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Professor Saravanamuth Vigneswaran

Director/Distinguished Professor, School of Civil and Environmental Engineering
Acting Head of School, Civil & Environmental Engineering, Faculty of Engineering & Information Technology
Director, CTWW - Centre for Technology in Water and Wastewater Treatment
Core Member, CTWW - Centre for Technology in Water and Wastewater Treatment
BSc (Hons) (OUSL), MSc (AIT), DSc (INP), Dr Ing (UM1)
Fellow, International Water Association
Member, International Water Academy
Chartered Engineer, Institution of Engineers, Australia
 
Phone
+61 2 9514 2641

Research Interests

Membrane technologies and hybrid systems for water reuse and desalination, high rate solid liquid separation technologies for package water treatment systems, advanced oxidation, photocatalysis, biofiltration for persistent organic removal, optimising treatment systems and their operation.

Can supervise: Yes

Books

Kandasamy, J. & Vigneswaran, S. 2008, Constructed wetlands.
This book covers an extensive range of issues related to constructed wetlands for treatment of stormwater and wastewater. Chapter One covers the functions and classifications of constructed wetlands, treatment processes of wetlands and a detailed description of microphytes. Chapter Two provides details of the design of wetlands and their construction. Chapter Three provides details of the important issue of operation and maintenance of constructed wetlands. Chapter Four highlights all the experience gained from managing a large and prominent urban wetland. Chapter Five outlines the importance of engaging the community when planning, designing and constructing wetlands. The book is useful for environmental professionals desiring a good appreciation of the concepts in constructed wetlands. This book is also a useful reference for graduate and post-graduate students of civil and environmental engineering, chemical engineering, environmental management or environmental science. © 2008 by Nova Science Publishers, Inc. All rights reserved.
Vigneswaran, S., Sundaravadivel, M., Kandasamy, J.K. & Chaudhary, D.S. 2007, Environmental Management - 2nd Edn., 2, Scitech Publications, Chennai.
Vigneswaran, S., Sundaravadivel, M. & Chaudhary, D.S. 2004, Environmental Management, Scitech Publications (India) Pvt Ltd, Chennai and Hydrabad, India.

Chapters

Chanan, A.P., Vigneswaran, S., Kandasamy, J.K. & Simmons, B. 2013, 'Wastewater Management Journey - From Indus Valley Civilisation to the Twenty-First Century' in Sharma, S.K. & Sanghi, R. (eds), Wastewater Reuse and Management, Springer Science+Business Media Dordrecht, Germany, pp. 3-18.
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Throughout the human existence on this planet, water and wastewater infrastructure never attracted as much public attention as it did during the second half of the nineteenth century. Following extensive debate on appropriate solutions for problems associated with hygiene and public health, options were chosen from several competing alternatives, while others foreclosed. Sociocultural impacts of these late nineteenth century decisions have lasted until the present day [1]. The shape of our cities and centralised approach embedded within sanitary engineers mindset today owe its existence to the options selected nearly 200 years ago. The current selection of water and wastewater management options, particularly in the developing world, has the opportunity to learn from 200 years of experience. It is critical that these lessons influence the design of future wastewater management systems because undoubtedly the decisions being made today will impact on the future generations. This chapter highlights the development of wastewater management through human evolution and settlement history.
Ngo, H., Guo, W. & Vigneswaran, S. 2012, 'Membrane Processes for Water Reclamation and Reuse' in Zhang, T.C., Surampalli, R.Y., Vigneswaran, S., Tyagi, R.D., Ong, S.L. & Kao, C.M. (eds), Membrane Technology and Environmental Applications, American Society of Civil Engineers, USA, pp. 239-275.
Water reclamation and reuse is being increasingly emphasized as a strategy for rational use of limited freshwater and as a means of safeguarding the deteriorating aquatic environment due to wastewater disposal. Membrane technology is playing a vital role in augment our water supplies and is essential for sustainable production of clean water. This chapter gives a comprehensive review of technological development train of wastewater treatment, as well as the detailed perfonnance of advanced membrance processes in municipal wastewater reclamation and reuse. The technological and economic feasibility of different membrane-based technologies compared to conventional treatment processes is also elucidated in this chapter.
Guo, W., Ngo, H. & Vigneswaran, S. 2012, 'Fouling Control of Membranes with Pretreatment' in Zhang, T.C., Surampalli, R.Y., Vigneswaran, S., Tyagi, R.D., Ong, S.L. & Kao, C.M. (eds), Membrane Technology and Environmental Applications, American Society of Civil Engineers, USA, pp. 533-580.
The impediment of the membrane technology is a fouling problem and consequently higher operating and membrane relacement cost. Pretreatment is very important for developing the best treatment process train to secure better membrane treatability and producing acceptable effluent qualities. This chapter addresses the state of the art pretreatment techniques and their application to low pressure (MF/UF) and high pressure (NF/RO) memrances in water and wastewater treatment as well as desalination. The impact of different pretreatment processes on membrane performance and membrane fouling control have been extensively reviewed.
Shon, H., Phuntsho, S., Vigneswaran, S., Kandasamy, J.K., Aryal, R. & Jegatheesan, V. 2012, 'Physical, Chemical, and Biological Characterization of Membrane Fouling' in Zhang, T.C., Surampalli, R.Y., Vigneswaran, S., Tyagi, R.D., Ong, S.L. & Kao, C.M. (eds), Membrane Technology and Environmental Applications, American Society of Civil Engineers, USA, pp. 457-497.
In this chapter, advanced characterization of membrane fouling as a diagnostic tool has been summarized to prevent membrane fouling. Physical, chemical and biological analyses as membrane autopsies are mainly utilized to better understand membrane foulant. The physical characteri zation gives structure, roughness, charge effect, strength and hydrophobicity of membrane fouling. The chemical methods provide qualitative and quantitative measurements of different inorganic and organic matter. The biological properties present the spatial biofilm distribution, structure of dominant microorgnisms and isolation and identification of microorganisms. In addition, detailed membrane foulant types are reviewed in terms of structure, roughness, hydrophobicity, charge effect, strength, calcium, magnesium, alluminum, iron, silicate, particle, functional group, biopolymer, humic acid, polysaccharide, structural composition, biofilm structure, microorganism and foulant interaction.
Guo, W., Ngo, H. & Vigneswaran, S. 2012, 'Enhancement of Membrane Processes with Attached Growth Media' in Zhang, T.C., Surampalli, R.Y., Vigneswaran, S., Tyagi, R.D., Ong, S.L. & Kao, C.M. (eds), Membrane Technology and Environmental Applications, American Society of Civil Engineers, USA, pp. 603-634.
The consumption of limited waste resources together with the need to comply with ever more stringent water quality standards, and the need to reuse water are the main impetus for the intensification of existing conventional water treatment processes. Moreover, current and impending legislation on wastewater treatment effluent has also led to the need for improved treatment processes capable of removing higher percentages of nutrients, suspended solids, bacteria, etc. (Kramne et al., 2005). During the last decades, the interest in the use of membrane technology has emerged in wastewater treatment as well as drinking water and process water production. This growth can be explained by a combination of (a) growing demand for water with high quality, (b) growing pressure to reuse wastewater, (b) better realibility and integrity of the membranes, (d) lower prices of membranes due to enhanced use, and (e) more stringent standards, e.g., in the drinking water industry (van de Bruggen et al., 2008). Therefore, membrane techniques (e.g., microfiltration (MF), ultrafiltration (DF), nanofiltration (NF) and reverse osmosis (RO)) in general and mebrance bioreactors (MBRs) in particular have been widely applied to wastewater reclamation and reuse for simultaneous organic and nutrient removal. Normally, there are two ways to begin water reuse: either retrofitting the current wastewater treatment plant (WWTP) facilities or constructing extra advanced processes after secondary treatment. Biological nutrients removal (BNR) processes modifying the current conventional WWTP is a typical example of retrofitting, while membrane filtration, carbon adsorption and ozonation are typically used for extra-installation the advanced treatment of secondary effluent (Baek and Chang, 2009). Especially, as eutrophication of the aquatic environment caused by nitrogen and phosphorus present in discharged effluent has become an unavoidable concern, the development of cost-effective and efficient BN...
Vigneswaran, S., Nguyen, T.V., Kandasamy, J., Ben Aim, R. & Visvanathan, C. 2012, 'Membrane processes for drinking water treatment' in Membrane Technology and Environmental Applications, ASCE Publications.
This volume provides in-depth technical information on the fundamentals, applications, and recent advances of membrane technology, including state-of-the-art reviews of current research, critical analysis of new processes and materials, and ...
Orem, Y., Messalem, R., Ben-David, E., Herzberg, M., Kushmaro, A., Ji, X., Di Profio, G., Curcio, E., Drioli, E., Laroche, J.F., Remize, P., Leparc, J., Vigneswaran, S., Chinu, K.J., Johir, M.H., Lee, J., Shon, H., Kandasamy, J.K., Ye, Y., Sim, L.N., Herulah, B., Chen, V., Fane, A.C., Tansakul, C., Laborie, S. & Cabassud, C. 2011, 'Evaluation and comparison of seawater and brackish water pre-treatment' in Drioli, E., Criscuofi, A. & Macedonio, F. (eds), Membrane-Based Desalination: An Integrated Approach (MEDINA), IWA Publishing, UK, pp. 33-70.
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The main objective of WP2 was to conduct a comprehensive evaluation on available pretreatment approaches for seawater, brackish water, and estuarinelbay water for membrane protection and recovery maximization. During the project promising results were obtained by UNlCAL and BGU on MBR as a means for reducing organic content from seawater as a step towards reducing fouling potentiaL It seems that the pretreatment in a MER system is effective at improving the water's quality (removal of TOC and EPS) for further process, but further economical and implemental examinations are necessary in order to adopt this treatment as an alternative pretreatment. The removal of particulate malter and organics from seawater by the use of biofiltration was investigated by UTS. Granular activated carbon (GAC) and anthracite were tested as a filter medium at two different velocities. The filtrate quality was evaluated by measuring the silt density index (SDI), modified fouling index (MFI) and turbidity removal. Both biofilters demonstrated similar behavior in terms of SDI and MFL In addition, fiber filter as pre-treatment of SWRO in terms ofMFI, SDI 10, pressure drop, turbidity and molecular weight distribution (MWD) was investigated with and without precoagulation. Submerged microfiltTation couplcd with physcio-chemical processes such as adsorption on powder activated carbon was investigated as well.
Moat, G., Simpson, B., Ghanem, P., Kandasamy, J.K. & Vigneswaran, S. 2008, 'Constructed Wetlands: Classification, Functions and Treatment' in Kandasamy, J. & Vigneswaran, S. (eds), Constructed Wetlands, Nova Science Publisher, Inc., New York, USA, pp. 1-26.
Constructed wetland technology utilises natural processes to treat wastewater and stormwater. Wetland technologies can provide cheap and effective wastewater treatment in both temperate and tropical climates, and is suitable for the adoption in both industrialised as well as developing nations. Constructed wetlands are being utilised for the removal of a range of pollutants and a broad range of wastewaters worldwide. This chapter provides a comprehensive review of the classifications, functions and treatment processes of constructed wetland.
Phuntsho, S., Shon, H.K., Vigneswaran, S. & Kandasamy, J. 2008, 'Wastewater Stablisation Ponds (WSP) For Wastewater Treatment' in Vigneswaran, S. (ed), Water and Wastewater Treatment Technologies, UNESCO & Encyclopedia of Life Support Systems (EOLSS).
Many industrialised countries have achieve d high levels of wastewater treatment technologies most of which are too mechanized and automated and beyond the affordability of the poor and developing nations. Technologies that are appropriate to the developing nations are required since two third of world's population live in developing countries. This review focuses mainly on those technologies appropriate to the developing countries. Appropriate technology should be affordable (capital cost), have low O&M cost (sustainability), effective in meeting the discharge standards, at least nuisance (public acceptability) and is environment-friendly. Many low cost technologies are being developed but the choice of the most appropriate technology depends on a proper evaluation of all the factors such as economic, political, social, availability, etc. Wastewater Stabilization Ponds (WSP) have been extensively used worldwide because of the simplicity in design and construction, the low capital and operating cost, are very reliable and are a sustainable technology. Constructed wetlands not only treat wastewater but have other functions such as habitats for animals and birds, recreational areas for the visitors, etc. Other low cost technologies appropriate to developing countries such as land treatments, filtration techniques, attach growth, aeration, baffled reactor and chemically enhance primary treatment are also discussed.
Shon, H.K., Phuntsho, S., Vigneswaran, S. & Kandasamy, J. 2008, 'Physico-Chemical Processes for Organic Removal from Wastewater Effluent' in Vigneswaran, S. (ed), Water and Wastewater Treatment Technologies, UNESCO & Encyclopedia of Life Support Systems (EOLSS).
This chapter covers physio-chemical processes including advanced oxidation processes for wastewater treatment. The approach used in this chapter is to first provide a brief introduction to each of the processes followed by a brief description of the process fundamentals in removing organic matter. The removal of effluent organic matter (EfOM) in terms of dissolved organic car bon (DOC), molecular weight distribution (MWD) for each process is then explained followed by removal of endocrine disrupting chemicals (EDCs) and pharmaceutical and personal care products (PPCPs) by each process.
Sundaravadivel, M. & Vigneswaran, S. 2007, 'Non-Conventional Sewerage' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 191-202.
Ngo, H., Vigneswaran, S. & Sundaravadivel, M. 2007, 'Advanced Treatment Technologies for Recycle/Reuse of Domestic Wastewater' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 77-98.
Vigneswaran, S. & Sundaravadivel, M. 2007, 'Wastewater Recycle, Reuse, and Reclamation' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 1-47.
Vigneswaran, S. & Sundaravadivel, M. 2007, 'Recycle and Reuse of Domestic Wastewater' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 48-76.
Illungkoo, K. & Vigneswaran, S. 2007, 'Water Reuse for Agriculture' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 137-165.
Visvanathan, C., Vigneswaran, S. & Jegatheesan, V. 2007, 'Industrial Waste Minimization' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 252-269.
Jegatheesan, V., Ben Aim, R.M. & Vigneswaran, S. 2007, 'Raw Materials and Process Chemical Recovery in Industrial Wastewater Pollution Control' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 270-280.
Sundaravadivel, M., Vigneswaran, S. & Visvanathan, C. 2007, 'Waste Minimization in Metal Finishing Industries' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 319-339.
Vigneswaran, S., Ngo, H., Visvanathan, C. & Sundaravadivel, M. 2007, 'Quantity and Quality of Drinking Water Supplies' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 24-36.
Vigneswaran, S., Ngo, H., Visvanathan, C. & Sundaravadivel, M. 2007, 'Conventional Water Treatment Technologies' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 37-56.
Vigneswaran, S. & Sundaravadivel, M. 2007, 'Traditional and Household Water Purification Methods of Rural Communities in Developing Countries' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 85-97.
Viraraghavan, T., Sundaravadivel, M. & Vigneswaran, S. 2007, 'Small Community and Rural Sanitation Systems' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 113-145.
Viraraghavan, T., Krishnamurthy, S. & Vigneswaran, S. 2007, 'Public Health Aspects of On-site Sanitation' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 203-229.
Sundaravadivel, M. & Vigneswaran, S. 2007, 'Constructed Wetlands for Wastewater Treatment' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 166-186.
Jegatheesan, V., Ben Aim, R.M. & Vigneswaran, S. 2007, 'By-product Recovery in Industrial Wastewater Pollution Control' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 281-289.
Vigneswaran, S. & Sundaravadivel, M. 2007, 'Small and Rural Community Water Supply' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 1-23.
Sundaravadivel, M. & Vigneswaran, S. 2007, 'Rural Water Supply Systems' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 57-84.
Vigneswaran, S., Visvanathan, C. & Sundaravadivel, M. 2007, 'Treatment Options for Removal of Specific Impurities from Water' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 98-112.
Vigneswaran, S. & Sundaravadivel, M. 2007, 'On-site Sanitation Technologies for Cold and Temprate Climates' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 179-190.
Jegatheesan, V., Ben Aim, R.M. & Vigneswaran, S. 2007, 'Process/Technology Modifications in Water Pollution Control' in Vigneswaran, S.V. (ed), Wastewater Recycle, Reuse, and Reclamation, Eolss Publishers Co., Ltd.,, UK, pp. 290-300.
Vigneswaran, S., Ngo, H., Chaudhary, D.S. & Hung, Y. 2005, 'Physicochemical Treatment Processes for Water Reuse' in Wang, L.K., Hung, Y.T. & Shammas, N.K. (eds), Physicochemical Treatment Processes, Humana Press, Totowa, New Jersey, USA, Totowa, New Jersey, USA, pp. 635-676.
Vigneswaran, S. & Ngo, H. 2000, 'Technologies for domestic wastewater treatment and reuse' in Goosen, F.A. & Shayya, W.H. (eds), Water Management, Purification & Conservation in Arid Climates, Technomic Publishing Co., Inc., USA, pp. 123-151.

Conferences

Shanmuganathan, S., Johir, M.A.H., Listowski, A., Vigneswaran, S. & Kandasamy, J. 2015, 'Sustainable Processes for Treatment of Waste Water Reverse Osmosis Concentrate to achieve Zero Waste Discharge: A Detailed Study in Water Reclamation Plant', Waste Management for Resource Utilisation (Procedia Environmental Sciences), International Conference on Solid Waste Management, 5IconSWM 2015, Elsevier, Bengaluru, India, pp. 930-937.
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Water reclamation systems based on dense membrane treatment such as reverse osmosis (RO) are being progressively applied to meet water quantity and quality requirements for a range of urban and environmental applications. The RO concentrate usually represents 25% of the feed water flow and contains the organic and inorganic contaminants at higher concentrations. The amount of RO concentrate waste water requiring disposal must be as minimal as possible (near zero-discharge); the recovery of high quality water should be as high as possible. Management issues related to proper treatment and disposal of RO concentrate are an important aspect of sustainable water reclamation practice. The RO concentrate is a significant component of water treatment process and poorly managed treatment and disposal of RO concentrate causes significant consequences. Even in a small to medium size water reclamation plant in Sydney, 2000 kL of water is treated by RO and around 300 kL of RO concentrate is produced daily. This RO concentrate consists of a high level of organics (25-30mg/L of DOC which is mainly refractory organics) and inorganic salts (Cl = 400-650mg/L, Na+ = 400-500mg/L, Ca2+ = 93-200mg/L, K+ = 63-100mg/L). The RO concentrate waste disposal cost can be minimized and made valuable by reclaiming the RO concentrate with the aim of producing salts from the solutes and recycling the water to the treatment system. Technologies for recovery of high salt concentration from the RO concentrate such as forward osmosis (FO) and membrane distillation (MD) are either energy intensive or not developed in large scale. In this study, we highlight a sustainable membrane adsorption hybrid system in treating this RO concentrate.
Ben-Aim, R., Chinu, K.J., Johir, M.H., Vigneswaran, S. & Kandasamy, J.K. 2010, 'New sources of water: Optimizing the use of membranes for their production', IWA Regional Conference and Exhibition on Membrane Technology & Water Reuse, IWA, Istabul-Turkey, pp. 1025-1027.
In many parts of the world water stress is predicted to occur in a near future. Membrane technology can help address this issue but the use of membranes has to be optimized for obtaining suitable water quality in an acceptable economic and ecological manner. Eventually the use of membranes could introduce a shift from a centralized water management to a decentralized one. The three potential new sources of water are treated wastewater or wastewater reuse, seawater and brackish water, rainwater including stormwater.
Nguyen, T.V., Rahman, A., Vigneswaran, S., Ngo, H.H., Chang, J.S. & Chang, C.Y. 2010, 'The uptake of arsenite by coprecipitation and adsorption on iron oxide coated sponge', Arsenic in Geosphere and Human Diseases, As 2010 - 3rd International Congress: Arsenic in the Environment, pp. 450-452.
Nguyen, V., Tran, T.T., Pham, T.L., Vigneswaran, S., Ngo, H., Nguyen, H. & Nguyen, D.T. 2009, 'Use of a Novel Ferrous-Ferric oxide Material from Waste of Iron Ore Mining for Arsenic Removal', The 3rd IWA-ASPIRE Conference & Exhibition (IWA-ASPIRE 2009), The 3rd IWA-ASPIRE Conference & Exhibition (IWA-ASPIRE 2009), IWA, Taiwan, pp. 1-9.
Savitha, R., Vigneswaran, S., Suresh, S. & Sundararajan, N. 2009, 'Adaptive beamforming using complex-valued radial basis function neural networks', IEEE Region 10 Annual International Conference, Proceedings/TENCON.
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Beamforming is an array signal processing problem of forming a beam pattern of an array of sensors. In doing so, beams are directed to the desired direction (beam-pointing) and the nulls are directed to interference direction (null-steering). In this paper, the performance of beamforming using the Fully Complex-valued RBF network (FC-RBF) with the fully complexvalued activation function is compared with the performance of the existing complex-valued RBF neural networks. It was observed that the FC-RBF network performed better than the other complex-valued RBF networks in suppressing the nulls and steering beams, as desired. The learning speed of the FC-RBF network was also faster than the Complex-valued Radial Basis Function network. Comparison of these performances with the optimum Matrix method showed that the beampattern of the FCRBF beamformer was closer to the beampattern of the matrix method. © 2009 IEEE.
Nguyen, V., Vigneswaran, S. & Ngo, H. 2008, 'A Novel Iron Oxide Coated Sponge Adsorption System To Remove Arsenic From Drinking Water', Proceedings of the World Water Congress and Exhibition 2008, IWA World Water Congress, International Water Association (IWA), Vienna, Austrlia, pp. 1-8.
Millions of people worldwide are at risk from the presence of arsenic in groundwater. There is a global need to develop appropriate technologies to remove arsenic from water for household and community water supply systems. In this study, a new material namely iron oxide coated sponge (IOCSp) was developed and used to remove As. It was found that IOCSp has a high capacity in removing both As (V) and As (III). The adsorption capacity of IOCSp was up to 4.6 mg As/g IOCSp, higher than a number of other materials. A filter packed even with very small amount of 25 g IOCSp maintained a consistent arsenic removal efficiency of 95% from synthetic water containing arsenic concentration of as high as 1,000μg/L. This produced a throughput volume of 153 and 178L of water containing As(III) and As(V) respectively before any need for regeneration or disposal of IOCSp. It was found to provide comparable results with advanced technologies such as nanofiltration system with in line addition of nano zero valent iron. In addition, the initial results also showed that the exhausted IOCSp can safely be disposed of through the solidification/stabilization technique.
Ho, D.P., Vigneswaran, S., Ngo, H., Shon, H. & Kandasamy, J.K. 2008, 'Adsorption and Photocatalysis Kinetics of UV Light Responsive and Visible Light Responsive Titanium Dioxide in Wastewater Treatment', Proceedings of the IWA World Water Congress and Exhibition 2008, IWA World Water Congress, International Water Association (IWA), Vienna, Austria, pp. 1-8.
The possible use of photocatalysis with TiO2 in wastewater treatment has been the focus of numerous studies in recent years. In this study, the adsorption and photocatalytic oxidation of organic compounds by UV light responsive titanium dioxide (P25) and visible light responsive titanium dioxide (Vis-TiO2) were investigated. Firstly, the adsorption behavior of the two photocatalysts was examined by the adsorption isotherm and kinetics experiments. The photocatalytic reactivity of the catalysts was then compared at different operating conditions. The results indicate that Freundlich model well described the adsorption capacity of both materials. The photocatalytic kinetics showed that the highest removal of NOM was achieved at an optimum concentration of 1.0 g/L of both photocatalysts. In case of P25, one-hour irradiation of UV light at the intensity of 184.64 mW/cm2 resulted in approximately 57% of TOC removal. It was observed that visible light photoexciting Vis- TiO2 required a longer irradiation time of 2 days to remove 65% of organic matters.
Mohammed Abdul, J., Areerachakul, N., Shon, H., Vigneswaran, S. & Kandasamy, J.K. 2008, 'Biofilter and Photo-Catalytic Treatment Processes of Groundwater Contaminated with Landfill Leachate', Proceedings of the IWA World Water Congress and Exhibition 2008, IWA World Water Congress, International Water Association (IWA), Vienna, Austria, pp. 1-8.
Landfill leachate is produced when rainwater infiltrates into the landfill and permeates through the decomposing waste within the landfill leaching out with it contaminants and pollutants. Untreated leachates can permeate ground water or mix with surface waters and contribute to the pollution of soil, ground water, and surface water. In this study, the processes such as GAC bio-filtration and photocatalysis and bio-filter were evaluated in treating synthetic landfill leachate. The Total organic carbon (TOC) removal efficiency (of landfill leachate) was evaluated by sequential adsorption/bio-sorption (on GAC) and compared with photocatalysis. GAC bio-filtration led to a consistent TOC removal even after a long period of operation without the need to regenerate the activated carbon. Even after 35 days of continuous running, the TOC of the effluent from the GAC bio-filter was approximately 60% of the influent quality (i.e. 40% removal). Biofiltration with a post treatment of advanced oxidation with Fenton reagent led to more 70% of removal of TOC. Also, the treatment of biofilter redcued significantly the concentration of Fenton reagent. On the other hand photocatalysis with TiO2 as a separate treatment led to only 40% TOC reduction.
Listowski, A., Ngo, H., Guo, W., Vigneswaran, S. & Palmer, C.G. 2008, 'Assessment Framework of Urban Water Reuse Based on a Novel Integrated Water Cycle Concept', Proceedings of the IWA World Water Congress and Exhibition 2008, IWA World Water Congress, International Water Association (IWA), Vienna, Austria, pp. 1-8.
To achieve sustainability of the water reclamation and urban reuse technologies, it would be necessary to develop and apply comprehensive assessment methodology and processes that would consider critical elements of urban water cycle, sustainability criteria and appropriate performance assessment standards as an integrated framework. When trying to study the rationale behind the urban water reuse approaches from social, economic, technical and ecological point of view, the outcomes are often lacking cohesion and appropriate balance. The assessment methods are further complicated by the lack of consistency, specific and accurate information and methodologies, which ultimately impair the process. Taking into consideration complexity and uniqueness of the integrated water cycle concept, this paper introduces to a novel assessment framework. This enables to identify suitable assessment process consisting of logical steps and including relevant objectives, principles from which a broad selection of criteria s and performance indicators would be derived. The final step in the process would be focused on validation of the quantitative analysis and model preparation. A considerable effort would also be necessary to establish baseline indicators of sustainability and operational tools to evaluate performance of the urban water systems.
Kandasamy, J.K. & Vigneswaran, S. 2006, 'Constructed Wetlands for Wastewater and Stormwater Management', Current Issues on Wetland Conservation in Asia: In View of the Upcoming COP10, International Symposium on Regional Wetlands Issues In Asia, Daewoong, Bugok, South Korea, pp. 60-70.
Ngo, H., Guo, W., Vigneswaran, S. & Xing, W. 2007, 'Potential of submerged membrane bioreactors for wastewater treatment and reuse', Proceedings of International Conference on Cleaner Technologies and Environmental Management, International Conference on Cleaner Technologies and Environmental Management, Allied Publishers Pvt. Ltd., India, pp. 800-805.
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The use of membrane bioreaetor (MBR) has been an increasing issue in replacing the conventional water and wastewater treatment processes to produce high quality treated water. In MBR systems design,the submergedmembranebioreactor (SMBR)can assist in significantlyreducingpower consumptionas the entire treatment activity (such as adsorption/biodegradation,liquid-solid separation, andsludgeaccumulationandwithdrawal)canbe carriedout in a singleunit. In this study, the performance of conventional 5MBR and non-eonventional submerged membrane adsorption bioreactor (SMABR) was evaluated in terms of organic and bacterial removal efficiencies,biomassgrowthvia specificoxygen uptake rate (SOUR) and mixed liquor suspendedsolids (MLSS), and membrane fouling through the development of transmembrane pressure (TMP) and sustainableflux.Theresults indicatethat both ofSMBRand5MBARproducedvery high effiuentquality. However,SMABRappeared to have a better performance as it achieved nearly 100%ofTOC andCOD removalswhile having lowerTMPdevelopment and higher SOUR,The MLSSkept constant (around 10 gIL) after 10 days operation in 5MBAR compared to about 4 gILofMLSS in 5MBR case. In order 10 enhancethe sustainableflux, an idea ofadding a predeterminedamountof spongeinto 5MBRreactor was proposedand tested, The results show that 10% of volume fraction of sponge addition could increase 2 folds of sustainablefluxofSMBRsystemat an air flow rate of9 L/min.
Kim, S., Nguyen, V., Vigneswaran, S. & Ngo, H. 2007, 'Adsorption Equilibrium, Kinetics and Thermodynamics of Iron-coated Sponge (IOCSp) for Removal of As (III)', Proceedings of International Conference on Cleaner Technologies and Environmental Management (ICCTEM 200), International Conference on Cleaner Technologies and Environmental Management, Allied Publishers Pvt. Ltd., India, pp. 44-50.
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Sundravadivivel, M., Kandasamy, J.K. & Vigneswaran, S. 2006, 'Policy and Design Issues in Rainwater Harvesting: Case Study in South Asia', Rainwater Harvesting and Management Vision: Multipurpose and Proactive - Workshop of IWA World Water Congress, IWA World Water Congress, IWA, Beijing, China, pp. 69-78.
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Visvanathan, C., Kandasamy, J.K. & Vigneswaran, S. 2006, 'Rainwater Collection and Storage in Thailand: Design, Practices and Operation', Rainwater Harvesting and Management Vision: Multipurpose and Proactive - Wortkshop of the IWA World Water Congress, IWA World Water Congress, IWA, Beijing, China, pp. 69-78.
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Shon, H., Vigneswaran, S., Kim, J., Ngo, H. & Park, N. 2004, 'Comparison of Nanofiltration with Flocculation-Microfiltration-Photocatalysis Hybrid System in Dissolved Organic Matter Removal', 9th World Filtration Congress, World Filtration Congress, The American Filtration and Separation Society, New Orleans, Louisiana, USA, pp. 1-19.
Shon, H., Vigneswaran, S., Kim, I.S., Cho, J. & Ngo, H. 2004, 'Characterization of Different Treatments With Biologically Treated Sewage Effluent and Synthetic Wastewater', Enviro 04 Convention & Exhibition, Enviro 04, Enviroaust Convention Limited, Darling Harbour, Australia, pp. 1-10.
Guo, W., Vigneswaran, S. & Ngo, H. 2004, 'A Rational Approach In Controlling Membrane Fouling Problems: Pretreatments to a submerged Hollow Fibre Membrane System', Water Environment - Membrane Technology Proceedings, IWA Specialty Conference, Water Environment-Membrane Technology, IWA, Seoul, Korea, pp. 517-524.
Guo, W., Vigneswaran, S., Ngo, H. & Ben Aim, R.M. 2004, 'Performance of a Submerged Membrane Adsorption Hybrid System (SMAHS) in Wastewater Treatment for Reuse', 4th World Water congress: innovations in Drinking Water Treatment, IWA World Water Congress, IWA, Marrakech, Morocco, pp. 1-8.
Nguyen, V., Vigneswaran, S., Ngo, H., Pokhrel, D. & Viraraghavan, T. 2004, 'Arsenic Removal by Iron Coated Sponge in Drinking Water Treatment', The 2nd International Symposium on Southeast Asian Water Environment, The Second International Symposium on Southeast Asian Water Environment, The University of Tokyo, Hanoi, Vietnam, pp. 214-221.
Chaudhary, D.S., Guo, W., Vigneswaran, S., Ngo, H. & Vigneswaran, B. 2003, 'Submerged Microfiltration: An Energy Efficient Process for Water Reuse', AWA Oz Water Convention and Conference, Australian Water Association Convention - Ozwater, AWA, Perth, Australia, pp. 1-9.
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Guo, W., Vigneswaran, S., Ngo, H. & Ben Aim, R.M. 2003, 'Evaluating the Efficiency of Pretreatment to Microfiltration: Using Critical Flux As a Performance Indicator', IMSTEC 2003, International Membrance Science and Technology Conference, AWA-UNESCO Membrane Centre, Sydney, Australia, pp. 1-6.
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Kim, D., Shon, H., Vigneswaran, S. & Cho, J. 2003, 'Evaluating Interactions Between NOM Molecules and Various Membranes with Flow Field -Flow Fractionation', IMSTEC 2003, Fifth International Membrane Science and Technology Conference, AWA-UNESCO Membrane Centre, Sydney, Australia, pp. 1-6.
Shon, H., Vigneswaran, S., Ngo, H. & Ben Aim, R.M. 2003, 'Low Pressure Nanofiltration with Adsorption As Pretreatment In Tertiary Wastewater Treatment for Reuse', IMSTEC 2003, International Membrane Science and Technology Conference, AWA-UNESCO Membrane Centre, Sydney, Australia, pp. 1-7.
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Shon, H., Vigneswaran, S., Ngo, H. & Kim, I.S. 2003, 'Effect of high rate Pre-Treatment on Nanofiltration Systems in Wastewater Reuse', ASIAN WaterQual 2003, IWA Asia-Pacific Regional Conference, IWA-Regional Publication, Bangkok, Thailand, pp. 1-9.
Guo, W., Vigneswaran, S., Ngo, H., Shon, H. & Shimohoki, S. 2003, 'Improving the Performance of a Crossflow Microfiltration in Tertiary Wastewater Treatment and Reuse By Specific Pre-Treatment Processes', ASIAN WaterQual 2003, IWA Asia-Pacific Regional Conference, IWA-Regional Publication, Bangkok, Thailand, pp. 1-8.
Shon, H., Vigneswaran, S., Ngo, H., Kim, D., Park, N.E., Jang, N.J. & Kim, I.S. 2003, 'Characterisation of Effluent Organic Matter (EFOM)Of Fouled Nanofilter (NF) Membranes', IMSTEC2003, Fifth International Membrane Science and Technology Conference, AWA-UNESCO Membrane Centre, Sydney, Australia, pp. 1-6.
Maheswaran, S.M., Yadav, N.N., Shutthanandan, V., Thevuthasan, S., Hart, T.R., Ngo, H. & Vigneswaran, S. 2003, 'Evaluating the use of induced X-ray emission (PIXE) technique in quantifying the arsenic in an adsorbent', ASIAN WaterQual2003, IWA Asia-Pacific Regional Conference, IWA-regional publication, Bangkok, Thailand, pp. 1-8.
Thiruvenkatachari, R., Ngo, H.H., Hagare, P., Vigneswaran, S. & Ben Aim, R. 2002, 'Flocculation-cross-flow microfiltration hybrid system for natural organic matter (NOM) removal using hematite as a flocculent', DESALINATION, pp. 83-88.
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Ngo, H.H., Vigneswaran, S., Hu, J.Y., Thirunavukkarasu, O. & Viraraghavan, T. 2002, 'A comparison of conventional and non-conventional treatment technologies on arsenic removal from water', Water Science and Technology: Water Supply, pp. 119-125.
In this study, four treatment methods were used to remove arsenic from water, namely: (i) chemical precipitation, (ii) arsenic adsorption onto iron-oxide-coated sand, (iii) high-rate saturated floating-medium flocculator/filter and (iv) membrane hybrid system (adsorption-microfiltration). The results indicated that more than 90% of total arsenic was removed by using FeCl3 (40 mg/L) as coagulant. The removal efficiency was 10% lower when polysilicato-iron (PSI, 2.5 mg/L) was used as a flocculant. The results of both the batch and column adsorption studies showed that iron-oxide-coated sand can effectively be used to achieve very high levels of arsenic removal (less than 5 m/L as As in drinking water). Arsenic was removed up to 78% from the packed polystyrene beads filter with in-line FeCl3 addition at a high loading rate of 30 m3/m2.h. When powder activated carbon (PAC) was used in the membrane hybrid system, 87% removal of arsenic was achieved. A mixing time of 2.7 min with the mixing intensity of 87.8 s-1 were used. A very high filtration (permeate flux of 760 L/m2.h) was observed with a membrane of pore size of 0.2 m.
Bidkar, A., Vigneswaran, S., Milne-Home, W.A., Ngo, H. & Moon, H. 2000, 'Adsorption of Metsulfuron-Methyl on Granular Activated Carbon', Proceedings of the 4th International Symposium on Environmental Geotechnology and Global Sustainable Development, CEEST, Boston (Danvers), Massachusetts, USA, pp. 1079-1086.
Jegatheesan, V., Ngo, H. & Vigneswaran, S. 2000, 'High rate filtration using buoyant medium: experiments and mathematical models', Critical Technologies to the World in 21st century: Pollution Control and Reclamation in process industries, International Water Association, Beijing, China, pp. 0-0.
Sundaravadivel, M. & Vigneswaran, S. 2000, 'Waste collection and treatment technology for semi-urban areas of India: A case study', First Water Congress of the International Water Association, International Water Association, Paris, France, pp. 0-0.
Vigneswaran, S., Kwon, D.Y., Ngo, H.H. & Hu, J.Y. 2000, 'Improvement of microfiltration performance in water treatment: Is critical flux a viable solution?', Water Science and Technology, pp. 309-315.
In this study, three definitions for critical flux were introduced based on the crossflow microfiltration (CFMF) experiments conducted under an operational mode of constant permeate flux. The critical flux based on material balance was calculated from the rate of particles deposition. The highest permeate flux results in no particle deposition being taken at the critical flux. The second definition was based on the increase in transmembrane pressure (TMP). The critical flux based on the TMP increase is the flux below which the membrane fouling does not occur. The third definition was based on the direct observation of particles deposition through microscope. Detailed experiments were conducted with synthetic suspension of different sizes of latex particles. Long term experiments conducted with polydispersed kaolin clay suspension indicated that the critical flux based on material balance concept is more realistic in field conditions.
Ngo, H.H., Vigneswaran, S., Kim, S.H., Bidkar, A. & Moon, H. 2000, 'Microfiltration-adsorption hybrid system in organics removal from water', Water Science and Technology, pp. 51-57.
A series of experiments was conducted with a Millipore flat plate microfiltration module modified to incorporate in-line powdered activated carbon (PAC) addition In-line PAC was mixed continuously through a spiral mixing device for a predetermined time prior entering a membrane unit. The results showed that this system is excellent in removing fulvic acid (FA). This system provides to sufficient contact time for PAC to adsorb organics compared to the system with in-line adsorbent addition. More than 85% of FA was removed from water containing 8 mg/l of FA. To achieve this following conditions were used:.(i) a velocity gradient G (mixing intensity) of 160.4 s-1; (ii) a hydraulic residence time (mixing time) of 4 minutes; (iii) a PAC dose of 260 mg/l; and (iv) membrane pore size of 0.22 m. In case of low FA concentration (e.g. 1.2 mg/l) in water, the removal efficiency was almost 100%. The removal efficiency also increased with the increase of mixing intensity and mixing timer. The permeate flux slightly improved when a membrane of pore size 0.22 m was used with shorter hydraulic residence time and lower PAC concentration. This paper presents a mathematical model developed based on surface diffusion. The model successfully predicted the performance of this hybrid system.
Prasanthi, H., Vigneswaran, S., Waite, T.D. & Ben Aim, R. 1994, 'Filtration of submicron particles: Effect of ionic strength and organic substances', Water Science and Technology, pp. 149-158.
Hematite (-Fe2O3) suspension was used in this study to investigate the effects of aggregate size and solution chemical characteristics on particle removal and headless development in a deep bed filter. When electrolyte (KCl) concentration in the suspension was increased from 0-80 mM, the size of hematite aggregates in suspension increased from 85 to 990 nM but had no significant effect on zeta potential. It was found that at low KCl concentrations (0-10 mM), the initial removal is governed by surface chemical properties while at higher concentrations (40-80 mM), the effect of particle size (steric effect) predominates. The transient stage filter performance was found to be controlled by the favourable chemical conditions prevailing in the filtration system rather than the size of the particles. Studies of the effect of a natural organic material (fulvic acid) on particle removal indicated that fulvic acid at low concentrations (less than 0.75 mg/L) enhanced particle aggregation and improved filtration efficiency. At concentrations higher than 2 mg/L, it was found to increase the stability of particles thus affecting filtration efficiency.
Vigneswaran, S., Manandhar, U.K., Janssens, J.G. & Ben Aim, R. 1991, 'Mathematical modelling of the effect of size distribution of suspended particles in deep-bed filtration - Experimental testing', Water Supply.
A mathematical model for granular bed filtration incorporating the influent particle size distribution was tested using extensive experimental results obtained from laboratory-scale filter experiments with sikron particles. This study gives an approach which reduces the nos. of model coefficients to be estimated by expressing these as functions of particle diameter. The predicted result fits reasonably well for the case of finer particles than the bigger ones, specially at the ripening stage.
Vigneswaran, S. & Setiadi, T. 1986, 'SPIRAL FLOCCULATOR: MATHEMATICAL MODELLING AND EXPERIMENTS.'.
Spiral flocculator has been claimed to be a good method for continuous assessment of flocculation in water treatment plant, and overcome most of the limitations experienced in jar test procedure. This paper deals with the mathematical modelling of spiral flocculator performance. The effluent turbidity, and temporal variation of floc size and floc density were related to the velocity gradient and influent concentrations. These formulations were then verified with the experimental results obtained from the laboratory-scale spiral flocculator experimental study. The experimental study also revealed that the spiral flocculator has a better effective energy dissipation compared to that of jar test although the size of flocs in spiral flocculation seems to be overestimated relative to the real flocculator.
Vigneswaran, S., Naw, M.S., Jeyaseelan, S. & Rabbani, W.I. 1983, 'COMPARISON OF MOBILE AND FIXED BED FILTER PERFORMANCE: RADIAL AND CONVENTIONAL VERTICAL DOWNWARDS FLOW.', American Institute of Chemical Engineers, National Meeting.
Vigneswaran, S. 1983, 'IMPORTANCE OF SIMULATION IN DEEP BED FILTRATION.', pp. 331-334.
In deep bed filtration, the removal of particles in the suspension is complex and depends on numerous filtration parameters. The mathematical models describing deep bed filtration involve several filtration coefficients which are characteristic of the particular suspension to be filtered and the type of filter media used. If these coefficients are evaluated from a limited number of filter experiments, filtration performance can be simulated for any operating conditions which would be helpful in designing the filter in a rational manner. This paper presents the simulation of dual media and radial filters from a limited number of conventional (vertical down flow) filter experiments. The simulated and experimental results are found to be comparable which indicates the usefulness of simulation in deep bed filtration.
Vigneswaran, S., Rabbani, W.I. & Naw, M.S. 1983, 'IMPORTANCE OF LABORATORY SCALE STUDY FOR THE DESIGN OF MOBILE-BED FILTER.', pp. 169-178.
Filters with mobile-bed arrangement eliminate the problem of back washing and use the entire filter bed in efficient filtration action. The optimum values of operational parameters of mobile-bed filter (sand-recycling rate, sludge-withdrawal rate, filter media specifications, filtration rate) can be evaluated from laboratory-scale experiments with the particular water to be treated. These values can be used to design a plant-scale mobile-bed filter in a rational manner.
Vigneswaran, S. 1982, 'The design of filters with low cost materials for small communities', Water and Waste Engineering in Asia: Proceedings of the 8th WEDC Conference, pp. 51-54.

Journal articles

Naidu, G., Shim, W.G., Jeong, S., Choi, Y.K., Ghaffour, N. & Vigneswaran, S. 2017, 'Transport phenomena and fouling in vacuum enhanced direct contact membrane distillation: Experimental and modelling', Separation and Purification Technology, vol. 172, pp. 285-295.
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© 2016 Elsevier B.V.The application of vacuum to direct contact membrane distillation (vacuum enhanced direct contact membrane distillation, V-DCMD) removed condensable gasses and reduced partial pressure in the membrane pores, achieving 37.6% higher flux than DCMD at the same feed temperature. Transfer mechanism and temperature distribution profile in V-DCMD were studied. The empirical flux decline (EFD) model represented fouling profiles of V-DCMD. In a continuous V-DCMD operation with moderate temperature (55 °C) and permeate pressure (300 mbar) for treating wastewater ROC, a flux of 16.0 ± 0.3 L/m2 h and high quality distillate were achieved with water flushing, showing the suitability of V-DCMD for ROC treatment.
Shanmuganathan, S., Loganathan, P., Kazner, C., Johir, M.A.H. & Vigneswaran, S. 2017, 'Submerged membrane filtration adsorption hybrid system for the removal of organic micropollutants from a water reclamation plant reverse osmosis concentrate', DESALINATION, vol. 401, pp. 134-141.
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Vu, T.M., Trinh, V.T., Doan, D.P., Van, H.T., Nguyen, T.V., Vigneswaran, S. & Ngo, H.H. 2017, 'Removing ammonium from water using modified corncob-biochar', Science of the Total Environment, vol. 579, pp. 612-619.
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Ammonium pollution in groundwater and surface water is of major concern in many parts of the world due to the danger it poses to the environment and people's health. This study focuses on the development of a low cost adsorbent, specifically a modified biochar prepared from corncob. Evaluated here is the efficiency of this new material for removing ammonium from synthetic water (ammonium concentration from 10 to 100 mg/L). The characteristics of the modified biochar were determined by Brunauer-Emmett-Teller (BET) test, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). It was found that ammonium adsorption on modified biochar strongly depended on pH. Adsorption kinetics of NH4+-N using modified biochar followed the pseudo-second order kinetic model. Both Langmuir and Sips adsorption isotherm models could simulate well the adsorption behavior of ammonium on modificated biochar. The highest adsorption capacity of 22.6 mg NH4+-N/g modified biochar was obtained when the biochar was modified by soaking it in HNO3 6 M and NaOH 0.3 M for 8 h and 24 h, respectively. The high adsorption capacity of the modified biochar suggested that it is a promising adsorbent for NH4+-N remediation from water
Vu, T.M., Trinh, V.T., Doan, D.P., Van, H.T., Nguyen, T.V., Vigneswaran, S. & Ngo, H.H. 2017, 'Removing ammonium from water using modified corncob-biochar', Science of the Total Environment, vol. 579, pp. 612-619.
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Ammonium pollution in groundwater and surface water is of major concern in many parts of the world due to the danger it poses to the environment and people's health. This study focuses on the development of a low cost adsorbent, specifically a modified biochar prepared from corncob. Evaluated here is the efficiency of this new material for removing ammonium from synthetic water (ammonium concentration from 10 to 100 mg/L). The characteristics of the modified biochar were determined by Brunauer-Emmett-Teller (BET) test, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). It was found that ammonium adsorption on modified biochar strongly depended on pH. Adsorption kinetics of NH4+-N using modified biochar followed the pseudo-second order kinetic model. Both Langmuir and Sips adsorption isotherm models could simulate well the adsorption behavior of ammonium on modificated biochar. The highest adsorption capacity of 22.6 mg NH4+-N/g modified biochar was obtained when the biochar was modified by soaking it in HNO3 6 M and NaOH 0.3 M for 8 h and 24 h, respectively. The high adsorption capacity of the modified biochar suggested that it is a promising adsorbent for NH4+-N remediation from water
Sounthararajah, D.P., Loganathan, P., Kandasamy, J. & Vigneswaran, S. 2017, 'Removing heavy metals using permeable pavement system with a titanate nano-fibrous adsorbent column as a post treatment', Chemosphere, vol. 168, pp. 467-473.
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&copy; 2016 Elsevier LtdPermeable pavement systems (PPS) are a widely-used treatment measure in sustainable stormwater management and groundwater recharge. However, PPS are not very efficient in removing heavy metals from stormwater. A pilot scale study using zeolite or basalt as bed material in PPS removed 41&#8211;72%, 67&#8211;74%, 38&#8211;43%, 61&#8211;72%, 63&#8211;73% of Cd, Cu, Ni, Pb, and Zn, respectively, from synthetic stormwater (pH 6.5; Cd, Cu, Ni, Pb, and Zn concentrations of 0.04, 0.6, 0.06, 1.0, and 2.0 mg L1, respectively) over a period of 80 h. The total volume of stormwater that passed through the PPS was equivalent to runoff in 10 years of rainfall in Sydney, Australia. The concentrations of metals in the PPS effluent failed fresh and marine water quality trigger values recommended in the Australian and New Zealand guidelines. An addition of a post-treatment of a horizontal filter column containing a titanate nano-fibrous (TNF) material with a weight < 1% of zeolite weight and mixed in with granular activated carbon (GAC) at a GAC:TNF weight ratio of 25:1 removed 77% of Ni and 99&#8211;100% of all the other metals. The effluent easily met the required standards of marine waters and just met those concerning fresh waters. Batch adsorption data from solutions of metals mixtures fitted the Langmuir model with adsorption capacities in the following order, TNF zeolite > basalt; Pb > Cu > Cd, Ni, Zn.
Naidu, G., Jeong, S., Choi, Y. & Vigneswaran, S. 2017, 'Membrane distillation for wastewater reverse osmosis concentrate treatment with water reuse potential', Journal of Membrane Science, vol. 524, pp. 565-575.
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&copy; 2016 Elsevier B.V.Membrane distillation (MD) was evaluated as a treatment option of wastewater reverse osmosis concentrate (WWROC) discharged from wastewater reclamation plants (WRPs). A direct contact MD (DCMD), at obtaining 85% water recovery of WWROC showed only 13&#8211;15% flux decline and produced good quality permeate (10&#8211;15&nbsp;&micro;S/cm, 99% ion rejection) at moderate feed temperature of 55&nbsp;&deg;C. Prevalent calcium carbonate (CaCO3) deposition on the MD membrane occurred in treating WWROC at elevated concentrations. The combination of low salinity and loose CaCO3 adhesion on the membrane did not significantly contribute to DCMD flux decline. Meanwhile, high organic content in WWROC (58&#8211;60&nbsp;mg/L) resulted in a significant membrane hydrophobicity reduction (70% lower water contact angle than virgin membrane) attributed to low molecular weight organic adhesion onto the MD membrane. Granular activated carbon (GAC) pretreatment helped in reducing organic contents of WWROC by 46&#8211;50%, and adsorbed a range of hydrophobic and hydrophilic micropollutants. This ensured high quality water production by MD (micropollutants-free) and enhanced its reuse potential. The MD concentrated WWROC was suitable for selective ion precipitation, promising a near zero liquid discharge in WRPs.
Aryal, R., Beecham, S., Sarkar, B., Chong, M.N., Kinsela, A., Kandasamy, J. & Vigneswaran, S. 2017, 'Readily Wash-Off Road Dust and Associated Heavy Metals on Motorways', Water, Air, and Soil Pollution, vol. 228, no. 1.
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&copy; 2016, Springer International Publishing Switzerland.Road dust contains a wide range of potentially health-hazardous pollutant sources. In this study, road dust samples were collected from nine locations along the Sydney orbital motorway during wet weather events and analysed for their mineralogy and heavy metal contents. The aim of this study was to examine for the specific particle size fractions in road dust samples that can be associated with anthropogenic pollutant sources, mainly on the prevalence of heavy metals. Surface morphological and elemental composition of the road dust particles was analysed using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). The heavy metal contents and degree of contamination were also investigated including in the two specific particle size fractions of <75 and 75&#8211;150&nbsp;m. It was found that the particle size fraction of <75&nbsp;m made up between 6 and 16% of the entire particle size distributions and contributed to more than 90% of the heavy metal contents. In addition, a moderate to high degree of heavy metal contamination was measured in the collected road dust samples, and this was correlated well with the local traffic volumes. The good correlation between heavy metals and traffic volumes in the finer road dust particle size fraction of <75&nbsp;m indicated that the finer road dust particles were not only important in terms of heavy metal attachment, accumulation and mobilisation during wet weather events but they could also provide evidence of potential anthropogenic pollution sources. These findings will facilitate our scientific understanding on the specific role and importance of particle size fractions on the mobilisation of pollutant sources, particularly heavy metals during wet weather events. It is anticipated that this study will assist in the development of best management practices for pollution prevention and control strategies on the frequency of road sweeping and retention p...
Lee, J., Jeong, S., Ye, Y., Chen, V., Vigneswaran, S., Leiknes, T.O. & Liu, Z. 2017, 'Protein fouling in carbon nanotubes enhanced ultrafiltration membrane: Fouling mechanism as a function of pH and ionic strength', Separation and Purification Technology, vol. 176, pp. 323-334.
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&copy; 2016 Elsevier B.V.The protein fouling behavior was investigated in the filtration of the multiwall carbon nanotube (MWCNT) composite membrane and commercial polyethersulfone ultrafiltration (PES-UF) membrane. The effect of solution chemistry such as pH and ionic strength on the protein fouling mechanism was systematically examined using filtration model such as complete pore blocking, intermediate pore blocking and cake layer formation. The results showed that the initial permeate flux pattern and fouling behavior of the MWCNT composite membrane were significantly influenced by pH and ionic strength while the effect of PES-UF membrane on flux was minimal. In a lysozyme (Lys) filtration, the severe pore blocking in the MWCNT membrane was made by the combined effect of intra-foulant interaction (Lys-Lys) and electrostatic repulsion between the membrane surface and the foulant at pH 7, and increasing ionic strength where the foulant-foulant interaction and membrane-fouling interaction were weak. In a bovine serum albumin (BSA) filtration, severe pore blocking was reduced by less deposition via the electrostatic interaction between the membrane and foulant at pH 4.7 and 10.4 and increasing ionic strength, at which the interaction between the membrane and BSA became weak. For binary mixture filtration, the protein fouling mechanism was more dominantly affected by foulant-foulant interaction (Lys-BSA, Lys-Lys, and BSA-BSA) at pH 7.0 and increase in ionic strength. This research demonstrates that MWCNT membrane fouling can be alleviated by changing pH condition and ionic strength based on the foulant-foulant interaction and the electrostatic interaction between the membrane and foulant.
Loganathan, P., Naidu, G. & Vigneswaran, S. 2017, 'Mining valuable minerals from seawater: A critical review', Environmental Science: Water Research and Technology, vol. 3, no. 1, pp. 37-53.
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&copy;2017 The Royal Society of Chemistry.Seawater contains large quantities of valuable minerals, some of which are very scarce and expensive in their land-based form. However, only a few minerals, the ones in high concentrations, are currently mined from the sea. Due to recent problems associated with land-based mining industries as a result of depletion of high-grade ores, sustainable water and energy demand and environmental issues, seawater mining is becoming an attractive option. This paper presents a comprehensive and critical review of the current methods of extracting valuable minerals from seawater and seawater brines generated in desalination plants, and suggests ways to overcome some of the limitations and challenges associated with the extraction process. The extraction methods discussed are solar evaporation, electrodialysis (ED), membrane distillation crystallisation (MDC), and adsorption/desorption.
Roobavannan, M., Kandasamy, J., Pande, S., Vigneswaran, S. & Sivapalan, M. 2017, 'Allocating Environmental Water and Impact on Basin Unemployment: Role of A Diversified Economy', Ecological Economics, vol. 136, pp. 178-188.
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&copy; 2017 Elsevier B.V.Water diversion for environmental purposes threatens many agricultural communities. This paper focuses on the water-agriculture-environment nexus in the Murrumbidgee River Basin, Australia, and attempts to explain how reduced water allocation to agriculture aimed at protecting the environment in turn impacted the wider economy and the community. Predictably reduced water allocation saw declines in agriculture production and employment. Despite this, paradoxically, the basin unemployment rate declined and basin median household income increased. To understand and interpret this, we first analyze available labour, economic and hydrology data, and then develop a simple dynamic model to interpret the observed pattern of basin employment and unemployment. Data analysis revealed the likely causes behind the paradox as (a) out-migration of people from the basin, and (b) absorption of the labour force in the fast growing non-agricultural sectors of the diversified basin economy. The model simulations reinforced this interpretation. Further model simulations under alternative realities of out-migration and sectoral transformation indicated that basins embedded in faster growing national economies, and are more diversified to begin with, are likely to be more conducive to agriculture sector reform (e.g., reduced water allocation) and environmental regeneration. This is a sobering message for other regions experiencing environmental degradation due to extensive agricultural development.
Sountharajah, D.P., Kus, B., Kandasamy, J. & Vigneswaran, S. 2017, 'Quantifying the reduction in water demand due to rainwater tank installations at residential properties in sydney', Journal of Sustainable Development of Energy, Water and Environment Systems, vol. 5, no. 2, pp. 202-218.
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&copy; 2017, International Centre for Sustainable Development of Energy, Water and Environment Systems SDEWES. All rights reserved.This paper examines data on actual reductions in consumption of water supply due to the widespread installation of rainwater tanks at residential properties in the Sydney metropolitan area and surrounding areas connected to Sydney Water Corporation water supply mains. The water consumption was based on metered potable water usage between 2002 and 2009. The number of properties in the study database totalled 962,697 single residential dwellings. Of this a total of 52,576 or 5.5% of Sydney's households had a rainwater tank registered with Sydney Water Corporation. The water usage consumption before and after the installation of the rainwater tank was analysed to quantify the extent to which rainwater tanks reduced mains water consumption. The average percentage of water savings by installing rainwater tanks across all 44 local government authorities was 9%. In some Sydney localities this reduction was up to 15%. On average, a household was able to save around 24 kilolitre of water annually by installing a rainwater tank even without considering other factors that affect water usage. The results were compared against socio-demographic factors using variables such as household size, educational qualifications, taxable income, rented properties, and non-English-speaking background, etc., to gain an appreciation of how these factors may have influenced the outcomes evident in the data. Among the co-relations found were that most properties within inner Sydney with a rainwater tank achieved at least a 9 to 11% additional reduction in water usage, with more than half of those local government authorities achieving more than 11%; properties with larger land area were more likely to have a rainwater tank installed; local government authorities with more people born in non-English speaking countries had lower reduction in water consumption reductions...
Plattner, J., Naidu, G., Wintgens, T., Vigneswaran, S. & Kazner, C. 2017, 'Fluoride removal from groundwater using direct contact membrane distillation (DCMD) and vacuum enhanced DCMD (VEDCMD)', Separation and Purification Technology, vol. 180, pp. 125-132.
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&copy; 2017 Elsevier B.V.Groundwater resources are under growing pressures in water scarce countries. Membrane distillation (MD) is an interesting option for drinking water production from groundwater with elevated salinity and fluoride (F) contamination. A direct contact MD (DCMD) at a moderate feed temperature of 55 &deg;C was able to concentrate a synthetic solution representing F contaminated groundwater. An average initial flux of 13.3 L/m2/h was achieved at 75% water recovery, resulting in only 15&#8211;17% flux decline, while producing high quality permeate (96&#8211;99% F rejection). Membrane autopsy showed presence of Ca, Na, S and Mg on the used membrane. Particularly, 51&#8211;53% F precipitation was estimated in line with the saturation index (SI) model. The used MD membrane with groundwater showed only 10&#8211;12% reduction in membrane hydrophobicity, which was largely recovered with simple cleaning. Meanwhile, synthetic groundwater solution spiked with humic substances resulted in brownish deposition on MD membrane, reducing the membrane hydrophobicity significantly by 37&#8211;40%. Additionally, DCMD operation with vacuum at the permeate side (vacuum enhanced DCMD; VEDCMD) was beneficial in increasing the permeate flux by 42%. Continuous VEDCMD operation with intermediate membrane cleaning showed positive results in treating F contained groundwater while producing good quality permeate at 67% water recovery.
Kalaruban, M., Loganathan, P., Kandasamy, J. & Vigneswaran, S. 2017, 'Submerged membrane adsorption hybrid system using four adsorbents to remove nitrate from water.', Environ Sci Pollut Res Int.
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Nitrate contamination of ground and surface waters causes environmental pollution and human health problems in many parts of the world. This study tests the nitrate removal efficiencies of two ion exchange resins (Dowex 21K XLT and iron-modified Dowex 21K XLT (Dowex-Fe)) and two chemically modified bio-adsorbents (amine-grafted corn cob (AG corn cob) and amine-grafted coconut copra (AG coconut copra)) using a dynamic adsorption treatment system. A submerged membrane (microfiltration) adsorption hybrid system (SMAHS) was used for the continuous removal of nitrate with a minimal amount of adsorbents. The efficiency of membrane filtration flux and replacement rate of adsorbent were studied to determine suitable operating conditions to maintain the effluent nitrate concentration below the WHO drinking standard limit of 11.3&nbsp;mg N/L. The volume of water treated and the amount of nitrate adsorbed per gramme of adsorbent for all four flux tested were in the order Dowex-Fe&nbsp;>&nbsp;Dowex&nbsp;>&nbsp;AG coconut copra&nbsp;>&nbsp;AG corn cob. The volumes of water treated (L/g adsorbent) were 0.91 and 1.85, and the amount of nitrate removed (mg N/g adsorbent) were 9.8 and 22.2 for AG corn cob and Dowex-Fe, respectively, at a flux of 15&nbsp;L/(m(2)/h).
Sounthararajah, D.P., Loganathan, P., Kandasamy, J. & Vigneswaran, S. 2016, 'Column studies on the removal of dissolved organic carbon, turbidity and heavy metals from stormwater using granular activated carbon', DESALINATION AND WATER TREATMENT, vol. 57, no. 11, pp. 5045-5055.
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Jeong, S., Nguyen, T.V., Vigneswaran, S., Kandasamy, J. & Dharmabalan, D. 2016, 'Removal of natural organic matter at the Gunbower water treatment plant in northern Victoria, Australia', Desalination and Water Treatment, vol. 57, no. 20, pp. 9061-9069.
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&copy; 2015 Balaban Desalination Publications. All rights reserved.Advanced treatment processes are vital if organic matter is to be removed from water as efficiently as possible. To produce high quality water that has low concentrations of natural organic matter (NOM), the Gunbower water treatment plant (WTP) in northern Victoria, Australia has implemented a number of processes including magnetic ion exchange (MIEX), coagulation, clarifier, ultrafiltration (UF), and granular activated carbon (GAC) filtration. This research evaluated the efficiencies of these processes in removing NOM employing various analytical methods, namely liquid chromatography&#8211;organic carbon detector (LC&#8211;OCD) and three-dimensional fluorescence excitation emission matrix (3D-FEEM). In addition, the fouling potential of source water and treated water was assessed using a modified fouling index with ultrafiltration (MFI-UF). Biological stability was also tested using a modified assimilable organic carbon (AOC) detection method. The combination of MIEX, clarifier, coagulation, UF membrane, and GAC filtration resulted in dissolved organic carbon (DOC) being removed (from 6.01 to 0.47&nbsp;mg/L). Furthermore 3D-FEEM analysis revealed that these treatment processes reduced humic and fulvic-like organics. AOC and MFI-UF decreased from 79.94&nbsp;g-C glucose equivalents/L and 46,350 s/L2 in the source water to 4.06&nbsp;g-C glucose equivalents/L and 2,057 s/L2 in the treated water, respectively.
Abdul, J.M., Vigneswaran, S., Kandasamy, J. & Mahinthakumar, G. 2016, 'Fenton Oxidation of Metsulfuron-Methyl with Application to Permeable Reactive Barriers', Environmental Modeling and Assessment, vol. 21, no. 1, pp. 149-158.
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&copy; 2015, Springer International Publishing Switzerland. Laboratory experiments were conducted for removal of metsulfuron-methyl (MeS) by Fenton oxidation using a sand column with multiple sampling points and varied flow rates. The transport and degradation of MeS in a sand column were modeled using an advection diffusion reaction system with rate-limited sorption, hydrolysis and second-order degradation kinetics. Rate constants for MeS adsorption and degradation were obtained by fitting the model to experimental breakthrough curves. Results showed that the residence time is the primary influencing factor in the amount of MeS removal by Fenton oxidation with removal efficiencies exceeding 85&nbsp;%. The column model was extended to two-dimensional porous media, and simulations were conducted to evaluate the feasibility of in situ chemical oxidation using Fenton's reagent in permeable reactor barriers. Results show that Fenton oxidation can yield remediation efficiencies exceeding 80&nbsp;% in permeable reactor barriers when compared to less than 10&nbsp;% with adsorption only.
Naidu, G., Jeong, S., Vigneswaran, S., Jang, E.K., Choi, Y.J. & Hwang, T.M. 2016, 'Fouling study on vacuum-enhanced direct contact membrane distillation for seawater desalination', Desalination and Water Treatment, vol. 57, no. 22, pp. 10042-10051.
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&copy; 2015 Balaban Desalination Publications. All rights reserved. Vacuum-enhanced direct contact membrane distillation (VE-DCMD) has been proposed to improve the DCMD system performance with better effective energy efficiency. However, the higher driving forces by the presence of vacuum pressure at permeate side of the VE-DCMD system could contribute to higher fouling development. In this study, thus, the biochemical fouling development of VE-DCMD with different vacuum pressures (700, 500, and 300&nbsp;mbar) for seawater desalination was investigated in comparison with DCMD (1,000&nbsp;mbar of pressure applied). VE-DCMD showed a significant increase in initial permeate flux while its flux decline was faster than DCMD. Low molecular weight (LMW) organics were found to be a dominant organic foulant on DCMD with thermally disaggregated humic substances (HS) to LMW HS-like organics. On the other hand, the presence of vacuum reduced the disaggregation HS to LMW HS-like organics. However, high driving force of VE-DCMD caused higher deposition of organic foulant including the LMW organics as well as HS. It also led to the higher LMW organic contents in permeate. Fluorescence excitation&#8211;emission matrix (F-EEM) analysis result showed that fulvic-like organic is a dominant HS foulant in VE-DCMD. Fouling development on membrane was observed using scanning electron microscope, contact angle, and confocal laser scanning microscope.
Naidu, G., Jeong, S., Vigneswaran, S., Hwang, T.M., Choi, Y.J. & Kim, S.H. 2016, 'A review on fouling of membrane distillation', Desalination and Water Treatment, vol. 57, no. 22, pp. 10052-10076.
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&copy; 2015 Balaban Desalination Publications. All rights reserved. Membrane distillation (MD) has been developed for the past 40&nbsp;years. Nevertheless, only in recent times, MD technology has shown substantial progress, including the development of a few commercial systems. In this study, a comprehensive review is carried out on the application of MD for the production of drinking water. Based on a broad perspective, this review describes the applications of MD for drinking water production, its advantages, and limitations. Specifically, this review focuses on the scaling and organic fouling phenomena in MD for drinking water production as one of the major challenge to MD implementation. The fouling and wetting phenomena in MD is discussed in detail as well as fouling detection methods, the influence of feed solution characteristics, and operational parameters on MD fouling and related areas requiring future investigations. The study highlights a number of approaches on fouling reduction in MD.
Li, S., Winters, H., Jeong, S., Emwas, A.H., Vigneswaran, S. & Amy, G.L. 2016, 'Marine bacterial transparent exopolymer particles (TEP) and TEP precursors: Characterization and RO fouling potential', Desalination, vol. 379, pp. 68-74.
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&copy; 2015 Elsevier B.V.This paper investigated the characteristics and membrane fouling potential of bacterial transparent exopolymer particles (TEP)/TEP precursors released from two marine bacteria, Pseudidiomarina homiensis (P. homiensis) and Pseudoalteromonas atlantica (P. atlantica), isolated from the Red Sea. Results showed that both bacteria grew at the similar rate, but the production of TEP/TEP precursors from P. atlantica was higher than that from P. homiensis. During the 168. h of incubation time, production rates of TEP/TEP precursors from P. atlantica and P. homiensis were 0.30 and 0.08 xanthan gum eq. mg/L-h, respectively. Isolated bacterial TEP precursors were mainly biopolymer, and P. atlantica produced a significantly higher concentration of biopolymer than that produced by P. homiensis. TEP/TEP precursors from both marine bacteria possessed protein-like material and were very similar in composition to previously reported foulants isolated from a fouled reverse osmosis (RO) membrane. Bacterial TEP/TEP precursors mostly consisted of aliphatic hydrocarbon from amino acids and amide group carbon of proteins (around 55%). Bacterial TEP precursors caused obvious fouling on RO membranes, which may create an ideal environment for bacteria attachment and promote to biofouling.
Johir, M.A.H., Nguyen, T.T., Mahatheva, K., Pradhan, M., Ngo, H.H., Guo, W. & Vigneswaran, S. 2016, 'Removal of phosphorus by a high rate membrane adsorption hybrid system', Bioresource Technology, vol. 201, pp. 365-369.
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&copy; 2015 Elsevier Ltd. Membrane adsorption hybrid system (MAHS) was evaluated for the removal of phosphate from a high rate membrane bioreactor (HR-MBR) effluent. The HR-MBR was operated at permeate flux of 30L/m2 h. The results indicated that the HR-MBR could eliminate 93.1&plusmn;1.5% of DOC while removing less than 53% phosphate (PO4-P). Due to low phosphate removal by HR-MBR, a post-treatment of strong base anion exchange resin (Dowex*21K-XLT), and zirconium (IV) hydroxide were used as adsorbent in MAHS for further removal of phosphate from HR-MBR effluent. It was found that the MAHS enabled to eliminate more than 85% of PO4-P from HR-MBR effluent. Hence, HR-MBR followed by MAHS lead to simultaneous removal of organics and phosphate in a reliable manner. The experiments were conducted only for a short period to investigate the efficiency of these resins/adsorbents on the removal of phosphorus and high rate MBR for organic removal.
Johir, M.A.H., Pradhan, M., Loganathan, P., Kandasamy, J. & Vigneswaran, S. 2016, 'Phosphate adsorption from wastewater using zirconium (IV) hydroxide: Kinetics, thermodynamics and membrane filtration adsorption hybrid system studies', JOURNAL OF ENVIRONMENTAL MANAGEMENT, vol. 167, pp. 167-174.
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Kalaruban, M., Loganathan, P., Shim, W.G., Kandasamy, J., Naidu, G., Nguyen, T.V. & Vigneswaran, S. 2016, 'Removing nitrate from water using iron-modified Dowex 21K XLT ion exchange resin: Batch and fluidised-bed adsorption studies', SEPARATION AND PURIFICATION TECHNOLOGY, vol. 158, pp. 62-70.
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Choi, Y., Vigneswaran, S. & Lee, S. 2016, 'Evaluation of fouling potential and power density in pressure retarded osmosis (PRO) by fouling index', Desalination, vol. 389, pp. 215-223.
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Pressure retarded osmosis (PRO) is an osmotically-driven membrane process to utilize salinity gradient power (SGP), which is renewable energy originated from the different salt concentration between seawater and fresh water. However, PRO suffers from membrane fouling, leading to decreased water permeability and energy density. Although prediction of fouling is important for its mitigation and control, little information is available on fouling potential in PRO process. Accordingly, this study aims at the investigation of fouling propensity of PRO membranes under different conditions. Feed solutions that have different fouling potential were used in a laboratory-scale PRO system. Silt density index (SDI) and modified fouling index (MFI) were applied as indicators for assessing PRO membrane fouling. Results showed that the power density of PRO decreases with an increase of the fouling potential of the feed waters. MFI was proposed to be a fouling index for PRO because it showed a better correlation with the power density than SDI and turbidity. When MFI value is lower than 1400s/L2, the efficiency is higher than 70%, indicating that 30% loss in energy recovery compared to the case with D.I. water. This suggests that pretreatment requirements for PRO may be determined based on MFI results.
Johir, M.A.H., Shim, W.G., Pradhan, M., Vigneswaran, S. & Kandasamy, J. 2016, 'Benefit of adding adsorbent in submerged membrane microfiltration treatment of wastewater', Desalination and Water Treatment, vol. 57, no. 44, pp. 20683-20693.
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In this study, the effect of coupling ion-exchange resin (purolite) and powdered activated carbon (PAC) in a submerged membrane reactor was investigated in terms of (i) removal of different classes of organic matter and (ii) reduction of membrane fouling. The degree of fouling in a membrane hybrid system was modelled in terms of transmembrane pressure development and organic removal efficiency using a simple semi-empirical model. Among these three absorbents, PAC was the most effective with higher removal efficiency for DOC (almost 100% reduction of hydrophobic organic compounds). Excitation&#8211;emission matrix analysis and LC&#8211;OCD were employed for the detailed organic characterisation.
Jeong, S., Vollprecht, R., Cho, K., Leiknes, T.O., Vigneswaran, S., Bae, H. & Lee, S. 2016, 'Advanced organic and biological analysis of dual media filtration used as a pretreatment in a full-scale seawater desalination plant', Desalination, vol. 385, pp. 83-92.
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&copy; 2016 Elsevier B.V.Dual media filter (DMF) is being used as a primary pretreatment to remove particulate foulants at seawater desalination plants. However, many plants experience organic and biological fouling. The first part of this paper focuses on the monitoring of organic and biological foulants using advanced analytical techniques to optimize functioning of DMF at Perth Seawater Desalination Plant (PSDP) in Western Australia. In addition, microbial community analysis in DMF filtered seawater, and on DMF media (DMF-M) and cartridge filter (CF) was conducted using terminal restriction fragment length polymorphism (T-RFLP) and 454-pyrosequencing. In the full-scale DMF system, the bacterial community structure was clustered along with the filtration time and sampling positions. For the DMF effluent samples, the bacterial community structure significantly shifted after 4 h of filtration time, which corresponded with the permeability reduction trend. The dominant bacterial communities in the DMF effluent were OTU 13 (Phaeobacter) and OTU 19 (Oceaniserpentilla). The different biofilm-forming bacteria communities were found in the biofilm samples on DMF-M and CF. In the second part of the study, semi-pilot scale DMF columns were operated on-site under same operating conditions used in PSDP. It demonstrated the advantage of operating DMF at the biofiltration mode for improving the reduction of biofoulants.
Nur, T., Loganathan, P., Kandasamy, J. & Vigneswaran, S. 2016, 'Phosphate Adsorption from Membrane Bioreactor Effluent Using Dowex 21K XLT and Recovery as Struvite and Hydroxyapatite', INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH, vol. 13, no. 3.
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Naidu, G., Nur, T., Loganathan, P., Kandasamy, J. & Vigneswaran, S. 2016, 'Selective sorption of rubidium by potassium cobalt hexacyanoferrate', SEPARATION AND PURIFICATION TECHNOLOGY, vol. 163, pp. 238-246.
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Jeong, S., Cho, K., Bae, H., Keshvardoust, P., Rice, S.A., Vigneswaran, S., Lee, S. & Leiknes, T.O. 2016, 'Effect of microbial community structure on organic removal and biofouling in membrane adsorption bioreactor used in seawater pretreatment', Chemical Engineering Journal, vol. 294, pp. 30-39.
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&copy; 2016 Elsevier B.V.Membrane bioreactors (MBRs) were operated on-site for 56 d with different powdered activated carbon (PAC) dosages of 0, 1.5 and 5.0 g/L to pretreat seawater for reverse osmosis desalination. It was hypothesized that PAC would stimulate adsorption and biological degradation of organic compounds. The microbial communities responsible for biofouling on microfiltration (MF) membranes and biological organic removal in MBR were assessed using terminal restriction fragment length polymorphism fingerprinting and 454-pyrosequencing. The PAC addition improved assimilable organic carbon removal (53-59%), and resulted in reduced biofouling development on MF (>50%) with only a marginal development in trans-membrane pressure. Interestingly, the bacterial community composition was significantly differentiated by the PAC addition. Cyanobacterium, Pelagibaca and Maricoccus were dominant in the PAC-free conditions, while Thiothrix and Sphingomonas were presumably responsible for the better reactor performances in PAC-added conditions. In contrast, the archaeal communities were consistent with predominance of Candidatus Nitrosopumilus. These data therefore show that the addition of PAC can improve MBR performance by developing different bacterial species, controlling AOC and associated biofouling on the membranes.
Jeong, S., Naidu, G., Vollprecht, R., Leiknes, T.O. & Vigneswaran, S. 2016, 'In-depth analyses of organic matters in a full-scale seawater desalination plant and an autopsy of reverse osmosis membrane', Separation and Purification Technology, vol. 162, pp. 171-179.
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&copy; 2016 Elsevier B.V. All rights reserved.In order to facilitate the global performance of seawater reverse osmosis (SWRO) systems, it is important to improve the feed water quality before it enters the RO. Currently, many desalination plants experience production losses due to incidents of organic and biofouling. Consequently, monitoring or characterizing the pretreatment step using more advanced organic and biological parameters are required for better operation to lessen fouling issues. In this study, the performance of pretreatment processes (including coagulation, dual media filtration (DMF), polishing with cartridge filter (CF) coupled with anti-scalant) used at Perth Seawater Desalination Plant (PSDP) located in Western Australia were characterized in terms of organic and biological fouling parameters. These analyses were carried out using liquid chromatography with organic carbon detector (LC-OCD), three dimensional-fluorescence excitation emission matrix (3D-FEEM) and assimilable organic carbon (AOC). Furthermore, the used (exhausted) RO membrane and CF were autopsied so that the fates and behaviors of organic foulants in these treatment systems could be better understood.
To, V.H.P., Nguyen, T.V., Vigneswaran, S., Duc Nghiem, L., Murthy, S., Bustamante, H. & Higgins, M. 2016, 'Modified centrifugal technique for determining polymer demand and achievable dry solids content in the dewatering of anaerobically digested sludge', Desalination and Water Treatment, vol. 57, no. 53, pp. 25509-25519.
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&copy; 2016 Balaban Desalination Publications. All rights reserved. This study aims to characterize anaerobically digested sludge (ADS) and correlate the sludge characteristics in terms of soluble organic compounds with polymer demand (PD) during sludge conditioning. The PD required to achieve maximum dewatering of the ADS studied is in the range of 8&#8211;10&nbsp;kg polymer/dry ton. The commonly used capillary suction time parameter to evaluate the solid&#8211;liquid separation ability was not a reliable indicator for assessing dewatering. Instead, in this study, a modified centrifugal technique proposed by Higgins (Higgins MCT) was used to assess the maximum achievable dry solids content of the biosolids cake. The Higgins MCT is readily obtained using a bench-scale centrifuge equipped with a modified centrifuge bucket. Using the Higgins MCT, the maximum dry solids contents obtained from conditioned ADS was 30&nbsp;wt%. These values were comparable to the dry solids content obtained from the same sludge at full-scale level. Our results suggest Higgins MCT is suitable for assessing the final dry solids content and simulating the dewatering process.
Lee, J., Jeong, S., Naidu, G., Ye, Y., Chen, V., Liu, Z. & Vigneswaran, S. 2016, 'Performance evaluation of carbon nanotube enhanced membranes for SWRO pretreatment application', Journal of Industrial and Engineering Chemistry, vol. 35, no. 8, pp. 123-131.
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&copy; 2016 The Korean Society of Industrial and Engineering Chemistry. Multi-wall carbon nanotube (MWCNT) membrane was tested for SWRO pretreatment. The MWCNT membrane itself showed a superior permeate flux (321.3. LMH/bar), which was 4-times as polyethersulfone ultrafiltration (PES-UF) membrane. Reduction of dissolved organic matter improved to 66% with fewer amounts of powder activated carbon (PAC) (0.5. g/L) in MWCNT membrane filtration maintaining a high permeate flux of 600. LMH/bar. It was due to the increased porosity (84.5%) and hydrophilicity (52.9&deg;) by incorporating MWCNT/polyaniline into PES membrane. Ionic strength affected organic removal in seawater filtration by altering electrostatic interaction between organic matter and surface charge of the positively charged MWCNT membrane.
Kalaruban, M., Loganathan, P., Shim, W.G., Kandasamy, J., Ngo, H.H. & Vigneswaran, S. 2016, 'Enhanced removal of nitrate from water using amine-grafted agricultural wastes', SCIENCE OF THE TOTAL ENVIRONMENT, vol. 565, pp. 503-510.
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Nur, T., Naidu, G., Loganathan, P., Kandasamy, J. & Vigneswaran, S. 2016, 'Rubidium recovery using potassium cobalt hexacyanoferrate sorbent', DESALINATION AND WATER TREATMENT, vol. 57, no. 55, pp. 26577-26585.
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To, V.H.P., Nguyen, T.V., Vigneswaran, S. & Ngo, H.H. 2016, 'A review on sludge dewatering indices.', Water Science and Technology, vol. 74, no. 1, pp. 1-16.
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Dewatering of sludge from sewage treatment plants is proving to be a significant challenge due to the large amounts of residual sludges generated annually. In recent years, research and development have focused on improving the dewatering process in order to reduce subsequent costs of sludge management and transport. To achieve this goal, it is necessary to establish reliable indices that reflect the efficiency of sludge dewatering. However, the evaluation of sludge dewaterability is not an easy task due to the highly complex nature of sewage sludge and variations in solid-liquid separation methods. Most traditional dewatering indices fail to predict the maximum cake solids content achievable during full-scale dewatering. This paper reviews the difficulties in assessing sludge dewatering performance, and the main techniques used to evaluate dewatering performance are compared and discussed in detail. Finally, the paper suggests a new dewatering index, namely the modified centrifugal index, which is demonstrated to be an appropriate indicator for estimating the final cake solids content as well as simulating the prototype dewatering process.
Naidu, G., Loganathan, P., Jeong, S., Johir, M.A.H., To, V.H.P., Kandasamy, J. & Vigneswaran, S. 2016, 'Rubidium extraction using an organic polymer encapsulated potassium copper hexacyanoferrate sorbent', CHEMICAL ENGINEERING JOURNAL, vol. 306, pp. 31-42.
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Jamil, S., Jeong, S. & Vigneswaran, S. 2016, 'Application of pressure assisted forward osmosis for water purification and reuse of reverse osmosis concentrate from a water reclamation plant', SEPARATION AND PURIFICATION TECHNOLOGY, vol. 171, pp. 182-190.
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Vigneswaran, S., Kandasamy, J. & Johir, M.A.H. 2016, 'Sustainable Operation of Composting in Solid Waste Management', Procedia Environmental Sciences, vol. 35, pp. 408-415.
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Nur, T., Shim, W.G., Loganathan, P., Vigneswaran, S. & Kandasamy, J. 2015, 'Nitrate removal using Purolite A520E ion exchange resin: batch and fixed-bed column adsorption modelling', International Journal of Environmental Science and Technology, vol. 12, no. 4, pp. 1311-1320.
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Removing excessive nitrate from water is essential because it causes eutrophication which in turn has a harmful effect on aquatic life, resulting in a reduction in biodiversity and posing a danger to peoples health when the water is used for drinking. In this study, nitrate removal from aqueous solutions was studied using an ion exchange resin (Purolite A520E) in batch and fixed-bed column experiments. Batch adsorption kinetics was very well described by pseudo-first-order, pseudo-second-order and homogeneous surface diffusion models for resin doses 1.5 and 3.0 g/L at a nitrate concentration 20 mg N/L. Column kinetic data satisfactorily fitted to the empirical Thomas model and a numerical model based on advection dispersion equation for filtration velocities 2.5 and 5.0 m/h at a column height of 12 cm and inlet concentration 20 mg N/L. The experimental and Thomas model predicted breakthrough adsorption capacity ranges for the two filtration rates were 12.013.5 and 8.29.7 mg N/g, respectively, whereas the maximum adsorption capacity determined using Langmuir adsorption isotherm model in the batch study was 32.2 mg N/g.
Kunhikrishnan, A., Shon, H., Bolan, N.S., El Saliby, I. & Vigneswaran, S. 2015, 'Sources, distribution, environmental fate and ecological effects of nanomaterials in wastewater streams', Critical Reviews in Environmental Science and Technology, vol. 45, no. 4, pp. 277-318.
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Engineered nanomaterials (ENM) are manufactured, as opposed to being an incidental by-product of combustion or a natural process, and they often have unique or novel properties that emerge from their small size. These materials are being used in an expanding array of consumer products and, like all technological developments, have both benefits and risks. As the use of ENM in consumer products becomes more common, the amount of these nanomaterials entering wastewater stream increases. Estimates of nanomaterials production are in the range of 500 and 50,000 tons per year for silver and titanium dioxide (TiO2) alone, respectively. Nanomaterials enter the wastewater stream during the production, usage, and disposal of nanomaterial-containing products. The predicted values of nanomaterials range from 0.003 (fullerenes) to 21 ng L1 (nano-TiO2) for surface waters, and from 4 ng L1 (fullerenes) to 4 g L1 (nano-TiO2) for sewage treatment effluents. Therefore, investigating the fate of nanomaterials in wastewater streams is critical for risk assessment and pollution control. The authors aim first to identify the sources of nanomaterials reaching wastewater streams, then determine their occurrence and distribution, and finally discuss their fate in relation to human and ecological health, and environmental impact.
Thankappan, R., Nguyen, T.V., Srinivasan, S.V., Vigneswaran, S., Kandasamy, J. & Loganathan, P. 2015, 'Removal of leather tanning agent syntan from aqueous solution using Fenton oxidation followed by GAC adsorption', JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY, vol. 21, pp. 483-488.
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Shanmuganathan, S., Johir, M.A.H., Nguyen, T.V., Kandasamy, J. & Vigneswaran, S. 2015, 'Experimental evaluation of microfiltration-granular activated carbon (MF-GAC)/nano filter hybrid system in high quality water reuse', JOURNAL OF MEMBRANE SCIENCE, vol. 476, pp. 1-9.
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Shanmuganathan, S., Vigneswaran, S., Nguyen, T.V., Loganathan, P. & Kandasamy, J. 2015, 'Use of nanofiltration and reverse osmosis in reclaiming micro-filtered biologically treated sewage effluent for irrigation', DESALINATION, vol. 364, pp. 119-125.
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Naidu, G., Jeong, S. & Vigneswaran, S. 2015, 'Interaction of humic substances on fouling in membrane distillation for seawater desalination', Chemical Engineering Journal, vol. 262, pp. 946-957.
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&copy; 2014 Elsevier B.V.The interaction of humic substances on organic and biofouling during the treatment of seawater using direct contact membrane distillation (DCMD) was studied. Organic fouling was investigated at different feed temperatures in terms of distillate flux pattern and detailed organic characterization using liquid chromatography-organic carbon detection. The penetration of organics through the membrane pores was observed with SEM cross-section analysis. Also, chemical cleaning analysis showed seawater organic fouling was irreversible in DCMD. Humic substances and low molecular weight (LMW) organics are dominant organic contents in seawater. In the tested DCMD system, humic substances were thermally disaggregated to LMW-humic organics. This phenomenon was more significant in the presence of salt (NaCl), while inorganic scalant (CaSO4) reduced the disaggregation of humic substances due to the binding effect. In this study, the assimilable organic carbon (AOC) test was used to estimate the biological fouling potential during the MD process. AOC concentration is closely associated with biofilm growth in water and on the membrane (biofouling). The AOC concentration increased as the concentration of LMW-humic organics increased. This indicated the possibility of biofouling increasing in the feed and on the membrane in the MD process.
Sounthararajah, D.P., Loganathan, P., Kandasamy, J. & Vigneswaran, S. 2015, 'Adsorptive removal of heavy metals from water using sodium titanate nanofibres loaded onto GAC in fixed-bed columns', JOURNAL OF HAZARDOUS MATERIALS, vol. 287, pp. 306-316.
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Nguyen, T.C., Loganathan, P., Nguyen, T.V., Vigneswaran, S., Kandasamy, J. & Naidu, R. 2015, 'Simultaneous adsorption of Cd, Cr, Cu, Pb, and Zn by an iron-coated Australian zeolite in batch and fixed-bed column studies', CHEMICAL ENGINEERING JOURNAL, vol. 270, pp. 393-404.
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Shanmuganathan, S., Nguyen, T.V., Jeong, S., Kandasamy, J. & Vigneswaran, S. 2015, 'Submerged membrane – (GAC) adsorption hybrid system in reverseosmosis concentrate treatment', Separation and Purification Technology, vol. 146, pp. 8-14.
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Wastewater reclamation plants using reverse osmosis as the final polishing treatment produce reverse osmosis concentrate (ROC), which consists of high salinity, nutrients and (recalcitrant) organics. The ROC collected from the water reclamation plant in Sydney was treated with a micro filtration (MF)&#8211;GAC hybrid system that removed natural and synthetic organics prior to its discharge into the environment. The MF&#8211;GAC hybrid system's performance was studied in terms of trans-membrane pressure (TMP) development, and organics removal. These features were measured using liquid chromatography&#8211;organic carbon detection (LC&#8211;OCD), Fluorescence Excitation-Emission matrix (F-EEM), and Liquid chromatography with tandem mass spectroscopy (LC&#8211;MS). Adding GAC into the membrane reactor reduced the TMP by reducing membrane fouling both through mechanical scouring and pre-adsorption of organics. F-EEM confirms the removal of humics-like and fulvic-like compounds by GAC from ROC. Pharmaceuticals and personal care products (PPCPs) were also removed by the MF&#8211;GAC hybrid system
Nguyen, T., Logananthan, P., Tien Vinh, N., Thi TN, P., Jaya, K., Wu, M., Naidu, R. & Vigneswaran, S. 2015, 'Trace elements in road-deposited and water bed sediments in Kogarah Bay of Sydney, Australia: Enrichment, sources, and fractionation', Soil Research.
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Road-deposited sediments (RDS) are a potential source of trace elements (TE) that can be transported by stormwater to neighbouring water bodies and cause aquatic pollution. A study in Sydney, Australia showed that of the 11 TE analysed, Zn, Cu, V, Cr, and Sb were greatly enriched in RDS compared to those in baseline soils (BS). All TE concentrations in water bed-sediments (WBS) in the catchment area were similar to those in the BS. Correlation and principal component analyses revealed that of the five TE enriched in RDS, Zn, Cu, Cr and Sb were related to each other, and they probably originated from vehicle components such as tyres and brake linings. Vanadium was separated into another component, likely to have originated mainly from road surface asphalt abrasion. Trace element concentrations in the mobile fraction of RDS, determined using a sequential extraction method, were: Fe >Mn, Zn > Cu, Pb> Cr, Ni, V, Cd, Sb. However, this fraction as a percentage of total elemental concentration was highest for Cd and Zn and lowest for Fe, Cr, Ni, and V. The RDS sites had low-medium ecological risk whereas WBS and BS sites had low risk.
Rattananurak, W., Chang, J.S., Wattanachira, S., Johir, M.A.H. & Vigneswaran, S. 2015, 'A novel plate settler in immersed membrane bioreactor (iMBR) in reducing membrane fouling', Desalination and Water Treatment, vol. 55, no. 1, pp. 10-16.
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&copy; 2014 Balaban Desalination Publications. All rights reserved.Abstract: Membrane separation technology has been widely applied in water and wastewater treatments, especially in the water reclamation and recycling. However, the membrane fouling decreases the membrane efficiency and increases the cost of the process, thus limiting the membrane application. There are two types of membrane bioreactors (MBRs), immersed (iMBR) and side streamed. However, the membrane surfaces of these two types of MBR are always directly exposed to high concentration of suspended solids (SS) and easily get fouling. A novel MBR was designed to reduce membrane fouling. Incorporation of inclined plate in MBR can separate high SS from direct contact with the membrane surface and decreases membrane fouling. The iMBR used in this study consists of an aeration zone, a settling zone, and a filtration zone. The reactor operated under the upflow mode of operation with 0.06 m membrane pore size and with and without membrane backwashing. The results showed that the novel iMBR can reduce the SS concentration in the filtration zone up to 97.3% and increase the permeate flux over 41.9% than that of normal iMBR.
Vigneswaran, S. & Kwon, D.Y. 2015, 'Effect of ionic strength and permeate flux on membrane fouling: Analysis of forces acting on particle deposit and cake formation', KSCE Journal of Civil Engineering, vol. 19, no. 6, pp. 1604-1611.
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&copy; 2015, Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg. In Cross-Flow Microfiltration (CFMF), suspended particles deposit to form a cake layer on the membrane surface, which provides a resistance to permeate flow. The cake resistance, which plays an important role on the performance of CFMF, is mainly determined by the packing porosity of the cake and, the physical and chemical properties of particles. This study aimed at understanding the porosity and the specific filtration resistance of the cake for a given condition. These properties have been studied using experiments under a constant permeate flux. Factors such as permeate flux and ionic strength were investigated in terms of the particles deposition and cake formation. This study also adopted a force balance model to predict the deposit rate of particles and then compare with the experimental results. Inter-particle forces (electric double layer repulsion force and Van der Waals attraction force) were incorporated into the calculation of cake structure (cake porosity and specific resistance) together with the equilibrium condition of hydrodynamic forces. The experimental results showed that the higher the permeate flux led to the greater amount of particles deposit and the denser structure of cake. The porosity of cake decreased with the increase in ionic strength (00.01M) and then increased sharply afterwards (0.010.1M). The hydrodynamic force balance model estimated well the tendency of variation in cake structure depending on the ionic strength.
Shrestha, A., Johir, M.A.H., Vigneswaran, S. & Kandasamy, J. 2015, 'A comparative study on in-line flocculation and spiral flocculation followed by media filtration as a pre-treatment of seawater', Desalination and Water Treatment, vol. 55, no. 4, pp. 892-900.
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&copy; 2014 Balaban Desalination Publications. All rights reserved. Abstract: In this study the efficiency of two different flocculation systems namely in-line flocculation and spiral flocculation followed by media filtration (sand or anthracite) have been investigated as a pre-treatment of seawater to reverse osmosis. The performances of these filtration systems were assessed in terms of turbidity removal, head loss development, ultra filter-modified fouling index (UF-MFI) and organic matters removal. Both systems showed 60&#8211;70% removal of turbidity. In-line flocculation and filtration showed 2&#8211;3 times higher head loss development than spiral flocculation filtration. These filtration systems helped to reduce the fouling potential (in terms of UF-MFI) by 50&#8211;73%, whereas dissolved organic carbon-removal efficiency was 30&#8211;45%. The fractionation of organic matter showed that both systems removed 70% of hydrophobic organic matters. The removals of hydrophilic organics were around 30&#8211;40%. Among the hydrophilic compounds, the removal of biopolymer and lower molecular weight neutrals and acid were higher than that of humic substances' and building blocks'.
Jamil, S., Loganathan, P., Kazner, C. & Vigneswaran, S. 2015, 'Forward osmosis treatment for volume minimisation of reverse osmosis concentrate from a water reclamation plant and removal of organic micropollutants', DESALINATION, vol. 372, pp. 32-38.
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Sounthararajah, D.P., Loganathan, P., Kandasamy, J. & Vigneswaran, S. 2015, 'Effects of Humic Acid and Suspended Solids on the Removal of Heavy Metals from Water by Adsorption onto Granular Activated Carbon', INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH, vol. 12, no. 9, pp. 10475-10489.
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Pramanik, B.K., Roddick, F.A., Fan, L., Jeong, S. & Vigneswaran, S. 2015, 'Assessment of biological activated carbon treatment to control membrane fouling in reverse osmosis of secondary effluent for reuse in irrigation', Desalination, vol. 364, pp. 90-95.
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&copy; 2015 Elsevier B.V.Biologically treated secondary effluent (BTSE) is being used increasingly as a source of water for irrigation purposes. Biological activated carbon (BAC) was investigated as a pre-treatment to reduce the organic fouling and biofouling potential of reverse osmosis (RO) membranes for the desalination of a moderately saline BTSE to be used for agricultural purposes. The BAC reduced the organic content through biodegradation by the microorganisms and adsorption by the activated carbon, and subsequent microfiltration (0.1. m PVDF) further reduced the organic content and thus fouling of the RO membrane. The BAC treatment was shown to effectively reduce the biodegradable dissolved organic carbon and assimilable organic carbon contents, and the bacterial regrowth potential, thus confirming its potential for mitigating biofouling of the RO membrane. The improved RO performance demonstrated that this process was effective for reducing the fouling propensity of the BTSE to enable its sustainable application for producing an effluent with a high reuse potential for irrigation purposes. The RO permeate can then be blended with untreated water to produce a product with a suitable inorganic content for irrigation.
Jeong, S. & Vigneswaran, S. 2015, 'Practical use of standard pore blocking index as an indicator of biofouling potential in seawater desalination', Desalination, vol. 365, pp. 8-14.
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&copy; 2015 Elsevier B.V.A practical approach to evaluate the biofouling potential of feed waters for seawater reverse osmosis (SWRO) was investigated. Assimilable organic carbon (AOC) and modified fouling index through an ultrafiltration 10kDa membrane (MFI-UF10) were measured for seawater and pretreated seawater. The pretreatments adopted were dual media filtration (DMF) coupled with coagulation and submerged membrane adsorption bioreactor (SMABR). Low molecular weight neutrals (LMW-N) responsible for biological growth (or biofouling) constituted the major component in seawater and pretreated seawater. A very good linear relationship was observed between AOC concentration and LMW-N concentration. A detailed study on various fouling indices revealed that standard blocking index (Ks) calculated from MFI-UF10 correlated with AOC concentration. This indicates that MFI-UF10 test can serve as a preliminary indicator of AOC and LMW-N (which are biofouling precursors). MFI-UF10 can also be used directly in desalination plants.
Pradhan, M., Vigneswaran, S. & Kandasamy, J. 2015, 'Assessment of fouling behaviour in submerged microfiltration system coupled with flocculation', Journal of Industrial and Engineering Chemistry, vol. 21, pp. 254-260.
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&copy; 2014 The Korean Society of Industrial and Engineering Chemistry.Microfiltration coupled with flocculation has the potential to remove colloidal and dissolved matter and hence mitigate membrane fouling. This study investigates the effects of flocculation on the performance of submerged membrane microfiltration of kaolin suspension. The addition of the flocculent (ferric chloride: FeCl3) demonstrated better control of colloidal membrane fouling. The experimental results showed that trans-membrane pressure (TMP) development at optimal flocculent concentration was significantly less than it was with an unflocculated feed. In the case of 30 L/m2/h, TMP was reduced by 85% with optimum concentration of flocculent. A regression analysis conducted between cake resistance and particle deposition showed a low specific cake resistance with flocculent addition.
Azizur Rahman, M., Hogan, B., Duncan, E., Doyle, C., Rahman, M.M., Nguyen, T.V., Lim, R.P., Maher, W., Naidu, R., Krassoi, R., Vigneswaran, S. & Hassler, C. 2015, 'Ecotoxicological Effects of an Arsenic Remediation Method on Three Freshwater Organisms - Lemna disperma, Chlorella sp. CE-35 and Ceriodaphnia cf. dubia', Water, Air, and Soil Pollution, vol. 226, no. 12, pp. 1-10.
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&copy; 2015 Springer International Publishing Switzerland.Chemical methods have been used for the remediation of arsenic (As)-contaminated water; however, ecological consequences of these methods have not been properly addressed. The present study evaluated the effects of the Fe-oxide-coated sand (IOCS) remediation method on As toxicity to freshwater organisms (Lemna disperma, Chlorella sp. CE-35, and Ceriodaphnia cf. dubia). The As removal efficiency by IOCS decreased substantially with time. The IOCS remediation method was less effective at suppressing the toxicity of AsV than AsIII to L. disperma but was highly effective in reducing both the AsIII and AsV toxicity to C. cf. dubia. The growth of Chlorella sp. was significantly higher (p < 0.05) in remediated and pre-remediated water than in controls (non-As-contaminated filtered Colo River water) for AsIII, while the opposite was observed for AsV, indicating that AsV is more toxic than AsIII to this microalga. Although the IOCS can efficiently remove As from contaminated water, residual As and other constituents (e.g. Fe, nitrate) in the remediated water had a significant effect on freshwater organisms.
Guo, H., Lim, F.Y., Zhang, Y., Lee, L.Y., Hu, J.Y., Ong, S.L., Yau, W.K. & Ong, G.S. 2015, 'Soil column studies on the performance evaluation of engineered soil mixes for bioretention systems', Desalination and Water Treatment, vol. 54, no. 13, pp. 3661-3667.
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Chanan, A.P., Vigneswaran, S., Kandasamy, J.K. & Singh, G. 2014, 'Beverley Park water reuse plant: getting the salt just right', Desalination and Water Treatment, vol. in press, pp. 1-8.
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The extraction type wastewater recycling systems are those where wastewater is taken from the collection system en route to the central treatment plant. This paper discusses a case study of Sydneys first ever extraction type scheme, the Beverley Park water reuse scheme. Primary applications of recycled water from this case study site include: parks and ovals, green-belt and golf course irrigation. Given the plants location on a major interceptor sewer along Kogarah Bay, tidal influx posed a significant challenge due to high salt levels. Salt sensitive grass on golf course greens meant that treated water had to meet stringent quality requirements with regards to salt. The design involved modelling the process of diurnal fluctuations in salt levels and to provide an optimised process design. A non-membrane, design based solution was also chosen to resolve this high salinity challenge. This Case Study highlights the significant challenges in planning, design and commissioning of water reuse plant intercepting sewer carriers prone to salt water intrusion. The study provides valuable knowledge that will assist in providing viable extraction type water reuse schemes for tidal impacted areas.
Nur, T., Johir, M.A.H., Loganathan, P., Vigneswaran, S. & Kandasamy, J. 2014, 'Effectiveness of purolite A500PS and A520E ion exchange resins on the removal of nitrate and phosphate from synthetic water', Desalination and Water Treatment.
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Water pollution due to the excessive presence of nutrients (nitrogen and phosphorus) is a serious environmental worldwide problem, because both species are implicated in the eutrophication of receiving surface waters and elevated nitrate concentration in drinking water can be toxic to infants. The removal efficiencies of nitrate and phosphate from water spiked with different ratios and concentrations of these nutrients by two ion-exchange resins (Purolite A500PS and Purolite A520E) were studied in batch kinetics and equilibrium adsorption experiments. Both purolites were found to be selective towards nitrate removal at all ratios of nitrate to phosphate in solution. Purolite A520E showed higher (<85%) removal efficiency of nitrate than Purolite A500PS (about 65%) from a solution containing 20mgN/L as nitrate and 10mgP/L as phosphate at a resin dose of 1.5 g/L. However, Purolite A500PS showed higher (65%) removal of phosphate than Purolite A520E (48%). Langmuir and Freundlich isotherm models fitted well for the adsorption of nitrate on Purolite A520E (R2 = 0.950.96). However, the adsorption of nitrate on Purolite A500PS can be explained satisfactorily only by Freundlich model (R2 = 0.98). The adsorption of phosphate on the resins fitted well to Freundlich model (R2 = 0.90) for Purolite A500PS as well as for Purolite A520E (R2 = 0.90). The adsorption of phosphate and nitrate on both ion-exchange resins was much better described by pseudo-second-order kinetic model (R2P0.99) than by pseudo-first-order kinetic model (R2 = 0.250.94).
Naidu, G., Choi, Y., Jeong, S., Hwang, T. & Vigneswaran, S. 2014, 'Experiments and modeling of a vacuum membrane distillation for high saline water', Journal of Industrial and Engineering Chemistry, vol. 20, no. 4, pp. 2174-2183.
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Danasamy, G., Jeong, S. & Vigneswaran, S. 2014, 'Influence of feed/permeate velocity on scaling development in a direct contact membrane distillation', Separation and Purification Technology, vol. 125, pp. 291-300.
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Danasamy, G., Jeong, S., S-J, K., Kim, I.S. & Vigneswaran, S. 2014, 'Organic fouling behavior in direct contact membrane distillation', Desalination, vol. 347, pp. 230-239.
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Jeong, S., Sathasivan, A.S., Kastl, G., Shim, W. & Vigneswaran, S. 2014, 'Experimental investigation and modeling of dissolved organic carbon removal by coagulation from seawater', Chemosphere, vol. 95, pp. 310-316.
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Nur, T., Johir, M.A.H., Loganathan, P., Nguyen, T., Vigneswaran, S. & Kandasamy, J. 2014, 'Phosphate removal from water using an iron oxide impregnated strong base anion exchange resin', Journal of Industrial and Engineering Chemistry, vol. 20, pp. 1301-1307.
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Removing phosphate from water is important as it causes eutrophication, which in turn has a harmful effect on aquatic life, resulting in a reduction in biodiversity. On the other hand, recovery of phosphate from phosphorus containing wastewater is essential for developing an alternative source of phosphorus to overcome the global challenge of phosphorus scarcity. Phosphate removal from aqueous solutions was studied using an iron oxide impregnated strong base anion exchange resin, Purolite FerrIX A33E in batch and fixed-bed column experiments. Phosphate adsorption in the batch study satisfactorily fitted to the Langmuir isotherm with a maximum adsorption capacity of 48 mg P/g. In the column study, increase in inlet phosphate concentration (530 mg P/L), and filtration velocity (2.510 m/h) resulted in faster breakthrough times and increase in breakthrough adsorption capacities. Increase in bed height (3 19 cm) also increased adsorption capacity but the breakthrough time was slower. The breakthrough data were reasonably well described using the empirical models of BohartAdams, Thomas, and Yoon Nelson, except for high bed heights. Phosphate adsorbed was effectively desorbed using 1 M NaOH and the adsorbent was regenerated after each of three adsorption/desorption cycles by maintaining the adsorption capacity at >90% of the original value. Greater than 99.5% of the desorbed P was recovered by precipitation using CaCl2.
Hossain, A., Ngo, H., Guo, W., Nguyen, V. & Vigneswaran, S. 2014, 'Performance of cabbage and cauliflower wastes for heavy metals removal', Desalination and Water Treatment, vol. 52, pp. 844-860.
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From this study, the cabbage and cauliflower, a well-known agro-waste were used as biosorbents for removing toxic lead(II) and cadmium(II) from water. A batch of experiments for both biosorbents indicated that the lead(II) and cadmium(II) sorption depended on pH (5.06.5), doses of biosorbents (38 g/L) and contact time (1545 min). The adsorption processes were fast, and equilibrium time was reached at 45 and 15 min for lead(II) and 45 and 30 min for cadmium(II) adsorption onto cabbage and cauliflower biosorbents, respectively. Both biosorbents showed higher preferences for lead(II) than cadmium(II) towards adsorption from a binary solution. Langmuir model was the best-predicted model, but threeparameter models (Redlich-Peterson, Koble Corrigan, Khan and SIPS) were shown good fitness with equilibrium data, and the adsorption coefficients indicate favourable adsorption. The maximum monolayer capacities for lead(II) were 60.57 and 47.63 mg/g onto cabbage and cauliflower biosorbents, respectively, which is higher than cadmium(II) adsorption (20.57 and 21.32 mg/g). Adsorption kinetic was multi-order and steps as it is followed the pseudo-second order and Avrami model. As a low-cost adsorbent, cabbage and cauliflower biosorbents could be preferable for the removal of heavy metals from water and wastewaters.
Nur, T., Loganathan, L., Nguyen, T., Vigneswaran, S., Singh, G. & Kandasamy, J.K. 2014, 'Batch and column adsorption and desorption of fluoride using hydrous ferric oxide: Solution chemistry and modelling', Chemical Engineering Journal, vol. 247, pp. 93-102.
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Nur, T., Shim, W.G., Johir, M.A.H., Vigneswaran, S. & Kandasamy, J. 2014, 'Modelling of phosphorus removal by ion-exchange resin (Purolite FerrIX A33E) in fixed-bed column experiments', Desalination and Water Treatment, vol. 52, no. 4-6, pp. 784-790.
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Phosphorus removal is important as it causes eutrophication that in turn has a harmful effect on fish and other aquatic life, resulting in a reduction in biodiversity as well as unfavourable human environmental health. In this study, phosphorus removal from aqueous solutions was studied using an ion-exchange resin (Purolite FerrIX A33E) in fixed-bed column experiments. The effects of adsorbent bed height (319 cm) on the breakthrough characteristics of the adsorption system were studied. An increase in bed height (319 cm) increased adsorption capacity but the breakthrough time was shorter. As the bed height increased, the detention time increased and the phosphate was in contact with the purolite ion-exchange resin for a longer time, resulting in more efficient removal of phosphate. The shape of breakthrough curve was steeper for a shorter bed height. A mathematical model (advection dispersion equation) was solved numerically to predict the dynamic behaviour of the columns. Finally, sensitivity analysis results apparently revealed that the dynamic adsorption behaviours of phosphate in Purolite FerrIX A33E were mainly controlled by the external mass transfer rather than the axial dispersion and the intra-particle diffusion.
Kandasamy, J.K., Sounthararajah, D.P., Sivabalan, P., Chanan, A., Vigneswaran, S. & Sivapalan, M. 2014, 'Socio-hydrologic drivers of the pendulum swing between agricultural development and environmental health: a case study from Murrumbidgee River basin, Australia', Hydrology And Earth System Sciences, vol. 18, no. 3, pp. 1027-1041.
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Jeong, S., Rice, S. & Vigneswaran, S. 2014, 'Long-term effect on membrane fouling in a new membrane bioreactor as a pretreatment to seawater desalination', Bioresource Technology, vol. 165, pp. 60-68.
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Shrestha, A., Jeong, S., Vigneswaran, S. & Kandasamy, J.K. 2014, 'Seawater biofiltration pre-treatment system: comparison of filter media performance', Desalination and Water Treatment, vol. 52, no. 34-36.
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Biological filtration is an effective pre-treatment method to remove organic matter and particulate matter from seawater. Three biofilter columns were operated packed with granular-activated carbon (GAC), anthracite and sand as a filter media. The biofilters were run for 120 d at a slow filtration velocity of 0.12?m/h. Biofiltration performances were evaluated in terms of turbidity, different fouling indices, and dissolved organic carbon(DOC). The removal efficiencies of turbidity by the three biofilters were similar with low headloss development. The fouling potential of treated seawater (filtrate) was evaluated using three different fouling indices such as microfiltration, ultrafiltration, and microfiltration at a cross flow. The analyses of three different fouling indices showed that the reduction in fouling potential was the following order GAC?>?sand?>?anthracite. In terms of DOC removal efficiency, GAC biofilter showed higher and stable removal efficiency (4188%), than sand biofilter (776%) and anthracite biofilter (371%). All biofilters used in this study removed most of hydrophobic organic compounds (around 94%). On the other hand, hydrophilic organic removal varied depending on the media filter. GAC biofilter removed more organic biopolymers (51%), humic substances (75%) and building blocks (50%) compared with sand and anthracite biofilters. Therefore, GAC biofiltration can be used as an effective pre-treatment to alleviate organic fouling.
Hossain, M.D., Ngo, H., Guo, W., Nghiem, L.D., Hai, F.I., Vigneswaran, S. & Nguyen, V. 2014, 'Competitive adsorption of metals on cabbage waste from multi-metal solutions', Bioresource Technology, vol. 160, pp. 79-88.
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This study assessed the adsorption capacity of the agro-waste 'cabbage' as a biosorbent in single, binary, ternary and quaternary sorption systems with Cu(II), Pb(II), Zn(II) and Cd(II) ions. Dried and ground powder of cabbage waste (CW) was used for the sorption of metals ions. Carboxylic, hydroxyl, and amine groups in cabbage waste were found to be the key functional groups for metal sorption. The adsorption isotherms obtained could be well fitted to both the mono- and multi-metal models. In the competitive adsorption systems, cabbage waste adsorbed larger amount of Pb(II) than the other three metals. However, the presence of the competing ions suppressed the sorption of the target metal ions. Except the case of binary system of Cd(II)-Zn(II) and Cd(II)-Cu(II), there was a linear inverse dependency between the sorption capacities and number of different types of competitive metal ions.
Kazner, C., Jamil, S., Phuntsho, S., Shon, H., Wintgens, T. & Vigneswaran, S. 2014, 'Forward osmosis for the treatment of reverse osmosis concentrate from water reclamation: process performance and fouling control.', Water Science and Technology, vol. 69, no. 12, pp. 2431-2437.
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While high quality water reuse based on dual membrane filtration (membrane filtration or ultrafiltration, followed by reverse osmosis) is expected to be progressively applied, treatment and sustainable management of the produced reverse osmosis concentrate (ROC) are still important issues. Forward osmosis (FO) is a promising technology for maximising water recovery and further dewatering ROC so that zero liquid discharge is produced. Elevated concentrations of organic and inorganic compounds may act as potential foulants of the concentrate desalting system, in that they consist of, for example, FO and a subsequent crystallizer. The present study investigated conditions under which the FO system can serve as concentration phase with the focus on its fouling propensity using model foulants and real ROC. Bulk organics from ROC consisted mainly of humic acids (HA) and building blocks since wastewater-derived biopolymers were retained by membrane filtration or ultrafiltration. Organic fouling of the FO system by ROC-derived bulk organics was low. HA was only adsorbed moderately at about 7% of the initial concentration, causing a minor flux decline of about 2&#8211;4%. However, scaling was a major impediment to this process if not properly controlled, for instance by pH adjustment or softening
Pradhan, M., Vigneswaran, S., Ben Aim, R. & Kandasamy, J.K. 2014, 'Modelling of particle deposition in a submerged membrane microfiltration system', Desalination, vol. 350, pp. 14-20.
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Nguyen, T., Loganathan, L., Nguyen, V., Vigneswaran, S., Kandasamy, J.K., Slee, S., Gavin, S. & Naidu, R. 2014, 'Polycyclic aromatic hydrocarbons in road-deposited sediments, water sediments, and soils in Sydney, Australia: Comparisons of concentration distribution, sources and potential toxicity', Ecotoxicology And Environmental Safety, vol. 104, pp. 339-348.
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Shanmuganathan, S., Nguyen, V., Shim, W., Kandasamy, J.K. & Vigneswaran, S. 2014, 'Performance of submerged membrane - Ion exchange hybrid system with Purolite A502PS in treating reverse osmosis feed', Separation and Purification Technology, vol. 122, pp. 24-31.
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Shanmuganathan, S., Nguyen, T.V., Shim, W.G., Kandasamy, J., Listowski, A. & Vigneswaran, S. 2014, 'Effluent organic matter removal from reverse osmosis feed by granular activated carbon and purolite A502PS fluidized beds', JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY, vol. 20, no. 6, pp. 4499-4508.
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Shanmuganathan, S., Nguyen, T.V., Shim, W.G., Kandasamy, J., Listowski, A. & Vigneswaran, S. 2014, 'Effluent organic matter removal from reverse osmosis feed by granular activated carbon and purolite A502PS fluidized beds', JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY, vol. 20, no. 6, pp. 4499-4508.
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Nguyen, T.V., Jeong, S., Pham, T.T.N., Kandasamy, J. & Vigneswaran, S. 2014, 'Effect of granular activated carbon filter on the subsequent flocculation in seawater treatment', Desalination, vol. 354, pp. 9-16.
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&copy; 2014 Elsevier B.V.In this study, a granular activated carbon (GAC) filter was used to remove organics from seawater. The effect of GAC filtration on the subsequent treating of seawater by flocculation was evaluated through Jar test experiments and submerged membrane coagulation hybrid system (SMCHS). GAC filtration removed 70% of low molecular weight (LMW) neutrals and acids from seawater which helped to reduce the biofouling of membrane. GAC filtration also helped to reduce flocculant dose significantly. Relatively high doses of ferric chloride (FeCl3 3mg/L) and poly-ferric sulfate (PFS 2mg/L) were normally needed to obtain high organic removal when flocculation was used without the pretreatment of GAC filter adsorption. The use of GAC filtration prior to the application of SMCHS reduced the flocculant dosage to 1mg/L to achieve the same removal. The subsequent flocculation by different flocculants such as ferric chloride (FeCl3) and poly-ferric sulfate (PFS) was found to be able to remove biopolymers which were not effectively removed by the pretreatment (GAC filtration). The technical and cost analyses made showed that a combination of GAC filtration and flocculation with low flocculant dose can be a superior technical and economical solution for seawater pretreatment.
Loganathan, P., Vigneswaran, S., Kandasamy, J. & Bolan, N.S. 2014, 'Removal and Recovery of Phosphate From Water Using Sorption', CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY, vol. 44, no. 8, pp. 847-907.
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Nguyen, T.V., Loganathan, P., Vigneswaran, S., Krupanidhi, S., Pham, T.T.N. & Ngo, H.-.H. 2014, 'Arsenic waste from water treatment systems: characteristics, treatments and its disposal', Water Science and Technology-Water Supply, vol. 14, no. 6, pp. 939-950.
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Naidu, G., Jeong, S., Choi, Y., Jang, E., Hwang, T.M. & Vigneswaran, S. 2014, 'Application of vacuum membrane distillation for small scale drinking water production', Desalination, vol. 354, pp. 53-61.
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&copy; 2014 Elsevier B.V.This study evaluated the applicability of a modified design vacuum enhanced-multi effect membrane distillation (V-MEMD) for drinking water production with feed solution containing NaCl and CaSO4. The applicability was studied in terms of flux, scale formation and ease of cleaning. A slight flux decline (18-20%) was observed with loosely deposited crystals in the membrane module during the 920min of the operation. Larger formation of crystal (volume weighted mean size, D[4,3]) was observed in the final feed brine (D[4,3]brine feed=455.96m) compared to that inside the module (D[4,3]brine module=62.68m). The loose crystal deposition was attributed to the absence of hydraulic pressure, low feed temperature, high turbulence (Re=5665.6) and short membrane retention time (21.6s). The crystal formation in the membrane module, D[4,3]brine module increased with reduced permeate side vacuum and lower feed velocity. Periodic DI water flushing was found to be efficient to remove the scaling. The feed component mass balance showed that most of the components were able to be removed with 2L DI water flushing. A 70% recovery ratio was projected for a scaled-up unit, highlighting the suitability of the V-MEMD as a small scale system for drinking water production.
van Emmerik, T.H.M., Li, Z., Sivapalan, M., Pande, S., Kandasamy, J., Savenije, H.H.G., Chanan, A. & Vigneswaran, S. 2014, 'Socio-hydrologic modeling to understand and mediate the competition for water between agriculture development and environmental health: Murrumbidgee River basin, Australia', Hydrology and Earth System Sciences, vol. 18, no. 10, pp. 4239-4259.
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Vigneswaran, S., Leelemani, A. & Divya, K. 2014, 'A video synchronization approach for coherent key-frame extraction and object segmentation', Journal of Theoretical and Applied Information Technology, vol. 68, no. 2, pp. 331-338.
&copy; 2005 - 2014 JATIT & LLS. All rights reserved.In this paper we discuss a new video frame synchronization approach for coherent key-frame extraction and object segmentation. As two basic units for content-based video analysis, key-frame extraction and object segmentation are usually implemented independently and separately based on different feature sets. Our previous work showed that by exploiting the inherent relationship between key-frames and objects, a set of salient key-frames can be extracted to support robust and efficient object segmentation. This work furthers the previous numerical studies by suggesting a new analytical approach to jointly formulate key-frame extraction and object segmentation via a statistical mixture model where the concept of frame/pixel saliency which is introduced and also this deals with the relationship between the frames. A modified Expectation Maximization algorithm is developed for model estimation that leads to the most salient key-frames for object segmentation. Simulations on both synthetic and real videos show the effectiveness and efficiency of the proposed method.
Loganathan, L., Vigneswaran, S., Kandasamy, J.K. & Naidu, R. 2013, 'Defluoridation of drinking water using adsorption processes', Journal of Hazardous Materials, vol. 248-249, pp. 1-19.
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Excessive intake of fluoride (F), mainly through drinking water, is a serious health hazard affecting humans worldwide. There are several methods used for the defluoridation of drinking water, of which adsorption processes are generally considered attractive because of their effectiveness, convenience, ease of operation, simplicity of design, and for economic and environmental reasons. In this paper, we present a comprehensive and a critical literature review on various adsorbents used for defluoridation, their relative effectiveness, mechanisms and thermodynamics of adsorption, and suggestions are made on choice of adsorbents for various circumstances. Effects of pH, temperature, kinetics and co-existing anions on F adsorption are also reviewed. Because the adsorption is very weak in extremely low or high pHs, depending on the adsorbent, acids or alkalis are used to desorb F and regenerate the adsorbents. However, adsorption capacity generally decreases with repeated use of the regenerated adsorbent. Future research needs to explore highly efficient, low cost adsorbents that can be easily regenerated for reuse over several cycles of operations without significant loss of adsorptive capacity and which have good hydraulic conductivity to prevent filter clogging during the fixed-bed treatment process.
Loganathan, L., Vigneswaran, S. & Kandasamy, J.K. 2013, 'Road-deposited sediment pollutants: A critical review of their characteristics, source apportionment, and management', Critical Reviews in Environmental Science and Technology, vol. 43, no. 13, pp. 1315-1348.
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Road-deposited sediments (RDS) often contain elevated concentrations of inorganic and organic pollutants such as heavy metals, metalloids, and polycyclic aromatic hydrocarbons. The authors trace new developments and trends on RDS pollutant characteristics with respect to their distribution in time and space, total and labile fractions in the different particle size and density fractions, source apportionment, and chemical speciation, as well as on the management of the pollutants. Recent research provides more reliable information to understand pollutants origin, bioavailability, transport pathways, and methods to minimize their risks. Use of special chemical, physical, mineralogical, and statistical methods has contributed to a better understanding of source apportionment of many of the pollutants but more research is needed on others. The degree of accumulation of pollutants in RDS that are derived from roads and vehicles has been quantified by using enrichment factors. Many of the studies on RDS pollutant management dealt with reducing pollutants by road sweeping and water flushing but these have not been found to be very effective. Pollutants that enter the water bodies through stormwater runoff need to be removed to protect the aquatic environment in the receiving water. The current knowledge on stormwater treatment methods to remove pollutants is also presented.
Jeong, S., Kim, S., Kim, C.M., Vigneswaran, S., Nguyen, V., Shon, H., Kandasamy, J.K. & Kim, I.S. 2013, 'A detailed organic matter characterization of pretreated seawater using low-pressure microfiltration hybrid systems', Journal Of Membrane Science, vol. 428, pp. 290-300.
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In this study, two different submerged membrane hybrid systems (SMHSs) namely (i) submerged membrane coagulation hybrid system (SMCHS) and (ii) submerged membrane coagulation-adsorption hybrid system (SMCAHS) were investigated as pretreatment options for seawater reverse osmosis. Organic matters in seawater before and after pretreatment were characterized in terms of XAD fractionation, molecular weight distribution (MWD) and fluorescence. A detailed study on the seawater organic matter (SWOM) structure was made through 1H-nuclear magnetic resonance (1H NMR), pyrolysis-gas chromatography&acirc;mass spectrometry (Py-GC/MS) and liquid chromatography-mass spectrometry-ion trap-time of fright (LC/MS-IT-TOF). The seawater investigated in this study is mainly composed of hydrophilic matter (5773.2%). SMHSs removed a significant amount of organic matter. The EEM fluorescence showed a removal of humic-like materials by SMHSs. In addition, humic-like materials relative to protein-like compounds were reduced significantly but the aromaticity of humic-like materials increased. After pretreatment by SMHSs, humics and biopolymers of over 900 Da. were found to be reduced and their structure associated with element composition was also changed. The transformation of the SWOM structure after SMHSs pretreatment may have been due to hydrolyzation or oxidization of the organic compounds such as humics and biopolymers resulting in poly-conjugation to aromatic compounds. SMHSs were effective in improving the RO performance leading to higher RO permeate flux and lower permeate flux decline. The pretreatment reduced the amount of foulants on the RO membrane.
Jeong, S., Danasamy, G., Vigneswaran, S., Ma, C.H. & Rice, S.A. 2013, 'A rapid bioluminescence-based test of assimilable organic carbon for seawater', Desalination, vol. 317, pp. 160-165.
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The accumulation of biological materials and bacteria on water purification membranes, termed biofouling, is associated with decreased membrane performance and increased cost of operation. One strategy to minimize biofouling is pretreatment of the influent water. In this regard, tools and indicators that can assess the influent water are required, enabling an optimum selection of pretreatment methods. One parameter directly linked to biofouling potential is the concentration of assimilable organic carbon (AOC) in the feed-water. High AOC levels are associated with increased growth potential of the microbial fouling community. This work focused on the development of a new method for rapid and accurate quantification of AOC concentration in seawater. The method is based on the quantification of the bioluminescence response of the marine bacterium Vibrio fischeri MJ-1. Compared to previous methods, this new V. fischeri method was rapid (within 1 h), sensitive (detection limit = 0.1 &micro;g-C glucose equivalents/L) and highly suitable for seawater samples. V. fischeri method was evaluated using real seawater samples. The results showed positive reproductive AOC values. The new V. fischeri AOC method developed has a highly promising potential to be practically adopted as a rapid indicator of AOC concentration and hence biofouling potential of influent marine water.
Jeong, S. & Vigneswaran, S. 2013, 'Assessment of biological activity in contact flocculation filtration used as a pretreatment in seawater desalination', Chemical Engineering Journal, vol. 228, no. 1, pp. 976-983.
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Contact flocculation filtration (CFF) is a promising pretreatment method to improve feed water quality prior to seawater reverse osmosis (SWRO). CFF is the combination of deep bed filtration and in-line flocculation. To date, CFF has been used mainly as a barrier for particle removal in the filter bed itself with hydrophobic organic compounds removal by flocculation. In this study, the potential of CFF was investigated as a biofilter in addition to its major function of flocculation and particle/floc separation. Two different media (sand; S-CFF and anthracite; A-CFF) were tested on CFF. Bacterial activity in the filter bed was assessed in terms of cell number and adenosine tri-phosphate (ATP) measurement. The microbial community test in the filtration bed was carried out over 50 d in case of sand filter (S-CFF) and 90 d for anthracite filter (A-CFF) filtration periods. With the growth of an active microbial population on the filter bed medium, significant removal of organic compounds, especially low molecular weight (LMW) organics, from the seawater was achieved. The results indicated that CFF functions both as flocculation and separation unit and also as biofilter with moderate efficiency in reducing biofouling potential. The results also showed that A-CFF needed longer time to achieve bio-stabilization but it showed more effective biofiltration potential than S-CFF.
Jeong, S., Danasamy, G. & Vigneswaran, S. 2013, 'Submerged membrane adsorption bioreactor as a pretreatment in seawater desalination for biofouling control', Bioresource Technology, vol. 141, no. 1, pp. 57-64.
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Submerged membrane adsorption bioreactor (SMABR) was investigated as a pretreatment to reverse osmosis (RO). SMABR removed organic matter by adsorption and biological degradation. At a powder activated carbon (PAC) residence time of 66 d (1.5% of PAC replacement daily), higher organic removal was achieved with removal of a majority of biopolymers (9497%) and humics (7176%). A continuous MBR operation with the optimal PAC residence time of 66 d was conducted and compared with MBR with no PAC replenishment in terms of the removal of organic and microbes. High removal of organics of up to 72% was maintained with only a marginal increment of trans-membrane pressure and stable bioactivity (total cell number and adenosine tri-phosphate) during the 50 d of operation. The SMABR was found to be a sustainable biological pretreatment to RO with only a small amount of PAC requirement (2.14 g of PAC/m3 of seawater treated).
Jeong, S., Okour, Y., Nguyen, T., Shon, H. & Vigneswaran, S. 2013, 'Ti-salt flocculation for dissolved organic matter removal in seawater', Desalination and Water Treatment, vol. 51, no. 16-18, pp. 3591-3596.
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In this study, the removal of different fractions of organic matter in seawater was investigated using titanium tetrachloride (TiCl4) flocculation and compared with ferric chloride (FeCl3) flocculation. The organic matter fractions were characterised using liquid chromatographyorganic carbon detector (LCOCD). Results showed the hydrophobic compounds removal was dominant by both flocculants. However, the removal of hydrophilic organic compounds, such as humics and low-molecular weight neutral compounds of seawater, was superior by TiCl4 flocculation compared to FeCl3 flocculation and this removal increased considerably with the increase of TiCl4 doses. The flocculated sludge after TiCl4 flocculation was incinerated to produce titanium dioxide (TiO2) nanoparticle. TiO2 from seawater sludge characterised by X-ray diffraction (XRD) and scanning electron microscope/energy-dispersive X-ray spectroscopy (SEM/EDS) showed predominant anatase phase with Si as a main dopant.
Loganathan, L., Vigneswaran, S. & Kandasamy, J.K. 2013, 'Enhanced removal of nitrate from water using surface modification of adsorbents - A review', Journal of Environmental Management, vol. 131, no. 1, pp. 363-374.
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Elevated concentration of nitrate results in eutrophication of natural water bodies affecting the aquatic environment and reduces the quality of drinking water. This in turn causes harm to peoples health, especially that of infants and livestock. Adsorbents with the high capacity to selectively adsorb nitrate are required to effectively remove nitrate from water. Surface modifications of adsorbents have been reported to enhance their adsorption of nitrate. The major techniques of surface modification are: protonation, impregnation of metals and metal oxides, grafting of amine groups, organic compounds including surfactant coating of aluminosilicate minerals, and heat treatment. This paper reviews current information on these techniques, compares the enhanced nitrate adsorption capacities achieved by the modifications, and the mechanisms of adsorption, and presents advantages and drawbacks of the techniques. Most studies on this subject have been conducted in batch experiments. These studies need to include continuous mode column trials which have more relevance to real operating systems and pilot-plant trials. Reusability of adsorbents is important for economic reasons and practical treatment applications. However, only limited information is available on the regeneration of surface modified adsorbents.
Jeong, S., Kim, S., Kim, L.H., Shin, M.S., Vigneswaran, S., Nguyen, V. & Kim, I.S. 2013, 'Foulant analysis of a reverse osmosis membrane used pretreated seawater', Journal Of Membrane Science, vol. 428, pp. 434-444.
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This study focused on the characterization of organic and biological foulants on reverse osmosis (RO) membrane and fouled RO membrane characterization with seawater pretreated by submerged membrane hybrid systems (SMHSs). New low pressure membrane based pretreatments namely submerged membrane coagulation hybrid system (SMCHS) and submerged membrane coagulation-adsorption hybrid system (SMCAHS) were investigated. Organic foulants on RO membrane were characterized in terms of molecular weight distribution (MWD), fluorescence and extracellular polymeric substance (EPS) analyses. The organic foulants were mainly composed of high molecular weight matters representing biopolymers in the foulants. The fluorescence excitation&acirc;emission matrix (F-EEM) analysis showed that protein-like materials were dominant with samples pretreated by SMHSs. Humic-like materials which have lower aromaticity were also present in the foulant. Biological foulants were investigated in terms of total direct cell (TDC) count, cell viability and biomass activity (adenosine tri-phosphate; ATP). Biological fouling was found to be reduced by organic removal with SMHSs. The fouled membranes were characterized using environmental scanning electron microscopy coupled with energy dispersive spectroscopy, attenuated total reflection-Fourier transform infrared spectrometry, zeta-potential measurement, atomic force microscopy, and contact angle measurement.
Johir, J., Vigneswaran, S., Kandasamy, J.K. & Sleigh, R. 2013, 'Coupling Of Physico-chemical Treatment And Steel Membrane Filtration To Enhanced Organic Removal In Wastewater Treatment', Desalination And Water Treatment, vol. 51, no. 13-15, pp. 2695-2701.
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In this study, the application of steel membrane filtration was tested with the pre-treated wastewater. The pre-treatment methods tested before membrane filtration application were flocculation using FeCl3, Powdered Activated Carbon (PAC) adsorption, purolite ion-exchange column and purolite ion-exchange column followed by flocculation (FeCl3). The effect of two different modes of membrane application (cross-flow and dead-end modes) was examined. The ability of these filters in removing organic matters and solids were examined. It was found that the decline of flux was slightly lower for dead-end mode of operation to that of cross-flow mode of operation. Pre-treatment increased the performance of membrane filtration. The flux decline of raw water (without pre-treatment) was 31-10%, whereas after pre-treatment, it was about 2.5-21%. Pre-treatment followed by microfiltration (MF) showed 68-91% removal efficiency of dissolved organic carbon
Shon, H., Phuntsho, S., Chaudhary, D.S., Vigneswaran, S. & Cho, J. 2013, 'Nanofiltration for water and wastewater treatment - a mini review', Drinking Water Engineering and Science, vol. 6, no. 1, pp. 47-53.
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The application of membrane technology in water and wastewater treatment is increasing due to stringent water quality standards. Nanofiltration (NF) is one of the widely used membrane processes for water and wastewater treatment in addition to other applications such as desalination. NF has replaced reverse osmosis (RO) membranes in many applications due to lower energy consumption and higher flux rates. This paper briefly reviews the application of NF for water and wastewater treatment including fundamentals, mechanisms, fouling challenges and their controls.
Johir, J., Vigneswaran, S., Kandasamy, J.K., Benaim, R. & Grasmick, A. 2013, 'Effect of salt concentration on membrane bioreactor (MBR) performances: Detailed organic characterization', Desalination, vol. 322, no. 1, pp. 13-20.
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The gradual increase of salt concentration (0 to 35 g-NaCl/L) on the performance of membrane bioreactor (MBR) was studied. The uptake rate of dissolved organic carbon and ammonia decreased from around 17.0 mg-DOC/g-MLVSS.d to 1.8 mg-DOC/g-MLVSS.d and from 8.2 mg-NH4-N/g-MLVSS.d to 0 mg-NH4-N/g-MLVSS.d respectively when salt concentration reached to 35 g-NaCl/L. Similarly the specific oxygen uptake rate (SOUR) reduced from 8 to 9 to around 0.3 mg-O2/g-MLVSS.h. The removal of bio-polymers, humic acids, building blocks and low molecular weight neutral decreased with increase in salt concentration. The concentration of dissolved organic nitrogen (DON) in bio-polymer increased from 0.05 to 3.31 mg/L when the salt concentration reached to 35 g-NaCl/L. This study provides good information for understanding the effect of continuous increase of salt concentration in treating saline wastewater in a MBR process.
Johir, J., Shanmuganathan, S., Vigneswaran, S. & Kandasamy, J.K. 2013, 'Performance of submerged membrane bioreactor (SMBR) with and without the addition of the different particle sizes of GAC as suspended medium', Bioresource Technology, vol. 141, no. NA, pp. 13-18.
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In this study the effect of different particle sizes of granular activated carbon (GAC) on the performance of a submerged membrane bioreactor (SMBR) was investigated. The sizes of GAC used were 150300, 300600 and 6001200 &micro;m. The SMBR was operated at a filtration flux of 20 L/m2 h. The removal of dissolved organic carbon (DOC) and chemical oxygen demand (COD) with the addition of GAC was 95%. The concentration of biopolymers, humic, building block and low molecular weight neutral and acids in the SMBR effluent was reduced by 20%, 6676%, 2050%, 3056%, respectively. It helped to reduce the sludge volume index (SVI) and transmembrane pressure (TMP) development by 3040% and 58%, respectively. However, the removal of View the MathML source and View the MathML source was relatively low of 3545% and 3443%, respectively. The SMBR effluent was rich in View the MathML source and was removed/recovered using hydrated ferric oxide (HFO). The removal of View the MathML source was almost 90%.
Kus, B.G., Kandasamy, J.K., Vigneswaran, S., Shon, H. & Moody, G. 2013, 'Gravity driven membrane filtration system to improve the water quality in rainwater tanks', Water Science & Technology: Water Supply, vol. 13, no. 2, pp. 479-485.
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The characterisation of rainwater in metropolitan Sydney and in rural New South Wales was undertaken. The results showed that factors such as the lack of vehicular traffic, air pollution and urban contamination meant that rural rainwater water quality was better. The rain water collected in both metropolitan and rural areas generally complied with the 2004 Australian Drinking Water Guidelines except for parameters such as the pH in both the metropolitan and rural rainwater tanks and the turbidity, and lead levels from the metropolitan tanks. This paper also reports the results of a laboratory and a pilot scale study with a deep bed filter (granular activated carbon, GAC) and microfiltration (MF) hollow fibre membrane filter system used to treat raw rainwater collected from a metropolitan rainwater tank. The results of the laboratory experiment and pilot scale systems focus on the non-compliant parameters of the sampling program, i.e. turbidity, lead and dissolved organic carbon (DOC). It was found that rainwater treated by the GAC filter removed the majority of the turbidity and organic substances. The treatment system reduced the concentration of turbidity, lead and DOC to below the Australian Drinking Water Guidelines limits. The pilot plant experiment demonstrated that a GAC filter system and gravity driven membrane could result in low cost and low maintenance operation.
Danasamy, G., Jeong, S., Vigneswaran, S. & Rice, S.A. 2013, 'Microbial activity in biofilter used as a pretreatment for seawater desalination', Desalination, vol. 309, no. NA, pp. 254-260.
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Biofilters as a pretreatment process in seawater desalination can reduce biofoulants through adsorption and biodegradation. In this study, the performance of granular activated carbon (GAC) biofilter with three different filtration velocities was studied in terms of dissolved organic carbon (DOC) removal. This apart, the microbial activities in the biofilters were measured in terms of concentration of active biomass (adenosine tri-phosphate; ATP) and total cell count. Biofouling potential in biofilter effluents were assessed in terms of transparent exopolymer particles (TEP) and assimilable organic carbon (AOC) concentration. AOC was carried out using a new rapid bioluminescence method. Upon reaching mature stage, the GAC biofilters achieved high DOC removal efficiency of more than 60%, especially the low molecular weight organics. This organic removal was mostly attributed to active biomass on the GAC media. In addition, GAC biofilters led to significant reduction of the AOC and TEP concentration amounting to only 0.6 &plusmn; 0.2 &micro;g-C glucose/L and 5.3 &plusmn; 1.1 &micro;g-C/L, respectively in effluents. Thus, GAC biofilter is an effective pretreatment in reducing biofouling potential
Jeong, S., Bae, H., Danasamy, G., Jeong, D., Lee, S. & Vigneswaran, S. 2013, 'Bacterial community structure in a biofilter used as a pretreatment for seawater desalination', Ecological Engineering, vol. 60, no. 1, pp. 370-381.
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In this study, two biofilters with different media, anthracite and granular activated carbon (GAC), were used to pre-treat seawater for desalination. Both biofilters had the same operating conditions that lasted for 75 days. The bacterial community struc
Aryal, R., Beecham, S.C., Vigneswaran, S., Kandasamy, J.K. & Naidu, R. 2013, 'Spatial variation of polycyclic aromatic hydrocarbons and equivalent toxicity in Sydney Harbour, Australia', Journal of Water and Climate Change, vol. 4, no. 4, pp. 364-372.
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Harbour sediments include wash-off from different nearby catchments that have various landuse activities. In this study the spatial variation of polycyclic aromatic hydrocarbons (PAHs) in Sydney Harbour was studied by analysing the sediment. The sediment
Chanan, A.P., Vigneswaran, S., Kandasamy, J.K. & Johir, J. 2013, 'Need for a fresh look at phosphorus management in wastewater treatment: Trash to treasure', Sustainable Environment Research (SER), vol. 23, no. 1, pp. 23-31.
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Eutrophication of water bodies is a major, global environmental problem. It is now well understood that its main cause is excessive amounts of nutrients such as phosphorus. Stringent laws were therefore introduced across the world, requiring that the level of the P be significantly reduced. Consequently, the focus for wastewater treatment industry became the elimination of phosphorus in effluent stream. Treatment technologies capable of removing over 90% of phosphorus from wastewater have now been developed. However, these phosphorus removal options are likely to be ineffective in the future. The future would call for a shift to the primary goal of phosphorus removal to 'capturing and reusing' phosphorus. This paper calls for a re-think in developing phosphorus management programs. Discussing Fertigation as step-one in phosphorus reclamation, the paper will further elaborate phosphorus recovery opportunities such as ion-exchange that can be retrofitted to existing wastewater treatment plants.
Kus, B.G., Kandasamy, J.K., Vigneswaran, S., Shon, H. & Moody, G. 2013, 'Household rainwater harvesting system - Pilot scale gravity driven membrane-based filtration system', Water Science & Technology: Water Supply, vol. 13, no. 3, pp. 790-797.
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This paper presents the results of a pilot scale study consisting of pre-treatment with a granular activated carbon (GAC) filter followed by membrane filtration. Detailed characterisation of rainwater tanks has highlighted that turbidity, dissolved organic carbon (DOC) and heavy metals, in particular lead, were not compliant with the 2004 Australian Drinking Water Guidelines (ADWG). Further, organic matter present in the water causes membrane fouling and leads to carcinogenic compounds upon chlorination. A GAC filter was used as a first step to remove dissolved organic matter (measured in terms of DOC) in particular and also to reduce the concentration, of turbidity and lead. Membrane filtration can remove any remaining solids reducing the concentrations of turbidity and microorganisms. In this study a pilot scale rainwater treatment system consisting of a gravity fed GAC filter and membrane filter (Ultra Flo) was operated for a period of 120 days. The performance of this system was assessed in terms of membrane flux and improvement in water quality measured against the 2004 Australian Drinking Water Guidelines. Determination of the flux especially in the later stages of membrane operation was important to be able to size the filters in a manner that meets the expected demand. The treatment system of GAC filter and membrane filter was effective in reducing the turbidity, DOC and heavy metals. The system reduced the turbidity to levels of 0.30.4 NTU, below the ADWG limit of 1 NTU.
Hong, S., Aryal, R., Vigneswaran, S., Johir, M.H. & Kandasamy, J.K. 2012, 'Influence of hydraulic retention time on the nature of foulant organics in a high rate membrane bioreactor', Desalination, vol. 287, no. 1, pp. 116-122.
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The influence of hydraulic retention time (HRT) in a submerged hollow fibre membrane bioreactor was studied by conducting experiments at four different HRTs (4,2, 1.3 and 1 h) at room temperature of 25 &Acirc;&deg;C. lt was found that a shorter HRT led to a higher development of trans-membrane pressure. The highest sludge cake and pore-blocking resistances of 4.02 x 1011 m-1 and 0.77 x 1011 m-1 respectively were noted for the shortest HRT (of 1 h) application. UV and fluorescence spectroscopy analyses showed that the nature of organics in the biomass and sludge cakes were different. The organic fraction analysis by liquid chromatography with organic carbon detector (LC-OCO) showed a significant amount of biopolymers and a lower amount of humics for longer HRT.
Mohammed Abdul, J., Colville, A.E., Lim, R.P., Vigneswaran, S. & Kandasamy, J.K. 2012, 'Use of duckweed (Lemna disperma) to assess the phytotoxicity of the products of Fenton oxidation of metsulfuron methyl', Ecotoxicology And Environmental Safety, vol. 83, pp. 89-95.
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Because of pressure on water supplies world-wide, there is increasing interest in methods of remediating contaminated ground waters. However, with some remediation processes, the breakdown products are more toxic than the original contaminant. Organic matter and salinity may also influence degradation efficiency. This study tested the efficiency of Fenton oxidation in degrading the sulfonylurea herbicide metsulfuron methyl (MeS), and tested the reaction products for phytotoxicity with the Lemna (duckweed) bioassay. The efficiency of degradation by Fenton&acirc;s reagent (Fe2&Atilde;&frac34; &Acirc;&frac14;0.09 mM; H2O2&Acirc;&frac14;1.76mM, 4 h) decreased with increasing initial MeS concentration, from 98% with 5 mg/L MeS, to 63% with 70 mg/L MeS. Addition of NaCl (10 mM) and organic matter (humic acid at 0.2 and 2.0 mg C/L as Total Organic Carbon) reduced the efficiency of degradation at low initial MeS concentrations (5 and 10mg/L), but had no effect at high concentrations. The residual Fenton&acirc;s reagent after Fenton&acirc;s oxidation was toxic to Lemna. After removal of residual iron and H2O2, the measured toxicity to Lemna in the treated samples could be explained by the concentrations of MeS as measured by HPLC/UV detection, so there was no evidence of additional toxicity or amelioration due to the by-products or formulation materials.
Phuntsho, S., Shon, H., Majeed, T., El Saliby, I., Vigneswaran, S., Kandasamy, J.K., Hong, S. & Lee, S. 2012, 'Blended Fertilizers as Draw Solutions for Fertilizer-Drawn Forward Osmosis Desalination', Environmental Science & Technology, vol. 46, pp. 4567-4575.
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In fertilizer-drawn forward osmosis (FDFO) desalination, the final nutrient concentration (nitrogen, phosphorus, potassium (NPK)) in the product water is essential for direct fertigation and to avoid over fertilization. Our study with 11 selected fertilizers indicate that blending of two or more single fertilizers as draw solution (DS) can achieve significantly lower nutrient concentration in the FDFO product water rather than using single fertilizer alone. For example, blending KCl and NH4H2PO4 as DS can result in 0.61/1.35/1.70 g/L of N/P/K, which is comparatively lower than using them individually as DS. The nutrient composition and concentration in the final FDFO product water can also be adjusted by selecting low nutrient fertilizers containing complementary nutrients and in different ratios to produce prescription mixtures. However, blending fertilizers generally resulted in slightly reduced bulk osmotic pressure and water flux in comparison to the sum of the osmotic pressures and water fluxes of the two individual DSs as used alone. The performance ratio or PR (ratio of actual water flux to theoretical water flux) of blended fertilizer DS was observed to be between the PR of the two fertilizer solutions tested individually. In some cases, such as urea, blending also resulted in significant reduction in N nutrient loss by reverse diffusion in presence of other fertilizer species.
Phuntsho, S., Shon, H., Hong, S., Lee, S., Vigneswaran, S. & Kandasamy, J.K. 2012, 'Fertiliser drawn forward osmosis desalination: the concept, performance and limitations for fertigation', Reviews in Environmental Science and Biotechnology, vol. 11, no. 2, pp. 147-168.
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With the world's population growing rapidly, pressure is increasing on the limited fresh water resources. Membrane technology could play a vital role in solving the water scarcity issues through alternative sources such as saline water sources and wastewater reclamation. The current generation of membrane technologies, particularly reverse osmosis (RO), has significantly improved in performance. However, RO desalination is still energy intensive and any effort to improve energy efficiency increases total cost of the product water. Since energy, environment and climate change issues are all inter-related, desalination for large-scale irrigation requires new novel technologies that address the energy issues. Forward osmosis (FO) is an emerging membrane technology. However, FO desalination for potable water is still a challenge because, recovery and regeneration of draw solutes require additional processes and energy. This article focuses on the application of FO desalination for non-potable irrigation where maximum water is required. In this concept of fertiliser drawn FO (FDFO) desalination, fertilisers are used as draw solutions (DS). The diluted draw solution after desalination can be directly applied for fertigation without the need for recovery and regeneration of DS. FDFO desalination can make irrigation water available at comparatively lower energy than the current desalination technologies. As a low energy technology, FDFO can be easily powered by renewable energy sources and therefore suitable for inland and remote applications. This article outlines the concept of FDFO desalination and critically evaluates the scope and limitations of this technology for fertigation, including suggestions on options to overcome some of these limitations
Heran, M., Aryal, R., Shon, H., Vigneswaran, S., Elmaleh, S. & Grasmick, A. 2012, 'How To Optimize Hollow-Fiber Submerged Membrane Bioreactors', Water Environment Research, vol. 84, no. 2, pp. 115-119.
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Membrane fouling is linked to reversible or irreversible accumulation of macromolecules and solids on membrane surfaces and to the irreversible adsorption inside pores. If reversible accumulation can be controlled by filtering in subcritical conditions, then adsorption could also be minimized by reducing the soluble organic matter [extracellular polymeric substances, soluble microbial products (SMP)]. This research shows how the choice of operating parameters related to biological reaction (solid retention time and the organic loading rate) can influence the process rate and the by-product (SMP) production. It also illustrates how suspension characteristics and membrane aeration can influence membrane fouling control according to the hollow fiber configuration and to the different scales of observation. The investigations were based on the definition of different fouling level and fine-tuning of a model to better understand the effects of operating parameters on membrane bioreactor filtration.
Johir, M.H., Vigneswaran, S., Sathasivan, A.S., Kandasamy, J.K. & Chang, C. 2012, 'Effect Of Organic Loading Rate On Organic Matter And Foulant Characteristics In Membrane Bio-Reactor', Bioresource Technology, vol. 113, pp. 154-160.
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In this study, the influence of organic loading rate (OLR) on the performance of a membrane bio-reactor (MBR) was investigated. The MBR was operated with 6 different OLRs between 0.5 and 3.0 kg COD/m3 d. The hydrodynamic parameters of the MBR were kept constant. The hydraulic retention time and sludge retention time were kept at 8 h and 40 d respectively. From the experimental investigation, it was found that the removal efficiency of DOC, COD and NH4-N decreased when OLRs were increased from 0.5 to 3.0 kg COD/m3 d. Higher OLRs of 2.75-3.0 kg COD/m3 d resulted in a higher transmembrane pressure development. The fractionation of organic matters showed more hydrophilic substances with higher OLRs. A detailed organic matter characterization of membrane foulant, soluble microbial product and extracellular polymeric substances showed that bio-polymers type substances together with humic acid and lower molecular neutral and acids were responsible for membrane fouling.
Jeong, S., Nguyen, V., Shon, H. & Vigneswaran, S. 2012, 'The Performance Of Contact Flocculation-Filtration As Pretreatment Of Seawater Reverse Osmosis', Desalination and Water Treatment, vol. 43, no. 1-3, pp. 246-252.
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Deep bed filtration has traditionally been used as a pretreatment in seawater desalination. The performance of contact flocculation&acirc;filtration (CFF) as pretreatment of seawater reverse osmosis (SWRO) was evaluated in terms of pressure drop through the filter and removal of organics and turbidity. The average turbidity, total suspended solids, and dissolved organic carbon (DOC) of raw seawater were 0.92 NTU, 3.6, and 1.12mg/L, respectively. The performances of CFF were experimentally evaluated with different flocculant doses (0.5&acirc;3.0mg Fe3+/L) and rapid mixing times (1.7&acirc;14.4 s). Here rapid mixing was performed in a spiral flocculation unit which consisted of a PVC tube of length 0.5m and internal diameters of 0.16 and 0.40 cm. The experimental results show that the filtration rate of 10.0m/h led to an extensive increase in both head loss (pressure drop) and turbidity as compared to those at filtration rates of 5.0 and 7.5 m/h. The head loss also significantly decreased when the flocculant dose was reduced from 3 to 0.5mg Fe3+/L. However, the organic matter (26% of DOC) removal was lower at a lower dose of ferric chloride (1.0 mg/L as Fe3+). The removal efficiency of DOC at low concentration of ferric was improved considerably through the improvement of rapid mixing. The application of CFF process also led to a significant decrease in ultrafiltermodified fouling index (UF-MFI).
Aryal, R., Johir, M.H., Vigneswaran, S., Kandasamy, J.K. & Sleigh, R. 2012, 'Performance Of A Stainless Steel Membrane In Membrane Bioreactor Process', Desalination and Water Treatment, vol. 41, no. 1-3, pp. 258-264.
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Stainless steel membrane has recently emerged as a durable membrane for microfiltration. An aerobic membrane bioreactor (MBR) equipped with a tubular stainless steel membrane of pore size 0.3&acirc;&Icirc;&frac14;m was submerged in a wastewater reactor to treat municipal wastewater of about 1,000&acirc;mg/L COD. The membrane operational performance was tested at three different permeate flux (7.5, 10 and 15&acirc;L/m2&acirc;h [LMH]) for 2 days each. In all cases, the rate of transmembrane pressure (TMP) rise was very high at 30, 45 and 80&acirc;kPa for 7.5, 10 and 15&acirc;LMH, respectively. Different analytical techniques i.e. particle size distribution, UV spectrometry, fluorescent spectrometry and size exclusion chromatography were used to study the nature of mixed liquor and the fouling deposited on the membrane surface. Rapid rise of TMP and decrease in permeate flux was observed during the experiment. Analysis of the fouling indicated a negligible difference in nature of organics between it and the mixed liquor. Filtration flux test showed a high sludge cake and pore-blocking resistance of 4.4&acirc;&Atilde;&acirc;1019 and 2.8&acirc;&Atilde;&acirc;1016&acirc;m&acirc;1, respectively, compared to a clean membrane resistance 5.4&acirc;&Atilde;&acirc;1012&acirc;m&acirc;1. The similar nature of organics in the mixed liquor and the foulant and recovery of flux after removal of the foulant after gentle washing in water, indicated a rapid sludge accumulation rather than the irreversible fouling.
Kus, B.G., Johir, M.H., Kandasamy, J.K., Vigneswaran, S., Shon, H., Sleigh, R. & Moody, G. 2012, 'Performance Of Granular Medium Filtration And Membrane Filtration In Treating Stormwater For Harvesting And Reuse', Desalination and Water Treatment, vol. 45, no. 1-3, pp. 120-127.
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This paper discusses laboratory scale and pilot scale treatment systems used to in treat water from a stormwater canal in Carlton, Sydney. The laboratory scale pre-treatment systems investigated included flocculation, GAC filtration and fibre filter prior to laboratory scale steriflow stainless steel membrane filter. The results showed that these pre-treatments improved the quality of the filtrate as measured by the turbidity and TOC removal effi ciency. The use of pre-treatment improved the TOC removal efficiency from 10% to 90%. Among the three pretreatment methods, GAC filter resulted in the highest TOC removal efficiency (88%). Pilot scale experiments were also carried out using stainless steel membrane filtration and GAC filtration at Carlton, Sydney. Pilot scale experiments showed that the Steri-Flow membrane filter treatment without any pre-treatment achieved an effluent fi ltrate turbidity of between 0.79&acirc;0.99 NTU which were well below the 5 NTU ADWG (2004) limit [1]. The influent raw stormwater had generally low concentrations of heavy metals. Following membrane filtration the concentration of all heavy metals were reduced to very low levels and well within the ADWG (2004) [1] limits. The membrane fi lter could not remove TOC in significant amounts. GAC adsorption used as post-treatment following Steri-flow membrane treatment effectively reduced the TOC influent feed levels. GAC filtration of stormwater provided a 70% removal of organics. It removed all types of organic. The GAC filter did not provide any further improvement to the turbidity level or heavy metal concentration following treatment with the Steri-flow membrane system.
Aryal, A., Sathasivan, A.S. & Vigneswaran, S. 2012, 'Synergistic Effect Of Biological Activated Carbon And Enhanced Coagulation In Secondary Wastewater Effluent Treatment', Water Science And Technology, vol. 65, no. 2, pp. 332-339.
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The use of secondary wastewater effluent (SWWE) is an essential strategy for making better use of limited water resources. However, a wide range of organic compounds eventually renders them unsuitable for recycling. In water treatment processes, biologic
Kus, B.G., Kandasamy, J.K., Vigneswaran, S., Shon, H. & Moody, G. 2012, 'Two Stage Filtration For Stormwater Treatment: A Pilot Scale Study', Desalination and Water Treatment, vol. 45, no. 1-3, pp. 361-369.
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This paper presents the results of the granular medium filter and membrane (Ultra Flo membrane) filter experiments conducted with raw stormwater collected from a stormwater canal at Carlton, in Sydney. The filter medium experimented were granular activat
Shim, W.G., Mohammed Abdul, J., Mohammed, T.M., Vigneswaran, S., Ngo, H. & Kandasamy, J.K. 2012, 'Biofilter In Leachate Treatment Processes', Desalination and Water Treatment, vol. 41, no. 1-3, pp. 249-257.
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Landfill leachate is produced when rainwater infiltrates into the landfill and permeates through the decomposing waste within the landfill leaching out with it contaminants and pollutants. Untreated leachates can permeate ground water or mix with surface
Chekli, L., Phuntsho, S., Shon, H., Vigneswaran, S., Kandasamy, J.K. & Chanan, A.P. 2012, 'A Review Of Draw Solutes In Forward Osmosis Process And Their Use In Modern Applications', Desalination and Water Treatment, vol. 43, no. 1-3, pp. 167-184.
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Forward osmosis (FO) is one of the emerging membrane technologies which has gained renewed interest recently as a low energy desalination process. The central to FO process is the draw solution (DS) and the membrane because both play a substantial role o
Loganathan, L., Vigneswaran, S., Kandasamy, J.K. & Naidu, R. 2012, 'Cadmium Sorption And Desorption In Soils: A Review', Critical Reviews in Environmental Science and Technology, vol. 42, no. 5, pp. 489-533.
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Cadmium (Cd) is an environmental pollutant that can be readily taken up by plants and may enter the food chain, causing risk to human health. It can also affect soil quality and, if easily leached, has the potential to pollute surface and ground waters. Sorption and desorption are critical processes controlling the phytoavailability and mobility of Cd in soils. The authors present the present knowledge on the mechanisms and hysteresis of Cd sorption and desorption in soils and factors such as pH, ionic strength, index cation, other heavy metal cations, inorganic anions, organic ligands, Cd loading rate, and the type and amounts of organic matter and inorganic colloids influencing these processes. The methods used to determine the nature and magnitude of Cd sorption and desorption are also critically reviewed.
Phuntsho, S., Vigneswaran, S., Kandasamy, J.K., Hong, S., Lee, S. & Shon, H. 2012, 'Influence of temperature and temperature difference in the performance of forward osmosis desalination process', Journal Of Membrane Science, vol. 415-416, pp. 734-744.
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Forward osmosis (FO) is an emerging technology for low energy desalination. Amongst the many other factors, emperature of the draw solution (DS) and feed solution (FS) plays an important role in influencing the performance of the FO process. In this study, the influence of the temperature and the temperature difference on the performance of FO process has been studied in terms of water and solute fluxes. Temperature difference was maintained by elevating only one of the solutions (eitherDSorFS). The results indicate that, water flux on average increases by up to 1.2 % for every degree rise in temperature from 25&Acirc;&deg;C to 35&Acirc;&deg;C while this rise is 2.3% from 25&Acirc;&deg;C to 45&Acirc;&deg;C. Providing a temperature difference by elevating only the DS also enhanced the water flux significantly, although it was lower than FO process operated at isothermal conditions. However, elevating only the temperature of FS did not significantly improve the water flux although it was higher than the FO process operated at 25&Acirc;&deg;C. This as significant implications in FO process because the total mass of the DS requiring heat energy is significantly less than the total FS used. The influences of temperature in the FO process such as through changes in the thermodynamic properties of the solutions and the various concentration polarisation effects are also explained in details.
Jeong, S., Choi, Y., Nguyen, V., Vigneswaran, S. & Hwang, T.M. 2012, 'Submerged membrane hybrid systems as pretreatment in seawater reverse osmosis (SWRO): Optimisation and fouling mechanism determination', Journal Of Membrane Science, vol. 411-412, pp. 173-181.
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Three different submerged membrane hybrid systems (SMHSs) namely submerged membrane coagulation hybrid system (SMCHS), submerged membrane adsorption hybrid system (SMAHS), and submerged membrane coagulation&acirc;adsorption hybrid system (SMCAHS) were studied as pretreatment systems to seawater reverse osmosis (SWRO). The performances of these SMHSs were compared with that of submerged membrane system (without any coagulation or adsorption) in terms of trans-membrane pressure (TMP) development, critical flux, ultrafilter modified fouling index (UF-MFI), dissolved organic carbon (DOC) removal efficiency, and the removal of detailed organic fractions. The experimental results show that pretreatment by SMCAHS led to the best results in terms of organic removal and critical flux. With the low doses of ferric chloride (FeCl3) and powder activated carbon (PAC) of 0.5 mg of Fe3+/L and 0.5 g of PAC/L, respectively, this hybrid system could remove 72% of DOC and reduce the UF-MFI nearly five times. The initial DOC and UF-MFI of seawater used in this study were 2.53 mg/L and 14,165 s/L2, respectively. The application of three different membrane fouling models namely pore blockage, pore constriction, and cake formation models showed that cake formation was the predominant fouling mechanisms causing fouling in SMHSs.
Mohammed Abdul, J., Kumar, M.R., Vigneswaran, S. & Kandasamy, J.K. 2012, 'Removal Of Metsulfuron Methyl By Fenton Reagent', Journal of Industrial and Engineering Chemistry, vol. 18, no. 1, pp. 137-144.
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The removal of metsulfuron methyl (MeS)&acirc;a sulfonyl urea herbicide from contaminated water was investigated by advanced oxidation process (AOP) using Fenton method. The optimum dose of Fenton reagent (Fe2+/H2O2) was 10 mg/L Fe2+ and 60 mg/L H2O2 for an initial MeS concentration ([MeS]0) range of 0&acirc;80 mg/L. The Fenton process was effective under pH 3. The degradation efficiency of MeS decreased by more than 70% at pH > 3 (pH 4.5 and 7). The initial Fe2+ concentration ([Fe2+]0) in the Fenton reagent affected the degradation efficiency, rate and kinetics. The degradation of MeS at optimum dose of Fenton reagent was more than 95% for [MeS] 0 of 0&acirc;40 mg/L and the degradation time was less than 30 min. The determination of residual MeS concentration after Fenton oxidation by UV spectrophotometry was affected by the interferences from Fenton reagent. The estimation of residual MeS concentration after Fenton oxidation by high pressure/performance liquid chromatograph (HPLC) was interference free and represented the actual concentration of MeS and does not include the by-products of Fenton oxidation. The degradation kinetics of MeS was modelled by second order reactions involving 8 rate constants. The two reaction constants directly involving MeS were fitted using the experimental data and the remaining constants were selected from previously reported values. The model fit for MeS and the subsequent prediction of H2O2 were found to be within experimental error tolerances.
Mohammed, T.M., Loganathan, L., Kinsela, A., Vigneswaran, S. & Kandasamy, J.K. 2012, 'Enrichment, Inter-Relationship, And Fractionation Of Heavy Metals In Road-Deposited Sediments Of Sydney, Australia', Australian Journal of Soil Research, vol. 50, no. 3, pp. 229-238.
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Urban road-deposited sediments (RDS) are potential sources of heavy metal pollution of both terrestrial and aquatic environments. We determined the heavy metals enrichments, their possible sources, and potential bioavailability and mobility in RDS from n
Das Gupta, M., Loganathan, L. & Vigneswaran, S. 2012, 'Adsorptive Removal Of Nitrate And Phosphate From Water By A Purolite Ion Exchange Resin And Hydrous Ferric Oxide Columns In Series', Separation Science and Technology, vol. 47, no. 12, pp. 1785-1792.
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Elevated concentrations of nitrate and phosphate in surface and ground waters can lead to eutrophication, and nitrate can also cause health hazards to humans. The adsorption process is generally considered to be an efficient technique in removing these ions provided that the adsorbent is highly selective for these ions. Removal of nitrate and phosphate from a synthetic water (50 mg N/L as nitrate, 15 mg P/L as phosphate) and a wastewater (12.9 mg N/L as nitrate, 5.9 mg P/L as phosphate) using a Purolite A500P anion exchange resin and a hydrous ferric oxide (HFO) columns (60 cm height, 2 cm diameter, flow rate 1 m/h) in series containing 1&acirc;10% (w/w) of these adsorbents and the remainder anthracite (90&acirc;99%) were studied. Data from batch adsorption experiment at various concentrations of adsorbents satisfactorily fitted to Langmuir adsorption isotherm for nitrate and phosphate on Purolite with adsorption maxima of 64 mg N/g and 7 mg P/g and only for phosphate on HFO with adsorption maxima of 14 mg P/g. Both batch and column experiments showed that Purolite selectively removed nitrate and HFO selectively removed phosphate. The Purolite column BTC time was greater for nitrate than for phosphate. At the highest percentage by weight of Purolite almost all nitrate was removed in batch study and up to 1000 min in column study, but it was not able to remove a comparatively high percentage of phosphate. However, when the effluent from the Purolite column was passed through the HFO column almost all phosphate was removed. The two columns when set up in series also removed almost all nitrate and phosphate from the wastewater.
Jeong, S., Kim, L., Kim, S., Nguyen, V., Vigneswaran, S. & Kim, I.S. 2012, 'Biofouling Potential Reductions Using A Membrane Hybrid System As A Pre-treatment To Seawater Reverse Osmosis', Applied Biochemistry and Biotechnology, vol. 167, no. 6, pp. 1716-1727.
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Biofouling on reverse osmosis (RO) membranes is the most serious problem which affects desalination process efficiency and increases operation cost. The biofouling cannot be effectively removed by the conventional pre-treatment traditionally used in desa
Johir, J., George, J., Vigneswaran, S., Kandasamy, J.K., Sathasivan, A.S. & Grasmick, A. 2012, 'Effect Of Imposed Flux On Fouling Behavior In High Rate Membrane Bioreactor', Bioresource Technology, vol. 122, no. NA, pp. 42-49.
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The influence of imposed flux and aeration rates on membrane fouling in a submerged membrane bioreactor was studied. The experiments were conducted at four imposed fluxes and three aeration rates. The effect of flux on the reduction of membrane fouling w
Mohammed, T.M., Vigneswaran, S., Loganathan, L., Kandasamy, J.K. & Aryal, R. 2012, 'Removal of inorganic contaminants from simulated stormwater by three sorbents in columns under intermittent runoff condition', Separation Science and Technology, vol. 42, no. 14, pp. 2340-2347.
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Combined removal of inorganic contaminants from a synthetic tormwater was investigated by their sorption on hydrous ferric oxide (HFO) (5%), HFO + Ca(OH)2(6%), and HFO + Ca(OH)2 + MnO2 (7%) in columns containing 93-95% anthracite, conducted under seven intermittent runoffs, each of 8 h duration with a 40 h (drying) period between them. At the initial period when Ca(OH)2 produced elevated pHs, the HFO column removed less metals but more Se than the HFO + Ca(OH)2 columns. With increased time when the pH effect of Ca(OH)2 became insignificant, the MnO2 in the column increased the removal of all contaminants. The removal efficiencies (%) at the flow rate of 0.75 m/h for Cd, Cu, Ni, Zn by the HFO + Ca(OH)2 + MnO2 column were 88-100%, and Se by the HFO column were 92-94% for the 1st and 3rd runs. The corresponding values for the 5th and 7th runs were 51-88% and 82-88%, respectively.
Pradhan, M., Vigneswaran, S., Kandasamy, J.K. & Ben Aim, R. 2012, 'Combined effect of air and mechanical scouring of membranes for fouling reduction in submerged membrane reactor', Desalination, vol. 288, pp. 58-65.
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This study investigated the combined effect of air flow and use of granular support medium in suspension in a submerged membrane reactor to reduce membrane fouling. Lower membrane fouling and a slower rise in transmembrane pressure (TMP) were noticed when a higher air flow rate was used for membrane scouring. Further fouling reduction was achieved by adding a granular medium in the reactor. The results showed that in the absence of the granular medium, when air flow was tripled (from 600 to 1800 L/h/m2), the TMP development was decreased by 60%. TMP further dropped to 85% with the addition of granular medium (for the same air flow rate). The doubling of the air flow rate (from 600 to 1200 L/h/m2), without granular medium, led to a 32% reduction in TMP development at 10 L/m2.h. The same result was obtained at a lower air flow rate of 600 L/h/m2 with the granular medium. This result shows that the same reduction of TMP can be obtained by adding granular medium instead of doubling air flow rate. Therefore adding granular medium in the suspension (mechanical scouring) with air flow (air scouring) could be a sustainable alternative to applying high air flow in submerged membrane systems.
Chanan, A.P., Vigneswaran, S. & Kandasamy, J.K. 2012, 'Case study research: training interdisciplinary engineers with context-dependent knowledge', European Journal of Engineering Education, vol. 37, no. 1, pp. 97-104.
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It is now widely acknowledged that water management discipline is transforming, from being a public health and flood prevention challenge of the nineteenth century to a multi-dimensional challenge of water security for the twenty-first century. In order to train water engineers to be capable of working with this holistic multi-dimensional approach, a new paradigm in engineering education is required. Adjustments already made to undergraduate coursework are not enough; this new paradigm requires modifications to the PhD in engineering, with greater emphasis on interdisciplinary case study research. Such a change can deliver PhD graduates with both sufficient social and technical knowledge, who can then go on to become the hybrid lecturers crucially needed for training future water engineers.
Mohammed, T.M., Aryal, R., Vigneswaran, S., Loganathan, L., Kandasamy, J.K. & Naidu, R. 2012, 'Removal of heavy metals in stormwater by hydrous ferric oxide', Water Management, vol. 165, no. WM3, pp. 171-178.
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Stormwater runoff from urban and industrial areas contains several types of heavy metals that have negative ecological impacts on receiving waters, and therefore methods need to be developed to remove these pollutants. Combined removal of a mixture of heavy metal cations (Cu2&Atilde;&frac34;, Zn2&Atilde;&frac34;, Cd2&Atilde;&frac34;, and Ni2&Atilde;&frac34;) and an oxy anion (selenate, SeO42) from an artificially prepared stormwater was investigated by sorption of these heavy metals on hydrous ferric oxide (HFO) in a column experiment under intermittent runoff (wetting and drying) condition, as occurs between rainfall events in the field. The heavy metal removal behaviour varied between ions as well as with time. In each continuous column run (8 h) the amount of ions removed progressively decreased with time and reached a constant level at approximately 4&acirc;6 h. However, stopping the runoff for 40 h and starting the next runoff after this period removed a large quantity of heavy metals in the first few hours of this run. The intermittent runoff for seven runs showed that HFO has a high capacity to remove copper and zinc, which were present in higher concentrations in the stormwater than cadmium, nickel and selenium.
Ahmad, R., Nguyen, V., Shim, W.G., Vigneswaran, S., Moon, H. & Kandasamy, J.K. 2012, 'Effluent Organic Matter Removal By Purolite (R) A500PS: Experimental Performance And Mathematical Model', Separation and Purification Technology, vol. 98, pp. 46-54.
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In this study, the performance of Purolite(R)A500PS in effluent organic matter (EfOM) removal was evaluated through adsorption equilibrium, kinetics and fluidized bed experiments. It was found that the maximum EfOM removal capacity of PuroliteA500PS calculated by the Langmuir isotherm was 50.9 mg DOC/g PuroliteA500PS. The results also showed that fluidized bed operational conditions strongly affected the EfOM removal efficiency. A fluidized bed packed with PuroliteA500PS can maintain a consistent EfOM removal efficiency of more than 80% with more than 800 bed volumes from 10 mg DOC/L of synthetic wastewater. A majority of hydrophilic compounds (76.4%) and a significant amount of hydrophobic compounds (55%) were removed by the PuroliteA500PS fluidized bed. The Purolite(R)A500PS fluidized bed was also found to remove a majority of biopolymer (98.5%), humic substances (86.5%), and low molecular weight neutrals (83.3%).
Kus, B., Johir, M., Kandasamy, J., Vigneswaran, S., Shon, H.Y., Sleigh, R. & Moody, G. 2012, 'Performance of granular medium filtration and membrane filtration in treating stormwater for harvesting and reuse', Desalination and Water Treatment, vol. 45, pp. 120-127.
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&copy; 2012, Desalination Publications.Abstract: This paper discusses laboratory scale and pilot scale treatment systems used to in treat water from a stormwater canal in Carlton, Sydney. The laboratory scale pre-treatment systems investigated included flocculation, GAC filtration and fibre filter prior to laboratory scale steriflow stainless steel membrane filter. The results showed that these pre-treatments improved the quality of the filtrate as measured by the turbidity and TOC removal efficiency. The use of pre-treatment improved the TOC removal efficiency from 10% to 90%. Among the three pretreatment methods, GAC filter resulted in the highest TOC removal efficiency (88%). Pilot scale experiments were also carried out using stainless steel membrane filtration and GAC filtration at Carlton, Sydney. Pilot scale experiments showed that the Steri-Flow membrane filter treatment without any pre-treatment achieved an effluent filtrate turbidity of between 0.79&#8211;0.99 NTU which were well below the 5 NTU ADWG (2004) limit [1]. The influent raw stormwater had generally low concentrations of heavy metals. Following membrane filtration the concentration of all heavy metals were reduced to very low levels and well within the ADWG (2004) [1] limits. The membrane filter could not remove TOC in significant amounts. GAC adsorption used as post-treatment following Steri-flow membrane treatment effectively reduced the TOC influent feed levels. GAC filtration of stormwater provided a 70% removal of organics. It removed all types of organic. The GAC filter did not provide any further improvement to the turbidity level or heavy metal concentration following treatment with the Steri-flow membrane system.
Kus, B., Kandasamy, J., Vigneswaran, S., Shon, H. & Moody, G. 2012, 'Two stage filtration for stormwater treatment: A pilot scale study', Desalination and Water Treatment, vol. 45, no. 1-3, pp. 361-369.
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&copy; 2012 Desalination Publications. All rights reserved.This paper presents the results of the granular medium filter and membrane (Ultra Flo membrane) filter experiments conducted with raw stormwater collected from a stormwater canal at Carlton, in Sydney. The filter medium experimented were granular activated carbon (GAC), anthracite and sand. Each was used as a single medium in a 1 m filter column. The filter columns were operated at filtration velocity 10 m h1. The GAC filter column was capable of significantly reducing the influent dissolved organic carbon (DOC) concentrations. After GAC filtration of stormwater, the average concentration of DOC was 1.76 mg l 1, measured using LC-OCD, which represents a 70% removal of all types of organic. Membrane filtration removed a small additional amount of organics. The GAC filter as a pre-treatment to membrane filtration performed effectively with significant removals in most heavy metals although their influent concentrations were low. The treatment train of GAC filter column followed by membrane filtration was able to reduce the turbidity by 99%. The GAC filter by itself was able to reduce turbidity to an average of 84%. The GAC filter by itself and with the membrane filter both achieved turbidity levels below the ADWG (2004) limits of 5 NTU.
Aryal, R., Vigneswaran, S. & Kandasamy, J.K. 2011, 'Application of Ultraviolet (UV) Spectrophotometry in the Assessment of Membrane Bioreactor Performance for Monitoring Water and Wastewater Treatment', Applied Spectrocopy, vol. 65, no. 2, pp. 227-232.
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Ultraviolet (UV) spectroscopy has been widely used in monitoring water and wastewater treatment. In this study UV spectroscopy was used to investigate fouling development on the membrane surface of membrane bioreactors. The chemistry of mixed liquor present in the membrane bioreactor and the foulant deposited on the membrane surface was compared by analyzing the UV spectra. The mixed liquor showed different spectra than did the foulant. The foulant spectra showed a shift in absorbance peaks with operation time. The particle size distribution (<450 nm) was also examined to explain the UV fingerprints.
Liu, H., Shon, H., Okour, Y., Song, W. & Vigneswaran, S. 2011, 'Photocatalytic Degradation of Acid Red G by Bismuth Titanate in Three-phase Fluidized Bed Photoreactor', Journal of Advanced Oxidation Technologies, vol. 14, no. 1, pp. 116-121.
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The objectives of this study were to prepare a high-performance bismuth titanate photocatalyst and to develop a novel photocatalytic reactor with three-phase internal circulating fluidized bed photoreactor (TPICFBP). Bismuth titanate photocatalyst was hydrothermally prepared under optimum operating parameters such as hydrothermal temperature, reaction time and molar ratio of Bi to Ti. The photocatalytic activity of bismuth titanate using TPICFBP was evaluated for the photocatalytic degradation of Acid Red G (ARG). The photodegradation of ARG over Bi12TiO20 (12:1 molar ratio of Bi to Ti) under acidic condition showed the highest removal rate (92%) with wastewater flux and operating time of 10 L/h and 3 h, respectively.
Phuntsho, S., Listowski, A., Shon, H., Le-Clech, P. & Vigneswaran, S. 2011, 'Membrane autopsy of a 10 year old hollow fibre membrane from Sydney Olympic Park water reclamation plant', Desalination, vol. 271, no. 1-3, pp. 241-247.
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Membrane autopsy was performed for a 10 year old polypropylene (PP) hollow fibre microfiltration membrane from Sydney Olympic Park water reclamation plant. The properties of the membrane were studied using scanning electron microscope (SEM) imaging, contact angle, bubble test, thermogravimetric analysis, tensile strength test and functional group. The old and fouled membrane exhibited a significant difference in surface properties and material strength in comparison to the virgin membrane. The old and fouled membrane surface is less hydrophilic and less negatively charged indicating that aged membrane is more vulnerable to fouling than virgin membrane. The fibre material of the old fouled membrane appears less flexible and brittle. Foulant analysis indicated that major components of the metallic elements were silicon and calcium. The dissolved organic matter was mainly composed of biopolymers (hydrophilic) and humic substances (hydrophobic).
Mohammed, T.M., Vigneswaran, S. & Kandasamy, J.K. 2011, 'Biofiltration as pre-treatment to water harvesting and recycling', Water Science and Technology, vol. 63, no. 10, pp. 2097-2105.
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This paper presents the results of the long term biofilter experiments conducted with raw stormwater collected from a canal at Carlton, in Sydney. Anthracite and granular activated carbon (GAC) were used as a single filter media in biofilter columns. Media heights of 75 and 40 cm were used. The filter columns were operated at filtration velocities of 0.12 and 0.25 m/h. The removal efficiency for turbidity and DOC for the GAC filter media were found to be 75% and almost 100% respectively. The removal efficiency for the anthracite filter was much lower. Molecular weight distribution analysis showed an almost similar trend to the DOC removal. Compared with anthracite filter media, the GAC biofilter removed a much larger range of organic compounds present in the stormwater. The GAC biofilter removes organic matter earlier as compared to anthracite. Based on a limited sample of stormwater, the removal efficiency for phosphorus was upto 74% and that of nitrogen was up to 30%. In general GAC filter shows higher heavy metal removal efficiency than anthracite. The removal of zinc, iron, lead and nickel were good. However the concentration of heavy metal in the raw surface water sample was low.
Pradhan, M., Aryal, R., Vigneswaran, S. & Kandasamy, J.K. 2011, 'Application of air flow for mitigation of particle deposition in submerged membrane microfiltration', Desalination and Water Treatment, vol. 32, pp. 201-207.
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This study investigates the effect of microfiltration operating conditions on membrane fouling of colloidal particles of kaolin clay. Experiments were conducted with a flat sheet membrane submerged in a suspension prepared from kaolin clay powder of size varying from 0.1 to 4 mm (Sigma) with a mean particle size 2.10 mm. The particle size distribution of clay was unimodal and the concentration of kaolin clay was similar to the biomass concentration in a membrane bioreactor (10 g/L). The effects of scouring and permeate flux rates were studied in terms of the membrane fouling rate. A linear relationship between the transmembrane pressure (TMP) and particle deposition was established for different air flow rates and permeate flow rates. Air scouring was more effective at a low permeate flux. There was only a minor change in the mean particle size of deposited colloidal particles on the membrane at a given flux under varying air flows and at the beginning all had a similar rise in TMP. However, at the later stages as particles accumulated on the membrane surface there was a significant rise in TMP. 15 LMH flux was observed as critical flux beyond which a rise in the permeate flux showed a sharp rise in the TMP which varied with air flow rates and particle deposition. The sharp TMP rise that occurred during the initial few hours of operation indicated that air flow for fouling mitigation strategies should target this period to optimise the membrane process. The study showed that air flow and flux rates are the two major governing factors for particle deposition on the membrane surface.
Liu, H., Shon, H., Sun, X., Vigneswaran, S. & Nan, H. 2011, 'Preparation and characterization of visible light responsive Fe2O3TiO2 composites', Applied Surface Science, vol. 257, no. 13, pp. 5813-5819.
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In this studywepresent the effects of iron oxide (Fe2O3) on titanium dioxide (TiO2) in synthesising visiblelight reactive photocatalysts. A Fe2O3&acirc;TiO2 composite photocatalyst was synthesized from Fe2(SO4)3 and Ti(SO4)2 by a ethanol-assisted hydrothermal method. The preparation conditions were optimized through the investigation of the effects of hydrothermal temperature and time as well as molar ratio of Ti to Fe on the photocatalytic activity. The visual, physical and chemical properties of the Fe2O3&acirc;TiO2 composites were investigated. The results showed that -Fe2O3 and anatase TiO2 were present in the composites. The Fe2O3&acirc;TiO2 synthesized under optimum condition consisted of mesoporous structure with an average pore size of 4 nm and a surface area of 43m2/g. Under visible and solar light irradiation, the photocatalytic activity of optimized sample was significantly higher than that of pure TiO2. This sample led to a photodegradation efficiency of 90% and 40% of auramine under visible light and solar light, respectively.
Phuntsho, S., Shon, H., Vigneswaran, S. & Cho, J. 2011, 'Assessing membrane fouling potential of humic acid using flow field-flow fractionation', Journal Of Membrane Science, vol. 373, no. 1-2, pp. 64-73.
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Flow field-flow fractionation (FlFFF), although a separation technique, has many similarities with the crossflow membrane filtration system, thereby making it an ideal tool for studying membrane fouling. This study reports the assessment of the fouling potential of humic acid on ultrafiltration membrane using asymmetrical FlFFF. The fouling potential of organic matter was assessed by quantifying the reversible and irreversible adsorption of humic acid on the membrane through analysis of FlFFF fractogram. A strong correlation was observed between the reversible/irreversible adsorption data analysed and the membrane fouling potential. This assessment was further complimented by moment analysis results in order to interpret the fouling potential of humic acid. However, further researches are necessary before this approach can serve as an alternative index for measuring membrane fouling propensity.
Chinu, K.J., Vigneswaran, S., Kandasamy, J.K., Aryal, R. & Dharmapalan, D. 2011, 'Assessment of water treatment processes: detailed organic matter characterisation and membrane fouling indices at the Loddon Water Treatment Plant, Victoria, Australia', Water Science & Technology: Water Supply, vol. 11, no. 3, pp. 274-281.
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Recent advances in membrane technology have led to its broad application, and reverse osmosis (RO) systems now represent the fastest growing segment of the desalination market. Its performance is hindered by membrane fouling. In this study pre-treatment methods to reduce RO fouling were investigated including flocculation, adsorption and ion exchange. Detailed organic characterisations were made in terms of florescence spectroscopy excitation emission matrix (EEM), UV254 absorbance and liquid chromatography-organic carbon detection (LCOCD). The different pre-treatment methods were assessed in terms of the fouling potential. This was quantified in terms of the modified fouling index measured using a dead-end cell micro-filtration (MF) unit. The existing pre-treatment of granular activated carbon (GAC) filter led to a good organic removal. Among the pre-treatment methods tested in the laboratory, purolite ion exchange/adsorption was found to be better than FeCl3 flocculation in terms of the amount as well as the wide range of organics removal. A pre-treatment of flocculation with Poly-ferric-silicate (PFSi) as flocculent gave a higher removal of organic matter compared to other pre-treatments tested. DOC was reduced from 11.5 to 4.25 mg/L, and it removed mostly the humic type substances.
Liu, H., Xia, T., Shon, H. & Vigneswaran, S. 2011, 'Preparation of titania-containing photocatalysts from metallurgical slag waste and photodegradation of 2,4-dichlorophenol', Journal of Industrial and Engineering Chemistry, vol. 17, no. 3, pp. 461-467.
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A low cost, high performance titania-containing metallurgical slag photocatalysts (TCMSPx, x = H2SO4, HNO3, HCl) were prepared using a hydrothermal method. The prepared TCMSPx were characterized in terms of visual, physical and chemical properties. The photocatalytic activity of the TCMSPx was evaluated via the photodegradation of 2,4-dichlorophenol (2,4-D) in aqueous solution. The results showed that the characteristics and photocatalytic activity of TCMSPx were strongly affected by acidic solutions used during the acidolysis. TCMSPH2SO4 exhibited better characteristics and higher photocatalytic activity than TCMSPHNO3 and TCMSPHCl. OH radicals from TCMSPH2SO4 were produced under UV, visible and solar light irradiation. The degree of photodegradation of 2,4-D by TCMSPH2SO4 was 80.1%, 50.0% and 61.5% under UV, visible and solar light irradiation respectively. In addition, the removal of chlorine functional group on the 2,4-D benzene ring and the production of intermediates during 2,4-D photodegradation were monitored using ion chromatography, UV&acirc;vis spectra and high performance liquid chromatography of 2,4-D before and after photodegradation.
Chang, C., Tanong, K., Chiemchaisri, C. & Vigneswaran, S. 2011, 'Feasibility Study Of A Cyclic Anoxic/Aerobic Two-Stage Mbr For Treating Abs Resin Manufacturing Wastewater', Bioresource Technology, vol. 102, no. 9, pp. 5325-5330.
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This study investigated the feasibility and the treatment efficiency of a cyclic anoxic/aerobic two-stage MBR for treating polymeric industrial wastewater. The anoxic/aerobic hybrid MBR was operated without sludge withdrawal except sampling during the st
Chiemchaisri, W., Chiemchaisri, C., Dumrongsukit, C., Threedeach, S., Ngo, H. & Vigneswaran, S. 2011, 'Removal Of Water-Borne Microorganisms In Floating Media Filter-Microfiltration System For Water Treatment', Bioresource Technology, vol. 102, no. 9, pp. 5438-5443.
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Floating plastic media pre-filter (PP) in combination with microfiltration membrane (MF) was applied to the removal of water-borne microorganism from surface water. The system was operated with and with-out coagulant addition. Jar-test results suggested
Chanan, A.P., Vigneswaran, S., Kandasamy, J.K. & Simmons, B. 2011, 'Lessons for a viable water recycling industry', Institution of Civil Engineers. Proceedings. Water Management, vol. 164, no. 5, pp. 213-219.
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The platform on which the labour government came to power in Australia in November 2007 included a policy of setting a national wastewater recycling target of 30% by the year 2015. A similar target-based approach was followed by the solid waste recycling industry in Australia the policy of which focused on supply and did not adequately acknowledge the price competitiveness of the product and its demand. This paper highlights the lessons from the solid waste recycling industry and applies them to the water recycling sector. A sound water pricing regime that reflects the true costs of water and a competitive water industry is offered as a better policy alternative to setting recycling targets.
Phuntsho, S., Shon, H., Hong, S., Lee, S. & Vigneswaran, S. 2011, 'A novel low energy fertilizer driven forward osmosis desalination for direct fertigation: Evaluating the performance of fertilizer draw solutions', Journal Of Membrane Science, vol. 375, no. 1-2, pp. 172-181.
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Forward osmosis (FO) is a novel and emerging low energy technology for desalination. It will be particularly more attractive, if the draw solution separation and recovery are not necessary after FO process. The application of this new concept is briefly described here in this paper for the desalination of saline water for irrigation, using fertilizer as a draw agent. Instead of separating the draw solution from desalinated water, the diluted fertilizer draw solution can be directly applied for fertigation. We report the results on the commonly used chemical fertilizers as FO draw solution. Based on the currently available FO technology, about nine different commonly used fertilizers were finally screened from a comprehensive list of fertilizers and, their performances were assessed in terms of pure water flux and reverse draw solute flux. These results indicate that, most soluble fertilizers can generate osmotic potential much higher than the sea water. The draw solutions of KCl, NaNO3 and KNO3 performed best in terms of water flux while NH4H2PO4, (NH4)2HPO4, Ca(NO3)2 and (NH4)2SO4 had the lowest reverse solute flux. Initial estimation indicates that, 1 kg of fertilizer can extract water ranging from 11 to 29 L from sea water.
Aryal, R., Baral, B., Vigneswaran, S., Naidu, R. & Loganathan, L. 2011, 'Seasonal influence on urban dust PAH profile and toxicity in Sydney, Australia', Water Science And Technology, vol. 63, no. 10, pp. 2238-2243.
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Road dust is one of the major threats to the urban environment due to wash-off of dust to the surrounding catchments during wet weather period. The dust contains wide range of toxic contaminants such as heavy metals, polycyclic aromatic hydrocarbons (PAHs) and endocrine disrupting chemicals. Among the toxic contaminants, PAHs are of environmental concern due to their potential carcinogenic and mutagenic effect besides endocrine disruptive behaviour. Eighteen road dust samples from Sydney were collected in different time periods for a year and analysed for 16 US EPA PAHs. Total PAHs content range in the dust was 9&acirc;105 &Icirc;&frac14;g/g. Total and individual PAH contents were highest in the finest size fraction (<75 &Icirc;&frac14;m) and in winter compared to the other seasons. The PAH profiles in the different particle sizes were similar but different between the four seasons. The concentrations of higher molecular weight PAHs (4- and 5-rings) were much greater than the concentrations of lower molecular weight PAHs (2- and 3-rings). Toxicity equivalency factor application showed that the longer the dry weather period the higher the total PAHs content and toxicity in the dust.
Nguyen, V., Zhang, R., Vigneswaran, S., Ngo, H., Kandasamy, J.K. & Mathes, P. 2011, 'Removal of organic matter from effluents by Magnetic Ion Exchange (MIEX)', Desalination, vol. 276, no. 1-3, pp. 96-102.
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Magnetic Ion Exchange Resin (MIEX&Acirc;&reg;) is effective in removing the majority of organic carbon from biologically treated wastewater. It removed 77% of dissolved organic carbon (DOC) from synthetic wastewater when operated in batch mode using a MIEX&Acirc;&reg; concentration of 10 mL/L. A pseudo secondorder reaction rate model namely the Ho model was used for the kinetic study and it was found that it provided a realistic description of the adsorption kinetics of DOC. A fluidised bed MIEX&Acirc;&reg; contactor effectively removed organic matter from synthetic biologically treated sewage effluent with more than 60% DOC removal even after 172 bed volumes. The regenerated MIEX&Acirc;&reg; resin did not display any significant reduction in its ability to remove organic matter.
Johir, M.H., George, J., Vigneswaran, S., Kandasamy, J.K. & Grasmick, A. 2011, 'Removal and recovery of nutrients by ion exchange from high rate membrane bio-reactor (MBR) effluent', Desalination, vol. 275, no. 2, pp. 197-202.
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In this study a membrane bioreactor (MBR) with ion-exchange as post-treatment was investigated for organic removal and nutrient recovery. The MBR was operated at a short HRT of 4 h in order to mainly remove organic carbon. This was followed by an ion-exchange process to remove and later recover the nitrogen and phosphorus from the MBR effluent. The increase in membrane resistance was reduced by 90% (from 0.061 to 0.006 m-1d-1) when the air scouring rate was increased from 0.5 to 1.5 m3/m2 membrane area h. The organic removal rate in terms of DOC was 85&acirc;90%. The bio-polymer in the molecular weight range of 24,500 Da was retained by the membrane of the MBR while humic type substances and lower molecular organic matter (molecular weight of 360&acirc;60 Da) were not effectively removed by the membrane. The ion-exchange process effectively removed the nutrients from the effluent of the MBR. The retention of PO4 3&acirc; and NO3 &acirc; by the two ion-exchange columns in series was 85% and 95% respectively. Over 95&acirc;98% phosphate and nitrate recovery was obtained during regeneration of columns with 1% NaCl of 20 bed volumes. This integrated process can remove pollutants and at the same time recover nutrients and thus open a new source for nitrogen and phosphorous.
Kus, B.G., Kandasamy, J.K., Vigneswaran, S. & Shon, H. 2011, 'Water Quality in Rainwater Tanks in Rural and Metropolitan Areas of New South Wales, Australia', Journal of Water Sustainability, vol. 1, no. 1, pp. 33-43.
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This paper compares the water quality of rainwater tanks throughout the Sydney metropolitan area to that in rural New South Wales, Australia. The water quality is compared against the Australian Guidelines for Water Recycling (AGWR) to determine if the untreated rainwater from both areas can be considered suitable for non-potable water supply without filtration. Additionally this paper reports on a set of experiments where rainwater collected from a typical domestic roof in Sydney, New South Wales, Australia was treated by a pre-treatment of granular activated carbon (GAC) adsorption filter followed by micro-filtration. The GAC column removed the pollutants through an adsorption mechanism. GAC is a macroporous solid with a very large surface area providing many sites for adsorption and it is this property that makes it an efficient adsorbent. The parameters analysed were ammonia, anions and cations, heavy metals, nitrate and nitrite, pH, total hardness, total organic carbon, total suspended solids and turbidity. The results indicate that before treatment, the rainwater already complied to many of the parameters specified in the AGWR, certain pollutants have the potential at times to exceed the AGWR. The water quality was within the AGWR limits after the treatment. The micro- filtration flux values demonstrate that rainwater was able to be filtered through the membranes under low gravitational heads that are typically available in a rainwater tank while still producing sufficient membrane flux and pollutant removal rates.
Listowski, A., Ngo, H., Guo, W., Vigneswaran, S., Shin, H. & Moon, H. 2011, 'Greenhouse Gas (GHG) Emissions from Urban Wastewater System: Future Assessment Framework and Methodology', Journal of Water Sustainability, vol. 1, no. 1, pp. 113-125.
Over the last two decades much scientific effort has been expended on the radiative gaseous emissions in the atmosphere. Although there are no regulatory requirements for managing gaseous emissions at present, the long term indications are, that impact relater to air pollution must embrace the broad diversity and challenges associated with urban wastewater cycle management. This study has been considered as a precursor to development of a comprehensive impact assessment of gaseous emission from urban wastewater infrastructure and treatment facilities. It has been carried out in consideration of the future climate change scientific projections, including socio-economic and environmental impacts. Major progress could be gained from systemic approaches in relation to factors influencing emission and the collected data demonstrates correlation between wastewater quality, treatment and energy used with the level of emission. An early attempt was made to attribute environmental impact and costs on per capita basis, as the weight of responsibility to take action is shifting to the community and individuals. The presented framework and methodology offers reliable evaluation of gaseous emissions is an integrated context comprising technology, environment, social and economic factors.
Ahmad, R., Nguyen, V., Vigneswaran, S. & Ho, D. 2011, 'Removal of effluent organic matter by purolite fluidised bed and submerged membrane hybrid system', Desalination and Water Treatment, vol. 32, no. 1-3, pp. 194-200.
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In this study, Purolite (R) A500PS was used to remove effluent organic matter in a fluidised bed and submerged membrane hybrid system (SMHS). It was found that the fluidised bed purolite column can effectively remove 73% of dissolved organic compound (DOC) from synthetic biologically treated sewage effluent (BTSE). DOC removal can be reduced further, by up to 95% when the fluidised bed purolite column was combined with a treatment by granular activated carbon column. Purolite (R) A500PS was also used as an adsorbent in the SMHS. The results showed that critical flux of the SMHS depend on the purolite size. Critical fluxes of SMHS were 30 and 35 L/m(2). h where 0.1 g/L of purolite of sizes below 150 mu m and 150-300 mu m were used respectively. The removal efficiency of natural organic matter from synthetic BTSE by SMHS was a function of purolite dose. The removal efficiency increased from less than 60% to more than 70% when the purolite dose increased from 0.05g/L to 0.1g/L.
Listowski, A., Ngo, H., Guo, W. & Vigneswaran, S. 2011, 'A novel integrated assessment methodology of urban water reuse', Water Science And Technology, vol. 64, no. 8, pp. 1642-1651.
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Wastewater is no longer considered a waste product and water reuse needs to play a stronger part in securing urban water supply. Although treatment technologies for water reclamation have significantly improved the question that deserves further analysis is, how selection of a particular wastewater treatment technology relates to performance and sustainabiiity? The proposed assessment model integrates; (i) technology, characterised by selected quantity and quality performance parameters; (ii) productivity, efficiency and reliability criteria; (iii) quantitative performance indicators; (iv) development of evaluation model. The challenges related to hierarchy and selections of performance indicators have been resolved through the case study analysis. The goal of this study is to validate a new assessment methodology in relation to performance of the microfiltration (MF) technology, a key element of the treatment process. Specific performance data and measurements were obtained at specific Control and Data Acquisition Points (CP) to satisfy the input-output inventory in relation to water resources, products, materiai flows, energy requirements, chemicals use, etc. Performance assessment process contains analysis and necessary linking across important parametric functions leading to reliable outcomes and results.
Jeong, S., Nateghi Ghasemian Nejad, F., Nguyen, V., Vigneswaran, S. & Tuan, A. 2011, 'Pretreatment for seawater desalination by flocculation: Performance of modified poly ferric silicate (PFSi-δ) and ferric chloride as flocculants', Desalination, vol. 283, pp. 106-111.
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Submerged microfiltration system coupled with in-line flocculation as pretreatment for seawater reverse osmosis has the potential to remove organic compounds and mitigate fouling. The effect of flocculation on the performance of microfiltration (MF) was investigated using two flocculants, namely, modified poly ferric silicate (PFSi-&Icirc;&acute;) and ferric chloride (FeCl3). The experimental results were analysed in terms of organic removal efficiency and critical flux. Both PFSi-&Icirc;&acute; and FeCl3 were found to be suitable as pretreatment because of their capacity in removing organic compounds. The results show that PFSi-&Icirc;&acute; was better than FeCl3 in terms of removing turbidity and dissolved organic carbon (DOC), particularly in removing hydrophilic compounds. The highest DOC removals of 68% and 57% were obtained when PFSi-&Icirc;&acute; at a dose of 1.2 mg Fe3+/L and FeCl3 at 3 mg Fe3+/L were used, respectively. It was observed that PFSi-&Icirc;&acute; (1.2 mg Fe3+/L) and FeCl3 (3 mg Fe3+/L) led to an increase of critical flux from 20 L/m2 h to 35 L/m2 h and 55 L/m2 h, respectively.
Jeong, S., Nguyen, V. & Vigneswaran, S. 2011, 'Submerged membrane coagulation hybrid system as pretreatment to organic matter removai from seawater', Water Science & Technology: Water Supply, vol. 11, no. 3, pp. 352-357.
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In this study, a commonly used ferric chloride was utilised as coagulant for removing organic compounds from seawater. More than 57% of dissolved organic carbon (DOC) was removed at optimum dosage of 3 mg Fe+3/L. The coagulation by FeCl3 at optimum dosage could remove a majority (95%) of hydrophobic compounds. The results from Liquid Chromatography &acirc; Organic Carbon Detector showed that only <0.02 mg/L of hydrophobic compounds was found after coagulation. In addition, the modified fouling index decreased considerably from 15,848 s/L2 with raw seawater to 3,025 s/L2 with seawater after coagulation. In-line coagulation coupled with submerged membrane system (ICSMS) was also trialled. It is observed that critical flux was increased from 20 L/m2&Acirc;h in the conventional submerged membrane system to 55 L/m2 h in ICSMS. The ICSMS could remain the high DOC removal efficiency (more than 70%) at filtration rate of 20 L/m2 h when keeping the development of trans-membrane pressure was significant lower than that of conventional submerged membrane system.
Saminathan, S., Liu, H., Nguyen, V. & Vigneswaran, S. 2011, 'Organic matter removal from biologically treated sewage effluent by flocculation and oxidation coupled with flocculation', Desalination and Water Treatment, vol. 32, no. 1-3, pp. 133-137.
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Flocculation alone and flocculation coupled with oxidation process were used for removing organic matter from biologically treated sewage effluent. The performances of different flocculants such as ferric sulphate, ferric nitrate, ferric chloride, and aluminium sulphate were experimentally evaluated. Among the flocculants tested, ferric chloride was selected because of its highest dissolved organic carbon (DOC) removal efficiency (67%) and the large size of the floc (mean size d(0.5) = 53.04 &Icirc;&frac14;m). The optimum dosage of FeCl3 was determined as 16 mg (Fe3+)/L. Different fractionation of organic matter before and after the flocculation process was analyzed. It was observed that FeCl3 could remove 90% of hydrophobic compounds and 61% of hydrophilic compounds. Oxidation process by Fenton reagent coupled with flocculation was also trialed. It is observed that DOC removal efficiency of Fenton reagent coupled with flocculation could reach 86%. The combination of flocculation and Fenton reagent increased the hydrophilic removal to 85%.
Shon, H., Vigneswaran, S., Kandasamy, J.K., Kim, J. & Kim, J. 2011, 'Advanced Characterization Techniques Of Organic Matter In Aqueous Solutions', Journal of the Korean Industrial and Engineering Chemistry, vol. 22, no. 1, pp. 1-14.
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Water is the most precious resource to human being, but it is polluted by different organic compounds. Organic matter (OM) in aqeous solutions is one of the important parameters of concern for human and environmental impact, and thus, it is essential to
Chanan, A.P., Kandasamy, J.K. & Vigneswaran, S. 2011, 'Role Of Case Study Research In Training The Renaissance Water Engineer', Global Journal of Engineering Education, vol. 13, no. 3, pp. 110-116.
Contemporary water management challenges around Australia highlight water engineers' inability to understand the community's needs. Developing new technologies is not enough. Implementation of these technologies can only take place if the engineers under
Johir, M.H., Aryal, R., Vigneswaran, S., Kandasamy, J.K. & Grasmick, A. 2011, 'Influence Of Supporting Media In Suspension On Membrane Fouling Reduction In Submerged Membrane Bioreactor (Smbr)', Journal Of Membrane Science, vol. 374, no. 1-2, pp. 121-128.
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In this study, the SMBR was compared in terms of membrane fouling with and without the addition of suspended medium in the membrane reactor. The effectiveness of medium in suspension in submerged membrane bioreactor (SMBR) was evaluated at different filt
Aryal, R., Vigneswaran, S., Loganathan, L., Kandasamy, J.K. & Mohammed, T.M. 2011, 'Hydrous iron oxide for removal of inorganic contaminants in simulated stormwater: A batch sorption kinetics study', Korean Journal of Chemical Engineering, vol. 28, no. 8, pp. 1706-1712.
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Urban stormwater runoff, which consists of inorganic and organic contaminants, is a major source of pollutants to receiving waters and therefore they need to be removed. Simultaneous removal of contaminants, Cd2+, Cu2+, Ni2+, Zn2+ (heavy metal cations), and SeO4 2&acirc; (oxyanion) from a simulated stormwater by a hydrous ferric oxide (HFO) was studied in batch and column sorption experiments. In the batch experiment the rate of sorption of the ions was rapid at the beginning and reached equilibrium in approximately 300 min. The amounts of ions sorbed were proportionate to the respective initial concentration of the ions added to the HFO. Cluster analysis showed that all heavy metals had similar sorption behavior, whereas Se had a distinctly different sorption process. Of the three different kinetic models tested the pseudo-first order kinetic model fitted the data the best. The column experimental results beyond 180 min were consistent with those of the batch experiment that the removal efficiencies of the ions were in proportion to the ion concentration in the feed. Below 180 min, Cu appeared to be preferentially removed than Zn.
Kus, B.G., Kandasamy, J.K., Vigneswaran, S., Shon, H. & Areerachakul, N. 2011, 'Water quality of membrane filtered rainwater', Desalination and Water Treatment, vol. 32, pp. 208-213.
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Although most Australians receive their domestic supply from reticulated mains or town water, there are vast areas with very low population densities and few reticulated supplies. In many of these areas rainwater collected in tanks is the primary source of drinking water. Heavy metals are a concern as their concentration in rainwater tanks was found to exceed recommended levels suitable for human consumption. This paper reports on experimental investigations where rainwater collected from a typical domestic roof in Sydney, Australia was treated in two stages of filtration including granular activated carbon (GAC) as a pre-treatment adsorption filter media and a metallic membrane from Steri-flow Filtration Systems Pty. Ltd. The quality of the treated rainwater was compared against the drinking water standards to determine its suitability as a supplement for potable water supply. The pollutants analysed were heavy metals, total coliform and faecal coliforms, total organic carbon, total suspended solids and turbidity. The results indicate that before treatment, the rainwater already complied with many of the parameters specified in drinking water standards. The metallic membrane performed well in removing suspended particles and heavy metals from the rainwater. The performance of the metallic membrane is greatly improved by the use of pre-treatment such as GAC which was used in this experiment.
Ho, D., Vigneswaran, S., Ngo, H., Shon, H., Kandasamy, J.K., Chang, Y. & Chang, J. 2011, 'Photocatalysis of Trimethoprim (TRI) in Water', Sustainable Environment Research (SER), vol. 21, no. 3, pp. 149-154.
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The advantage of the use of photocatalysts to treat persistent organic pollutants (POP) was demonstrated with the decomposition of trimethoprim (TRI), an antibiotic most frequently detected in municipal wastewaters and surface waters. In this study, the oxidation process by UV/TiO2 was employed as an alternative to advanced oxidation process (AOP) to remove residual antibiotics from water. High concentrations of TRI were used to study the efficiency of photocatalysis. Both batch and continuous photoreactors were used. The decomposition of TRI by TiO2/UV photooxidation occurred gradually over time. On the other hand, with UV irradiation alone, the reduction of TRI mineralization was relatively small. The effect of light intensity showed there was no significant impact of UV light intensity on the degradation of TRI in the range of increasing intensities studied. The simulation using first-order kinetics provided a good fit with the experimental data. In the continuous system, the feed flow rate was adjusted to maximize the percentage of mineralization of targeted compounds inside the photoreactor. A lower flow rate, i.e., higher detention time, achieved higher percentage of TRI mineralization. The results indicated that TiO2/UV irradiation was effective in removing TRI.
Khorshed, C., Vigneswaran, S., Kandasamy, J.K., Aryal, R. & Dharmapalan, D. 2011, 'Assessment of water treatment processes: Detailed organic matter characterisation and membrane fouling indices at the Loddon Water Treatment Plant, Victoria, Australia', Water Science and Technology, vol. 11, no. 3, pp. 274-280.
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Aryal, R., Kandasamy, J., Vigneswaran, S., Naidu, R. & Lee, H.S. 2011, 'Review of stormwater quality, quantity and treatment methods part 2: Stormwater: Quality modelling', Environmental Engineering Research, vol. 16, no. 4, pp. 143-149.
In this paper, review of stormwater quality and quantity in the urban environment is presented. The review is presented in three parts. This second part reviews the mathematical techiques used in the stromwater quality modelling and has been undertaken by examining a number of models that are in current use. The important features of models are discussed.
Liu, H., Shon, H.K., Okour, Y., Song, W. & Vigneswaran, S. 2011, 'Photocatalytic degradation of Acid Red G by Bismuth titanate in three-phase fluidized bed photoreactor', Journal of Advanced Oxidation Technologies, vol. 14, no. 1, pp. 115-121.
The objectives of this study were to prepare a high-performance bismuth titanate photocatalyst and to develop a novel photocatalytic reactor with three-phase internal circulating fluidized bed photoreactor (TPICFBP). Bismuth titanate photocatalyst was hydrothermally prepared under optimum operating parameters such as hydrothermal temperature, reaction time and molar ratio of Bi to Ti. The photocatalytic activity of bismuth titanate using TPICFBP was evaluated for the photocatalytic degradation of Acid Red G (ARG). The photodegradation of ARG over Bi12TiO20 (12:1 molar ratio of Bi to Ti) under acidic condition showed the highest removal rate (92%) with wastewater flux and operating time of 10 L/h and 3 h, respectively. &copy; 2011 Science & Technology Network, Inc.
Aryal, R., Kandasamy, J., Vigneswaran, S., Naidu, R. & Lee, S.H. 2011, 'Review of stormwater quality, quantity and treatment methods part 1: Stormwater quantity modelling', Environmental Engineering Research, vol. 16, no. 4, pp. 71-78.
A review of stormwater quantity and quality in the urban environment is presented. The review is presented in three parts. The first part reviews the mathematical methods for stormwater quantity and has been undertaken by examining a number of stormwater models that are in current use. The important feature of models, their applications, and management has been discussed. Different types of stormwater management models are presented in the literatures. Generally, all the models are simplified as conceptual or empirical depending on whether the model is based on physical laws or not. In both cases if any of the variables in the model are regarded as random variables having a probability distribution, then the model is stochastic model. Otherwise the model is deterministic (based on process descriptions). The analytical techniques are presented in this paper.
Chinu, K.J., Johir, M.H., Vigneswaran, S., Shon, H. & Kandasamy, J.K. 2010, 'Assessment of pretreatment to microfiltration for desalination in terms of fouling index and molecular weight distribution', Desalination, vol. 250, no. 2, pp. 644-647.
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In this study, different processes such as flocculation with ferric chloride (FeCl3) and deep bed filtration (sand filtration and dual media filtration) as a pre-treatment to microfiltration (MF) were used for seawater desalination. The performance of these pre-treatments was determined in terms of silt density index (SDI) and modified fouling index (MFI) and flux decline in MF. Flux decline of MF with seawater was 45% without any pre-treatment, 42% after pre-treatment of FeCl3 flocculation, 24% after pre-treatment of sand filtration with in-line coagulation and 22% after pre-treatment of dual media filtration (sand and anthracite), respectively. MFI and SDI also indicated that deep bed filtration with in-line flocculation was better pretreatment than flocculation alone. Detailed molecular weight distribution (MWD) of seawater organic matter was examined after different pretreatments. MWD of the initial seawater mainly ranged from 1510 Da to 130 Da. Deep bed filtration with in-line flocculation removed relatively large molecular weight of organic matter (1510&acirc;1180 Da), while the small molecular weights (less than 530 Da) were not removed.
Lee, J., Johir, M.H., Chinu, K.J., Shon, H., Vigneswaran, S., Kandasamy, J.K., Kim, C.W. & Shaw, K. 2010, 'Novel pre-treatment method for seawater reverse osmosis: Fibre media filtration', Desalination, vol. 250, no. 2, pp. 557-561.
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A high rate fibre filter was used as a pre-treatment to seawater reverse osmosis (SWRO) to reduce membrane fouling. Seawater was drawn from Chowder Bay where the Sydney Institute of Marine Science, Australia is located. A lab-scale fibre filter with a height of 1000 mm and a diameter of 30 mm was used in conjunction with in-line coagulation. The effect of operating the fibre filter with different packing densities (105, 115 kg/m3) and filtration velocities (40, 60 m/h) was investigated in terms of silt density index (SDI10), modified fouling index (MFI), pressure drop (&Icirc;P), turbidity and molecular weight distribution (MWD). The use of in-line coagulation improved the performance of fibre filter as measured by the MFI and SDI. Regardless of filtration velocity and packing density the MFI and SDI10 values remained low as did the turbidity until the end of the filtration run. The MWD analysis showed the removal efficiencies of organic materials like biopolymers, fulvic acids, low MW acids for even experiments with the highest filtration velocity (60 m/h) and lowest packing density (105 kg/m3). This pre-treatment has a small foot print as it has the capacity of operating at a very high filtration velocity
Guo, W., Zhang, R., Vigneswaran, S., Ngo, H. & Kandasamy, J.K. 2010, 'Membranes coupled with physico chemical treatment in water reuse', Water Science and Technology, vol. 61, no. 2, pp. 513-519.
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In this study, short-term experiments were conducted with different configurations of membrane hybrid systems to treat biological treated sewage effluent containing refractory organic pollutants: (i) submerged hollow fiber microfiltration (SMF) alone; (ii) spiral flocculator (SF)-SMF without settling; (iii) SF-PAC-SMF without settling and (iv) SMF with magnetic ion exchange resin MIEXw pretreatment. The results indicated that the pre-flocculation of SF could improve the mitigation of membrane fouling significantly even when the system was operated at a high membrane filtration rate. The transmembrane pressure (TMP) of SF-PAC-SMF only increased marginally (0.8 kPa over 8 hours). SF-SMF without the addition of powdered activated carbon (PAC) also took a relatively long duration for the TMP to increase. The TMP only increased by 2.5 kPa over 8 hours. The SF-PAC-MF system resulted in a high dissolved organic carbon (DOC) removal of more than 96%. When used as pre-treatment to submerged membranes, the fluidized bed MIEXw contactor could remove a significant amount of organic matter in wastewater. This pre-treatment helped to reduce the membrane fouling and kept the TMP low during the membrane operation.
Park, K.H., Shim, W.G., Shon, H., Lee, S.G., Ngo, H., Vigneswaran, S. & Moon, H. 2010, 'Adsorption Characteristics of Acetaldehyde on Activated Carbons Prepared from Corn-Based Biomass Precursor', Separation Science and Technology, vol. 45, no. 8, pp. 1084-1091.
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The ACs (R-1/2 and R-1/4) having two different textual and chemical properties are prepared from corn-based biomass precursor and evaluated together with a wood-based activated carbon (WAC) at room temperature using a gas chromatograph. The results obtained from the correlation studies indicate that the pore size distribution (below 8A &Euml; ) and the relatively lower energetic heterogeneity of ACs on acetaldehyde adsorption are considerable factors rather than that of a specific surface area and surface chemistry. The adsorption equilibrium of ACs is well correlated with the Sips equation. The pseudo second-order equation was better in describing the ACs&acirc; adsorption kinetic of acetaldehyde.
Shon, H., Vigneswaran, S., El Saliby, I., Okour, Y., Kim, I.S., Cho, J., Park, H.J., Kim, J.B. & Kim, J.H. 2010, 'Hydrogen production affected by Pt concentration on TiO2 produced from the incineration of dye wastewater flocculated sludge using titanium tetrachloride', Desalination and Water Treatment, vol. 15, no. 1-3, pp. 214-221.
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TiO2 from the incineration of dye wastewater flocculated sludge using TiCl4 coagulant was produced. Optimal catalyst amount and Pt-loading on TiO2 were studied for the production of H2 by photocatalytic reforming of methanol (6% vol.). On the other hand, BTSE (biologically treated sewage effluent) was flocculated using TiCl4 and produced sludge was incinerated to generate TiO2. TiO2 was loaded with optimum Pt and added to the supernatant in a photocatalytic reactor to test the efficiency of using remaining organics as a &acirc;sacrificial reagent&acirc; for photocatalytic hydrogen production. Dissolved organic carbon (DOC) and molecular weight distribution (MWD) were measured for nanofiltration (NF) and TiCl4 flocculation followed by photocatalysis. TiO2 (from the incineration of BTSE flocculated sludge using TiCl4) was produced and loaded with 0.5% Pt. Results showed that the optimum concentration of TiO2 (from dye wastewater) for H2 production was 0.3 g/L, while the optimum amount of Pt was 0.5%. DOC and MWD removal was similar for the flocculation of BTSE followed by photocatalytic reaction and the NF process. Remaining organic compounds after flocculation could not be used as sacrificial reagent to induce H2 production. Further investigations on studying the UV intensity and/or identifying organic/inorganic scavengers to inhibit H2 production are underway.
Aryal, R., Vigneswaran, S. & Kandasamy, J.K. 2010, 'Influence of buoyant media on particle layer dynamics in microfiltration membranes', Water Science & Technology: Water Supply, vol. 61, no. 7, pp. 1733-1738.
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This study forms a part of the physical study of the membrane bioreactor in presence of buoyancy media. Kaolin clay suspension with buoyancy media (anthracite) was used as a suspension and the particle layer development on membrane surface with evolution of time was studied. Presence of buoyancy media reduced the pressure development by almost two folds compared to in absence of the media. The particles deposition on membrane surface was size selective. The mean particle diameter (0.45mm) deposited on the membrane surface remained almost similar in presence of the media after 7 hrs run where as in its absence the mean diameter finer particles deposition occurred at the beginning followed by coarser particles.
Lebegue, J., Aryal, R., Shon, H., Vigneswaran, S., Heran, M. & Grasmick, A. 2010, 'Identification and quantification of foulant in submerged membrane reactor', Desalination and Water Treatment, vol. 24, no. 1-3, pp. 278-283.
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In submerged membrane system, membrane fouling is linked to the reversible accumulation of macromolecules and solids on the membrane surface and the irreversible sorption of soluble molecules inside the pores. In the first part of the paper, the fouling was analysed at two different aeration rates through the determination of membrane resistance due to (a) sludging (Rsludging), (b) irreversible biofilm (Rbiofilm) and (c) adsorption of organic (Radsorption). These results confirm the importance of aeration for sludge control in the bundle. In the second part of the paper, irreversible foulant obtained at different aeration rates were characterised. Membrane air flow rate limits adsorption of biopolymers onto or into the membrane surface.
Kus, B.G., Kandasamy, J.K., Vigneswaran, S. & Shon, H. 2010, 'Analysis of first flush to improve the water quality in rainwater tanks', Water Science and Technology, vol. 61, no. 2, pp. 421-428.
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Although most Australians receive their domestic supply from reticulated mains or town water, there are vast areas with very low population densities and few reticulated supplies. In many of these areas rainwater collected in tanks is the primary source of drinking water. Heavy metals have recently become a concern as their concentration in rain water tanks was found to exceed recommended levels suitable for human consumption. Rainwater storage tanks also accumulate contaminants and sediments that settle to the bottom. Although not widely acknowledged, small amounts of contaminants such as lead found in rain water (used as drinking water) may have a cumulative and poisonous effect on human health over a life time. This is true for certain factors that underlie many of the chronic illnesses that are becoming increasingly common in contemporary society. The paper reports on a study which is part of a project that aims to develop a cost effective in-line filtration system to improve water quality in rainwater tanks. To enable this, the characteristics of rainwater need to be known. One component of this characterization is to observe the effects of the first flush on a rainwater tank. Samples of the roof runoff collected from an urban residential roof located in the Sydney Metropolitan Area in the initial first few millimetres of rain were analysed. The results show that bypassing the first 2mm of rainfall gives water with most water quality parameters compliant with the Australian Drinking Water Guidelines (ADWG) standards. The parameters that did not comply were lead and turbidity, which required bypassing approximately the first 5mm of rainfall to meet ADWG standards. Molecular weight distribution (MWD) analysis showed that the concentration of rainwater organic matter (RWOM) decreased with increasing amount of roof runoff.
Erdei, L., Vigneswaran, S. & Kandasamy, J.K. 2010, 'Modelling of submerged membrane flocculation hybrid systems using statistical and artificial neural networks methods', Journal of Water Supply: Research and Technology. AQUA, vol. 59, no. 2-3, pp. 198-208.
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Hybrid membrane filtration processes involve complex physical, chemical and biological phenomena, thus their mechanistic modelling is challenging. The chief advantages of statistical and artificial neural networks (ANN) models (data-driven models) are that they do not require assumptions and simplifications to establish relationships from data. This paper investigates the characteristics and performance of several data-driven methods to model a hybrid membrane system. The focus is on the application of regression analysis and artificial intelligence based methods to a steady-state system. Among empirically based approaches, ANN neural networks methods were found to be very useful to predict permeate quality and membrane fouling. In the past multivariate nonlinear regression had barely been investigated for process modelling in water and waste water treatment. In this study polynomial multivariate nonlinear regression showed a superior performance. Multivariate parametric nonlinear models could match the performance of the nonparametric ANN models in the empirical modelling of complex systems, especially when combined with advanced optimization methods. This paper gives the methodology of how one could optimize a membrane hybrid system using ANN, validating it with one set of data. The same procedure/methodology can be applied to similar systems.
Ho, D., Vigneswaran, S. & Ngo, H. 2010, 'Integration of Photocatalysis and Microfiltration in Removing Effluent Organic Matter from Treated Sewage Effluent', Separation Science and Technology, vol. 45, no. 2, pp. 155-162.
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An integration of photocatalysis with low-pressure submerged membrane has attracted growing interest for its synergic advantages in water and wastewater treatment. In this study, the adsorption and photocatalytic oxidation of organic compounds by UV light responsive titanium dioxide (TiO2) were investigated. First, the adsorption behavior of the TiO2 was examined by the adsorption isotherm and kinetics experiments. The photocatalytic reactivity of the catalysts was then compared at different operating conditions. The results indicate that the Freundlich model described well the adsorption capacity of both materials. The photocatalytic kinetics showed that the highest removal of effluent organic matter (EfOM) was achieved at an optimum concentration of 1.0 g/L of TiO2. In addition, it was found that the pre-photosensitization with titanium dioxide/ultra-voilet radiation (TiO2/UV) could effectively reduce membrane fouling and enhance the permeate flux of the submerged membrane reactor when it was used as a post-treatment. An increase of 10% in organic removal efficiency was achieved by the posttreatment of membrane filtration. The sustainable flux of the membrane reactor increased from 25 up to 40 L/m2.h when the pretreatment of photocatalysis was used.
Chanan, A.P., Kandasamy, J.K., Vigneswaran, S., Spyrakis, G., Ghetti, I. & idris, E. 2010, 'Applied Rainwater Harvesting Education: An Australian Case Study', Journal of Environmental Science and Engineering, vol. 4, no. 3, pp. 32-35.
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Rainwater tanks have been an integral part of the Australian landscape given the vital role these tanks have played over the years in rural Australia. In the past Local government and Water Authorities actively discouraged the use of rainwater tanks and informing citizens that they were illegal and dangerous. Kogarah Council within the Sydney metropolitan area is a proactive Council, and became the first council in Sydney to adopt Total Water Cycle Management (TWCM) principles into its Sustainability Management Plan, integrating these principles into on-ground projects at a catchment level in a planned and strategic approach. Among it priority projects was the Rainwater Tanks in Schools. This paper outlines how this project assisted all 22 schools in the Kogarah LGA (The Local Government Association) to increase the efficiency of water use and install rainwater tanks to reduce potable water use in toilet flushing and irrigating school gardens. The rainwater harvesting reduced the amount of drinking water used for toilet flushing and/or irrigation. The rainwater tanks also act as a visual reminder to conserve water for the students. The project has equipped the next generation with the necessary tools to make informed decisions and undertake actions that will move towards achieving sustainability.
Chinu, K.J., Vigneswaran, S., Erdei, L., Shon, H., Kandasamy, J.K. & Ngo, H. 2010, 'Comparison of fouling indices in assessing pre-treatment for seawater reverse osmosis', Desalination and Water Treatment, vol. 18, no. 1-5, pp. 187-191.
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In this study, different processes such as flocculation with ferric chloride (FeCl3) and deep bed filtration (sand filtration and dual media filtration) as a pre-treatment were used for seawater desalination. The performance of these pre-treatments was determined in terms of silt density index (SDI) and modified fouling index by using microfilter (MF-MFI), ultrafilter (UF-MFI), and nanofilter (NF-MFI) membrane. MFI and SDI indicated that deep bed filtration with in-line flocculation was better pre-treatment than flocculation alone as colloidal particles are removed after this pretreatment. UF-MFI and NF-MFI indicated that these pretreatment cannot remove dissolved organic matter as the fouling reduction was smaller. Detailed molecular weight distribution (MWD) of seawater organic matter was examined after different pretreatments. MWD of the initial seawater mainly ranged from 1510 Da to 130 Da. Deep bed filtration with in-line flocculation removed relatively large molecular weight of organic matter (1510&acirc;1180 Da), while the small molecular weights (less than 530 Da) were not removed.
Shon, H., Phuntsho, S., Vigneswaran, S., Kandasamy, J.K., Nghiem, L.D., Kim, G., Kim, J.B. & Kim, J. 2010, 'Preparation of Titanium Dioxide Nanoparticles from Electrocoagulated Sludge using Sacrificial Titanium Electrodes', Environmental Science & Technology, vol. 44, no. 14, pp. 5553-5557.
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A comprehensive investigation of electrocoagulation using sacrificial titanium (Ti) electrodes in wastewater was carried out. The effects of specific process variables, such as initial pH, mixing, current density, initial organic loading, and ionic/ electrolyte strength were first optimized to produce recyclable Ti-based sludge. The sludge was incinerated at 600&Acirc;&deg;C to produce functional TiO2 photocatalyst. X-ray diffraction analysis revealed that TiO2 produced at optimum electrocoagulation conditions was mostly anatase structure. The specific surface area of the synthesized TiO2 photocatalyst was higher than that of the commercially available and widely used Degussa P-25 TiO2. Furthermore, energy dispersive X-ray and X-ray photoelectron spectroscopy analyses showed that in additional to titanium and oxygen, this photocatalyst is also composed of carbon and phosphorus. These elements were mainly doped as a substitute site for the oxygen atom. Transmission electron microscopy images exhibited sharply edged nanorods, round nanoparticles, and nanotubes with nonuniform shapes showing some structural defects. Photodecomposition of gaseous acetaldehyde by this photocatalyst was also conducted under UV and visible light irradiation to study the photocatalytic properties of the doped TiO2 photocatalyst. While no photocatalytic activity was observed under visible light irradiation, this doped TiO2 photocatalyst exhibited high photocatalytic activity under UV light.
Nguyen, V., Vigneswaran, S., Ngo, H. & Kandasamy, J.K. 2010, 'Arsenic removal by iron oxide coated sponge: Experimental performance and mathematical models', Journal of Hazardous Materials, vol. 182, no. 1-3, pp. 723-729.
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Millions of people worldwide are at risk from the presence of arsenic in groundwater. In this study, adsorption equilibrium and long term experiments were carried out to evaluate the performance of iron oxide coated sponge (IOCSp) in arsenic removal. It was found that maximum adsorption capacity of IOCSp for As(III) and As(V) calculated by Sips isotherm was 4.2 and 4.6 mg/g of IOCSp, respectively. A filter packed with small amount of 25 g IOCSp maintained a consistent arsenic removal efficiency of 95% from synthetic solution containing arsenic concentration of as high as 1000g/L. This produced a throughput volume of 153 and 178 L of water containing As III) and As(V), respectively before any need for regeneration or disposal of IOCSp. IOCSp could be regenerated by washing it with NaOH solution. The dynamic (column) adsorption kinetics were successfully predicted by the Thomas and Nikolaidis modified models.
Shon, H., Phuntsho, S., Vigneswaran, S., Kandasamy, J.K., Kim, J.B., Park, H.J. & Kim, I.S. 2010, 'PVDF-TiO2 Coated microfiltration membranes: preparation and characterization', Membrane Water Treatment, vol. 1, no. 3, pp. 193-206.
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Organic fouling and biofouling pose a significant challenge to the membrane filtration process. Photocatalysis-membrane bybrid system is a novel idea for reducing these membranes fouling however, when TiO2 photocatalyst nanoparticles are used in suspension, catalyst recovery is not only imposes an extra step on the process but also significantly contributes to increased membrane resistance and reduced permeate flux. In this study, TiO2 photocatalyst has been immobilized by coating on the microfiltration (MF) membrane surface to minimize organic and microbial fouling. Nano-sized TiO2 was first synthesized by a sol-gel method. The synthesized TiO2 was coated on a Poly Vinyl Difluoride (PVDF) membrane (MF) surface using spray coating and dip coating techniques to obtain hybrid functional composite membrane. The characteristics of the synthesized photocatalyst and a functional composite membrane were studied using numerous instruments in terms of physical, chemical and electrical properties. In comparison to the clean PVDF membrane, the TiO2 coated MF membrane was found more effective in removing methylene blue (20%) and E-coli (99%).
Nguyen, V., Guo, W., Ngo, H. & Vigneswaran, S. 2010, 'A new combined inorganic-organic flocculant (CIOF) as a performance enhancer for aerated submerged membrane bioreactor', Separation and Purification Technology, vol. 75, no. 2, pp. 204-209.
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In this study, a new combined inorganicorganic flocculant (CIOF) of FeCl3 and membrane performance enhancer (MPE50) was prepared and added to an aerated submerged membrane bioreactor (SMBR). The effects of CIOF on the performance of an aerated submerged membrane bioreactor (SMBR) were evaluated. The results indicated that the SMBR with CIOF addition could remove almost 100% total phosphate while eliminating over 90% ammonia (NH4-N) and dissolved organic carbon (DOC) during an 80-day of operation. The respiration tests revealed that the specific oxygen uptake rate (SOUR) was stable around 1.52.0mgO2/gMLVSS h. The sludge volume index (SVI) of less than 100 mL/g during the operation showed the importance of CIOF on the improvement of settling properties of the sludge. Soluble carbohydrate concentration was also well correlated with DOC of the supernatant. CIOF was successful in the reduction of fouling of membrane as the membrane was only chemically cleaned after 53 days of operation.
Mohammed Abdul, J., Vigneswaran, S., Shim, W.G. & Kandasamy, J.K. 2010, 'Removal of metsulfuron methyl by granular activated carbon adsorption', Desalination and Water Treatment, vol. 21, no. 1-3, pp. 247-254.
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The removal of metsulfuron methyl (MSM) from aqueous solution (a sulfonyl urea herbicide) was investigated by adsorption both in batch and fixed bed processes. Coal based granular activated carbon (GAC) was used as an adsorbent. The adsorption equilibrium, isotherms and kinetics of MSM were studied and the data was fitted into various mathematical models. The adsorption equilibrium was fitted by Langmuir and Freundlich isotherms. Homogeneous surface diffusion model (HSDM) kinetic equation with Langmuir and Freundlich adsorption isotherm model was successfully applied to predict the adsorption kinetics data for various concentrations of MSM. The average mass transfer coefficients (kf) were 2.125 105 and 2.198 105 m/s with the Langmuir and Freundlich adsorption isotherm model, respectively. The Bohart-Adams, Thomas, and Yoon and Nelson empirical models were attempted to fit long term column adsorption data. Overall, the Thomas model was found to best simulate the fixed bed adsorption of MSM.
Chanan, A.P., Vigneswaran, S., Kandasamy, J.K. & Shon, H. 2010, 'Chemical-assisted physico-biological water mining system', Institution of Civil Engineers. Proceedings. Water Management, vol. 163, no. 9, pp. 469-474.
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Water mining is the process of extracting valuable water from a sewerage network by treating raw sewage to high standards. A range of commercially viable water mining treatment technologies are now available to treat sewage to specified water quality targets. Most of these technologies have minimal plant footprint requirements, making them suitable for decentralised operations. This paper discusses a hybrid water mining system that includes chemically assisted fine solids separation followed by a biological treatment process. Results from the first proof testing of this water mining system in Sydney, Australia are presented. The results confirm the suitability of the hybrid system for producing high-quality water for non-potable reuse.
Johir, M.H., Vigneswaran, S. & Kandasamy, J.K. 2010, 'Hybrid filtration method for pre-treatment of stormwater', Water Science And Technology, vol. 62, no. 12, pp. 2937-2943.
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In this study the hybrid filtration process (combining fibre filter with deep bed dual media filtration) was investigated as pre-treatment to stormwater. This process was investigated in-terms of reduction in turbidity, dissolved organic carbon (DOC), colour, headloss development across the filters, suspended solids removal, organic matter removal, nutrients and heavy matter (such as iron, copper, lead, zinc) removal efficiency. A comparison was made between the hybrid filter with single media (sand) deep bed filter and fibre filter. It was found that the hybrid filtration system successfully removed turbidity (98%), colour (99%), suspended solids (99%), and DOC (55%). The removal efficiency of heavy metal was relatively low as the concentration of heavy metals present in stormwater was low. The removal efficiency of nitrate, nitrite and phosphorous (as orthophosphate) was 27, 35 and 72% respectively. Hybrid filtration processes showed a better reduction of Modified Fouling Index (MFI) value (from 15.500 s/l2 to 9 s/l2) compared with single media sand, anthracite and fibre filter which were 35 s/l2, 13 s/l2 and 14 s/l2 respectively when operated at FeCl3 dose of 15 mg/l.
Phuntsho, S., Dulal, I., Yangden, D., Tenzin, U., Herat, S., Shon, H. & Vigneswaran, S. 2010, 'Studying Municipal Solid Waste Generation And Composition In The Urban Areas Of Bhutan', Waste Management & Research, vol. 28, no. 6, pp. 545-551.
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Bhutan lacks the solid waste data which are essential parameters for planning and scheduling of municipal solid waste management (MSWM) systems. The first ever large-scale research survey on solid waste generation and characterization in the urban areas
Ho, D., Senthilnanthan, M., Mohammad, J., Vigneswaran, S., Ngo, H., Mahinthakumar, G. & Kandasamy, J.K. 2010, 'The Application Of Photocatalytic Oxidation In Removing Pentachlorophenol From Contaminated Water', Journal of Advanced Oxidation Technologies, vol. 13, no. 1, pp. 21-26.
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The degradation of sodium salt of pentachlorophenol (PCPS) by photocatalysis with titanium dioxide (TiO2) as the catalyst was investigated. The residual PCPS after photo-degradation was analyzed by high performance liquid chromatograph (HPLC) while the c
Aryal, R., Vigneswaran, S., Kandasamy, J.K., Baral, B. & Grasmick, A. 2010, 'Influence of aeration and permeate flux on deposition of particulates on membrane surface', Water Science & Technology: Water Supply, vol. 10, no. 6, pp. 979-986.
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In microfiltration, a deposit of foulant tends to form on the membrane surface and this usually controls the performance of the filtration process. This paper discusses the influence of physical parameters such as aeration and permeates flux on migration and deposition of above micron particles on the membrane surface. Kaolin clay suspension of particle 3.7&acirc;8 mm with mean particle diameter 4.1 mm was used in this study. Equal amount of mass of deposited particles on the membrane surface created different transmembrane pressure (TMP) when operated at different aeration rates and permeate flux showing that there is a composite effect. The particle deposition rate at the beginning at lower flux was almost linear which changed to a sharp logarithamic rise at higher flux. The difference in TMP rise for the same amount of deposit demonstrated the selective nature of particle deposition. The mass of the particle deposition on the membrane surface could be described by two parameters: maximum deposition and time using a simple empirical logarithamic equation y=k/[1+exp(b-at)], where k, a, and b are constant; y is the particulate mass deposit (g/m2) and t is the time. The maximum particle mass deposition growth could be described by the equation dy/dt=1/4ka.
Senthilnanthan, M., Ho, D., Vigneswaran, S., Ngo, H. & Shon, H. 2010, 'Visible light responsive ruthenium-doped titanium dioxide for the removal of metsulfuron-methyl herbcide in aqueous phase', Separation and Purification Technology, vol. 75, no. 3, pp. 415-419.
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Titanium dioxide (TiO2) under UV light irradiation is one of the effective treatment methods to reduce the concentration of synthetic organic compounds in water. Nevertheless, only a small amount of UV light is absorbed in the solar light. This makes the less use of TiO2 for environmental applications. In this study, we prepared Ru-doped visible light responsive (VLR) TiO2 to improve visible light absorption and characterized it in terms of physical and chemical properties. The photocatalytic activity of VLR Rudoped TiO2 was investigated to remove metsulfuron-methyl (MSM) in aqueous phase. The Ru-doped TiO2 at different Ru concentrations was found to have the anatase phase. The undoped and Ru-doped TiO2 consisted of regular round shape. The photocatalytic activity of VLR photocatalyst was significantly improved on the addition of Ru from 40% for undoped TiO2 to 80% for Ru-doped TiO2. The removal efficiency of MSM was proportional to the increasing Ru-doped TiO2 under visible light. As the calcined temperature increased from 300 to 900 &acirc;&brvbar;C, the degradation efficiencies moderately changed from 65 to 90%. However, the effect of calcination duration was marginal on the photodegradation of MSM.
El Saliby, I., Shon, H., Okour, Y., Vigneswaran, S., Senthilnanthanan, M. & Kandasamy, J.K. 2010, 'Production of Titanium Dioxide Nanoparticles and Nanostructures from Dye Wastewater Sludge - Characterisation and Evaluation of Photocatalytic activity', Journal of Advanced Oxidation Technologies, vol. 13, no. 1, pp. 15-20.
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Producing a useful catalyst (TiO2) from sludge is possible after the incineration of sludge produced from the flocculation of wastewater by Ti-salts. In this study, TiO2 was successfully produced from dye wastewater sludge. Titanate nanotubes and nanoaggregates were produced through alkaline-hydrothermal and hydrogen peroxide treatments, respectively. Catalysts were characterised using scanning electron microscope and BET surface measurement. The photocatalytic activity was monitored for the photodegradation of organics in synthetic wastewater (SWW) and the photodecomposition of gas acetaldehyde. Nanotubes with a high surface area of 155.83 m2/g were obtained by alkaline-hydrothermal treatment, while lower surface area (65.22 m2/g) nanoaggregates were synthesized after hydrogen peroxide treatment. In general, nanoparticles, nanotubes and nanoaggregates showed mild photocatalytic activity. All catalysts showed similar photocatalytic activity for the photodecomposition of organics in SWW and the photodecomposition of acetaldehyde.
Aryal, R., Vigneswaran, S., Kandasamy, J.K. & Naidu, R. 2010, 'Urban stormwater quality and treatment', Korean Journal Of Chemical Engineering, vol. 27, no. 5, pp. 1343-1359.
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Stormwater runoff from urban and suburban areas generates numerous pollutants. The areas include residential areas, parks, commercial areas, industrial areas and road/highways. Land use and human activities largely determine the nature and level of pollutants. Among the various types of pollutants that can contribute to adverse water quality impact in receiving water bodies, of concern are suspended solids, heavy metals, polycyclic aromatic hydrocarbons and nutrients. This paper provides a critical review of the characteristics and sources of urban stormwater pollutants and the manner in which the pollution occurs. Treatment systems for urban stormwater runoff and for urban stormwater harvesting are discussed.
Chang, Y., Chang, J., Chen, C., Chiemchaisri, C. & Vigneswaran, S. 2010, 'An innovative attached-growth biological system for purification of pond water', Bioresources Technology, vol. 101, no. 5, pp. 1506-1510.
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This study applied the non-woven material from used diaper as the carrier for bio-film process to purify the recycled water from a landscape pond at the Tainan City Municipal Culture Center (TCMCC), Taiwan. An on-site system was installed and the experiment was accomplished through three stages in 192 days with different time periods of 70 days, 63 days, and 59 days, respectively. The results showed that the non-woven media is functional for SS removal. The average SS removal of stages 1, 2, and 3 were 91%, 96%, and 95%, respectively. The highest SCOD removal efficiency of 90% occurred at stage 3. A significant color improvement of the pond water was achieved through this non-woven bio-carrier treatment system. Whole system can be without any maintenance for 139 days. The result indicated that the non-woven medium system was with a great potential in treating and recycling the pond water with stable operation and satisfactory removal performance.
Kus, B.G., Kandasamy, J.K., Vigneswaran, S. & Shon, H. 2010, 'Water quality characterisation of rainwater in tanks at different times and locations', Water Science and Technology, vol. 61, no. 2, pp. 429-439.
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Rainwater collected from ten domestic roofs in Sydney and from one in Wollongong, a town south of Sydney, Australia was analysed to determine the water quality and to compare against the Australian Drinking Water Guidelines (ADWG) to determine its suitability as a potable water supply. The pollutants analysed were 13 heavy metals, 8 salts & minerals, pH, ammonia, orthophosphate, conductivity, water hardness, turbidity, total suspended solids, Total dissolved salts & Bicarbonate. The results indicate that the rainwater tested complied to most of the parameters specified in the ADWG. Molecular weight distribution of organic matter from one of the domestic rainwater tanks was analysed in terms of the effects of aging and roof contact. Molecular weight distribution of organic matter in rainwater showed prominent peaks at 37,500 daltons may be due to biopolymers, 850 Da to humic substances, 500 Da to building blocks, 220 Da to low MW acids, and less than 220 Da to amphiphilics. The findings also indicate that the first flush volumes that by-passed the tank can have a significant influence on the water quality in the rainwater tank.
Chanan, A.P., Vigneswaran, S. & Kandasamy, J.K. 2010, 'Valuing stormwater, rainwater and wastewater in the soft path for water management: Australian case studies', Water Science And Technology, vol. 62, no. 12, pp. 2854-2861.
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A Water Sensitive City is now commonly acknowledged best practice for designing the cities of the future. In Australia, the National Water Initiative has allocated high priority towards offering insight into successful water sensitive urban development projects, to facilitate capacity building within the industry. This paper shares innovative water sensitive projects implemented at Kogarah City Council, in Sydney. Four key projects are discussed, demonstrating how stormwater, rainwater and wastewater can be incorporated into decentralised water systems to offer sustainable water management of the future. The case studies included in the paper highlight Kogarah&acirc;s journey towards the Soft Path for Water Management.
Shon, H.K., Vigneswaran, S., El Saliby, I., Okour, Y., Kim, I.S., Cho, J., Park, H.J., Kim, J.B. & Kim, J.-.H. 2010, 'Hydrogen production affected by Pt concentration on TiO2 produced from the incineration of dye wastewater flocculated sludge using titanium tetrachloride', DESALINATION AND WATER TREATMENT, vol. 15, no. 1-3, pp. 214-221.
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Mohammed Abdul, J., Vigneswaran, S., Shon, H., Areerachakul, N. & Kandasamy, J.K. 2009, 'Comparison of granular activated carbon bio-sorption and advanced oxidation processes in the treatment of leachate effluent', Korean Journal Of Chemical Engineering, vol. 26, no. 3, pp. 724-730.
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Ho, D., Vigneswaran, S. & Ngo, H. 2009, 'Photocatalysis - membrane hybrid system for organic removal from biological treated sewage effluent', Separation and Purification Technology, vol. 68, no. 2, pp. 145-152.
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The application of semiconductor photocatalysis in treating wastewater has attracted growing interest due to its complete mineralisation of organic matter. Furthermore, coupling of photocatalytic process with microfiltration provided considerable advantages over the conventional methods. In this study, the photocatalytic reactivity of the catalysts was assessed at different operating conditions. The results show that the dissolved organic carbon (DOC) content was halved at a concentration of 1.0 g/L of TiO2. With the addition of flocculant FeCl3, the oxidation process was significantly improved further by another 30%. The recovery of TiO2 upon photooxidation process was achieved by coupling the photocatalysis reactor with a low energy submerged membrane reactor. The results show superior DOC degradation of more than 80% by this hybrid system. Moreover, it was demonstrated that photosensitization with TiO2/UV could effectively reduce membrane fouling and enhance the permeate flux of the submerged membrane reactor.
Nguyen, V., Vigneswaran, S., Ngo, H., Shon, H. & Kandasamy, J.K. 2009, 'Arsenic removal by a membrane hybrid filtration system', Desalination, vol. 236, no. 1-3, pp. 363-369.
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Arsenic is a toxic semi-metallic element that can be fatal to human health. Membrane filtration can remove a number of contaminants from water, including arsenic. Removal of arsenic by membrane filtration is highly dependent on the species of arsenic and the properties of the membrane. The performance of the nanofilter is better for removing As(V) than As(III). About 57% of As(III) and 81% of As(V) was removed from 500 mg/L arsenic solutions by nanofiltration (NTR729HF, Nitto Denko Corp., Japan) of 700 molecular weight (MW) cutoff. The removal efficiency of microfiltration (MF) was much lower than that of nanofiltration (NF) due to its larger pore size. By comparison only 37% of As(III) and 40% of As(V) were removed by microfiltration (PVA membrane, Pure-Envitech, Korea). However, the removal efficiency of microfiltration was increased dramatically when a small amount of nanoscale zero valent iron (nZVI) was added. The removal efficiency by MF increased up to 90% with As(V) and 84% with As(III) when an amount of 0.1 g/L of nZVI was added into the arsenic solution.
Shon, H., Vigneswaran, S., Zareie, H.M., Ben Aim, R., Lee, E., lee, J., Cho, J. & Kim, I.S. 2009, 'Physico-chemical pretreatment to Seawater Reverse Osmosis (SWRO): Organic Characterization and Membrane Autopsy', Desalination, vol. 236, no. 1 - 3, pp. 282-290.
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In this study, different pretreatment methods such as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), powdered activated carbon (PAC) adsorption and ferric chloride (FeCl3) flocculation were evaluated in terms of their capability in removing seawater organic matter (SWOM) and the characteristics of the foulants on the seawater reverse osmosis (SWRO) membranes. A detailed experiment with a crossflow SWRO filtration unit was conducted with SR membrane (MWCO 100 Da) at 60 bar with seawater (conductivity = 48.9 mS/cm) drawn from south-western Korea. The SWOM removal by UF, NF, PAC adsorption and FeCl3 flocculation was 20.3, 28.9, 46 and 23.3%, respectively. SWOM used in this study predominantly consisted of small size organic matter (<1000 Da). A large amount of the hydrophobic fraction present in SWOM was removed by PAC adsorption. The SDI5min significantly decreased from 12.7 (without any pretreatment) to 3.2 (MF), 1.3 (UF), 1.0 (NF) and 4.4 (PAC adsorption). RO filtration of seawater with and without pretreatment showed significant flux decline (normalized flux decline (J/J0) = 0.17 &plusmn; 0.02) within 20-h operation. The elemental analyses made on the RO surface after direct RO filtration showed that the relative fraction of the carbon decreased, while sodium (Na), magnesium (Mg), chlorine (Cl) and iron (Fe) elements were found in the foulants extracted from the fouled membrane surface. The average roughness of the clean membrane surface was 41.5 nm. After MF and UF pretreatment, the roughness slightly increased to 54.8 and 55.6 nm, respectively. On the other hand, without any pretreatment, with PAC adsorption and with FeCl3 flocculation, the roughness increased up to 69.7, 66.4 and 110 nm, respectively. It can be concluded that the pretreatment by MF and UF could relatively preserve the RO membrane surface.
Mohammed Abdul, J., Chinu, K.J., Shon, H. & Vigneswaran, S. 2009, 'Effect of pre-treatment on fouling propensity of feed as depicted by the modified fouling index (MFI) and cross-flow sampler-modified fouling index (CFS-MFI)', Desalination, vol. 238, no. 1-3, pp. 98-108.
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The effectiveness of different pretreatment on the fouling propensity of the feed was studied using synthetic wastewater. The fouling potential of the feed was characterized by the standard modified fouling index (MFI) and cross-flow sampler modified fouling index (CFSMFI). In CFSMFI, a cross-flow sampler was used to simulate the condition of a cross-flow filtration. The results indicated that the pretreatment such as flocculation with an optimum dose of 68 mg/l FeCl3 substantially reduced the fouling propensity of the feed. The standard MFI of flocculated wastewater was reduced by around 99% compared to that of the untreated wastewater. Similarly, the adsorption with powdered activated carbon (PAC) of 1 g/l reduced the standard MFI value to more than 99% compared to that of the untreated wastewater. The CFSMFI values were lower than the standard MFI values for both treated and untreated wastewater, suggesting that the standard MFI was overestimated. The overestimation of the standard MFI compared to that of the CFSMFI value was more than 99%. The effect of molecular weight distribution (MWD) of the foulants in the wastewater on the fouling propensity of the feed was investigated. The MWD was correlated with the MFI and CFSMFI indices. It yielded useful insights in understanding the effect of MW on MFI and CFSMFI and fouling propensity of the feed.
Aryal, R., Legegue, J., Vigneswaran, S., Kandasamy, J.K., Heran, M. & Grasmick, A. 2009, 'Identification and characterisation of biofilm formed in membrane bioreactor', Separation and Purification Technology, vol. 67, no. 1, pp. 86-94.
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Experiments were conducted in a laboratory scale membrane bio-reactor (MBR) system equipped with a side stream flat sheet membrane. Six runs lasting different durations (2, 4, 6, 9, 15 and 20 days) were conducted at an aeration rate of 2 m3 h-1 m-2 to understand the temporal variation of chemistry of foulant that attached on the membrane surface. The foulant attached on the membrane surface was extracted with 0.5% (v/v) NaOH solution and the extract was analysed using fluorescent spectroscopy and size exclusion chromatography. Variation of low- and high-molecular weight substances with evolution of time was compared. The results showed that the nature of foulant changed with the evolution of time. Four runs conducted for a short duration (2, 4, 6 and 9 days), low-molecular weight substances were dominant in the foulant whereas for long duration runs (15 and 20 days), high-molecular weight substances were mainly observed. Moreover, the foulant close to the membrane surface contained mainly protein and soluble microbial by-products.
Aryal, R., Kandasamy, J.K., Vigneswaran, S., Naidu, R. & Lee, S.H. 2009, 'Review of Stormwater quality, Quantity and Treatment Methods Part 1', Environmental Engineering Research, vol. 14, no. 2, pp. 71-78.
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A review of stormwater quantity and quality in the urban environment is presented. The review is presented in three parts. The first part reviews the mathematical methods for stormwater quantity and has been undertaken by examining a number of stormwater models that are in current use. The important feature of models, their applications, and management has been discussed. Different types of stormwater management models are presented in the literatures. Generally, all the models are simplified as conceptual or empirical depending on whether the model is based on physical laws or not. In both cases if any of the variables in the model are regarded as random variables having a probability distribution, then the model is stochastic model. Otherwise the model is deterministic (based on process descriptions). The analytical techniques are presented in this paper.
Lee, J., Johir, J., Chinu, K.J., Shon, H., Vigneswaran, S., Kandasamy, J.K., Kim, C.W. & Shaw, K. 2009, 'Hybrid filtration method for pre-treatment of seawater reverse osmosis (SWRO)', Desalination, vol. 247, no. 1-3, pp. 15-24.
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Hybrid processes combining fi bre fi lter with deep bed fi ltration process such as (i) fi bre fi lter and sand fi lter, (ii) fi bre fi lter and anthracite and (iii) fi bre fi lter and dual media fi lter were investigated as pre- treatments to SWRO. Seawater was drawn from Chowder Bay, Sydney. The eff ect of diff erent pretreatment hybrid systems was investigated in terms of silt density index (SDI10), modifi ed fouling index (MFI), headloss across the fi lters and reduction in turbidity and dissolved organic carbon (DOC). The in-line fl occulation in fi bre fi lter improved the performance of the pretreatment hybrid system as measured by the MFI, SDI10, headloss, turbidity and DOC removal. The lowest SDI10 and MFI were found with a fi bre fi lter operated at a fi ltration velocity of 40 m/h followed by dual media fi lter operated at a fi ltration velocity of 5 m/h. The lowest headloss and turbidity was found with a fi bre fi lter operated at a fi ltration velocity of 40 m/hr followed by anthracite operated at a fi ltration velocity of 5 m/h. This system also gave an effl uent with the lowest DOC of 0.64 mg/L corresponding to a removal effi ciency of about 70%.
El Saliby, I., Okour, Y., Shon, H., Vigneswaran, S., Kandasamy, J.K. & Kim, J.H. 2009, 'Detailed Investigation on the Effect of Washing TiO2 Prepared from Ti-salts Flocculated Wastewater Sludge', Journal of Advanced Oxidation Technologies, vol. 12, no. 2, pp. 194-201.
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In this study, the effect of washing TiO2 produced from flocculated sludge was investigated. Produced TiO2 was washed with HCl, NaOH and Milli-Q-water and the washed TiO2 was then characterized in terms of X-ray diffraction imaging, scanning electron microscope/energy dispersive using X-ray analysis and surface area. Washed TiO2 was tested for adsorption and photocatalytic oxidation of acetaldehyde, and the decomposition of organics from synthetic wastewater (SWW) in terms of total organic carbon (TOC) and absorbance at UV-254. Results revealed that the anatase structure was dominant and TiO2 was mainly doped with C atoms. The surface area of TiO2 generated form TiCl4 flocculation was found to be twice larger than the TiO2 generated from Ti(SO4)2 flocculation. Acid and base washings of TiO2 improved its photocatalytic ability in decomposing acetaldehyde under UV-irradiation. Similarly, acid, base and Milli-Q water washings of TiO2 were better in reducing TOC and humic acids from SWW.
Lee, B., Kim, S.H., Shon, H., Vigneswaran, S., Kim, S.H., Cho, J., Kim, I., Choi, K., Kim, J.K., Park, H.J. & Kim, J.K. 2009, 'Aquatic toxicity evaluation of TiO2 nanoparticle produced from sludge of TiCl4 flocculation of wastewater and seawater', Journal of nanoparticle Research, vol. 11, no. 8, pp. 2087-2096.
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Flocculation using titanium tetrachloride (TiCl4) as a coagulant is an efficient and economical application because the flocculated sludge can be recycled to produce a valuable byproduct, namely titanium dioxide (TiO2) nanoparticles. However, toxicity of TiCl4 has not yet been assessed while it is used in water treatment. The aquatic toxicity of TiCl4 flocculation process was investigated to assess the environmental safety of the coagulant. D. magna and V. fischeri bioassays were carried out to evaluate the supernatant toxicity after TiCl4 flocculation. Artificial wastewater, biologically treated sewage effluent, and seawater were used to study the toxicity of TiCl4 flocculation. Results showed that supernatant toxicity was very low when TiCl4 flocculation was conducted (no observed effect concentration = 100 mg/L and lowest observed effect concentration = 150 mg/L exposed to D. magna and V. fischeri, respectively). Similarly, TiO2 nanoparticles recovered from wastewater and seawater flocculated sludge were also found to have low toxicity. The regenerated TiO2 nanoparticles indicated low toxicity values when compared to the commercial-TiO2 nanoparticle, P-25.
Chiemchaisri, C., Passananon, S., Ngo, H. & Vigneswaran, S. 2009, 'Simultaneous removal of particles and dissolved organic matter in floating media filter for surface water treatment', Desalination and Water Treatment, vol. 11, no. 1-3, pp. 109-114.
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This research investigated the performance of fl oating media fi lter in removing particles and dissolved organic matter from surface water. Pilot-scale study consists of fl oating plastic media pre-fi lter connected with either granular activated carbon (GAC) or sponge biological fi lter (BF) bed. In the fl oating plastic media fi lter, coagulation and fl occulation processes using poly-aluminum chloride (PACl) as coagulant at an optimum dose of 8 mg/L helped removing particles from raw water. The fl oating media fi lter was operated a fi ltration rate of 11 m3/m2.h whereas those in GAC and BF units were maintained at 2 m3/m2.h. Continuous operation for over 120 days gave 98% and 99% average removal effi ciencies of turbidity and UV254 in fl oating media fi lter in combination with GAC unit whereas and 78% and 52% removal effi ciencies of turbidity and UV254 removal were obtained in fl oating media fi lter in combination with BF. The removal of dissolved organic carbon in GAC and BF units reduced chlorine demand for disinfection by 29% and 14%. It could also reduce the sum of trihalomethane (THMs) ratio from 1.1 to 0.1 and 0.5 respectively.
Johir, M.H., Chinu, K.J., Vigneswaran, S. & Shon, H. 2009, 'In-line flocculation - filtration as pre-treatment to reverse osmosis desalination', Desalination, vol. 247, no. 1-3, pp. 85-93.
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In this paper the performance of single and dual media filters with in-line flocculation have been examined as pretreatment to seawater reverse osmosis (SWRO). A comparison of filter performance was made between single medium filter (80 cm) consisting of sand or anthracite, and dual media filter consisting of sand (40 cm at the bottom) and anthracite (40 cm on top). Short term (6 hours) experiments were conducted with in-line coagulation followed by direct filtration. Filtration velocities of 5 m/h and 10 m/h were used. The performances of these filters were assessed in terms of turbidity removal, head loss build-up, and organic compound removal in terms of molecular weight distribution (MWD). The efficiency of the filter as pretreatment was evaluated in terms of silt density index (SDI) and modified fouling index (MFI). It was found that the turbidity removal was high and all the filters produced more or less same quality water. There was a slower buildup of head loss for coarser filter medium. A post treatment of reverse osmosis after an inline-flocculation-dual media filtration showed lower normalized flux decline (J/J0) (0.35 to 0.22 during the first 20 hours operation) while, seawater without any pretreatment showed steeper flux decline (0.18 to 0.11 at first 20 hours operation) in RO.
Okour, Y., El Saliby, I., Shon, H., Vigneswaran, S., Kim, J.H., Cho, J. & Kim, I.S. 2009, 'Recovery of sludge produced from Ti-salt flocculation as pretreatment to seawater reverse osmosis', Desalination, vol. 247, no. 1-3, pp. 53-63.
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In this study, titanium tetrachloride (TiCl4), titanium sulfate (Ti(SO4)2) and ferric chloride (FeCl3) flocculation as a pretreatment to seawater reverse osmosis (SWRO) were investigated. Their ability to remove turbidity, seawater organic matter (SWOM) and controlling the feed water quality of SWRO was evaluated. Flux decline of SWRO and membrane autopsy were studied. Titanium dioxide (TiO2) produced from sludge after Ti-salt fl occulation was characterized in terms of particle structure and photocatalytic activity. A hybrid system of fl occulation followed by granular activated carbon (GAC) filtration was employed to remove the suspended micro-flocs after diff erent fl occulations. The optimum dose of 10 mg/L TiCl4 and FeCl3 were used. The turbidity removal for the three coagulants was marginal at different doses at pH 6 and 8. Flocculation followed by GAC fi ltration signifi cantly reduced the turbidity values from 1.5 NTU to about 0.35 NTU using TiCl4 and 0.40 using FeCl3. Silt density index (SDI15) was also decreased from 5.0 to 4.2 and 4.7, respectively. Removal of dissolved organic carbon (DOC), colour and UV absorbance after TiCl4 and FeCl3 flocculation followed by GAC fi ltration was found to be eff ective and similar. TiO2 produced from sludge showed very high photocatalytic activity under UV-irradiation. Acetaldehyde was completely removed after 45 min photocatalytic reaction
Shon, H., Vigneswaran, S., Kandasamy, J.K., Kim, J.B., Park, H.J., Choi, S. & Kim, J.H. 2009, 'Preparation of titanium oxide, iron oxide, and aluminium oxide from sludge generated from Ti-salt, Fe-salt and Al-salt flocculation of wastewater', Journal of Industrial and Engineering Chemistry, vol. 15, no. 5, pp. 719-723.
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In this study, the settled floc (sludge) produced by aluminum sulfate (Al2(SO4)3), ferric chloride (FeCl3) and titanium tetrachloride (TiCl4) flocculation was recycled with a novel flocculation process, which has a significant potential to the lower cost of waste disposal, protect the environment and public health and yield economically useful by-products. Three coagulants removed 70% of organic matter in synthetic wastewater. The settled floc was incinerated in the range from 100 8C to 1000 8C. Alumina (Al2O3), hematite (Fe2O3), titanium oxide (TiO2) which are the most widely used metal oxides were produced from the wastewater sludge generated by the flocculation in wastewater with Al2(SO4)3, FeCl3 and TiCl4, respectively. TiO2 particles produced from the sludge consisted of the large amount of nano size particles. Hematite (Fe2O3) and grattarolaite (Fe3 (PO4)O3 or Fe3PO7) included the majority of micro size (40%) particles. Alumina (Al2O3) also consisted of micro size (40%). Due to TiO2 usefulness of the application, detailed characterisation of TiO2 after calcination at different temperatures were investigated in terms of X-ray diffraction, energy dispersive X-ray, surface area and photoactivity.
Nguyen, V., Nguyen, T., Pham, T.L., Vigneswaran, S., Ngo, H., Kandasamy, J.K., Nguyen, H. & Nguyen, T.D. 2009, 'Adsorption and removal of arsenic from water by iron ore mining waste', Water Science and Technology, vol. 60, no. 9, pp. 2301-2308.
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There is a global need to develop low-cost technologies to remove arsenic from water for individual household water supply. In this study, a purified and enriched waste material (treated magnetite waste, TMW) from the Trai Cau's iron ore mine in the Thai Nguyen Province in Vietnam was examined for its capacity to remove arsenic. The treatment system was packed with TMW that consisted of 75% of ferrous-ferric oxide (Fe3O4) and had a large surface area of 89.7 m2/g. The experiments were conducted at a filtration rate of 0.05 m/h to treat groundwater with an arsenic concentration of 380 mg/L and iron, manganese and phosphate concentrations of 2.07 mg/L, 0.093 mg/L and 1.6 mg/L respectively. The batch experimental results show that this new material was able to absorb up to 0.74 mg arsenic/g. The results also indicated that the treatment system removed more than 90% arsenic giving an effluent with an arsenic concentration of less than 30 mg/L while achieving a removal efficiency of about 80% for Mn2 + and PO43-. This could be a promising and cost-effective new material for capturing arsenic as well as other metals from groundwater
Guo, W., Ngo, H., Vigneswaran, S., Dharmawan, F., Nguyen, V. & Aryal, R. 2009, 'Effect of different flocculants on short-term performance of submerged membrane bioreactor', Separation and Purification Technology, vol. 70, no. 3, pp. 274-279.
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This study aims at evaluating the impacts of flocculant addition to a submerged membrane bioreactor (SMBR). Three types of common flocculants (FeCl3, PACl and chitosan) were tested based on the performance of organic and nutrients removal, respiration test and fouling control. The data showed that all of the flocculants not only could keep high removal efficiencies of DOC and COD (>90%) compared to SMBR alone, but also exhibited different advantages and disadvantages according to the properties of the flocculants. For instance, inorganic flocculants strongly affected the nitrification process and organic flocculant addition slightly reduced the phosphorus removal efficiency in SMBR. After adding FeCl3 and PACl, NH4-N removal decreased to 31.9% and 11.1%, while T-N removal dropped to 22% and 0.5% respectively. Although flocculants addition improved sludge settleability and oxygen transfer to some extent, organic flocculant obtained more stable sludge volume indexes (SVI) and specific oxygen uptake rates (SOUR) than those of inorganic flocculants. Inorganic flocculants, on the other hand, led to more reduction of soluble microbial products (SMP) present in mixed liquor and lower membrane fouling rates (1.3 and 2.6 kPa/day for FeCl3 and PACl respectively).
Aryal, R., Kandasamy, J.K., Vigneswaran, S., Naidu, R. & Lee, S. 2009, 'Review of Stormwater Quality, Quantity and Treatment Methods Part 2: Stormwater: Quality Modelling', Environmental Engineering Research, vol. 14, no. 3, pp. 143-149.
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In this paper, review of stormwater quality and quantity in the urban environment is presented. The review is presented in three parts. This second part reviews the mathematical techniques used in stormwater quality modelling and has been undertaken by examining a number of models that are in current use. The important features of models are discussed.
Chanan, A.P., Kandasamy, J.K., Vigneswaran, S. & Sharma, D. 2009, 'A gradualist approach to address Australia's urban water challenge', Desalination, vol. 249, no. 3, pp. 1012-1016.
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There is growing consensus worldwide against the conventional centralised approach to water management, and a &acirc;soft path&acirc; for water management has emerged as a sustainable alternative. A &acirc;soft path&acirc; for water management emphasizes the optimization of end-use efficiency, small-scaled management systems, incorporates fit-for-purpose water use, and recommends the use of diverse, locally appropriate and commonly decentralised infrastructures. However, large-scale desalination plants are currently being built for almost all metropolitan centres in Australia to ensure water supply security. Unlike &acirc;soft path&acirc; for water management, large-scale desalination plants embody the traditional urban water supply approach. In spite of knowledge and values relating to the water cycle having shifted towards &acirc;soft path&acirc;, the old organisational framework is believed to be hindering its adoption. Perhaps, therefore major water utilities in recent times have opted for the ideologically easier option of large-scale desalination conforming to the existing framework, instead of choosing a &acirc;soft path&acirc; for water management with potential for decentralised management. This paper critically reviews the urban water management direction in metropolitan Australia and puts forward a &acirc;gradualist approach&acirc;. It incorporates a comprehensive non-potable water reuse program necessary to build the familiarity and trust in water reuse, as a first step before introducing the idea of potable reuse.
Shon, H., Vigneswaran, S., Kandasamy, J.K., Zareie, H.M., Kim, J.B., Cho, D.L. & Kim, J.H. 2009, 'Preparation and Characterisation of Titanium Dioxide (TiO2) from Sludge produced by TiCl4 Flocculation with FeCl3, Al2(SO4)3 and Ca(OH)2 Coagulant Aids in Wastewater', Separation Science and Technology, vol. 44, no. 7, pp. 1525-1543.
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In this study, TiCl4 coagulant together with coagulant aids such as FeCl3, Al2(SO4)3, and Ca(OH)2 were investigated to improve the photoactivity of titanium dioxide (TiO2) produced from sludge and to increase the resulting low pH value. After TiCl4 flocculation with three coagulant aids, the settled floc (sludge) was incinerated at 600&Acirc;&deg;C to produce TiO2 doped with Fe, Al, and Ca elements. Fe-, Al-, and Ca-doped TiO2 was characterized in terms of structural, chemical, and photo-electronic properties. All the coagulant aids used together with Ti-salt flocculation effectively increased the pH values. The surface area of TiO2-WO (without any coagulant aids), Fe/TiO2, Al/TiO2, and Ca/TiO2 was 122 m2/g, 77 m2/g, 136 m2/g and 116 m2/g, respectively. The TiO2-WO, Fe/TiO2, Al/TiO2, and Ca/TiO2 was found to be of anatase phase. The XRD pattern on the Fe/TiO2 included an additional peak of hematite (&Icirc;&plusmn;-Fe2O3). The majority of gaseous acetaldehyde with TiO2-WO and Ca/TiO2 for photocatalytic activity was completely removed within 40 minutes under UV irradiation.
Aryal, R., Lebegue, J., Shon, H., Vigneswaran, S., Kandasamy, J.K. & Grasmick, A. 2009, 'Temporal variation of foulant characteristics in membrane bioreactor', Desalination and Water Treatment, vol. 6, no. 1-3, pp. 69-73.
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Many studies have been performed to analyse the influence of compounds present in different fractions of the membrane foulants. The aim of this study was to reveal the changing chemistry of compounds present in membrane foulant with the evolution of time. Membrane fouling in a side stream membrane bioreactor (MBR) reactor was investigated. Constant flux filtration was employed in an MBR operation. Air bubbles were injected at 2 m3 h1 m2 for six different durations (2, 4, 6, 9, 15 and 20 days) of MBR operation. The foulant on the membrane surface was extracted using NaOH solution (5%) and analysed using fluorescent spectroscopy. The spectra showed the changing chemistry of foulant with the evolution of time. It showed low molecular weight substances such as amino acids and small aromatic proteins were dominant in the foulant at the beginning of the experiment but its concentration decreased with time. On the other hand BOD5 type substances concentration increased with time from the beginning of the experiment up to 9 days and there after decreased. The concentration of larger molecular weight soluble microbial by-products increased with evolution of time. Air bubbles at two aeration rate of 1m3 h1m2 and 2 m3 h1 m2 were also injected from the bottom of the membrane tanks to produce shear stresses on the membrane surface during 5 days of MBR operation to compare the effect of aeration in fouling propensity.
Zhang, R., Chinu, K.J., Vigneswaran, S. & Kandasamy, J.K. 2009, 'Submerged microfiltration coupled with physico-chemical processes as pretreatment to sea water desalination', Desalination and Water Treatment, vol. 11, no. 1-3, pp. 52-57.
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In this study, the critical fl ux of the submerged membrane system was experimentally evaluated when it was used for seawater with and without pre-treatment. In this study, different processes such as fl occulation with ferric chloride (FeCl3) and different doses of PAC adsorption were used as a pre-treatment. The pretreatment of fl occulant of 2 mg/L of FeCl3 and adsorption with the dose of 1 g/L PAC showed an improvement in the critical fl ux from 5 L/m2.h to 6.7 L/m2.h and 13.3 L/m2.h respectively. The performance of these pretreatments was also determined in terms of modifi ed fouling index using ultrafi lter membrane (UF-MFI). UF-MFI and SDI indicated that PAC adsorption was a better pretreatment than fl occulation for the seawater used in this study. Molecular weight distribution (MWD) of seawater organic matter was also examined after different pretreatments. MWD of the raw seawater was mainly in the range from 1510 to 130 Da. It is observed that FeCl3 fl occulation and PAC adsorption as pretreatments partially removed the organic matter of 1510 Da and 130Da respectively
Areerachakul, N., Kitiphatmontree, M., Kandasamy, J.K., Kus, B.G., Duangduen, C., Pivsa-Art, S. & Vigneswaran, S. 2009, 'Submerged Membrane System with Biofilter as a Treatment to Rain Water', Water, Air, & Soil Pollution: Focus, vol. 9, no. 5-6, pp. 431-438.
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Rainwater has been used as drinking water in Thailand for centuries especially in the rural parts and is accepted as an important water resource. From past to present, the quality of rainwater has changed with the landuse of the landscape, and its water quality is influenced by a diverse range of conditions such as the management of pollutant sources, the catchment condition, wind and meteorological conditions, and the location of rainwater collection points. In this study, the quality of rainwater collected off roofs at several locations was examined. Granular activated carbon (GAC) filtration was used as a pretreatment to microfiltration (MF) to remove the dissolved organic matter (DOC). After an initial adsorption period, the biofilm that formed on the GAC (biofilter) was found to remove DOC by up to 40%, 35%, and 15% for bed filter depths of 15, 10, and 5 cm, respectively. Biofilters also removed nitrate and phosphate by more than 80% and 35%. The hollow fiber membrane microfiltration with pore size of 0.1 &Icirc;&frac14;m was used to treat the effluent from biofiltration to remove the microorganisms/pathogens in the rainwater. Although there was no significant additional removal of DOC by MF, the biofilter removed all microorganisms. The use of biofilters as pretreatment to MF/UF could remove a higher amount of DOC, remove microorganisms, increase the membrane treatment efficiency, and reduce membrane fouling.
Johir, M.H., Lee, J., Vigneswaran, S., Kandasamy, J.K. & Shaw, K. 2009, 'Treatment of Stormwater using Fibre Filter Media', Water, Air, & Soil Pollution: Focus, vol. 9, no. 5-6, pp. 439-447.
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In this study, a high-rate fibre filter was used as a pre-treatment to stormwater in conjunction with in-line flocculation. The effect of operating the fibre filter with different packing densities (105, 115 and 125 kg/m3) and filtration velocities (20, 40, 60 m/h) with and without in-line flocculation was investigated. In-line flocculation was provided using 5, 10 and 15 mg/L of ferric chloride (FeCl3&Acirc;6H2O). The filter performance was studied in terms of pressure drop (&Icirc;P), solids removal efficiency, heavy metals (total) removal efficiency and total organic carbon (TOC) removal efficiency. It is found that the use of in-line flocculation at a dose of 15 mg/L improved the performance of fibre filter as measured by turbidity removal (95%), total suspended solids reduction (98%), colour removal efficiency (99%), TOC removal (reduced by 30&acirc;40 %) and total coliform removal (93%). The modified fouling index reduced from 750&acirc;950 to 12 s/L2 proving that fibre filter can be an excellent pre-treatment to membrane filtration that may be consider as post-treatment. The removal efficiency of heavy metal was variable as their concentration in raw water was small. Even though the concentration of some of these metals such as iron, aluminium, copper and zinc were reduced, others like nickel, chromium and cadmium showed lower removal rates
Johir, M.H., Vigneswaran, S. & Kandasamy, J.K. 2009, 'Deep bed filter as pre-treatment to stormwater', Desalination and Water Treatment, vol. 12, no. 1-3, pp. 313-323.
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This paper presents the results of experiments on the application of dual media and single media deep bed filters as pre-treatments to stormwater. In-line flocculation-filtration experiments were conducted with dual and single media filter. The single filter media (80 cm) consisted of either anthracite or sand, and the dual media filter consisted of sand (40 cm at the bottom) and anthracite (40 cm on top). Filtration velocities of 5 m/h, 10 m/h and 15 m/h were examined. The removal efficiency for turbidity, suspended solids and TOC was found to be 95%, 99% and 30&acirc;45% respectively at a flocculant dose of FeCl3 of 15 mg/L. The anthracite filter media showed a lower headloss development (26 cm, operated at 5 m/h filtration velocity with FeCl3 dose of 5 mg/L). The removal efficiency for nitrogen was lower than phosphorus which was relatively good (up to 50%). The removal efficiency for heavy metals such as Cd, Pb, Cr and Ni was found to be very low for all tested filtration systems because concentrations of these metals in the influent were also low. This filter can be used as a pretreatment to a membrane filter as the modified fouling index was reduced from 750 s/L2 (for stormwater) to 15 s/L2 (for filtered effluent). Detailed submerged membrane filter experiments conducted with pre-treated water showed that the membrane filter can be successfully be used as post-treatment to in-line flocculant-filter at a sustainable flux of 10 L/m2.h to remove the remaining solids and pathogens. An increase of air scouring in the membrane unit decreased the pressure development although it did not have any effect on increasing the critical flux beyond 10 L/m2.h.
Shon, H., Kim, S.H., Vigneswaran, S., Ben Aim, R.M., Lee, S. & Cho, J. 2009, 'Physicochemical Pretreatment Of Seawater: Fouling Reduction And Membrane Characterisation', Desalination, vol. 238, no. 1-3, pp. 10-21.
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The pretreatment of raw seawater is necessary to minimize the organic fouling of seawater reverse osmosis (SWRO) membranes. To predict the membrane fouling of the pretreated seawater, the modified fouling index (MFI) with ultrafiltration (UF) was investigated in terms of molecular weight distribution (MWD) and membrane characterization. The study was conducted with seawater drawn from Collioure, France. The concentration of total dissolved solids was 32,760 mg/L. The molecular weight (MW) of the initial seawater organic matter (SWOM) ranged from about 14160 Da to 280 Da. FeCl3 flocculation removed the majority of SWOM, while PAC adsorption could not remove the lowest MW fraction of organic matter (1110, 750 and 280 Da). The UF membranes with 30 kDa and 100 kDa MW cut-off removed the majority of of organic matter corresponding to the peaks 14,160 Da and 6560 Da in MWD. The MFI values obtained when using UF membranes of 30 kDa and 100 kDa with MF pretreatment were 19,700 s/L2 and 31,000 s/L2, respectively. The MFI values after pretreatments of FeCl3 flocculation and PAC adsorption significantly decreased to 6900 s/L2 and 6700 for 30 kDa UF and to 2300 s/L2 and 2500 s/L2 for 100 kDa UF, respectively. Some relation does exist for both membranes between the MFIUF values and Spb values obtained during the first peiod of filtration (pore blocking). The pore blocking zone significantly decreased after flocculation and adsorption pretreatment. This suggests that the pore blocking can be used as an indicator to predict membrane propensity. The detailed membrane characterization on the clean and fouled membrane surface after MFIUF experiments was made in terms of contact angle, zeta potential, functional group and microscopy.
Chinu, K.J., Johir, M.H., Vigneswaran, S., Shon, H. & Kandasamy, J.K. 2009, 'Biofilter as pretreatment to membrane based desalination: Evaluation in terms of fouling index', Desalination, vol. 247, no. 1-3, pp. 77-84.
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The removal of particulate matter and dissolved organic matter from seawater by the use of biofiltration was investigated. Granular activated carbon (GAC) and anthracite were used as biofilter media at two different filtration velocities. Filtrate quality was measured in terms of silt density index (SDI), modified fouling index (MFI) and turbidity removal. Reverse osmosis (RO) was used as a post-treatment. Both biofilters demonstrated similar fouling reduction behavior in terms of SDI and MFI. Fouling potential in terms of MFI values decreased to 10 s/L2 within the first 10&acirc;15 days of operation and kept constant up to the remaining experimental period of 55 days of operation for both GAC and anthracite biofilter. The filtrate turbidity was steady after 10 days and remained low at a value of 0.2&acirc;0.3 NTU and 0.28&acirc;0.31 NTU for anthracite and GAC biofilter, respectively. Furthermore, the headloss development was low and within 20 cm for biofilter operated at a low velocity of 5 m/h. A post-treatment of reverse osmosis after a pretreatment of GAC and anthracite biofilters showed a reduction in normalized flux decline (J/J0) from 0.22 to 0.12 and 0.35 to 0.21 during the first 20 h, respectively. The RO flux for seawater declined at a faster rate and continued even after 3 days when no pretreatment was provided.
Nguyen, V., Rahman, A., Vigneswaran, S., Ngo, H., Kandasamy, J.K., Nguyen, T.D., Do, A.T. & Nguyen, K.T. 2009, 'Arsenic removal by iron oxide coated sponge: treatment and waste management', Water Science and Technology, vol. 60, no. 6, pp. 1489-1495.
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One of the problems in drinking water that raises concern over the world is that millions of people still have to use arsenic-contaminated water. There is a worldwide need to develop appropriate technologies to remove arsenic from water for household and community water supply systems. In this study, a new material namely iron oxide coated sponge (IOCSp) was developed and used to remove arsenic (As) from contaminated groundwater in Vietnam. The results indicated that IOCSp has a high capacity in removing both As (V) and As (III). The adsorption capacity of IOCSp was up to 4.6mg As/g IOCSp, showing better than many other materials. It was observed from a pilot study that a small quantity of IOCSp (180 g) could reduce As concentration of 480mg/L in 1.5m3 of contaminated natural water to below 40 mg/L. In addition, an exhausted IOCSp, containing a large amount of arsenic (up to 0.42 wt %) could safely be disposed through the solidification/stabilization with cement. Addition of fly ash also reduced the amount of arsenic in the leachate.
Smith, P.J. & Vigneswaran, S. 2009, 'Effect of backwash and powder activated carbon (PAC) addition on performance of side stream membrane filtration system (SSMFS) on treatment of biological treatment effluent', Desalination and Water Treatment, vol. 11, no. 1-3, pp. 46-51.
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In this study, a pilot scale Side Stream Membrane Filtration System (SSMFS) was used to demonstrate the need for optimization of backwash conditions and the addition of PAC. Through an investigation of the amount of fouling each cycle that can be restored through backwashing over a short-term, a good operating point for long-term operation was developed. Periodic removal of 1.5% of the PAC slurry mixture (7.5 L out of 500 L) and PAC replacement (15 g/d) was found to have a positive impact on the reduction of membrane fouling
Listowski, A., Ngo, H., Guo, W., Vigneswaran, S. & Palmer, C.G. 2009, 'Concepts towards a novel integrated assessment methodology of urban water reuse', Desalination and Water Treatment, vol. 11, no. 1-3, pp. 81-92.
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Traditional supplies of large volumes of water and wastewater disposal technologies have offered a linear solution, thus intensifying environmental stress. In addition, provision of urban infrastructure especially any major augmentations are often the impractical or economically prohibitive. Urban water cycle should be viewed as an interactive and coordinated approach involving: Available water resources, Appropriate treatment technology producing fi t for purpose water quality, and Ascertaining long term balance between environmental, social and economic issues.
Shon, H., Puntsho, S., Chon, K., Aryal, R., Vigneswaran, S., Kim, I.S. & Cho, J. 2009, 'A study on the influence of ionic strength on the elution behaviour of membrane organic foulant using advanced separation tools', Desalination and Water Treatment, vol. 11, no. 1-3, pp. 38-45.
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Although membrane technology has become a reliable and viable alternative for water and wastewater treatment, membrane fouling is a serious challenge. In this case study, we report application of different techniques to extract foulant from the hollow fi bre membrane and characterize the foulant into various components of organic, inorganic and different fractions. The organic foulant was subjected to high-pressure size exclusion chromatography (HPSEC) and fl ow fi eld-fl ow fractionation (FlFFF) analysis to study the infl uence of ionic strength on its elution behaviour using NaCl and CaCl2 as carrier solutions. It was observed that an increase in ionic strength delayed the elution time of both the organic foulant and the Na-salt of Polysterene sulphone (PSS) with HPSEC. However, no such effect was observed with FlFFF analysis. Such study is signifi cant because the characteristics of the membrane organic foulant are believed to be infl uenced by the carrier ionic conditions and pH and, therefore their subsequent interaction with the membrane and membrane fouling process. However with FlFFF, whether the infl uence of carrier ionic strength is limited to certain type of ionic carriers or certain groups of natural organic matter is a scope for further research.
Hoang, T., Vigneswaran, S., Ngo, H., Kandasamy, J.K., Shim, W.G., Chaudhary, D.S., Gotety, B.P. & Peiris, P. 2008, 'Performance evaluation and mathematical modelling of granular activated carbon biofiltration in wastewater treatment', Korean Journal of Chemical Engineering, vol. 25, no. 2, pp. 259-267.
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Biological filtration is an effective technique for removing organic matter from wastewater. The performance of a biofilter can be influenced by a range of operational conditions. In this study the performance of biofilters was investigated for the influence of filter media depth, influent concentrations, filtrations rates and backwashing. The results show that performance of GAC filters decreased with shallower filter bed depths. In addition, the GAC performed better at lower influent concentration and lower filtration rates. The daily backwash adopted to avoid the physical clogging of the biofilter did not have any significant effect on the organic removal efficiency of the filter. The concentration, activity and characteristics of the biomass are quantified and described. A mathematical model was developed to simulate the organic removal of the GAC biofiltration system. The performance of the GAC filter under different influent organic concentration levels, filtration rates and filter bed depths was adequately simulated by the mathematical model developed for this study.
Areerachakul, N., Vigneswaran, S., Ngo, H. & Kandasamy, J.K. 2008, 'A continuous photocatalysis system in the degradation of herbicide', Korean Journal of Chemical Engineering, vol. 25, no. 4, pp. 663-669.
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The performance of both batch and continuous photo-catalytic reactors was studied to evaluate their capabilities in removing the sulfonyl urea herbicide of metsulfuron methyl (MM). It was found in a batch reactor that the addition of a small amount of powder activated carbon (PAC) significantly increased the rate of degradation of MM. The continuous photo-catalytic system resulted in 57% of MM removal. When a small dose of activated carbon was added in the photo-catalytic system, MM removal increased to 7886% MM removal for retention times between of 5.2521 min (corresponding to withdrawal rates of 1040 mLmin-1). In this study, the pseudo first order rate constants of a continuous photo-catalytic system revealed that shorter retention times were associated with lower rate constants. Solid phase micro extraction/gas chromatography (SPME/GC) results showed that high concentrations of MM were broken down to small volatile organic compounds (VOCs) by photo-catalytic oxidation. PAC adsorbed the photo-products and increased the degradation of MM.
Guo, W., Vigneswaran, S., Ngo, H., Kandasamy, J.K. & Yoon, S. 2008, 'The Role of a Membrane Performance Enhancer in a Membrane Bioreactor: a Comparison with Other Submerged Membrane Hybrid Systems', Desalination, vol. 231, no. 1-3, pp. 305-313.
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Among the membrane processes, membrane bioreactor (MBR) technologies are becoming an innovative and promising option for wastewater treatment and reuse. In this study the performance of the submerged membrane bioreactor was studied with an addition of MPE50, and it was compared against a sponge submerged membrane bioreactor (SMBR) and submerged membrane adsorption bioreactor (SMABR) in terms of TOC removal, COD removal, ammonium nitrogen (NH4-H) removal, orthophosphate (PO4-P) removal, transmembrane pressure (TMP) and oxygen uptake rate. SMBR with MPE50 addition significantly improved the sustainable flux and reduced membrane fouling. The improvement was better than even in the sponge SMBR system. SMBR with MPE50 achieved a high DOC and COD removal efficiency and NH4-N removal. PO4-P removal concentration of 62% initially which increased with time to over 99% after 7 day operation. In terms of phosphorus removal the sponge SMBR system performed better. OUR measurements showed that there was more microbial activity in the SMBR with MPE50 system
Chang, J., Vigneswaran, S., Kandasamy, J.K. & Tsai, L.J. 2008, 'Effect of Pore Size and Particle Size Distribution on Granular Bed Filtration and Microfiltration', Separation Science and Technology, vol. 43, no. 7, pp. 1771-1784.
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The paper reviews the effect of particle size distribution and pore size distribution on granular bed filter and crossflow microfiltration performance. The experimental results of the granular bed filter with pollen particles in suspension showed that the presence of large particles improved the filter efficiency of smaller particles in suspension. Microfiltration results with bi and tri-modal latex suspensions showed that the permeate flux and the quality were significantly affected by the particle size and its distribution, especially when the particle size was smaller than the pore size of the membrane. The mathematical model simulation results of granular bed filtration show that media pore size distribution is an important parameter of filtration for the particle removal and pressure drop across the filter
Chang, Y., Chang, J., Vigneswaran, S. & Kandasamy, J.K. 2008, 'Pharmaceutical Wastewater Treatment by Membrane Bioreactor Process - A Case Study in Southern Taiwan', Desalination, vol. 234, no. 1-3, pp. 393-401.
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A pilot-scale study of pharmaceutical wastewater treatment by a membrane bioreactor (MBR) process in southern Taiwan is presented in this paper. A 10 m3/day capacity MBR plant consisting of an aeration tank and a membrane bioreactor was installed to remove organic matter (measured in terms of chemical oxygen demand (COD)). The performance of the MBR was monitored for a period of 140 days. The removal of COD was on average over 95%. The effluent did not contain any suspended solids. During the 140 days of operation, manual cleaning was carried out twice and chemical cleaning was carried out once. A natural logarithmic evolution of the viscosity with TSS concentration was observed. The results of SEM and EDX demonstrated that the fouling on the membrane outer surface was mainly due to microorganisms and/or the sludge physiological properties. The results indicated that the MBR system has potential as a means of treating high-strength and fluctuating strength wastewater with consistent performance.
Guo, W., Vigneswaran, S., Ngo, H. & Xing, W. 2008, 'Comparison of membrane bioreactor systems in wastewater treatment', Desalination, vol. 231, no. 1-3, pp. 61-70.
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This study investigated the performance of four different membrane bioreactor (MBR) systems, namely floating media biofiltercrossflow microfiltration (FMBCFMF) system, submerged membrane bioreactor (SMBR) alone, submerged membrane adsorption bioreactor (SMABR) and spongeSMBR system, in terms of critical flux. The results indicated that FMB could be used as a pretreatment unit prior to MBR in order to minimize membrane fouling when the FMBCFMF system operates under sub-critical flux condition. The addition of powdered activated carbon (PAC) could maintain the sustainable flux at a lower TMP value (7.5 kPa). However, irreversible fouling occurred when the filtration flux exceeded the critical flux. The addition of 10% volume (reactor volume) fraction of sponge could increase sustainable flux of SMBR system to 2 times.
Erdei, L., Vigneswaran, S. & Areerachakul, N. 2008, 'A combined photocatalytic slurry reactor-immersed membrane module system for advanced wastewater treatment', Separation and Purification Technology, vol. 62, no. 2, pp. 382-388.
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type continuous photocatalytic (CP) system and an immersed hollow fibre membrane micro-ultrafilter (MF/UF) unit. The CP reactor charged with 1 g/L P-25 catalyst removed 63% dissolved organic carbon (DOC) from a synthetic wastewater (representing biologically treated sewage effluent). The addition of 0.05 g/L of powdered activated carbon (PAC) increased DOC removal up to 76%. The start-up times to achieve 60% DOC removal were 31 min and 15 min, respectively. These results show a 16 times improvement in volumetric load over a comparable batch reactor system used in previous studies by our group. Slurry type photocatalytic reactors need subsequent particle separation to retain the catalyst in the system and allow the discharge of treated effluent. The immersed membrane module accomplished this without prior slurry settling step. Membrane feed pre-treatment with pH adjustment and particle charge neutralisation with aluminium chloride coagulant led to improved critical membrane fluxes, 15.25 L/m2 h and 19.05 L/m2 h, respectively. In each experiment MF/UF produced near zero turbidity permeate, completely retained the photocatalyst, and flocculation also improved the efficiency of DOC removal. Membrane fouling was controlled by particle aggregation rather than feed DOC levels, but the latter had significant impact on coagulant demand. The complete treatment train achieved up to 92% DOC reduction with 12 mg/L AlCl3 dosage using in-line coagulation conditions. The results show that in-line coagulation offers a simple yet effective means to improve the performance of slurry type photocatalytic-MF/UF hybrid systems for advanced water and wastewater treatment applications. &copy; 2008 Elsevier B.V. All rights reserved.
Thiruvenkatachari, R., Vigneswaran, S. & Moon, I.S. 2008, 'A review on UV/TiO2 photocatalytic oxidation process', Korean Journal of Chemical Engineering, vol. 25, no. 1, pp. 64-72.
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Advanced oxidation processes (AOPs) with UV irradiation and photocatalyst titanium dioxide (TiO2) are gaining growing acceptance as an effective wastewater treatment method. A comprehensive review of the UV-TiO2 photocatalytic oxidation process was conducted with an insight into the mechanism involved, catalyst TiO2, irradiation sources, types of reactors, comparison between effective modes of TiO2 application as immobilized on surface or as suspension, and photocatalytic hybrid membrane system. Photocatalytic degradation technique with titanium dioxide is generally applied for treating wastewater containing organic contaminants due to its ability to achieve complete mineralization of the organic contaminants under mild conditions such as ambient temperature and ambient pressure. Recently, photocatalysis studies using TiO2 have been gaining attention for the degradation of persistent organic pollutants and other organic chemicals which are known to be endocrine disruptors. Treatment of wastewater in a titanium dioxide-suspended slurry reactor has been widely utilized due to its simplicity and enhanced degradation efficiency. However, this system requires separation of TiO2 from water after the photocatalytic process. The final section of the manuscript focuses on the removal of TiO2 using a membrane hybrid system. A two-stage coagulation and sedimentation process coupled with microfiltration hollow-fibre membrane process was found to achieve complete removal of TiO2, and the recovered TiO2 can be reused for a photocatalytic process after regeneration.
Thiruvenkatachari, R., Vigneswaran, S. & Naidu, R. 2008, 'Permeable reactive barrier for groundwater remediation', Journal of Industrial and Engineering Chemistry, vol. 14, no. 2, pp. 145-156.
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This article aims to provide an overview of the upcoming technology of permeable reactive barriers for groundwater remediation. A comprehensive list of references and web-links are also provided for further in-depth understanding. A brief discussion on the Australian perspective on this emerging technology is also included.
Guo, W., Vigneswaran, S., Ngo, H., Xing, W. & Goteti, P. 2008, 'Comparison of the performance of submerged membrane bioreactor (SMBR) and submerged membrane adsorption bioreactor (SMABR)', Bioresource Technology, vol. 99, no. 5, pp. 1012-1017.
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This study focuses on comparing the performance of submerged membrane bioreactor (SMBR) and submerged membrane adsorption bioreactor (SMABR) over a period of 20 days at a hydraulic retention time (HRT) of 3.1 h. The effects of PAC on critical flux and membrane fouling were also investigated. The SMABR exhibited better results in terms of mixed liquor suspended solids (MLSS) growth, DOC removal (over 96%), COD removal (over 95%), transmembrane pressure (TMP) and oxygen uptake rate. Nearly 100% of bacteria and 100% of total coliforms were removed in both systems. The addition of PAC could maintain the critical flux at a lower TMP value (7.5 kPa), while irreversible fouling caused by PAC occurred when the filtration flux exceeded critical flux.
Areerachakul, N., Vigneswaran, S., Kandasamy, J.K. & Duangduen, C. 2008, 'The degradation of humic substance using continuous photocatalysis systems', Separation Science And Technology, vol. 43, no. 1, pp. 93-112.
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Photocatalytic oxidation is an emerging technology in water and wastewater treatment. Photocatalysis often leads to complete degradation of organic pollutants without the need for chemicals. This study investigated the degradation of humic substances in
Guo, W., Ngo, H., Vigneswaran, S., Xing, W. & Goteti, P. 2008, 'A Novel Sponge-Submerged Membrane Bioreactor (SSMBR) for Wastewater Treatment and Reuse', Separation Science and Technology, vol. 43, no. 2, pp. 273-285.
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Membrane fouling has been regarded as one of the biggest challenges to widespread application of membrane bioreactor (MBR). This study focuses on minimizing the membrane fouling and improving the performance of submerged membrane bioreactor (SMBR) by porous sponge addition. The effects of sponge addition on sustainable flux and membrane fouling were investigated. Acclimatized sponge could significantly increase the suspended growth in SMBR with biomass of 16.7 g/L(sponge). With the sponge volume fraction of 10%, SSMBR could enhance sustainable flux up to 50 L/m2 h compared with sustainable flux of SMBR (only 25 L/m2 h). SSMBR also exhibited excellent results in terms of DOC removal (over 95%), COD removal (over 97%), lower transmembrane pressure development, and oxygen uptake rate. Over 89% of NH4-N and 98% of PO4-P were removed when SSMBR was operated with a MLSS concentration of 15 g/L.
Chiemchaisri, C., Passananon, S., Ngo, H. & Vigneswaran, S. 2008, 'Enhanced natural organic matter removal in floating media filter coupled with microfiltration membrane for river water treatment', Desalination, vol. 234, no. 1-3, pp. 335-343.
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This research work was carried out to determine natural organic matter (NOM) removal in floating media filter coupled with microfiltration membrane applied to the treatment of river water in Bangkok, Thailand. Polyaluminum chloride was found to be the most effective coagulant providing enhanced coagulation effect for NOM removal. Optimum filtration rate of floating media filter was 11 m3/m2 h at which highest NOM removal efficiencies of 82.2% was achieved. Subsequent treatment in microfiltration membrane unit operated at a filtration rate of 0.45 m3/m2 d provided total NOM removal of 85.786.6%. Periodical cleanings of floating media filter and microfiltration membrane were accomplished by using air scouring coupled with water flushing at every 8 and 24 h interval. As a result of NOM removal, the sum of trihalomethane (THM) ratio was reduced from 0.51.1 in raw water to 0.20.6 in treated water. Membrane fouling study revealed that both turbidity and NOM affected transmembrane pressure (TMP) built up but particulate fouling provided greater impact on TMP as compared to organic adsorption on the membrane surface.
Erdei, L., Chang, C. & Vigneswaran, S. 2008, 'In-line Flocculation-Submersed MF/UF Membrane Hybrid System in Tertiary Wastewater Treatment', Separation Science and Technology, vol. 43, no. 7, pp. 1839-1851.
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Coagulation/flocculation pre-treatment of feeds can successfully mitigate the drawbacks of membrane micro- and ultra filtration processes: fouling and limited ability to remove organic pollutants. Laboratory experiments conducted with a synthetic wastewater (representing biologically treated secondary effluent) using 0.1 &micro;m pore size hollow fiber membrane showed that simple in-line flocculation pre-treatment with inorganic coagulants dramatically reduced membrane fouling rates. The hybrid system also ensured over 70% organic matter removal in terms of dissolved organic carbon (DOC). In the experiments in in-line flocculation outperformed clarification pre-treatment at optimum coagulant dosages. Differences in floc characteristics and elevated suspended solids concentrations in the membrane tank may explain this finding, but the exact causes were not investigated in this study. The beneficial effects of in-line flocculation pre-treatment to MF/UF separation were also confirmed in the treatment of septic tank effluent in a membrane bioreactor (MBR). The fouling rate of the 0.4 &micro;m pore size (flat-sheet) membrane was substantially reduced with 10-100 mg L-1 ferric chloride coagulant doses, and total dissolved chemical oxygen demand (DCOD) removal also increased from 66% up to 93%. These findings are consistent with the results of other experimental studies and show that pre-treatment controls submersed MF/UF filtration performance.
Shon, H., Vigneswaran, S. & Cho, J. 2008, 'Comparison of Physico-Chemical Pretreatment Methods to Seawater Reverse Osmosis: Detailed Analyses of Molecular Weight Distribution of Organic Matter in Initial Stage.', Journal Of Membrane Science, vol. 320, pp. 151-158.
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In desalination, effective pretreatment is the key to reduce membrane fouling that occurs during the seawater reverse osmosis (SWRO) process. However, it is difficult to compare the flux decline after different pretreatments using a small-scale reverse osmosis filtration unit. In this study, we successfully evaluated the effect of pretreatment on SWRO in terms of molecular weight distribution (MWD) of seawater organic matter (SWOM) after 20 h of SWRO operation. Microfiltration (MF), ultrafiltration (UF), ferric chloride (FeCl3) flocculation and powdered activated carbon (PAC) adsorption, were used as pretreatment. The effluents and the retentates after each pretreatment and 20 h of SWRO operation were characterized in terms of MWD. Although the normalized flux of SWRO showed similar flux decline (J/J0 = 0.17) with/without pretreatment, SWOM concentration in the retentates after different pretreatments was different in quantity and it increased linearly with time. The slope of the SWOM increase was 0.110, 0.096, 0.077 and 0.059 after MF, FeCl3 flocculation, UF and PAC adsorption pretreatments, respectively. MW peaks for the seawater used in this study consisted of 1200 Da (biopolymers), 950 Da (fulvic acids), 650 Da (hydrolysates of humic substances), 250 Da (low MW acids) and 90 Da (low MW neutrals and amphiphilics). FeCl3 flocculation preferentially removed 1200 Da (biopolymers), while PAC adsorption mostly removed 950 Da (fulvic acids). UF and NF removed only a marginal amount of relatively large organics, while RO removed the majority of organics. The intensity of 1200, 950, 650 and 250 Da MW in the RO retentates increased with the RO operation time. The organics of MW around 1200 Da (biopolymers) had a relatively low rate of increase with time compared with those of lower MW. This suggests that the SWOM of 1200 Da MW was preferentially retained on the membrane surface.
Nguyen, V., Vigneswaran, S., Ngo, H., Kandasamy, J.K. & Choi, H. 2008, 'Arsenic removal by photo-catalysis hybrid system', Separation and Purification Technology, vol. 61, no. 1, pp. 44-50.
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Arsenic is a toxic semi-metallic element that can be fatal to human health. Arsenic pollution in water is found in many parts of the world, especially in developing countries such as Bangladesh, India, Nepal, and Vietnam. Photo-oxidation experiments with titanium dioxide (TiO2) as photo-catalyst showed that photo-oxidation of As(III) to As(V) is possible within minutes. Further, TiO2 can also adsorb both As(III) and As(V) on its surface. Photo-catalysis reaction with TiO2 reduced about 98% of arsenite from water containing 500 ?g/L of arsenite. By adding nano-scale zero valent iron (nZVI) of 0.05 g/L in the photo-reactor, arsenic removal can be significantly enhanced. Further the TiO2 requirement is five times less in this photo-catalysis nZVI hybrid system. The photo-catalytic degradation processes was modeled using the first-order, second-order and LangmuirHinshelwood kinetics equations and removal rates were simulated.
Zhang, R., Vigneswaran, S., Ngo, H. & Nguyen, H.V. 2008, 'Fluidized bed magnetic ion exchange (MIEX) as pre-treatment process for a submerged membrane reactor in wastewater treatment and reuse', Desalination, vol. 227, no. 1-3, pp. 85-93.
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Magnetic ion exchange (MIEX) resin can effectively remove significant amounts of organic matter from biologically treated sewage effluent. The MIEX process has mainly been used as a batch process, which requires a large area for accommodating both contact tank and settling tank in the treatment process. In this study, a fluidized bed MIEX reactor (a semi-continuous process) was used as a pre-treatment for a submerged membrane. When used as a pre-treatment for a submerged membrane, the fluidized bed MIEX contactor could remove a significant amount of organic matter in the wastewater (80% removal). This pre-treatment helped to reduce membrane fouling and keep transmembrane pressure low during the membrane operation of 8 h (less than 19 kPa). The regeneration of MIEX resin (number of regeneration, regeneration time, etc.) did not have any adverse effect on the organic removal by MIEX
Shon, H., Phuntsho, S. & Vigneswaran, S. 2008, 'Effect of Photocatalysis on the Membrane Hybrid System for wastewater treatment', Desalination, vol. 225, no. 1-3, pp. 1-16.
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An integrated photocatalysismembrane hybrid system was investigated for wastewater treatment with the main focus on improving the cross flow microfiltration (MF) permeate flux. Photocatalysis with TiO2 (P25 Degussa) suspension as photocatalyst was applied both as pre-treatment and as inline treatment with MF. The TiO2 slurry was found to have significant effect in permeate flux for wastewater with lower dissolved organic carbon concentration. The MF flux decline due to TiO2 slurry cake on the membrane surface was minimized by allowing the TiO2 slurry to settle and by using only the supernatant for further treatment using the hybrid system. The investigation also included the study on the effect of photocatalytic reaction time and the slurry settling times on the MF permeate flux. The irradiation of ultraviolet on the MF surface in presence of TiO2 catalyst in suspension yielded in an increase in permeate flux.
Kim, S., Ngo, H., Shon, H. & Vigneswaran, S. 2008, 'Adsorption and Photocatalysis Kinetics of Herbicide onto Titanium Oxide and Powdered Activated Carbon', Separation and Purification Technology, vol. 58, no. 3, pp. 335-342.
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The adsorption and photocatalysis kinetics of metsulfuron-methyl (MM) onto titanium oxide (TiO2) and powdered activated carbon (PAC) were studied at varying adsorbent amount and MM concentration. The overall mass transfer in adsorption was estimated from concentration decay curves obtained in the batch adsorber. The maximum adsorption capacity decreased with increasing adsorbent amount in TiO2 adsorption. The adsorption isotherms of MM could be plotted using the Langmuir isotherm model with a reasonable degree of accuracy having higher r2 values rather than Freundlich isotherm model. Linear driving force approximation (LDFA) kinetic equation with Langmuir adsorption isotherm model was successfully applied to predict the adsorption kinetics data in various concentrations of MM in photobatch reactor. The estimated mass transfer coefficient was used to be 3.0 10-5, 5.5 10-5, 9.1 10-5 m/s in PAC adsorption and 2.0 10-5, 1.1 10-5, 9.0 10-6 m/s in TiO2 adsorption for a different MM concentration of 20, 50 and 70 mg/L, respectively. Photocatalysis kinetics was same with TiO2 of 0.2 g/L regardless of TiO2 amounts and the MM degradation kinetics was enhanced by TiO2 catalysis rather than only UV light degradation. Among the photocatalysis kinetics model with first-order, second-order and LangmuirHinshelwood (LH) model, a second-order kinetic model was found to well present the experimental data of MM by TiO2 catalyst for the range of various TiO2 amounts and MM concentration studied.
Shon, H., Vigneswaran, S., Kandasamy, J.K. & Shim, W.G. 2008, 'Ultraflitration Of Wastewater With Pretreatment: Evaluation of Flux Decline Models', Desalination, vol. 231, no. 1-3, pp. 332-339.
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Three different mathematical models relating the flux decline were investigated to quantify the effects of pretreatment in a membrane filtration system. The models used are empirical flux decline model, series resistance flux decline model and modified series resistance flux decline model. A cross flow ultrafiltration unit was used to study flux decline and organic removal from synthetic wastewater. Flocculation and adsorption pretreatments were carried out with ferric chloride (FeCl3) and activated carbon of different doses. The three models could predict flux decline after different pretreatments and could be used as a pretreatment index to ultrafiltration.
Shon, H.K., Phuntsho, S. & Vigneswaran, S. 2008, 'Effect of photocatalysis on the membrane hybrid system for wastewater treatment', DESALINATION, vol. 225, no. 1-3, pp. 235-248.
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Guo, W., Vigneswaran, S., Ngo, H. & Xing, W. 2007, 'Experimental investigation on acclimatized wastewater for membrane bioreactors', Desalination, vol. 207, no. 1-3, pp. 383-391.
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The inoculation and acclimatization of activated sludge (AS) is one of the vital components to provide preferably suspended aerobic growth and desired treatment mechanism for a treated wastewater using MBR. The performance of a floating media biofilter-s
Shon, H., Vigneswaran, S., Kim, I.S., Cho, J., Kim, G., Kim, J.K. & Kim, J. 2007, 'Preparation of titanium dioxide (TiO2) from sludge produced by titanium tetrachloride (TiCl4) flocculation of wastewater', Environmental Science & Technology, vol. 41, no. 4, pp. 1372-1377.
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Sludge disposal is one of the most costly and environmentally problematic challenges of modern wastewater treatment worldwide. In this study, a new process was developed, which has a significant potential for lower cost of waste disposal, protection of t
Zhang, R., Vigneswaran, S., Ngo, H. & Nguyen, H.V. 2007, 'A Submerged Membrane Hybrid System Coupled With Magnetic Ion Exchange (miex (r)) And Flocculation In Wastewater Treatment', Desalination, vol. 216, no. 1-3, pp. 325-333.
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Wastewater treated by conventional secondary and tertiary processes cannot be reused directly without further treatment. The membrane process can achieve a high quality effluent, but membrane fouling caused by organic matter affects membrane performance
Shon, H., Vigneswaran, S., Kim, J.K. & Ngo, H. 2007, 'Application Of Hybrid Photocatalysis Systems Coupled With Flocculation And Adsorption To Biologically Treated Sewage Effluent For Organic Removal', Korean Journal Of Chemical Engineering, vol. 24, no. 4, pp. 618-623.
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The application of a photocatalysis hybrid system coupled with flocculation and adsorption in treating biologically treated sewage effluent (BTSE) was investigated. The removal of organic matter was studied in terms of dissolved organic matter (DOC), rem
Shon, H., Vigneswaran, S., Ngo, H., Kim, J.K. & Kandasamy, J.K. 2007, 'Effect Of Flocculation As A Pretreatment To Photocatalysis In The Removal Of Organic Matter From Wastewater', Separation And Purification Technology, vol. 56, no. 3, pp. 388-391.
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Effects of different flocculants (chloride-based salts and ferric and ferrous salts) and initial organic concentration of wastewater on flocculation-photocatalysis hybrid process were investigated. Titanium dioxide (TiO2) adsorption alone, flocculation a
Dunphy, A.J., Beecham, S.C., Vigneswaran, S., Ngo, H., McLaughlan, R.G. & Collins, A.P. 2007, 'Development of a Confined Water Sensitive Urban Design (WSUD) System Using Engineered Soils', Water Science and Technology, vol. 55, no. 4, pp. 211-214.
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Innovative Water Sensitive Urban Design (WSUD) systems are being investigated at three locations to the north and south of Sydney, Australia. These systems contain porous concrete pipes that are designed so that stormwater exfiltrates through the permeable walls of the pipes into the surrounding substrate media material. The porous pipes and media material treat the passing stormwater. The primary aim of the overall project is to develop a model to describe the treatment effectiveness of confined WSUD systems. This paper focuses on the system located at the Weathertex Industrial Site, Heatherbrae. Due to wood processing operations that occur at this site, it is recognised that the surface runoff will carry a heavy organics loading. Granulated Activated Carbon (GAC) is recognised for its ability to reduce the concentration of dissolved organics present in both wastewater and stormwater. GAC was therefore chosen as a filtration medium to be investigated at this site. To maximise the effectiveness of the GAC, extensive laboratory batch studies were undertaken prior to the field system being constructed to determine the optimum GAC/sand ratio. The purpose of the experimental work was to assess the dissolved organic removal potential through sorption of various concentrations of GAC. The aim of this paper is to describe these laboratory experiments and discuss how they related to the field system. Through these experiments it was determined that a sand/GAC ratio of 25:1 was ideal for the media material at the Heatherbrae site.
Vigneswaran, S., Shon, H., Kandasamy, J.K. & Shim, W.G. 2007, 'Performance of Granular Activated Carbon (GAC) adsorption and biofiltration in the treatment of biologically treated sewage effluent', Separation Science and Technology, vol. 42, no. 14, pp. 3101-3116.
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In this study, the performance of GAC adsorption and biofiltration systems in treating biological treated sewage effluent (BTSE) was evaluated in terms of organic removal efficiency, organic fractions, and molecular weight distribution (MW) of organic matter (OM) removed. The GAC biofilter removed 23.5% and 61% of the hydrophobic fractions and hydrophilic fractions of OM in the BTSE respectively. MW distribution studies of GAC filter and GAC adsorption revealed the following: Hydrophobic fraction of the effluent showed a peak at 345 dalton after GAC biofiltration and 256 dalton after GAC adsorption, whereas, with hydrophilic fractions, peaks at 46,178 and 345 daltons were observed after GAC biofiltration and peaks at 46,178 and 256 daltons after GAC adsorption. Transphilic fraction showed the peaks at 12,783 dalton with GAC biofiltration, and 1,463 dalton with GAC adsorption. The performance of the GAC biofilter was successfully mathematically modelled.
Vigneswaran, S., Guo, W., Smith, P.J. & Ngo, H. 2007, 'Submerged Membrane Adsorption Hybrid System (smahs) Process Control And Optimization Of Operating Parameters', Desalination, vol. 202, no. 1-3, pp. 392-399.
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This study is to investigate the effect of operating parameters of submerged membrane adsorption hybrid system (SMAHS) such as preadsorption and powdered activated carbon requirement, aeration, filtration flux; There is an optimum value for each of the o
Shon, H., Smith, P.J., Vigneswaran, S. & Ngo, H. 2007, 'Effect Of A Hydrodynamic Cleaning Of A Cross-flow Membrane System With A Novel Automated Approach', Desalination, vol. 202, no. 1-3, pp. 351-360.
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The effect of different hydraulic cleaning methods was investigated in terms of flux decline and resistance using the cross-flow UF unit. The use of varied production intervals, varied ratios of periodic relaxation and the use of a periodic high-rate cro
Areerachakul, N., Vigneswaran, S., Ngo, H. & Kandasamy, J.K. 2007, 'Granular activated carbon (GAC) adsorption-photocatalysis hybrid system in the removal of herbicide from water', Separation And Purification Technology, vol. 55, no. 2, pp. 206-211.
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The performance of the granular activated carbon (GAC) fixed bed adsorption, the continuous photocatalysis systems and a combination of the two were studied to evaluate their capabilities in removing the herbicide of metsulfuron-methyl (MM) from waste wa
Shon, H., Vigneswaran, S., Kim, J.H. & Ngo, H. 2007, 'Application of a Photocatalysis System to Wastewater: A Detailed Organic Removal of different fractions', Studies in Surface Science and Catalysis, vol. 172, pp. 559-560.
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A removal of detailed organic matter by photocatalysis was investigated in terms of molecular weight (MW) distribution and fraction (hydrophobic (HP), transphilic (TP) and hydrophilic (HL)). The photooxidation with TiO, removed the majority of MW (263 daltons, 580, 865, and 43109). Effluent organic matter (EfOM) removal in wastewater was high (80%) for HP and TP components. EfOM removal from the HL fraction was however minimum, suggesting that the HL fraction may be the fraction of low activity in photocatalytic degradation. Thus, the HL fraction has to be removed from BTSE in the application of photocatalysis for the purpose of wastewater reuse
Vigneswaran, S. 2007, 'Organic matter in water and wastewater: Constituents and analysis', Research Journal of Chemistry and Environment, vol. 11, no. 2, pp. 3-5.
Shon, H., Vigneswaran, S. & Ngo, H. 2006, 'Effect of partial flocculation and adsorption as pretreatment to ultrafiltration', Aiche Journal, vol. 52, no. 1, pp. 207-216.
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In this study, the sufficiency of flocculation and adsorption with reduced doses of ferric chloride and powdered activated carbon (PAC) as pretreatment to ultrafiltration. (UF) was investigated. A 50 mg/L dose of FeCl3 and 0.5 g/L of PAC removed a majori
Nguyen, V., Vigneswaran, S., Ngo, H., Pokhrel, D. & Viraraghavan, T. 2006, 'Specific treatment technologies for removing arsenic from water', Engineering In Life Sciences, vol. 6, no. 1, pp. 86-90.
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Arsenic (As) is a highly toxic metalloid found in ground and surface water. Arsenic contamination in drinking water leads to harmful effects on human health. To eliminate arsenic from drinking water, several technologies such as coagulation, adsorption,
Guo, W., Vigneswaran, S., Ngo, H., Nguyen, V.T. & Ben Aim, R.M. 2006, 'Influence of bioreaction on a long-term operation of a submerged membrane adsorption hybrid system', Desalination, vol. 191, no. 1-3, pp. 92-99.
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This study investigates the long-term performance of a submerged membrane adsorption hybrid system (SMAHS) for organic matter removal from synthetic wastewater representing biologically treated wastewater by using a low dose of powdered activated carbon
Chang, Y., Chang, J., Lin, Y., Erdei, L. & Vigneswaran, S. 2006, 'Quantification of air stripping and biodegradation of organic removal in acrylonitrile-butadiene-styrene (ABS) industry wastewater during submerged membrane bioreactor operation', Desalination, vol. 191, no. 1-3, pp. 162-168.
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With the rapid development of the petrochemical industry in Taiwan, a significant amount of nitrogenous organic wastewater is generated. Some of this wastewater contains volatile residual monomers, such as acrylonitfile-butadiene-styrene (ABS) manufactur
Zhang, R., Vigneswaran, S., Ngo, H. & Nguyen, H.V. 2006, 'Magnetic ion exchange (MIEX (R)) resin as a pre-treatment to a submerged membrane system in the treatment of biologically treated wastewater', Desalination, vol. 192, no. 1-3, pp. 296-302.
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Magnetic ion exchange (MIEX (R)) resin can remove a majority of hydrophilic compounds and a significant amount of hydrophobic compounds from biologically treated secondary effluent within a short contact time of 20 min. It removed a majority of small mol
Shon, H., Vigneswaran, S. & Snyder, S. 2006, 'Effluent organic matter (EfOM) in wastewater Constituents, effects, and treatment', Critical Reviews In Environmental Science And Technology, vol. 36, no. 4, pp. 327-374.
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Wastewater reuse is being increasingly emphasized as a strategy for conservation of limited resources of freshwater and as a mean of safeguarding the aquatic environment due to contaminants present in wastewater. Although secondary and tertiary treated w
Shon, H., Kim, S.H., Erdei, L. & Vigneswaran, S. 2006, 'Analytical methods of size distribution for organic matter in water and wastewater', Korean Journal Of Chemical Engineering, vol. 23, no. 4, pp. 581-591.
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Organic matter (OM), such as natural organic matter (NOM) in surface waters, and effluent organic matter (EfOM) in wastewaters causes many problems. For example, color, taste and odor derogate potable water quality, while the presence of endocrine disrup
Smith, P.J., Vigneswaran, S., Ngo, H., Nguyen, H.T. & Ben-Aim, R. 2006, 'Application of an automation system and a supervisory control and data acquisition (SCADA) system for the optimal operation of a membrane adsorption hybrid system', Water Science And Technology, vol. 53, no. 4-5, pp. 179-184.
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The application of automation and supervisory control and data acquisition (SCADA) systems to municipal water and wastewater treatment plants is rapidly increasing. However, the application of these systems is less frequent in the research and developmen
Shon, H., Vigneswaran, S., Kim, I., Cho, J. & Ngo, H. 2006, 'Fouling of ultrafiltration membrane by effluent organic matter A detailed characterization using different organic fractions in wastewater', Journal Of Membrane Science, vol. 278, no. 1-2, pp. 232-238.
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Membrane fouling caused by hydrophobic (HP), transphilic (TP), and hydrophilic (HL) fractions in biologically treated sewage effluent (BTSE) are still not well understood. Some researches reported that the HP fraction (humic substances) were the major pr
Yadav, N.N., Maheswaran, S.M., Shutthanandan, V., Thevuthasan, S., Hart, T.R., Ngo, H. & Vigneswaran, S. 2006, 'Comparison of analytical techniques for analysis of arsenic adsorbed on carbon', Water Quality Research Journal Of Canada, vol. 41, no. 2, pp. 185-189.
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Activated carbon (AC) has been used extensively to treat arsenic-contaminated groundwater for a number of years. To date, attempts to quantify directly the amount of arsenic removed by the activated carbon using nondestructive methods has been limited. H
Jang, N.J., Shon, H., Ren, X., Vigneswaran, S. & Kim, I.S. 2006, 'Characteristics of Bio-Foulants in the Membrane Bioreactor', Desalination, vol. 200, no. 1-3, pp. 201-202.
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Smith, P.J., Vigneswaran, S., Ngo, H., Nguyen, H.T. & Aim, R.B. 2006, 'A New Approach to backwash initiation in Membrance Systems', Journal of Membrane Science, vol. 278, no. 1-2, pp. 381-389.
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Yadav, N.N., Maheswaran, S.M., Shutthanandan, V., Thevuthasan, S., Ngo, H. & Vigneswaran, S. 2006, 'Quantification of Arsenic in activated carbon using particle induced X-ray emission', Nuclear Instruments and Methods in Physics Research B, vol. 251, no. 1, pp. 191-196.
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To date, the trace elemental analysis of solids with inhomogencous internal structure has been limited, particularly in the case of adsorbents. High-energy ion beam based particle induced X-ray emission (PIXE) is an ideal analytical too] suitable for sim
Chang, J., Chang, Y., Cheng, A., Erdei, L. & Vigneswaran, S. 2006, 'Long-term operation of submerged membrance bioreactor for the treatment of high strength acrylonitrile-butadiene-sturene (ABS) Wastewater: effect of hydraulic retention time', Desalination, vol. 191, no. 1-3, pp. 45-51.
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Shon, H., Vigneswaran, S., Ngo, H., Johnston, A.J., Kim, I.S. & Cho, J. 2006, 'Performance of Flocculation and Adsorption Pretreatments to Ultrafiltration of Biologically Treated Sewage Effluent: the Effect of Seasonal Variations', Separation Science and Technology, vol. 41, no. 16, pp. 3585-3596.
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The effect of seasonal variations on ultrafiltration (UF) following pretreatment was investigated in terms of organic removal, removal of fraction, and molecular weight (MW) distribution. The MW range of effluent organic matter (EfOM) in biologically treated sewage effluent during winter (BTSE-W) consisted of large MW. However, the MW ranged from 3000 to 200 daltons in biologically treated sewage effluent in the summer (BTSE-S). During filtration experiments of BTSE-S, the UF NTR 7410 filter showed rapid flux decline with time without pretreatment. FeCl3 flocculation removed the hydrophobic (HP) and hydrophilic (HL) fractions with different trends. In winter the HP fraction was removed up to 68.5%, whereas during the summer season, the HL fraction was removed by up to 59.8%. Flocculation removed large MW organics together with small MW, while PAC removed the majority of small MW organics. The flux decline with adsorption was also more severe than that with flocculation. Considering MW distribution, when large MW was removed by flocculation, the flux decline was minimized, whereas PAC adsorption which removed small MW still decreased the permeate flux.
Areerachakul, N., Shon, H., Vigneswaran, S. & Ngo, H. 2006, 'Photocatalytic hybrid system in degradation of herbicide (metsulfuron-methyl)', Water Science & Technology: Water Supply, vol. 6, no. 2, pp. 109-114.
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Photocatalytic oxidation is becoming an emerging technology in water and wastewater Photocatalysis often leads to complete degradation of organic pollutants without any need for chemicals. this study, the removal of the herbicide metsulfuron-methyl (MM)
Kanel, S.R., Choi, H., Kim, J.Y., Vigneswaran, S. & Shim, W.G. 2006, 'Removal of Arsenic (III) from Groundwater using Low-Cost Industrial By-products-Blast Furnace Slag', Water Quality Research Journal of Canada, vol. 41, no. 2, pp. 130-139.
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Smith, P.J., Shon, H., Vigneswaran, S., Ngo, H. & Nguyen, H.T. 2006, 'Productivity enhancement in a cross-flow ultrafiltration membrane system through automated de-clogging operations', Journal Of Membrane Science, vol. 280, no. 1-2, pp. 82-88.
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A membrane system only has a limited operational lifetime, whereby it becomes so severely fouled that continued operation must be stopped. In the cross-flow configuration of membrane filtration of wastewater, both increased cross-flow velocities and decr
Nguyen, V., Vigneswaran, S., Ngo, H., Pokhre, D. & Viraraghavan, T. 2006, 'Iron-coated sponge as effective media to remove arsenic from drinking water', Water Quality Research Journal Of Canada, vol. 41, no. 2, pp. 164-170.
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Arsenic (As) contamination in drinking water is a serious problem in a number of countries in the world, especially in small communities and developing countries. Arsenic is related to many health diseases. Several technologies such as coagulation, adsor
Khirani, S., Paul, J., Manero, M., Ben Aim, R.M. & Vigneswaran, S. 2006, 'Effect of periodic backwash in the submerged membrane adsorption hybrid system (SMAHS) for wastewater treatment', Desalination, vol. 191, no. 1-3, pp. 27-34.
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The submerged membrane adsorption hybrid system (SMAHS) is an attractive solution in treating wastewater; however it faces membrane fouling although to a less extent. In this study, different adsorbents and resins were investigated in order to find a sub
Smith, P.J., Shon, H.K., Vigneswaran, S., Ngo, H.H. & Nguyen, H. 2006, 'Productivity enhancement in a cross-flow ultrafiltration membrane system through automated de-clogging operations', Journal of Membrane Science, vol. 280, no. 1-2, pp. 82-88.
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A membrane system only has a limited operational lifetime, whereby it becomes so severely fouled that continued operation must be stopped. In the cross-flow configuration of membrane filtration of wastewater, both increased cross-flow velocities and decreased operational transmembrane pressures can be used to decrease membrane fouling and extend the life cycle of the membrane separation process. The study found that an optimised usage of two de-clogging techniques, with a 1 h production period followed by a 1 min relaxation period and then a 1 min high cross-flow rate period, resulted in a net productivity increase of 14.8%. The study involved a detailed investigation into the utilization of two automated cleaning techniques to reduce fouling problems encountered when cross-flow membrane systems are operated with high permeate flux rates. The two cleaning techniques studied were periodic membrane relaxation and a periodic high rate cross-flow. During both the relaxation and high rate cross-flow periods, permeate production was stopped. This results in an operational loss in productivity. When each cleaning technique was operated individually, there was a net productivity decrease of 0.7%, due to the 3.2% operational loss due to cleaning technique being implemented. The system was developed using a Programmable Logic Controller (PLC) and a Supervisory Control and Data Acquisition (SCADA) system to accurately control and monitor the process. &copy; 2006 Elsevier B.V. All rights reserved.
Shon, H., Vigneswaran, S., Ngo, H., Kim, I.S. & Ben Aim, R.M. 2005, 'Foulant Characterization of the NF Membranes with and without Pretreatment of Biologically Treated Wastewater', Water Science And Technology, vol. 51, no. 6-7, pp. 277-284.
In this study, different pretreatment methods such as ferric chloride (FeCl3) flocculation and powdered activated carbon (PAC) adsorption were evaluated in terms of their capability in removing effluent organic matter (EfOM) and the characteristics of the foulants on the NF membranes. A detailed experiment was conducted with two NF membranes (NTR 729HF with MWCO 700 daltons and LF 10 with MWCO 200 daltons). With pretreatment, the concentration of organic matter on the membranes decreased to 5.67110+3 (NTR 729HF) and 4.94010+3 (LF 10) mg EfOM/cm2 of membrane from 6.37210+3 (NTR 729HF) and 4.97910+3 (LF 10) mg EfOM/cm2 of membrane. The MW of the solute fraction of biologically treated sewage effluent (BTSE) ranged from 250 daltons to about 3573 (the most important being 250-520 daltons). The weight-averaged MW values of the foulants on the NTR 729HF membrane reduced from 304 daltons without pre-treatment to 208 daltons with pretreatment. In the case of EfOM, the small molecules (MW 300 to 500 daltons) are mainly responsible for the membrane fouling. Thus, the MW distribution of organic matter in the effluent and in the foulant can be used as a representative tool to evaluate the efficiency of pretreatment and NF and in the selection of their operating conditions.
Jegatheesan, V., Vigneswaran, S. & Lee, S. 2005, 'Deposition of submicron particles in deep bed filtration under unfavorable surface conditions', Korean Journal Of Chemical Engineering, vol. 22, no. 1, pp. 142-146.
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Deterioration in the filter removal efficiency of submicron particles (lambda/lambda(0)) under unfavorable surface conditions is affected by the number of deposited particles per filter grain. In the case of above micron particles, the deterioration of f
Chiemchaisri, C., Chiemchaisri, W., Kornboonraksa, T., Dumrongsukit, C., Threedeach, S., Ngo, H. & Vigneswaran, S. 2005, 'Particle and microorganism removal in floating plastic media coupled with microfiltration membrane for surface water treatment', Water Science And Technology, vol. 51, no. 10, pp. 93-100.
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Floating plastic media followed by hollow fiber microfiltration membrane was applied for surface water treatment. The performance of the system in terms of particle and microorganisms was investigated. The floating filter was examined at different filtra
Shon, H., Vigneswaran, S., Ngo, H., Kim, I. & Ben Aim, R.M. 2005, 'Foulant characterization of the NF membranes with and without pretreatment of biologically treated wastewater', Water Science And Technology, vol. 51, no. 6-7, pp. 277-284.
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In this study, different pretreatment methods such as ferric chloride (FeCl3) flocculation and powdered activated carbon (PAC) adsorption were evaluated in terms of their capability in removing effluent organic matter (EfOM) and the characteristics of th
Shon, H., Vigneswaran, S., Ben Aim, R.M., Ngo, H., Kim, I.S. & Cho, J. 2005, 'Influence of flocculation and adsorption as pretreatment on the fouling of ultrafiltration and nanofiltration membranes: Application with biologically treated sewage effluent', Environmental Science & Technology, vol. 39, no. 10, pp. 3864-3871.
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Membrane fouling is a critical limitation on the application of membranes to wastewater reuse. This work aims to understand the fouling phenomenon which occurs in ultrafiltration (UF; 17500 molecular weight cutoff (MWCO)) and nanofiltration (NF; 250 MWCO
Guo, W., Shim, W.G., Vigneswaran, S. & Ngo, H. 2005, 'Effect of Operating Parameters in a Submerged Membrane Adsorption Hybrid System: Experimental and Mathematical Modelling', Journal of Membrane Science, vol. 247, no. 1-2, pp. 65-74.
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This study aims at developing a simple and practical mathematical model to predict the performance of a submerged membrane adsorption hybrid system (SMAHS). Adsorption equilibrium and kinetic studies were first carried out with powdered activated carbon (PAC) for removing, persisting organics from a synthetic wastewater. A series of short-term SMAHS experiments were conducted with preadsorption a[ different operating conditions such as aeration rate, backwash frequency, PAC dose and filtration flux. The Talu adsorption equilibrium and homogeneous surface diffusion model (HSDM) described well the isothermal adsorption behavior and adsorption kinetics. respectively The semi-empirical mathematical model formulated for membrane-adsorption system predicts successfully the performance of SMAHS in terms of total organic carbon (TOC) removal. A coefficient known as "membrane correlation coefficient (MCC)" introduced in the model was found to be very, useful in describing both the adsorption of organics adsorbed onto the PAC and onto the membrane surface. and separation of PAC (with organics adsorbed on it) by the membrane.
Guo, W., Vigneswaran, S. & Ngo, H. 2005, 'Effect of Flocculation and/or adsorption as pretreatment on the critical flux of crossflow microfiltration', Desalination, vol. 172, no. 1, pp. 53-62.
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Shon, H., Vigneswaran, S., Kim, H., Ngo, H. & Park, N. 2005, 'Comparison of nanofiltration with flocculation - microfiltration - photocatalysis hybrid system in dissolved organic matter removal', Filtration: International Journal for Filtration and Separation, vol. July, pp. 215-221.
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In this research, a NTR 729HF nanofiltration (NF) membrane was employed to remove synthetic organic matter (SOM) from wastewater. NF alone led to a removal of 92.4% of dissolved organic carbon (DOC). The performance of NF was compared with that of a microfiltration (MF) hybrid system consisting of FeCl3 flocculation, MF and photocatalysis. Flocculation and microfiltration followed by photocatalysis led to more than 96% dissolved organic carbon (DOC) removal. A detailed molecular weight (MW) distribution study of organic matter indicated that the photocatalysis initially breaks the large MW organics and then the small MW organics were removed by a photoreactor process. Flocculation with an optimum dose of FeCl3 (68 mg/L as FeCl3) gave rise to the highest removal of organics including small MW organics. The small MW organics remaining after the treatment of flocculation could successfully be removed by photocatalysis.
Shon, H., Vigneswaran, S., Ngo, H. & Aim, R.B. 2005, 'Is semi-flocculation effective as pretreatment to ultrafiltration in wastewater treatment?', Water Research, vol. 39, no. 1, pp. 147-153.
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In this study, ferric chloride (FeCl3) flocculation was used as a pretreatment to ultrafiltration (UF) in treating synthetic wastewater containing synthetic organic matter (SOM). The effect of flocculant dose was studied in terms of organic removal and m
Smith, P.J., Vigneswaran, S., Ngo, H., Ben-Aim, R. & Nguyen, H.T. 2005, 'Design of a generic control system for optimising back flush durations in a submerged membrane hybrid reactor', Journal Of Membrane Science, vol. 255, no. 38749, pp. 99-106.
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Organic fouling on the membrane can be minimised through powdered activated carbon (PAC) usage in the submerged membrane reactor to adsorb dissolved organic matter and reduce direct organic loading on the membrane. However, fouling cannot be totally alle
Shon, H., Vigneswaran, S., Ngo, H. & Kim, J.K. 2005, 'Chemical coupling of photocatalysis with flocculation and adsorption in the removal of organic matter', Water Research, vol. 39, no. 12, pp. 2549-2558.
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An experimental investigation was made to study the effects of chemical coupling of flocculation and adsorption with photocatalysis in treating persistent organic pollutants in wastewater. The photocatalysis alone showed initial reverse reaction when tit
Jegatheesan, V. & Vigneswaran, S. 2005, 'Deep Bed Filtration: Mathematical Models and Observations', Critical Reviews in Environmental Science and Technology, vol. 35, no. 6, pp. 515-569.
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Numerous mathematical models have been developed to evaluate both initial and transient stage removal efficiency of deep bed filters. Microscopic models either using trajectory analysis or convective-diffusion equations were used to compute the initial removal efficiency. These models predicted the removal efficiency under favorable filtration conditions quantitatively, but failed to predict the removal efficiency under unfavorable conditions. They underestimated the removal efficiency under unfavorable conditions. Thus, semi-empirical formulations were developed to compute initial removal efficiencies under unfavorable conditions. Also, correction for the adhesion of particles onto filter grains improved the results obtained for removal efficiency from the trajectory analysis. Macroscopic models were used to predict the transient stage removal efficiency of deep bed filters. The O'Melia and Ali(1) model assumed that the particle removal is due to filter grains as well as the particles that are already deposited onto the filter grain. Thus, semi-empirical models were used to predict the ripening of filtration. Several modifications were made to the model developed by O'Melia and Ali to predict the deterioration of particle removal during the transient stages of filtration. Models considering the removal of particles under favorable conditions and the accumulation of charges on the filter grains during the transient stages were also developed. This article evaluates those models and their applicability under different operating conditions of filtration
Shon, H., Vigneswaran, S., Kim, I.S., Cho, J. & Ngo, H. 2004, 'The effect of pretreatment to ultrafiltration of biologically treated sewage effluent: a detailed effluent organic matter (EfOM) characterization', Water Research, vol. 38, pp. 1933-1939.
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Shim, W.G., Chaudhary, D.S., Vigneswaran, S., Ngo, H., Lee, J.W. & Moon, H. 2004, 'Mathematical modeling of granular activated carbon (GAC) biofiltration system', Korean Journal Of Chemical Engineering, vol. 21, no. 1, pp. 212-220.
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In this study, a mathematical model of a fixed bed Granular Activated Carbon (GAC) biofiltration system was developed to predict the organic removal efficiency of the filter. The model consists of bulk transportation, adsorption, utilization, and biodegradation of organics. The variation of the specific surface area due to biofilm growth and the effect of filter backwash were also included in the model. The intrapellet diffusion and the diffusion of substrate in the biofilm were described by linear driving force approximation (LDFA) method. Biodegradation of organics was described by Monod kinetics. Sips adsorption isotherm was used to analyze the initial adsorption equilibrium of the system. The model showed that the organic removal efficiency of the biofilter greatly depends on the parameters related to the biological activities such as the maximum rate of substrate utilization (kmax) and biomass yield (Y) coefficients. Parameters such as suspended cell concentration (Xs) and decay constant (Kd) had little effects on the model simulation results. The filter backwash also had no significant impact on the performance of the biofilter.
Smith, P.J., Vigneswaran, S., Ngo, H., Ben-Aim, R. & Nguyen, H.T. 2004, 'Investigation of Membrane De-Clogging Techniques in the Submerged Filtration Absorption Hybrid System (SMFAHS)', Fluid/Particle Separation Journal, vol. 16, no. 2, pp. 165-173.
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Vigneswaran, S., Shon, H., Boothanon, H., Ngo, H. & Ben-Aim, R. 2004, 'Membrane-flocculation-adsorption Hybrid System in Wastewater Treatment: Micro and Nano Size Organic Matter Removal', Water Science and Technology, vol. 50, no. 12, pp. 265-271.
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Nguyen, V., Vigneswaran, S., Ngo, H., Pokhrel, D. & Viraraghavan, T. 2004, 'Iron Coated Sponge In Arsenic Removal', Fluid/Particle Separation Journal, vol. 16, no. 2, pp. 175-184.
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Guo, W., Vigneswaran, S., Ngo, H. & Chapman, H.A. 2004, 'Experimental Investigation Of Adsorption-Flocculatio-Microfiltration Hybrid System In Wastewater Reuse', Journal of Membrane Science, vol. 242, pp. 27-35.
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Hoang, T., Shon, H., Chaudhary, D.S., Vigneswaran, S. & Ngo, H. 2004, 'Granular Activated Carbon (GAC) Biofilter For Low Strength Wastewater Treatment', Fluid/Particle Separation Journal, vol. 16, no. 2, pp. 185-191.
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Nguyen, V., Chaudhary, D.S., Ngo, H. & Vigneswaran, S. 2004, 'Arsenic in water: Concerns and treatment technologies', Journal of Industrial and Engineering Chemistry, vol. 10, pp. 337-348.
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Shon, H., Guo, W., Vigneswaran, S., Ngo, H. & Kim, I.S. 2004, 'Effect of flocculation in membrane-flocculation hybrid system in water reuse', Separation Science And Technology, vol. 39, no. 8, pp. 1871-1883.
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Preflocculation reduces the fouling of membranes in cross-flow microfiltration (CFM) thus leading to high quality product water at economic filtration flux. As such, this hybrid system will have a major impact in treatingthe biologically treated sewage effluent. The preflocculation achieved through the floating medium flocculation (FMF) was found to increase the phosphorus removal up to 96%. The decline in microfiltration permeate flux with time was reduced by the incorporation of flocculation. However, the improvement in the removal of dissolved organic carbon (DOC) was marginal (from 20% with membrane alone to 46% with the membrane-flocculation hybrid system). The flocculation followed by adsorption as pretreatment helped to increase the DOC removal as high as 98%. Flocculation was found to remove more than 66% of colloidal effluent organic matter (EfOM). An attempt was also made to quantify the hydrophobic fraction in the pretreated effluent and to identify the molecular weight (MW) range of organics removed by the flocculation. The pretreatment of flocculation was found to remove 68.5%, 61.8%, and 62.9% of hydrophobic, hydrophilic, and transphilic organic matter. The MW size distribution analysis indicated that flocculation with ferric chloride removed a majority of organic matter in the MW range of 300-5000 Da.
Shon, H., Vigneswaran, S., Kim, I.S., Cho, J. & Ngo, H. 2004, 'The effect of pretreatment on the fouling of membranes: application in biologically treated sewage effluent', Journal Of Membrane Science, vol. 234, no. 1-2, pp. 111-120.
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Reuse of wastewater can help in maintaining environmental quality and relieving the unrelenting pressure on conventional and natural freshwater sources. Membrane processes find an important place in the wastewater treatment for reuse. Nonetheless, reverse osmosis (RO) and nanofiltration (NF), i.e. non-porous membranes require higher operational costs and energy. Thus, in this research NTR 7410 ultrafiltration (UF) membrane which is porous was used without and with pretreatment to treat biologically treated sewage effluent (BTSE). Four different pretreatment methods, namely, ferric chloride (FeCl3) flocculation, powdered activated carbon (PAC) adsorption, flocculation followed by adsorption, and granular activated carbon (GAC) biofilter were used in this study to compare their relative merits. Experimental results indicate that the most suitable pretreatment was flocculation followed by adsorption leading to a total organic carbon (TOC) removal of 90%. To assess the suitability of the membranes, it is important to conduct a detailed membrane characterization. The fouled NTR 7410 membrane surface was analyzed in terms of contact angle, zeta potential, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), flux decline, and TOC removal. The contact angle of the fouled membrane surface was lower than that of the clean membrane surface. This suggests that the majority of the foulants may have been the hydrophilic organic compounds such as polysaccharides, urea, etc. which are the extracellular enzyme of microorganisms in BTSE
Nguyen, M., Reynolds, N. & Vigneswaran, S. 2003, 'By-product recovery from cottage cheese production by nanofiltration', Journal Of Cleaner Production, vol. 11, no. 7, pp. 803-807.
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Chiemchaisri, C., Panchawaranon, C., Rutchatanunti, S., Kludpiban, A., Ngo, H. & Vigneswaran, S. 2003, 'Development of floating plastic media filtration system for water treatment and wastewater reuse', Journal Of Environmental Science And Health Part A-toxic/hazardous Substances & Environmental Engineering, vol. 38, no. 10, pp. 2359-2368.
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Chaudhary, D.S., Vigneswaran, S., Ngo, H., Kim, S.H. & Moon, H. 2003, 'Effects of biodegradation and background inorganic substances on granular activated carbon adsorption of wastewater', Separation Science And Technology, vol. 38, no. 11, pp. 2515-2531.
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Background inorganic substances are thought to disrupt the adsorption process used in wastewater treatment systems. In this study, a low-strength synthetic wastewater was investigated for biodegradation and adsorption onto granular activated carbon, with and without the presence of background inorganic compounds. Overall, organic compounds in the synthetic wastewater underwent slow biodegradation, but when a solution was prepared with only one or two individual organic components present in the wastewater, biodegradation ceased. This effect was noticed both in the presence and absence of inorganic compounds. The association theory was found to describe the overall adsorption equilibrium of the system better than the more commonly used Freundlich isotherm. The isotherm patterns of the synthetic wastewater indicated that the dissolved inorganic substances had unfavorable effects on the adsorption of dissolved organic substances.
Chaudhary, D.S., Vigneswaran, S., Jegatheesan, V., Ngo, H., Moon, H., Shim, W.G. & Kim, S.H. 2003, 'Granular activated carbon (GAC) adsorption in tertiary wastewater treatment: experiments and models', Water Science And Technology, vol. 47, no. 1, pp. 113-120.
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Li, H., Fane, T.G., Coster, H. & Vigneswaran, S. 2003, 'Observation of deposition and removal behaviour of submicron bacteria on the membrane surface during crossflow microfiltration', Journal Of Membrane Science, vol. 217, no. 1-2, pp. 29-41.
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The deposition and removal of submicron bacteria (SW8) has been examined by the direct observation through the membrane (DOTM) technique. The original DOTM was modified to incorporate fluorescence microscopy to better visualise the submicron material. The flux at which deposition commenced, the so-called critical flux, was visually identified before the transmembrane pressure indicated cake formation. After supercritical operation for about 15 min the flux was reduced to subcritical and then zero; slow cake removal was observed as distinct cylindrical rolling floc (about 50 ?m diameter) and aggregates. The extent of cake removal varied from about 90 to <5% depending on the ionic environment with low ions resulting in better removal. Cake formed over longer periods (upto 60 min) showed negligible removal. The critical fluxes of SW8 measured with DOTM increased with crossflow, but exhibited higher values than expected from their primary particle size.
Chaudhary, D.S., Vigneswaran, S., Ngo, H., Kim, S.H. & Moon, H. 2003, 'Comparison of Association Theory and Freundlich Isotherm For Describing Granular Activated Carbon Adsorption of Secondary Sewager Effluent', Journal of Environmental Engineering and Science, vol. 2, no. 2, pp. 111-118.
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Sundaravadivel, M. & Vigneswaran, S. 2003, 'Strategies for Waste Management in Small and Medium Towns of Developing Countries: A Case Study of India', Water Science and Technology, vol. 47, no. 12, pp. 277-283.
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Chaudhary, D.S., Vigneswaran, S., Ngo, H., Shim, W.G. & Moon, H. 2003, 'Granular Activated Carbon (GAC) Biofilter for Low Strength Wastewater', Environmental Engineering Research, vol. 8, no. 4, pp. 184-192.
Chaudhary, D.S., Vigneswaran, S., Ngo, H., Shim, W.G. & Moon, H. 2003, 'Biofilter in Water and Wastewater Treatment', Korean Journal of Chemical Engineering, vol. 20, no. 6, pp. 1054-1065.
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Ngo, H., Jegatheesan, V. & Vigneswaran, S. 2003, 'High Rate Filtration Using Bouyant Medium: Experiments and Mathematical Models', Water Intelligence Online, vol. N/A, no. NA, pp. 1-9.
Sundaravadivel, M. & Vigneswaran, S. 2003, 'Public Private Partnership Approach For Developing Urban Environmental Infrastructure', Journal of Indian Association for Environmental Management, vol. 30, no. 1, pp. 1-8.
Vigneswaran, S., Chaudhary, D.S., Ngo, H., Shim, W.G. & Moon, H. 2003, 'Application of a PAC-membrane hybrid system for removal of organics from secondary sewage effluent: Experiments and modelling', Separation Science And Technology, vol. 38, no. 10, pp. 2183-2199.
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As world supplies of clean, fresh water come under increasing pressure and the need for water reuse rises, membrane technology is becoming increasingly important as a possible solution. However, membrane fouling is a major obstacle to the successful operation of the membrane process in wastewater treatment. In this study, a submerged hollow-fiber membrane with powdered activated carbon (PAC) adsorption was investigated for the removal of organics from secondary sewage effluent from a sewage treatment plant. The use of PAC in the membrane system was found to be very effective, not only in removing refractory organics, but also in reducing membrane clogging. A simple mathematical model was developed to predict the effluent quality [in terms of total organic carbon (TOC)] of the submerged membrane-adsorption hybrid system.
Kim, S.H., Ngo, H., Chaudhary, D.S., Kim, J.C., Vigneswaran, S. & Moon, H. 2002, 'Characterisation procedure for absorption of DC (Dissolved Organic Carbon) from synthetic waste water', Korean Journal of Chemical Engineers, vol. 19, no. 5, pp. 888-894.
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Chapman, H.A., Vigneswaran, S., Ngo, H., Dyer, S. & Ben Aim, R.M. 2002, 'Pre-flocculation of secondary treated wastewater in enhancing the performance of microfiltration', Desalination, vol. 146, no. N/A, pp. 367-372.
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Thiruvenkatachari, R., Ngo, H., Hagare, P., Vigneswaran, S. & Ben Aim, R.M. 2002, 'Flocculation-cross-flow microfiltration hybrid system for natural organic matter (NOM) removal using hematite as a flocculent', Desalination, vol. 147, no. N/A, pp. 83-88.
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Chang, S., Fane, T.G. & Vigneswaran, S. 2002, 'Modeling and optimizing submerged hollow fiber membrane modules', AIChE Journal, vol. 48, no. 10, pp. 2203-2212.
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Chang, S., Fane, T.G. & Vigneswaran, S. 2002, 'Experimental assessment of filtration of biomass with transverse and axial fibres', Chemical Engineering Journal, vol. 87, no. N/A, pp. 121-127.
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Ngo, H., Vigneswaran, S., Hu, J.Y., Thirunavukkarasu, O. & Viraraghavan, T. 2002, 'A comparison of conventional and non-conventional treatment technologies on arsenic removal from water', Water Science & Technology: Water Supply, vol. 2, no. 5,6, pp. 119-125.
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Kim, S.H., Bidkar, A., Ngo, H., Vigneswaran, S. & Moon, H. 2001, 'Adsorption and mass transfer characteristics of Metsulfuron-Methyl on activated carbon', Korean Journal of Chemical Engineering, vol. 18, no. 2, pp. 163-169.
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Sundaravadivel, M. & Vigneswaran, S. 2001, 'Constructed wetlands for wastewater treatment', Critical Reviews in Environmental Science and Technology, vol. 31, no. 4, pp. 351-409.
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Sundaravadivel, M. & Vigneswaran, S. 2001, 'Waste water collection and treatment technologies for semi-urban areas of India: a case study', Water Science and Technology, vol. 43, no. 11, pp. 329-336.
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Jegatheesan, V. & Vigneswaran, S. 2000, 'Transient stage deposition of submicron particles in deep bed filtration under unfavourable conditions', Water Research, vol. Volume 34, no. 0, pp. 2119-2131.
Jegatheesan, V. & Vigneswaran, S. 2000, 'Surface coverage of filter medium in deep bed filtration: mathematical modelling and experiments', Separation Science and Technology, vol. Volume 35, no. 0, pp. 967-987.
Ngo, H., Vigneswaran, S., Kim, S.H., Bidkar, A. & Moon, H. 2000, 'Microfiltration - absorption hybrid system in organic removal from water', Water Science and Technology, vol. Volume 41, no. 0, pp. 51-57.
Vigneswaran, S., Ngo, H., Hashimoto, K., Hasegawa, T. & Watanabe, Y. 2000, 'High Rate Floating Medium Flocculation-filtration With In-line Polysilicato-iron (PSI) Addition', Environmental Technology, vol. 21, no. 3, pp. 317-325.
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The performance of a high rate floating medium flocculation-filtration system with an in-line addition of a silica-polymer compound, namely polysilicato-iron (PSI) has been investigated for water treatment. This study is intended to investigate the applicability of PSI as a sole flocculant or as a combined flocculant with an organic polymer in the downflow floating medium filter. The filter system was operated at a high loading rate of up to 60 m3 m-2 h-1. Filter column experiments were conducted at different PSI doses, filtration rates, filter depths and buoyant medium types and sizes. Results showed the filter system was able to yield uniform and filterable flocs (15 - 20 &Acirc;&micro;m), even at a very high filtration rate of 60 m-3 h-1, through out the filter run time of 4 hours. Better filter performance was obtained when: (i) polystyrene beads of 1.9 mm diameter or polypropylene beads of 3.8 mm diameter; (ii) an in-line single dosage of 2.5 mg l-1 PSI; (iii) in-line combined dosages of 1.5 mg l-1 PSI and 0.4-0.6 mg l-1 organic polymers (cationic polyacrylamides, cationic polystyrene or Pollyallylamine hydrochloride) were used. When PSI was introduced as a sole flocculant, more than 90% turbidity was removed from a 54 NTU artificial kaolin clay suspension at a filtration rate of 30 m-3 m-2h-1 with very low headloss development. Greater removals were achieved when SIF was used in combination with a polymer (e.g.greater than 95% turbidity removal). Frequent (once in every 90 minutes) but short duration backwash (less than 60 s) by air and water enables the system to maintain a superior effluent quality (e.g. turbidity less than 1 NTU) during the filter run. Backwash water requirement was very low (approximately 1%-2% of filtered water production). A lower amount of sludge was produced from the filter in case of combined PSI and organic polymer coagulant addition.
Sundaravadivel, M., Vigneswaran, S. & Doeleman, J.A. 2000, 'Waste management in semi-urban areas of India: appropriate technological strategies to overcome financial barriers', Environmental Engineering and Policy, vol. 2, no. 2, pp. 91-104.
The public health and environmental pollution problems due to inadequate treatment and inappropriate disposal of liquid and solid wastes generated in small and medium towns (referred to as semi-urban areas) of India receive insufficient attention. A field study of four towns in the State of Tamil Nadu was conducted to evaluate the current waste management practices in such semi-urban areas (SUAs). The study reveals that financial barriers for waste management arise due to a combination of policy and technological constraints. Based on the results of a preliminary waste characterization study and other observations made during the field study, reed bed channels and a semi-mechanized aerobic windrow composting process for the treatment of wastewater and municipal solid wastes, respectively, are recommended as appropriate technological options. The recommended technologies utilize existing arrangements for waste disposal, and aid an integrated resource recovery and reuse strategy that takes advantage of the geographic location and socioeconomic characteristics of SUAs to achieve lower waste management costs. Financial viability of the recommended technological approach is demonstrated through a comparative evaluation of competing treatment systems, and an estimation of costs and recoverable benefits resulting from waste reuse.
Kwon, D., Vigneswaran, S., Fane, T.G. & Ben Aim, R.M. 2000, 'Experimental determination of critical flux in cross-flow microfiltration', Separation and Purification Technology, vol. Volume 19, no. 0, pp. 169-181.
Li, H., Fane, T.G., Coster, H. & Vigneswaran, S. 2000, 'An assessment of depolorization models of cross-flow microfiltration by direct observation through membrane', Journal of Membrane Science, vol. Volume 172, no. 0, pp. 135-147.
Vigneswaran, S., Kwon, D., Ngo, H. & Hu, J. 2000, 'Improvement of microfiltration perfromance in water treatment: Is critical flux, a viable solution?', Water Science and Technology, vol. Volume 41, no. 0, pp. 309-310.
Jegatheesan, V. & Vigneswaran, S. 2000, 'Surface coverage of filter medium in deep bed filtration: Mathematical modeling and experiments', Separation Science and Technology, vol. 35, no. 7, pp. 967-987.
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This paper highlights the importance of surface coverage in modeling the removal of particles in deep bed filtration. A model that considers the saturation of sites on which particle deposition occurs is used. Experimental results obtained with monodispersed suspensions of 0.46 and 0.816 m latex particles at different influent concentrations and ionic strengths were used to calculate the fraction of filter grain surface (1) on which actual particle deposition occurs. This will be useful in evaluating the filter performance in terms of the utilization of available surface area of the filter medium. Further, the level of dendrite formation of particles on filter grains during filtration is expressed in terms of 1 and the specific surface coverage, (T) (the fraction of a filter grain surface that is covered by particles at time T, assuming that the filter grain is covered by a monolayer of particles). This can be used to compare the contribution of deposited particles in the removal efficiency of deep bed filtration for suspensions with different physical and chemical characteristics.
Vigneswaran, S., Jegatheesan, V. & Visvanathan, C. 1999, 'Industrial waste minimization initiatives in Thailand: concepts, examples and pilot scale trials', Journal of Cleaner Production, vol. 7, no. 1, pp. 43-47.
Industrial waste pollution control is a major issue in waste management. To comply with the specific effluent standards, industries are forced to treat their waste before discharge. This is neither a cost effective nor an environmentally friendly solution. The first part of this paper presents different techniques by which the waste minimization can be achieved with examples. The second part of the paper highlights the waste minimization efforts made in three different types of industries, namely paper and pulp, tapioca starch and palm oil
Vigneswaran, S. & Moon, H. 1999, 'Phosphorus Removal By Slag Experiments And Mathematical Modeling', Adsorption And Its Applications In Industry And Environmental Protection, Vol Ii Applications In Environmental Protection, vol. 120, pp. 533-569.
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Sundaravadivel, M., Doeleman, J.A. & Vigneswaran, S. 1999, 'Combined surface sewerage: a low-cost option for effective sanitation in semi-urban areas of India', Environmental Engineering and Policy, vol. 1, no. 3, pp. 181-189.
Current prescriptions for sanitation technologies in developing countries are predominantly in the context of either large cities or rural areas. In India, however, there are a large number of small cities and towns with population in the range of 20000&Acirc;&plusmn;100000 that account for over 50 million of the country's urban population. This paper discusses the inappropriateness (in terms of techno-economic viability and environmental desirability) of commonly recommended on-site sanitation technologies and capital intensive conventional sewage collection systems for these `semi-urban' areas. While emphasising the need for a different approach for provision of sanitation services to such cities and towns, it identifies the limitations of recent developments of non-conventional sewerage systems. Based on the field research carried out in four `semi-urban' towns in India, the paper proposes the concept of `combined surface sewerage' that can utilise existing infrastructure to a maximum to effect better sanitation at lower costs. The suggested system involves converting the existing open drains on the roadsides, as decentralized networks with simple structural modifications and covering them with concrete slabs. These decentralized networks would convey sullage, septic tank overflow and storm water run-off for appropriate low-cost treatment prior to disposal.
Vigneswaran, S., Ngo, H. & Lee, K.L. 1999, 'Effluent recycle and waste minimization in prawn farm effluent', Journal of Cleaner Production, vol. 7, no. 2, pp. 121-126.
Prawn farms withdraw huge quantities of sea water and discharge 5&acirc;30% of it back to the estuary during water exchange process. The effluent from the prawn ponds contains large quantities of solids, nitrogen, phosphorus and algae and it cannot be discharged into the estuary or ocean without proper effluent treatment. Sedimentation could form a partial treatment system. In this study, about 28&acirc;38% removal was achieved at an overflow rate of 40 m3/m2.d. Because of low loading, it requires a large area. Co-culture systems may be technically feasible but it is difficult to control the prawns growth. Considering the water quantity requirement, it is necessary to design a high rate treatment system to treat the effluent and recycle it in the system. A high rate floating medium filter led to 68% removal of suspended solids at 20 m3/m2.h and with a depth of 1.2 m. The removal efficiency increased when flocculant was added. A combined downflow floating medium and sand filter gave rise to almost 90% solids and phosphorus removal. Another way is to control the nutrient discharge by optimizing the feed and reducing its waste. &Atilde; 1999 Elsevier Science Ltd. All rights reserved.
Peiris, P., Bailey, J., Ngo, H. & Vigneswaran, S. 1998, 'Bacterial Removal From Secondary Sewage Effluent By A Combined Downflow Floating Medium Flocculatorperprefilter And Sand Filter', Indian Journal Of Engineering And Materials Sciences, vol. 5, no. 4, pp. 217-222.
semi pilot-scale study conducted with the combined downflow floating medium flocculatorperprefilter and sand filter indicated that, it is an effective filter system for removing bacteria from the secondary sewage effluent. Since the filter system can rem
Ngo, H. & Vigneswaran, S. 1998, 'Process Optimisation Of A Combined System Of Floating Medium And Sand Filter In Prawn Farm Effluent Treatment', Water Science And Technology, vol. 38, no. 4-5, pp. 87-93.
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A treatment technology known as "a combined system of floating medium and sand filter (FMSF)" was developed and tested successfully with prawn farm effluent. This system has a remarkable techno-economical advantages. Laboratory and semi pilot-scale studies were carried out to optimise the filter bed depth, backwash method and other operating conditions. The dewatering characteristics of sludge from filter backwash was also analysed. The filter was operated at a high rate. The experimental results indicated that: (i) in case of no in-line chemical addition, the smaller ratio between floating medium and sand filter depth gave rise better filter performance. At the filtration rate of 7.5 - 20 m3/m2.h and with an in-line chemical addition, the suitable depth of floating medium varied from 400-1000 mm for a sand filter depth of 400 mm; (ii) frequent (once in every 90-120 minutes) but short duration of backwash (not more than 60 seconds) was found to be suitable. During the backwash, the water and air were sent for 30 seconds in upward direction and then followed with upflow of water for another 30 seconds. Backwash water amount comprised only 1.2-1.8% of the filtered water production. A mechanical backwash system using rotating paddles is a promising alternative for floating medium filter; and (iii) the filterability of the sludge from filter backwash was low in case of no in-line chemical addition (specific resistance, r = 9.34 1010 m/kg) but improved with in-line flocculant addition (r = 3.07 109 - 1.29 1010 m/kg).
Kwon, D. & Vigneswaran, S. 1998, 'Influence Of Particle Size And Surface Charge On Critical Flux Of Crossflow Microfiltration', Water Science And Technology, vol. 38, no. 4-5, pp. 481-488.
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The effect of particle size and ionic strength of the feed suspension on critical flux was studied. The critical flux was defined in two different ways (strong and mild definition). The fouling, the increase of resistance (which is the basis of the mild definition of the critical flux) was relatively sensitive to the deposition of particles of 0.46 &Icirc;&frac14;m on the membrane of 0.2 &Icirc;&frac14;m mean pore. On the other hand, the deposition of large particles of 3.2 &Icirc;&frac14;m to a certain value on the membrane surface of 0.2 &Icirc;&frac14;m mean pore did not lead to the increase in resistance. In case of 11.9 &Icirc;&frac14;m particles, the transmembrane pressure did not increase even with significant amount of deposition of particles. The ionic strength of suspension had significant effect on the critical flux. For an ionic strength less than 1&Atilde;10&acirc;1.5 M, there was a decrease in the critical flux. This could be due to the dense layer of deposit which is the result of less diffuse layer thickness of particles. Above this ionic strength, a significant increase in critical flux was noticed which may be due to the aggregation of particles.
Li, H., Fane, T.G., Coster, H. & Vigneswaran, S. 1998, 'Direct Observation Of Particle Deposition On The Membrane Surface During Crossflow Microfiltration', Journal Of Membrane Science, vol. 149, no. 1, pp. 83-97.
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In the crossflow microfiltration of particles, a deposit cake layer tends to form on the membrane and this usually controls the performance of the filtration process. This paper presents observations of particle deposition on membrane surfaces using a non-invasive, in situ, continuous direct observation through the membrane (DOTM) technique. The particles used in the experiments were typical of microfiltration processes, yeast (mean diameter 5 &Icirc;&frac14;m) and latex beads (3, 6.4 and 12 &Icirc;&frac14;m). The filtration tests were conducted in the imposed flux mode, so that the flux could be controlled at, below, or above the &acirc;critical flux&acirc;. Below the critical flux, the particle deposition was negligible; near the critical flux the particle deposition was significant; and above the critical flux, particle layers were formed on the membrane surface. Rolling of the particles was observed during the filtration of 6.4 &Icirc;&frac14;m latex near the critical flux whereas a flowing cake layer was observed during the filtration of 3 &Icirc;&frac14;m latex. The particle size distribution of the deposited particles changed with the crossflow velocity, with smaller particles deposited on the membrane at higher crossflow velocity. Comparison of the normalised flux (J/&Icirc;P) with the membrane area coverage by the particles revealed that for filtration of latex particles &acirc;flux percentage (with respect to the clean membrane)&acirc; was marginally greater than the percentage of uncovered membrane area, whereas for filtration of yeast, the &acirc;flux percentage&acirc; was significantly less than the uncovered area percentage due to the deposition of smaller cell debris species. This paper demonstrates that DOTM is a powerful technique for the study of fundamentals of particle deposition and interactions between the particles and the membrane.
Lee, S., Vigneswaran, S. & Moon, H. 1997, 'Adsorption Of Phosphorus In Saturated Slag Media Columns', Separation And Purification Technology, vol. 12, no. 2, pp. 109-118.
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Adsorption of phosphorus (P as phosphates) in saturated slag media (dust and cake) columns was studied to assess the slag media's capability in removing P from wastewater. Prior to the experiments, slag media were completely washed to rinse off the soluble metal ions which are generally responsible for forming insoluble precipitates. Experimental data revealed that the adsorption capacities of washed slag media are still much higher than that of a sandy roam soil. Two dynamic models were tested for simulating the adsorption behavior of phosphorus in columns packed with slag media. The model employing the intraparticle transport through surface diffusion is successful, while a simplified model based on the linear driving force approximation (LDFA) could not predict the column behavior properly at low concentrations, particularly on the cake slag.
Jegatheesan, V. & Vigneswaran, S. 1997, 'Interaction Between Organic Substances And Submicron Particles In Deep Bed Filtration', Separation And Purification Technology, vol. 12, no. 1, pp. 61-66.
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Prasanthi, H., Vigneswaran, S. & Miller, S.C. 1997, 'Effect Of Particle Concentration On The Entire Cycle Of Filtration', Water Science And Technology, vol. 35, no. 8, pp. 91-102.
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In this present study, submicron polystyrene latex beads of sizes 0.46 &Icirc;&frac14;m and 0.825 &Icirc;&frac14;m were used to study the effect of concentration on the entire cycle of filtration. Experiments were carried out at constant mass, number and surface area as influent concentrations in order to observe the variation in filtration of the two sizes of particle. At constant mass concentrations, the initial removal was found to be higher for smaller particles (0.46 um) (in the submicron range); but when the number or surface area of particles was considered, it was found to be higher for larger particles (0.825 &Icirc;&frac14;m). The transient stage removal was found to increase with an increase in particle size, either with constant mass, number or surface area as an influent concentration. The Vigneswaran and Chang 1986 model was used to quantify the results. The model parameters estimated using the experimental results are useful in quantifying and understanding the performance of the filter
Jegatheesan, V. & Vigneswaran, S. 1997, 'The Effect Of Concentration On The Early Stages Of Deep Bed Filtration Of Submicron Particles', Water Research, vol. 31, no. 11, pp. 2910-2913.
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The removal of mono-dispersed suspensions of 0.46 &Icirc;&frac14;m and 0.816 &Icirc;&frac14;m particles in the early stages of deep bed filtration was found be higher at a certain range of influent mass concentration. For both equal number concentrations and equal surface area concentrations of mono-dispersed suspensions of 0.46 &Icirc;&frac14;m and 0.816 &Icirc;&frac14;m particles, the removal of particles of 0.816 &Icirc;&frac14;m size was higher during the early stages of filtration than 0.460 &Icirc;&frac14;m particles, at lower concentrations. Specific surface coverage was higher for 0.816 &Icirc;&frac14;m particles compared to 0.460 &Icirc;&frac14;m particles, for influents of these mono-dispersed particles having same number concentrations. However, it was similar for influents of these mono-dispersed particle suspensions, having equal surface area concentration.
Vigneswaran, S., Ngo, H. & Jeyaseelan, J. 1997, 'Application Of Non-conventional Filtration Technologies In Pollution Control', Environmental Monitoring And Assessment, vol. 44, no. 1-3, pp. 231-240.
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Deep bed filtration is becoming increasing important in wastewater treatment particularly in tertiary treatment as stringent water quality standards are emphasized. A detailed pilot-scale filtration study conducted with secondary effluent in a sewage treatment plant indicated that tertiary filtration with prior alum flocculation is capable of producing high quality effluent, particularly an effluent with phosphorus content of less than 0.3 mg/L (Vigneswaran and Ngo, 1994). Main problem of dual media filter has been rapid headloss development thus frequent backwash requirement. To overcome this problem two independent experimental studies were conducted: one with mobile bed filtration (MBF) and the other with combined downflow floating medium flocculator/prefilter (DFF) and coarse sand filter (CSF) system. A semi-pilot scale mobile bed filtration study conducted using oxidation pond effluent indicated that MBF with contact-flocculation arrangement was good in removing COD, T-P and turbidity with practically no headloss development. Sand of 0.6-0.84 nm dia and 50 cm depth was sufficient to reduce the COD and P from 55 mg/L and 4.5 mg/L to 15 mg/L and 0.5 mg/L respectively at a filtration rate of 7.5 m3/m2.h. Another experimental study with combined DFF-CSF system indicated that the DFF with in-line flocculation addition is a good pretreatment unit to reduce the phosphate upto 80-90%. The fact that DFF resulted in uniform filterable-flocs, it can also successfully be used as a static flocculator/prefilter unit. The introduction of DFF on top of a coarse sand filter increased the filter run time and removal efficiency (more 90-95% of NH3-N and T-P removal respectively). Most importantly, the backwashing of this system was achieved with small quantity of water at low backwash indicated that the removal efficiency was also superior with this system apart from the major advantage of low operating cost.
Ben-Aim, R., Vigneswaran, S., Prasanthi, H. & Jegatheesan, V. 1997, 'Influence Of Particle Size And Size Distribution In Granular Bed Filtration And Dynamic Microfiltration', Water Science And Technology, vol. 36, no. 4, pp. 207-215.
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Panicle size and size distribution is an important parameter in solid liquid separation process especially in granular bed filtration and in dynamic microfiltration. This paper discusses their effects on the above processes from extensive experimental data obtained. In granular bed filtration, the experimental results showed that the initial efficiency follows the pattern reported by previous experimental and theoretical studies, i.e., lower efficiency for particles which fal! in the range of critical size of 1 &Icirc;&frac14;m. However, the particle removal during the transient stage increased with an increase in particle size for the range of sizes studied. An attempt was made to quantify these effects in granular bed filtration using semi-empirical approach. In dynamic membrane filtration also, the particle size plays a major role in the retention. However, despite the relative thickness of the membrane (compared to particle size) dynamic microfiltration appears more as a sieving process; the retention is mainly related to the largest pore size
Lee, S., Vigneswaran, S. & Chung, Y. 1997, 'A Detailed Investigation Of Phosphorus Removal In Soil And Slag Media', Environmental Technology, vol. 18, no. 7, pp. 699-709.
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Kinetic studies on phosphorus (P as orthophosphate) sorption onto a sandy loam soil from North Sydney, Australia, and a slag (waste products from the BHP steel industry, Australia) revealed that more than 90% of the P was adsorbed within 70 and 12 hours for the soil and slag respectively. The pH of the P solution played a critical role in the rate of P removal. Removal was at a minimum at pH 2. Dominant removal mechanism of P at pH less than 8 was physical sorption, while it was chemical precipitation at pH greater than 10. Adsorptive capacity of the slag was 225 and 53 times of that of the soil for the static and dynamic systems respectively. Breakthrough curves obtained from the column experiments are S-shaped and more spreaded with the decrease of influent P concentration. Simulated results from an equilibrium sorption model (ESM) and Freundlich isotherm constants did not always match the corresponding experimental breakthrough data. Mobility of P is restricted by the adsorbent due to its high sorption capacity of P.
Kwon, D., Vigneswaran, S., Ngo, H. & Shin, H. 1997, 'An Enhancement Of Critical Flux In Crossflow Microfiltration With A Pretreatment Of Floating Medium Flocculatorperprefilter', Water Science And Technology, vol. 36, no. 12, pp. 267-274.
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In this study, use of a combined system of flocculation-microfiltration was assessed for its capability in removing solids and organics. The improvement of flux by the preflocculation was also investigated. The experimental set-up consisted of (i) Millipore flat plate microfiltration module with constant permeate withdrawal arrangement and (ii) a floating medium flocculator/filter consisting of polypropylene beads as a pretreatment. Commercial ferric chloride(FeCl3) was used for flocculation. The purpose of floating medium filter was primarily to produce filterable flocs and also to achieve partial solids and organics removal. The critical flux of kaolin clay suspension of 10 - 100mg/L was measured for membrane of pore size of 0.2m in the presence of 0 - 4mg/L of fulvic acid in the suspension without any pretreatment. The critical flux was found to decrease with the increase in kaolin clay concentration. The results also indicated that there was no significant effect of organic (fulvic acid) concentration on critical flux. The pretreatment of floating medium filter alone without flocculant addition removed 30 - 40% of solids and resulted in a significant improvement of critical flux in crossflow microfiltration. Degree of solids and organic removal and the variation in critical flux were then studied in detail for the preflocculated/filtered kaolin clay suspension in the presence of organics. The pretreatment of flocculation/prefiltration removed approximately 50% of organics while producing uniform microflocs of 13 - 16 m size. In addition, it enhanced the critical flux by 70% and resulted in 30 - 70% of the remaining organic removal in the crossflow microfiltration.
Ngo, H., Vigneswaran, S. & Jegatheesan, V. 1996, 'Mathematical Modelling Of Downflow Floating Medium Filter (dff) With In-line Flocculation Arrangement', Water Science And Technology, vol. 34, no. 3-4, pp. 355-362.
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A laboratory-scale set-up consisting of rapid mixing device and floating medium filter was used to study the use of a downflow floating medium filter (DFF) with an in-line flocculation arrangement as a static flocculator and a prefilter. The semi-empirical mathematical model formulated incorporates flocculation within the filter, particle/floc attachment onto the filter and the detachment of flocs from the medium. The mathematical model for filtration takes into account the expansion of the filter bed. The removal efficiency of DFF and headloss development were successfully simulated for different conditions of filtration velocity, filter depth and influent suspended solids (SS). The values of attachment coefficient ap and headloss coefficient were found to be independent of filtration velocity, filter depth and influent SS concentration.
Ngo, H. & Vigneswaran, S. 1996, 'Application Of Downflow Floating Medium Flocculatorperprefilter (dff) - Coarse Sand Filter (csf) In Nutrient Removal', Water Science And Technology, vol. 33, no. 8, pp. 63-70.
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In this study, the applicability and the advantages of the downflow floating medium filter (DFF) in wastewater treatment were examined. The experimental results indicated that the DFF with in-line fiocculation addition is a good pretreatment unit to reduce phosphorus load (up to 80&acirc;89% removal). The DFF also resulted in uniform filterable-floes of 32&acirc;42 (am throughout the filter run. Thus it can also successfully be used as a flocculator. The backwashing of floating medium was achieved with a small quantity of water and at low backwash velocity. The introduction of floating medium filter bed on top of a coarse sand filter unit (CSF) increased the filter run time and removal efficiency (more than 87 and 94% of NH3-N and T-P removal respectively), particularly at a low filtration rate (5 m3/m2.h).
Chang, J., Tsai, L.J. & Vigneswaran, S. 1996, 'Experimental Investigation Of The Effect Of Particle Size Distribution Of Suspended Particles On Microfiltration', Water Science And Technology, vol. 34, no. 9, pp. 133-140.
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Suspended particle size is one of the main factors which affect the performance of the microfiltration. Experimental results with bi and trimodal suspensions of latex particles clearly showed that the permeate flux and the quality were significantly affected by the particle size and its distribution, especially when the particle size was smaller than the pore size of the membrane.
Vigneswaran, S., Prasanthi, H. & Miller, S.C. 1996, 'Implications Of Particle Size To Transient Stage Of Deep Bed Filtration', Korean Journal Of Chemical Engineering, vol. 13, no. 6, pp. 565-572.
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This study was aimed at investigating the effect of particle size, mostly in the submicron range, on break-through stage of filtration. Latex beads, with diameters ranging from 0.46- to 2.967-&Icirc;&frac14;m were filtered through filter grains of diameters 0.1-, 0.175- and 0.45-mm. Experimental conditions were chosen so as to obtain breakthrough curves. The experimental results showed that the initial efficiency follows the pattern reported by previous experimental and theoretical studies, i.e., lower efficiency for 0.825-&Icirc;&frac14;m particles which fall in the range of critical size. However, the particle removal during the transient stage increased with an increase in particle size for the range of sizes studied. This pattern is qualitatively confirmed by the theoretical predictions of Vigneswaran and Chang (1986) model. This study also provides experimental verification of the effect of the ratio of particle size and grain size at different stages of filtration.
Vigneswaran, S., Boonthanon, S. & Prasanthi, H. 1996, 'Filter Backwash Water Recycling Using Crossflow Microfiltration', Desalination, vol. 106, no. 1-3, pp. 31-38.
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Experiments were carried out using crossflow microfiltration (CFMF) for treating filter backwash water from a water treatment plant, It was found that CFMF with backflush is technically feasible and highly efficient. The condition of the backflush freque
Lee, S., Vigneswaran, S. & Bajracharya, K. 1996, 'Phosphorus Transport In Saturated Slag Columns Experiments And Mathematical Models', Water Science And Technology, vol. 34, no. 1-2, pp. 153-160.
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Excessive phosphorus (P as orthophosphate) is one of the major pollutants in natural water that are responsible for algal blooms and eutrophication. P removal by slag is an attractive solution if the P sorption capacity of slag is significant. To design an efficient land treatment facility, basic information on the behaviour of P in the media-water environment is required. In this study, detailed column experiments were conducted to study the P transport under dynamic condition, and mathematical models were developed to describe this process. The column experiments conducted with dust and cake waste products (slag) from a steel industry as adsorbing media indicated that they had higher sorption capacity of P than that of a sandy loam soil from North Sydney, Australia. P transport in the dust and cake columns exhibited characteristic S-shaped or curvilinear breakthrough curves. The simulated results from a dynamic physical non-equilibrium sorption model (DPNSM) and Freundlich isotherm constants satisfactorily matched the corresponding experimental breakthrough data. The mobility of P is restricted by the adsorbents and it is proportional to the sorption capacity of them.
Ngo, H. & Vigneswaran, S. 1995, 'Application Of Floating Medium Filter In Water And Waste-water Treatment With Contact-flocculation Filtration Arrangement', Water Research, vol. 29, no. 9, pp. 2211-2213.
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Conventional granular filtration, although successfully used in water treatment and tertiary wastewater treatment, suffers from some disadvantages such as limited retention capacity and high energy requirement for backwashing. Use of floating filter medium overcomes these shortcomings especially when direct filters are used in the treatment plants. A laboratory-scale study carried out indicated that the floating medium filter with downflow direct filter arrangement was a good pretreatment unit to reduce the pollutant load in rapid filters used as polishing filter units. Due to its ability to form uniform micro-flocs of the order of 26&acirc;40 &Icirc;&frac14;m throughout the filter run, the floating medium filter can serve as an excellent static flocculator.
Ngo, H., Vigneswaran, S. & Miller, S.C. 1995, 'Optimization Of Direct-filtration - Experiments And Mathematical-models', Environmental Technology, vol. 16, no. 1, pp. 55-63.
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A laboratory-scale set-up consisting of helicoidal flocculator and rapid sand filter was used to study the implication of flocs in direct filtration for optimizing the design parameters. Two different methods, one using a flocculation and filtration mathematical model and other using Ives' filterability number were used to optimize the direct filtration. The results indicated that (i) there is an optimum range of floc size which resulted in prolonged filter run, (ii) alum dose played an important role in floc size and density, (iii) a good compromise between velocity gradient and flocculation time is essential in optimizing the direct filtration performance, and (iv) the optimum filter depth increased with higher filtration rate. The simulation results indicated that a floc size of 62 &Acirc;&micro;m was found to be optimum for direct filtration which corresponded to 2.5 minutes of flocculation time at the velocity gradient values of 26.5 s-1. This optimum value shifted with filter medium size, depth and filtration velocity. On the other hand, Ives' filterability number indicated that a floc size of 57-76 &Acirc;&micro;m was found to be optimum which corresponded to 4.8 - 7.2 minutes of flocculation time and at a velocity gradient values of 33.6 - 79.6 s-1. These methods will help in optimizing the design parameters of direct filtration in a rational manner using minimum number of experiments with the specific raw water and chemicals.
Vigneswaran, S., Ngo, H.H., Maheswaran, S., Ostarcevis, E. & Potter, A. 1995, 'Improved phosphorus and bacterial removal in sewage treatment plants: A pilot-scale study', Water Treatment, vol. 10, no. 1, pp. 75-80.
Studies have shown, superior removal of phosphorus (up to the level of less than 0.03 mg/L in the treatment plant effluent) is essential to the improvement of water quality of Hawkesbury-Nepean River in New South Wales, Australia. But the chemical precipitation presently adopted in the secondary treatment step can only decrease phosphorus level to about 1 mg/L. A detailed pilot-scale filtration study conducted with secondary effluent in a sewage treatment plant indicated that tertiary filtration with a prior alum flocculation is essential in achieving superior B removal. The best results were obtained with sand (ES = 0.85-0.95; U = 1.25-1.50 mm) as filter medium and 4.4 min of preflocculation. Alum at 40 mg/L was found to be the most suitable chemical. Dual media filter also produced comparable effluent quality (although slightly inferior) while leading to longer filter runs.
Prasanthi, H., Vigneswaran, S., Waite, T.L. & Ben-Aim, R. 1994, 'Filtration Of Submicron Particles - Effect Of Ionic-strength And Organic-substances', Water Science And Technology, vol. 30, no. 9, pp. 149-158.
Hematite (-Fe2O3) suspension was used in this study to investigate the effects of aggregate size and solution chemical characteristics on particle removal and headloss development in a deep bed filter. When electrolyte (KCl) concentration in the suspension was increased from 0-80 mM, the size of hematite aggregates in suspension increased from 85 to 990 nM but had no significant effect on zeta potential. It was found that at low KCl concentrations (0-10 mM), the initial removal is governed by surface chemical properties while at higher concentrations (40-80 mM), the effect of particle size (steric effect) predominates. The transient stage filter performance was found to be controlled by the favourable chemical conditions prevailing in the filtration system rather than the size of the particles. Studies of the effect of a natural organic material (fulvic acid) on particle removal indicated that fulvic acid at low concentrations (less than 0.75 mg/L) enhanced particle aggregation and improved filtration efficiency. At concentrations higher than 2 mg/L, it was found to increase the stability of particles thus affecting filtration efficiency.
Miller, S.C., Fujiwara, O., Verink, J. & Vigneswaran, S. 1994, 'Water-treatment System-design For Turbidity Removal .2. Optimization', Journal Of Environmental Engineering-asce, vol. 120, no. 4, pp. 921-942.
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In this second part of the paper, optimization models for design of water treatment plants for turbidity removal are discussed. Application of the models is illustrated with a case study. The results from the case study indicate cost differences of about 16&acirc;64%, solely due to change in the influent particle size distribution (PSD), with higher cost of treatment for the influents with relatively greater fraction of fine particles. The system configuration, level of treatment, and design and operating parameters are found to be different for each influent PSD. Use of other parameters like turbidity units, suspended solids and volume average diameter are unable to explain this variation. The influence of PSD on the total cost decreases with inflow. Integration of process optimization in system optimization is justified as the different design and operating parameters are selected under each level of treatment. The cost of sludge treatment accounts to about 30&acirc;50% of the total plant cost
Miller, S.C., Vigneswaran, S., Verink, J. & Fujiwara, O. 1994, 'Water-treatment System-design For Turbidity Removal .1. Simulation', Journal Of Environmental Engineering-asce, vol. 120, no. 4, pp. 900-920.
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Although a number of optimization models have been developed for the least-cost design of wastewater-treatment systems, very few models are available for water-treatment systems. The present study proposes a method toward optimal design of water-treatment systems, considering integration of process optimization in system optimization; particle-size distribution (PSD) for process design and selection; relatively general simulation models; membrane processes in the alternative evaluation; sludge treatment/handling processes; multicriteria for alternative evaluation; and algorithms for process and system optimization. The paper is divided into two parts. The first part presents the important features of simulation models along with the simulation results and the second part highlights the optimization models and algorithms used for the optimal design. Results from the simulation study indicate the importance of influent particle-size distribution on the performance of flocculation, sedimentation, and filtration processes. Recycling of the sludge sidestreams from gravity/centrifugal separation processes to the head of the water-treatment plant and the filtrate disposal into sewers are economically and environmentally justified.
Dharmappa, H.B., Fujiwara, O., Verink, J. & Vigneswaran, S. 1994, 'Water-treatment-system design for turbidity removal. II: Optimization', Journal of Environmental Engineering (United States), vol. 120, no. 4, pp. 921-942.
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In this second part of the paper, optimization models for design of water treatment plants for turbidity removal are discussed. Application of the models is illustrated with a case study. The results from the case study indicate cost differences of about 16-64%, solely due to change in the influent particle size distribution (PSD), with higher cost of treatment for the influents with relatively greater fraction of fine particles. The system configuration, level of treatment, and design and operating parameters are found to be different for each influent PSD. Use of other parameters like turbidity units, suspended solids and volume average diameter are unable to explain this variation. The influence of PSD on the total cost decreases with inflow. Integration of process optimization in system optimization is justified as the different design and operating parameters are selected under each level of treatment. The cost of sludge treatment accounts to about 30-50% of the total plant cost. &copy; ASCE.
Dharmappa, H.B., Vigneswaran, S., Verink, J. & Fujiwara, O. 1994, 'Water-treatment-system design for turbidity removal. I: Simulation', Journal of Environmental Engineering (United States), vol. 120, no. 4, pp. 900-920.
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Although a number of optimization models have been developed for the least-cost design of wastewater-treatment systems, very few models are available for water-treatment systems. The present study proposes a method toward optimal design of water-treatment systems, considering integration of process optimization in system optimization; particle-size distribution (PSD) for process design and selection; relatively general simulation models; membrane processes in the alternative evaluation; sludge treatment/handling processes; multicriteria for alternative evaluation; and algorithms for process and system optimization. The paper is divided into two parts. The first part presents the important features of simulation models along with the simulation results and the second part highlights the optimization models and algorithms used for the optimal design. Results from the simulation study indicate the importance of influent particle-size distribution on the performance of flocculation, sedimentation, and filtration processes. Recycling of the sludge sidestreams from gravity/centrifugal separation processes to the head of the water-treatment plant and the filtrate disposal into sewers are economically and environmentally justified. &copy; ASCE.
Waite, T.D., Amal, R., Ngo, H. & Vigneswaran, S. 1993, 'Effects Of Adsorbed Organic-matter On Size, Structure And Filterability Of Iron Oxyhydroxide Flocs', Water Science And Technology, vol. 27, no. 11, pp. 133-142.
The presence of organic matter may modify the nucleation and aggregation process of the oxide flocculants being used in water treatment processes. Such organic induced modifications in floc behaviour may necessitate a variation in treatment process. The effects of adsorbed fulvic acid, a naturally occurring organic acid, on the aggregation and filtration of hematite particles are investigated. Evidence is presented to show that the structure of the aggregates formed in the presence of fulvic acid depends on the aggregation kinetics and the amount of the fulvic acid. The presence of fulvic acid also greatly affects the filter efficiency due in part to the reversal of charge on the particles but also to the variables of particle size and structure. Since the filtration and the removal of these particles depends on their characteristic size, shape and chemical nature, the studies of the aggregation kinetics and the resulting structure of organic influenced particles are relevant to the removal of pollutants from surface waters (A).
Aim, R.B., Liu, M. & Vigneswaran, S. 1993, 'Recent Development Of Membrane Processes For Water And Waste-water Treatment', Water Science And Technology, vol. 27, no. 10, pp. 141-149.
Membranes are presently used at industrial scale for water and waste water treatment, but still for limited production. More knowledge of hydrodynamic phenomena has recently resulted in significant technical improvements (backflush, unsteady flow). Howev
Chiemchaisri, C., Yamamoto, K. & Vigneswaran, S. 1993, 'Household Membrane Bioreactor In Domestic Waste-water Treatment', Water Science And Technology, vol. 27, no. 1, pp. 171-178.
The activated sludge process coupled with hollow fiber membrane for solid-liquid separation was applied to treat low strength domestic wastewater. Pilot-scale experimental unit use in this study consisted of 2 modules of 0.03 mum pore size with 9 m2 surf
Miller, S.C., Verink, J., Fujiwara, O. & Vigneswaran, S. 1993, 'Optimal-design Of A Flocculator', Water Research, vol. 27, no. 3, pp. 513-519.
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An approach is presented for the least cost design of a flocculator with respect to flocculation time and velocity gradient, in order to obtain a desired effluent condition, which is measured using the negative slope of power law distribution function (&Icirc;&sup2;). The model proposed is a non-linear programming problem involving a non-linear constraint, which in turn comprises a verified simulation model. The case study demonstrates the existence of a relationship between design criterion and design parameters. It also shows that the optimal solution is sensitive to influent particle size distribution (PSD) and particle contact efficiency (&Icirc;&plusmn;).
Miller, S.C., Verink, J., Fujiwara, O. & Vigneswaran, S. 1992, 'Optimization Of Granular Bed Filtration Treating Polydispersed Suspension', Water Research, vol. 26, no. 10, pp. 1307-1318.
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The need for economic optimization of a filter unit leading to its least cost design with respect to filtration velocity, run time, depth and medium size has long been identified but there are no algorithms towards this end. In this study, an algorithm incorporating a NLP (non-linear programming) software (NPSOL&acirc;System Optimization Laboratory, Stanford University, Calif.) and response surface methodology (RSM) is presented for optimal design and operation of a filter unit. Also, the simulation model included in the optimization takes into account the polydispersity of the influent. The optimization results obtained using laboratory data have shown that the filter design and operating parameters are highly dependent on the particle size distribution (PSD) of the influent. The cost of the filter unit with influent having the same total particles mass concentration and turbidity but with greater fraction of fine particles was about 46% higher. This demonstrates the importance of incorporating PSD instead of suspended solids (SS), turbidity units (TU) or volume average diameter in the design and operation of filter units. The proposed approach, however, is applicable only for single medium filters. Further research is warranted to extend it to dual and tri media filters.
Miller, S.C., Verink, J., Ben-Aim, R., Yamamoto, K. & Vigneswaran, S. 1992, 'A Comprehensive Model For Cross-flow Filtration Incorporating Polydispersity Of The Influent', Journal Of Membrane Science, vol. 65, no. 1-2, pp. 173-185.
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A semi-empirical model is presented for the prediction of foulant deposit thickness and concentration, and thereby, predicting the permeate flux in cross-flow microfiltration and ultrafiltration. The scope of the model is limited to colloidal suspensions (i.e. non-diffusive solutes) and its hallmark is its applicability to polydispersed influents. The theoretical model was verified with experimental observations and found to yield a fairly good agreement with an error less than 62% of the average flux over 100 min of filtration. However, evaluation of model coefficients a and b is necessary through laboratory studies. The model was successfully used to predict the effect of particle size distribution (PSD) on permeate flux. The simulation results corroborate the contention that the long-term flux decline is due to the reduction is foulant deposit permeability via infiltration of fines into the cake, thereby demonstrating the importance of influent particle size distribution (PSD) on foulant deposit permeability. The proposed model is a first step towards the modeling of polydispersed influents. As such there is a lot of scope for further refinements which is briefly discussed.
Vigneswaran, S. & Dharmappa, H.B. 1992, 'Industrial waste minimisation: concepts and technology', National Conference Publication - Institution of Engineers, Australia, no. 92 pt 5, pp. 103-107.
As the industrialisation takes a leap ahead threatening to incur serious damage to environment, it is necessary to protect the environment through more conservative efforts. Towards this end traditional 'End-of-the-pipe treatment' is grossly inadequate and to achieve the desired results, it is necessary to integrate the pollution control right into the heart of the industrial processes. This not only results in less pollution but also helps in recycling of valuable nonrenewable resources, often with a considerable amount of cost saving. This technology is called 'Waste Minimisation' or 'Low or No Waste Technology (LNWT)'. This paper highlights some of the advantages of LNWT and the methods to implement LNWT in industry. The methodologies are illustrated with some examples. Finally criteria for comparison of various methodologies and the need for research and development are brought out.
Vigneswaran, S., Casiano, V. & Polprasert, C. 1991, 'Application Of Coarse-media Slow Sand Filtration In Aquaculture', Water Science And Technology, vol. 23, no. 10-12, pp. 1817-1824.
Laboratory experiments were carried out with pilot-scale experimental unit of Coarse Media Slow Sand Filter (CMSSF). A 2.7 m high filter column with a diameter of 0.56 m was operated with the filter media size of 1-2 mm and media depth of 1.0 m at filtr
Manandhar, U.K. & Vigneswaran, S. 1991, 'Effect of media size gradation and varying influent concentration in deep-bed filtration: Mathematical models and experiments', Separations Technology (Incorporated into Separation and Purification Technology after 1996), vol. 1, no. 4, pp. 178-183.
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A new model for deep-bed filtration that considers the presence of medium size gradations and the variation of influent concentration with time is proposed. In formulating the model, the rate of filtration is assumed to be either enhanced or retarded by the deposited particles, and the increase in the headloss necessary to maintain a given flow is estimated from the Kozeny equation. Simulated filter performance based on the model was found to agree with pilot plant data on the filtration of clarified effluent from a water treatment plant.
Vigneswaran, S. & Chang, J. 1991, 'Effect of media pore size distribution on deep-bed filtration', Separations Technology (Incorporated into Separation and Purification Technology after 1996), vol. 1, no. 5, pp. 259-266.
One important parameter of filtration, the media pore size distribution, has not been explicitly considered in modeling deep-bed filtration models by previous investigators. In this study, we propose, based on the hypothesis of O'Melia-Ali and the use of the effective medium approximation theory, a new transient-state model and examine the effect of the media pore size distribution on filter performance. From the simulation results based on six different pore size distribution functions, it is clear that the pore size distribution plays an important role in determining the removal efficiency as well as headloss development
Boonthanon, S., Dharmappa, H.P., Vigneswaran, S. & Ben Aim, R. 1991, 'Use of a backflush technique in cross-flow microfiltration for treating natural water and filter backwash wastewater in water works', Aqua London, vol. 40, no. 2, pp. 103-109.
Cross-flow microfiltration (CFMF), is useful in treating natural water for potable purpose, as it is very efficient in completely removing all particles within the size range 0.01-10 m, including bacteria. It can also be used to treat the filter backwash wastewater produced in a water-treatment plant. Although CFMF is a very effective technique for treating natural water and filter backwash wastewater, problems like fouling, deposition and internal clogging affect the efficiency of the process. The backflush technique in CFMF is one of the most useful techniques for minimizing these problems. In this study, laboratory-scale CFMF experiments were carried out using backflush technique in treating natural water and filter backwash wastewater to study the effect of operating parameters like backflush frequency and backflush duration on CFMF performance. In the case of natural-water treatment, the permeate flux increased by 24% using the backflush technique and in the case of backwash wastewater treatment, it was found to increase by 400%.
Boonthanon, S., Hwan, L.S., Vigneswaran, S., Aim, R. & More, J. 1991, 'Application of pulsating cleaning technique in crossflow microfiltration', Filtration and Separation, vol. 28, no. 3, pp. 199-201.
Crossflow microfiltration (CFMF), is a pressure driven membrane process allowing better permeate flux by shearing action of flow. It can remove most of the impurities found In water and wastewater. But there are still major problems to be solved caused by fouling, deposition and internal clogging, which reduce the efficiency of separation. The pulsation cleaning technique is one of the methods used to avoid or minimise these drawbacks. Laboratory scale microfiltration using a clay suspension was carried out to study the effect of the pulsation cleaning technique on overall CFMF performance at various pulsation times of flux. It was found that the higher permeate flux was obtained when the operation of pulsation was more frequent. Also the study performed showed that this technique improved the permeate flux by 80%. &copy; 1991.
Mahinthakumar, G. & Vigneswaran, S. 1990, 'Solute Transport Through Saturated Soils - A Study Of The Physical Nonequilibrium Model', Water Air And Soil Pollution, vol. 51, no. 1-2, pp. 161-180.
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Chang, J. & Vigneswaran, S. 1990, 'Ionic strength in deep bed filtration', Water Research, vol. 24, no. 11, pp. 1425-1430.
The removal efficiency of particles in deep bed filtration depends on both transport and attachment mechanisms of particles. The particle attachment mechanisms depend mainly on chemical characteristics of aqueous phase, suspended particles and filter media. In this study, two different suspensions were used to study the effect of ionic strength on the particle removal efficiency. The ionic strength of suspension was varied by adding a known amount of sodium chloride. The removal efficiencies were related to ionic strength and zeta potential. The clean filter bed efficiency and removal efficiency during the ripening period for various strengths were quantitatively related to the two model coefficients appearing in the O'Melia-Ali model. These model coefficients represent the filter medium-particle and particle-particle attachments. This type of quantification of the effect of ionic strength in terms of filter efficiency is very useful in filter design and operation control.
Vigneswaran, S. & Joshi, D. 1990, 'Laboratory development of a small-scale iron removal plant for rural water supply', Aqua, vol. 39, no. 5, pp. 300-308.
This paper outlines the construction and performance of a simple iron and manganese removal plant, suitable for small community water supply in rural areas, where groundwater is extensively used for drinking and other domestic purposes. The unit consists of a contact filter to oxidize iron and manganese and a matrix filter to remove these pollutants. This paper presents a design approach for a new type of fixed-bed filter, known as matrix filter, for the removal of suspended solids, iron, manganese and coliform. -Authors
Bajracharya, K. & Vigneswaran, S. 1990, 'Competitive adsorption of solutes in saturated soil columns: Mathematical model and experiments', Environmental Technology (United Kingdom), vol. 11, no. 1, pp. 25-32.
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Results of competitive adsorption column experiments of Cadmiua (Cd) and Zinc (Zn) are discussed. A mathematical model termed as Competitive Dynamic Adsorption Model (CDAM) to predict the solute concentration in the multisolute system is presented. The CDAM is verified using concentration history curves of Cd and Zn obtained from saturated column experiments. &copy; 1990 Taylor and Francis Group, LLC.
Bajracharya, K. & Vigneswaran, S. 1990, 'Adsorption of cadmium and zinc in saturated soil columns: Mathematical models and experiments', Environmental Technology (United Kingdom), vol. 11, no. 1, pp. 9-24.
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It vas found from experiments that adsorption of Cd and Zn in the dynamic system was higher than that in the static systea. Equilibrium Adsorption Model (EAM) and Two Site Adsorption Model (TSAM) have been validated with the observed concentration history curves of Cd and Zn. In most of the cases the EAM model with dynamic isotherm constants fitted the observed concentration history curves satisfactorily. In those where EAM did not fit well (using Dynamic isotherm constants), the TSAM predicted more accurately. The general conclusion is that for highly adsorbing solutes, EAM is a simple and quite satisfactory model for the prediction of concentration profiles both temporally and spatially. &copy; 1990 Publications Division Selper Ltd.
Vigneswaran, S., Jing, S.C. & Janssens, J.G. 1990, 'Experimental investigation of size distribution of suspended particles in granular bed filtration', Water Research, vol. 24, no. 7, pp. 927-930.
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Laboratory-scale experimental studies were conducted to show the effect of size distribution of particles in granular bed filtration. The results showed that the investigation of granular bed filtration based merely on the mean size is inadequate as particles of different size have different removal efficiencies. This study also showed that there is an improvement in fine particles removal efficiency when they are present with particles in polydispersed suspension. &copy; 1990.
Vigneswaran, S., Muttamara, S. & Srianandakumar, K. 1989, 'Low waste technologies in selected industries', ENVIRON. SANIT. REV., no. 27, pp. 1-86.
Expectations of increasingly higher living standards along with rapid industrial developments have resulted in a dramatic rise in the level of pollution of the natural environment. At the same time it is generally accepted that a healthy life requires good quality environment and hence the control of pollution. Today, environmental scientists are in the process of combining all these three aspects (industrialization, clean environment and healthy life) based on the principle of using low and non-waste technology. The philosophy behind this is 'to produce better while polluting less'. In practice, this technology and its application go by many names such as low and non-waste technology (LNWT), clean technology, pollution prevention, waste reduction, waste recycling, resource utilization, etc. The basic goal of LNWT is to eliminate the by-product formation that is discarded as waste. The objectives of LNWT are therefore to avoid inefficiencies in production which result in excess of waste and to recover the useful components of the waste in such a way that they can either be reused or recycled to minimize the emission of pollutants to the environment. LNWT alleviates disposal costs, liability risk and resource cost.
Visvanathan, C., Aim, R.B. & Vigneswaran, S. 1989, 'Application of cross-flow electro-microfiltration in chromium wastewater treatment', Desalination, vol. 71, no. 3, pp. 265-276.
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Cross-flow microfiltration (CFMF) was experimentally studied for the separation of precipitates of chromium hydroxide. Although this process enables one to obtain chromium-free filtrate, a disadvantage is that the filtration flux declines rapidly due to membrane fouling. In order to avoid this fouling problem and increase the filtration flux, an electric field was applied across the membrane as an antifouling technique (cross-flow electro-microfiltration-CFEMF). The surface charges of the precipitates were modified by adding a dispersant. The experimental results indicate that this modified process of CFEMF is highly effective in reducing the membrane fouling, which eventually leads to a remarkable filtration flux increase. The application of this antifouling technique of CFEMF is cited only for the suspensions containing charged particles and colloids. Nevertheless, the process of modification of surface charge with a dispersant permits us to use this technique with a wide variety of suspensions. &copy; 1989.
Vigneswaran, S. & Chang, J.S. 1989, 'Experimental testing of mathematical models describing the entire cycle of filtration', Water Research, vol. 23, no. 11, pp. 1413-1421.
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Two mathematical models developed based on different concepts to describe the entire cycle of filtration were tested with experimental results. The concept of Model I is based on the detachment of deposited particles. The degree of detachment was assumed proportional to the hydraulic gradient and number of particles already retained on the filter grain. Model II is based on the concept that there exists a maximum limit on particle deposition on the filter grain. It was found that Model I, based on the detachment assumption, can simulate better than Model II does. This may be an experimental proof for the concept of detachment which is now agreed by most of the researchers. The ultimate specific deposit was estimated experimentally for different filtration velocities to give a qualitative justification on the applicability range of the proposed models. &copy; 1989.
Vigneswaran, S. & Mora, J.C. 1989, 'Energy recovery considerations for membrane separation process', RERIC International Energy Journal, vol. 11, no. 1, pp. 1-15.
This paper gives an overview of different membrane processes like reverse osmosis ultrafiltration with direct and indirect energy recovery systems. The feasibility of using direct and indirect energy recovery in each membrane process and a few examples are presented. The importance of cogeneration technology and pervaporation, and principles and examples are also introduced.
Vigneswaran, S., Muttamara, S., Srianandakumar, K. & Ben Aim, R. 1989, 'Low waste technologies in selected industries', Environmental Sanitation Reviews, no. 27.
The paper examines the need for low and non-waste technology. The methods to achieve low-waste technology are given. Selected unit operations are discussed for suspended solids removal and dissolved solids removal. The applications in selected industries include: pulp and paper mill industry; tapioca starch industry; palm oil refinery wastewater treatment; food industry; textile industry; electroplating industry; distillery industry.
Vigneswaran, S. & Tien, C. 1988, 'EMPIRICAL CORRELATION FOR ESTIMATING PRESSURE DROP ACROSS CLOGGED FILTERS.', Aqua (Oxford), no. 3, pp. 110-115.
Empirical correlations for estimating pressure drop in clogged filters were established. The correlations are based on pressure drop data collected from filtration of kaolin clay suspensions under different operating conditions. A simple procedure for applying the correlations is outlined.
Vigneswaran, S. & Tulachan, R.K. 1988, 'Mathematical modelling of transient behaviour of deep bed filtration', Water Research, vol. 22, no. 9, pp. 1093-1100.
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This study proposes a mathematical model based on the concept that there exists a maximum limit on particle deposition on the filter grain, to describe the entire cycle of filtration. The three model coefficients appearing in this mathematical model were calculated for different operating conditions using experimental results obtained from a filter 2 cm in depth. Although these model coefficients were different for different operating conditions, a uniform trend was observed in the variation of model parameters with operating conditions. &copy; 1988.
Vigneswaran, S. & Pandey, J.R. 1988, 'ASSESSING THE SUITABILITY OF MEMBRANES FOR MICROFILTRATION - AN EMPIRICAL APPROACH.', Filtration and Separation, vol. 25, no. 4, pp. 253-255.
Very little work has been done on the performance of cross-flow microfiltration during the filter run. The authors suggest an empirical methodology to characterize membrane performances by using standard curves. A procedure is developed to establish standard curves for cross-flow microfiltration. The standard curve arrived at gives a reasonable prediction for the performance of CMF, but a larger number of data have to be analyzed with respect to the standard curve obtained before it can be used for practical purposes.
Vigneswaran, S. & Kiat, W.Y. 1988, 'Detailed investigation of effects of operating parameters of ultrafiltration using laboratory-scale ultrafiltration unit', Desalination, vol. 70, no. 1-3, pp. 299-316.
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Cross flow ultrafiltration is a pressure driven membrane process in which the fluid to be filtered flows parallel to the membrane surface. The formation of filter cake can be reduced by scouring force of the flow, thus better permeate rate is obtained. Laboratory-scale ultrafiltration experiments with Polyvinyl Alcohol (PVA) solution of known molecular weight was carried out to study the membrane filter performances with respect to operating parameters. These operating parameters included, membrane molecular weight cut off size, molecular weight of PVA, influent concentration, cross flow velocity and applied pressure. It was discovered that clogging in the membrane occurs quite slowly during first 30 minutes, and quasi-steady state was noticed normally after 50 minutes of filtration time. In this study, steady state flux data were used to develop semi-empirical and empirical correlations which are useful in the optimum design of ultrafiltration. &copy; 1988.
Vigneswaran, S. & Suazo, R.B. 1987, 'A detailed investigation of physical and biological clogging during artificial recharge', Water, Air, and Soil Pollution, vol. 35, no. 1-2, pp. 119-140.
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An attempt was made to study the physical and biological clogging during artificial recharge with an experimental model that simulates the artificial recharging practice by considering factors such as effective infiltration rate, media size and depth, and inundation period. Recharging was investigated experimentally in terms of suspended solids (SS) removal, 3-day biological oxygen demand (BOD3) removal and chemical oxygen demand (COD) removal at different sand sizes and infiltration rates. To understand the physical phenomenon involved, the effect of suspended solids concentration and initial infiltration rate on cumulative discharge was studied and verified using a simple mathematical model. The simulated cumulative discharge profiles were comparable with the experimental profiles. This indicates that an empirical relationship can be successfully used to predict the biological clogging at different recharge rates. The effect on headloss was also discussed. &copy; 1987 D. Reidel Publishing Company.
Vigneswaran, S. & Tien, C. 1987, 'Transient behavior of deep-bed filtration of brownian particles', Chemical Engineering Science, vol. 42, no. 11, pp. 2729-2739.
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A new model is proposed for deep-bed filtration of Brownian particles. The model incorporates the unit-collector concept for estimating particle deposition rates and the application of the effective medium approximation (EMT) theory for predicting the instantaneous pressure drop across the filter bed. Case studies are used to show the effects of various variables on filter performance. &copy; 1987.
Vigneswaran, S. & Jing Song, C. 1986, 'Mathematical modelling of the entire cycle of deep bed filtration', Water, Air, and Soil Pollution, vol. 29, no. 2, pp. 155-164.
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This study proposes a mathematical model which was developed from the 'O'Melia-Ali' and 'Adin-Rebhun' models, to describe the entire filtration cycle. The three coefficients appearing in this model were calculated for different operating conditions using 30 cm depth filter experiments. The concentrations and headloss profiles simulated for different filter depths using these coefficients were found to fit very well with experimental results. &copy; 1986 D. Reidel Publishing Company.
Vigneswaran, S., Balasuriya, B.L.N. & Viraraghavan, T. 1986, 'Anaerobic wastewater treatment - Attached growth and sludge blanket process', ENVIRON. SANIT. REV., vol. No. 19-20, pp. 1-101.
Vigneswaran, S. & Setiadi, T. 1986, 'Flocculation study on spiral flocculator', Water, Air, and Soil Pollution, vol. 29, no. 2, pp. 165-188.
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Traditionally, the Jar Test has been used to assess the suitability of flocculation treatment for a given raw water. Unfortunately, the Jar Test suffers from a number of disadvantages. The new method of assessment of flocculation, Spiral Flocculator, has been claimed to be a better method than the Jar Test apparatus and a good method for continuous assessment of flocculation. This study compares the performance of Spiral Flocculator and Jar Test, and mathematical modeling of the Spiral Flocculator performance. The experiments conducted reveal that the Spiral Flocculator has a better effective energy dissipation compared to that of Jar Test. However, the size of flocs in Spiral Flocculator seems to be overestimated relative to the real flocculator and Jar Test. &copy; 1986 D. Reidel Publishing Company.
Vigneswaran, S. & Visvanathan, C. 1985, 'Mathematical modelling of mobile bed filtration with contact flocculation - filtration arrangement', Effluent & Water Treatment Journal, vol. 25, no. 9, pp. 309-314.
Mathematical formulation of suspended solids removal in contact-flocculation filtration is complex since both flocculation and suspended solids removal occur within the filter bed itself. In this study, a mathematical formulation based on O'Melia and Alis' model was developed for contact flocculation-filtration incorporating the flocculation phenomena in ideal conditions. This model was then extended to mobile bed filtration with contact flocculation-filtration arrangement and verified with laboratory-scale mobile bed filter experimental results obtained.
Vigneswaran, S., Thiyagaram, M. & Aim, R.B. 1985, 'Mathematical modeling of radial flow filtration and its application to groundwater recharge problems', AIChE Journal, vol. 31, no. 11, pp. 1929-1933.
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Vigneswaran, S. & Aim, R.B. 1985, 'The influence of suspended particle size distribution in deepbed filtration', AIChE Journal, vol. 31, no. 2, pp. 321-324.
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Vigneswaran, S., Notthakun, S. & Thanh, N.C. 1984, 'Flocculation time optimization in direct water filtration', Effluent & Water Treatment Journal, vol. 24, no. 7, pp. 270-274.
Direct filtration consists of unit operations without the use of sedimentation. Past experiences indicate that this is an economical solution for low turbid waters. A laboratory-scale experimental study has been carried out to see the effects of flocculation gradient, flocculation time and coagulant dose on direct filtration performance. The results indicated that there exists a threshold flocculation time for which filtration run lengths are longest and that this threshold increases with decrease in alum dose and flocculation gradient. The determination of the threshold flocculation time for the water to be treated from a laboratory-scale direct filtration study, therefore, would lead to an optimal solution for direct filtration.
Vigneswaran, S. & Thiyagaram, M. 1984, 'Application of filtration theories to ground water recharge problems', Water, Air, and Soil Pollution, vol. 22, no. 4, pp. 417-428.
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A mathematical model is formulated for filtration of different flow conditions (radial flow, spherical flow and combined radial and vertical downwards flow) from O'Melia's model for deep bed filtration. The simple ground water recharge problems with the above mentioned flow conditions are also presented. The radial flow mathematical model was verified using bench-scale radial flow experiments. The removal efficiency and headless in spherical flow and combined radial - vertical downwards flow models with equal bed volume were simulated. &copy; 1984 D. Reidel Publishing Company.
Vigneswaran, S., Visvanathan, C. & Ben Aim, R. 1984, 'Optimization of sand recycle rate in mobile bed filtration', Effluent & Water Treatment Journal, vol. 24, no. 12, pp. 457-460.
Rapid sand filters have been used as a final clarifying step in municipal water treatment plants since the early 1900's. The mobile-bed deep filter process uses compressed air to lift and separate retained particles in the sand. Although reports indicate that this type of filter operates continuously without any problem, sand recycling was found to be an energy consuming process. It is therefore essential to optimize the sand recycle rate. In this study the optimum recycle rate for a particular filtration rate was estimated from the 'filter clogging front theory' using fixed bed experimental results.
Vigneswaran, S. & Mazumdar, B. 1984, 'Intermixing of media in dual media filters', Effluent & Water Treatment Journal, vol. 24, no. 9, pp. 341-345.
Though many theoretical formulations exist to determine the size ratio of anthracite to sand grains which cause mixing in dual media filters, there is no specific means to quantify the degree of mixing with variation of size ratio. This suggests a method of quantifying the degree of mixing, and attempts to determine the effect of intermixing on effluent quality and headloss development. A mathematical model has been formulated to explain the observed experimental results.
Vigneswaran, S., Tam, D.M. & Visvanathan, C. 1983, 'Water filtration technologies for developing countries', ENVIRON. SANIT. REV., vol. 10 . 12.
Vigneswaran, S. & Perera, Y.A.P. 1982, 'CONVENTIONAL, UPFLOW, AND RADIAL FILTERS: COMPARISON & MATHEMATICAL MODELLING.', Effluent & Water Treatment Journal, vol. 22, no. 10, pp. 377-381.
This paper compares radial and upflow filters with conventional filters based on head loss development and the number of bed volumes filtered during a filter run. Mathematical formulations of K. J. Ives are used to study conventional and upflow filters. The model parameters obtained from conventional filters are used to predict the radial filter performance
Thanh, N.C., Vigneswaran, S. & Polprasert, C. 1979, 'OPTIMIZATION OF DUALMEDIA FILTER PERFORMANCE', JAWRA Journal of the American Water Resources Association, vol. 15, no. 5, pp. 1459-1465.
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ABSTRACT: Rapidrate filter with sand or anthracite as filter media was studied at filtration rates of 4.5 and 9.0 m3/m2h. Different parameters were evaluated by adopting a proposed simplified model. A suitable combination of anthracitesand as filter media was given by using corresponding filter parameters of singlemedium filters and breakeven optimization technique. Copyright &copy; 1979, Wiley Blackwell. All rights reserved