Dr. Tien-Vinh Nguyen is currently a senior lecturer at the Faculty of Engineering and IT (FEIT) and a core member of Center for Technology in Water and Wastewater (CTWW) at the University of Technology, Sydney (UTS), Australia and UTS-VNU Joint Technology and Innovation Research Centre.
His research interests include water and wastewater treatment and reused technologies, desalination and sludge dewatering. He has published more than 60 refereed journal papers in several reputable journals such as in Bioresource Technology, Journal of Membrane Science, Journal of Hazardous Materials, and Chemical Engineering Journal. He has been involved in a number of research projects as an investigator (Google, DFAT, CRC Care, National Centre of Excellence in Desalination, Sydney Water Corporation). He also has experience supervising (as the principal and co-supervisor) for PhD and master students.
He has strong collaborative connections with water authorities, and shire councils in Australia and organisations in developing countries, especially in Vietnam. He has helped establish the collaborative research activities between UTS and the Vietnam Academy of Science and Technology (VAST) and Vietnam National University (VNU).
His solutions on arsenic removal in Vietnam has received the 2008 East Asia & Pacific Honour Award - Applied Research Award from International Water Association and also was selected as one of three overseas solutions in the Vietnam Golden Book of Creativity 2017.
Can supervise: YES
Water and wastewater treatment and reuse: adsorption, membrane, biological technologies
Decentralised Environmental Systems
Industrial Water Pollution Control Engineering
Water Supply and Wastewater Engineering
Hien, NT, Lan, HN, Huu, TV, Thi, DN, Thi, HVN, Thi, HHC, Tien, VN, Van, TT, Xuan, HV & Aziz, KHH 2020, 'Heterogeneous catalyst ozonation of Direct Black 22 from aqueous solution in the presence of metal slags originating from industrial solid wastes', SEPARATION AND PURIFICATION TECHNOLOGY, vol. 233.View/Download from: Publisher's site
Hoang, LP, Nguyen, TMP, Van, HT, Hoang, TKD, Vu, XH, Nguyen, TV & Ca, NX 2020, 'Cr(VI) Removal from Aqueous Solution Using a Magnetite Snail Shell', WATER AIR AND SOIL POLLUTION, vol. 231, no. 1.View/Download from: Publisher's site
Nguyen, TH, Tran, HN, Vu, HA, Trinh, MV, Nguyen, TV, Loganathan, P, Vigneswaran, S, Nguyen, TM, Trinh, VT, Vu, DL & Nguyen, THH 2020, 'Laterite as a low-cost adsorbent in a sustainable decentralized filtration system to remove arsenic from groundwater in Vietnam.', The Science of the total environment, vol. 699, pp. 134267-134267.View/Download from: Publisher's site
In the Red River Delta, Vietnam, arsenic (As) contamination of groundwater is a serious problem where more than seventeen million people are affected. Millions of people in this area are unable to access clean water from the existing centralized water treatment systems. They also cannot afford to buy expensive household water filters. Similar dangerous situations exist in many other countries and for this reason there is an urgent need to develop a cost-effective decentralized filtration system using new low-cost adsorbents for removing arsenic. In this study, seven locally available low-cost materials were tested for arsenic removal by conducting batch adsorption experiments. Of these materials, a natural laterite (48.7% Fe2O3 and 18.2% Al2O3) from Thach That (NLTT) was deemed the most suitable adsorbent based on arsenic removal performance, local availability, stability/low risk and cost (US$ 0.10/kg). Results demonstrated that the adsorption process was less dependent on the solution pH from 2.0 to 10. The coexisting anions competed with As(III) and As(V) in the order, phosphate > silicate > bicarbonate > sulphate > chloride. The adsorption process reached a fast equilibrium at approximately 120-360 min, depending on the initial arsenic concentrations. The Langmuir maximum adsorption capacities of NLTT at 30 °C were 512 μg/g for As(III) and 580 μg/g for As(V), respectively. Thermodynamic study conducted at 10 °C, 30 °C, and 50 °C suggested that the adsorption process of As(III) and As(V) was spontaneous and endothermic in nature. A water filtration system packed with NLTT was tested in a childcare centre in the most disadvantaged community in Ha Nam province, Vietnam, to determine arsenic removal performance in an operation lasting six months. Findings showed that the system reduced total arsenic concentration in groundwater from 122 to 237 μg/L to below the Vietnam drinking water standard of 10 μg/L.
Nguyen, TTQ, Loganathan, P, Nguyen, TV & Vigneswaran, S 2020, 'Removing arsenic from water with an original and modified natural manganese oxide ore: batch kinetic and equilibrium adsorption studies.', Environmental science and pollution research international, vol. 27, no. 5, pp. 5490-5502.View/Download from: Publisher's site
Arsenic contamination of drinking water is a serious water quality problem in many parts of the world. In this study, a low-cost manganese oxide ore from Vietnam (Vietnamese manganese oxide (VMO)) was firstly evaluated for its performance in arsenate (As(V)) removal from water. This material contains both Mn (25.6%) and Fe (16.1%) mainly in the form of cryptomelane and goethite minerals. At the initial As(V) concentration of 0.5 mg/L, the adsorption capacity of original VMO determined using the Langmuir model was 0.11 mg/g. The modified VMOs produced by coating VMO with iron oxide (Fea-VMO) and zirconium oxide (Zra-VMO) at 110 °C and 550 °C achieved the highest As(V) adsorption capacity when compared to three other methods of VMO modifications. Langmuir maximum adsorption capacities of Fea-VMO and Zra-VMO at pH 7.0 were 2.19 mg/g and 1.94 mg/g, respectively, nearly twenty times higher than that of the original VMO. Batch equilibrium adsorption data fitted well to the Langmuir, Freundlich, and Temkin models and batch kinetics adsorption data to pseudo-first order, pseudo-second order, and Elovich models. The increase of pH progressively from 3 to 10 reduced As(V) adsorption with a maximum reduction of 50-60% at pH 10 for both original and modified VMOs. The co-existing oxyanions considerably weakened the As(V) removal efficiency because they competed with As(V) anions. The competition order was PO43- > SiO32- > CO32- > SO42-. The characteristics of the original and modified VMOs evaluated using SEM, FTIR, XRD, XRF, surface area, and zeta potential explained the As(V) adsorption behaviour.
To, VHP, Nguyen, TV, Bustamante, H & Vigneswaran, S 2020, 'Effects of extracellular polymeric substance fractions on polyacrylamide demand and dewatering performance of digested sludges', Separation and Purification Technology, vol. 239.View/Download from: Publisher's site
© 2020 Elsevier B.V. High polymer demand in sludge conditioning is an intractable aspect of the water industry. This study investigated the effects of extracellular polymeric substances (EPS) fractions on polyacrylamide demand for conditioning and dewatering performance. Specifically, it examined aerobically and anaerobically digested sludges from seven full-scale wastewater treatment plants (WWTPs). Our study successfully quantified the contributions of soluble EPS to polyacrylamide demand during conditioning and explained the role of tightly bound EPS (TB-EPS) in determining the digested sludges’ dewatering performance. Results show that the concentrations of soluble EPS in the sludges varied between 92 and 1148 mg/L. Experimental results also demonstrated that between 25% and 80% of polyacrylamides used for conditioning were wasted in “parasitic” reactions with soluble EPS. The residual cationic polyacrylamide left in solution, after the parasitic reactions, was substantial and varied between 35 and 254 mg/L. Despite this outcome, the zeta potential values of dewatered sludge cakes remained negative, i.e. between −24 and −35 mV. These indicated that the residual soluble cationic polyacrylamides would not have been absorbed on the negatively charged sludge particles. This explained the relatively poor performance of the dewatering stage in the treatment plants studied. Furthermore the results suggested the TB-EPS attached to the sludge particles would be responsible for the poor dewatering. We postulated that the TB-EPS would gelify and immobilize the water surrounding the sludge particles. Our study suggested that new and more effective polymers for conditioning are needed to both: (i) reduce polymer demand; and (ii) improve the dewatering performance.
Bui, HH, Ha, NH, Nguyen, TND, Nguyen, AT, Pham, TTH, Kandasamy, J & Tien, VN 2019, 'Integration of SWAT and QUAL2K for water quality modeling in a data scarce basin of Cau River basin in Vietnam', ECOHYDROLOGY & HYDROBIOLOGY, vol. 19, no. 2, pp. 210-223.View/Download from: Publisher's site
Kalaruban, M, Loganathan, P, Nguyen, TV, Nur, T, Hasan Johir, MA, Nguyen, TH, Trinh, MV & Vigneswaran, S 2019, 'Iron-impregnated granular activated carbon for arsenic removal: Application to practical column filters.', Journal of Environmental Management, vol. 239, pp. 235-243.View/Download from: Publisher's site
Arsenic is a major drinking water contaminant in many countries causing serious health hazards, and therefore, attempts are being made to remove it so that people have safe drinking water supplies. The effectiveness of arsenic removal from As(V) solutions using granular activated carbon (GAC) (zero point of charge (ZPC) pH 3.2) and iron incorporated GAC (GAC-Fe) (ZPC pH 8.0) was studied at 25 ± 1 °C. The batch study confirmed that GAC-Fe had higher Langmuir adsorption capacity at pH 6 (1.43 mg As/g) than GAC (1.01 mg As/g). Adsorption data of GAC-Fe fitted the Freundlich model better than the Langmuir model, thus indicating the presence of heterogeneous adsorption sites. Weber and Morris plots of the kinetic adsorption data suggested intra-particle diffusion into meso and micro pores in GAC. The column adsorption study revealed that 2-4 times larger water volumes can be treated by GAC-Fe than GAC, reducing the arsenic concentration from 100 μg/L to the WHO guideline of 10 μg/L. The volume of water treated increased with a decrease in flow velocity and influent arsenic concentration. The study indicates the high potential of GAC-Fe to remove arsenic from contaminated drinking waters in practical column filters.
Nur, T, Loganathan, P, Ahmed, MB, Johir, MAH, Tien, VN & Vigneswaran, S 2019, 'Removing arsenic from water by coprecipitation with iron: Effect of arsenic and iron concentrations and adsorbent incorporation', CHEMOSPHERE, vol. 226, pp. 431-438.View/Download from: Publisher's site
To, VHP, Nguyen, TV, Bustamante, H & Vigneswaran, S 2019, 'Deleterious effects of soluble extracellular polymeric substances on polyacrylamide demand for conditioning of anaerobically digested sludge', Journal of Environmental Chemical Engineering, vol. 7, no. 2.View/Download from: Publisher's site
© 2019 Elsevier Ltd. All rights reserved. High polyacrylamide (polymer) demand for conditioning of sludge, especially anaerobically digested sludge (ADS), is a major issue for the water industry. Currently, this problem is being investigated and the reasons for doing so are varied. It has been demonstrated that excess amounts of soluble extracellular polymeric substances (EPS) can lead to high polymer demand for conditioning. This study developed a simple and unique yet effective method for quantifying the contribution of soluble EPS to conditioning polymer demand. It did this by measuring absorbance at 191.5 nm wavelength of the supernatant derived from conditioned ADS. Experimental results confirmed that approximately 87 wt% of soluble EPS interacted with polyacrylamides during the conditioning process. Furthermore, they revealed that a specified amount of soluble EPS could not be removed by polymer flocculation despite high polymer dosage. This study concluded that about 86 wt% of the polyacrylamide used for conditioning was consumed solely by soluble EPS. These results confirm the important role of reducing this EPS fraction in ADS in order to curtail significant chemical costs for sludge conditioning and dewatering.
Tran, HN, Nguyen, DT, Le, GT, Tomul, F, Lima, EC, Woo, SH, Sarmah, AK, Nguyen, HQ, Nguyen, PT, Nguyen, DD, Nguyen, TV, Vigneswaran, S, Vo, D-VN & Chao, H-P 2019, 'Adsorption mechanism of hexavalent chromium onto layered double hydroxides-based adsorbents: A systematic in-depth review.', Journal of Hazardous Materials, vol. 373, pp. 258-270.View/Download from: Publisher's site
An attempt has been made in this review to provide some insights into the possible adsorption mechanisms of hexavalent chromium onto layered double hydroxides-based adsorbents by critically examining the past and present literature. Layered double hydroxides (LDH) nanomaterials are typical dual-electronic adsorbents because they exhibit positively charged external surfaces and abundant interlayer anions. A high positive zeta potential value indicates that LDH has a high affinity to Cr(VI) anions in solution through electrostatic attraction. The host interlayer anions (i.e., Cl-, NO3-, SO42-, and CO32-) provide a high anion exchange capacity (53-520 meq/100 g) which is expected to have an excellent exchangeable capacity to Cr(VI) oxyanions in water. Regarding the adsorption-coupled reduction mechanism, when Cr(VI) anions make contact with the electron-donor groups in the LDH, they are partly reduced to Cr(III) cations. The reduced Cr(III) cations are then adsorbed by LDH via numerous interactions, such as isomorphic substitution and complexation. Nonetheless, the adsorption-coupled reduction mechanism is greatly dependent on: (1) the nature of divalent and trivalent salts utilized in LDH preparation, and the types of interlayer anions (i.e., guest intercalated organic anions), and (3) the adsorption experiment conditions. The low Brunauer-Emmett-Teller specific surface area of LDH (1.80-179 m2/g) suggests that pore filling played an insignificant role in Cr(VI) adsorption. The Langmuir maximum adsorption capacity of LDH (Qomax) toward Cr(VI) was significantly affected by the natures of used inorganic salts and synthetic methods of LDH. The Qomax values range from 16.3 mg/g to 726 mg/g. Almost all adsorption processes of Cr(VI) by LDH-based adsorbent occur spontaneously (ΔG° <0) and endothermically (ΔH° >0) and increase the randomness (ΔS° >0) in the system. Thus, LDH has much potential as a promising material that can effectively remove anion pollutants, especiall...
Tran, HN, Nguyen, HC, Woo, SH, Nguyen, TV, Vigneswaran, S, Hosseini-Bandegharaei, A, Rinklebe, J, Kumar Sarmah, A, Ivanets, A, Dotto, GL, Bui, TT, Juang, RS & Chao, HP 2019, 'Removal of various contaminants from water by renewable lignocellulose-derived biosorbents: a comprehensive and critical review', Critical Reviews in Environmental Science and Technology, vol. 49, no. 23, pp. 2155-2219.View/Download from: Publisher's site
© 2019, © 2019 Taylor & Francis Group, LLC. Contaminants in water bodies cause potential health risks for humans and great environmental threats. Therefore, the development and exploration of low-cost, promising adsorbents to remove contaminants from water resources as a sustainable option is one focus of the scientific community. Here, we conducted a critical review regarding the application of pristine and modified/treated biosorbents derived from leaves for the removal of various contaminants. These include potentially toxic cationic and oxyanionic metal ions, radioactive metal ions, rare earth elements, organic cationic and anionic dyes, phosphate, ammonium, and fluoride from water media. Similar to lignocellulose-based biosorbents, leaf-based biosorbents exhibit a low specific surface area and total pore volume but have abundant surface functional groups, high concentrations of light metals, and a high net surface charge density. The maximum adsorption capacity of biosorbents strongly depends on the operation conditions, experiment types, and adsorbate nature. The absorption mechanism of contaminants onto biosorbents is complex; therefore, typical experiments used to identify the primary mechanism of the adsorption of contaminants onto biosorbents were thoroughly discussed. It was concluded that byproduct leaves are renewable, biodegradable, and promising biosorbents which have the potential to be used as a low-cost green alternative to commercial activated carbon for effective removal of various contaminants from the water environment in the real-scale plants.
Van, HT, Nguyen, LH, Nguyen, VD, Nguyen, XH, Nguyen, TH, Nguyen, TV, Vigneswaran, S, Rinklebe, J & Tran, HN 2019, 'Characteristics and mechanisms of cadmium adsorption onto biogenic aragonite shells-derived biosorbent: Batch and column studies.', Journal of Environmental Management, vol. 241, pp. 535-548.View/Download from: Publisher's site
Calcium carbonate (CaCO3)-enriched biomaterial derived from freshwater mussel shells (FMS) was used as a non-porous biosorbent to explore the characteristics and mechanisms of cadmium adsorption in aqueous solution. The adsorption mechanism was proposed by comparing the FMS properties before and after adsorption alongside various adsorption studies. The FMS biosorbent was characterized using nitrogen adsorption/desorption isotherm, X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, Fourier-transform infrared spectroscopy, and point of zero charge. The results of batch experiments indicated that FMS possessed an excellent affinity to Cd(II) ions within solutions pH higher than 4.0. An increase in ionic strength resulted in a significant decrease in the amount of Cd(II) adsorbed onto FMS. Kinetic study demonstrated that the adsorption process quickly reached equilibrium at approximately 60 min. The FMS biosorbent exhibited the Langmuir maximum adsorption capacity as follows: 18.2 mg/g at 10 °C < 26.0 mg/g at 30 °C < 28.6 mg/g at 50 °C. The Cd(II) adsorption process was irreversible, spontaneous (-ΔG°), endothermic (+ΔH°), and more random (+ΔS°). Selective order (mmol/g) of metal cations followed as Pb2+ > Cd2+ > Cu2+ > Cr3+ > Zn2+. For column experiments, the highest Thomas adsorption capacity (7.86 mg/g) was achieved at a flow rate (9 mL/min), initial Cd(II) concentration (10 mg/L), and bed height (5 cm). The Cd(II) removal by FMS was regarded as non-activated chemisorption that occurred very rapidly (even at a low temperature) with a low magnitude of activation energy. Primary adsorption mechanism was surface precipitation. Cadmium precipitated in the primary (Cd,Ca)CO3 form with a calcite-type structure on the FMS surface. A crust of rhombohedral crystals on the substrate was observed by SEM. Freshwater mussel shells have the potential as a renewable adsorbent to remove cadmium from water.
Nguyen, TC, Loganathan, P, Nguyen, TV, Kandasamy, J, Naidu, R & Vigneswaran, S 2018, 'Adsorptive removal of five heavy metals from water using blast furnace slag and fly ash.', Environmental science and pollution research international, vol. 25, no. 21, pp. 20430-20438.View/Download from: Publisher's site
Heavy metals can be serious pollutants of natural water bodies causing health risks to humans and aquatic organisms. The purpose of this study was to investigate the removal of five heavy metals from water by adsorption onto an iron industry blast furnace slag waste (point of zero charge (PZC) pH 6.0; main constituents, Ca and Fe) and a coal industry fly ash waste (PZC 3.0; main constituents, Si and Al). Batch study revealed that rising pH increased the adsorption of all metals with an abrupt increase at pH 4.0-7.0. The Langmuir adsorption maximum for fly ash at pH 6.5 was 3.4-5.1 mg/g with the adsorption capacity for the metals being in the order Pb > Cu > Cd, Zn, Cr. The corresponding values for furnace slag were 4.3 to 5.2 mg/g, and the order of adsorption capacities was Pb, Cu, Cd > Cr > Zn. Fixed-bed column study on furnace slag/sand mixture (1:1 w/w) revealed that the adsorption capacities were generally less in the mixed metal system (1.1-2.1 mg/g) than in the single metal system (3.4-3.5 mg/g). The data for both systems fitted well to the Thomas model, with the adsorption capacity being the highest for Pb and Cu in the single metal system and Pb and Cd in the mixed metal system. Our study showed that fly ash and blast furnace slag are effective low-cost adsorbents for the simultaneous removal of Pb, Cu, Cd, Cr and Zn from water.
To, VHP, Nguyen, TV, Vigneswaran, S, Bustamante, H, Higgins, M & Van Rys, D 2018, 'Novel methodologies for determining a suitable polymer for effective sludge dewatering', Journal of Environmental Chemical Engineering, vol. 6, no. 4, pp. 4206-4214.View/Download from: Publisher's site
© 2018 Elsevier Ltd. All rights reserved. Understanding the interactions between sludge particles and polymers during sludge dewatering is necessary to: firstly, maximize dewatered cake solids content; and secondly, minimize polymer demand. In this study, two scientific methodologies, namely the 'y-intercept' concept and Higgins modified centrifugal technique (Higgins MCT) were used to identify the optimum polymer demand and type for effective conditioning and dewatering. Results from the 'y-intercept' concept show that a large amount of polymer required during conditioning of anaerobically digested sludge (ADS) is mainly due to neutralization of soluble biopolymers. In contrast, conditioning of aerobically digested sludge (AEDS) and waste activated sludge (WAS) is mostly controlled by a polymer bridging mechanism. The results indicated that, in order to achieve maximum dewatering performance with minimum conditioning polymer requirement, high charge density polymers are suitable for ADS while branched (or cross-linked) polymers can be used for AEDS and WAS. The new lab-scale technique, Higgins MCT, was successfully implemented for measuring cake solids content achievable by centrifuge and determining the optimum polymer demand (OPD). The Higgins MCT also helped to understand the relationship between digestion, conditioning and dewatering.
Tran, HN, Lee, C-K, Nguyen, TV & Chao, H-P 2018, 'Saccharide-derived microporous spherical biochar prepared from hydrothermal carbonization and different pyrolysis temperatures: synthesis, characterization, and application in water treatment.', Environmental Technology, vol. 39, no. 21, pp. 2747-2760.View/Download from: Publisher's site
Three saccharides (glucose, sucrose, and xylose) were used as pure precursors for synthesizing spherical biochars (GB, SB, and XB), respectively. The two-stage synthesis process comprised: (1) the hydrothermal carbonization of saccharides to produce spherical hydrochar' and (2) pyrolysis of the hydrochar at different temperatures from 300°C to 1200°C. The results demonstrated that the pyrolysis temperatures insignificantly affected the spherical morphology and surface chemistry of biochar. The biochar' isoelectric point ranged from 2.64 to 3.90 (abundant oxygen-containing functionalities). The Brunauer-Emmett-Teller (BET)-specific surface areas (SBET) and total pore volumes (Vtotal) of biochar increased with the increasing pyrolysis temperatures. The highest SBET and Vtotal were obtained at a pyrolysis temperature of 900°C for GB (775 m2/g and 0.392 cm3/g), 500°C for SB (410 m2/g and 0.212 cm3/g), and 600°C for XB (426 m2/g and 0.225 cm3/g), respectively. The spherical biochar was a microporous material with approximately 71-98% micropore volume. X-ray diffraction results indicated that the biochar' structure was predominantly amorphous. The spherical biochar possessed the graphite structure when the pyrolysis temperature was higher than 600°C. The adsorption capacity of GB depended strongly on the pyrolysis temperature. The maximum Langmuir adsorption capacities ([Formula: see text]) of 900GB exhibited the following selective order: phenol (2.332 mmol/g) > Pb2+ (1.052 mmol/g) > Cu2+ (0.825 mmol/g) > methylene green 5 (0.426 mmol/g) > acid red 1 (0.076 mmol/g). This study provides a simple method to prepare spherical biochar - a new and potential adsorbent for adsorbing heavy metals and aromatic contaminants.
Van, HT, Nguyen, TMP, Thao, VT, Vu, XH, Nguyen, TV & Nguyen, LH 2018, 'Applying Activated Carbon Derived from Coconut Shell Loaded by Silver Nanoparticles to Remove Methylene Blue in Aqueous Solution', Water, Air, and Soil Pollution, vol. 229, no. 12.View/Download from: Publisher's site
© 2018, Springer Nature Switzerland AG. This study developed a new adsorbent, specifically activated carbon-loaded silver nanoparticles (AgNPs-AC) by coating the silver nanoparticles (AgNPs) onto activated carbon (AC). The obtained AgNPs-AC were characterized by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET). The ability of AgNPs-AC to remove methylene blue (MB) was evaluated using different experimental factors, these being pH solution, contact time, adsorbent dose, and initial MB concentration. Results indicated that the highest adsorption capacity of MB onto AgNPs-AC was obtained when the AC was loaded onto AgNPs at the impregnation ratio of 0.5% w/w for AC and AgNPs. The best conditions in which AgNPs-AC could remove MB were as follows: pH 10, contact time lasting 120 min, and adsorbent dose being 250 mg/25 mL solution. In this scenario, the maximum adsorption capacity of MB onto AgNPs-AC was 172.22 mg/g. The adsorption isothermal equilibrium was well described by the Langmuir, Freundlich and Sips models. The Sips equations had the highest correlation coefficient value (R2 = 0.935). The pseudo-first-order and pseudo-second-order kinetic models agree well with the dynamic behavior of the adsorption of dye MB on AgNPs-AC.
Vu, TM, Trinh, VT, Doan, DP, Van, HT, Nguyen, TV, Vigneswaran, S & Ngo, HH 2017, 'Removing ammonium from water using modified corncob-biochar', Science of the Total Environment, vol. 579, pp. 612-619.View/Download from: Publisher's site
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
Tran, HN, You, SJ, Nguyen, TV & Chao, HP 2017, 'Insight into the adsorption mechanism of cationic dye onto biosorbents derived from agricultural wastes', Chemical Engineering Communications, vol. 204, no. 9, pp. 1020-1036.View/Download from: Publisher's site
© 2017 Taylor & Francis. This study investigated the phenomenon and mechanism of adsorption of methylene green 5 (MG5) on three pristine biosorbents: golden shower pod (GS), coconut shell (CC), and orange peel (OP). The results showed that the biosorbents possessed low specific surface areas, but abundant functional groups. Adsorption was strongly affected by the solution’s pH and ionic strength. As revealed in the kinetic study, equilibrium was rapidly established, requiring low activation energies; a removal rate of 30%–87% was achieved within 1 min. The maximum Langmuir adsorption capacities at 30°C exhibited the following order: GS (106 mg/g) > OP (92 mg/g) > CC (59 mg/g). Thermodynamic experiments suggested that the adsorption occurred spontaneously and exothermically The primary adsorption mechanisms involved electrostatic attraction, hydrogen bonding formations, and n-π interaction. Thermogravimetric analysis (TGA) revealed that three biopolymer components (i.e., hemicellulose, cellulose, and lignin) played controlling roles in the adsorption process. Thus, these three agricultural residues can be considered potential low-cost adsorbents for efficient dye adsorption applications.
To, VHP, Nguyen, TV, 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.View/Download from: Publisher's site
© 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 8–10 kg polymer/dry ton. The commonly used capillary suction time parameter to evaluate the solid–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 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.
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.
Jeong, S, Tien, VN, 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.View/Download from: Publisher's site
Kalaruban, M, Loganathan, P, Shim, WG, Kandasamy, J, Naidu, G, Tien, VN & 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.View/Download from: Publisher's site
Nguyen, AH, Ngo, HH, Guo, WS, Pham, TQ, Li, FM, Nguyen, TV & Bui, XT 2015, 'Adsorption of phosphate from aqueous solutions and sewage using zirconium loaded okara (ZLO): Fixed-bed column study', SCIENCE OF THE TOTAL ENVIRONMENT, vol. 523, pp. 40-49.View/Download from: Publisher's site
Nguyen, TC, Loganathan, P, Nguyen, TV, Pham, TTN, Kandasamy, J, Wu, M, Naidu, R & Vigneswaran, S 2015, 'Trace elements in road-deposited and waterbed sediments in Kogarah Bay, Sydney: enrichment, sources and fractionation', Soil Research, vol. 53, no. 4, pp. 401-411.View/Download from: Publisher's site
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.
Shanmuganathan, S, Johir, MAH, Tien, VN, 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.View/Download from: Publisher's site
Shanmuganathan, S, Nguyen, TV, 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.View/Download from: Publisher's site
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)–GAC hybrid system that removed natural and synthetic organics prior to its discharge into the environment. The MF–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–organic carbon detection (LC–OCD), Fluorescence Excitation-Emission matrix (F-EEM), and Liquid chromatography with tandem mass spectroscopy (LC–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–GAC hybrid system
Shanmuganathan, S, Vigneswaran, S, Nguyen, TV, 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.View/Download from: Publisher's site
Thankappan, R, Nguyen, TV, Srinivasan, SV, 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.View/Download from: Publisher's site
Thuy, CN, Loganathan, P, Tien, VN, 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.View/Download from: Publisher's site
Rahman, MA, Hogan, B, Duncan, E, Doyle, C, Rahman, MM, Nguyen, TV, Lim, RP, 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.View/Download from: Publisher's site
Hossain, MD, Ngo, H, Guo, W, Nghiem, LD, Hai, FI, Vigneswaran, S & Nguyen, V 2014, 'Competitive adsorption of metals on cabbage waste from multi-metal solutions', Bioresource Technology, vol. 160, pp. 79-88.View/Download from: Publisher's site
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.
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.View/Download from: Publisher's site
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.
Nguyen, T, Ngo, H, Guo, W, Nguyen, V, Zhang, J, Liang, S, Chen, S & Nguyen, NC 2014, 'A comparative study on different metal loaded soybean milk by-product 'okara' for biosorption of phosphorus from aqueous solution', Bioresource Technology, vol. 169, pp. 291-298.View/Download from: Publisher's site
Cationization of agricultural by-products using metal salts is widely used to activate their phosphorous capture ability. This study developed three kinds ofnew metal loaded soybean milk by-product `okara for phosphorus biosorption. A comparative study among these biosorbents was carried out with respect to their performances in terms of affinity, stability and reusability. Zirconium loaded okara (ZLO) was found to have the highest affinity towards PO43- anions (47.88 mg/g), followed by iron/zirconium loaded okara IZLO (40.96 mg/g) and iron loaded okara ILO (16.39 mg/g). ZLO was successfully desorbed with 0.2 M NaOH and activated with 0.1 HCl prior to the next cycle. After five consecutive cycles, the efficiency of both adsorption and desorption of ZLO remained about 85% whilst no Zr(IV) leakage was observed. Conversely, IZLO and ILO suffered from vitalshortcomingssuch ashigh metal release and/or sharp reduction in PO43- sequestering capability after multi operation cycles.
Tien, VN, Loganathan, P, Vigneswaran, S, Krupanidhi, S, Thi, TNP & Huu-Hao, N 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.View/Download from: Publisher's site
Nguyen, T, Loganathan, L, Nguyen, V, Vigneswaran, S, Kandasamy, JK, 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.View/Download from: Publisher's site
Nur, T, Johir, MAH, 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.View/Download from: Publisher's site
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.
Shanmuganathan, S, Nguyen, V, Shim, W, Kandasamy, JK & 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.View/Download from: Publisher's site
Shanmuganathan, S, Tien, VN, Shim, WG, 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.View/Download from: Publisher's site
Tien, VN, Jeong, S, Thi, TNP, Kandasamy, J & Vigneswaran, S 2014, 'Effect of granular activated carbon filter on the subsequent flocculation in seawater treatment', DESALINATION, vol. 354, pp. 9-16.View/Download from: Publisher's site
Nguyen, T, Ngo, H, Guo, W, Zhang, J, Liang, S, Yue, Q, Li, Q & Nguyen, V 2013, 'Applicability of agricultural waste and by-products for adsorptive removal of heavy metals from wastewater', Bioresource Technology, vol. 148, no. 1, pp. 574-585.View/Download from: Publisher's site
This critical review discusses the potential use of agricultural waste based biosorbents (AWBs) for sequestering heavy metals in terms of their adsorption capacities, binding mechanisms, operating factors and pretreatment methods. The literature survey indicates that AWBs have shown equal or even greater adsorption capacities compared to conventional adsorbents. Thanks to modern molecular biotechnologies, the roles of functional groups in biosorption process are better understood. Of process factors, pH appears to be the most influential. In most cases, chemical pretreatments bring about an obvious improvement in metal uptake capacity. However, there are still several gaps, which require further investigation, such as (i) searching for novel, multi-function AWBs, (ii) developing cost-effective modification methods and (iii) assessing AWBs under multi-metal and real wastewater systems. Once these challenges are settled, the replacement of traditional adsorbents by AWBs in decontaminating heavy metals from wastewater can be expected in the future.
Jeong, S, Kim, S, Kim, CM, Vigneswaran, S, Nguyen, V, Shon, H, Kandasamy, JK & Kim, IS 2013, 'A detailed organic matter characterization of pretreated seawater using low-pressure microfiltration hybrid systems', Journal Of Membrane Science, vol. 428, pp. 290-300.View/Download from: Publisher's site
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 chromatographyâmass 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, 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.View/Download from: Publisher's site
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.
Jeong, S, Kim, S, Kim, LH, Shin, MS, Vigneswaran, S, Nguyen, V & Kim, IS 2013, 'Foulant analysis of a reverse osmosis membrane used pretreated seawater', Journal Of Membrane Science, vol. 428, pp. 434-444.View/Download from: Publisher's site
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 excitationâemission 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.
Hossain, A, Ngo, H, Guo, W & Nguyen, V 2012, 'Biosorption of Cu(II) From Water by Banana Peel Based Biosorbent: Experiments and Models of Adsorption and Desorption', Journal of Water Sustainability, vol. 2, no. 1, pp. 87-104.
Banana peel, a discarded agricultural waste was used to produce bioadsorbent through easy and environmental friendly processes. This banana peel based biosorbent was evaluated for adsorptive removal of copper from water and its desorption capability. The characterisation results showed this biosorbent had very high specific surface area, potential binding sites and functional groups. The optimal conditions for biosorption were found at pH 6.5, biosorbent size of less than 75Î¼, dose of 0.5g/100ml and 1-hour contact time. Thermodynamic analysis also indicated that its adsorption was spontaneous. Significant desorption of copper (94%) was obtained when using 0.1N H2SO4. Both adsorption and desorption equilibrium data were well described by Langmuir, SIPS and Koble-Corrigan models whilst kinetics data by pseudo-first order, Elovich and Intraparticle diffusion models. Modelsâ parameters were optimised by MATLABâs non-linear modelling. All models had good fitness with the experimental data from high R2 (0.970-1.00), low non-linear errors - RMSE (0.004-10.00) and low 2 (0.0004-10.00). The maximum adsorption and desorption capacities were 20.37 and 32.40 mg/g, respectively. The adsorption processes were controlled by chemisorption. Both adsorption and desorption processes could be described by the pseudo-first order kinetic. The potential applicability of banana peel based bioadsorbent could be further examined in a large-scale.
Hossain, M, Ngo, H, Guo, W & Nguyen, V 2012, 'Palm Oil Fruit Shells As Biosorbent For Copper Removal From Water And Wastewater: Experiments And Sorption Models', Bioresource Technology, vol. 113, pp. 97-101.View/Download from: Publisher's site
Palm oil fruit shells were evaluated as a new bioadsorbent to eliminate toxic copper from water and wastewater. Without any chemical treatment, palm oil fruit shells were washed, dried and grounded into powder (<75 lm) for use in the experiments. Characterization showed mesopore based bioadsorbent was prepared from palm oil fruit shells. The results indicate that the highest Cu removal efficiency was found in an aqueous solution with pH of 6.5. The equilibrium sorption capacity of copper was significantly high (between 28 and 60 mg/g) at room temperature. Nonlinear regression analyses for isotherm models revealed that three-parameter isotherms had a better fit to the experimental data (R2 > 0.994) than that of two-parameter isotherms. The copper sorption system was heterogeneous as the values of exponents were lying between 0 and 1. The highly correlated pseudo-second-order kinetics model (R2 > 0.998) ascertained the applicability of copper removal by palm oil fruit shells.
Banana peel, a fruit waste were used to produce bioadsorbent through environment friendly process. It were cut, washed, dried, grounded into powder and used for copper removal. Copper adsorption onto banana peel was depended upon the controlling parameters such as particle size, doses, pH, contact time, agitation speed and temperature. Slightly acidic water (pH = 6) was found to be suitable for copper removal. Equilibrium data were well fitted (R2 = 0.998) with the Langmuir and Freundlich isotherms. The monolayer adsorption capacity was 27.78 mg/g. The calculated RL and `n values has proved the favorability of copper adsorption onto banana peel. Copper adsorption was followed the second order kinetic properly rather than other models. The equilibrium adsorption capacity was 1.439, 8.849, 18.182, 31.250 and 71.429 mg/g when initial copper concentrations were 10, 50, 100, 200, and 400 mg/l respectively. Solvent 0.1N Sulphuric acid showed higher desorption of copper (94%) and adsorption-desorption process can be continued till seven cycles efficiently.
Phosphorous plays an essential role in the development of living organisms. Nevertheless, phosphorous pollution, known as the eutrophication, is regarded as one of main causes of water quality deterioration. Hence, the decontamination of phosphorous from aqueous solutions is of importance for eutrophication control and phosphorous recovery. This review paper investigates the potential use of agricultural by-products (ABPs) as biosorbents in remediation of phosphorous contaminated waters. It was found that the modified ABPs exhibit equivalent or higher sorption capacity of phosphorous compared to conventional adsorbents. The efficient removal of phosphorous by ABPs requires some chemical modifications. The application of ABPs is highly recommended because of their significant advantages, including the abundant availability, low cost, high efficiency and without detrimental impacts on the environment. As adsorptive removal of phosphorous by ABPs is a relatively new process, there are still many aspects for future research, such as development of novel and cost-effective modification techniques, modeling for process optimization, desorption, cost-benefit analysis etc. The improvements in these aspects are expected to make it the method of choice in the future.
Ahmad, R, Nguyen, V, Shim, WG, Vigneswaran, S, Moon, H & Kandasamy, JK 2012, 'Effluent Organic Matter Removal By Purolite (R) A500PS: Experimental Performance And Mathematical Model', Separation and Purification Technology, vol. 98, pp. 46-54.View/Download from: Publisher's site
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%).
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.View/Download from: Publisher's site
Deep bed filtration has traditionally been used as a pretreatment in seawater desalination. The performance of contact flocculationâfiltration (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 (0.5â3.0mg Fe3+/L) and rapid mixing times (1.7â14.4 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).
Jeong, S, Choi, Y, Nguyen, V, Vigneswaran, S & Hwang, TM 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.View/Download from: Publisher's site
Three different submerged membrane hybrid systems (SMHSs) namely submerged membrane coagulation hybrid system (SMCHS), submerged membrane adsorption hybrid system (SMAHS), and submerged membrane coagulationâadsorption 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.
Jeong, S, Kim, L, Kim, S, Nguyen, V, Vigneswaran, S & Kim, IS 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.View/Download from: Publisher's site
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
Nguyen, V, Zhang, R, Vigneswaran, S, Ngo, H, Kandasamy, JK & Mathes, P 2011, 'Removal of organic matter from effluents by Magnetic Ion Exchange (MIEX)', Desalination, vol. 276, no. 1-3, pp. 96-102.View/Download from: Publisher's site
Magnetic Ion Exchange Resin (MIEXÂ®) 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 MIEXÂ® 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 MIEXÂ® contactor effectively removed organic matter from synthetic biologically treated sewage effluent with more than 60% DOC removal even after 172 bed volumes. The regenerated MIEXÂ® resin did not display any significant reduction in its ability to remove organic matter.
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.View/Download from: Publisher's site
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.
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-Î´) and ferric chloride as flocculants', Desalination, vol. 283, pp. 106-111.View/Download from: Publisher's site
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-Î´) and ferric chloride (FeCl3). The experimental results were analysed in terms of organic removal efficiency and critical flux. Both PFSi-Î´ and FeCl3 were found to be suitable as pretreatment because of their capacity in removing organic compounds. The results show that PFSi-Î´ 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-Î´ at a dose of 1.2 mg Fe3+/L and FeCl3 at 3 mg Fe3+/L were used, respectively. It was observed that PFSi-Î´ (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.View/Download from: Publisher's site
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 â 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/m2Â·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.View/Download from: Publisher's site
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 Î¼m). 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%.
Nguyen, V, Vigneswaran, S, Ngo, H & Kandasamy, JK 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.View/Download from: Publisher's site
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.
Nguyen, V, Nguyen, T, Pham, TL, Vigneswaran, S, Ngo, H, Kandasamy, JK, Nguyen, H & Nguyen, TD 2009, 'Adsorption and removal of arsenic from water by iron ore mining waste', Water Science and Technology, vol. 60, no. 9, pp. 2301-2308.View/Download from: Publisher's site
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
Nguyen, V, Rahman, A, Vigneswaran, S, Ngo, H, Kandasamy, JK, Nguyen, TD, Do, AT & Nguyen, KT 2009, 'Arsenic removal by iron oxide coated sponge: treatment and waste management', Water Science and Technology, vol. 60, no. 6, pp. 1489-1495.View/Download from: Publisher's site
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.
Nguyen, V, Vigneswaran, S, Ngo, H, Shon, H & Kandasamy, JK 2009, 'Arsenic removal by a membrane hybrid filtration system', Desalination, vol. 236, no. 1-3, pp. 363-369.View/Download from: Publisher's site
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.
Nguyen, V, Vigneswaran, S, Ngo, H, Kandasamy, JK & Choi, H 2008, 'Arsenic removal by photo-catalysis hybrid system', Separation and Purification Technology, vol. 61, no. 1, pp. 44-50.View/Download from: Publisher's site
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.
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.
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
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.View/Download from: Publisher's site
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,
Vigneswaran, S, Nguyen, TV, Kandasamy, J, Ben Aim, R & Visvanathan, C 2012, 'Membrane processes for drinking water treatment' in Membrane Technology and Environmental Applications, ASCE Publications, pp. 140-168.View/Download from: Publisher's site
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 ...
Nguyen, TC, Colville, A, Lim, R, Rahman, MA, Nguyen, TV, Loganathan, P, Kandasamy, J, Naidu, R & Vigneswaran, S 2014, 'Toxicity assessment of road-deposited sediments in Sydney, Australia', SETAC 2014 Advancing Science for a Sustainable Environment, Society of Environmental Toxicology and Chemistry (SETAC), Adelaide, Australia.
Nguyen, TC, Loganathan, P, Nguyen, TV, Vigneswaran, S & Kandasamy, J 2014, 'Simultaneous adsorption of Cd, Cu, Cr, Pb, and Zn by an Australian iron-coated zeolite', 7th International Young Water Professional Conference, Taipei, Taiwan.
To, VHP, Nguyen, TV, Vigneswaran, S, Nghiem, L, Murthy, S, Bustamante, H & Higgins, MJ 2014, 'Modified centrifugal index and sludge characteristics in assessing sludge dewatering', 7th International Young Water Professional Conference, Taipei, Taiwan.
Nguyen, TC, Loganathan, P, Nguyen, TV, Pham, TTN, Vigneswaran, S, Kandasamy, J, Wu, M & Naidu, R 2013, 'Heavy metals in road-deposited and water sediments at Kogarah bay, Sydney: Enrichment, sources, and fractionation', IWA Conference on Metals in water – Health protection and sustainability through technical innovation, Shanghai, China.
Nguyen, V, Tran, TT, Pham, TL, Vigneswaran, S, Ngo, H, Nguyen, H & Nguyen, DT 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.
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 1,000Î¼g/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.
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.
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.