Van, HT, Lim, S, Han, DS, Pathak, N, Akther, N, Phuntsho, S, Park, H & Shon, HK 2019, 'Efficient fouling control using outer-selective hollow fiber thin-film composite membranes for osmotic membrane bioreactor applications', BIORESOURCE TECHNOLOGY, vol. 282, pp. 9-17.View/Download from: UTS OPUS or Publisher's site
Chekli, L, Pathak, N, Kim, Y, Phuntsho, S, Li, S, Ghaffour, N, Leiknes, T & Shon, HK 2018, 'Combining high performance fertiliser with surfactants to reduce the reverse solute flux in the fertiliser drawn forward osmosis process.', Journal of environmental management, vol. 226, pp. 217-225.View/Download from: UTS OPUS or Publisher's site
Solutions to mitigate the reverse diffusion of solutes are critical to the successful commercialisation of the fertiliser drawn forward osmosis process. In this study, we proposed to combine a high performance fertiliser (i.e., ammonium sulfate or SOA) with surfactants as additives as an approach to reduce the reverse diffusion of ammonium ions. Results showed that combining SOA with both anionic and non-ionic surfactants can help in reducing the reverse salt diffusion by up to 67%. We hypothesised that, hydrophobic interactions between the surfactant tails and the membrane surface likely constricted membrane pores resulting in increased rejection of ions with large hydrated radii such as SO42-. By electroneutrality, the rejection of the counter ions (i.e., NH4+) also therefore subsequently improved. Anionic surfactant was found to further decrease the reverse salt diffusion due to electrostatic repulsions between the surfactant negatively-charged heads and SO42-. However, when the feed solution contains cations with small hydrated radii (e.g., Na+); it was found that NH4+ ions can be substituted in the DS to maintain its electroneutrality and thus the diffusion of NH4+ to the feed solution was increased.
Fortunato, L, Pathak, N, Ur Rehman, Z, Shon, H & Leiknes, TO 2018, 'Real-time monitoring of membrane fouling development during early stages of activated sludge membrane bioreactor operation', Process Safety and Environmental Protection, vol. 120, pp. 313-320.View/Download from: UTS OPUS or Publisher's site
© 2018 Institution of Chemical Engineers Non-invasive analysis and a final destructive analysis were employed to study the fouling formation during the initial days of AS-MBR operation. The fouling layer development was quantified in-situ non-invasively with Optical Coherence Tomography (OCT). The increase in biomass thickness was related to the transmembrane pressure (TMP) and to the increase in concentration of soluble microbial products (SMP) in the reactor The OCT non-destructive analysis allowed normalizing the final autopsy values for the amount of biomass deposited on the membrane. After 8 days of operation, the cake layer presented a biomass activity of 400 pg/mm3 of intra-ATP and EPS concentration of 9.8 mg/ mm3. The microbial community analysis of sludge and biofouling on the membrane surface revealed the abundance of Proteobacteria.
Pathak, N, Fortunato, L, Li, S, Chekli, L, Phuntsho, S, Ghaffour, N, Leiknes, T & Shon, HK 2018, 'Evaluating the effect of different draw solutes in a baffled osmotic membrane bioreactor-microfiltration using optical coherence tomography with real wastewater.', Bioresource technology, vol. 263, pp. 306-316.View/Download from: UTS OPUS or Publisher's site
This study investigated the performance of an integrated osmotic and microfiltration membrane bioreactor for real sewage employing baffles in the reactor. To study the biofouling development on forward osmosis membranes optical coherence tomography (OCT) technique was employed. On-line monitoring of biofilm growth on a flat sheet cellulose triacetate forward osmosis (CTA-FO) membrane was conducted for 21 days. Further, the process performance was evaluated in terms of water flux, organic and nutrient removal, microbial activity in terms of soluble microbial products (SMP) and extracellular polymeric substance (EPS), and floc size. The measured biofouling layer thickness was in the order sodium chloride (NaCl) > ammonium sulfate (SOA) > potassium dihydrogen phosphate (KH2PO4). Very high organic removal (96.9 ± 0.8%) and reasonably good nutrient removal efficiency (85.2 ± 1.6% TN) was achieved. The sludge characteristics and biofouling layer thickness suggest that less EPS and higher floc size were the governing factors for less fouling.
Pathak, N, Li, S, Kim, Y, Chekli, L, Phuntsho, S, Jang, A, Ghaffour, N, Leiknes, T & Shon, HK 2018, 'Assessing the removal of organic micropollutants by a novel baffled osmotic membrane bioreactor-microfiltration hybrid system.', Bioresource technology, vol. 262, pp. 98-106.View/Download from: UTS OPUS or Publisher's site
A novel approach was employed to study removal of organic micropollutants (OMPs) in a baffled osmotic membrane bioreactor-microfiltration (OMBR-MF) hybrid system under oxicanoxic conditions. The performance of OMBR-MF system was examined employing three different draw solutes (DS), and three model OMPs. The highest forward osmosis (FO) membrane rejection was attained with atenolol (100%) due to its higher molar mass and positive charge. With inorganic DS caffeine (94-100%) revealed highest removal followed by atenolol (89-96%) and atrazine (16-40%) respectively. All three OMPs exhibited higher removal with organic DS as compared to inorganic DS. Significant anoxic removal was observed for atrazine under very different redox conditions with extended anoxic cycle time. This can be linked with possible development of different microbial consortia responsible for diverse enzymes secretion. Overall, the OMBR-MF process showed effective removal of total organic carbon (98%) and nutrients (phosphate 97% and total nitrogen 85%), respectively.
Volpin, F, Gonzales, RR, Lim, S, Pathak, N, Phuntsho, S & Shon, HK 2018, 'GreenPRO: A novel fertiliser-driven osmotic power generation process for fertigation', DESALINATION, vol. 447, pp. 158-166.View/Download from: UTS OPUS or Publisher's site
Pathak, N, Chekli, L, Wang, J, Kim, Y, Phuntsho, S, Li, S, Ghaffour, N, Leiknes, T & Shon, H 2017, 'Performance of a novel baffled osmotic membrane bioreactor-microfiltration hybrid system under continuous operation for simultaneous nutrient removal and mitigation of brine discharge.', Bioresource Technology, vol. 240, pp. 50-58.View/Download from: UTS OPUS or Publisher's site
The present study investigated the performance of an integrated osmotic and microfiltration membrane bioreactor system for wastewater treatment employing baffles in the reactor. Thus, this reactor design enables both aerobic and anoxic processes in an attempt to reduce the process footprint and energy costs associated with continuous aeration. The process performance was evaluated in terms of water flux, salinity build up in the bioreactor, organic and nutrient removal and microbial activity using synthetic reverse osmosis (RO) brine as draw solution (DS). The incorporation of MF membrane was effective in maintaining a reasonable salinity level (612-1434mg/L) in the reactor which resulted in a much lower flux decline (i.e. 11.48-6.98LMH) as compared to previous studies. The stable operation of the osmotic membrane bioreactor-forward osmosis (OMBR-FO) process resulted in an effective removal of both organic matter (97.84%) and nutrient (phosphate 87.36% and total nitrogen 94.28%), respectively.
Wang, J, Pathak, N, Chekli, L, Phuntsho, S, Kim, Y, Li, D & Shon, HK 2017, 'Performance of a novel fertilizer-drawn forward osmosis aerobic membrane bioreactor (FDFO-MBR): Mitigating salinity build-up by integrating microfiltration', Water, vol. 9, no. 1, pp. 1-13.View/Download from: UTS OPUS or Publisher's site
© 2017 by the authors. In this paper, three different fertilizer draw solutions were tested in a novel forward osmosis-microfiltration aerobic membrane bioreactor (MF-FDFO-MBR) hybrid system and their performance were evaluated in terms of water flux and reverse salt diffusion. Results were also compared with a standard solution. Results showed that ammonium sulfate is the most suitable fertilizer for this hybrid system since it has a relatively high water flux (6.85 LMH) with a comparatively low reverse salt flux (3.02 gMH). The performance of the process was also studied by investigating different process parameters: draw solution concentration, FO draw solution flow rate and MF imposed flux. It was found that the optimal conditions for this hybrid system were: draw solution concentration of 1 M, FO draw solution flow rate of 200 mL/min and MF imposed flux of 10 LMH. The salt accumulation increased from 834 to 5400 μS/cm during the first four weeks but after integrating MF, the salinity dropped significantly from 5400 to 1100 μS/cm suggesting that MF is efficient in mitigating the salinity build up inside the reactor. This study demonstrated that the integration of the MF membrane could effectively control the salinity and enhance the stable FO flux in the OMBR.