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Now showing items 1 - 16 of 37

  • Plant Traits for Phytoremediation in the Tropics

    Chen, Xiangting Cleo   Huang, Liling   Chang, Tze Hsien Agnes   Ong, Bee Lian   Ong, Say Leong   Hu, Jiangyong  

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  • Electrodialysis reversal for industrial reverse osmosis brine treatment

    Zhao, Dandan   Lee, Lai Yoke   Ong, Say Leong   Chowdhury, Prannoy   Siah, Keng Boon   Ng, How Yong  

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  • Brine pre-treatment technologies for zero liquid discharge systems

    Semblante, Galilee Uy   Lee, Jonathan Zhiqiang   Lee, Lai Yoke   Ong, Say Leong   Ng, How Yong  

    The management of brine produced by the reverse osmosis process is challenging due to its high salt and organic content. Limitations in brine disposal options sometimes necessitate the use of zero liquid discharge (ZLD) approach. ZLD systems may include a membrane process which is used to recover water and to further concentrate brine followed by thermal treatment. In such systems, a high-water recovery rate is difficult to achieve due to the early onset of membrane scaling and fouling. Brine pre-treatment is therefore necessary to protect the membrane and facilitate ZLD. Literature shows that the most common brine pre-treatment process, chemical precipitation, is generally costly because of high chemical consumption and hazardous sludge production. Moreover, its performance may be hindered by the temporal fluctuations in brine chemistry and the occurrence of residual antiscalants in the brine. A critical evaluation of alternative pre-treatment options was performed. It was found that electrocoagulation and nanofiltration processes have promising performance in terms of hardness and organic removals. Meanwhile, coagulation and adsorption processes show potential for organic removal. Further studies should be performed on process optimization and cost analysis to determine the feasibility of applying these technologies in ZLD systems.
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  • Optimization of resource and water recovery from urine

    Lefebvre, Olivier   Hu, Jiangyong   Ong, Say Leong   Ng, How Yong  

    This study deals with the feasibility and practicality to recover water and nutrients from fresh urine by means of evaporation/ condensation. The evaporation process generated two distinct fractions: a condensate and a concentrate. The optimal percentage of evaporation (in volume) was found to be 80%, resulting in optimal condensate quality. Higher percentages of evaporation resulted in a deterioration of water quality, as urea decomposed into ammonia, followed by volatilization of the ammonia which ended up in the condensate. Following evaporation, struvite was recovered from the concentrate at an optimal Mg/N ratio of 1/1. The condensate was purified by filtration into two layers of soil and sand, followed by zeolites. Complete removal of N-NH3 and 91% removal of chemical oxygen demand (COD) could be achieved throughout this process. Finally, the condensate was disinfected by sodium hypochlorite, achieving over 6-log inactivation of MS2 bacteriophage at a dose of 1,200 mg min/L. In conclusion, this study shows that there exist some potential benefits to the production of high-quality water and fertilizer from urine. The value of struvite recovered from the concentrate was found to be equivalent to that of the water from the condensate, showing that both streams deserve equal attention.
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  • Active removal of ibuprofen by Money plant enhanced by ferrous ions

    Chehrenegar, Behdad   Hu, Jiangyong   Ong, Say Leong  

    In this study, the removal of ibuprofen (IBP), a pharmaceutical compound, from aqueous media by Money plant (Epipremnum aureum) was investigated. The effect of ferrous iron (Fe2+) on enhancing the IBP removal rate was also analyzed. The first-order removal rate constants showed higher values for lower IBP initial concentrations in the range of 0.20-0.28 d(-1) for an initial concentration of 125 mu g L-1 to 0.03-0.13 d(-1) for an initial concentration of 1000 mu g L-1. Introducing ferrous iron to the aqueous media enhanced the first-order removal rate constant up to 6.5 times in a 3 d time period. Along with the removal of IBP from the media, the endogenous concentration of H2O2 also decreased presumably by the production of hydroxyl radical (center dot OH). Reduction in the endogenous H2O2 concentration was recorded to be 38% and 98% in the absence and presence of Fe2+ respectively in the first day and the H2O2 level remained considerably low until day 7 which then gradually increased slightly. Simultaneous reduction of IBP and endogenous H2O2 concentration could be due to the reaction of IBP with center dot OH and presumably center dot OH production itself accelerated via Fenton reaction. In addition, presence of sodium bicarbonate (NaHCO3) as center dot OH scavenger in the system showed reduction of first-order removal rate constant from 1.30 d(-1) to 0.07 d(-1) which could be a possible evidence of biological advanced oxidation process which is believed to play an important role in phytoremediation.(c) 2015 Elsevier Ltd. All rights reserved.
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  • Application of proteomics in environmental science

    Chu, Xiaona   Hu, Jiangyong   Ong, Say Leong  

    Proteomics involves the separation of proteins, identification of the amino acid sequence of the interested or target proteins, study of the function of the proteins, modification, structure and ultimate assignments to functional pathways in the cell. The proteomic investigations have contributed greatly to human diseases studies, new drugs discovery researches, and environmental science in recent years. This article provides a review on the development of the main proteomic technologies, including both the gel based and non-gel based technologies, and their applications in environmental science. Proteomic technologies have been utilized in the environmental stresses studies to analyze the induction or reduction of proteins at expression level and identify the target proteins to investigate their function in response to environmental stresses, such as high or low pH, oxidation stress, and toxic chemicals. Such protein responses are also helpful to understand the mechanisms of some cellular activities and the functions of some proteins.
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  • Performance of an ultra-compact biofilm reactor treating domestic and synthetic wastewaters

    Koh, Lee Chew   Zhang, Haiyang   Thi Thai Ha Nguyen   Ong, Say Leong  

    The performance of an ultra-compact biofilm reactor (UCBR) treating domestic wastewater (DWW) collected from a local water reclamation plant; and gradually shifting to a mono-type carbon source synthetic wastewater (SWW) combined with DDW (CWW) and finally SWW; was investigated in this study. The total COD concentrations of influent DWW and CWW/SWW were 413.6 +/- 80.8 mg/L and 454.9 +/- 51.3 mg/L, respectively. The UCBR was able to achieve average total COD removal efficiencies of 70 +/- 10% and 80 +/- 4% for DWW and SWW respectively. The total COD concentrations of the effluent of DWW and CWW/SWW were 122.5 +/- 44.4 mg/L and 89.7 +/- 10.3 mg/L, respectively. These observations suggested that heterotrophs in the UCBR system were able to better assimilate and remove carbon of mono-type SWW compared to diverse carbon sources such as DWW; although the influent soluble COD concentrations of the SWW were higher than those of the DWW. However, the effluent NH4+-N concentrations for both types of wastewater were rather similar, <3.0 mg/L; although the influent NH4+-N concentrations of the DWW were 1.5 times those of the SWW.
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  • Implication of zeta potential at different salinities on boron removal by RO membranes

    Oo, Maung Htun   Ong, Say Leong  

    Boron removal by reverse osmosis (RO) membranes has been improved through raised pH and its removal mechanism was suggested as either charge repulsion or size exclusion. In the present study, boron removal by different RO membranes at different salinities was investigated along with their respective zeta potentials. While the impact of salinity on zeta potential of RO membranes was similar, its impact on boron removal by brackish water reverse osmosis (BWRO) membranes was different from that by SWC4+ and ESPAB membranes. RO membranes used in this study showed negative zeta potential value at high pH. However, at pH 9 and with higher salinity, their zeta potentials shifted to positive values. Boron removal by BWRO membranes decreased with increasing salinity at pH 9. The shift of zeta potential towards positive values at higher salinity suggested that charge repulsion mechanism became less dominant. Boron removal by ESPAB and SWC4+ decreased initially when NaCl concentration was increased towards 2000 mg/L at pH 9. However, removal increased slowly when NaCl was beyond 2000 mg/L This observation suggested that boron removal by these membranes at low salinity was partially contributed by charge repulsion mechanism. At higher salinity, size exclusion could be the dominant factor for boron removal by SWC4 and ESPAB. (C) 2010 Elsevier B.V. All rights reserved.
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  • Preparation of a New Type of Black TiO2 under a Vacuum Atmosphere for Sunlight Photocatalysis

    Katal, Reza   Salehi, Mojtaba   Farahano, Mohammad Hossein Davood Abadi   Masudy-Panah, Saeid   Ong, Say Leong   Hu, Jiangyong  

    Black TiO2 as a solar-driven photocatalyst has attracted enormous attention from scientists and engineers in water and wastewater treatment field. Most of the methods used for the preparation of black TiO2 are thermal treatment under a hydrogen atmosphere. Nevertheless, it is well known that working with hydrogen is not safe and needs special maintenance. Here, for the first time, we prepared black TiO2 by sintering P25 pellets at different temperatures (500-800 degrees C) under a vacuum atmosphere that showed the same performance with the prepared black TiO2 under a hydrogen atmosphere. The samples were characterized by X-ray diffraction, Raman spectra field emission scanning electron microscopy, transmission electron microscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, and ultraviolet-visible deep resistivity sounding techniques. The differences between the formation of oxygen vacancy density and color turning in sintered powder and pellet were also studied. The results showed that the color of the P25 powder became darker after sintering but not completely turning to black, whereas the P25 pellets completely turned black after sintering. The resultant black TiO2 was used for the photocatalytic degradation of the acetaminophen (ACE) in aqueous solution under AM 1.5G solar light illumination; it was found that the P25 pellet sintered in 500 degrees C had the highest photocatalytic performance for ACE degradation under AM 1.5G solar light illumination. The photocatalytic activity of prepared black TiO2 under vacuum and hydrogen atmospheres was also compared together; the results showed that photocatalytic activities of both samples were so close together. The existence of the oxygen vacancy after 6 months and long and short-term stability (by application for photocatalytic degradation of ACE in an aqueous solution) of the black TiO2 pellets was also studied; the results showed that the TiO2 pellets in aqueous phase had acceptable stability.
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  • RO brine treatment and recovery by biological activated carbon and capacitive deionization process

    Tao, Guihe   Viswanath, Bala   Kekre, Kiran   Lee, Lai Yoke   Ng, How Yong   Ong, Say Leong   Seah, Harry  

    The generation of brine solutions from dense membrane (reverse osmosis, RO or nanofiltration, NF) water reclamation systems has been increasing worldwide, and the lack of cost effective disposal options is becoming a critical water resources management issue. In Singapore, NEWater is the product of a multiple barrier water reclamation process from secondary treated domestic effluent using MF/UF-RO and UV technologies. The RO brine (concentrates) accounts for more than 20% of the total flow treated. To increase the water recovery and treat the RO brine, a CDI based process with BAC as pretreatment was tested. The results show that ion concentrations in CDI product were low except SiO2 when compared with RO feed water. CDI product was passed through a RO and the RO permeate was of better quality including low SiO2 as compared to NEWater quality. It could be beneficial to use a dedicated RO operated at optimum conditions with better performance to recover the water. BAC was able to achieve 15-27% TOC removal of RO brine. CDI had been tested at a water recovery ranging from 71.6 to 92.3%. CDI based RO brine treatment could improve overall water recovery of NEWater production over 90%. It was found that calcium phosphate scaling and organic fouling was the major cause of CDI pressure increase. Ozone disinfection and sodium bisulfite dosing were able to reduce CDI fouling rate. For sustainable operation of CDI organic fouling control and effective organic fouling cleaning should be further studied.
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  • Role of metal modified water treatment residual on removal of Escherichia coli from stormwater runoff

    Xu, Dong   Shi, Xueqing   Lee, Lai Yoke   Lyu, Zhiyang   Ong, Say Leong   Hu, Jiangyong  

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  • Comparison of fouling characteristics in different pore-sized submerged ceramic membrane bioreactors

    Jin, Le   Ong, Say Leong   Ng, How Yong  

    Membrane fouling, the key disadvantage that inevitably occurs continuously in the membrane bioreactor (MBR), baffles the wide-scale application of MBR. Ceramic membrane, which possesses high chemical and thermal resistance, has seldom been used in MBR to treat municipal wastewater. Four ceramic membranes with the same materials but different pore sizes, ranging from 80 to 300 nm, were studied in parallel using four lab-scale submerged MBRs (i.e., one type of ceramic membrane in one MBR). Total COD and ammonia nitrogen removal efficiencies were observed to be consistently above 94.5 and 98%, respectively, in all submerged ceramic membrane bioreactors. The experimental results showed that fouling was mainly affected by membrane's microstructure, surface roughness and pore sizes. Ceramic membrane with the roughest surface and biggest pore size (300 nm) had the highest fouling potential with respect to the TMP profile. The 80 nm membrane with a smoother surface and relatively uniform smaller pore openings experienced least membrane fouling with respect to TMP increase. The effects of the molecular weight distribution, particle size distribution and other biomass characteristics such as extracellular polymeric substances, zeta potential and capillary suction time, were also investigated in this study. Results showed that no significant differences of these attributes were observed. These observations indicate that the membrane surface properties are the dominant factors leading to different fouling potential in this study. (C) 2010 Elsevier Ltd. All rights reserved.
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  • A method to eliminate bromide interference on standard COD test for bromide-rich industrial wastewater

    Shi, Xueqing   Huang, Shujuan   Yeap, Tsuey Shan   Ong, Say Leong   Ng, How Yong  

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  • Removal of natural hormone estrone from secondary effluents using nanofiltration and reverse osmosis

    Jin, Xue   Hu, Jiangyong   Ong, Say Leong  

    The rejection of steroid hormone estrone by nanofiltration (NF) and reverse osmosis (RO) membranes in treated sewage effluent was investigated Four NF/RO membranes with different materials and interfacial characteristics were utilized To better understand hormone removal mechanisms in treated effluent, effluent organic matters (EfOM) were fractionated using column chromatographic method with resins XAD-8, AG MP-50 and IRA-96 The results indicate that the presence of EfOM in feed solution could enhance estrone rejection significantly Hydrophobic acid (HpoA) organic fraction made a crucial contribution to this "enhancement effect" Hydrophobic base (HpoB) could also improve estrone rejection while hydrophobic neutral (HpoN) and hydrophilic acid (HpoA) with low aromaticity had little effects. The increment in estrone rejection was predominantly attributed to the binding of estrone by EfOM in feed solutions, which led to an increase in molecular weight and appearance of negative charge (for the HpoA case) and thus an increased level of estrone rejection However, the improvement of estrone rejection by HpoA decreased with increasing calcium ion concentration The important conclusion of this study is, first, hydrophobic acid macromolecules are recommended to be added into feed water to improve the rejection of trace hormone during NF/RO membrane process, and, second, removal of calcium ions via pretreatment and application of membrane with more negative charge at its interface can greatly intensify this "enhancement effect" (C) 2009 Elsevier Ltd All rights reserved
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  • Biodiesel production by microalgae cultivated using permeate from membrane bioreactors in continuous system.

    Low, Siok Ling   Ong, Say Leong   Ng, How Yong  

    Microalgae in three submerged ceramic membrane photobioreactors (SCMPBRs) with different hydraulic retention times (HRTs) were fed with permeate of a submerged ceramic membrane bioreactor for a period of 3 months to investigate the lipid content and also the biodiesel quality produced at different HRTs. The lipid content, lipid productivity and fatty acid compositions for all three SCMPBRs were not significantly different at the 95% confidence level. These results suggested that insigni=EF=AC=81cant change in the amount of fatty acids was observed at different HRTs that supplied varying concentration of nitrate in the medium. Among the fatty acids, palmitic acid, palmitoleic acid, oleic acid and linoleic acid were the main components, whereas stearic acid was a minor fatty acid. Since there was insignificant effect of HRT on lipid content, lipid productivity and fatty acid compositions, the optimum HRT for SCMPBRs can then be designed based on optimum nutrient removal performance and low membrane fouling propensity. =20
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  • A mesophilic Clostridium species that produces butanol from monosaccharides and hydrogen from polysaccharides

    Bramono, Sandhi Eko   Lam, Yuen Sean   Ong, Say Leong   He, Jianzhong  

    A unique mesophilic Clostridium species strain BOH3 is obtained in this study, which is capable of fermenting monosaccharides to produce butanol and hydrolyzing polysaccharides to produce hydrogen (H(2)) and volatile fatty acids (VFAs). From 30 g/L of glucose and xylose each, batch culture BOH3 was able to produce 4.67 and 4.63 g/L of butanol. Enhancement treatments by increasing the inoculated cells improved butanol production to 7.05 and 7.41 g/L, respectively. Hydrogen production (2.47 and 1.93 mmol) was observed when cellulose and xylan (10 g/L each) were used, suggesting that strain BOH3 possesses xylanolytic and cellulolytic capabilities. These unique features reveal the strain's novelty as most wild-type solventogenic strains have not been reported to have such properties. Therefore, culture BOH3 is promising in generating butanol and hydrogen from renewable feedstock. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
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