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Galjaard G.,PWN Technologies andijk | Clement J.,PWN Technologies andijk | Ang W.S.,Singapores National Water Agency | Lim M.H.,Singapores National Water Agency
Water Practice and Technology | Year: 2012

Ceramic membrane technology is used in water treatment due to the robustness of ceramic membranes, but ceramic membrane systems are costly as each membrane module is housed in individual casing. PWNT has developed a ceramic membrane system called the CeraMac which greatly reduced the capital cost of installing the system by housing up to 200 modules in a single stainless steel vessel. PWNT and PUB have jointly started a 18-month operation at Choa Chu Kang Waterworks (CCKWW). In this paper, the results of the optimization runs using settled water as feed has shown that membrane operation at flux of 200 lmh can be sustained with stable transmembrane pressure (TMP) and permeability, and the proposal to apply 0.5 mg/L residual ozone to the feed to investigate the effect of ozonated feed on membrane operational performance and fouling will be discussed. © IWA Publishing 2012. Source


Agus E.,University of California at Berkeley | Lim M.H.,Singapores National Water Agency | Zhang L.,Singapores National Water Agency | Sedlak D.L.,University of California at Berkeley
Environmental Science and Technology | Year: 2011

The presence of effluent-derived compounds with low odor thresholds can compromise the aesthetics of drinking water. The potent odorants 2,4,6-trichloroanisole and geosmin dominated the profile of odorous compounds in wastewater effluent with concentrations up to 2 orders of magnitude above their threshold values. Additional odorous compounds (e.g., vanillin, methylnaphthalenes, 2-pyrrolidone) also were identified in wastewater effluent by gas chromatography coupled with mass-spectrometry and olfactometry detection. Full-scale advanced treatment plants equipped with reverse osmosis membranes decreased odorant concentrations considerably, but several compounds were still present at concentrations above their odor thresholds after treatment. Other advanced treatment processes, including ozonation followed by biological activated carbon and UV/H 2O 2 also removed effluent-derived odorants. However, no single treatment technology alone was able to reduce all odorant concentrations below their odor threshold values. To avoid the presence of odorous compounds in drinking water derived from wastewater effluent, it is necessary to apply multiple barriers during advanced treatment or to dilute wastewater effluent with water from other sources. © 2011 American Chemical Society. Source


Ho J.S.,Nanyang Technological University | Ho J.S.,Singapores National Water Agency | Ma Z.,Shandong University of Science and Technology | Ma Z.,National University of Singapore | And 3 more authors.
Desalination | Year: 2015

To help resolve issues associated with reverse osmosis (RO) brine handling for inland water reuse plants, RO brine treatment and recovery from NEWater factory was demonstrated in a laboratory using a low cost, less footprint and low energy consumption pretreatment method of inline coagulation-ultrafiltration (UF). Polyaluminum chloride (PACl), aluminum chlorohydrate (ACH) and ferric chloride (FeCl3) were chosen as the coagulants. PACl and ACH attained dissolved organic carbon (DOC) removal of 31% and 27% respectively at the optimal dosage (0.556mM as Al), while FeCl3 outperformed PACl and ACH at this molar dosage, reaching up to 60% of DOC removal. At the optimal pH (pH7), FeCl3 was again more superior with the highest DOC removal efficiency of 55%. FeCl3 also presented the highest phosphate (>99%) and silica removals (14%) at its optimum dosage and pH. Liquid chromatography-organic carbon detector (LC-OCD) and fluorescence excitation-emission matrix (EEM) were used to characterize the DOC fractions removed by inline coagulation-UF. For LC-OCD, FeCl3 revealed higher removal efficiency for almost all the DOC fractions ranging from low to high molecular weight. These results suggest that the inline-coagulation (FeCl3)-UF pretreatment is potential in reducing the fouling tendency of downstream RO because of its high DOC and phosphate removal efficiency. © 2015 Elsevier B.V. Source


Yu J.,Singapores National Water Agency | Yu J.,Yangzhou University | Qin J.,Singapores National Water Agency | Kekre K.A.,Singapores National Water Agency | And 3 more authors.
Journal of Water Reuse and Desalination | Year: 2014

The study aimed at further developing an integrated capacitive deionisation (CDI)-based process to treat reverse osmosis (RO) brine from a water reclamation facility to increase the overall water recovery to more than 90% and to achieve a sustainable operation of the process with optimised conditions. The normalised treatment capacity of CDI membranes and voltage was optimised at 24.8 L/m2/h and 1.1-1.5 V, respectively. The operation time of CDI cell with membrane area of 0.8 m2 was able to be extended to more than 1,000 h from the initial 72 h. Cleaning with both HCl at low pH and salt solution was good in removing foulants but cleaning with citric acid was not effective, as expected. The initiative cleaning strategy was found to be more effective in CDI fouling control and is recommended for long-term CDI operation. CDI cell efficiency for removal of ions reduced with operation time due to cleaning with surfactants at pH 10.5 which should be avoided in a future study. © IWA Publishing 2014. Source


Qin J.-J.,Singapores National Water Agency | Oo M.H.,Singapores National Water Agency | Kekre K.A.,Singapores National Water Agency | Knops F.,NORIT X Flow
Desalination and Water Treatment | Year: 2012

We have demonstrated an integrated coagulation-ultrafiltration (UF) process for enhanced removals of phosphate and dissolved organic carbon (DOC) in tertiary treatment. A lab scale system with hollow fiber UF membranes was used in the study. Dead-end operation was applied in the study since its advantages of low energy consumption and high water recovery over cross-flow operation. The results showed that removals of phosphate and DOC at alum dosage of 10 mg l-1 in the study were >99% (or phosphate <0.03 mg l-1 in product) and 25%, respectively. The coagulation time in the new integrated coagulation-UF process was reduced to 1 min with much less foot-print. The concentration of alum dose could be further optimized between 5 and 10 mg l-1. © 2012 Desalination Publications. All rights reserved. Source

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