Singapores National Water Agency

Singapore, Singapore

Singapores National Water Agency

Singapore, Singapore
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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.


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.


Galjaard G.,PWN Technologies | Clement J.,PWN Technologies | Ang W.S.,Singapores National Water Agency | Lim M.H.,Singapores National Water Agency
AMTA/AWWA Membrane Technology Conference and Exposition 2013 | Year: 2013

Ceramic membrane technology is known for its robustness of the ceramic membranes, but ceramic membrane systems have historically been too costly for installation in drinking water treatment plants, primarily due to the traditional configuration of each membrane module being housed in individual stainless steel casings, which is costly. PWN Technologies (PWNT) has developed a different ceramic membrane system configuration, called the CeraMac® which greatly reduces the capital cost by housing up to 200 modules in a single, stainless steel vessel. PWNT, together with PUB, Singapore's National Water Agency, has embarked on a rigorous and systematic evaluation of the newly developed CeraMac® system at the Choa Chu Kang Waterworks (CCKWW). The demonstration plant testing began with coagulated and clarified feed water from the existing CCKWW. The findings of this phase of testing were that the CeraMac® system can operate with a flux of 200 lmh, a backwash interval of 30 minutes, and an enhanced backwash interval of once every 30 backwashes when treating clarified water. Membrane permeability was stable at approximate 325 lmh/bar at a water recovery of 96.88%. In this phase, fluctuations of transmembrane pressure (TMP) and permeability were also observed, mainly owing to changes in feed water quality. In a second phase of the demonstration study, ozone was applied to the clarified feed water to investigate the effect on membrane operational performance. The results of these tests exceeded expectations. The combination of ozone with CeraMac® significantly improved the system's performance, with stable operation, lower TMP, increased permeability, and increased recovery. The CeraMac® system operated with a flux of >240 lmh, a backwash interval of 180 minutes, and an enhanced backwash interval of once every 4 backwashes when treating ozonated clarified water. A membrane permeability of 850 lmh/bar and a water recovery of 99.3 % were achieved. This flux was the maximum that could be achieved by the equipment that was installed in the demonstration plant. © 2013 American Water Works Association.


Wang J.,Xylem Services GmbH | Ried A.,Xylem Services GmbH | Stapel H.,Xylem Services GmbH | Zhang Y.,Xylem Services GmbH | And 6 more authors.
Water Practice and Technology | Year: 2015

A two-year comprehensive advanced oxidation processes (AOPs) pilot test was completed for a Singapore waterworks in 2011–2013. This study focused on oxidative removal of spiked organic contaminants with ozone and ozone-based AOPs (ozone application together with hydrogen peroxide, which is necessary for AOPs). The ‘optimized H2O2 dosage’ test philosophy was verified during the test period – keeping the residual ozone at 0.3 mg/L in the water for disinfection purpose by minimizing the H2O2 dosage. This study also monitored the bromate concentration in both ozone- and AOP-treated water, and all the samples reported below the laboratory detection limit (,5 µg/L), which is also lower than the WHO Guidelines for Drinking Water Quality (,10 µg/L). For comparison, a low pressure UV-based AOP test was conducted in the final stage of the study. The electrical energy per order (EEO) value is compared with ozone- and UV-based AOPs as well. The results indicated that ozone-based AOP with an optimized hydrogen peroxide dosage could be the most energy efficient option for this specific water matrix in terms of most selected compounds. © IWA Publishing 2015.


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.


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.


Wang J.,Xylem Water Solutions Herford GmbH | Ried A.,Xylem Water Solutions Herford GmbH | Wieland A.,Xylem Water Solutions Herford GmbH | Zhang Y.,Xylem Water Solutions Herford GmbH | And 7 more authors.
Water Practice and Technology | Year: 2012

In response to the national water strategies and pursuing to close the urban water loop with minimum concern, a proactive approach needs to be considered for future drinking water treatment process in Singapore. Ozone or ozone based advanced oxidation process (AOP) followed by granular activated carbon (GAC) can be one of the best available and cost-effective processes in implementing the national water strategies.Xylem Water Solutions and PUB jointly started a two-year ozone based AOP pilot study at a Waterworks in Singapore. The objective of the project is to study the effectiveness of ozone based AOP on the removal of taste and odour compounds and various emerging organic contaminants. In this paper, the first year results with six selected contaminants show that it is promising to employ ozone based AOP to remove the concerned organic contaminants. © IWA Publishing 2012.


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.


Quek B.S.,Singapores National Water Agency | He Q.H.,Singapores National Water Agency | Sim C.H.,Singapores National Water Agency
Water Science and Technology | Year: 2015

The Alexandra Wetlands, part of PUB's Active, Beautiful, Clean Waters (ABC Waters) Programme, showcase a surface flow wetland, an aquatic pond and a sub-surface flow wetland on a 200 m deck built over an urban drainage canal. Water from the canal is pumped to a sedimentation basin, before flowing in parallel to the three wetlands. Water quality monitoring was carried out monthly from April 2011 to December 2012. The order of removal efficiency is sub-surface flow (81.3%) >aquatic pond (58.5%) >surface flow (50.7%) for total suspended solids (TSS); sub-surface (44.9%) >surface flow (31.9%) >aquatic pond (22.0%) for total nitrogen (TN); and surface flow (56.7%) >aquatic pond (39.8%) >sub-surface flow (5.4%) for total phosphorus (TP). All three wetlands achieved the Singapore stormwater treatment objectives (STO) for TP removal, but only the sub-surface flow wetland met the STO for TSS, and none met the STO for TN. Challenges in achieving satisfactory performance include inconsistent feed water quality, undesirable behaviour such as fishing, release of pets and feeding of animals in the wetlands, and canal dredging during part of the monitoring period. As a pilot showcase, the Alexandra Wetlands provide useful lessons for implementing multi-objective wetlands in an urban setting. © IWA Publishing 2015.


PubMed | Singapores national water agency
Type: Journal Article | Journal: Water science and technology : a journal of the International Association on Water Pollution Research | Year: 2015

The Alexandra Wetlands, part of PUBs Active, Beautiful, Clean Waters (ABC Waters) Programme, showcase a surface flow wetland, an aquatic pond and a sub-surface flow wetland on a 200 m deck built over an urban drainage canal. Water from the canal is pumped to a sedimentation basin, before flowing in parallel to the three wetlands. Water quality monitoring was carried out monthly from April 2011 to December 2012. The order of removal efficiency is sub-surface flow (81.3%) >aquatic pond (58.5%) >surface flow (50.7%) for total suspended solids (TSS); sub-surface (44.9%) >surface flow (31.9%) >aquatic pond (22.0%) for total nitrogen (TN); and surface flow (56.7%) >aquatic pond (39.8%) >sub-surface flow (5.4%) for total phosphorus (TP). All three wetlands achieved the Singapore stormwater treatment objectives (STO) for TP removal, but only the sub-surface flow wetland met the STO for TSS, and none met the STO for TN. Challenges in achieving satisfactory performance include inconsistent feed water quality, undesirable behaviour such as fishing, release of pets and feeding of animals in the wetlands, and canal dredging during part of the monitoring period. As a pilot showcase, the Alexandra Wetlands provide useful lessons for implementing multi-objective wetlands in an urban setting.

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