Conventional Surface Water Treatment Plant Research Articles

Efficiency of a gravity-driven membrane in a water treatment plant

Abstract Membrane filtration technology is widely applied in conventional surface water treatment plants because of its low power load and high filtration accuracy. This study follows the transition from a power-driven to a gravity-driven siphon-submerged ultrafiltration membrane system in a drinking water treatment plant in Shandong Province, China. The proportion of space membrane areas in the tank was further developed, by increasing the membrane areas of a single tank to 1.6 times that before the transformation, and the design production capacity of a single tank is increased from 10,000 m3/d before the transformation to 16,700 m3/d. The recovery rate of a single tank was also increased from 96.28 to 97.77%. The energy consumption per ton of water decreased from 0.06 to 0.017 MJ. The annual carbon emissions reduction reached 197.13 tons per tank. In terms of the water quality, the algae removal rate from surface water by the ultrafiltration membrane reached 100%. Further, the removal rates of 2 μm particles, turbidity, and chlorophyll were above 99%. Our results suggest that gravity-driven siphon-submerged ultrafiltration promotes environmental protection, energy conservation, and emissions reduction. This technology introduces a new development direction for membrane filtering in drinking water treatment plants.

The significance of the biomass subfraction of high-MW organic carbon for the microbial growth and maintenance potential of disinfectant-free drinking water produced from surface water

Drinking water must be sufficiently biostable to avoid excessive microbial and invertebrate growth in disinfectant-free distribution systems. The production of biologically stable drinking water is challenging for conventional surface water treatment plants using reservoirs as feed water due to the presence of slowly biodegradable particulate and high-molecular weight biopolymeric organic carbon (high-MW OC) which increases the Microbial Growth Potential (MGP) in the feed water and produced drinking water. The study presented here provides new insights in the relationship between high-MW OC and MGP for a full-scale surface water treatment plant. Controlled-conditions addition series experiments showed that MGP increases linearly with the high-MW OC concentration with a seasonally variable ratio. Laboratory filtration indicated that MGP is mainly attributable to the high-MW OC subfraction of > 0.12µm particle size coinciding with microbial biomass. Intensive field monitoring revealed clear seasonal patterns in the plant's feed water and treated water levels of high-MW OC, biomass and MGP. These parameters reach maximum levels in the periods of high water temperature with the notable exception of the treated water's high-MW OC concentration which exhibits an opposite seasonal pattern (reflecting seasonally variable removal in the treatment). Moreover, the field monitoring showed that MGP correlates well with the concentrations of biodegradable biopolymeric OC and with microbial biomass measured as ATP (adenosine triphosphate) and cell counts, but not with the total high-MW OC concentration in the treated water. Theoretical estimations showed that the OC quantities present in and consumed by the microbial biomass are in the same order of magnitude as slowly biodegradable biopolymers. From these results it is concluded that specifically the microbial biomass-associated and biodegradable biopolymeric OC subfraction of the totally present high-MW OC is important for MGP. Finally, the MGP-assay results and theoretical calculations showed for the high-MW OC matrix that the microbial biomass' OC consumption for maintenance is significant vis-á-vis that for growth, and that stable and high levels of biomass are sustained in the treated water which may adversely affect biological stability in the distribution network.

What Don't You Know About Your Distribution System?

The Partnership for Safe Water, a continuous improvement and optimization program, was launched in 1995 with a suite of resources focused on self‐assessment and continuous improvement for conventional surface water treatment plants. During the past 25 years, the program and the resources available to subscribing utilities have grown and evolved, much as the regulatory requirements have grown and changed with the availability of new information.

Enhancing biological stability of disinfectant-free drinking water by reducing high molecular weight organic compounds with ultrafiltration posttreatment

The production of biologically stable drinking water is challenging in conventional surface water treatment plants. However, attainment of biological stability is essential to avoid regrowth in disinfectant-free distribution systems. A novel application of ultrafiltration as a posttreatment step to enhance biological stability of drinking water produced in an existing conventional surface water treatment plant was investigated. The conventional full-scale plant comprised coagulation/sedimentation/filtration, UV-disinfection, biological activated carbon filtration and chlorine dioxide post-disinfection. The produced water exhibited substantial regrowth of Aeromonads, invertebrates and colony counts in the distribution network. Recent literature attributes this phenomenon to the specific presence of slowly biodegradable, high molecular weight (MW) biopolymeric organic compounds. Hence, the aim of this study is to enhance the biological stability of conventionally treated surface water by reducing the concentration of high-MW organic compounds. For this purpose, biological active carbon filtrate was subjected to ultrafiltration with membrane pore sizes of 10 kDa, 150 kDa and 0.12 μm respectively, operating in parallel. The UF performance was evaluated in terms of the achieved reduction in particulate and high-MW organic carbon (PHMOC); the biopolymer fraction in Liquid Chromatography-Organic Carbon Detection; biomass (cells, ATP); Assimilable Organic Carbon (AOC) by the AOC-P17/NOX method for easily biodegradable, low-MW compounds and by the AOC-A3 method for slowly biodegradable, high-MW compounds; and overall microbial growth potential (MGP) as assessed by Biomass Production Potential (BPP) and Bacterial Growth Potential (BGP) bio-assays. Results showed increasing removal of high-MW organic carbon with decreasing UF pore size, i.e., 30%, 60% and 70% removal was observed for the 0.12 μm, 150 kDa and 10 kDa membranes, respectively. Biomass and particulates retention was more than 95% for all UF membranes. AOC-A3, BPP and BGP were substantially reduced by 90%, 70% and 50%, respectively. These respective reductions were similar for all three UF membranes despite their difference in pore size. Easily biodegradable organic compounds (as AOC-P17/NOX) were not reduced by any of the membranes, which was in accordance with expectations considering the low MW of the compounds involved. Based on the obtained results, growth potential appears to be largely attributable to high-MW organic compounds which are retained by a 0.12 μm UF membrane. Furthermore, the quality of all three UF permeates was equal to or better than in reference cases (literature data) which exhibit little regrowth in their disinfectant-free distribution networks. The results demonstrate that ultrafiltration posttreatment in conventional surface water treatment plants is a potentially promising approach to enhance the biological stability of drinking water.

Centralized Drinking Water Treatment Operations Shape Bacterial and Fungal Community Structure.

Drinking water microbial communities impact opportunistic pathogen colonization and corrosion of water distribution systems, and centralized drinking water treatment represents a potential control for microbial community structure in finished drinking water. In this article, we examine bacterial and fungal abundance and diversity, as well as the microbial community taxonomic structure following each unit operation in a conventional surface water treatment plant. Treatment operations drove the microbial composition more strongly than sampling time. Both bacterial and fungal abundance and diversity decreased following sedimentation and filtration; however, only bacterial abundance and diversity was significantly impacted by free chlorine disinfection. Similarly, each treatment step was found to shift bacterial and fungal community beta-diversity, with the exception of disinfection on the fungal community structure. We observed the enrichment of bacterial and fungal taxa commonly found in drinking water distribution systems through the treatment process, for example, Sphingomonas following filtration and Leptospirillium and Penicillium following disinfection. Study results suggest that centralized drinking water treatment processes shape the final drinking water microbial community via selection of community members and that the bacterial community is primarily driven by disinfection while the eukaryotic community is primarily controlled by physical treatment processes.

Assessing and maintaining membrane performance in a post-sedimentation ultrafiltration process

A pilot test program was conducted to evaluate methods for maintaining the productivity of a hollow fiber ultrafiltration membrane operating at constant flux values of 49.2 and 62.3 gallons/ft2-day. The ultrafiltration pilot filtered settled water from a conventional surface water treatment plant in Florida. The testing assessed the impact of different chemical maintenance protocols on UF membrane performance. Seasonal variations in water quality necessitated changes in the type and combination of cleaning agents used to maintain membrane performance. Sodium hypochlorite, citric acid and sodium hydroxide were used during pilot testing as the fouling characteristics of the water changed with time. Pilot results were used to develop alternative chemically enhanced backwash strategies that varied with seasonally-impacted changes in feed water quality. Citric acid, with a target pH of <3, was found to be effective in August and September; whereas, a combination of citric acid and high pH sodium hydroxide chemically enhanced backwashes successfully maintained performance between November, 2010 and May, 2011.

Disinfection characteristics of the dissolved organic fractions at several stages of a conventional drinking water treatment plant in Southern China

Dissolved organic matter (DOM) influences many aspects of drinking water treatment, including the formation of harmful disinfection by-products (DBPs) when disinfectants are applied. DOM was isolated and fractionated using membrane ultra-filtration (UF) and reverse osmosis (RO) to eight individual fractions based on molecular weight cut-offs from a conventional surface water treatment plant (WTP) in Guangzhou of PR China. Molecular weights of these eight fractions were further calibrated using high performance size exclusion chromatography (HPSEC) and they ranged from 0.36 to 182.6 kDa. Fractions with molecular weight <0.80 kDa obtained by YC-05 UF membrane and RO were the major ones in all four stages of the water treatment processes; both ZM-500 and YM-100 membranes showed the highest removal efficiency when coupling with conventional coagulation and sedimentation processes. The elemental analysis showed that YC-05 fraction had greater polarity and aromaticity than any of the others. Furthermore, disinfection characteristics and trihalomethane formation potential (THMFP) were determined for all DOM fractions obtained in this study. YC-05 fraction was the major precursor for trihalomethane (THMs) formation among the samples tested and could be removed effectively by particulate activated carbon (PAC) adsorption. RO fraction could not be removed by PAC adsorption and, as a result, consumed more chlorine in the disinfection process. The results suggested that advanced drinking water treatment should focus on the removal of low molecular weight DOM in the source water.

Development and implementation of the software mEnCo© to predict coagulant doses for DOC removal at full-scale WTPs in South Australia

Research Article| June 01 2009 Development and implementation of the software mEnCo© to predict coagulant doses for DOC removal at full-scale WTPs in South Australia J. van Leeuwen; J. van Leeuwen 1University of South Australia, Centre for Water Management and Reuse, School of Natural and Built Environments, H-Building Level 3, Mawson Lakes Campus, Adelaide South Australia, Australia E-mail: john.vanleeuwen@unisa.edu.au Search for other works by this author on: This Site PubMed Google Scholar M. Holmes; M. Holmes 2United Water International, GPO Box 1875, Adelaide 5501, SA, Australia Search for other works by this author on: This Site PubMed Google Scholar U. Kaeding; U. Kaeding 2United Water International, GPO Box 1875, Adelaide 5501, SA, Australia Search for other works by this author on: This Site PubMed Google Scholar R. Daly; R. Daly 3Australian Water Quality Centre, SA Water, Hodgson Road, Bolivar 5110, SA, Australia Search for other works by this author on: This Site PubMed Google Scholar D. Bursill D. Bursill 1University of South Australia, Centre for Water Management and Reuse, School of Natural and Built Environments, H-Building Level 3, Mawson Lakes Campus, Adelaide South Australia, Australia Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2009) 58 (4): 291–298. https://doi.org/10.2166/aqua.2009.054 Article history Received: June 18 2008 Accepted: October 21 2008 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation J. van Leeuwen, M. Holmes, U. Kaeding, R. Daly, D. Bursill; Development and implementation of the software mEnCo© to predict coagulant doses for DOC removal at full-scale WTPs in South Australia. Journal of Water Supply: Research and Technology-Aqua 1 June 2009; 58 (4): 291–298. doi: https://doi.org/10.2166/aqua.2009.054 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Conventional surface water treatment plants (WTPs) rely on optimised coagulation for effective clarification, filtration and chlorination performance. WTPs operated at sub-optimal coagulation conditions are at risk from failing treated water microbial, disinfection by-product, chemical and aesthetic quality goals as well as incurring excessive sludge production and treatment cost. This is especially important when treating water that contains a high concentration of natural organic matter (NOM). Removal of NOM by coagulation can be enhanced by optimising the inorganic coagulant dose and coagulation pH. This paper describes the development and implementation of a software model mEnCo© (referring to modelling enhanced coagulation) that enables WTP operators to rapidly determine coagulation chemicals. Implementation was carried out in a four-stage process comprising model evaluation by (1) jar tests and pilot-scale studies, (2) comparison of mEnCo© predictions with historical water quality and coagulant dose trends at Adelaide metropolitan WTPs, (3) parallel studies where mEnCo© predictions were compared with the usual methods applied by operators for chemical dose determination and (4) application of mEnCo© for dose determination and review. United Water International (UWI) began using mEnCo© in July 2003 for prediction of chemical doses for coagulation control and have used the model from July 2004 to adjust coagulant doses. coagulation, DOC, model, optimization, software, water treatment This content is only available as a PDF. © IWA Publishing 2009 You do not currently have access to this content.

Study on ultrafiltration for surface water by a polyvinylchloride hollow fiber membrane

Low pressure membrane filtration processes are increasingly competing against conventional surface water treatment plants. In comparison with conventional processes, UF technology has many advantages, but it is also important that a kind of membrane is suitably selected and operated. In this paper, a pilot plant study on a polyvinylchloride ultrafiltration (MWCO of 80 kD) hollow fiber membrane process was performed for the treatment of surface water. The new membrane had an optimized pore size distribution over membrane thickness while membrane material and fiber dimensions remained the same, the modification resulted in a much higher pure water flux (160 l/(m 2 h bar) at 20°C). The membrane system was operated in the dead-end filtration modes with different constant permeate fluxes. The results showed that the permeate quality was stable, regardless of different surface water for a long duration of filtration. The transmembrane pressure should be operated in less than 1 bar to avoid irreversible fouling. Treating cold raw water below 5°C in constant pressure operation mode was better than in constant permeate flux.

Fate of THMs and HAAs in low TOC surface water

A total of 30 conventional surface water treatment plants (WTPs) implementing prechlorination and postchlorination simultaneously from different regions in Korea were investigated to assess formation and removal of THMs and HAA 5. All water was low in total organic carbon (TOC) ranging from 0.74 to 6.20 mg/L with an average of 1.63 mg/L. The ranges of THMs and HAA 5 levels were 4.5–84.3 μg/L and 1.5–90.8 μg/L, respectively. THMs concentration was more sensitive to water temperature than HAA 5 and the ratio of THMs in summer over winter was 2.06. The sum of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) was 97% of HAA 5. The extent of formation and speciation of DBPs varied greatly by season and geography. The concentration of DCAA and TCAA of the finished water was comparable on a yearly base, but more TCAA was noticed in summer and the opposite trend was noticed in winter. This can be caused by different biodegradability in the sand filter between DCAA and TCAA that formed through prechlorination. Investigation on the removal of preformed DBPs in the GAC filter–adsorber (FA) revealed that breakthrough of THMs and HAA 5 was noticed after 3 months of operation. However, gradual improvement (>90%) in HAA 5 removal was observed again after breakthrough, which could be attributable to biodegradation. Heterotrophic plate counts confirmed active biological activity in the GAC FA.

Filter Aid Injection Manifold Enhances Operations

This article discusses the Filter Aid Injection Manifold that uses ram water from the house system water supply lines to break the head of the influent water to the filter. Filter aid is fed at low feed rates of about 0.16 mg/L. The ram water and manifold nozzles provide a more uniform and constant dispersion of the chemical, and the higher velocity of the solution creates cleaner feed lines. Results and benefits of using the manifold at the Eugene (Oregon) Water and Electric Board's 72‐mgd conventional surface water treatment plant are discussed.

Riverbank Filtration for IESWTR Compliance

The Central Wyoming Regional Water System operates 29 groundwater collection devices in an alluvial aquifer adjacent to the North Platte River. These collection devices were previously designated “groundwater under the direct influence of surface water.” In lieu of constructing a conventional surface water treatment plant, the utility opted to perform a two‐year study to demonstrate that riverbank filtration (i.e., natural filtration) provided the 2.0‐log reduction of Cryptosporidium required under the Interim Enhanced Surface Water Treatment Rule (e.g., riverbank filtration is the primary filtration process). Using multiple surrogates of various sizes encompassing those of Giardia and Cryptosporidium, the utility demonstrated 2.0‐log reductions in more than 90% of matched data pairs. No Giardia cysts or Cryptosporidium oocysts were found in any of the 170 groundwater samples. This level of removal was achieved during the summer months when infiltration rates are high because of increased river stage and well‐field production.

Comparison of process options for treatment of water treatment residual streams

Spent filter backwash water (SFBW) and clarifier sludge comprise the majority of the waste streams from conventional surface water treatment plants and collectively are referred to as composite residuals stream. Composite residuals streams can comprise up to 3–10% of the plant throughput and generally consist of concentrated metals (e.g., aluminum), colloidal material, natural organic matter (NOM), and pathogens (e.g., Giardia and Cryptosporidium). This research project evaluated the performance of four different treatment processes in terms of their capability of restoring this waste stream to a quality that was equal to or better than that of the source water quality. The unit operations evaluated were (i) gravity thickening, (ii) sedimentation with reflocculation, (iii) dissolved air flotation (DAF) with reflocculation, and (iv) ultrafiltration (UF). The water quality from the optimal trials met or exceeded the average raw water quality of the source water for all measured parameters with the exception of manganese. The optimal pH for sedimentation was determined to be 6.0 with no alum addition. The best coagulant dosage and recycle ratio for dissolved air flotation (DAF) were found to be 30 mg/L and 20%, respectively. The optimum settling time for thickening was determined to be 0.8–1.0 d, after which soluble metal concentrations began to increase because of re-solubilization. Ultrafiltration required no coagulant and yielded superior results to the other unit operations evaluated. Key words: filter backwash water, residual treatment, gravity thickening, sedimentation, dissolved air flotation, ultrafiltration.

Improving eco-efficiency of Amsterdam water supply: A LCA approach

Amsterdam Water Supply produces 70 million m 3 drinking water per annum in its Leiduin plant and is considering increasing the plant capacity to 83 million m 3 per annum. The existing plant is a conventional surface water treatment plant. For capacity expansion, two alternative treatment schemes, each using reverse osmosis, are being considered. In these considerations, environmental impact plays an important role. Environmental impact of the plant was assessed with life cycle analysis. The total impact for annual production from the existing and the two future alternative schemes are 2.89E+04, 3.65E+04 and 3.44E+04 eco-points respectively. The significant impact contributors are the use of conventional energy, softening and the granular activated carbon process. Impact reduction up to 73% may be achieved by the use of 100% green energy, the use of an alternative chemical [Na 2 CO 3 in place of NaOH] in the softening process and doubling the carbon run time.

The variation of mass and disinfection by-product formation potential of dissolved organic matter fractions along a conventional surface water treatment plant

Dissolved organic matter (DOM) influences many aspects of water treatment, including the formation of potentially harmful disinfection by-products (DBPs) when disinfectants are applied. DOM from a conventional surface water treatment plant (WTP) in Northern New Jersey was isolated and fractionated using resin adsorption chromatography into six different fractions. These fractions are operationally categorized as hydrophobic acid, hydrophobic neutral, hydrophobic base, hydrophilic acid, hydrophilic neutral and hydrophilic base. The hydrophilic acid fraction was found to be the most abundant fraction in the source water. The hydrophilic neutral, hydrophilic acid and hydrophobic acid fractions had the highest removal efficiency through the WTP (about 65%). The variation and removal effectiveness of each fraction along the WTP was studied. Seven-day chlorine DBP formation potential (FP) tests were performed on all DOM fractions through the WTP. For the source water studied, the hydrophilic acid fraction was found to be the most reactive precursor to the trihalomethane (THM) formation. The hydrophobic neutral fraction was found to be the fraction of concern with respect to the FP of haloacetic acids (HAAs) class of DBPs. The FP of each fraction's class of DBPs was found to be amenable for reduction along the treatment train, specifically by coagulation/sedimentation. The fractionated approach concept showed to be very beneficial in the study of DBP precursors and their effective removal by physical and chemical treatment.

Rapid delineation of humic and non-humic organic matter fractions in water

Dissolved organic matter (DOM) in water is often characterized by aggregate parameters like dissolved organic carbon (DOC). DOM from conventional surface water treatment plant in Northern New Jersey was isolated and fractionated using resin adsorption chromatography into six different fractions, which were operationally categorized as hydrophobic acid, hydrophobic neutral, hydrophobic base, hydrophilic acid, hydrophilic neutral and hydrophilic base. The spectral fluorescent signatures (SFS) technique was developed for the quantitative identification of the six fractions by post-processing analysis that includes a statistical model. The SFS is the total sum of emission spectra of a sample at different excitation wavelengths, recorded as a matrix of fluorescent intensity in coordinates of excitation and emission wavelengths, in a definite spectral window. High sensitivity and rapid identification and quantification of DOM fractions are among the main features of the technique. Since hydrophobic and hydrophilic substances are considered more humic and non-humid in nature, respectively, the technique provided an opportunity to rapidly delineate source waters in terms of such categories.

Ultrafiltration of surface water with ®MOLPURE FW50 hollow fibre module

Low pressure membrane filtration processes are increasingly competing against conventional surface water treatment plants. In this paper the ®MOLPURE FW50 technology for surface water treatment is presented, its operating procedure described and experiences from different projects reported.