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Concise Abstract 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 increase 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 > 0.12 µm particle size coinciding with microbial biomass. Intensive field monitoring revealed clear seasonal patterns in the plant's feed water and treated water high-MW OC, biomass and MGP levels. 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, field monitoring showed that MGP correlates well with the concentrations of biodegradable biopolymeric OC and 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 measurable 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-a-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.

This study examined primary data on the energy use (electricity and natural gas) of nine surface water treatment plants in and around Salt Lake City, Utah, and how their energy use relates ...

The microbial endogenous respiration process is very important in biological water treatment processes. This study analyzed and compared the endogenous respiration process in an attached growth membrane bioreactor (aMBR) system and a UV/O3 integrated aMBR system (UV/O3-aMBR) in treating polluted surface water with CODMn around 10 mg/L. The endogenous respiration activity of heterotrophic microbes and autotrophic nitrifiers activity in both systems was analyzed and compared. Results show that heterotrophic bacteria and autotrophic nitrifiers enter endogenous respiration at 6 h aeration in an aMBR and 0 h in a UV/O3-aMBR system. Biomass amount on PVA-gel in aMBR was higher than in UV/O3-aMBR in terms of specific respiration rates SOURt, SOURH, and SOURA. Substrate remained on PVA-gel in the aMBR system, but no substrate remained on PVA-gel in the UV/O3-aMBR system. Higher species of microbes, including recoverable and irrecoverable components, existed in the aMBR system as compared to the UV/O3-aMBR system. The UV/O3-aMBR system could make full use of the advanced oxidation process (AOP) and biological process, leading to a higher treatment performance, and has the potential to mitigate total energy demand. Thus, the UV/O3-aMBR system can be used as a new technology for treating polluted surface water with the co-contribution of biological process and AOP treatment.

Several pharmaceuticals were followed through a drinking water production process on the river Meuse. Tramadol and levetiracetam were the most common compounds while cytostatics were not detected. All compounds found at that intake point had an annual consumption greater than 90 mg/inhabitant. The tracer substance 1,2,3-benzotriazole allowed estimation of the maximal concentration of pharmaceuticals and the evolution profile for tramadol and sotalol. After pre-ozonation of raw water, most pharmaceuticals were completely removed, except levetiracetam and irbesartan, confirming the efficiency of this advanced oxidation process. Irbesartan and levetiracetam were completely removed by granular activated carbon filtration. Levetiracetam was the most reluctant compound. A conventional multi-barrier treatment combining ozone and activated carbon, already used for several decades before implementation in wastewater treatment, can completely remove most pharmaceuticals. Therefore, drinking water without any significant health-related amount of these pharmaceuticals can be produced from surface water.

In this work, volcanic rocks were used as particle electrodes to construct a volcanic rock three-dimensional (3D) electrode reactor. In a wide pH range (3 ~ 11), volcanic rocks can degrade norfloxacin (NOR) at low voltage (4 V) within 40 min. In acidic environment, the NOR removal was greater than 85%. Volcanic rock also showed excellent electrocatalytic activity when treating ofloxacin, methylene blue and other pollutants. After six cycles, the weight loss rate of volcanic rocks was 3.87%. Volcanic rocks had high mechanical strength stability. There were hydroxyl radicals ( OH) and superoxide radical (O2 −) produced in the volcanic rock 3D system. The volcanic rock surface was the main location of NOR degradation. The possible degradation mechanism and the degradation pathway of NOR were proposed. In addition, volcanic rock also showed excellent effects in actual surface water treatment.

Naturally present aquatic microorganisms play an important role in water purification systems, such as the self-purification of surface waters. In this study, two water sources representing polluted surface water (Olympic Green; OG) and unpolluted surface water (Jingmi river; JM), were used to explore the self-purification of surface water by bacteria under different environmental conditions. The dominant bacterial community of OG and JM waters (both are Firmicutes and Proteobacteria) were isolated, cultured, and then used to carry out flocculation tests. Results showed that the flocculation ability of the dominant bacteria and extracellular polymeric substances (EPS) obtained from OG isolation was significantly greater than that from JM. Further examination illustrated that the main components of EPS were polysaccharides, which played an important role in improving the flocculation ability of bacteria. EPS from dominant cultural bacteria strains (OG1 and JM3) isolated from the two different sources lacked hydrophilic groups (e.g. COOH) and had a networked structure which are the main reasons to enhance the flocculation ability. The bacterial diversity and redundancy analysis (RDA) results also showed that microbial community composition is determined by water quality (SS, TOC, and NH4+), and different Bacteroidetes, Actinobacteria and Proteobacteria community structures can improve the water body’s ability to remove environmental pollutants (such as SS, humic acid and fulvic acid). These findings provide new information showing how bacterial communities change with environmental factors while maintaining the purity of surface water.

Reactions between chlorine disinfectants, total organic carbon (TOC), and other chemicals in water form a series of disinfection by-products (DBPs), including trihalomethanes (THMs) that are toxic and suspected carcinogens. This paper aims at reducing DBPs formation potential through the degradation of the precursors using pre-oxidation. First, a survey analysis for five different water treatment plants (WTPs) was carried out to determine the most polluted site with TOC and THMs afterward, the efficiency of three different oxidants (potassium peroxy-mono-sulfate, potassium permanganate, and hydrogen peroxide) was tested under different conditions of pH, oxidant concentration and contact time. Optimum values for the mentioned conditions were used to achieve the maximum reduction for THMs in Mostorod-WTP which recorded the highest concentration of TOC and THM. THMs reduction efficiency of 54%, 67%, and 99% was achieved by using potassium peroxy-mono-sulfate, potassium permanganate, and hydrogen peroxide, respectively. In conclusion, hydrogen peroxide was the best in reducing THMs.

This study aims to investigate thermodynamic mechanisms of filtration behaviors of ultrafiltration (UF) process with polyacrylamide (PAM) flocculation for surface water treatment, which has not been investigated previously. It was interestingly found that, filtration of durably mixed sodium alginate (SA) solution corresponded to an extraordinarily high specific filtration resistance (SFR) (3.28 × 1014 m·kg−1 without polyacrylamide addition) and a V-shaped profile of SFR characterized by a sharp fall followed by a correspondingly sharp rise along with the increase in PAM addition concentration. Experimental characterizations suggested that, membrane fouling was mainly caused by the gel layer formation rather than the pore clogging and cake/floc formation. Rather than the chemical composition change, the changes of the solution physicochemical properties (pH and zeta potential) and foulant morphology are associated with above-mentioned interesting filtration behaviors. Accordingly, the thermodynamic mechanisms of the filtration behaviors were proposed. It was proposed that, the thermodynamics of polymeric network described by the Flory-Huggins lattice theory were responsible for the extraordinarily high SFR of SA gel layer. Low dosage of PAM addition decreased the negative zeta potential and homogeneity of the gel system, causing the reduced SFR. In contrast, further PAM addition increased the negative zeta potential and homogeneity of the gel system, and then increased the SFR of the gel layer. These results reasonably explained the V-shaped profile of SFR. This study provided significant insights into the effects of PAM addition on ultrafiltration behaviors of alginate solution.

In this study, a mathematical model was developed to assess fouling as well as membrane regeneration in a pressurized, hollow-fiber membrane system for the treatment of highly turbid surface water using periodical cleaning by backwashing and forward flushing. The model was validated using experimental data of trans-membrane pressure obtained when filtering separately, a SiO2 solution, a mixed SiO2/sodium alginate (SA) solution, a mixed SiO2/bovin serum albumin (BSA) solution and a mixed SiO2/humic acid (HA). Experimental and theoretical studies highlighted the synergistic fouling effect between SiO2 simulating the colloidal particles and the different elements (HA, SA and BSA) simulating the natural organic matter. Protein fouling was mitigated when mixed with SiO2. While the highest fouling rate was obtained for mixed SiO2/SA solution, the majority of this fouling was removed by periodic cleaning. Moreover, mixed SiO2/HA solution showed also high fouling which was mainly irreversible.

This study aimed at the assessment of UV, UV/H2O2 and ozonation processes on the removal of 26 pharmaceutically active compounds (PhACs) from a membrane distillation (MD) surface water concentrate. Furthermore, environmental and human health risk assessment were carried out considering acute and chronic risks, in addition to the genotoxic and carcinogenic effect over human health upon exposure. PhACs rejection by MD was >99% at 80% recovery rate. Besides PhACs rejection, MD was able to reject solids and other ions. Regarding the PhACs degradation in the concentrate, an increase in efficiencies were observed for UV/H2O2 and ozonation while increasing hydrogen peroxide dosage or ozone flow rate, respectively, achieving efficiencies up to 99.9%. Prednisone, Atorvastatin and Clarithromycin, considered the most insoluble PhACs among all, presented the lowest kinetic constants. Furthermore, these advanced oxidative processes (AOPs) were capable to effectively reduce the effluent color, total nitrogen and total organic carbon. Lastly, the surface water was subject to high toxicological risk. After the concentrate treatment by AOPs, acute and chronic effects were reduced while increasing H2O2 and O3 dosage in the UV/H2O2 and ozonation process.

Although surface water treatment presents a good solution for pollutants in rivers and freshwater lakes, the purification process itself presents a great threat to the aquatic environment through aluminum waste disposal. Recent studies have introduced coagulants recovery from treatment sludge as a green solution for waste handling and cost reduction. This article aims to evaluate repeated aluminum coagulants recovery from sludge using sulfuric acid. The waste from El-Sheikh Zaid Water Treatment Plant (ESZ-WTP) was characterized, then sequential coagulants recovery using optimum conditions was conducted. In addition, treated water was analyzed to determine the efficiency of the obtained coagulants and their influence on treated water quality. Sequential coagulants recovery using acidification revealed that no metals accumulation took place in the produced coagulants until the third recovery from ESZ-WTP sludge. On the other hand, a noticeable increase in trihalomethanes was detected in the treated water, especially using the third recovered coagulant. In conclusion, sequential coagulants recovery and usage in water treatment is an attractive alternative for single-use original coagulant in ESZ-WTP but for no more than three sequential recoveries. It is advisable to apply a fresh coagulant every three sequential recoveries to enrich the aluminum content and regenerate the sludge before restarting the recovery process.

The aim of this study was to analyze the presence and concentration of selected polycyclic aromatic hydrocarbons in water samples from different stages of treatment and to verify the usefulness of semipermeable membrane devices for analysis of drinking water. For this purpose, study was conducted for a period of 5 months. Semipermeable membrane devices were deployed in a surface water treatment plant located in Lower Silesia (Poland). To determine the effect of water treatment on concentration of PAHs, three sampling places were chosen: raw water input, stream of water just before disinfection and treated water output. After each month of sampling SPMDs were changed for fresh ones and prepared for further analysis. Concentrations of fifteen polycyclic aromatic hydrocarbons were determined by high performance liquid chromatography (HPLC). Presented study indicates that the use of semipermeable membrane devices can be an effective tool for the analysis of aquatic environment, including monitoring of drinking water, where organic micropollutants are present at very low concentrations.

This study examined the formation of disinfection by-products (DBPs), including nitrogenous DBPs, haloacetonitriles (HANs), and carbonaceous DBPs, trihalomethanes (THMs), upon chlorination of water samples collected from a conventional Chinese surface water treatment plant (i.e. applying coagulation, sedimentation, and filtration). Reductions in the average concentrations (and range, shown in brackets) of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) from 4.8 (3.0-7.3) μg/L and 0.52 (0.20-0.81) μg/L in 2010 to 2.4 (1.4-3.7) μg/L and 0.17 (0.11-0.31) μg/L in 2012, respectively, led to a decrease in HANs and THMs from 5.3 and 28.5 μg/L initially to 0.85 and 8.2 μg/L, as average concentrations, respectively. The bromide concentration in the source water also decreased from 2010 to 2012, but the bromine incorporation factor (BIF) for the THMs did not change significantly; however, for HAN the BIFs increased because the reduction in DON was higher than that of bromide. There was good linear relationship between DOC and THM concentrations, but not between DON and HANs.

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.

A series jar test was conducted to study the impact of dosing sequence and solution pH on coagulation and flocs properties by dual-coagulants of polyaluminum chloride (PAC) and compound bioflocculant (CBF) in low temperature surface water treatment. The results showed that DOC removal could be improved when CBF was used, especially by CBF–PAC (CBF dosed first). And both of the maximum DOC and UV 254 removal were achieved at pH6. Moreover, the flocs size and growth rate were enhanced significantly when dual-coagulants were used, while flocs strength and flocs dimension decreased. The recovery ability of flocs was improved when PAC–CBF was used, but decreased in condition of CBF–PAC. And recovery ability decreased as pH increased, while flocs were more compact as pH increased.

In the 1980s, a case-control epidemiologic study was conducted in Iowa (USA) to analyze the association between exposure to disinfection by-products (DBPs) and bladder cancer risk. Trihalomethanes (THMs), the most commonly measured and dominant class of DBPs in drinking water, served as a primary metric and surrogate for the full DBP mixture. Average THM exposure was calculated, based on rough estimates of past levels in Iowa. To reduce misclassification, a follow-up study was undertaken to improve estimates of past THM levels and to re-evaluate their association with cancer risk. In addition, the risk associated with haloacetic acids, another class of DBPs, was examined. In the original analysis, surface water treatment plants were assigned one of two possible THM levels depending on the point of chlorination. The re-assessment considered each utility treating surface or groundwater on a case-by-case basis. Multiple treatment/disinfection scenarios and water quality parameters were considered with actual DBP measurements to develop estimates of past levels. The highest annual average THM level in the re-analysis was 156μg/L compared to 74μg/L for the original analysis. This allowed the analysis of subjects exposed at higher levels (>96μg/L). The re-analysis established a new approach, based on case studies and an understanding of the water quality and operational parameters that impact DBP formation, for determining historical exposure.

The Surface Water Treatment Rule (SWTR) specifies the Ct (disinfectant concentration×time) calculation as the means by which disinfection efficacy, and therefore compliance, is determined. Baffle factors are used to scale the theoretical residence time of the water in a vessel to obtain the amount of time used for the Ct calculation. The baffle factor formulation has been left to guidance and has been a topic of discussion. In this work, an extended baffle factor formulation is developed using disinfection contact system performance models that incorporate the methods imposed by and built into the SWTR. The performance models are based on chemical reactor analyses that have been validated extensively in the literature. A comparison made between the extended baffle factor formulation and methods that use hydraulic considerations alone shows that failing to account for the entire residence time distribution and disinfection kinetics can lead to significant errors. The result of this work is a baffle...

The preparation and application of polyurethane immobilized nitrifying bacteria pellets for surface water treatment was studied. The removal of ammonia nitrogen from micro-polluted source water by polyurethane immobilized nitrobacteria pellets with a stuffing ratio of 10% in volume in an up-flow inner circulation reactor was investigated with the system operated continuously under the following conditions: temperature 20°C--30°C, DO 3--5 mg/L, and pH 7.1--7.3. The continuous removal rates of NH4+-N remain above 90% and4+-N concentration in the produced water was less than 0.5 mg/L with the hydraulic reaction time (HRT) controlled at 0.5 h. The results verified that polyurethane immobilized nitrobacteria pellets have a great potential for micro-polluted source water treatment applications.

The growth, breakage and regrowth nature of flocs formed by Titanium tetrachloride (TiCl 4 ) and polyaluminum chloride (PACl) was comparatively evaluated with surface water treatment. A series of jar experiments were conducted to investigate the impacts of different operating parameters such as shear force, solution pH and a breakage period on floc strength and re-aggregation potential. Results indicated that the responses of flocs to different operating parameters depend on the coagulant used. The ability of floc to resist breakage decreased with the increase of shear force and breakage period. Floc strength properties were also measured in response to increasing shear force, with the results suggesting that the order of floc strength was TiCl 4 > PACl. Floc regrowth of the two coagulants after exposure to high shear was limited, and flocs formed by TiCl 4 displayed weaker recoverability. The flocs generated in acid conditions were more recoverable than those generated in alkaline conditions no matter which coagulant was used.

The floc strength and regrowth properties of three polyferric-cationic polymer dual-coagulants were comparatively evaluated using surface water sample. The first dual-coagulant PFC-PD was prepared by premixing of polyferric chloride (PFC) and polydiallyldimethylammonium (PDADMAC) before dosing. The other two, PFCF (PFC dosed firstly) and PDF (PDADMAC dosed firstly), were achieved by dosing PFC and PDADMAC in different order. Floc strength properties were measured in response to increasing shear levels in the long period and high shear level in the short or long period. For the given optimum dose (3.0 mg L−1) and water pH (6.5) condition, the order of floc strength was PFCF > PDF > PFC-PD. The dual-coagulant which gave stronger flocs also gave a lower absolute value of zeta potential. The floc regrowth properties of all three dual-coagulants after short and long period high shear level were also investigated. The floc recoverability was in the following order: PFCF > PFC-PD > PDF.

The Henrico County VA Water Treatment Facility has been in operation since April 2004, making use of intermediate ozone for primary disinfection to take advantage of both the disinfection and DBP benefits. Since the summer of 2007 the staff at the Henrico WTF has embarked on an optimizing journey with their ozone system. This paper overviews the significant milestones accomplished on this journey as well as ongoing improvements. Optimizing efforts to reduce operating costs while achieving disinfection goals included: Staff training workshops; Automating ozone data collection and access; Operating system at optimum ozone concentration; Selecting optimum contactor sampling locations and number of contactors; Overcoming minimum gas flow limitations; Solenoid contactor sampling system issues and improvements; Disinfection calculation constraints; Excessive buildup of liquid oxygen (LOX) tank pressure. Each of these items is discussed following an overview of this 55 MGD surface water treatment facility.

Dissolved organic matters and ammonia nitrogen are serious contaminants of surface water in Taiwan. These contaminants can interfere with the water treatment process and cause biological instability in the finished water. One solution is to employ a biological treatment stage prior to the conventional water treatment process. A continuous flow biological filter packed with reticulated PU foam was used to remove ammonia nitrogen and organic materials before the conventional water treatment practice. The effect of its operation mode, namely, empty bed contact time (EBCT) and backwash, on the removal efficiencies of ammonia and organic matter was examined. The results suggested that ammonia nitrogen and organic nitrogen can be effectively removed by controlling the operation mode of the biological fixed bed. Efficient ammonia nitrogen removal was achieved upon the combination of the backwash mode with short EBCT or extended EBCT without the backwash. Efficient organic nitrogen and DOC removals were ...

In July 2003, the US Environmental Protection Agency (USEPA) published a proposed regulation, the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR), which included requirements pertaining to ultraviolet (UV) disinfection. In addition the USEPA released the proposed UV Disinfection Guidance Manual (UVDGM) that provides implementation guidelines for UV disinfection. Since July 2003, USEPA has revised several elements, which are also described. This paper summarizes proposed regulatory requirements in the United States (US) that pertain to disinfection of drinking water using UV light and the recommendations in USEPA's UVDGM. Although this paper does not provide the detailed UVDGM recommendations, it highlights important elements of the proposed regulation and guidance, including required UV doses, UV facility design and operation, and UV reactor validation. The US regulations and guidance do not directly affect the implementation of UV facilities in other countries; however, the information provided in this paper provides a different perspective for worldwide facilities and regulatory agencies to consider. Key words: ultraviolet, disinfection, regulations, guidance, UV facility design, validation, UV dose.

The U.S. Environmental Protection Agency currently recommends Ct (disinfectant concentration multiplied by the exposure time) values to achieve required levels of inactivation of Giardia lamblia cysts by different disinfectants including free chlorine. Current guidance covers inactivation levels in the pH range between 6 and 9. Subsequent to the publication of these criteria, studies on the inactivation kinetics of Giardia cysts by chlorine have been performed at pH levels greater than 9. It has been shown that the chlorine inactivation process for Giardia cysts is pH dependent. The objective of this paper is to extend the current Ct values for higher pH levels. The Chick-Watson first order kinetics model was used to develop Ct values for pH levels from 6 to 11.5. A formula is provided to calculate a 100(1 - alpha)% upper confidence bound for these values.

This study was intended to compare coagulation behavior and floc properties of two dual-coagulants polyaluminum chloride–compound bioflocculant (PAC–CBF) (PAC dose first) and compound bioflocculant–polyaluminum chloride (CBF–PAC) (CBF dose first) with those of PAC alone in low temperature drinking water treatment. Results showed that dual-coagulants could improve DOC removal efficiency from 30% up to 34%. Moreover, CBF contributed to the increase of floc size and growth rate, especially those of PAC–CBF were almost twice bigger than those of PAC. However, dual-coagulants formed looser and weaker flocs with lower breakage factors in which fractal dimension of PAC–CBF flocs was low which indicates a looser floc structure. The floc recovery ability was in the following order: PAC–CBF > PAC alone > CBF–PAC. The flocculation mechanism of PAC was charge neutralization and enmeshment, meanwhile the negatively charged CBF added absorption and bridging effect.

A study of concentration of bromates and THM has been made during a year on two surface water treatment plants which supply drinking water to the city of Paris. The concentrations of bromates and THM are always under die E.U guidelines, but the results on the two plants whose treatments are different (one physico-chemical, the other biological), depend on different parameters. Temperature seems to have a greater influence on the formation of bromate in the physico-chemical treatment. On the biological plant, slow sand filtration removes BDOC leading to a potentially higher formation of bromates. Concentrations of different THM are not significantly influenced by Br concentrations.

The Surface Water Treatment Rule and the Interim Enhanced Surface Water Treatment Rule classify some ground-water sources as “ground water under the direct influence of surface water” (GWUDI), and ground waters classified as GWUDI must follow the same treatment guidelines as surface-water sources. The microscopic particulate analysis (MPA) method is the most widely used method to identify GWUDI; however, this method has several deficiencies. An improved protocol for classifying ground-water sources as GWUDI is presented in this paper. The procedure consists of calculating the absolute risk of illness from waterborne \IGiardia\N and \ICryptosporidium\N in the pumped water, accounting for the uncertainty in the surface-water concentrations, hydrogeology, straining characteristics, pathogen viability in ground water, and observations of \IGiardia\N and \ICryptosporidium\N in samples of the pumped water. In cases where the risk of illness exceeds the acceptable risk, the ground water should be classified as GWUDI. Two examples are presented to illustrate the application of the proposed method.

The Surface Water Treatment Rule under the Safe Drinking Water Act and its amendments require that the water utilities maintain a detectable disinfectant residual throughout the distribution system...

The surface water treatment plants in Anglian Water are being upgraded in order to more reliably meet the requirements of the EEC Drinking Water Directive. Ozone and additional GAC filtration capacity are being installed at 11 waterworks treating river and reservoir water, with capacities ranging from 11 to 360 ML/d. The installations and reasons for the plant designs are discussed.

The Safe Drinking Water Act and its Amendments have imposed a large number of new regulations on the U.S. drinking-water industry. A major set of regulations currently under consideration will control disinfectants and disinfection by-products. Included in the development of these regulations is an Information Collection Rule and an Enhanced Surface Water Treatment Rule. These rules will require monitoring for microorganisms such as Giardia, Cryptosporidium, and viruses. Certain surface-water systems may be required to remove microbiological contaminants above levels currently required by the Surface Water Treatment Rule. Also included in these rules will be monitoring requirements for disinfection by-products and evaluation of pre-cursor removal technologies. As various regulations are promulgated, regulators and those associated with the drinking-water industry need to be cognizant of the potential impact of treatment to control one contaminant or group of contaminants on control of other contaminants. Compliance with drinking-water regulations mandated under the Safe Drinking Water Act and its amendments has been estimated to cost about $1.6 billion.

The U.S. Environmental Protection Agency (U.S. EPA) is currently attempting to balance the complex trade-off in chemical and microbial risk associated with controlling disinfection and disinfection by-products (D/DBP) in drinking water. In attempting to achieve this balance, the U.S. EPA will propose three rules: an information collection (ICR); an enhanced surface water treatment rule (ESWTR) and a two-stage D/DBP rule. Controlling D/DBP will have a major impact on drinking water utilities in the United States. There are several options for D/DBP control, including moving the point of disinfection, removal of by-products once they are found, removing precursor material or natural organic matter before it interacts with the disinfectant, or use of a disinfectant that minimizes the formation of by-products. The least-expensive approach to D/DBP control is to move the point of disinfection or the use of an alternative disinfectant. The least-desirable approach is to remove disinfection by-products once they are formed. Overall, the most effective approach to D/DBP control is to remove precursor before it reacts with the disinfectant. The choice of any given strategy is very site specific.

The U.S. EPA published the surface water treatment rule which imposed stringent requirements for disinfection. The rule is based on the C × T concept. The detention time T10 must be determined for each type of contactor by performing tracer tests. Those tests have been performed for various ozone contactors. The results were evaluated using two types of models. For a classical diffuser-bubble contactor the ratio T10/τ is about 0.5. For an industrial deep U-tube this ratio is equal to 0.55, but it reaches 0.9 for a pilot system. These results are indicating that a deep U–tube can provide a greater T10/τ ratio than a diffuser–bubble contactor.

Coagulation performance, mechanism of poly-aluminum-silicate-chloride (PASiC) and residual Al speciation in the effluent with respect to a specific surface water treatment in China were comprehensively investigated in this study. The impact of OH(-)/Al(3+) and Si/Al molar ratios on the coagulation performance, mechanism and residual Al speciation of PASiC in surface water treatment was discussed as a function of coagulant dosage. It was intended to provide an insight into the relationship between coagulation performance and residual Al. Experimental results revealed that when OH(-)/Al(3+) molar ratio = 2.00 and Si/Al molar ratio = 0.0500 in PASiC coagulant, PASiC exhibited beneficial coagulation property and relatively lower content of residual Al. Surface bridging and entrapment was more effective compared with charge neutralization during the specific surface water treatment. The majority of residual Al in the effluent existed in the form of insoluble suspended or particulate Al. Dissolved organically bound Al was almost the major speciation in dissolved Al and dissolved inorganically bound monomeric Al was the only component in dissolved monomeric Al. Al in PASiC remained abundant at lower dosages and residual Al concentration could be effectively reduced at the dosages of 12.0-15.0mg/L as Al.

Preozonation facilities were installed at the Los Angeles Aqueduct Filtration Plant originally to enhance coagulation assistance (microflocculation). The Surface Water Treatment Rule will amend this primary purpose to meeting disinfection standards. Additional ozone generation equipment and a revised ozone system operating strategy will be required to accomplish these changed objectives. The topics discussed in this paper are the considerations surrounding the development of a successful, cost-effective operating strategy. The strategy proposed herein was based on data collected between January and July 1991. On-line process monitoring plans and automated system control logic are described.

The U.S. Environmental Protection Agency (EPA) has recently promulgated drinking water regulations known as the surface water treatment rule (SWTR) to control viruses, \IGiardia lamblia, Legionella\N, and heterotrophic bacteria. The SWTR specifies overall minimum removal and inactivation efficiencies by filtration and disinfection for \IGiardia lamblia\N and viruses. The \ICT\N concept is used to predict inactivation efficiencies. \ICT\N stands for the product of characteristic exposure time (\IT\N) and the characteristic concentration (\IC\N) of the disinfectant in the disinfection chamber. This paper presents an analysis of ways to characterize ozone concentration in water disinfection systems for the purpose of calculating ozone inactivation efficiencies. Guidelines to predict the characteristic (or average) ozone concentration are developed for four types of ozone reactors, including rigorously mixed systems, cocurrent and countercurrent contractors, and flow segments (i.e., where no ozone gas is introduced but where residuals in a water phase remains).

The U.S. Environmental Protection Agency has recently promulgated drinking‐water regulations, known as the surface water treatment rule (SWTR), to control viruses, Giardia cysts, Legionella, and heterotrophic bacteria. The SWTR specifies overall minimum removal/inactivation efficiencies by filtration and disinfection for Giardia lamblia and viruses and uses the CT concept to predict in‐activation efficiencies. CT stands for the product of characteristic exposure time (T) and the characteristic concentration (C) in the disinfection chamber. This paper evaluates possible methods to determine the characteristic exposure time for ozone disinfection. The extent to which different measures of T (such as the hydraulic retention time, T10 and T50) actually ensure compliance with the required level of inactivation is evaluated by using segregated flow analysis and classical residence time distribution models. The analysis indicates that T10, the minimum exposure time of 90% of the water in the disinfection unit, i...

Basedon the success of the first Hungarian large capacity drinking water treatment ozonation plant of Budapest that was put into operation in 1984, a similar second plant was put into operation in 1988 in Debrecen with 150,000 inhabitants. This recently built plant solves taste and odor problems and water quality development of a surface water treatment plant with a capacity of 50,000 m3/day that is operative for a longer period of time. The experiences gained at the Budapest ozonizing plant were utilized during both planning and construction. Thus, for example, the method of ozone absorption had been modified. The in-situ repair of the Frings turbines for ozone contacting placed at the Rackeve plant of the Budapest Waterworks will be introduced, as well as a concept of a newer kind of ozone mixing.

Under the auspices of the Safe Drinking Water Act (SDWA) the U.S. EPA has promulgated the Surface Water Treatment Rule (SWTR) requiring public water systems using surface water to provide minimum disinfection to control \IGiardia lamblia,\N enteric viruses, and bacteria. The \IC\N·\N\It\N concept (concentration of disinfectant in mg/L times time in minutes) is used to establish the appropriate criteria for a surface system to achieve at least 99.9% inactivation of \IGiardia lamblia\N and 99.9% inactivation for viruses. In the SWTR, an empirical equation was developed based on water temperature, pH, concentration of chlorine, and inactivation level to predict required disinfection criteria (\IC\N·\N\It\N values). This paper describes the development of an equation based on Chick-Watson kinetics that provides equivalent information but is theoretically more consistent.

Hom's model for microbial disinfection kinetics is frequently applied to data showing deviations from Chick's law inactivation. However, the generally applied form of this model does not consider the possibility for disinfectant decay/demand. In this work, we derive the form of the Hom model under conditions of first-order demand; the integrated solution involves the incomplete γ function. We then propose a simpler approximation to this exact solution and explore its numerical adequacy, also showing the effect of the approximation when applied to a real data set. This approach can be used to assess disinfection kinetics in drinking water to insure compliance with microbial reductions required under the Surface Water Treatment Rule

After reviewing the uses of ozone in the preparation of drinking water, high purity water for Pharmaceuticals industries, and swimming pools throughout Belgium, a discussion of technological developments made at the Tailfer plant (serving Brussels) concerning the uses of ozone is presented. These subjects include analytical and monitoring techniques developed for ozone, procedures for ozone contacting employed at this plant, treatment of ozone contactor off–gases, and the use of oxygen–enriched process gas to produce supplemental amounts of ozone required periodically. Capital and operating cost data are presented.

A four month study was carried out at the Buffalo Pound Water Treatment Plant near Regina, Saskatchewan to examine the formation and removal of volatile organic compounds. Nine volatile organics were found to be consistently formed or added to the water during full scale conventional treatment. Only the chlorine-containing trihalomethanes were present at levels greater than 1 ug/L. Removal of these compounds was investigated in pilot scale granular activated carbon post contactors; the study examined both fresh carbon and carbon which had been used in a previous four month investigation. All compounds were removed to some degree on the carbon. The location of removal within the columns varied with the different compounds and the results suggested formation of some compounds within the columns. Post chlorination of column effluent resulted in at most a modest increase in the concentrations of the organic compounds.

Because organic micropollutants (MP) are frequently detected in river waters that are used as drinking water sources, combining a relatively cost-efficient natural treatment with upstream advanced oxidation processes (AOP) appears promising for their efficient abatement. Such a multi-barrier system can be integrated in drinking water production schemes to minimize risks from potentially hazardous MPs. This study investigates the impact of an UV/H2O2 AOP before soil aquifer treatment (SAT) on the abatement of selected MPs (EDTA, acesulfame, iopamidol, iomeprol, metformin, 1H-benzotriazole, iopromide), dissolved organic matter (DOM) (apparent molecular size distribution, specific UV absorbance at 254 nm – SUVA) and microbial parameters (intact cell count, cell-bound ATP). A pilot plant consisting of an AOP (0.5 m3 h−1, 4 mg L−1 H2O2, 6000 J m−2) and two parallel soil columns (filtration velocity: 1 m d−1, column height: 1 m) was continuously operated over a period of 15 months with Rhine river water pre-treated with rapid sand filtration. The investigations revealed a shift towards longer retention times of the humic substances peak in LC analysis of DOM, lower SUVA and higher biodegradability of DOM after UV/H2O2 treatment. In addition, an overall higher abatement of all investigated MPs by the combined treatment was observed (AOP with subsequent SAT) compared to either process alone. This observation could be explained by an addition of the single treatment effects. The strong primary disinfection effect of the AOP was detectable along the first meter of infiltration, but did not lead to any change in the column performance (i.e., similar abatement of dissolved organic matter).