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Dissolved oxygen (DO) is strongly linked to the origin and transformation of dissolved organic matter (DOM) in reservoirs. During metalimnetic oxygen minimum (MOM), the reservoir is divided into four regions: surface oxygen-rich (SOR), middle anoxic (MA), middle oxygen (MO), and bottom anoxic (BA). This article focuses on the link between DOM and disinfection by-product (DBP) precursors and DO in reservoirs. The DOM in SOR was characterized by the highest proportion of protein-like components, lowest humification and aromaticity, which was indicated mainly affected by algae blooms. The DOM in MO was affected by terrestrial, with the highest ratio of humic and fulvic-like fluorescent and the highest extent of humification and aromaticity. The humification and aromaticity in MA and BA were between MO and SOR water. Moreover, according to redundancy analysis, the dominant DBPs, including trichloromethane and haloacetic acid precursors, mainly originate from a high degree of humification and aromaticity in DOM, suggesting that the terrestrial-derived DOM was a dominant source of DBP precursors. This study provides the distribution in DOM characteristics and its driven DBPs in the Sanhekou Reservoir during the MOM, which is of great significance for selecting appropriate water intake regions for subsequent water treatment. [ABSTRACT FROM AUTHOR]

Trihalomethanes (THMs) are one of the main disinfection by-products generated in drinking water (DW). To control health risks caused by THMs several countries have established a maximum content of these chemicals in DW. THMs can be removed by granular activated carbon (GAC) and their adsorption processes have been studied by different authors. However, there are few studies on their desorption from GAC and no data are available on their desorption at a full scale. This paper summarises the results obtained in the monitoring of the adsorption and desorption processes of THMs at a full-scale DW plant considering different types and stages of GACs, as well as several types of influent waters. This research was carried out during 3 years in a full-scale advanced DW plant (6.25 m³·h−1) that can use four different pre-oxidants. An increase on THMs concentration in the outlet of the AC filters due to desorption processes were checked, although the obtained doses were always far below the established European limit (100 μg/L). [ABSTRACT FROM AUTHOR]

Biological activated carbon filter backwash water (BAC FBW) removes pollutants from BAC filters in drinking water treatment plants. Characterizing the dissolved organic matter (DOM) in BAC FBW is of great significance for the recycling and treatment of backwash water. DOM pollution was monitored over a year using three-dimensional excitation-emission matrix fluorescence spectra. The dissolved organic carbon (DOC) concentration and fluorescence results showed that the DOC concentration reached the lowest value of 1.95 mg/L in the summer. The relative abundances of fluorescence components had a direct relationship with temperature variations. The soluble microbial products were enhanced greatly during cold seasons, while fulvic-acid-like and humic-acid-like compounds remained constant. Disinfection by-products (DBPs) formation potential and cytotoxicity were evaluated. The total haloacetonitriles (HANs), trihalomethanes (THMs), halonitromethanes (HNMs), and haloacetaldehyde (HALs) formation potentials ranged from 35.5 to 47.3 µg/L, 95.1 to 126 µg/L, 4.95 to 8.06 µg/L, and 43.4 to 53.0 µg/L in BAC FBW, respectively. Among all DBPs included in the calculation, the order of contribution to cytotoxicity was HANs.HALs.THMs.HNMs, respectively. Especially, HANs were much higher than the other DBPs, which should be controlled to avoid the biological risk of effluent quality. [ABSTRACT FROM AUTHOR]

In recent years, the contribution of bacterial materials in water distribution systems to DBPs has attracted widespread attention from researchers. The risks and influencing factors of bacterial DBPs are reviewed. Factors affecting the generation of bacterial DBPs include the characteristics of bacterial materials, disinfection process, piping materials, and water quality. Among the major components of biofilms, proteins or amino acids have the greatest risk of DBPs. Among the commonly used disinfection methods, chlorine is more suitable for continuous disinfection of pipe networks than chloramine, but chlorine dioxide may be a better substitute in the future. Pipes with good biological stability, such as polyethylene (PE) pipe, should be encouraged to be used in water supply networks. Periodic removal of biofilms, reduction of organic matter and bromide ion concentrations, and maintenance of high flow rates are effective means to reduce bacterial DBPs. The control, removal and monitoring devices of tube wall biofilm need to be further developed and promoted. In the future, it is urgent to develop new disinfectants that are not easy to react with biomolecules and natural organic matter, and produce fewer or no by-products. [ABSTRACT FROM AUTHOR]

Controlling the formation of disinfection by-products (DBPs) is a major issue in the drinking water industry, and understanding the characteristics of DBP precursors in treatment processes for micro-polluted raw water is key to improving water quality. In this study, a sampling program was undertaken to investigate the fate of dissolved organicmatter (DOM) and the characteristics of DBP precursors in a pilot constructed wetland imitating the Yanlong Lake ecological project. Using XAD resin adsorption and ultrafiltration techniques, the dissolved organic carbon, UV254, and DBP formation potential (DBPFP) were measured in different DOM fractions in raw water and wetland effluents. After the constructed wetland treatment, the low molecular weight fraction (<3 kDa) of DOM and DBPFP generally showed a decreasing trend along the water path, while the high molecular weight fraction (>3 kDa) of DOM increased. The specific DBPFP (SDBPFP) was much higher in the <1 kDa fraction than in the other fractions. Although the hydrophobic fraction of DOM was the most abundant in all stages of the wetland treatment, the SDBPFP of the hydrophilic fraction was higher than that of the hydrophobic fraction. Furthermore, compared with raw water, the DOC, UV254 and DBPFP in the treated wetland effluents increased; however, all of the chemical DOM fractions exhibited decreased SDBPFP in accordance with a decrease in the specific ultraviolet absorbance during wetland treatment. These conclusions indicate that the DOM produced by the wetland system may generate DBPs less readily compared with the DOM of raw water. [ABSTRACT FROM AUTHOR]

Nitrogen-containing organic compounds and nitrogenous disinfection by-products (N-DBPs) in drinking water have attracted attention in the field of water treatment. Metabolites released during algae growth contain a variety of organic nitrogen species, which are called N-DBP precursors. The aim of this paper is to elucidate how N-DBP precursors are released under UV radiation, as well as investigate the variations of their chemical properties. The results show that through UV radiation, the physiological metabolism of algal cells was disordered and the properties of their metabolites were changed. The dissolved organic nitrogen (DON) compound concentration increased rapidly from 5.38 at the beginning to 11.11 mg/L after 30 min of radiation, and then increased steadily from 11.11 to 23.71 mg/L during a further 210 min of radiation. Derivation results of the curves for algae and DON concentration variations shows that when 1 x 1010 algal cells were destroyed, 8.31 mg DON was released into the solution during the first 30 min of radiation. Low dose UV radiation brought a slight decline of the specific N-DBP formation potential due to changes in the extracellular organic matter (EOM) structure without destroying the algal cells, which was conducive to controlling the formation potential of N-DBPs. Long-time UV radiation can bring a significant increase in N-DBP formation potential. After 4 hours of ultraviolet radiation, the total formation potential of N-DBPs in the solution increased from about 84.9 μg/L to about 213.5 μg/L, 2.5 times higher than the initial solution. The N-DBP formation potential increases obviously during the first 10-30 min UV radiation, and then decreases slightly in the subsequent 30-240 min radiation. [ABSTRACT FROM AUTHOR]

Iopamidol (an iodinated X-ray contrast medium) and bromide are precursors in the formation of halogenated disinfection byproducts (DBPs). The interactions of these precursors are vital to elucidate the formation of halogenated DBPs during chloramination. This work investigated the formation of total organic halogen and select individual DBPs in two laboratory-chloraminated source waters containing iopamidol and bromide. Experiments were carried out in batch reactors containing Barberton source water (BSW) and Cleveland BSW (CSW), spiked with iopamidol (5 µM), bromide (15 µM), and 100 µM monochloramine. Total organic iodine concentrations were approximately equal regardless of source water since they are mostly unreacted iopamidol and iopamidol DBPs. Almost equal amounts of total organic chlorine (3-4 nM) were produced in the source waters, but higher quantities of total organic bromine were formed in BSW than CSW. Substantial quantities of regulated trihalomethanes (THMs) and haloacetic acids (HAAs) were formed in the source waters, along with appreciable concentrations of iodinated trihalomethanes (CHBrClI, CHCl2I, and CHBr2I). Low concentrations of iodo-HAAs were detected, especially at low pH. Overall, bromide concentrations appeared to suppress iodo-DBP formation during chloramination of iopamidol in the presence of natural organic matter. A good correlation (R²= 0.801) between the yields of regulated DBPs and iodo-DBPs was observed. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) causes organic pollution in lakes, resulting in the occurrence of off-flavour etc. when lake water is used as a drinking water source. In this study, DOM in 11 major lakes in Japan was characterised by high-resolution Orbitrap mass spectrometry. Molecular formulas were assigned to 845-1,451 components per sample. Among them, 555 components were commonly found in all lakes. The DOM compositions of the 11 lakes were clustered into four groups. Correlation analysis could extract specific components whose relative intensities were associated with water quality indices such as specific ultraviolet absorbance, specific dissolved chemical oxygen demand (DCODMn), and specific trihalomethane formation potential (R= 0.80-0.93, p<0.05). Although further molecular structural analyses of DOM components are necessary, these results could be informative for exploring key candidates related to specific water quality issues. Pretreatment of samples with permanganate oxidation was applied to screen components which could contribute to DCODMn. DCODMn components accounted for only 7-30% of total peak intensities, indicating the limited performance of permanganate oxidation. Pre-treatment by permanganate coupled with Orbitrap MS revealed that components with higher molecular weight, higher oxygen-tocarbon ratios (O/C), and lower hydrogen-to-carbon ratios (H/C) could be responsible for DCODMn. [ABSTRACT FROM AUTHOR]

Seawater is a valuable water resource in coastal regions. However, during seawater chlorination, a group of halophenols (HPs) may be formed. These HPs have lower odor and taste detection thresholds than other disinfection by-products (DBPs), however these are usually more toxic than most of the abundantly detected DBPs. Hence, an effective approach for control of HP formation during seawater chlorination is required to minimize highly toxic HP formation. Pretreatment using TiO2 photocatalysis was applied in this study to assess its ability for removal of HP precursors. Seawater samples with external addition of 1 mg/L phenol were spiked with TiO2 from 0.1 to 10.0 g/L and exposed under UV light for 2 to 120 min. The UV absorbance at 254 nm and the excitation- emission matrix fluorescence of dissolved organic matter were measured for each treated sample. It was observed that the optimal treatment condition to achieve the highest UV254 removal was 4.0 g/L TiO2 with UV exposure of 30 min. By pretreatment using this method and stated dose and exposure, only two types of HPs were detected during chlorination, compared with four types of HPs formed in the untreated samples. Moreover, the pretreatment greatly reduced the concentration of 2,4,6-TBP from more than 400 μg/L to less than 1 μg/L. The significance of this research study is to identify the effectiveness of UV/TiO2 in reducing DBP formation by analyzing the mechanisms during the process, which indicates the use of UV/TiO2 pretreatment for control of HP formation in seawater during chlorination. [ABSTRACT FROM AUTHOR]

Certain aspects of the distribution of disinfection by-products (DBPs) in the air of indoor swimming pools, the exposure of the users, and possible health effects, have not been well documented. To determine the distribution of trihalomethanes (THMs), measurements were performed at 0.05 m, 0.60 m and 1.50 m above the water surface. These heights were chosen to measure the exposure in the breathing zone of the users. Air samples were collected from two indoor swimming pool facilities in Norway. Facility 1 uses calcium hypochlorite and facility 2 uses sodium hypochlorite for water treatment. In facility 2, one of the swimming pools is filled with 33% seawater, while the other pools in this study were filled with freshwater. Higher values were measured at 0.05 m compared to 1.50 m. Negligible differences between the measurements at 0.60 m and 1.50 m above floor levels were obtained. On average, 282% higher concentrations of total THM (tTHM) were measured in facility 2. Different disinfection products and ventilation concepts are possible explanations. Swimmers are exposed to higher concentrations compared to users by the poolside. For future studies, it is crucial to measure as close to the water surface as possible [ABSTRACT FROM AUTHOR]

Invertebrate removal by traditional biological activated carbon (tra-BAC) and pre-BAC treatment processes was investigated in a full-scale water treatment plant. The results showed that invertebrate reproduction occurred in both BAC filters, but the invertebrate abundance in the finished water processed by tra-BAC was about 15 times greater than that processed using the pre-BAC process. In the pre-BAC process, the sand filter was placed after the BAC filter, and sand filtration removed most of the invertebrates, with an average removal efficiency of 91.1%. However, the pre-BAC filter, which was positioned behind the sedimentation tank, needed to be backwashed more frequently than the tra-BAC filter because of the high turbidity of the inlet water. The frequent backwashing reduced the biomass on the activated carbon and decreased the invertebrate reproductive rate. The results of this study are helpful for evaluating the pre-BAC treatment process in drinking water treatment plants. [ABSTRACT FROM AUTHOR]

Advanced reduction processes (ARPs) are treatment processes that involve combining reducing reagents and activating tools to produce highly reactive reducing free radicals. The process has proven effective for treating oxidized contaminants, and the effects of process variables on the degradation kinetics of various target contaminants have been investigated in our previous studies. In natural environments, natural organic matter (NOM) is found in surface or ground water. NOM absorbs UV light and can react with photochemically produced radicals, thus affecting target contaminant photochemical reactions and further influencing the efficiency of ARP. This study examines the impact of humic acid (HA) and Suwanee River NOM on bromate reduction rates with UV irradiation using a low-pressure mercury UV lamp. The effects of the sulfite dose, solution pH, and light intensity are studied and the pseudo-first-order rate constants in the presence of HA (kobs,HA) are compared to those observed in the absence of HA (kobs). At low HA concentrations of 1 mg L-1, kobs,HA was larger than kobs; however, kobs,HA was less than kobs at higher HA concentrations. Furthermore, kobs,HA did not increase with increasing sulfite doses in the presence of HA, which is unlike the behavior of kobs. [ABSTRACT FROM AUTHOR]

The objectives of this pilot-scale study were to optimize backwash frequency and empty bed contact time (EBCT) of biofilters treating ozonated surface water from Lake Ontario. Performance was benchmarked in terms of the reduction of turbidity, dissolved organic carbon (DOC), disinfection by-product (DBP) precursors, and ultrafiltration foulants (biopolymers). Increasing the EBCT from 4 to 8 min resulted in a higher reduction of DOC (5%), trihalomethane (THM4) and haloacetic acid (HAA9) precursors (~12%) without negatively impacting effluent turbidity (consistently below 0.4 NTU), while biopolymer removal remained unaffected (2%). The impact of varying backwash frequency (5, 10, and 25 day intervals) was also compared for biofilters operated at an EBCT of 4 min. Results showed no impact of extended run times (up to 25 days) on DOC or DBP precursor removal; however turbidity removal was affected beyond 15 days of operation. Backwashing biofilters at 10 vs 5 day intervals would result in a reduction of backwash water, energy consumption and amount to nearly $17,000 in savings for the utility. [ABSTRACT FROM AUTHOR]

The study attempted to determine the hydraulic retention time (HRT) required for soil aquifer treatment (SAT) to reclaim water as potable water in an aspect of controlling disinfection byproduct (DBP) precursors. In order to evaluate the removal of DBP precursors, the uniform formation condition was used to estimate the formations of trihalomethanes (THMs) and haloacetic acids (HAAs). Effluent water from anaerobic-anoxic-oxic processes (A2O water) was fed through soil columns at different HRTs. Sand with low organic content and less specific surface area was selected to represent the 'worst available case' of subsurface environment in Japan. Overall, annual data (n ≥ 14) indicated that the average concentrations of THMs and HAAs for water passed through SAT with HRT less than 7 days were below the standard of drinking water. However, risks of exposure to THMs and HAAs were observed. Increasing HRT to 30 days resulted in the concentrations of regulated THM and HAA species lower than the 10% of the drinking water standard values, except for dichlorobromoform. Therefore, a treatment unit for bromide ion removal (e.g., anion exchanger) prior to chlorination is recommended to lower the risk levels of exposure to dichlorobromoform. [ABSTRACT FROM AUTHOR]

2014 marks the 40th anniversary of the seminal discovery by Johannes Rook, in 1974, that trihalomethanes (THMs) were formed by the chlorination of natural organic matter (NOM) in drinking water. Since this discovery, which revolutionized how we viewed drinking water safety and quality, hundreds of other classes of disinfection by-products (DBPs) have been discovered. The finding in 1976 by the US National Cancer institute that chloroform, the dominant THM, was a rodent carcinogen spurred a large number of epidemiology and toxicology studies into chlorinated drinking water, in 1985, this cancer finding was shown to be wrong. We should now be asking: What do we know about the human health impacts of DBPs in drinking water? Bladder cancer has been the most consistent finding from epidemiologic studies in North America and Europe and the possibility that chlorinated drinking water contributes an increased risk of bladder cancer remains a viable hypothesis. Despite some recent improvements in exposure assessments to focus on inhalation and dermal exposures rather than ingestion, no causal agent with sufficient carcinogenic potency has been identified, nor has a mechanistic model been validated. Consequently, a sensible precautionary approach to managing DBPs remains the only viable option based on four decades of evidence. [ABSTRACT FROM AUTHOR]

Formation of disinfection by-products (DBPs), including dichloroacetonitrile (DCAN), trichloroacetonitrile (TCAN), chloroform (TCM), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), chloropicrin (TCNM) and chloral hydrate (CH), from monochloramination of chironomid larvae was investigated at different contact times, pH levels and temperatures. Increased monochloramine dosage and prolonged reaction time resulted in an increase in most DBPs. Furthermore, the concentrations of TCAN, DCAN and CH initially increased over time before reaching a plateau. This is because of the hydrolysis of functional groups and the function of NH2Cl. The concentrations of DCAA, TCAA and TCM decreased as pH was increased from 5 to 10, and TCAN, DCAN and CH were not detected when the pH exceeded 8. As for TCNM, their concentration increased as the pH increased from 5 to 7, following a subsequent decrease at higher pH values. High temperatures led to higher DCAN and TCAN concentrations, while low temperatures resulted in higher TCNM and DCAA concentrations. Both high and low temperatures reduced the concentrations of TCAN and CH. Finally, concentrations of the four predominant DBPs (TCM, DCAN of DCAA and TCAA) all decreased as Cl/N ratio declined. [ABSTRACT FROM AUTHOR]

A pilot-scale study was conducted to evaluate the impact of several biofiltration enhancement strategies in terms of organic removal to reduce disinfection by-product (DBP) formation potential and mitigate ultrafiltration (UF) fouling. Strategies included nutrient addition (nitrogen and phosphorus) to optimize metabolic degradation of organics, use of hydrogen peroxide (H2O2, peroxide) to improve filter run times, and the application of in-line aluminum sulphate (alum) for biopolymer removal. The impact of media type on performance was also examined (anthracite versus granular activated carbon (GAC)). Passive biofiltration (without enhancement) reduced dissolved organic carbon (~5%), biopolymers (~20%), and trihalomethane and haloacetic acid precursors (~20% and ~12%, respectively) while mitigating UF irreversible fouling (~60%). Nutrient addition was not observed to enhance biological performance. Addition of 0.5 mg/L hydrogen peroxide decreased head loss by up to 45% without affecting organic removal; however at a dosage of 1 mg/L, it negatively impacted both UF fouling and DBP precursor removal. In-line alum addition prior to biofiltration (<0.5 mg/L) improved UF fouling control by up to 40%, without sacrificing head loss. Overall, GAC provided superior performance when compared to anthracite. [ABSTRACT FROM AUTHOR]

Water disinfection usually requires expensive chemicals or equipment. Chlorination is a common disinfection method, although it is not able to inactivate all pathogens. High concentrations of residual chlorine also cause an unpleasant taste and smell in drinking water. As an alternative, photocatalysis and photoelectrochemical treatment has a high disinfection potential in drinking water by using solid catalysts, such as titanium dioxide. Highly reactive hydroxyl radical generated during the process serves as the main oxidant, capable of inactivating a wide range of microorganisms. In this study, we proposed a novel comparison between Gram-positive and gramnegative microorganisms. An immobilized TiO2 film promoted higher efficiency in water disinfection processes. The treatment effectively inactivated Escherichia coli and Staphylococcus aureus bacterial microorganisms in a shorter period than other alternative methods. [ABSTRACT FROM AUTHOR]

A series of column experiments and risk evaluation showed that preozonation was a better option to enhance the performance of soil aquifer treatment (SAT) than ozonation after SAT with respect to dissolved organic carbon, trace organic contaminants, and disinfection byproducts. This is a good example to show that upgrading pretreatments can be more effective than adding extra treatments after SAT, and that it is important to optimize a water reclamation system as a whole system. [ABSTRACT FROM AUTHOR]

In this study the influence of water matrix and oxidation treatment by ozone on natural organic matter (NOM) fractionation and corresponding disinfection by-products formation was investigated. Three water types were selected, based on their different NOM contents (5.16-9.85 mg/L dissolved organic carbon (DOC)) and structures (42-79% proportion of hydrophobic NOM fraction). It was determined that increasing the ozone dose (0.2-0.8 mg O3/mg DOC) generally led to reductions in DOC (2-26%) and trihalomethane formation potential values (4-58%). Results of NOM fractionation showed that the reactivity of all the individual NOM fractions towards trihalomethane formation decreased after ozone oxidation (0.8 mg O3/mg DOC) by 47-69%, relative to the raw waters. [ABSTRACT FROM AUTHOR]

The presence of N-nitrosamines in water bodies used for drinking water purposes may present a more serious risk for humans than regulated disinfection by-products (DBPs) species. Hence, understanding and controlling the incidence of N-nitrosamines represents a contemporary challenge to the water industry. Although many of these molecules potentially formed as DBPs are detected in chlorinated natural waters, few studies have focused on the formation, occurrence, and analysis of N-nitrosamines. Until now, nine N-nitrosamines have been detected in water samples; Nnitrosodimethylamine is the most frequently reported nitrosamine in drinking water. Although there are currently no federal regulations for these molecules in drinking water, this family of N-DBPs is one of three potential groups of contaminants highlighted for possible regulatory action in the near future. This paper gives an overview of the current knowledge concerning the occurrence, precursors, and formation mechanisms of N-nitrosamines in water. In addition, the existing regulations are described and relevant analytical methods used for their quantification in water samples are also discussed. [ABSTRACT FROM AUTHOR]

Over the past several decades, much research has been carried out to understand and control the formation of disinfection byproducts (DBPs) of potential human health concern in drinking water. The majority of these studies have taken place in continental climates of North America and Europe, with less work investigating waters in tropical and subtropical climates. This study evaluated the occurrence, precursors and formation potentials of a range of DBPs across nine water treatment plants (WTPs) in South East Queensland, Australia. Average total organic nitrogen concentrations in raw and final waters were 0.35 and 0.15 mg N/L, respectively, and total organic carbon levels were 9.2 and 3.7 mg C/L in raw and final waters, respectively. DBP formation potential was lower on average in final waters of advanced compared to conventional WTPs, demonstrating the effectiveness of ozone/biological activated carbon (BAC) treatment at removing DBP precursors. While ozone on its own increased the formation potentials of chloral hydrate, halonitromethanes, and haloketones when followed by chlorination or chloramination, subsequent BAC treatment reduced the potential to produce these DBPs, except for tribromonitromethane. DBPs measured in the finished water leaving the WTPs were all below the Australian Drinking Water Guideline levels. [ABSTRACT FROM AUTHOR]

In this contribution, a compact reactor system is presented that enables efficient processing of grey water in order to facilitate its reutilization for flushing toilet bowls. The treatment of collected grey water is performed in combination with an aerobic/anoxic biological process carried out in a submersed bioreactor with immobilized biomass for the removal of dissolved organic substances, and a procedure of adjusting the concentration of microorganisms in the liquid phase by using a simple technique of flow-through ultraviolet-light based disinfection. In this system which operates at ambient temperature as a semi-continuous recycle reactor, significant removal of organic matter was achieved (conversions up to 65%, expressed as total organic carbon) without the occurrence of malodour. A low concentration of dispersed microorganisms was measured in treated grey water; importantly, no coliforms were accumulated in the unit. [ABSTRACT FROM AUTHOR]

Anion exchange resins (AERs) were compared with aluminum-based coagulants for reducing disinfection by-product (DBP) precursor concentrations from a source water collected in northeast Ohio, USA. Three AERs (IRA-910, IRA-958, and MIEX) were evaluated to determine which resin would remove the most natural organic matter (NOM) and moieties responsible for DBP formation. All the AERs were found to be highly proficient at NOM removal specifically the moieties that absorb UV254 (i.e., chromophores) over 75 min of contact time; however, MIEX removed NOM at a faster rate than IRA-910 and IRA-958 resins. Enhanced coagulation was effective at removing approximately 35% of the NOM and 40-60% of the chromophores and fluorophores (i.e., excitation-emission matrix pairs A and C). DBP formation was determined as a function of pH for the different NOM removal processes. MIEX treatment resulted in significant reduction in DBP concentrations when compared to chlorinating the raw source water. MIEX generally out-performed enhanced coagulation for reducing DBP formation. However, alum was found to remove more NOM and resulted in less DBPs compared to aluminum chlorohydrate. This could impact water utilities trying to balance the health effects due to DBP exposure verses chemical/sludge management costs. [ABSTRACT FROM AUTHOR]

This study investigates the formation of 14N- and 15N-nitrogenous disinfection by-product formation upon 15N-chloramination from four dissolved organic matters (DOMs). A series of XAD resins were used to fractionate DOM based on their hydrophobicity and functional group. The results show that hydrophobic acid (HPOA) fraction was the most important precursor pool for haloacetonitrile (HAN); these precursors mainly generated HAN through chloramine incorporation. HPOA and hydrophobic neutral (HPON) gave higher trichloronitromethane (TCNM) yields than the other fractions did. The nitrogen origin upon chloramination of HPOA was primarily from dissolved organic nitrogen (DON). By contrast, chloramines provided the main nitrogen sources during chloraminating HPON and HPOA with low DON to dissolved organic carbon ratios. The results of formation kinetics show that dichloroacetonitrile (DCAN) of which nitrogen source originate from DON formed faster than that of which nitrogen source originate from chloramines. Under normal chloramine exposure (4,000 mg-min/L, equal to 2 mg/L chloramines with around 2 days' reaction duration), 14N-DCAN concentration was two to over five times higher than that of 15N-DCAN. This study also uses a model to calculate the formation concentration of nitrogenous disinfection by-products without hydrolysis effects. The results show that 15N-DCAN formation was linearly correlated with chloramine exposure. [ABSTRACT FROM AUTHOR]

Ultrafiltration (UF) has been presented as an alternative to chemical disinfection to obtain safe drinking water, for its ability to remove microbiological contamination. Hollow-fiber UF membranes are designed as an effective barrier to microorganisms, for their high manufacturing integrity and for the 'potting' method adopted to seal fibers to the feeding/extraction manifold. While the main advantage over chemical disinfection is the drastic reduction of disinfection-by-product (DBP) formation, some chemicals are still required to control fouling and related sanitary risks. This study aims at an up-to-date assessment of UF use for surface water disinfection by compact, minimally-attended, automated plants. A 3.5 m³/h automated UF pilot-plant was run for 8 months for drinking quality purification of surface water from Pescia stream. Standard drinking water parameters, as well as specific microbiological parameters (Legionella, Mycobacterium, Adenovirus, coliphage) and DBP formation were monitored. Final results highlighted that the plant could reach a good removal of bacteria and a significant reduction of viruses. However, the adopted operation/maintenance policies had a strong impact on energy and water consumption, efficacy of bacterium/virus barrier and DBP formation. Hence, an accurate and competent operation, as well as the assistance of chemical disinfection, are still required for safe drinking water production. [ABSTRACT FROM AUTHOR]

Haloacetamides are disinfection byproducts (DBPs) formed through chlorine/chloramine disinfection processes in drinking waters and have been recently highlighted in the US national Reconnaissance Survey. These species occur at low concentrations, but have been determined to have high cytotoxicity and mutagenicity and therefore may represent a human health hazard. Advanced oxidation/reduction processes (AO/RPs) which utilize free radical reactions are new alternatives to degrade these species. This study reports the absolute bimolecular reaction rate constants for 12 haloacetamides with •OH radical and hydrated electron. The •OH radical reaction rates varied from 5.18x107 to 1.14x1010 M-1 S-1 and hydrated electron reaction rates varied from 5.00 x109 to 3.64 x 1010 M-1 S-1. Results obtained using an ion chromatograph indicated that ARPs are suitable for dehaloliazation of haloacetamides. These data are required for both evaluating AO/RPs for the destruction of these compounds and for studies of their fate and transport in surface waters where radical chemistry may be important in assessing their lifetime. [ABSTRACT FROM AUTHOR]

In line in situ electrochemical disinfection of drinking water with chloride concentrations as low as 10 mg/L has been demonstrated at practical flow rates of at least 3 m³/day using a novel perforated electrode flow through (PEFT) cell with a 50 μm inter-electrode gap. Sufficient chlorine to achieve 6 log inactivation of Escherichia coli bacteria was produced at applied voltages as low as 5 V and with energy consumptions as low as 0.5 kWh/m³. At slightly higher applied voltages, the specific lethality of electrochemically produced chlorine was enhanced by at least two orders of magnitude to greater than 50 L/mg min. This dramatically enhanced lethality is consistent with a synergistic effect resulting from reversible electroporation when electric fields greater than 1.3 kV/cm are produced. There was no evidence for involvement of other species such as reactive oxygen species (ROSs). Disinfection of drinking water using the PEFT cell is cost competitive with other disinfection technologies and when enhanced by the electric field is much less likely to produce disinfection by products. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) irradiation is an emerging technique for drinking water disinfection due to effective removal of enteric pathogens without generation of disinfection by-products (DBPs). In order to overcome the drawback of UV irradiation the integration of UV disinfection with sequential disinfectant was proposed. Among all the possible combinations and sequences, a UV/H2O2-Cl2 integrated system has proven to be effective in many previous studies. In this study, a UV/H2O2 flow-through system followed by free chlorine was built and studied. MS-2 coliphage, as a model for a waterborne virus, were inactivated to evaluate the disinfection capacity. Assimilable organic carbon (AOC) tests and an Ames assay using Salmonella typhimurium TA98 and TA100 on such a proposed integrated system were also performed to determine re-growth potential of bacteria and genotoxicity, respectively. Briefly, such a proposed flow-through system was effective in removal of MS-2 coliphage and no genotoxic potential was detected according to the results; however, an increase of AOC may raise concerns of bacterial re-growth along the subsequent distribution system. [ABSTRACT FROM AUTHOR]

Humic substances (HS) cause problems in water purification because of disinfection by-product (DBP) formation during chlorination. The efficiency of activated carbon (AC) adsorption as a method in drinking water treatment has been investigated in removing HS at different pH values (pH= 5; 6; 7; 8) in static equilibrium experiments. The degradation of HS was studied with an EM (effective microorganisms) bacteria community, and solutions of fulvic acid, sodium humate furthermore extracts of sandy soil were investigated. EM products are widely used but their effect on HS has no been investigated before. The combination of EM and AC methods in the case of fulvic acid resulted in higher performance than any of these methods alone. Humic substances were analyzed using a UV-VlS spectrophotometer and by total organic carbon (TOC) measurements. The carbon/nitrogen ratio was also determined, which enabled conclusions to be made for the nutrient supply. According to these results the degradation was efficient, especially in fulvic acid solutions. [ABSTRACT FROM AUTHOR]

Water utilities have experienced increasing pressure to minimise the formation of disinfection by-products (DBPs), as reflected in the increasingly stringent regulations and guidelines for the concentrations of DBPs in drinking water. Understanding the disinfection characteristics and molecular weight (MW) distribution of natural organic matter (NOM) will assist in the optimisation of drinking water treatment processes to minimise the formation of DBPs. This study investigated the disinfection behaviour of MW fractions of NOM isolated from a Western Australian source water. The NOM was fractionated and separated using preparative size exclusion chromatography (SEC) and the fractions were chlorinated in the presence of bromide ion. The larger MW fractions of NOM were found to produce the highest concentrations of DBPs (trihalomethanes, haloacetic acids, haloacetonitriles, haloketones, and haloaldehydes), with the low MW fractions still producing significant amounts of these DBPs. The results also showed a trend of an increasing proportion of brominated DBPs with decreasing MW and aromatic character. Considering that the smaller MW fractions of NOM produce significant amounts of DBPs, with a higher relative contribution from brominated DBPs, water treatment processes need to be optimised for either bromide removal or the removal of aliphatic, small MW fractions of NOM, in order to meet DBP guidelines and regulations. [ABSTRACT FROM AUTHOR]

Factors affecting formation of disinfection byproducts (DBPs) such as trihalomethane THM and haloacetic acid HAA in drinking water treated with chlorine dioxide ClO2 as disinfectant were investigated. The collected data were used to develop mathematical models that predict the formation of THM and HAA in terms of each of the studied factor: ClO2 dose, total organic content TOC, bromide ion concentration, pH, temperature and contact time. Mathematical models were developed for four trihalomethane species, as well as total trihalomethanes TTHM, in addition to six haloacetic acid species and total haloacetic acids THAA. Predicted THM and HAA concentrations using developed models were compared to actual concentrations measured in real samples. Results showed good correlation between measured and calculated values. This means that the method presented could be used to obtain good estimates of THM and HAA concentrations formed when the water is treated with ClO2 under different experimental conditions. [ABSTRACT FROM AUTHOR]

Batch ozonation experiments were conducted to investigate the effects of various operating options (i.e. additions of acid, ethanol, ammonium ion, and hydrogen peroxide) on the formation of disinfection byproducts (DBPs) in six different source waters. Formation of bromate, total organic bromines, total aldehydes (the sum of 13 aldehydes) was evaluated, assuming they represent three different types of DBPs during ozonation (i.e. inorganic bromine DBPs, organobromine DBPs, and non-brominated organic DBPs, respectively). Among the tested options, acid addition was found to be the best one to control all the three types of DBPs simultaneously on an ozone exposure basis. [ABSTRACT FROM AUTHOR]

Little information is available on the evolution of remaining organic matter (ROM) in a water distribution system (WDS) and its impact on the generation of disinfection by-products (DBPs). This research involves the characterization, through sample fractionation processes and experimental chlorination tests, of the reactivity of DBP precursors occurring within a WDS. The study is based on samples collected in various locations of a WDS during a complete year. For each sample, six fractions were generated to determine their potential for formation of trihalomethanes (THMs) and haloacetic acids (HAAs). Fractionation processes on ROM demonstrated that the spatial behavior of precursors for THMs differs from that for precursors of HAAs. In addition, experimental chlorination tests showed that the reactivity of the investigated fractions, in terms of DBP formation potential (DBPfp), was different from each other according to location in the WDS. DBPfp for the studied fractions changed drastically during water treatment. However, changes of DBPfp for fractions were relatively low between the beginning and the extremity of the distribution system. Since the results of this research confirm that the ability to produce DBPs is related to the nature of the fractions, they could be useful to evaluate the impact of re-chlorination on DBP formation in a WDS. [ABSTRACT FROM AUTHOR]

The NDMA formation potential (NDMA FP) of four commonly used amine-based cationic water treatment polymers was assessed in reactions with chlorine-based oxidants (free chlorine, monochloramine and chlorine dioxide) and nitrosifying agents (nitrite and nitrate). Relatively high dosages of polymers were directly exposed to oxidants for long reaction times in the FP tests to assess the potential to form NDMA and obtain mechanistic insight. Results show that the NDMA FP of the polymers generally follows the trend of aminomethylated polyacrylamide (Mannich polymer) .. poly(epichlorohydrin-dimethylamine) (polyamine) . poly(diallyldimethylammonium chloride) (polyDADMAC) . cationic polyacrylamide copolymer (cationic PAM). The high NDMA FP of Mannich polymer was largely due to the high amount of dimethylamine (DMA) residue in the polymer solution. For the other three polymers, the DMA concentration was increased after oxidation, indicating polymer degradation, and the trend of DMA increase agreed with that of NDMA FP. Among the oxidants, NDMA formation followed the order of monochloramine . free chlorine . chlorine dioxide, despite that the DMA release from the polymers caused by the oxidant followed the opposite order. At equal dosages, nitrite and nitrate generated NDMA from the polymers at levels comparable to those by free chlorine and chlorine dioxide; even so, the nitrosifying agents are unlikely to contribute significantly to NDMA formation due to expected lower concentrations in drinking water treatment systems. Jar tests followed by monochloramination of real water samples using conditions in line with those at potable water treatment plants generally showed relatively small contributions from polyamines and polyDADMACs to the overall NDMA formation. [ABSTRACT FROM AUTHOR]

This study was aimed at developing statistically based model equations capable of predicting chlorite and chlorate formation during the primary oxidation/disinfection treatment using data collected on two real scale treatment plants. In this phase many operational parameters, raw water quality as well as the second oxidant dose applied, sodium hypochlorite, importantly influence the chlorite and chlorate formation. The operational parameters and the raw water quality correlated with chlorite and chlorate formation were: contact time, chemical doses, temperature, turbidity, organic substances (non-purgeable organic carbon and UV254nm absorbance), pH, iron and ammonium concentration. Given the high numbers of variables two models have been developed. The first one (complex) includes all the studied parameters; the other model (simplified) takes into account only the parameters that gave a significant correlation (.0.55) with the dependent variable. Nearly 60% of the predictions for chlorite formation were observed to be within ^40% of the measured levels and the found key parameters were the water organic content and the physico-chemical characteristics (pH and temperature). Nearly 85% of the predictions for chlorate formation were observed to be within ±40% of the measured levels and the found key parameters were again the chemical physical water characteristics (pH and temperature) and the applied chemicals doses. [ABSTRACT FROM AUTHOR]

There are established chemical models that can predict disinfectant decay and DBPs formation with respect to various water quality parameters and reaction time (water age). While models such as EPANET are powerful tools in hydraulic simulations, they have limited use in simulating water quality, containing only a basic chlorine decay subroutine. This paper presents a study on the use of a link that was developed to couple the external water quality models and the hydraulic model of EPANET 2.The coupled model has been applied to a hypothetical distribution system under steady and non steady conditions. Simulations have taken the form of sensitivity analyses to probe operational strategies such as modified treatment as well as optimized secondary disinfection in order to maintain sufficient chlorine residual at critical points within the distribution system. Simulations have also been performed to compare the relative rates of formation of THMs vs HAAs as well as individual species. Of particular interest is optimization of chlorine dose to minimize residual chlorine under non-steady-state conditions. [ABSTRACT FROM AUTHOR]

The formation of disinfection by-products (DBPs) was evaluated from a chloraminated water after coagulation with and without prechlorination or preozonation. Prechlorination enhanced formation of trihalomethane (THM), 1,1,1-trichloro-2-propanone (1,1,1-TCP) and total organic chlorine (TOCl) and the concentrations of most DBPs increased with increasing chlorine dosages. Preozonation reduced dichloroacetonitrile (DCAN) and TOCl formation but increasing ozone (O3) dosages did not necessarily reduce the formation of THM, 1,1-dichloro-2-propanone (1,1-DCP) and total organic bromine (TOBr). Increasing coagulant doses reduced the formation of most DBPs and TOCl. However, the formation of TOBr cannot be readily controlled by coagulation in most cases except the case involving prechlorination. [ABSTRACT FROM AUTHOR]

An original approach for modelling disinfection by-products formation in chlorinated water is proposed. Assuming a multi-step formation mechanism, and introducing partition coefficients to differentiate the various compounds formed as a consequence of halogen incorporation and oxidation reactions, a system of linear differential equations is obtained and solved in explicit terms. Two sets of solutions are derived: the first one assuming that the reaction rate is the same for all species included in the model, as a consequence of steady state approximation; the second one assuming that the reaction rate is different from one species to another. Experimental data, obtained varying reaction time and chlorine dose, are used to calibrate the two models. Statistic tests are also performed to compare the two sets of solutions and validate the assumed hypotheses. [ABSTRACT FROM AUTHOR]

Source water samples were collected from Guangzhou segment of Pearl River and filtered through Amiconw YC-05, YM-1, YM-3, YM-10, YM-30, YM-100 and ZM-500 membranes sequentially after pre-treatment. The apparent molecular weights of the 8 fractions were calibrated using high-performance size exclusion chromatograph (HPSEC) and they ranged from 0.36 to 182.6 kDa. These fractionated isolates and the raw water were disinfected by chlorine or chlorine dioxide to determine their disinfection characteristics. Results showed that apparent molecular weight of the main dissolved organic matter (DOM) in the RO isolate of water sample was less than 360 Da and this part of the DOM was mainly from anthropogenic activities and contamination of wastewater. RO fraction was the controlling factor for the raw water disinfection process according to the THMs concentrations detected. Disinfection by chlorine dioxide produced less THMs that by chlorine. [ABSTRACT FROM AUTHOR]

The need of disinfecting potable water to eliminate potential health risks associated with waterborne pathogens, however inevitably resulting in leaving elevated toxicity in water by forming disinfection by-products (DBPs) is being considered as one of the primary threats to human well-being. Bromate is a carcinogenic DBP mainly formed during ozonation of bromide-containing water. The current maximum contaminant level (MCL) of bromate in the US national primary drinking water standard is set at 10 μg/L. With continuous improvements in analytical instrumentation and removal technologies, a lower MCL for bromate is expected in the future. Current researches on bromate control strategies involve minimizing bromate formation (like ammonia addition) or removing bromate after formation (like carbon adsorption), however have their own limitations. Seeking for alternative bromate control strategies that can be used alone (or in combine with others) is of great value and in urgent need when water quality standards are getting more stringent. This paper reviews the occurrence of bromate in water supply and evaluates the effectiveness of bromate removal technologies applied, to advance our understanding of bromate fate and degradation in water supply system for future study. [ABSTRACT FROM AUTHOR]

A major portion of the total organic halogen formed during chlorination is likely attributable to high molecular weight (MW) DBPs (above 500 Da), which may have potential adverse health effects. In this work, highly dosed chlorinated Suwannee River fulvic acid samples with and without coagulation pretreatment were separated and fractionated by using ultrafiltration (UF) and size exclusion chromatography (SEC) techniques. The SEC fractions corresponding to the high MW region were concentrated with nitrogen sparging and characterized by negative ion electrospray ionization/mass spectrometry (ESI-MS). The SEC- UV chromatograms and SEC-ESI-MS spectra show that coagulation greatly reduced the formation of high MW DBPs. It is of note that phosphate from the buffer could affect the ESI-MS characterization in 2-3 SEC fractions although most of the phosphate had been removed by UF. [ABSTRACT FROM AUTHOR]

Factors impacting the Cost equivalency point for deploying strategically-located treatment units within a distributed optimal technology network (DOT-Net) to manage network-derived water quality degradation are defined and quantified. The cost equivalency point is essentially the 'breakeven' allowable cost for implementing DOT-Net strategy as an alternative to upgrading a central treatment facility to 'pretreat' water sufficiently to manage quality degradation within a potable water distribution network. For the purposes of the analysis presented, water quality is assumed to degrade linearly with time as it flows through the distribution network. Disinfection by-product (DBP) formation, selected as a representative water quality degradation parameter, was modeled to predict service population DBP exposure and resulting cost of centralized treatment plant upgrades to meet water quality goals. The equivalency point was determined by apportioning the anticipated cost for upgrading the centralized treatment facilities over the fraction of service connections receiving deficient quality water. Both concentration of DBP precursor material and service population size are found to have limited impact on the equivalency point of a distributed treatment unit. The advantages and disadvantages of various treatment methods available for in-network water treatment are outlined and the ancillary functional requirements of the distributed treatment unit are delineated. [ABSTRACT FROM AUTHOR]

The biofilm community structure in a granular activated carbon (GAC) filter was investigated by ribosomal intergenic spacer region analysis (RISA). The results showed that microbial diversity diminished and stabilized with time of filter operation. One bacterium (Hydrogenophaga pa/leronh,) was identified according to its 16S-rRNA sequence. However, this bacterium did not degrade any of the HAAs tested. Another bacterium was isolated from biofilm enrichment cultures and was capable of degrading CIAA and CI2AA. [ABSTRACT FROM AUTHOR]

A demonstration plant consisted of ozone/granular activated carbon (GAG) was operated using sand filtered water as an influent to study the feasibility for introduction of an advanced water treatment. In ozonating the sand filtered water, dissolved organic carbon (DOG) slightly increased at an ozone dose of less than 1.0mg O3/mg C, and the largest DOC reduction was exhibited at 1.0mg O3/mg G. As ozone dosage increased from 1.0 to 5.0mg O3/mg G, DOG decreased no more, whereas UV absorbance at 254 nm gradually decreased with increasing ozone dosage. The hydrophobic fraction in natural organic matter (NOM) was considered as a predominant reactant from the result of a rapid decrease in specific ultraviolet absorbance (SUVA). Since the specific reaction sites in the NOM molecule for hatoform reaction were attacked by ozonation, the disinfection by-product (DBP) formation potentials could be reduced. The hydrophobic fraction decreased from 36.3% to 28.7% by ozonation and then decreased to 24.2% through carbon adsorption. The hydrophilic fraction changed only by 1.0% during ozonation, while it decreased by 28.3% through carbon adsorption. Therefore, ozonation followed by carbon adsorption is an acceptable process for the reduction of latent risk through selective oxidation and adsorption of different NOM fractions. [ABSTRACT FROM AUTHOR]

Applicability of a rotating reactor for photocatalytic oxidation of humic substances extracted from the Han River in Seoul, Korea (Han-HS) was investigated. Because air blowing for complete dispersion of TiO2 photocatalysts could inhibit ultraviolet (UV)-irradiation between UV lamps and photocatalysts by air bubbles, a rotating photocatalytic reactor with four baffles was used for better UV-irradiation in this study. Han-HS was extracted and treated with UV-irradiation. Because Han-HS is different from other commercial humic materials (e.g. Aldrich Humic acid and International Humic Substance Society NOM), structural spectroscopic analyses were conducted by FT-IR and 13C-NMR. Immobilized TiO2 coated on hollow beads was used to separate and recover the photocatalyst. During two hours of UV-irradiation, absorbance at 254 nm (UV254) and total organic carbon (TOC) content were monitored. Photocatalytic oxidation efficiencies of different wavelengths of UV lamps (254 nm and 352 nm) were also compared and raw and pre-chlorinated waters of the Han River were used to evaluate the applicability for water treatment. [ABSTRACT FROM AUTHOR]