Concentrations Of Disinfection By-products Research Articles

Disinfection by-products of chlorine dioxide (chlorite, chlorate, and trihalomethanes): Occurrence in drinking water in Qatar

The occurrence of chlorine dioxide (ClO2) disinfection by-products (DBPs) in drinking water, namely, chlorite, chlorate, and trihalomethanes (THMs), was investigated. Two-hundred-ninety-four drinking water samples were collected from seven desalination plants (DPs), four reservoirs (R), and eight mosques (M) distributed within various locations in southern and northern Qatar. The ClO2 concentration levels ranged from 0.38 to <0.02 mg L−1, with mean values of 0.17, 0.12, and 0.04 mg L−1 for the DPs, Rs, and Ms, respectively. The chlorite levels varied from 13 μg L−1 to 440 μg L−1, with median values varying from 13 to 230 μg L−1, 77–320 μg L−1, and 85–440 μg L−1 for the DPs, Rs, and Ms, respectively. The chlorate levels varied from 11 μg L−1 to 280 μg L−1, with mean values varying from 36 to 280 μg L−1, 11–200 μg L−1, and 11–150 μg L−1 in the DPs, Rs, and Ms, respectively. The average concentration of THMs was 5 μg L−1, and the maximum value reached 77 μg L−1 However, all of the DBP concentrations fell within the range of the regulatory limits set by GSO 149/2009, the World Health Organization (WHO), and Kahramaa (KM).

Effect of Microcystis aeruginosa on Disinfection By-Product Formation During Chlorination of Chironomid larvae Metabolites

Abstract Many studies have shown that both Chironomid larvae and Microcystis aeruginosa would form disinfection by-products (DBPs) under chlorination or chloramination. However, in the natural state, Microcystis aeruginosa and Chironomid larvae exist together. DBPs of chlorination between Chironomid larvae and Microcystis aeruginosa were widely assumed to be “black box.” This study focused on effects of Microcystis aeruginosa on DBP formation during the chlorination of Chironomid larvae metabolites. Results of the study suggest that the presence of Microcystis aeruginosa not only influences the concentration of DBPs from Chironomid larvae metabolism, but also changes the trend of individual DBPs. Results suggest that Microcystis aeruginosa may change the trend of chloropicrin (TCNM), and Microcystis aeruginosa may promote TCM, 1,1-DCP, 1,1,1-TCP, and TCNM formation, while inhibiting the accumulation of DCAA and TCAA. Results illustrate the mechanism of Microcystis aeruginosa participating in DBP formation...

Effects of UV-based treatment on volatile disinfection byproducts in a chlorinated, indoor swimming pool

Ultraviolet (UV) irradiation and chlorination are commonly used together in treatment of swimming pool water because they function as complementary disinfectants and because UV-based processes have been shown to promote photodecay of chloramines. However, UV-based treatment also has the potential to promote formation of some disinfection byproducts (DBPs). As a result, the overall effects of UV irradiation with chlorination on swimming pool chemistry remain unclear. To address this issue, a three-year study was conducted in a chlorinated, indoor swimming pool under three different operating conditions: conventional chlorination (1st year) which served as a control, chlorination augmented by MP UV irradiation (2nd year), and chlorination augmented by LP UV irradiation (3rd year). Water samples were collected from the pool for measurement of pH, temperature, total alkalinity, free and combined chlorine, eleven volatile DBPs, and urea concentration. After installation of MP UV, the concentrations of most volatile DBPs decreased; similar effects were observed after inclusion of LP UV. Collectively, these results imply an overall improvement in water quality as a result of the inclusion of the both UV systems. In general, MP UV was more efficient than LP UV for reducing the concentrations of most of the volatile DBPs measured in this pool. However, a need exists to standardize the application of UV systems in recreational water settings.

Granular Activated Carbon Treatment May Result in Higher Predicted Genotoxicity in the Presence of Bromide.

Certain unregulated disinfection byproducts (DBPs) are more of a health concern than regulated DBPs. Brominated species are typically more cytotoxic and genotoxic than their chlorinated analogs. The impact of granular activated carbon (GAC) on controlling the formation of regulated and selected unregulated DBPs following chlorine disinfection was evaluated. The predicted cyto- and genotoxicity of DBPs was calculated using published potencies based on the comet assay for Chinese hamster ovary cells (assesses the level of DNA strand breaks). Additionally, genotoxicity was measured using the SOS-Chromotest (detects DNA-damaging agents). The class sum concentrations of trihalomethanes, haloacetic acids, and unregulated DBPs, and the SOS genotoxicity followed the breakthrough of dissolved organic carbon (DOC), however the formation of brominated species did not. The bromide/DOC ratio was higher than the influent through much of the breakthrough curve (GAC does not remove bromide), which resulted in elevated brominated DBP concentrations in the effluent. Based on the potency of the haloacetonitriles and halonitromethanes, these nitrogen-containing DBPs were the driving agents of the predicted genotoxicity. GAC treatment of drinking or reclaimed waters with appreciable levels of bromide and dissolved organic nitrogen may not control the formation of unregulated DBPs with higher genotoxicity potencies.

Study on a Polish peat bog “Rucianka” as a source of yeast strains capable of effective phenol biodegradation

Sodium hypochlorite (NaClO) is the most commonly used disinfectant in pool treatment system. Outdoor pools usually suffer from the strong sunlight irradiation which degrades the free chlorine rapidly. In addition, more pools start to adopt the recirculation of swimming pool water, which intensifies the disinfection by-product (DBP) accumulation issue. Given these potential drawbacks of using NaClO in the tropical environment, two alternative organic-based disinfectants, trichloroisocyanuric acid (TCCA, C3Cl3N3O3) and bromochlorodimethylhydantoin (BCDMH, C5H6BrClN2O2), were investigated and compared to NaClO in terms of their self-degradation and the formation of DBPs, including trihalomethanes (THMs) and haloacetic acids (HAAs), under simulated tropical climate conditions. The result reveals that halogen stabilizer, TCCA, had the advantages of slower free chlorine degradation and lower DBP concentration compared to NaClO, which makes it a good alternative disinfectant. BCDMH was not recommended mainly due to the highly reactive disinfecting ingredient, hypobromous acid (HBrO), which fails to sustain the continuous disinfection requirement. Total disinfectant dosage was the main factor that affects residual chlorine/bromine and THM/HAA formation regardless of different disinfectant dosing methods, e.g. shock dosing (one-time spiking) in the beginning, and continuous dosing during the whole experimental period. Two-stage second-order-kinetic-based models demonstrate a good correlation between the measured and predicted data for chlorine decay (R2 ≥ 0.95), THM (R2 ≥ 0.99) and HAA (R2 ≥ 0.83) formation. Higher temperature was found to enhance the DBP formation due to the temperature dependence of reaction rates. Thus, temperature control of pools, especially for those preferring higher temperatures (e.g. hydrotherapy and spa), should take both bather comfort and DBP formation potential into consideration. It is also observed that chlorine competition existed between different precursors from natural organic matters (NOM) in filling water and body fluid analogue (BFA). Among the composition of BFA, uric acid, citric acid and hippuric acid were found to be the main precursors for HAA formation.

An insight of disinfection by-product (DBP) formation by alternative disinfectants for swimming pool disinfection under tropical conditions

Sodium hypochlorite (NaClO) is the most commonly used disinfectant in pool treatment system. Outdoor pools usually suffer from the strong sunlight irradiation which degrades the free chlorine rapidly. In addition, more pools start to adopt the recirculation of swimming pool water, which intensifies the disinfection by-product (DBP) accumulation issue. Given these potential drawbacks of using NaClO in the tropical environment, two alternative organic-based disinfectants, trichloroisocyanuric acid (TCCA, C3Cl3N3O3) and bromochlorodimethylhydantoin (BCDMH, C5H6BrClN2O2), were investigated and compared to NaClO in terms of their self-degradation and the formation of DBPs, including trihalomethanes (THMs) and haloacetic acids (HAAs), under simulated tropical climate conditions. The result reveals that halogen stabilizer, TCCA, had the advantages of slower free chlorine degradation and lower DBP concentration compared to NaClO, which makes it a good alternative disinfectant. BCDMH was not recommended mainly due to the highly reactive disinfecting ingredient, hypobromous acid (HBrO), which fails to sustain the continuous disinfection requirement. Total disinfectant dosage was the main factor that affects residual chlorine/bromine and THM/HAA formation regardless of different disinfectant dosing methods, e.g. shock dosing (one-time spiking) in the beginning, and continuous dosing during the whole experimental period. Two-stage second-order-kinetic-based models demonstrate a good correlation between the measured and predicted data for chlorine decay (R2 ≥ 0.95), THM (R2 ≥ 0.99) and HAA (R2 ≥ 0.83) formation. Higher temperature was found to enhance the DBP formation due to the temperature dependence of reaction rates. Thus, temperature control of pools, especially for those preferring higher temperatures (e.g. hydrotherapy and spa), should take both bather comfort and DBP formation potential into consideration. It is also observed that chlorine competition existed between different precursors from natural organic matters (NOM) in filling water and body fluid analogue (BFA). Among the composition of BFA, uric acid, citric acid and hippuric acid were found to be the main precursors for HAA formation.

Progressive Increase in Disinfection Byproducts and Mutagenicity from Source to Tap to Swimming Pool and Spa Water: Impact of Human Inputs.

Pools and spas are enjoyed throughout the world for exercise and relaxation. However, there are no previous studies on mutagenicity of disinfected spa (hot tub) waters or comprehensive identification of disinfection byproducts (DBPs) formed in spas. Using 28 water samples from seven sites, we report the first integrated mutagenicity and comprehensive analytical chemistry of spas treated with chlorine, bromine, or ozone, along with pools treated with these same disinfectants. Gas chromatography (GC) with high-resolution mass spectrometry, membrane-introduction mass spectrometry, and GC-electron capture detection were used to comprehensively identify and quantify DBPs and other contaminants. Mutagenicity was assessed by the Salmonella mutagenicity assay. More than 100 DBPs were identified, including a new class of DBPs, bromoimidazoles. Organic extracts of brominated pool/spa waters were 1.8× more mutagenic than chlorinated ones; spa waters were 1.7× more mutagenic than pools. Pool and spa samples were 2.4 and 4.1× more mutagenic, respectively, than corresponding tap waters. The concentration of the sum of 21 DBPs measured quantitatively increased from finished to tap to pool to spa; and mutagenic potency increased from finished/tap to pools to spas. Mutagenic potencies of samples from a chlorinated site correlated best with brominated haloacetic acid concentrations (Br-HAAs) (r = 0.98) and nitrogen-containing DBPs (N-DBPs) (r = 0.97) and the least with Br-trihalomethanes (r = 0.29) and Br-N-DBPs (r = 0.04). The mutagenic potencies of samples from a brominated site correlated best (r = 0.82) with the concentrations of the nine HAAs, Br-HAAs, and Br-DBPs. Human use increased significantly the DBP concentrations and mutagenic potencies for most pools and spas. These data provide evidence that human precursors can increase mutagenic potencies of pools and spas and that this increase is associated with increased DBP concentrations.

N-Nitrosamines and halogenated disinfection byproducts in U.S. Full Advanced Treatment trains for potable reuse

Water utilities are increasingly considering indirect and direct potable reuse of municipal wastewater effluents. Disinfection byproducts (DBPs), particularly N-nitrosamines, are key contaminants of potential health concern for potable reuse. This study quantified the concentrations of N-nitrosamines and a suite of regulated and unregulated halogenated DBPs across five U.S. potable reuse Full Advanced Treatment trains incorporating microfiltration, reverse osmosis, and UV-based advanced oxidation. Low μg/L concentrations of trihalomethanes, haloacetic acids, dichloroacetonitrile, and dichloroacetamide were detected in the secondary or tertiary wastewater effluents serving as influents to potable reuse treatment trains, while the concentrations of N-nitrosamines were more variable (e.g., <2–320 ng/L for N-nitrosodimethylamine). Ozonation promoted the formation of N-nitrosamines, haloacetaldehydes, and haloacetamides, but biological activated carbon effectively reduced concentrations of these DBPs. Application of chloramines upstream of microfiltration for biofouling control increased DBP concentrations to their highest levels observed along the treatment trains. Reverse osmosis rejected DBPs to varying degrees, ranging from low for some (e.g., N-nitrosamines, trihalomethanes, and haloacetonitriles) to high for other DBPs. UV-based advanced oxidation eliminated N-nitrosamines, but only partially removed halogenated DBPs. Chloramination of the treatment train product waters under simulated distribution system conditions formed additional DBPs, with concentrations often equaling or exceeding those in the treatment train influents. Overall, the concentration profiles of DBPs were fairly consistent within individual treatment trains for sampling campaigns separated by months and across different treatment trains for the same sampling time window. Weighting DBP concentrations by their toxic potencies highlighted the potential significance of haloacetonitriles, which were not effectively removed by reverse osmosis and advanced oxidation, to the DBP-associated toxicity in potable reuse waters.

Fate and transport of DBPs in a deep confined aquifer during artificial recharge process

Although the behavior of disinfection by-products (DBPs) in groundwater artificial recharge projects is considered as one of the crucial factors affecting potable water, surprisingly, its mechanism remains unclear. Our in situ study on transport and fate of DBPs (especially chloroform) was carried out in a test site located in Southeast China. In this study, four types of DBPs: dichloromethane, chloroform, bromodichloromethane (BDCM), and dibromochloromethane (DBCM), were detected, among which the occurrence rate and concentration of chloroform were found the highest. The DBPs concentration within the observation well (J4) situated 10 m away is higher than that in the source water, especially during the first 10 days since the beginning of recharge. And the difference between peak concentration in J4 and the other observation well (J5) located 17 m away was approximately 13 μg/L for chloroform, 0.1 μg/L for dichloromethane, 0.7 μg/L for DBCM, and insignificant for BDCM. The breakthrough took 16 days for chloroform from J4 to J5. According to attenuation analysis, the chemical hydrolysis, adsorption, and other processes were insignificant. Therefore, biodegradation was most likely dominating the attenuation process, and half-lives of chloroform ranged from 11.2 to 40.5 days, which was mainly a contribution of ammonia-oxidizing bacteria Nitrosomonas europaea via aerobic co-metabolism. In consistence with the transformation of groundwater redox conditions, the biodegradation rate of chloroform was changing as well. As the recharge time got longer, half-lives of chloroform had a tendency to stabilize at roughly 14 days.

Disinfection by-products effect on swimmers oxidative stress and respiratory damage

Disinfection by-products (DBPs) are generated through the reaction of chlorine with organic and inorganic matter in indoor swimming pools. Different DBPs are present in indoor swimming pools. This study evaluated the effects of different chlorinated formations in oxidative stress and lung damage in 20 swimmers after 40 min of aerobic swimming in 3 indoor pools with different characteristics. Biological samples were collected to measure lung damage (serum-surfactant-associated proteins A and B), oxidative stress parameters (plasma protein carbonylation and malondialdehyde, and whole-blood glutathione oxidation), and swimming exertion values (blood lactate) before and after exercise. Free chlorine and combined chlorine in water, and chlorine in air samples were determined in all the swimming pools. Chlorination as disinfection treatment led to the formation of chloramines in water samples, mainly mono- and dichloramine. However, free chlorine was the predominate species in ultraviolet-treated swimming pool. Levels of total chlorine increased as a function of the swimming activity in chlorinated swimming pools. The lower quality of the installation resulted in a higher content of total chlorine, especially in air samples, and therefore a higher exposure of the swimmer to DBPs. However, the concentration level of chlorinated DBPs did not result in significant variation in serum-surfactant-associated proteins A and oxidative stress parameters in swimmers. In conclusion, the quality of the installation affected the DBPs concentration; however, it did not lead to lung epithelial damage and oxidative stress parameters in swimmers.

Towards reducing DBP formation potential of drinking water by favouring direct ozone over hydroxyl radical reactions during ozonation

When ozonation is employed in advanced water treatment plants to produce drinking water, dissolved organic matter reacts with ozone (O3) and/or hydroxyl radicals (OH) affecting disinfection byproduct (DBP) formation with subsequently used chlorine-based disinfectants. This study presents the effects of varying exposures of O3 and OH on DBP concentrations and their associated toxicity generated after subsequent chlorination. DBP formation potential tests and in vitro bioassays were conducted after batch ozonation experiments of coagulated surface water with and without addition of tertiary butanol (t-BuOH, 10 mM) and hydrogen peroxide (H2O2, 1 mg/mg O3), and at different pH (6–8) and transferred ozone doses (0–1 mg/mg TOC).Although ozonation led to a 24–37% decrease in formation of total trihalomethanes, haloacetic acids, haloacetonitriles, and trihaloacetamides, an increase in formation of total trihalonitromethanes, chloral hydrate, and haloketones was observed. This effect however was less pronounced for samples ozonated at conditions favoring molecular ozone (e.g., pH 6 and in the presence of t-BuOH) over OH reactions (e.g., pH 8 and in the presence of H2O2). Compared to ozonation only, addition of H2O2 consistently enhanced formation of all DBP groups (20–61%) except trihalonitromethanes. This proves that OH-transformed organic matter is more susceptible to halogen incorporation. Analogously, adsorbable organic halogen (AOX) concentrations increased under conditions that favor OH reactions. The ratio of unknown to known AOX, however, was greater at conditions that promote direct O3 reactions. Although significant correlation was found between AOX and genotoxicity with the p53 bioassay, toxicity tests using 4 in vitro bioassays showed relatively low absolute differences between various ozonation conditions.

Enhancement effects of ultrasound on secondary wastewater effluent disinfection by sodium hypochlorite and disinfection by-products analysis

Since fecal coliforms was introduced as a standard indicator of pollutants in effluents of municipal wastewater treatment plants in China in 2003, chlorine had been widely used in many wastewater treatment plants. However, concerns about the disinfection by-products (DBPs) of chlorine have been increasing. One of the effective way to reduce the production of DBPs is to reduce the effective chlorine dosage by improving the utilization rate of disinfectant. Ultrasound (US) is proved to be effective in wastewater treatment for its multiple chemical and physical effects produced by cavitation, which could favor the disinfection process accordingly. For the purpose of improving disinfection efficiency with the help of US, following points are addressed in the current study: (1) investigate the enhancement effects of US on the disinfection efficiency of sodium hypochlorite (NaClO) for real secondary effluents of municipal wastewater treatment plants; (2) evaluate the possibility of using US specific energy consumption (kJ/L) as an parameter for disinfection efficiency evaluation; and (3) quantify the reduction in chlorine-DBPs through US application. Results demonstrated that sonication could reduce two-thirds (US pretreatment) or one-third (simultaneous US and NaClO disinfection) of the required concentrations of NaClO (available chlorine) for 4 log reduction of fecal coliforms, which could meet the Class 1A (fecal coliforms less than 1000CFU/L) discharge standard of China. In addition, US pretreatment with NaClO disinfection performed better enhancement in disinfection efficiency compared with simultaneous US and NaClO disinfection. Furthermore, analysis on DBPs showed that US application as pretreatment could obviously reduce the contents of trichloromethane (TCM) and trichloroacetic acid (TCAA) by more than 85% and 50%, respectively, compared with NaClO disinfection alone for the same disinfection efficiency. Meanwhile, the experimental results also showed that the disinfection efficiency and DBPs concentration were only slightly affected under a constant US specific energy consumption, although input power density and irradiation time changed, indicating that specific energy consumption (kJ/L) could be considered as a better control parameter for disinfection efficiency evaluation.

New Trends in Disinfection By-Products Formation upon Water Treatment

This review paper deals with the formation of disinfection by-products (DBPs). Water basin remains a wonderful chemical reactor that allows the occurrence of intricate secondary disinfection chemical reactions, forming several hundreds of DBPs at the same time with microorganisms killing. The kinetics of DBPs formation is tightly dependent on water physicochemical characteristics such as temperature, hydrophobic/hydrophilic fractions in natural organic matter (NOM), pH, and pretreatment. Reducing DBPs levels in drinking water is not a relevant measure as the newly-developed analytical techniques and the health-related research reveal that the tolerable DBPs' levels must be further decreased and would be detected at ng L-1 instead of μg L-1 scale. Furthermore, because of the fact that man is being exposed to DBPs concentrations in drinking water in his lifetime, there will be a cumulative effect of these toxic chemical products even at their more reduced concentrations. Hence, the removal of these chemical products is sought for and is considered a real challenge and the main objective of water treatment technology for mankind survival.

Concentration levels of disinfection by-products in 14 swimming pools of China

Swimming has become a popular exercising and recreational activity in China but little is known about the disinfection by-products (DBPs) concentration levels in the pools. This study was conducted as a survey of the DBPs in China swimming pools, and to establish the correlations between the DBP concentrations and the pool water quality parameters. A total of 14 public indoor and outdoor pools in Beijing were included in the survey. Results showed that the median concentrations for total trihalomethanes (TTHM), nine haloacetic acids (HAA9), chloral hydrate (CH), four haloacetonitriles (HAN4), 1,1-dichloropropanone, 1,1,1-trichloropropanone and trichloronitromethane were 33.8, 109.1, 30.1, 3.2, 0.3, 0.6 μg·L−1 and below detection limit, respectively. The TTHM and HAA9 levels were in the same magnitude of that in many regions of the world. The levels of CH and nitrogenous DBPs were greatly higher than and were comparable to that in typical drinking water, respectively. Disinfection by chlorine dioxide or trichloroisocyanuric acid could substantially lower the DBP levels. The outdoor pools had higher TTHM and HAA9 levels, but lower trihaloacetic acids (THAA) levels than the indoor pools. The TTHM and HAA9 concentrations could be moderately correlated with the free chlorine and total chlorine residuals but not with the total organic carbon (TOC) contents. When the DBP concentration levels from other survey studies were also included for statistical analysis, a good correlation could be established between the TTHM levels and the TOC concentration. The influence of chlorine residual on DBP levels could also be significant.

Impact of Water Heaters on the Formation of Disinfection By‐products

This study examined the effect of water heaters and home‐heating scenarios on the formation and decomposition of disinfection by‐products (DBPs). Residential concentrations of DBPs were investigated in cold and hot tap water samples from 18 houses equipped with conventional water heaters or on‐demand, tankless heaters. The houses were served by a western Massachusetts water system. On‐demand heating without long‐term storage of hot water resulted in little or no change in DBP formation. In contrast, the research indicated that long‐term storage could lead to an increase in trihalomethanes, haloacetic acid, and chloropicrin, whereas the concentrations of dichloroacetonitrile and trichloropropane resulted from competition and decomposition. In the bench‐scale study for this article, laboratory incubation and different heating scenarios (short‐term and long‐term) were tested to confirm the effect of stagnation and high temperature on DBP concentrations in different types of heaters.

Seasonal evaluation of the presence of 46 disinfection by-products throughout a drinking water treatment plant

In this work, we studied a total of 46 regulated and non-regulated disinfection by-products (DBPs) including 10 trihalomethanes (THMs), 13 haloacetic acids (HAAs), 6 halonitromethanes (HNMs), 6 haloacetonitriles (HANs) and 11 aldehydes at different points in a drinking water treatment plant (DWTP) and its distribution network. Determining an increased number of compounds and using accurate, sensitive analytical methodologies for new DBPs can be useful to overcome some challenges encountered in the comprehensive assessment of the quality and safety of drinking water. This paper provides a detailed picture of the spatial and seasonal variability of DBP concentrations from raw water to distribution network. Samples were collected on a monthly basis at seven different points in the four seasons of a year to acquire robust data for DBPs and supplementary quality-related water parameters. Only 5 aldehydes and 2 HAAs were found in raw water. Chlorine dioxide caused the formation of 3 new aldehydes (benzaldehyde included), 5 HAAs and chloroform. The concentrations of DBPs present in raw water were up to 6 times higher in the warmer seasons (spring and summer). The sedimentation process further increased their concentrations and caused the formation of three new ones. Sand filtration substantially removed aldehydes and HAAs (15–50%), but increased the levels of THMs, HNMs and HANs by up to 70%. Chloramination raised the levels of 8 aldehydes and 7 HAAs; also, it caused the formation of monoiodoacetic acid, dibromochloromethane, dichloroiodomethane and bromochloroacetonitrile. Therefore, this treatment increases the levels of existing DBPs and leads to the formation of new ones to a greater extent than does chlorine dioxide. Except for 5 aldehydes, the 23 DBPs encountered at the DWTP exit were found at increased concentrations in the warmer seasons (HAAs by about 50% and THMs by 350%).

NOM removal: evaluating five process alternatives to alum coagulation

Bench-scale experiments were conducted to evaluate disinfection by-product (DBP) precursor removal by coagulation with alum and ferric sulfate (FS), intermediate ozonation (IO 3 ), powdered-activated carbon (PAC), ion exchange resin (IX), and spiral-wound nanofiltration (NF). The effect of source water quality on process performance was also assessed on six source waters. Overall, NF offered the best performance in terms of dissolved organic carbon (DOC) removals along with lower DBP concentrations in every tested condition except for DOC-rich waters (13–15 mg/L). Conventional treatment coupled with recirculated PAC adsorption (Actiflo ® Carb) was the process configuration providing the most consistently low DOC (less than 2 mg/L), facilitating DBP regulation compliance. IX/alum and alum/IO 3 reduced DBP concentration to a lesser extent, but proved to be more efficient than conventional treatment with alum alone. In terms of effluent DBP concentration, FS outperformed alum at higher coagulant dosages, whereas alum offered a superior performance at lower dosages. Finally, this investigation shows the relevance of conducting treatability assays to identify the most suitable treatment alternative for DBP control.

Disparity in disinfection byproducts concentration between hot and cold tap water

The quality of water entering a distribution system may differ substantially from the quality at the point of exposure to the consumer. This study investigated temporal variations in the levels of regulated and non-regulated disinfection byproducts (DBPs) in cold and hot tap water in a home on a medium-sized municipal water system. In addition, samples were collected directly from the water plant with some being held in accordance with a simulated distribution system (SDS) test protocol. The location for this work was a system in western Massachusetts, USA that uses free chlorine as a final disinfectant. Very little short term variability of DBPs at the point of entry (POE) was observed. The concentration of DBPs in the time-variable SDS test was similar to concentrations in the cold water tap. For most DBPs, the concentrations continued to increase as the cold water tap sample was held for the time-variable SDS incubation period. However, the impact of heating on DBP levels was compound specific. For example, the concentrations of trihalomethanes (THMs), dichloroacetic acid (DCAA) and chloropicrin (CP) were substantially higher in the hot water tap than in the cold water time-variable SDS samples. In contrast, the concentration of trichloroacetic acid (TCAA) was lower in the heated hot tap water, but about equal to that observed in the cold tap water. The situation was more pronounced for dichloroacetonitrile (DCAN), bromodichloroacetic acid (BDCAA), bromochloroacetic acid (BCAA) and 1,1,1-trichloropropanone (TCP), which all showed lower concentrations in the hot water then in either of the cold water samples (instantaneous or time-variable SDS). The latter was viewed as a clear indication of thermally-induced decomposition. The ratio of unknown total organic halide (UTOX) to TOX was substantially lower in the hot tap water as the THM to TOX ratio became correspondingly larger. The results of this study show that DBP exposure in the home is not well represented by concentrations measured in cold water taps where most compliance monitoring is done.

A comparison of membership function shapes in a fuzzy-based fugacity model for disinfection byproducts in indoor swimming pools

Aleatory and epistemic uncertainty in human health risk assessment is virtually unavoidable. While probabilistic methods may adequately address exposure and risk model parameters with variability (body weight, exposure duration, exposure frequency), other methods are more helpful for handling uncertainty that arises from an incomplete understanding of the processes being modeled (mass transport). Due to the potential for cancer and other health risks, it is essential to understand of the concentrations of disinfection byproducts in swimming pool facilities and the related exposures. This study builds on previous probabilistic and fuzzy based fugacity models which estimate exposure to disinfection byproducts in swimming pools (Dyck, Water Res 45:5084–5098, 2011; Annual meeting of the North American Fuzzy Information Processing Society (NAFIPS), 2012). Those models estimated environmental concentrations based on mass transfer processes for which there are many possible formulas. The influence of membership function shape on the final estimated concentration required further investigation. In this study, three different trapezoidal membership functions are derived for the gas-side mass transfer coefficient k G . One triangular and one trapezoidal membership function are derived for the liquid-side mass transfer coefficient, k L . According to graphical output and percent difference between the actual concentration and the defuzzified output of the fuzzy based model, the best combination of shapes to use is the trapezoidal k G membership function which uses seven calculated values (to define the shape of the trapezoid) with either the triangular or trapezoidal k L membership function. Further study is recommended to combine the fuzzy based methods for poorly understood model processes with probabilistic methods for model parameters with aleatory uncertainty.

Birth Defects and Disinfection By-Product Exposures and Source Water

Previous epidemiological studies suggest that women exposed to disinfection byproducts have an increased risk of delivering babies with neural tube, genitourinary system, and ventricular septal defects. The risk of birth defects (n=3,500) among all live births from 275 towns in Massachusetts was examined relative to different water sources, disinfection types, and disinfection byproduct concentrations using 2000 to 2004 data. Preliminary unadjusted and adjusted results for combined birth defects were largely null among the water source and disinfection exposure metrics. Adjusted odds ratios (aORs) ranged from 1.17 to 1.37 for obstructive urinary defects among births linked to drinking water treated with chlorine, chloramines, and other alternative disinfectants compared to untreated ground water systems. Compared to untreated ground water, increased aORs for cardiac defects were noted for chlorinated surface water (1.14; 95%CI=0.92, 1.41) and chloraminated water (1.08; 95%CI=0.88, 1.33). Increased aORs for hypospadias and epispadias were found for chlorinated surface water (1.19; 95%CI=0.80, 1.78) and chloraminated water (1.17; 95%CI=0.79, 1.72) compared to untreated ground water. Preliminary analyses showed no increased risk of combined birth defects for total trihalomethane or total haloacetic acid exposures compared to the lowest quintiles. Small increased aORs for ventricular septal defects were detected for the upper two brominated trihalomethane quintiles (aOR range=1.15-1.24), while increased risks for obstructive genitourinary defects were detected for the upper three bromodichloromethane (aOR range=1.10-1.51) and brominated trihalomethane (aOR range=1.61-1.91) quintiles. These preliminary data indicate larger risks for birth defects for brominated disinfection byproducts, but further analyses are needed to confirm these results. The views expressed herein are those of the authors only and do not necessarily reflect the views or policies of the USEPA.