GAC to BAC: Does it make chloraminated drinking water safer?

Biological activated carbon (BAC) is widely used as a polishing step at full-scale drinking water plants to remove taste and odor compounds and assimilable organic carbon. BAC, especially with pre-ozonation, has been previously studied to control regulated disinfection by-products (DBPs) and DBP precursors. However, most previous studies only include regulated or a limited number of unregulated DBPs. This study explored two full-scale drinking water plants that use pre-chloramination followed by BAC and chloramine as the final disinfectant. While chloramine generally produces lower concentrations of regulated DBPs, it may form increased levels of unregulated nitrogenous and iodinated DBPs. We evaluated 71 DBPs from ten DBP classes including haloacetonitriles, haloacetamides, halonitromethanes, haloacetaldehydes, haloketones, iodinated acetic acids, iodinated trihalomethanes, nitrosamines, trihalomethanes, and haloacetic acids, along with speciated total organic halogen (total organic chlorine, bromine and iodine) across six different BAC filters of increasing age. Most preformed DBPs were well removed by BAC with different ages (i.e., operation times). However, some preformed DBPs were poorly removed or increased following treatment with BAC, including chloroacetaldehyde, dichloronitromethane, bromodichloronitromethane, N-nitrosodimethylamine, dibromochloromethane, tribromomethane, dibromochloroacetic acid, and tribromoacetic acid. Some compounds, including dibromoacetaldehyde, bromochloroacetamide, and dibromoacetamide, were formed only after treatment with BAC. Total organic halogen removal was variable in both plants and increases in TOCl or TOI were observable on one occasion at each plant. While calculated genotoxicity decreased in all filters, decreases in overall DBP formation did not correlate with decreases in calculated cytotoxicity. In three of the six filters, calculated toxicity increased by 4-27%. These results highlight that DBP concentration alone may not always provide an adequate basis for risk assessment.

Analysis of Cumulative Cancer Risk Associated with Disinfection Byproducts in United States Drinking Water

Hundreds of different disinfection byproducts form in drinking water following necessary treatment with chlorine and other disinfectants, and many of those byproducts can damage DNA and increase the risk of cancer. This study offers the first side-by-side comparison of cancer risk assessments based on toxicological and epidemiological studies of disinfection byproducts using a comprehensive contaminant occurrence dataset for haloacetic acids and trihalomethanes, two groups of disinfection byproducts that are regulated in drinking water. We also provide the first analysis of a new occurrence dataset for unregulated haloacetic acids that became available from the latest, fourth round of the U.S. EPA-mandated unregulated contaminant monitoring program (UCMR4). A toxicological assessment indicated that haloacetic acids, and in particular brominated haloacetic acids, are more carcinogenic and are associated with a greater number of attributable cancer cases than trihalomethanes. Based on the toxicological analysis, cumulative lifetime cancer risk due to exposure to trihalomethanes and haloacetic acids for community water systems monitored under UCMR4, estimated with standard default parameters for body weight and water intake, corresponds to 7.0 × 10-5 (3.5 × 10-5-1.3 × 10-4). The same analysis conducted with age sensitivity factors to account for elevated risk in infants and children yielded a cumulative risk estimate of 2.9 × 10-4 (1.7 × 10-4-6.2 × 10-4). Epidemiological data suggest that lifetime cancer risk from disinfection byproducts for the U.S. population served by community water systems is approximately 3.0 × 10-3 (2.1 × 10-4-5.7 × 10-3), or a lifetime cancer risk of three cases per thousand people. Overall, this analysis highlights the value of using human data in health risk assessments to the greatest extent possible.

Low toxicological impact of wastewaters on drinking water sources

Surface waters may contain varying levels of wastewater effluent associated with de facto reuse, which may influence their toxicological properties both prior to and following treatment. This study examined the genotoxic response of three surface waters containing a range of wastewater effluent (5%, 10%, and 25% by volume). The SOS Chromotest™ was used to assay the genotoxicity of both chlorinated and unchlorinated mixtures. Chlorinated mixtures were also analyzed for trihalomethanes (THMs), haloacetonitriles (HANs), and halonitromethanes (HNMs); their concentrations were used to calculate a relative toxicity index for each sample, based on published potencies in the comet assay and subsequently referred to as predicted genotoxicity. Wastewater effluents were observed to be reactive in the genotoxicity assay, whereas raw and chlorinated surface waters were not. Upon chlorination, surface waters containing 5% or 10% wastewater did not elicit a response and only modest effects were observed for higher wastewater ratios (25%). The measured SOS responses correlated well with predicted genotoxicity (R = 0.92) and THM concentrations (R = 0.92). This is important since THMs themselves are non-reactive in either the SOS or comet genotoxic assays, but their formation may serve as surrogates for non-regulated DBPs which drive toxic effects.

Characterization of dissolved organic matter derived from atmospheric dry deposition and its DBP formation

Disinfection by-products (DBPs) precursors can be regarded mainly from the drinking water sources and the water treatment processes. A recent study showed that dissolved organic matter (DOM) in atmosphere is an important precursor source of DBPs through atmospheric wet deposition. However, little information is available on the characteristics of DOM derived from dry deposition particulate matter (PM) and the impact of dry deposition on CX₃R-type DBP formation. This study determined whether dry deposition directly contributed the production of DBPs during chlor (am)ination and investigated the mechanism behind the contribution based on the combination of the resin and membrane for fractionating DOM fractions. The results showed that the hydrophilic fraction (HPI) contributed the most DOM and low molecular weight DOM (<10 kDa) was the main component of HPI. In addition, aromatic proteins and soluble microbial products-like compounds were the dominant fluorescent species in DOM derived from PM, and <10 kDa transphilic was the most abundant. The concentrations of C-DBPs and N-DBPs in disinfected PM solution were trihalomethanes (THMs) > haloacetic acids (HAAs) > haloaldehydes and haloacetamides > haloacetonitriles > halonitromethanes for both chlorination and chloramination. The main contributors of calculated toxicity are transphilic and hydrophobic in chlorination and chloramination respectively. Dry deposition PM was deduced to contribute DOM and DBP formation after chlorination in surface water, especially THMs and HAAs. These results presented herein provide key information for controlling DBPs from the perspectives of atmospheric dry deposition, especially in the case of heavy air pollution.

Disinfection byproducts and halogen-specific total organic halogen speciation in chlorinated source waters - The impact of iopamidol and bromide

This study investigated the speciation of halogen-specific total organic halogen and disinfection byproducts (DBPs) upon chlorination of natural organic matter (NOM) in the presence of iopamidol and bromide (Br^-). Experiments were conducted with low bromide source waters with different NOM characteristics from Northeast Ohio, USA and varied spiked levels of bromide (2-30 μmol/L) and iopamidol (1-5 μmol/L). Iopamidol was found to be a direct precursor to trihalomethane (THM) and haloacetic acid formation, and in the presence of Br^- favored brominated analogs. The concentration and speciation of DBPs formed were impacted by iopamidol and bromide concentrations, as well as the presence of NOM. As iopamidol increased the concentration of iodinated DBPs (iodo-DBPs) and THMs increased. However, as Br^- concentrations increased, the concentrations of non-brominated iodo- and chloro-DBPs decreased while brominated-DBPs increased. Regardless of the concentration of either iopamidol or bromide, bromochloroiodomethane (CHBrClI) was the most predominant iodo-DBP formed except at the lowest bromide concentration studied. At relevant concentrations of iopamidol (1 μmol/L) and bromide (2 μmol/L), significant quantities of highly toxic iodinated and brominated DBPs were formed. However, the rapid oxidation and incorporation of bromide appear to inhibit iodo-DBP formation under conditions relevant to drinking water treatment.

Assessing the potential effect of extreme weather on water quality and disinfection by-product formation using laboratory simulation

Increased frequency and severity of extreme weather events (i.e., floods and droughts) combined with higher temperatures can threaten surface water quality and downstream drinking water production. This study characterized the effects of extreme weather events on dissolved organic matter (DOM) washout from watershed soils and the corresponding contribution to disinfection by-product (DBP) precursors under simulated weather conditions. A laboratory simulation was performed to assess the effects of temperature, drought, rainfall intensity, sea level rise, and acid deposition on the amount of DOM released from soil samples. DBP formation potentials (DBPFPs) were obtained to assess the effect of extreme weather events on DBP formation and drinking water quality. The results demonstrated that the dissolved organic carbon (DOC) and carbonaceous DBP levels increased with increasing temperature in a dry (drought) scenario. Regardless of the watershed from which a soil sample was obtained and the incubation temperature during rewetting or chlorination processes, the DOC and carbonaceous DBP levels also increased with increasing temperature. Brominated DBP formation was increased when bromide was present during the rewetting of soil, indicating the effect of sea level rise. When bromide was present during the chlorination of water for DBPFP tests, only the level of brominated DBPs increased. Acid deposition had various effects under different weather conditions. The results of heavy rainfall simulations suggested that water quality deteriorates at the beginning of an extreme rainfall event. Abundant DOM was washed out of soil, leading to a peak in the DBPFP level. The level of DOM in seepage water was less than that of the surface runoff water during rainfall. The situation was more severe when the rainfall came after a long drought and the drought-rewetting cycle effect occurred.

Comprehensive assessment of the indoor air quality in a chlorinated Olympic-size swimming pool

Elite swimmers and swimming pool employees are likely to be at greater health risk due to their regular and intense exposure to air stressors in the indoor swimming pool environment. Since data on the real long-term exposure is limited, a long-term monitoring and sampling plan (22 non-consecutive days, from March to July 2017) was carried out in an indoor Olympic-size pool with a chlorine-based disinfection method to characterize indoor environments to which people involved in elite swimming and maintenance staff may be exposed to. A comprehensive set of parameters related with comfort and environmental conditions (temperature, relative humidity (RH), carbon dioxide (CO₂) and monoxide and ultrafine particles (UFP)) were monitored both indoors and outdoors in order to determine indoor-to-outdoor (I/O) ratios. Additionally, an analysis of volatile organic compounds (VOC) concentration and its dynamics was implemented in three 1-hr periods: early morning, evening elite swimmers training session and late evening. Samplings were simultaneously carried out in the air layer above the water surface and in the air surrounding the pool, selected to be representative of swimmers and coaches/employees' breathing zones, respectively. The results of this work showed that the indoor climate was very stable in terms of air temperature, RH and CO₂. In terms of the other measured parameters, mean indoor UFP number concentrations (5158 pt/cm³) were about 50% of those measured outdoors whereas chloroform was the predominant substance detected in all samples collected indoors (13.0-369.3 µg/m³), among a varied list of chemical compounds. An I/O non-trihalomethanes (THM) VOC concentration ratio of 2.7 was also found, suggesting that, beyond THM, other potentially hazardous VOC have also their source(s) indoors. THM and non-THM VOC concentration were found to increase consistently during the evening training session and exhibited a significant seasonal pattern. Compared to their coaches, elite swimmers seemed to be exposed via inhalation to significantly higher total THM levels, but to similar concentrations of non-THM VOC, during routine training activities. Regarding swimming employees, the exposure to THM and other VOC appeared to be significantly minimized during the early morning period. The air/water temperature ratio and RH were identified as important parameters that are likely to trigger the transfer processes of volatile substances from water to air and of their accumulation in the indoor environment of the swimming pool, respectively.

Natural and anthropogenic sources of bromoform and dibromomethane in the oceanographic and biogeochemical regime of the subtropical North East Atlantic

The organic bromine compounds bromoform (CHBr₃) and dibromomethane (CH₂Br₂) influence tropospheric chemistry and stratospheric ozone depletion. Their atmospheric abundance is generally related to a common marine source, which is not well characterized. A cruise between the three Macaroenesian Archipelagos of Cape Verde, the Canaries and Madeira revealed that anthropogenic sources increased oceanic CHBr₃ emissions significantly close to some islands, especially at the Canaries, while heterotrophic processes in the ocean increased the flux of CH₂Br₂ from the sea to the atmosphere in the Cape Verde region. As anthropogenic disinfection processes, which release CHBr₃ in coastal areas increase, and as more CH₂Br₂ may be produced from increased heterotrophy in a warming, deoxygenated ocean, both sources could supply higher fractions of stratospheric bromine in the future, with yet unknown consequences for stratospheric ozone.

Dominant formation of unregulated disinfection by-products during electrocoagulation treatment of landfill leachate

During the electrocoagulation (EC) treatment of landfill leachate, the production of chlorine species may result in the formation of harmful disinfection by-products (DBPs). This formation was investigated in the present study by monitoring five classes of DBPs (haloacetic acids-HAA, trihalomethanes-THM, haloacetonitriles-HAN, haloketones-HK, and halonitromethanes-HNM) in two leachate samples treated by EC. It was shown that the applied current has stimulated the formation of DBPs, which were dominated by unregulated DBPs. With a current density of 100 mA cm^-2, the unregulated HK dominated the weight-based DBP concentration (96% in Leachate A and 44.3% in Leachate B), while the unregulated HAN contributed to >80% of the DBP additive toxicity in both leachates. The concentrations of regulated THM and HAA species were below US EPA regulations. The in situ generation of active chlorine has resulted in the DBP formation, as demonstrated in the scavenging test. Applying granular activated carbon as a post-treatment step could successfully reduce the total DBP concentration from 295.33 μg L^-1 to 82.04 μg L^-1 in Leachate A, leading to a total DBP removal of 72.2% and a toxicity removal of 50%. Given the dominant concentration and lack of toxicity information, the unregulated DBPs should receive more attention.

Formation and removal of disinfection by-products in a full scale drinking water treatment plant

In this case study, high sensitivity simple methods for the analysis of trihalomethanes (THM4), iodinated-trihalomethanes (I-THMs), haloacetic acids (HAAs), bromide, iodide and iodate have been developed. A one-step procedure for the analysis of haloacetic acids by head-space GC-MS provides good reproducibility and low limits of quantification (≤50 ng L^-1). These methods were applied to characterize the formation of disinfection by-products (DBPs) in a full scale drinking water treatment plant. In this treatment plant, the incorporation of bromine into THMs increases throughout the water treatment line, due to the formation of bromine reactive species favored by the decrease of competition between dissolved organic carbon (DOC) and bromide towards chlorine. A linear correlation has been observed between the bromine incorporation factor and the Br^-/DOC mass ratio. The conversion of iodine to iodate by chlorination occurs in this water due to the relatively high bromide concentration. Moreover, a higher formation of iodate compared to iodide levels in the raw water is observed indicating a degradation of organic iodinated compounds. The formation of I-THMs was constant in terms of quantity and speciation between campaigns despite fluctuating concentrations of DOC and total iodine in the raw water. A preferential removal of DBPs formed by the intermediate chlorination in the order I-DBPs > Br-DBPs > Cl-DBPs occurs during the subsequent activated carbon filtration. The removal rates range from 25 to 36% for the regulated THM4, from 82 to 93% for the ∑I-THMs and 95% for haloacetic acids. The assessment of the relative toxicity shows that despite a much lower concentration of HAAs (<10% of the total mass of measured DBPs) compared to THMs, these compounds are responsible for 75% of the relative cytotoxicity of the treated water. Bromoacetic acid on its own accounts for more than 60% of the overall toxicity of the 17 compounds included in this study.

Advanced treatment of urban wastewater by UV-C/free chlorine process: Micro-pollutants removal and effect of UV-C radiation on trihalomethanes formation

The effect of the UV-C/free chlorine (FC) process on the removal of contaminants of emerging concern (CECs) from real urban wastewater as well as the effect of UV-C radiation on the formation of trihalomethanes (THMs) compared to FC process alone was investigated. Unlike of FC process, UV-C/FC was really effective in the degradation of the target CECs (carbamazepine (CBZ), diclofenac, sulfamethoxazole and imidacloprid) in real wastewater (87% degradation of total CECs within 60 min, Q_UVC = 1.33 kJ L^-1), being CBZ the most refractory one (49.5%, after 60 min). The UV-C radiation significantly affected the formation of THMs. THMs concentration (mainly chloroform) was lower in UV-C/FC process after 30 min treatment (<1 μgL^-1 = limit of quantification (LOQ)) than in FC process in dark (2.3 μgL^-1). Noteworthy, while in FC treated wastewater chloroform concentration increased after treatment, UV-C/FC process resulted in a significant decrease (residual concentrations below the LOQ), even after 24 h and 48 h post-treatment incubation. The formation of radicals due to UV-C/FC process can reduce THMs compared to chlorination process, because part of FC reacts with UV-C radiation to form radicals and it is no longer available to form THMs. These results are encouraging in terms of possible use of UV-C/FC process as advanced treatment of urban wastewater even for possible effluent reuse.

Comparison of the yields of mono-, Di- and tri-chlorinated HAAs and THMs in chlorination and chloramination based on experimental and quantum-chemical data

Thermodynamic and kinetic aspects of the formation of trihalomethanes and haloacetic acids determined based on the quantum chemical (QC) simulations were compared in this study with the experimental data generated using the differential spectroscopy approach in chlorination and chloramination. The ratios of the slopes of the correlations between -DlnA₃₅₀ values and individual DBPs concentrations (S_NH2Cl/S_HOCl) were observed to be linearly correlated with the ratios of the Gibbs free energies (ΔG_NH2Cl/ΔG_HOCl) of the corresponding reactions of chloramine and chlorine with acetaldehyde which was used as a model DBP precursor in QC simulations. Further QC examination of the kinetics of chlorination and chloramination of the model compound acetoacetic acid showed that the activation energy of reactions between monochloramine that directly participates in substitution reactions to form mono-, di and tri-halogenated intermediates are 2-3 times higher than those of HOCl formed via the hydrolysis monochloramine. This result confirms that the interactions of chloramine with NOM and ensuing DBP formation are primarily mediated by the free chlorine released as a result of the hydrolysis of monochloramine while direct halogenation of NOM by monochloramine is likely to provide a small contribution to DBP formation.

Application of stabilized hypobromite for controlling membrane fouling and N-nitrosodimethylamine formation

Chloramination is a conventional and successful pre-disinfection approach to control biological fouling for reverse osmosis (RO) treatment in water reuse. This study aimed to evaluate the possibility of using a new disinfectant-stabilized hypobromite-in controlling membrane fouling and the formation of a particular carcinogenic disinfection byproduct (DBP)-N-nitrosodimethylamine (NDMA). Our accelerated chemical exposure tests showed that the new disinfectant reduced the permeability of a polyamide RO membrane permeability from 6.7 to 4.1 L/m²hbar; however, its treatment impact was equivalent to that of chloramine. The disinfection efficacy of stabilized hypobromite was greater than that of chloramine when evaluated with intact bacterial counts, which suggests its potential for mitigating membrane biofouling. Additional pilot-scale tests using synthetic wastewater demonstrated that pre-disinfection with the use of stabilized hypobromite inhibits membrane fouling. Among 13 halogenated DBPs evaluated, the formation of bromoform by stabilized hypobromite was higher than that by chloramine at a high dose of 10 mg/L, thus suggesting the need for optimizing chemical doses for achieving sufficient biofouling mitigation. NDMA formation upon stabilized hypobromite treatment in two different types of actual treated wastewaters was found to be negligible and considerably lower than that by chloramine treatment. In addition, NDMA formation potential by stabilized hypobromite was 2-5 orders of magnitude lower than that by chloramine. Our findings suggest the potential of using stabilized hypobromite for controlling NDMA formation and biofouling, which are the keys to successful potable water reuse.

Synergistic effects of quenching agents and pH on the stability of regulated and unregulated disinfection by-products for drinking water quality monitoring

Quenching agents (QAs) are widely used in order to prevent the additional formation of disinfection by-products (DBPs) during the sample holding time. In addition, DBP levels are usually stabilized by adjusting the pH of water samples. Previous studies have mostly focused on the individual effects of QAs or of pH on the stability of DBPs in water samples. Considering that disinfectant quenching and pH adjustments are applied simultaneously during routine analyses, it is more appropriate to evaluate the stability of DBPs with all the chemicals (e.g., disinfectants, QAs, buffers) present in the water. This study investigated the synergistic effects of different QAs (ascorbic acid, ammonium chloride, or no quenching) and pH adjustment (3-9) strategies on the stability of different classes of DBPs (i.e., trihalomethanes (THMs), halogenated acetaldehydes (HALs), haloacetonitriles (HANs), haloketones (HKs), and halonitromethane (HNM)). Sample preservation conditions that did not include a QA were shown to be inadequate for GC-ECD analysis, due to interference problems. Ammonium chloride was found to be effective for most DBPs. However, some HALs continued to form in the presence of chloramine, which is a by-product of dechlorination using ammonium chloride. Conversely, using ascorbic acid efficiently inactivated residual chlorine, providing a clean chromatographic baseline. Based on the results of this study, we recommend the use of ascorbic acid for quenching and sulfuric acid for acidifying (pH 3.5) samples. Considering the instability of some DBPs in water matrices over long periods (i.e., 14 days), samples should be processed as soon as possible after collection.

Modeling Trihalomethane Increases Associated with Source Water Bromide Contributed by Coal-Fired Power Plants in the Monongahela River Basin

Increases in source water bromide concentrations are challenging for drinking water utilities since bromide contributes to the formation of disinfection byproducts (DBPs) that have negative human-health effects. The present work evaluates the role of coal-fired power plant wet flue gas desulfurization (FGD)-associated bromide loads on in-stream bromide concentrations in the Monongahela River Basin in the water year (WY) 1998 (during a nationwide study) and over a five-year period from WYs 2013 through 2017. Under mean flow conditions in the lower Monongahela River for the WYs of interest, the median-estimated wet FGD bromide discharges are modeled to represent a significant fraction (27-57%) of observed bromide concentrations with the range representing the change in load conditions across WYs. Seasonal effects are predicted due to changes in the dilution capacity of the river with elevated concentrations under lower flows in the third and fourth quarters (July through December). The effect of these bromide concentration contributions, which range from 6.8 to 23 μg/L under median load estimates and median flow conditions, on trihalomethane (THM) formation and associated risk were assessed. A simple model was applied to demonstrate an analytical approach for evaluating the power plant total THM (TTHM) and risk contributions. Utilizing this model, the power plant TTHM contribution was estimated to range from 7.6 to 27 μg/L with a median risk contribution of 0.0014.

Factors Associated with Exposure to Trihalomethanes, NHANES 2001-2012

Disinfection is critical for maintaining a safe water supply, but the use of chlorine or chloramine leads to exposure to disinfection byproducts (DBPs), including trihalomethanes (THMs), which have been associated with adverse reproductive outcomes and bladder cancer. The U.S. Environmental Protection Agency revised the DBP regulations starting in 1998 to further limit levels of THMs in household water. We analyzed data from the National Health and Nutrition Examination Survey (NHANES) collected between 2001 and 2012 (with 2 years per cycle) using models with and without water-related predictors to examine the utility of including these measures. Median blood chloroform levels (25th-75th percentiles) were 16.2 (9.13-31.2) ng/L in 2001-2002 and 5.97 (2.92-12.3) ng/L in 2011-2012. Median blood bromodichloromethane (BDCM) levels (25th-75th percentiles) were 2.22 (1.06-4.61) ng/L in 2001-2002 and 1.18 (<limit of detection-2.92) ng/L in 2011-2012. THM water concentrations and measures of the recency since time spent in water use activities were associated with blood THM levels. Being in a pool/hot tub/sauna within 24 h or taking a shower/bath within 6 h of blood collection was associated with elevated blood levels of chloroform and BDCM. When possible, it is important to include recency and external dose when assessing associations to internal dose levels for nonpersistent compounds.

The use of peracetic acid for estrogen removal from urban wastewaters: E2 as a case study

17β-Estradiol (E2) is a natural estrogen produced by the feminine endocrine system. It is excreted mainly through urine and feces. Exposure to E2 may affect the reproductive system of both animals and humans, especially since the removal of E2 in conventional processes and technologies present in the wastewater treatment plants is not sufficient. Chlorine is one of the most studied and used oxidant worldwide. Although there are studies that demonstrate the endocrine disrupting compounds removal like E2, its reaction with organic matter can originate by-products, namely, trihalomethanes, which are known to have high toxic potential. The main aim of the present study was to evaluate the removal of E2 (50 μg E2 L^-1-maximum concentration) using peracetic acid (PAA), a seeming cleaner and innocuous alternative to chlorine. To this end, a series of jar tests were performed, using different peracetic acid concentrations (1, 5, 10, and 15 mg L^-1) and contact times (10, 15, and 20 min). The results obtained showed that a peracetic acid concentration of 15 mg L^-1 with a contact time of 20 min had a removal efficacy of approximately 100%. The second main goal of this study was to evaluate the ecotoxicological potential of the tested treatments on the zebrafish Danio rerio. Several oxidative stress biomarkers were evaluated, namely glutathione S-transferase, lipid peroxidation, and catalase, besides vitellogenin. Both peracetic acid and E2 caused significant increases in the oxidative stress biomarkers, although this did not lead to increased lipid peroxidation levels. In addition, peracetic acid significantly decreased the estrogenic activity of E2, as indicated by decreased vitellogenin levels. Peracetic acid demonstrated to have great potential as an alternative disinfectant for chlorine treatments, and indications for future research are discussed.

Trihalomethanes in Drinking Water and Bladder Cancer Burden in the European Union

BACKGROUND

Trihalomethanes (THMs) are widespread disinfection by-products (DBPs) in drinking water, and long-term exposure has been consistently associated with increased bladder cancer risk.

OBJECTIVE

We assessed THM levels in drinking water in the European Union as a marker of DBP exposure and estimated the attributable burden of bladder cancer.

METHODS

We collected recent annual mean THM levels in municipal drinking water in 28 European countries (EU28) from routine monitoring records. We estimated a linear exposure-response function for average residential THM levels and bladder cancer by pooling data from studies included in the largest international pooled analysis published to date in order to estimate odds ratios (ORs) for bladder cancer associated with the mean THM level in each country (relative to no exposure), population-attributable fraction (PAF), and number of attributable bladder cancer cases in different scenarios using incidence rates and population from the Global Burden of Disease study of 2016.

RESULTS

We obtained 2005-2018 THM data from EU26, covering 75% of the population. Data coverage and accuracy were heterogeneous among countries. The estimated population-weighted mean THM level was 11.7μg/L [standard deviation (SD) of 11.2]. The estimated bladder cancer PAF was 4.9% [95% confidence interval (CI): 2.5, 7.1] overall (range: 0-23%), accounting for 6,561 (95% CI: 3,389, 9,537) bladder cancer cases per year. Denmark and the Netherlands had the lowest PAF (0.0% each), while Cyprus (23.2%), Malta (17.9%), and Ireland (17.2%) had the highest among EU26. In the scenario where no country would exceed the current EU mean, 2,868 (95% CI: 1,522, 4,060; 43%) annual attributable bladder cancer cases could potentially be avoided.

DISCUSSION

Efforts have been made to reduce THM levels in the European Union. However, assuming a causal association, current levels in certain countries still could lead to a considerable burden of bladder cancer that could potentially be avoided by optimizing water treatment, disinfection, and distribution practices, among other possible measures. https://doi.org/10.1289/EHP4495.

Using UV/H2O2 pre-oxidation combined with an optimised disinfection scenario to control CX3R-type disinfection by-product formation

The effects of UV/H₂O₂ pre-oxidation or disinfection methods on the formation of partial disinfection by-products (DBPs) have been studied previously. This study assessed the effect of UV/H₂O₂ pre-oxidation combined with optimisation of the disinfection method on the formation of six classes of CX₃R-type DBPs, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetaldehydes (HALs), haloacetonitriles (HANs), halonitromethanes (HNMs), and haloacetamides (HAMs). Experimental results showed that a simulated distribution system (SDS) in-situ chloramination or pre-chlorination followed by chloramination effectively decreased total CX₃R-type DBP formation by 51.1-63.5% compared to SDS chlorination, but little reduction in DBP-associated toxicity was observed. The dominant contributors to the calculated toxicity were HANs and HALs. UV/H₂O₂ pre-oxidation was able to destroy the aromatic and dissolved organic nitrogen components of natural organic matter. As a consequence, THM, HAA, and HAL formations increased by 49.5-55.0%, 47.8-61.9%, and 42.0-67.1%, respectively, whereas HAN, HNM, and HAM formations significantly decreased by 52.1-83.6%, 42.9-87.3%, and 74.1-100.0%. UV/H₂O₂ pre-oxidation increased total CX₃R-type DBP formation, during SDS chlorination, whereas SDS in-situ chloramination or pre-chlorination followed by chloramination of UV/H₂O₂-treated water produced lower total CX₃R-type DBPs than water without UV/H₂O₂ pre-oxidation. Nevertheless, the DBP-associated toxicity of water with UV/H₂O₂ pre-oxidation was substantially lower than the toxicity for water without UV/H₂O₂ pre-oxidation, decreased by 24.1-82.7%. HALs followed by HANs contribute to major toxic potencies in UV/H₂O₂ treated water. The best DBP concentration and DBP-associated toxicity abatement results were achieved for water treated by UV/H₂O₂ coupled with in-situ chloramination treatment.

Evidence-based analysis on the toxicity of disinfection byproducts in vivo and in vitro for disinfection selection

Disinfection is a key step in drinking water treatment process to prevent water-borne infections. However, reactions between chlorine, one of the most common disinfectants, and natural organic matter (NOM) often lead to the formation of hazardous disinfection byproducts (DBPs). However, the cytotoxicity of some DBPs is still poorly understood. Such knowledge is critical for proper selection of disinfection processes. We investigated the effects of DBPs on mouse acute liver injury. The exacerbation of liver damage increased with the DBPs concentrations, likely due to the increased hepatic macrophages. Haloacetonitriles (HANs) and haloketones (HKs) are more toxic to Human Hepatocellular (Hep3B) cells than trihalomethanes (THMs). Cytotoxicity of DBPs were governed by the halogen type (brominated DBPs > chlorinated DBPs) and the numbers of halogen atoms per molecule. Then, we used the pilot-scale WDS to study the best conditions for reducing the formation of DBPs. The result showed that the formation of DBPs followed the order: stainless-steel (SS) > ductile iron (DI) > polyethylene (PE) pipe. Higher flowrate promoted the formation of DBPs in all three pipes. The results suggest that the formation of DBPs in chlorine disinfection can be reduced by using PE pipes and low flow rate in water distribution systems (WDS).

Assessment of the chlorine demand and disinfection byproduct formation potential of surface waters via satellite remote sensing

The ability of satellites to assess surface water quality indicators such as colored dissolved organic matter (CDOM) suggests that remote sensing could be a useful tool for evaluating water treatability metrics in considering potential drinking water supplies. To explore this possibility, 24 surface water samples were collected throughout Minnesota, USA with wide ranging values of CDOM (a₄₄₀; 0.41-27.9 m^-1), dissolved organic carbon (DOC; 5.5-47.6 mg/L) and specific ultraviolet absorbance at 254 nm (SUVA₂₅₄; 1.3-5.1 L/mg-M). Laboratory experiments were performed to quantify chlorine demand and the formation of two classes of halogenated disinfection byproducts (DBPs), trihalomethanes (THMs) and haloacetic acids (HAAs), using the uniform formation conditions (UFC) test. Chlorine demand and THM_UFC were linearly correlated with CDOM (R² = 0.97 and 0.91, respectively), indicating that CDOM is a useful predictor of these parameters. On the other hand, data comparing di- and tri-HAA_UFC with CDOM were better fit by a logarithmic relationship (R² = 0.73 and 0.87, respectively), while mono-HAA_UFC was linearly correlated with CDOM (R² = 0.46) but only for low-to moderately-colored waters (a₄₄₀ ≤ 11 m^-1). The correlations relating chlorine demand and DBP_UFC values with CDOM were coupled with satellite CDOM assessments to estimate chlorine demand and DBP_UFC values for all surface waters larger than 0.05 km² in the state of Minnesota, USA. The resulting maps suggest that only 21.8% of Minnesota lakes would meet both the THM and HAA maximum contaminant levels, but only when pre-disinfection treatment removes 75% of DBP precursors. There are limitations to determining CDOM using satellites for high color surface waters (a₄₄₀ > 11 m^-1), however, leading to underpredicted values for CDOM, chlorine demand, and DBP_UFC. Overall, the results demonstrate the potential benefits of satellite remote sensing for assessing potential drinking water sources and water treatability metrics.

Disinfection Byproducts in Rajasthan, India: Are Trihalomethanes a Sufficient Indicator of Disinfection Byproduct Exposure in Low-Income Countries?

The implementation of chlorine disinfection in low-income countries reduces the risk of waterborne illness but initiates exposure to disinfection byproducts (DBPs). Like high-income countries, low-income countries typically are adopting regulations focusing on trihalomethanes (THM4) as an indicator of overall DBP exposure. However, the use of impaired water sources can decouple the formation of THM4 from other DBP classes that are more potent toxins. The documentation of DBP species other than THM4 is rare in low-income countries, where water sources may be degraded by inadequate sanitation infrastructure and other uncontrolled wastewater discharges. We measured THM4 and 21 unregulated DBPs in tap waters and laboratory-treated source waters from two cities in northwestern India. The contribution of each DBP class to the cumulative toxicity was estimated by weighting each species by metrics of toxic potency; haloacetonitriles typically were the dominant contributor, while the contribution of THM4 was negligible. THM4 concentrations did not correlate with the total toxic potency-weighted DBP concentrations. Although THM4 rarely exceeded international guidelines, DBPs of greater toxicological concern were observed in high concentrations. The total toxic potency-weighted DBP concentrations in some waters were elevated compared to conventional drinking waters in high-income countries and more closely resembled chlorine-disinfected wastewater effluents. Artificial sweeteners confirmed widespread contamination of both surface and groundwaters by domestic sewage. The results suggest that THM4 may not be an adequate indicator of overall DBP exposure in impaired water supplies prevalent in some low-income nations.

Urinary Biomarker of Prenatal Exposure to Disinfection Byproducts, Maternal Genetic Polymorphisms in CYP2E1 and GSTZ1, and Birth Outcomes

The effects of disinfection byproducts (DBPs) on adverse birth outcomes remain unsettled. Maternal genetic variants in relation to DBP metabolism may modify this effect. Pregnant women during late pregnancy (n = 1306) were included from a Chinese cohort. Maternal urinary trichloroacetic acid (TCAA) was measured as a biomarker of DBP exposure. Maternal genotyping was conducted in cytochrome P450 2E1 (CYP2E1; rs2031920, rs3813867, and rs915906) and glutathione S-transferase zeta-1 (GSTZ1; rs7975). The associations between maternal urinary TCAA and birth outcomes and statistical interactions between maternal exposure and genetic polymorphisms were estimated. We found that maternal urinary TCAA levels were associated with decreased birth weight (P for trend = 0.003) and ponderal index (P for trend = 0.004). Interaction analyses showed that maternal urinary TCAA in association with decreased birth weight was observed only among subjects with CYP2E1 rs3813867 GC/CC versus GG (P_int = 0.07) and associations with decreased birth length, ponderal index, and gestational age were observed only among subjects with GSTZ1 rs7975 GA/AA versus GG (P_int = 0.07, 0.02, and 0.02, respectively). Our results suggested that prenatal DBP exposure was negatively associated with birth weight and ponderal index, and maternal genetic polymorphisms in CYP2E1 and GSTZ1 might modify these associations.

Formation of iodinated trihalomethanes and noniodinated disinfection byproducts during chloramination of algal organic matter extracted from Microcystis aeruginosa

The increasing occurrence of harmful algal blooms in surface waters may increase the input of algal organic matter (AOM) to the dissolved organic matter pool. The formation of iodinated trihalomethanes (I-THMs) and noniodinated disinfection byproducts (DBPs) in synthetic waters containing AOM extracted from Microcystis aeruginosa was investigated in chloramination (preformed and in-situ formed chloramine, NH₂Cl and Cl₂-NH₂Cl, respectively) and chlorination (Cl₂) processes. AOM is much more favorable for iodine incorporation than natural organic matter (NOM). For example, the formation of I-THM from AOM is much higher than NOM isolate extracted from treated water (e.g., 3.5 times higher in the NH₂Cl process), and thus higher iodine utilization and substitution factors from AOM were observed. Short contact time (2 min) chlorination in Cl₂-NH₂Cl process leading to the formation of halogenated intermediates favored I-THM formation, compared with NH₂Cl process. However, further increasing chlorine contact time from 5 min to 24 h facilitated the conversion from iodide to iodate and thus I-THM formation decreased. Meanwhile, the formation of noniodinated THM4, haloacetonitriles (HANs), and haloacetaldehydes (HALs) increased. Factors including concentrations of AOM and bromide, pH, and chlorine/nitrogen ratios influenced the formation of I-THMs and noniodinated DBPs. To evaluate the benefit of mitigating I-THM formation over the risk of noniodinated DBP formation, measured DBPs were weighed against their mammalian cell toxicity indexes. Increasing the chlorine exposure increased the calculated cytotoxicity based on concentrations of measured I-THMs and noniodinated DBPs since unregulated HANs and HALs were the controlling agents.

Integrated control of CX3R-type DBP formation by coupling thermally activated persulfate pre-oxidation and chloramination

The alternative disinfectant chloramine can lower the formation of carbonaceous DBPs (C-DBPs) but promote the formation of nitrogenous DBPs (N-DBPs), which are more cytotoxic and genotoxic. In this study, the combination of thermally activated persulfate pre-oxidation and post-chloramination (TA/PS-NH₂Cl) was proposed to control the formation and reduce the toxicity of both C-DBPs and N-DBPs. The formation, speciation and toxicity of trihalomethanes, haloacetic acids, haloaldehydes, haloacetonitriles, halonitromethanes and haloacetamides, collectively defined as CX₃R-type DBPs, under TA/PS-NH₂Cl process were compared with processes of chlorination alone (Cl₂), chloramination alone (NH₂Cl) and coupled thermally activated persulfate pre-oxidation with post-chlorination (TA/PS-Cl₂). Results showed that chloramination could reduce formation of C-DBPs and total organic halogen (TOX) while increase N-DBP formation, and the introduction of TA/PS pretreatment process slightly increased the formation of C-DBPs and TOX but sharply reduced the formation of N-DBPs with higher toxicity as well as brominated CX₃R-type DBPs that are more toxic than their chlorinated analogues. By comprehensive toxicity calculation, an outright decline of both cytotoxicity and genotoxicity risk of CX₃R-type DBPs was observed during TA/PS-NH₂Cl process compared with Cl₂, NH₂Cl, and TA/PS-Cl₂ processes. In summary, TA/PS-NH₂Cl process was a potential effective method for integrally controlling the formation of CX₃R-type DBPs and their toxicity and is suggested to be used to treat raw waters containing no bromide or low levels of bromide considering bromate caused by TA/PS pre-oxidation. The study may provide a feasible and economical method for DBP control on the background of global warming.