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ABSTRACT: Disinfection byproducts (DBPs), residual compounds formed from the chemical disinfection of drinking water, can cause a host of damaging public health and environmental impacts. This study evaluates the landscape of regulations designed to reduce the occurrence and/or impact of DBPs, focusing on regulations issued by the US states. Drawing on a systematic search of state administrative codes and agency websites, we first identify the presence, absence, and layering of DBP-related regulations. We then evaluate the number and types of policy tools – the specific approaches required by each regulation, such as monitoring requirements, economic incentives, and required treatment technologies – to identify how DBPs are being managed and how states cluster with relatively more and less robust regulatory frameworks. Finally, we evaluate the relationship between the regulatory approach and the frequency of drinking water quality violations for DBP compounds. While most states have at least one DBP-specific regulation, these vary substantially in their comprehensiveness. The most-used policy tools (monitoring, compliance schedules, and reporting) directly reflect federal regulations; few states have adopted innovative tools such as collaboration or financial incentives. We observe no relationship between regulatory efforts and water quality violations, suggesting that current policy implementation may not adequately address the complex risk of DBPs.

Bezafibrate (BZF), an extensively used lipid-regulating agent, has been frequently detected in aqueous environments. In this work, we systematically investigated the Fe(II)/sulfite process for degrading BZF and its impact on disinfection byproducts (DBPs) during postchlorination. Degradation conditions were optimized by adjusting the pH, sulfite concentration, Fe(II), and BZF concentration. Under the conditions of pH = 4, [BZF]0 = 5 μM, [Fe(II)]0 = 25 μM, and [sulfite]0 = 250 μM, the BZF removal efficiency reaches 97.9% in 15 min. Sulfate radicals (SO4●–) and singlet oxygen (1O2) are recognized as the main reactive agents, with Fe(IV) also contributing to the removal of BZF. Common anions (Cl− and HCO3−) and humic acid generally impede the degradation process, except that trace amounts of Cl− can slightly accelerate BZF degradation. A total of ten products are recognized by ultra high performance liquid chromatography and quadrupole time-of-flight mass spectrometry, and four major degradation pathways are proposed: hydroxylation, cleavage of amino bonds, removal of fibrate chains, and dechlorination. Meanwhile, the toxicity assessment shows that the majority of products exhibit lower biological toxicity and less bioaccumulation potential than BZF itself. The Fe(II)/sulfite pretreatment alters the DBP formation potential, especially when Br− is present. The formation of trichloromethane (TCM) is diminished following pretreatment with the Fe(II)/sulfite process, whereas a noticeable increase in the formation of dichloroacetonitrile (DCAN) is found. Moreover, Fe(II)/sulfite pretreatment enhances the formation of brominated DBPs. Therefore, special consideration should be given to DBP formation when a Fe(II)/sulfite system is employed as a pretreatment for the removal of BZF in water. [ABSTRACT FROM AUTHOR]

Maine is a largely rural state where nearly half of the population uses drinking water from private wells. Arsenic (As) is present in some Maine groundwater, has been linked to cancer, and a lack of testing and treatment may expose people with private wells to elevated As levels. Disinfection byproducts (DBPs) include known and suspected carcinogens that form when chlorine or chloramines are added to water. People served by public water systems may be exposed to elevated levels of regulated DBPs such as trihalomethanes and haloacetic acids associated with chlorine and/or unregulated nitrogenous DBPs, or N-DBPs, such as nitrite and N-nitrosodimethylamine associated with chloramines. Contrary to initial expectations, there were no significant associations between median town As in well water and bladder, lung, kidney, or skin cancer incidence. Furthermore, bladder, melanoma, and other skin cancer incidence rates were negatively correlated with the percent of the town population using private wells. Analysis of cancer incidence associated with chlorine and chloramine disinfection showed elevated melanoma, and other skin cancer with chloramine use and elevated bladder and non-melanoma skin cancer with chlorine use compared to the no disinfectant case. We recommend more research on the links between disinfectant use and cancer. [ABSTRACT FROM AUTHOR]

Emerging contaminants (ECs) have drawn global concern, and the endocrine disrupting chemicals is one of the highly interested ECs categories. However, numerous ECs lacks the basic information about whether they can disturb the endocrine related biomacromolecules or elicit endocrine related detrimental effects on organism. In this study, the potential binding affinity and underlying binding mechanism between 29 ECs from 7 chemical groups and Gobiocypris rarus transthyretin (CrmTTR) are investigated and probed using in vitro and in silico methods. The experimental results demonstrate that 14 selected ECs (11 disinfection byproducts, 1 pharmaceuticals and personal care product, 1 alkylphenol, 1 perfluoroalkyl and polyfluoroalkyl substance) are potential CrmTTR binders. The CrmTTR binding affinity of three ECs (i.e., 2,6-diiodo-4-nitrophenol (logRP(T4) = 0.678 ± 0.198), 2-bromo-6-chloro-4-nitrophenol (logRP(T4) = 0.399 ± 0.0908), tetrachloro-1,4-benzoquinone (logRP(T4) = 0.272 ± 0.0655)) were higher than that of 3,3′,5,5′-tetraiodo-L-thyronine, highlighting that more work should be performed to reveal their potential endocrine related harmful effects on Gobiocypris rarus. Molecular docking results imply that hydrogen bond and hydrophobic interactions are the dominated non-covalent interactions between the active disruptors and CrmTTR. The optimum mechanism-based (for CrmTTR), and high throughput screening (for CrmTTR, little skate-TTR, seabream-TTR, and human-TTR) binary classification models are developed using three machine learning algorithms, and all the models have good classification performance. To facilitate the use of developed high throughput screening models, a tool named "TTR Profiler" is derived, which could be employed to determine whether a given substance is a potential CrmTTR, little skate-TTR, seabream-TTR, or human-TTR disruptor or not. [ABSTRACT FROM AUTHOR]

Growing concerns over public health and environmental safety have intensified the focus on minimizing harmful disinfection byproducts (DBPs) in water treatment. Traditional methods like chlorination, while effective against pathogens, often lead to the formation of DBPs, which pose significant risks. This paper explores alternative strategies to reducing DBP formation while ensuring effective disinfection. The methodology involved a bibliographic study conducted through the Scopus platform, using appropriate keywords. The initial search yielded 9576 articles from the period 2020 to 2024. The key approaches identified include advanced oxidation processes (AOPs) such as UV/H2O2 and ozone, which mineralize natural organic matter (NOM) and minimize chemical use and sludge production; membrane-based filtration systems, like reverse osmosis, effectively removing contaminants without chemical disinfectants, reducing DBP risks. Furthermore, conventional processes, such as coagulation and filtration, serve as crucial pretreatment steps to lower NOM levels before disinfection. Additionally, optimizing chlorine dosing, using non-chlorine disinfectants, and employing post-disinfection methods like adsorption and biological filtration further mitigate DBP formation. Finally, the integration of artificial intelligence in process optimization is emerging as a promising tool for enhancing treatment efficiency and safety. This research contributes to the development of safer, more sustainable water treatment solutions, addressing regulatory demands and public health objectives. [ABSTRACT FROM AUTHOR]

Trihalomethanes, the main drinking water disinfection byproducts, may be carcinogenic and are regulated to amaximum total trihalomethanes (TTHM) of 80 µg/l in the US. We aimed to determine whether total and individual trihalomethanes in drinking water across the US are associated with higher cancer mortality in 6,260 adult participants to the National Health and Nutrition Examination Surveys from 1999 to 2008 followed for mortality until 2019 (median: 14.4 years). At baseline, the geometric mean (standard error) of TTHM in drinking water was 9.61 (0.85) µg/l. During follow-up, 873 deaths occurred, including 207 from cancer. In Cox proportional hazards regression adjusted for relevant covariates, drinking water TTHM (HR: 1.45, 95% CI: 1.16–1.82), chloroform (HR: 1.35, 95% CI: 1.12–1.64), and bromodichloromethane (HR: 1.30, 95% CI: 1.05–1.59) were associated with 30% to 45% higher cancer mortality. Therefore, drinking water trihalomethanes, especially chloroform and bromodichloromethane maybe risk factors for cancer mortality. [ABSTRACT FROM AUTHOR]

The adsorption of trihalomethanes (THMs) from drinking water was investigated in the current study through comparison studies of kaolinite and ZnO@kaolinite nanocomposites. The clay structural network’s successful immobilization on the zincite hexagonal structure of ZnO nanoparticles’ lattice layers was verified by the SEM/EDX analysis. Under the optimum conditions, the maximum removal of THMs was achieved by kaolinite and ZnO@kaolinite nanocomposites after 60 min. The adsorption performance of the ZnO@kaolinite nanocomposites was greater than that of kaolinite because the former had a larger surface area than the latter. The Freundlich isotherm model best matched the adsorption experimental data, which also reveals the existence of multilayer adsorption on a diverse surface with the greatest correlation (R² ¼ 0.956 and 0.954, respectively) for both nanoadsorbents using the pseudo-first-order (PFO), pseudo-second-order (PSO), mixed 1, 2-order (MFSO), and intraparticle diffusion (IPD) models. The mechanism by which THMs in drinking water adsorb onto nanoadsorbents was examined. This revealed that both intraparticle and film diffusion were involved in the adsorption process. Kaolinite and ZnO@kaolinite nanocomposites can be used in water treatment to remove THMs due to their great recyclable and reusable properties, even after six cycles. [ABSTRACT FROM AUTHOR]

Key Takeaways: With elevated disinfection byproduct (DBP) levels in its distribution system, a water treatment plant in Maine worked with an engineering consultant to develop solutions and avoid possible regulatory violations. Four mitigation options were determined—two of them immediate and two long‐term, with the chosen strategy being premembrane coagulation. Recommendations from the success of the DBP mitigation project include being proactive, collaborating with team members and outside experts, and planning for resilience. [ABSTRACT FROM AUTHOR]

Microplastics that adsorb various toxic contaminants in water may be transported into cells and organs, possibly posing toxicological risks in the aquatic environment. Disinfection byproducts (DBPs), which are ubiquitous in chlorinated drinking water and wastewater, may have some potential to sorb onto microplastics (MPs) through hydrophobic or electrostatic interactions. However, DBP adsorption on microplastics has not yet been closely examined. This work investigated the adsorption behavior of trihalomethanes (THMs)—a regulated and ubiquitous DBP class in chlorinated water—onto virgin and weathered polyvinyl chloride (PVC) microplastics, the most widely used plastic material in drinking water distribution and sewer systems. A comparative analysis of kinetic and isotherm test results indicated that the adsorption mechanisms mainly involved hydrophobic interactions from a combination of weak and strong physisorption behavior and possibly chemisorption. The adsorption coefficients from all the models examined suggested that the adsorption of THMs, and perhaps chemically similar DBPs, onto virgin PVC microplastics can be 10–20 µg g−1. However, the weathered PVC microplastics contained more polar functional groups, which led to a decreased hydrophobicity and reduced THM adsorption capacity by approximately 10%. These findings offer novel insights into the possible adsorption characteristics of disinfection byproducts (DBPs) onto microplastics and will assist in targeting more toxic DBPs for future investigations. [ABSTRACT FROM AUTHOR]

Premise plumbing systems (PPSs), which are connected to the main drinking water distribution system via service lines, are a primary source for human exposure to chemical and microbial contaminants through inhalation, ingestion, and skin contact. To understand the occurrence and distribution of drinking water contaminants in these systems, this study utilized a full-scale PPS and monitored operational parameters and water quality changes for 26 weeks. The PPS contained natural gas- and electric-powered instantaneous and tank hot water heaters (HWHs), each supplying separate sinks and a single shower stall. Total water, gas, and electric usage was monitored daily. Over 400 water samples were collected at 11 timepoints across a 26-week period. Samples represented 4 types: Supply, Hot, Cold, and Shower water, with either stagnant (after an 8-hour period of no water usage), 10-15 second, and/or 5–10-minute flushed samples collected. Lower heterotrophic plate count (HPC) levels were observed in Shower and Hot water samples compared to those in the Supply Line, with most Hot water samples displaying decreases in adenosine triphosphate (ATP) levels post flushing. Water quality differences were also observed between Hot water samples supplied by instantaneous and tank HWHs, such as temperature, oxidation-reduction potential (ORP), conductivity, chlorine levels, and US regulated disinfection byproducts (DBPs). Spearman tests indicated very strong to perfect negative correlations between DBPs, ORP, and free chlorine in Hot and Shower water samples. Principal component analysis revealed distinct clustering of Cold and Hot water samples, supplied either by instantaneous or tank HWH samples, which were driven by differences in temperature, HPC/ATP, DBPs, conductivity, and disinfectant residual. These differences were also impacted by water stagnation as observed by the separate clustering of respective stagnant and flushed HWH samples. Collectively, HWH system and water age (i.e., stagnation) and type strongly influenced chemical and microbial water quality and furthers the understanding of the impacts PPS design and engineering parameters have on water quality.

We characterized concentrations of trihalomethanes (THMs), a measure of disinfection byproducts (DBPs), in tap water samples collected from households with utility-supplied water in two rural counties in Appalachian Virginia, and assessed associations with pH, free chlorine, and metal ions which can impact THM formation. Free chlorine concentrations in all samples (n = 27 homes) complied with EPA drinking water guidelines, though 7% (n = 2) of first draw samples and 11% (n = 3) of 5-min flushed-tap water samples exceeded the US Safe Drinking Water Act (SDWA) maximum contaminant level (MCL) for THM (80 ppb). Regression analyses showed that free chlorine and pH were positively associated with the formation of THM levels above SDWA MCLs (OR = 1.04, p = 0.97 and OR = 1.74, p = 0.79, respectively), while temperature was negatively associated (OR = 0.78, p = 0.38). Of the eight utilities serving study households, samples from water served by three different utilities exceeded the EPA MCL for THM. Overall, these findings do not indicate substantial exposures to DBPs for rural households with utility-supplied water in this region of southwest Virginia. However, given the observed variability in THM concentrations between and across utilities, and established adverse health impacts associated with chronic and acute DBP exposure, more research on DBPs in rural Central Appalachia is warranted. HIGHLIGHTS 11% (n = 3) of tap water samples exceeded the EPA MCL threshold for THMs (>80 ppb).; Mean free chlorine residual in tap water samples was ≥0.2 ppm, aligning with regulatory guidance.; More research is warranted to characterize rural exposures and assess potential drivers of DBP formation in small rural systems.;

Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health. However, current analysis approaches are not ideal, as they tend to be laborious, time-consuming, or technically difficult. Disinfection byproducts (DBPs) are a family of well-known secondary pollutants formed by the reactions of chemical disinfectants with DBP precursors during water disinfection treatment. Since DBP precursors have various origins (e.g., natural, domestic, industrial, and agricultural sources), and since the formation of DBPs from different precursors in the presence of specific disinfectants is distinctive, we argue that DBPs and DBP precursors can serve as alternative indicators to assess the contamination in water sources and identify pollution origins. After providing a retrospective of the origins of DBPs and DBP precursors, as well as the specific formation patterns of DBPs from different precursors, this article presents an overview of the impacts of various natural and anthropogenic factors on DBPs and DBP precursors in drinking water sources. In practice, the DBPs (i.e., their concentration and speciation) originally present in source water and the DBP precursors determined using DBP formation potential tests—in which water samples are dosed with a stoichiometric excess of specific disinfectants in order to maximize DBP formation under certain reaction conditions—can be considered as alternative metrics. When jointly used with other water quality parameters (e.g., dissolved organic carbon, dissolved organic nitrogen, fluorescence, and molecular weight distribution) and specific contaminants of emerging concern (e.g., certain pharmaceuticals and personal care products), DBPs and DBP precursors in drinking water sources can provide a more comprehensive picture of water pollution for better managing water resources and ensuring human health.

Disinfection during tertiary municipal wastewater treatment is a necessary step to control the spread of pathogens; unfortunately, it also gives rise to numerous disinfection byproducts (DBPs), only a few of which are regulated because of the analytical challenges associated with the vast number of potential DBPs. This study utilized polydimethylsiloxane (PDMS) passive samplers, comprehensive two-dimensional gas chromatography (GC×GC) coupled with time-of-flight mass spectrometry (TOFMS), and non-negative matrix factorization (NMF) spectral deconvolution for suspect screening of DBPs in treated wastewater. PDMS samplers were deployed upstream and downstream of the chlorination unit in a municipal wastewater treatment plant located in Abu Dhabi, and their extracts were analyzed using GC×GC-TOFMS. A workflow incorporating a multi-tiered, eight-filter screening process was developed, which successfully enabled the reliable isolation of 22 candidate DBPs from thousands of peaks. The NMF spectral deconvolution improved the match factor score of unknown mass spectra to the reference mass spectra available in the NIST library by 17% and facilitated the identification of seven additional DBPs. The close match of the first-dimension retention index data and the GC×GC elution patterns of DBPs, both predicted using the Abraham solvation model, with their respective experimental counterparts—with the measured data available in the NIST WebBook and the GC×GC elution patterns being those observed for the candidate peaks—significantly enhanced the accuracy of peak assignment. Isotopic pattern analysis revealed a close correspondence for 11 DBPs with clearly visible isotopologues in reference spectra, thereby further strengthening the confidence in the peak assignment of these DBPs. Brominated analogues were prevalent among the detected DBPs, possibly due to seawater intrusion. The fate, behavior, persistence, and toxicity of tentatively identified DBPs were assessed using EPI Suite™ and the CompTox Chemicals Dashboard. This revealed their significant toxicity to aquatic organisms, including developmental, mutagenic, and endocrine-disrupting effects in certain DBPs. Some DBPs also showed activity in various CompTox bioassays, implicating them in adverse molecular pathways. Additionally, 11 DBPs demonstrated high environmental persistence and resistance to biodegradation. This combined approach offers a powerful tool for future research and environmental monitoring, enabling accurate identification and assessment of DBPs and their potential risks.

Disinfection during tertiary municipal wastewater treatment is a necessary step to control the spread of pathogens; unfortunately, it also gives rise to numerous disinfection byproducts (DBPs), only a few of which are regulated because of the analytical challenges associated with the vast number of potential DBPs. This study utilized polydimethylsiloxane (PDMS) passive samplers, comprehensive two-dimensional gas chromatography (GC×GC) coupled with time-of-flight mass spectrometry (TOFMS), and non-negative matrix factorization (NMF) spectral deconvolution for suspect screening of DBPs in treated wastewater. PDMS samplers were deployed upstream and downstream of the chlorination unit in a municipal wastewater treatment plant located in Abu Dhabi, and their extracts were analyzed using GC×GC-TOFMS. A workflow incorporating a multi-tiered, eight-filter screening process was developed, which successfully enabled the reliable isolation of 22 candidate DBPs from thousands of peaks. The NMF spectral deconvolution improved the match factor score of unknown mass spectra to the reference mass spectra available in the NIST library by 17% and facilitated the identification of seven additional DBPs. The close match of the first-dimension retention index data and the GC×GC elution patterns of DBPs, both predicted using the Abraham solvation model, with their respective experimental counterparts—with the measured data available in the NIST WebBook and the GC×GC elution patterns being those observed for the candidate peaks—significantly enhanced the accuracy of peak assignment. Isotopic pattern analysis revealed a close correspondence for 11 DBPs with clearly visible isotopologues in reference spectra, thereby further strengthening the confidence in the peak assignment of these DBPs. Brominated analogues were prevalent among the detected DBPs, possibly due to seawater intrusion. The fate, behavior, persistence, and toxicity of tentatively identified DBPs were assessed using EPI Suite™ and the CompTox Chemicals Dashboard. This revealed their significant toxicity to aquatic organisms, including developmental, mutagenic, and endocrine-disrupting effects in certain DBPs. Some DBPs also showed activity in various CompTox bioassays, implicating them in adverse molecular pathways. Additionally, 11 DBPs demonstrated high environmental persistence and resistance to biodegradation. This combined approach offers a powerful tool for future research and environmental monitoring, enabling accurate identification and assessment of DBPs and their potential risks. [ABSTRACT FROM AUTHOR]

We characterized concentrations of trihalomethanes (THMs), a measure of disinfection byproducts (DBPs), in tap water samples collected from households with utility-supplied water in two rural counties in Appalachian Virginia, and assessed associations with pH, free chlorine, and metal ions which can impact THM formation. Free chlorine concentrations in all samples (n = 27 homes) complied with EPA drinking water guidelines, though 7% (n = 2) of first draw samples and 11% (n = 3) of 5-min flushed-tap water samples exceeded the US Safe Drinking Water Act (SDWA) maximum contaminant level (MCL) for THM (80 ppb). Regression analyses showed that free chlorine and pH were positively associated with the formation of THM levels above SDWA MCLs (OR = 1.04, p = 0.97 and OR = 1.74, p = 0.79, respectively), while temperature was negatively associated (OR = 0.78, p = 0.38). Of the eight utilities serving study households, samples from water served by three different utilities exceeded the EPA MCL for THM. Overall, these findings do not indicate substantial exposures to DBPs for rural households with utility- supplied water in this region of southwest Virginia. However, given the observed variability in THM concentrations between and across utilities, and established adverse health impacts associated with chronic and acute DBP exposure, more research on DBPs in rural Central Appalachia is warranted. [ABSTRACT FROM AUTHOR]

Bromhexine and ambroxol are among the mucolytic drugs most widely used to treat acute and chronic respiratory diseases. Entering the municipal wastewater and undergoing transformations during disinfection with active chlorine, these compounds can produce nitrogen- and bromine-containing disinfection by-products (DBPs) that are dangerous for aquatic ecosystems. In the present study, primary and deep degradation products of ambroxol and bromhexine obtained in model aquatic chlorination experiments were studied via the combination of high-performance liquid and gas chromatography with high-resolution mass spectrometry. It was shown that at the initial stages, the reactions of cyclization, hydroxylation, chlorination, electrophilic ipso-substitution of bromine atoms with chlorine, and oxidative N-dealkylation occur. Along with known metabolites, a number of novel primary DBPs were tentatively identified based on their elemental compositions and tandem mass spectra. Deep degradation of bromhexine and ambroxol gives twenty-four identified volatile and semi-volatile compounds of six classes, among which trihalomethanes account for more than 50%. The specific class of bromhexine- and ambroxol-related DBPs are bromine-containing haloanilines. Seven of them, including methoxy derivatives, were first discovered in the present study. One more novel class of DBPs associated with bromhexine and ambroxol is represented by halogenated indazoles formed through dealkylation of the primary transformation products containing pyrazoline or tetrahydropyrimidine cycle in their structure. [ABSTRACT FROM AUTHOR]

In the face of ongoing water pollution challenges, the intricate interplay between dissolved organic matter and disinfectants like chlorine gives rise to potentially harmful disinfection byproducts (DBPs) during water treatment. The exploration of DBP formation originating from amino acids (AA) is a critical focus of global research. Aromatic DBPs, in particular, have garnered considerable attention due to their markedly higher toxicity compared to their aliphatic counterparts. This work seeks to advance the understanding of DBP formation by investigating chlorination disinfection and kinetics using tyrosine (Tyr), phenylalanine (Phe), and tryptophan (Trp) as precursors. Via rigorous experiments, a total of 15 distinct DBPs with accurate molecular structures were successfully identified. The chlorination of all three AAs yielded highly toxic chlorophenylacetonitriles (CPANs), and the disinfectant dosage and pH value of the reaction system potentially influence chlorination kinetics. Notably, Phe exhibited the highest degradation rate compared to Tyr and Trp, at both the CAA:CHOCl ratio of within 1:2 and a wide pH range (6.0 to 9.0). Additionally, a neutral pH environment triggered the maximal reaction rates of the three AAs, while an acidic condition may reduce their reactivity. Overall, this study aims to augment the DBP database and foster a deeper comprehension of the DBP formation and relevant kinetics underlying the chlorination of aromatic AAs. [ABSTRACT FROM AUTHOR]

Iodine acetonitrile (IAN) is an important halogenated acetonitrile (HANs) with potential toxic effect on organism. However, no in vivo toxicological study has been reported on IAN. To quantify the toxicity of IAN, we sought to use adult Drosophila as a model for studying IAN-induced neurotoxicity. Adult Drosophila flies were exposed to 1000 mg/L, 100 mg/L, 10 mg/L, and 1 mg/L IAN or dibromoacetonitrile (DBAN, used as positive control) for 4 days to observe fly survival rate, and for 7 days to study climbing behavior. One hundred percent lethality was observed at 1000 mg/L IAN or DBAN. Kaplan‒Meier survival curves demonstrated that the overall survival of flies treated with 1 mg/L IAN was significantly shorter than that of flies treated with 1 mg/L DBAN. The climbing assay showed that the 10 mg/L IAN and 100 mg/L DBAN conditions started to reduce the climbing ability of the flies, suggesting that IAN and DBAN are neurotoxicity. In conclusion, IAN is more toxic than DBAN. It is recommended that attention be paid to toxicity, and IAN be included in the water test criteria to limit its concentration. In addition, IAN exposure was associated with changes in climbing behavior in flies, which might be associated with neurotoxicity. [ABSTRACT FROM AUTHOR]

Predictive models of disinfection byproducts (DBPs) formation in treated drinking water have been widely used to guide operational decisions. However, very few studies have addressed the issue of managing DBPs through watershed protection programs and proactive management of water supply systems through predictive modeling of DBP formation potential in source waters. Here, we propose a two‐component, simple statistical approach to predict the formation potentials of the sum of five haloacetic acids (HAA5fp) and total trihalomethanes (TTHMfp) in source water streams using environmental variables and ultraviolet absorbance at 254 nm wavelength (UV254) as a surrogate for DBP precursors. In the first component of the model, using three feature selection regression models and cross‐validation of subsets of the selected predictors, we identified three commonly monitored variables—streamflow, soil temperature, and total phosphorus for predicting UV254. In the second component, HAA5fp and TTHMfp are predicted from UV254. The approach is successfully demonstrated for two source water streams of the New York City water supply system (R2 was 0.8, and 0.7–0.8 for the two model components). Long‐term predictions of HAA5fp and TTHMfp showed distinct seasonal patterns that are linked to differences in land uses of the two watersheds. Moreover, sensitivity analysis showed that transport processes were important in one watershed whereas production processes were more important in the other. [ABSTRACT FROM AUTHOR]

2,6-Dihalogenated nitrophenols (2,6-DHNPs) are emerging halogenated nitroaromatic pollutants that have been detected in various water environments. However, there is currently limited research available regarding their potential impacts on locomotion behavior and neurotoxicity. Therefore, this study utilized zebrafish embryos to investigate the potential neurotoxic effects of 2,6-DHNPs by examining their impact on the nervous system at a concentration defined as 10% of the median lethal concentration. Our findings demonstrated that exposure to 2,6-DHNPs resulted in a significant 30 % decrease in the total swimming distance of zebrafish larvae, accompanied by notable impairments in motor neuron development and central nervous system. These effects were evidenced by a substantial 25% decrease in axonal growth, as well as disruptions in synapse formation and neuronal differentiation. Additionally, neurotransmitter analysis revealed marked decreases of 40%, 35%, and 30% in dopamine, 5-hydroxytryptamine, and acetylcholine levels respectively, highlighting disturbances in their synthesis, transport, and degradation mechanisms. These results emphasize the considerable neurotoxicity of 2,6-DHNPs at concentrations previously considered safe; thus necessitating a re-evaluation of environmental risk assessments and regulatory standards for such emerging contaminants.

Changes in climate, season, and vegetation can alter organic export from watersheds. While an accepted tradeoff to protect public health, disinfection processes during drinking water treatment can adversely react with organic compounds to form disinfection byproducts (DBPs). By extension, DBP monitoring can yield insights into hydrobiogeochemical dynamics within watersheds and their implications for water resource management. In this study, we analyzed temporal trends from a water treatment facility that sources water from Coal Creek in Crested Butte, Colorado. These trends revealed a long-term increase in haloacetic acid and trihalomethane formation over the period of 2005-2020. Disproportionate export of dissolved organic carbon and formation of DBPs that exceeded maximum contaminant levels were consistently recorded in association with late spring freshet. Synoptic sampling of the creek in 2020 and 2021 identified a biogeochemical hotspot for organic carbon export in the upper domain of the watershed that contained a prominent fulvic acid-like fluorescent signature. DBP formation potential analyses from this domain yielded similar ratios of regulated DBP classes to those formed at the drinking water facility. Spectrometric qualitative analyses of pre and post-reacted waters with hypochlorite indicated lignin-like and condensed hydrocarbon-like molecules were the major reactive chemical classes during chlorine-based disinfection. This study demonstrates how drinking water quality archives combined with synoptic sampling and targeted analyses can be used to identify and understand export control points for dissolved organic matter. This approach could be applied to identify and characterize analogous watersheds where seasonal or climate-associated organic matter export challenge water treatment disinfection and by extension inform watershed management and drinking water treatment.

Growing concerns over public health and environmental safety have intensified the focus on minimizing harmful disinfection byproducts (DBPs) in water treatment. Traditional methods like chlorination, while effective against pathogens, often lead to the formation of DBPs, which pose significant risks. This paper explores alternative strategies to reducing DBP formation while ensuring effective disinfection. The methodology involved a bibliographic study conducted through the Scopus platform, using appropriate keywords. The initial search yielded 9576 articles from the period 2020 to 2024. The key approaches identified include advanced oxidation processes (AOPs) such as UV/H2O2 and ozone, which mineralize natural organic matter (NOM) and minimize chemical use and sludge production; membrane-based filtration systems, like reverse osmosis, effectively removing contaminants without chemical disinfectants, reducing DBP risks. Furthermore, conventional processes, such as coagulation and filtration, serve as crucial pretreatment steps to lower NOM levels before disinfection. Additionally, optimizing chlorine dosing, using non-chlorine disinfectants, and employing post-disinfection methods like adsorption and biological filtration further mitigate DBP formation. Finally, the integration of artificial intelligence in process optimization is emerging as a promising tool for enhancing treatment efficiency and safety. This research contributes to the development of safer, more sustainable water treatment solutions, addressing regulatory demands and public health objectives.

Halobenzoquinones (HBQs) were recently discovered as an emerging class of drinking water disinfection byproducts with carcinogenic concern. However, the molecular mechanism underlying HBQs-induced DNA damage is not clear. In this study, we integrated in vitro genotoxicity, computational toxicology, and the quantitative toxicogenomic analysis of HBQs on DNA damage/repair pathways in human bladder epithelial cells SV-HUC-1. The results showed that HBQs could induce cytotoxicity with the descending order as 2,6-DIBQ > 2,6-DCBQ ≈ 2,6-DBBQ. Also, HBQs can increase DNA damage in SV-HUC-1 cells and thus generate genotoxicity. However, there is no significant difference in genotoxicity among the three HBQs. The results of molecular docking and molecular dynamics simulation further confirmed that HBQs had high binding fractions and stability to DNA. Toxicogenomic analysis indicated that HBQs interfered with DNA repair pathways, mainly affecting base excision repair, nucleotide excision repair and homologous recombination repair. These results have provided new insights into the underlying molecular mechanisms of HBQs-induced DNA damage, and contributed to the understanding of the relationship between exposure to DBPs and risks of developing bladder cancer.

This article, published in 1980, explores the connection between algae and the formation of trihalomethanes (THMs) in water supplies. The study conducted in northern Virginia found that THM concentrations varied seasonally and correlated with chlorophyll-a concentrations in the reservoir. Laboratory experiments confirmed that algal biomass and algal extracellular products can act as precursors for THMs. The article emphasizes the importance of understanding the role of algae in water quality and suggests that further research is needed to fully comprehend the relationship between algae and THMs. [Extracted from the article]

An ongoing hydrogen peroxide pilot project at a Connecticut water treatment facility showed promising benefits beyond disinfection precursor oxidation, such as reduced total organic carbon, lower chemical costs, and improved aesthetics. [ABSTRACT FROM AUTHOR]

Nitrosamines, including N-nitrosodimethylamine (NDMA), are disinfection by-products of concern for drinking water utilities that use chloramines as a disinfectant. In this study, batch experiments were performed to investigate the effectiveness of preoxidation with ozone, free chlorine, or both on removal of NDMA precursors in raw, lime-softened, and recarbonated water from a full-scale water treatment plant treating primarily Mississippi River water and in a tributary water sample before and after bench-scale lime softening. NDMA "precursor" concentrations were assessed indirectly by quantifying NDMA formed after addition of preformed chloramines using the uniform formation conditions (UFC) protocol. NDMA concentrations (NDMAUFC) in the raw plant water were 8 ng/L in summer and 10 ng/L in winter and increased to 13–26 ng/L in lime-softened and recarbonated waters. NDMAUFC in the raw tributary water was 33.7 ng/L. Preoxidation by ozone at doses of up to 5 mg/L effectively decreased NDMAUFC concentrations in all water samples with and without hydrogen peroxide addition (hydrogen peroxide:ozone mass ratio of 0.5:1). The effectiveness of ozone at destroying ambient NDMA precursors was independent of water temperature and ozone dose. NDMA precursor destruction, however, increased with increasing ozone dose for a recarbonated water sample spiked with ranitidine (initial NDMAUFC = 358 ng/L). Free chlorine at a dose of 5 mg/L as Cl2 for 20 min of contact time (i.e., Ct ∼70 mg-min/L) was most effective at destroying ambient NDMA precursors in recarbonated water, and similarly, free chlorine treatment following ozone (2 mg/L) was more effective at destroying NDMA precursors in the ranitidine-spiked water than ozone alone. Preoxidation with ozone, free chlorine, or both proved to be an effective strategy for limiting NDMA formation upon subsequent chloramination for surface waters impacted by agricultural activities and municipal wastewater discharges. [ABSTRACT FROM AUTHOR]

Key Takeaways: The effectiveness of powdered activated carbon (PAC) at removing cyanotoxins depends on the specific toxin(s), water pH, and PAC source. A study showed that wood–lignite PAC adsorbed more cyanotoxin than bituminous coal–based PAC, and cyanotoxin removal was more effective at a higher pH. In this study, removal costs decreased as toxin concentration increased, and saxitoxin removal was less expensive when it was present with microcystin‐LR. A decision tree that balances treatment costs with toxin removal efficiency was developed to help water utilities. [ABSTRACT FROM AUTHOR]

Effective filtration depends on a combination of complex physical and chemical mechanisms. It's important for operators to know how granular media filters work, the basics of how they are designed, and strategies for successful operation. [ABSTRACT FROM AUTHOR]

Disinfection byproducts (DBPs) are emerging pollutants in drinking water with high health risks. Precursor reduction before disinfection is an effective strategy to control the formation of DBPs. In this study, three types of anion exchange resins (AERs) and two types of nanofiltration (NF) membranes were tested for their control effects on DBP precursors, DBPs, and total organic halogen (TOX). The results showed that, for AER adsorption, the removal efficiencies of DBP precursors, DBPs, and TOX increased with the increase of resin dose, and the strong basic macroporous anion exchange resin (M500MB) had the highest removal efficiencies. For NF, the highest removal efficiencies were achieved at an operating pressure of 4 bar, and the membrane (NF90) with a smaller molecular weight cut-off, had a better control efficiency. However, AER adsorption was inefficient in removing dissolved organic carbon (DOC); NF was inefficient in removing Br− resulting in insufficient control of Br-DBPs. Accordingly, a sequential approach of AER (M500MB) adsorption followed by NF (NF90) was developed to enhance the control efficiency of DBPs. Compared with single AER adsorption and single NF, the sequential approach further increased the removal efficiencies of DOC by 19.4%–101.9%, coupled with the high Br− removal efficiency of 92%, and thus improved the reduction of cyclic DBPs and TOX by 3.5%–4.9%, and 2.4%–8.4%, respectively; the sequential approach also reduced the cytotoxicity of the water sample by 66.4%. [ABSTRACT FROM AUTHOR]

Introduction: Reaction of disinfection reagents, particularly chlorine, with natural organic material existing in raw water, results in production of a wide range of organic compounds, also known as disinfection byproducts. Despite their sever impacts on human health, only a tiny fraction of disinfection byproducts is regulated and controlled. Material and methods: In the present work, a novel solid-phase microextraction Arrow coupled with GC-MS has been developed, optimized and implemented for determination of seven non regulated disinfection byproducts; trichloroacetonitrile, dichloroacetonitrile, 1,1-dichloro-2-propanone, chloropicrin, bromochloroacetonitrile, 1,1,1-trichloro-2- propanone and dibromoacetonitrile. A central composite design was used to optimize the extraction parameters. Results and discussion: The method was sensitive enough to detect traces of the target compounds, with LOD values of 0.4-20 ng L-1. Also, quantitative analysis was possible over a wide linear range of about four orders of magnitude (50 to 100000 ng L-1 with R2 values of more than 0.997) with reasonable precision (RSD% values of less than 21.6% at 50 ng L-1. relative recoveries were between 60 and 95 %. Conclusion: The optimized technique was also successfully implemented for determination of the target compounds in ten drinking water samples and as result, most of them were observed in various concentration levels.

To enhance the quality of life and ensure sustainability in crowded cities, safe management of drinking water using cutting-edge technologies is a priority. This study developed an intelligent early warning system (EWS) for alarming and controlling risks from bacteria and disinfection byproducts in a drinking water distribution system (DWDS), named BARCS (Bacterial Risk Controlling System). BARCS adopts an artificial intelligence (AI) approach to data-driven prediction and considers total chlorine (TCl) concentration as the pivot indicator for risk identification and control. First, the machine learning-based AI model in BARCS can provide a reliable prediction of TCl concentration in a DWDS, with an average R2 of 0.64 for the validation set, while offering great flexibility for BARCS to adapt to various conditions. Second, TCl concentration was proven to be a good indicator of bacterial risk in a DWDS, as well as a cost-effective surrogate variable to assess disinfection byproduct risk. Third, the robustness analysis demonstrates that with state-of-the-art water quality monitoring technologies, online implementation of BARCS in real-world settings is feasible. Overall, BARCS represents a promising solution to the safe management of drinking water in future smart cities. HIGHLIGHTS BARCS predicts and regulates bacterial risk in pipelines.; TCl prediction module harvests an average R2 of 0.64 for the validation set.; The relationship between TCl and CFU is quantified.; Online implementation of BARCS in real-world settings is feasible.;

Graphitic carbon nitride (CN) was a promising candidate for efficient environmental remediation in the advanced oxidation processes (AOPs). However, whether CN itself had some potential environmental risks, such as affecting the production of disinfection byproducts (DBPs) was still unknown. This study investigated the formation potential of DBPs in the presence of CN. The experimental data revealed that CN had a high potential to form DBPs, and dichloroacetonitrile (DCAN) was the most produced species during the chlorination and chloramination processes. Moreover, the effects of chlorine time, chlorine dosage, pH, and CN dosage during the chlorination process were evaluated to understand the formation pattern of DBPs. The possible mechanism of DBPs formation was deduced by analyzing the results of FTIR, Raman, and XPS before and after chlorination. Finally, the DBPs formation potential and cytotoxicity of the CN leaching solution were investigated, indicating CN could leach the precursors of DBPs and that the potential toxicity of the leaching solution increased with the extension of CN immersion time. In general, this research adds an understanding of the DBP formation of CN in water treatment systems and sheds light on CN's environmental potential risks. HIGHLIGHTS g-C3N4(CN) has a high potential to form DBPs and dichloroacetonitrile (DCAN) was the dominant species.; Chorine dosage, pH, and CN dosage could significantly affect DBPs formation.; Chlorine attacked the N-containing aromatic ring and the surface amino group of CN to produce DBPs.; CN could leach the precursors of DBPs and DCAN was the major contributor to the formed DBPs cytotoxicity.;

Microplastics that adsorb various toxic contaminants in water may be transported into cells and organs, possibly posing toxicological risks in the aquatic environment. Disinfection byproducts (DBPs), which are ubiquitous in chlorinated drinking water and wastewater, may have some potential to sorb onto microplastics (MPs) through hydrophobic or electrostatic interactions. However, DBP adsorption on microplastics has not yet been closely examined. This work investigated the adsorption behavior of trihalomethanes (THMs)—a regulated and ubiquitous DBP class in chlorinated water—onto virgin and weathered polyvinyl chloride (PVC) microplastics, the most widely used plastic material in drinking water distribution and sewer systems. A comparative analysis of kinetic and isotherm test results indicated that the adsorption mechanisms mainly involved hydrophobic interactions from a combination of weak and strong physisorption behavior and possibly chemisorption. The adsorption coefficients from all the models examined suggested that the adsorption of THMs, and perhaps chemically similar DBPs, onto virgin PVC microplastics can be 10–20 µg g−1. However, the weathered PVC microplastics contained more polar functional groups, which led to a decreased hydrophobicity and reduced THM adsorption capacity by approximately 10%. These findings offer novel insights into the possible adsorption characteristics of disinfection byproducts (DBPs) onto microplastics and will assist in targeting more toxic DBPs for future investigations.

In the face of ongoing water pollution challenges, the intricate interplay between dissolved organic matter and disinfectants like chlorine gives rise to potentially harmful disinfection byproducts (DBPs) during water treatment. The exploration of DBP formation originating from amino acids (AA) is a critical focus of global research. Aromatic DBPs, in particular, have garnered considerable attention due to their markedly higher toxicity compared to their aliphatic counterparts. This work seeks to advance the understanding of DBP formation by investigating chlorination disinfection and kinetics using tyrosine (Tyr), phenylalanine (Phe), and tryptophan (Trp) as precursors. Via rigorous experiments, a total of 15 distinct DBPs with accurate molecular structures were successfully identified. The chlorination of all three AAs yielded highly toxic chlorophenylacetonitriles (CPANs), and the disinfectant dosage and pH value of the reaction system potentially influence chlorination kinetics. Notably, Phe exhibited the highest degradation rate compared to Tyr and Trp, at both the CAA:CHOCl ratio of within 1:2 and a wide pH range (6.0 to 9.0). Additionally, a neutral pH environment triggered the maximal reaction rates of the three AAs, while an acidic condition may reduce their reactivity. Overall, this study aims to augment the DBP database and foster a deeper comprehension of the DBP formation and relevant kinetics underlying the chlorination of aromatic AAs.

Reports have shown an increase in the use of disinfectants in wastewater treatment plants, prompted by the detection of residual viruses in sewage. However, the release of disinfection byproducts (DBPs) in final effluents has raised concerns about their potential adverse effects, such as endocrine disruption, on aquatic environments. Despite these concerns, few studies have examined the endocrine-disrupting effects of DBPs on fish, which may be vulnerable to DBPs. The aim of this case study was to investigate the endocrine-disrupting properties of four commonly formed DBPs: chloroiodomethane (CIM), dibromochloromethane (DBCM), bromodichloromethane (BDCM), and trichloroacetic acid (TCA) on the estrogen receptor-α in zebrafish (zERα). The results indicated that all four DBPs have high anti-estrogenic activity against zERα; with CIM, BDCM, DBCM, and TCA yielding 80.8%, 78.4%, 49.0%, and 64.1% anti-estrogenic effects on zERα, respectively. Moreover, all DBPs demonstrated negligible estrogenic effects on zERα. Our study sheds new light on the adverse effects of DBPs, particularly the endocrine-disrupting activity of CIM, which, as part of the dihalomethanes group, has received limited research attention in the past. This study shows the molecular interactions in terms of the endocrine disruption of DBP on zERα, warranting further studies to understand the overall impact of fish in affected aquatic ecosystems.

Sunlight exposure can degrade and transform discharged wastewater effluent organic matter (EfOM) in aquatic systems, potentially enhancing the feasibility of reusing wastewater for drinking purposes. However, there remains a lack of comprehensive understanding regarding the sunlight-induced changes in the molecular-level composition, characteristics, and chlorine reactivity of EfOM. Herein, we investigated the impact of sunlight on the optical properties, chemical composition, and formation of disinfection byproducts of EfOM using multiple spectroscopic analyses, high-resolution mass spectrometry, chlorination experiments, and in vitro bioassays. Upon natural sunlight exposure, we observed significant decreases in ultraviolet–visible absorbance and fluorescence intensity of EfOM, indicating the destruction of chromophores and fluorophores. Photolysis generally yields products with lower molecular weight and aromaticity, and with higher saturation and oxidation levels. Moreover, a shift within the EfOM from condensed aromatic-like compounds to tannin-like components was observed. Furthermore, sunlight exposure reduced the reactivity of EfOM toward the formation of trihalomethanes and haloacetonitriles during chlorination, while there was a slight increase in the specific formation potential of haloketones. Importantly, the disinfection byproducts resulting from chlorination of the irradiated EfOM exhibited reduced microtoxicity. Overall, this study provides new insights into alterations in EfOM under sunlight exposure and aids in predicting the health risks of effluent discharge in water environments.

The U.S. Environmental Protection Agency (EPA) is considering a regulatory revision of the Disinfectant and Disinfection Byproduct Rule (DBPR) with a goal of limiting nationwide exposure to DBPs of emerging health concern. The occurrence of four brominated haloacetic acids (HAAs), which are generally more toxic in in vitro assays than the five currently regulated HAAs and are candidates for future regulation, were surveyed in 4924 public water systems under EPA's fourth unregulated contaminant monitoring rule (UCMR4). Using UCMR4 data, this study evaluated the nationwide occurrence of nine HAA species and the potential for two regulatory scenarios (the mass sum of all nine HAA species, HAA9, or just the six brominated HAA species, HAA6Br) to control nationwide exposure to the most toxic HAAs. Neither HAA9 nor HAA6Br approaches were effective for identifying water systems that exhibit high HAA exposure, assessed as additive cytotoxicity, because they are more specific to the HAA species that form at high concentrations rather than the species that are most toxic. However, the effectiveness of HAA6Br is highly sensitive to the relative toxicity of one HAA compound, monobromoacetic acid, which has the highest in vitro toxicity among HAAs but also the lowest occurrence and about which little is known regarding in vivo health risks. In contrast to HAA9, systems with high HAA‐associated additive toxicity tend to share similar treatment and disinfectant characteristics as systems with high HAA6Br concentrations. Systems with high source water bromide and total organic carbon were far more likely to use chloramines as a disinfectant residual compared to other systems, but were no more likely to adopt organic precursor removal technologies (biofiltration, granular activated carbon, and ion exchange) than other systems, on average. [ABSTRACT FROM AUTHOR]

With the increased use of microplastics and antibiotics in modern society, a large number of microplastics and antibiotics are being found in natural and water treatment systems. In this paper, the effect of polypropylene (PP), polyethylene (PE), and polystyrene (PS) microplastics (MPs) on the chlorination of ciprofloxacin (CIP) and subsequent production of disinfection byproducts (DBPs) was investigated using sodium hypochlorite (NaClO) as the disinfectant and trichloromethane (CHCl3) and dichloroacetonitrile (DCAN) as typical carbon- and nitrogen-containing disinfection byproducts. Disinfection byproducts (DBPs) were investigated. The results showed that the mass concentrations of CHCl3 and DCAN generated after CIP chlorination were higher, reaching 160.1 μg/L and 2.5 μg/L, respectively, than those generated after the chlorination of microplastics (0.49~41 μg/L). Considering the effect of microplastics on the chlorination of ciprofloxacin to generate disinfection byproducts, it was found that the increase in the production of CHCl3 and DCAN was not significant and that production even tended to decrease. There was a slight contribution to the generation of CHCl3 with increasing microplastic concentration. There was almost no effect on DCAN, and the generation of DCAN was even inhibited. Increases in pH, NaClO dose, and chlorination time promoted the generation of CHCl3, but DCAN showed a decreasing trend due to its instability and easy decomposition. This study provides a theoretical basis for understanding the generation of disinfection byproducts in water sources contaminated by microplastics and antibiotics. [ABSTRACT FROM AUTHOR]

Irbesartan belongs to the Sartan family, whose members are used in the treatment of arterial hypertension and kidney disease among patients with hypertension and type 2 diabetes mellitus as part of a treatment based on antihypertensive drugs. This drug has reached surface waters, accumulating to the extent of being considered an emerging pollutant, along with other substances from the same class. Wastewater treatment plants, which constitute the main environmental source of this compound, fail to completely reduce its presence in wastewater and generate additional toxic byproducts through the chlorine-based disinfection process. This study provides a comprehensive investigation into the chlorination mechanisms of irbesartan, revealing the identity of twelve new byproducts, which were characterized using NMR and mass spectrometry (MS-TOF). The other six byproducts were published in a previous study, allowing for the confirmation of some aspects of the supposed mechanisms of degradation, along with the identification of those that had only been hypothesized. An ecotoxicological assessment of a mixture and isolated byproducts was performed using Raphidocelis subcapitata for algal growth inhibition, Daphnia magna for immobility, and Aliivibrio fischeri for luminescence inhibition. The results revealed the variable toxicity of irbesartan and its byproducts. Different organisms exhibited varying sensitivities to the byproducts, with Aliivibrio fischeri being the most sensitive. The coexistence of multiple byproducts in the environment, their high toxicity, and their potential interactions highlight the significant environmental risks associated with chlorination and its derivates. Our study highlights the ongoing debate surrounding the generation of disinfection byproducts. [ABSTRACT FROM AUTHOR]

Increasing water scarcity caused by population growth, climate change, pollution from natural and anthropogenic sources, etc. is likely to impact the occurrence of water-associated infectious diseases. Nowadays, access to clean and safe water is a growing concern worldwide. Therefore, disinfection of drinking water is a vital step in public treatment systems as it ensures the removal of various contaminants, including pathogenic microorganisms (protozoa, viruses, bacteria, and intestinal parasites) that give rise to waterborne diseases. Nevertheless, undesirable disinfection byproducts (DBPs) are formed during disinfection as a result of reactions between chemical disinfectants and natural organic matter (NOM), and/or anthropogenic contaminants, and/or bromide/iodide that are present in the raw water. The chemical complexity and heterogeneity of matters in the raw water makes the characterization and the mechanism of DBPs formation quite difficult and ambiguous regardless of the previous hundreds of studies on DBPs generation. As chlorination is still the most economic and most often used disinfection method, and beside chlorination, the application of chlorine dioxide is becoming more widespread, this paper investigates the possible DBPs generated using chlorine and chlorine dioxide with highlighting their adverse health effects. It overviews the reactions of those disinfectants with inorganic and organic compounds. It is important to note that in order to better understand the performance of disinfectants in water treatment, further investigations on the mechanisms of them with inorganic and organic compounds found in water are critically needed. [ABSTRACT FROM AUTHOR]

Chloroform accumulation in the body and the increase in its steady-state concentrations in blood of exposed people have been established to be associated with polymorphisms of enzyme genes in a genotype involved in metabolism of water disinfection byproducts (A415G of EPHX1 gene, C1091T of CYP2E1 gene, zero mutations of GSTT1 and GSTM1 genes) (р < 0.000001). These polymorphisms in a genotype correlate with higher chloroform levels in blood of people consuming chlorinated drinking water: by 43.8 % and higher for GSTM1 gene polymorphism; by 68.2 % and higher for GSTT1; by 80.4 % and higher for EPHX1 (р < 0.01). EPHX1 genetic polymorphism makes chloroform accumulation much more probable (levels in blood ≥ Р75), which is the most pronounced when combined with GSTТ1 genetic polymorphism. The study results allow us to consider hetero- and homozygous polymorphic genotypes AG/GG for the EPHX1 gene, CT/TT for the CYP2E1 gene, and the null allele in the GSTT1 and GSTM1 genes as genetic predisposition factors for chloroform accumulation in the body. This increases the probability of health outcomes associated with chronic exposure to this disinfection byproduct. The A415G polymorphism of the EPHX1 gene and null alleles of GSTT1 gene, their combinations including the combination with the null allele of the GSTM1 gene and/or the C1091T polymorphism of the CYP2E1 gene can be used as the most informative biomarkers of sensitivity when assessing risks associated with exposure to trihalomethanes (chloroform) at levels not exceeding MPC in water.

Background: Trihalomethanes (THMs), a class of DBPs (disinfection byproducts) that includes chloroform, bromodichloromethane (BDCM), chlorodibromomethane (CDBM), and bromoform. To the best of authors’ knowledge, no study has addressed the relationship between the concentration of THMs and lifetime cancer risks (LCR) in drinking water supply system in Addis Ababa, Ethiopia. Therefore, this study aimed to determine the lifetime cancer risks of exposure to THMs in Addis Ababa, Ethiopia. Method: A total of 120 duplicate water samples were collected from 21 sampling points in Addis Ababa, Ethiopia. The THMs were separated by a DB-5 capillary column and detected by an electron capture detector (ECD). Cancer and non-cancer risk assessments were performed. Results: The average total THMs (TTHMs)concentration in Addis Ababa, Ethiopia, was 76.3 μg/L. Chloroform was the most dominant THM species identified. The total cancer risk for males was higher than that for females. The average LCR for TTHMs via ingestion in drinking water in this study was unacceptably high risk93.4×10−2. An average LCR through dermal routes was also of unacceptably high risk4.3×10−2. The LCR by chloroform contributes the highest (72%) of the total risk, followed by BDCM (14%), DBCM (10%) and bromoform (4%). Conclusions: The cancer risk of drinking water due to THMs in Addis Ababa was higher than the level recommended by the USEPA. The total LCR from the targeted THMs was higher via the three exposure routes. Males were at higher THM cancer risk than females. The hazard index (HI) indicated that the dermal route caused higher HI values than the ingestion route. It is essential to apply alternatives to chlorine, i.e., chlorine dioxide (ClO2), ozone and ultraviolet radiation, in Addis Ababa, Ethiopia. The monitoring and regulation of the THMs is required on a regular basis to analyse the trends and guide the water treatment and distribution system. Availability of data and materials: The datasets generated for this analysis are available from the corresponding author upon reasonable request.

Introduction: The reaction of disinfection reagents, particularly chlorine, with natural organic material existing in raw water, results in the production of a wide range of organic compounds, also known as disinfection byproducts. Despite their severe impacts on human health, only a tiny fraction of disinfection byproducts is regulated and controlled. Material and methods: In the present work, a novel solid-phase microextraction arrow coupled with GC-MS was developed, optimized and implemented for the determination of seven non-regulated disinfection byproducts; trichloroacetonitrile, dichloroacetonitrile, 1,1-dichloro-2-propanone, chloropicrin, bromochloroacetonitrile, 1,1,1-trichloro-2-propanone and dibromoacetonitrile. A central composite design was used to optimize the extraction parameters. Results and discussion: The method was sensitive enough to detect traces of the target compounds, with LOD values of 0.4-20 ng L-1. Also, quantitative analysis was possible over a wide linear range of about four orders of magnitude (50 to 100000 ng L-1 with R2 values of more than 0.997) with reasonable precision (RSD% values of less than 21.6% at 50 ng L-1). Relative recoveries were between 60 and 95 %. Conclusion: The optimized technique was also successfully implemented for the determination of the target compounds in ten drinking water samples and as a result, most of them were observed in various concentration levels. [ABSTRACT FROM AUTHOR]

Chlorination, ozonation and non-thermal plasma water purification technologies were compared in terms of their effectiveness, efficiency, capital and operating costs, energy yield and chemical demand. Retrofitting plasma technology to chlorination plants offered the lowest capital cost (ZAR 14,000 or USD 253,376 based on the current South African Reserve Bank rate of ZAR/USD of 18.0983) and the most effective contaminant removal (of the three possible combinations). How- ever, this combination yielded the highest operating costs (ZAR 586,000 per annum or USD 10.6 million) and the lowest energy efficiency. It was concluded that retrofitting chlorination plants with plasma technology is feasible. However, plasma generators should be redesigned to consume less energy or to operate using renewable energy. Furthermore, research should be performed on contaminants of emerging concern to establish a deadline after which their concentration must not exceed a specified limit. This will accelerate the implementation of plasma technology and secure the health of our posterity. [ABSTRACT FROM AUTHOR]

Ensuring drinking water quality is a key factor for public health and it is especially important given the increase in industrialization. Its quality is ensured by a water treatment process that includes a disinfection stage, mainly involving chlorination. However, by applying this disinfection method, unwanted disinfection byproducts (DBPs) are formed. These compounds have, in general, a negative impact on human health. Following this, the development of stricter regulations for drinking water quality standards has been conducted worldwide. Several techniques for the removal of DBPs have already been developed to prevent DBP formation or to reduce DBPs formed during disinfection. Nevertheless, controlling the water distribution systems after drinking water treatment is still important, since DBPs can reoccur along the distribution network. To achieve this, further research should be developed to efficiently monitor and allow the performance of the necessary actions to detect and control these contaminants throughout the water distribution system. Additionally, the most suitable places for sensing along the distribution system must be further assessed. [ABSTRACT FROM AUTHOR]

Brominated disinfection byproducts (DBPs) are a concern to drinking water utilities due to their toxicity and increasing prevalence in water systems. Haloacetic acids (HAAs) are a class of DBPs that are partially regulated by the United States Environmental Protection Agency (USEPA), but regulations are likely to increase as evidenced by the brominated HAAs listed on the USEPA Fourth Unregulated Contaminant Monitoring Rule and Fifth Contaminant Candidate List. Utilities often use a pre-oxidant to assist in their treatment training, but this can lead to increased HAA formation during treatment. In this study, tap water was spiked with bromine (Br2) at varying concentrations to simulate bromine-to-chlorine ratios found in the natural environment and the DBPs that may be formed from those waters. The water was fed through a bench-scale biological filter (biofilter) with a small layer of fresh granular activated carbon (GAC) media followed by acclimated anthracite media. The HAA species studied were found to be removable by an average of 89.5% through combined GAC filtration and biofiltration. Biodegradation occurred predominantly in the first five minutes for the acclimated anthracite, with minimal additional removal observed at longer empty bed contact times (15 and 30 min EBCT). This study provides recommendations on biofilter parameters for utilities to reduce the formation of both regulated and unregulated HAAs during the drinking water treatment process. [ABSTRACT FROM AUTHOR]