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This study reports the trihalomethanes generated during disinfection within the water distribution network of Delhi, India. For 12 months study period tap water samples were collected (n = 216) from the command areas of nine water treatment plants to provide a comprehensive picture of spatial and seasonal variation of trihalomethanes in the city. The mean concentrations of chloroform, bromodichloromethane, dibromochloromethane, bromoform were 34.62 ± 13.09 μg/l, 25.39 ± 11.75 μg/l, 15.83 ± 9.66 μg/l, 1.74 ± 1.51 μg/l respectively, the total trihalomethanes concentration ranged between 11.41–175.54 μg/l. Chloroform was prevalent accounting 45% in total trihalomethanes followed by bromodichloromethane, dibromochloromethane, bromoform accounting 33%, 20%, and 2% respectively. Trihalomethanes concentrations were found to be increasing during summer season and got decreased in the winter and post-monsoon season. Total trihalomethanes levels were found to be highest at Chandrawal water treatment plant command area (85.35–148.38 μg/l) and lowest at Okhla water treatment plant command area (11.41–63.38 μg/l). In many samples trihalomethanes concentrations were discovered to be higher than the allowable limit specified by Indian Standards. A strong relationship between trihalomethanes formation with total organic carbon (r = 0.934) and residual chlorine (r = 0.801) accentuate its capability for monitoring disinfection by-products in the distribution network. Results showed that considerable levels of trihalomethanes are generated in the study area, therefore the competent authorities must take the appropriate steps to regularly monitor the trihalomethanes in drinking water. The findings of this study may help to provide operators with invaluable information on drinking water quality and open up several chances to enhance water quality management. [ABSTRACT FROM AUTHOR]

Biological mechanisms of exposure to Trihalomethanes (THMs) in swimming pools remain unclear. Investigation of short-term changes in metabolomic profiles due to exposure to THMs during swimming can help to understand the health effects-related mechanisms. With this in view, we aimed to assess exposure of swimmers to THMs in chlorine and ozone-chlorine swimming pools using the metabolomics approach from September 2020 to January 2021 in Tehran. Two parallel panels of 29 healthy adult subjects swam over 60 min in either of swimming pools. Blood samples were collected before and 2 h after swimming to assess metabolomic profile using Hydrogen-Nuclear Magnetic Resonance Spectroscopy (H-NMR). Differential metabolites between the two groups were identified by multivariate analysis methods such as Orthogonal Partial Least-Squares Discriminant Analysis (OPLS-DA) and Random Forest (RF). The levels of THMs in exhaled air as a biomarker of exposure and the metabolic profile as a biomarker of the effect changed significantly between two participants of swimming pools. Based on the significant metabolites, the biochemical pathways were identified by the method of Metabolite Setts Enrichment Analysis (MSEA) and by using the Metaboanalyst platform. The pathways of tryptophan metabolism, galactose metabolism and fructose and mannose metabolism were the most important biochemically significant pathways in individuals after exposure to THMs. Finally, findings from metabolic changes in our study indicate that exposure to THMs in swimming pools can activate the mechanisms of central nervous system disorders, increased uric acid, increased risk of bladder cancer and oxidative stress. [ABSTRACT FROM AUTHOR]

In this study, the sodium perborate (SP)-activated peroxymonosulfate (PMS) process was used to enhance the coagulation efficiency of cyanobacteria with polymeric aluminum chloride (PAC), aiming to efficiently mitigate the impact of algal blooms on the safety of drinking water production. The optimal concentrations of SP, PMS, and PAC were determined by evaluating the removal rate of OD680 and zeta potential of the algae. Experimental results demonstrated that the proposed ternary PMS/SP/PAC process achieved a remarkable OD680 removal efficiency of 95.2%, significantly surpassing those obtained from individual treatments with PMS (19.5%), SP (5.2%), and PAC (42.1%), as well as combined treatments with PMS/PAC (55.7%) and PMS/SP (28%). The synergistic effect of PMS/SP/PAC led to the enhanced aggregation of cyanobacteria cells due to a substantial reduction in their zeta potential. Flow cytometry was performed to investigate cell integrity before and after treatment with PMS/SP/PAC. Disinfection by-products (DBPs) (sodium hypochlorite disinfection) of the algae-laden water subsequent to PMS/SP/PAC treatment declined by 57.1%. Moreover, microcystin-LR was completely degraded by PMS/SP/PAC. Electron paramagnetic resonance (EPR) analysis evidenced the continuous production of S O 4 • − , •OH, 1O2, and O 2 • − , contributing to both cell destruction and organic matter degradation. This study highlighted the significant potential offered by the PMS/SP/PAC process for treating algae-laden water. [ABSTRACT FROM AUTHOR]

Trichloramine is a disinfection by-product in chlorinated swimming pools. It can evaporate into the air and irritate eyes and airways among swimmers and pool workers. This study aimed to evaluate airborne concentrations of trichloramine in different types of indoor swimming pools. Altogether, 72 swimming pools across Sweden were included; 36 exercise pools, 16 instruction pools, seven adventure pools, and 13 rehabilitation pools. In total, 167 sampling sessions were performed with the majority (N = 91) conducted in public exercise pools. Repeated sampling sessions on different days were performed within all pool categories. Airborne trichloramine was measured stationary by the poolside using active sampling on quartz filters. In total, 434 air samples were collected. The geometric mean (GM) concentration of trichloramine for the exercise pools was 0.12 mg/m3 (range GMpool: 0.02–0.29 mg/m3) and for about 30% the GMpool exceeded the Swedish public health guideline value (0.2 mg/m3). The geometric mean for instruction pools was 0.18 mg/m3 and for adventure pools 0.20 mg/m3. Trichloramine concentrations were statistically significantly lower in rehabilitation pools (GM: 0.03 mg/m3) compared with the other pool categories. A statistically significant effect of time of the day for sampling was found for the exercise and instruction pools, with higher trichloramine levels during evenings compared with mornings and afternoons. For the rehabilitation pools, trichloramine was significantly higher during the cold season compared with the warm season. Variability in trichloramine concentrations was attributed to between-pool as well as within-pool variances. The within-pool variability encourages a repeated sampling strategy to capture the variation between different days. These findings have implications for exposure assessment in epidemiological studies as well as for indoor air quality monitoring. Trichloramine can cause acute irritative effects at elevated levels, and since trichloramine concentrations may differ depending on the time of the day it is recommended that full-day stationary measurements are supplemented with short-term samplings to capture these variations. [ABSTRACT FROM AUTHOR]

In this study, the effectiveness of the Fenton process in removing natural organic matter (NOM) from groundwater was investigated. The subject of this study is groundwater characterised by increased content of NOM and iron (II) compounds. In laboratory-scale studies, the influence of the ratio of concentrations of Fe(II) ions, which are naturally occurring in groundwater, to hydrogen peroxide (H2O2) as well as oxidation time and pH on the removal efficiency of organic matter was determined. Indicators such as total organic carbon (TOC), dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254), UV absorbance at 272 nm (UV272), and specific UV absorbance (SUVA254) were used to quantitatively and qualitatively assess the organic substances present in the raw water and after oxidation with Fenton's reagent. Analysis of the results obtained showed that the highest removal efficiency of organic substances in the deep oxidation process using the Fenton reaction was obtained for a concentration ratio of Fe(II) to H2O2 = 1:5. Acidification of the water samples to a pH of about 4 and extending the oxidation time to 30 min significantly increased the removal efficiency of organic substances including mainly dissolved organic substances containing aromatic rings. The organic substances containing aromatic rings, determined at a wavelength of 254 nm, were degraded to other organic intermediates. [ABSTRACT FROM AUTHOR]

In this study, samples from the Yangtze River, Han River, and Liangzi Lake in Wuhan City were utilized to characterize the formation of disinfection by-products (DBPs) from chlorine-based disinfection residues in drinking water sources. The results indicated that the main DBPs in drinking water sources were trichloromethane (TCM) and trichloroacetic acid (TCAA). The generation of DBPs was significantly positively correlated with oxidative substances, aromatic compounds, pH, and ammonia nitrogen (NH3-N) content in the water. The concentration of TCAA increased from 0 to 2.45 ± 0.31 mg/L when the reaction time increased to 72 h. As the NaClO concentration increased from 5 mg/L to 15 mg/L, the concentrations of TCAA, TBM, and DCAN increased from 2.03 ± 0.04 mg/L, 0 mg/L, and 0 mg/L to 2.49 ± 0.34 mg/L, 0.21 ± 0.07 mg/L, and 0.10 ± 0.04 mg/L before decreasing to 1.75 ± 0.19 mg/L, 0.17 ± 0.07 mg/L, and 0.04 ± 0.05 mg/L, respectively. The orthogonal experimental results showed that Br−, NH3-N, and pH all had significant influences on the TCM generation, whereas temperature affected the formation of TCAA in the Han River. This work reveals the factors influencing the generation of DBPs from chlorine-based disinfection residues, offering a prevention and control method for DBPs in drinking water sources from a theoretical perspective. [ABSTRACT FROM AUTHOR]

Abstract Disinfection is a critical process to ensure the safety of drinking water. To curb the spread of various bacteria and viruses, disinfectants are extensively employed in communities, hospitals, sewage treatment plants, and other settings. However, disinfectants can produce disinfection by-products (DBPs) that threaten human health. Despite their importance, research and systematic analyses of these risks remain limited. This study monitored DBPs in drinking water across 13 districts and counties in Hangzhou, conducting a risk assessment based on the health risk assessment model recommended by the United States Environmental Protection Agency. Concentrations of 12 DBPs ranged from 0.01 µg/L to 120 µg/L, with levels in 2020–2022 generally exceeding those in 2018–2019. Notably, median concentrations of trichloromethane peaked at 18.00 µg/L in 2021. Most DBPs are detected at higher concentrations in the central and northern parts. However, the spatial distribution of DBPs in drinking water was determined to be random. The health risks associated with most DBPs were higher in 2021 compared to other years. Cancer risks of DBPs ranged between 10− 6 and 10− 4 and noncarcinogenic risks were below 1. This study demonstrates that increased disinfectant use during water treatment may elevates DBPs concentrations.

• UVA 365 /ClO 2 /NaClO process showed excellent degradation efficiency of CBZ. • The UVA 365 /ClO 2 /NaClO process can effectively control the consumption of oxidants. • The main active species were HO • and Cl • at high ratios of ClO 2. • The UVA 365 /ClO 2 /NaClO process can reduce the formation of chlorate and chlorite. A mixed oxidant of chlorine dioxide (ClO 2) and NaClO was often used in water treatment. A novel UVA-LED (365 nm)-activated mixed ClO 2 /NaClO process was proposed for the degradation of micropollutants in this study. Carbamazepine (CBZ) was selected as the target pollutant. Compared with the UVA 365 /ClO 2 process, the UVA 365 /ClO 2 /NaClO process can improve the degradation of CBZ, with the rate constant increasing from 2.11×10−4 sec−1 to 2.74×10−4 sec−1. In addition, the consumption of oxidants in the UVA 365 /ClO 2 /NaClO process (73.67%) can also be lower than that of UVA 365 /NaClO (86.42%). When the NaClO ratio increased, both the degradation efficiency of CBZ and the consumption of oxidants can increase in the UVA 365 /ClO 2 /NaClO process. The solution pH can affect the contribution of NaClO in the total oxidant ratio. When the pH range of 6.0-8.0, the combination process can generate more active species to promote the degradation of CBZ. The change of active species with oxidant molar ratio was investigated in the UVA 365 /ClO 2 /NaClO process. When ClO 2 acted as the main oxidant, HO• and Cl• were the main active species, while when NaClO was the main oxidant, ClO• played a role in the system. Both chloride ion (Cl–), bicarbonate ion (HCO 3 –), and nitrate ion (NO 3 –) can promote the reaction system. As the concentration of NaClO in the reaction solution increased, the generation of chlorates will decrease. The UVA 365 /ClO 2 /NaClO process can effectively control the formation of volatile disinfection by-products (DBPs), and with the increase of ClO 2 dosage, the formation of DBPs can also decrease. [Display omitted] [ABSTRACT FROM AUTHOR]

• Ozonation enhanced the formation potential of regulated DBPs from Phe chlorination. • CH with highest yield of 21.31+1.05 ug/mgPhe was enhanced to 3 times after ozonation. • The DBPs formation rates in the first 6 h were much higher than subsequent time. • Br− promoted brominated DBPs generation and elevated the total cytotoxicity. • Ozonation enhanced the BIF of THMs, while reduced that of DHAAs. As a strong oxidizing agent, ozone is used in some water treatment facilities for disinfection, taste and odor control, and removal of organic micropollutants. Phenylalanine (Phe) was used as the target amino acid to comprehensively investigate variability of disinfection byproducts (DBPs) formation during chlorine disinfection and residual chlorine conditions subsequent to ozonation. The results showed that subsequent to ozonation, the typical regulated and unregulated DBPs formation potential (DBPsFP), including trichloromethane (TCM), dichloroacetonitrile (DCAN), chloral hydrate (CH), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), and trichloroacetamide (TCAcAm) increased substantially, by 2.4, 3.3, 5.6, 1.2, 2.5, and 6.0 times, respectively, compared with only chlorination. Ozonation also significantly increased the DBPs yield under a 2 day simulated residual chlorine condition that mimicked the water distribution system. DBPs formations followed pseudo first order kinetics. The formation rates of DBPs in the first 6 hr were higher for TCM (0.214 hr−1), DCAN (0.244 hr−1), CH (0.105 hr−1), TCAcAm (0.234 hr−1), DCAA (0.375 hr−1) and TCAA (0.190 hr−1) than thereafter. The peak DBPsFP of TCM, DCAN, CH, TCAcAm, DCAA, and TCAA were obtained when that ozonation time was set at 5–15 min. Ozonation times > 30 min increased the mineralization of Phe and decreased the formation of DBPs upon chlorination. Increasing bromine ion (Br−) concentration increased production of bromine- DBPs and decreased chlorine-DBPs formation by 59.3%–92.2%. Higher ozone dosages and slight alkaline favored to reduce DBP formation and cytotoxicity. The ozonation conditions should be optimized for all application purposes including DBPs reduction. [Display omitted] [ABSTRACT FROM AUTHOR]

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Background: The use of chlorine to treat drinking water produces disinfection by‐products (DBPs), which have been associated with congenital heart defects (CHDs) in some studies. Methods: Using National Birth Defects Prevention Study data, we linked geocoded residential addresses to public water supply measurement data for DBPs. Self‐reported water consumption and filtration methods were used to estimate maternal ingestion of DBPs. We estimated adjusted odds ratios and 95% confidence intervals using logistic regression controlling for maternal age, education, body mass index (BMI), race/ethnicity, and study site to examine associations between CHDs and both household DBP level and estimated ingestion of DBPs. Results: Household DBP exposure was assessed for 2717 participants (1495 cases and 1222 controls). We observed a broad range of positive, null, and negative estimates across eight specific CHDs and two summary exposures (trihalomethanes and haloacetic acids) plus nine individual DBP species. Examining ingestion exposure among 2488 participants (1347 cases, 1141 controls) produced similarly inconsistent results. Conclusions: Assessing both household DBP level and estimated ingestion of DBPs, we did not find strong evidence of an association between CHDs and DBPs. Despite a large study population, DBP measurements were available for less than half of participant addresses, limiting study power. [ABSTRACT FROM AUTHOR]

During the COVID-19 pandemic, most sewage treatment plants increased disinfectant dosages to inactivate pathogenic viruses and microorganisms more effectively. However, this approach also led to the production of more disinfection by-products (DBPs). To ensure both disinfection efficiency and a reduction in DBP formation, new disinfection protocols are required. In this study, the disinfection efficiency, DBP amounts, and toxicity changes resulting from ozone (O3), ultraviolet (UV), chlorine (Cl2), and their combined processes were examined. The results demonstrated that the O3/UV/Cl2 combination achieved the highest disinfection efficiency. Chlorination produced the most DBPs, whereas UV treatment reduced the formation of trihalomethane (THM), halogenated ketones (HKs), haloacetic acids (HAA), dichloroacetonitrile (DCAN) and N-nitrosodimethylamine (NDMA) by 45.9%, 52.6%, 82.0%, 67.95%, and 47%, respectively. O3 also significantly reduced their production by 99.1%, 91.1%, 99.5%, 100%, and 35%. Intracellular organic matter (IOM) was identified as the primary DBP precursors, producing 2.94 times more DBPs than extracellular organic matter (EOM). The increased DBP formation during chlorination was attributed to IOM leakage and cell membrane damage, which was verified using scanning electron microscopy (SEM). The toxicities of DBPs were evaluated for six disinfection methods, revealing inconsistent results. The overall toxicities were assessed using zebrafish embryo experiments. Both evaluations indicated that chlorination alone was the least favorable method. In addition, the toxicities followed a sequence: Cl2 ≈ O3/Cl2 > O3 > O3/UV/Cl2 > UV > UV/Cl2. These findings can serve as a reference for sewage treatment plants in selecting appropriate disinfection methods to manage the COVID-19 epidemic from comprehensive perspective. [ABSTRACT FROM AUTHOR]

Background: Previous studies have demonstrated that there is a correlation between trihalomethanes and disease progression, such as allergic diseases. As we know, only few studies focused on the relationship between trihalomethanes and metabolic diseases, such as diabetes mellitus. Objective: The aim of this study was to further explore the associations between blood trihalomethane concentrations and diabetes mellitus in older adults in the US. Methods: Data were collected from the National Health and Nutrition Examination Study (NHANES) database in the survey cycle during 2013 to 2018, including 2,511 older adults in the US whose blood trihalomethane concentrations were measured, involving chloroform (TCM) and brominated trihalomethanes (Br-THMs). Br-THMs include bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM). Meanwhile, the concentration of total trihalomethanes (TTHMs) was also measured later. A multivariate logistic regression and restricted cubic spline were used to examine the relationship between blood THMs and diabetes mellitus. Meanwhile, we performed a subgroup analysis, which aims to explore the stability of this relationship in different subgroups. In order to further consider the impact of various disinfection by-products on diabetes, we also used weighted quantile sum (WQS). To explore the correlation in trihalomethanes, we plot a correlation heatmap. Results: Adjusting for potential confounders, we found that there was a significant negative association between chloroform and diabetes mellitus [Model 1 (adjusted for covariates including age, sex, and race, OR = 0.71; 95% CI: 0.50-1.02; p = 0.068; p for trend = 0.094); Model 2 (adjusted for all covariates, OR = 0.68; 95% CI: 0.48-0.96; p = 0.029; p for trend = 0.061)]. In the bromodichloromethane, we reached a conclusion that is similar to TCM [Model 1 (adjusted for covariates including age, sex, and race, OR = 0.54; 95% CI: 0.35-0.82; p = 0.005; p for trend = 0.002); Model 2 (adjusted for all covariates, OR = 0.54; 95% CI: 0.35-0.82; p = 0.003; p for trend = 0.002)]. Meanwhile, the restricted cubic spline curve also further confirms this result (p overall = 0.0027; p overall< 0.001). Based on the analysis in the subgroups, we found that the value p for interaction in the majority of subgroups is higher than 0.1. Trihalomethanes and diabetes were inversely associated, and in the WQS, chloroform and bromodichloromethane were found to be the major contributors to this relationship. In the correlation analysis, we found that most trihalomethanes have a weak correlation, except for TBM and TCM with a strong correlation. Conclusion: Our results in this study showed that blood chloroform, bromodichloromethane concentrations, and diabetes mellitus in older adults in the US are negatively correlated, suggesting that chloroform and bromodichloromethane can be protective factors for diabetes. [ABSTRACT FROM AUTHOR]

The performance capability of granular activated carbon (GAC) adsorption in terms of disinfection by-product (DBPs) removal was investigated with synthetic water containing 1) trihalomethanes (THMs), 2) haloacetronitriles (HANs), and 3) Mix-THMs & HANs. The initial 20 min of adsorption resulted in the maximum adsorption rate, with the total THMs, total HANs, and total Mix–THMs & HANs being 4.972, 2.071, and 6.460 µg/gGAC-min, respectively. GAC dosage affects the adsorption selectivity of THMs and HANs. Under a low GAC dosage, the selectivity of GAC adsorbs more bromo-THMs than chloro-THMs. The adsorption selectivity of THMs on GAC following bromoform > dibromochloromethane > bromodichloromethane > chloroform was investigated. As the GAC concentration increased, the selectivity of THM adsorption by GAC became comparable. Chloro-HAN, in contrast to THMs, has a higher adsorption selectivity than bromo-HAN. Trichloroacetonitrile was removed by GAC more rapidly than the other HAN species when the GAC dose was increased. The toxin of bromoform was primarily eliminated through GAC adsorption, caused by a greater removal rate than that of the other THMs. As an implemented measure, GAC is introduced to reduce THMs and HANs and the toxic contents associated with THMs and HANs. [ABSTRACT FROM AUTHOR]

• UV/chlorine needed half the time of in-situ chlorination to reach 90% CBZ removal. • LP UV/chlorine was the most energy efficient among the tested processes. • RCS were the dominant reactive species contributing to more than 70% of CBZ removal in all three processes. • Compared to •OH, RCS had lower energy barrier and higher reactivity in main CBZ degradation pathways. • UV/chlorine processes produced 15 times higher ClO 3 − than in-situ chlorination. Chlorine has been widely used in different advanced oxidation processes (AOPs) for micropollutants removal. In this study, different chlorine-based AOPs, namely medium pressure (MP) UV/chlorine, low pressure (LP) UV/chlorine, and in-situ chlorination, were compared for carbamazepine (CBZ) removal efficiency, energy consumption, and disinfection by-products (DBPs) formation. All three processes could achieve nearly 100% CBZ removal, while the reaction time needed by in-situ chlorination was double the time required by UV/chlorine processes. The energy consumed per magnitude of CBZ removed (EE/O) of MP UV/chlorine was 13 times higher than that of LP UV/chlorine, and relative to that of in-situ chlorination process. Accordingly, MP and LP UV/chlorine processes generated one to two orders of magnitude more hydroxyl radicals (•OH) and reactive chlorine species (RCS) than in-situ chlorination. Besides, RCS were the dominant reactive species, contributing to 78.3%, 75.6%, and 71.6% of CBZ removal in MP, LP UV/chlorine, and in-situ chlorination, respectively. According to the Gibbs free energy barriers between CBZ and RCS/•OH calculated based on density functional theory (DFT), RCS had more reaction routes with CBZ and showed lower energy barrier in the main CBZ degradation pathways like epoxidation and formation of iminostilbene. When applied to secondary wastewater effluent, UV/chlorine and in-situ chlorination produced overall DBPs ranging from 104.77 to 135.41 µg/L. However, the production of chlorate during UV/chlorine processes was 15 times higher than that during in-situ chlorination. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, samples were taken from three locations, upstream to downstream, along the central route project of the China South to North Water Diversion (SNWD) scheme in summer and winter. These were used to reveal the variations of dissolved organic matter (DOM) during the water transfer process, and the effects of these variations on drinking water treatment and disinfection by-products formation potential (DBPs-FP). The results showed that polysaccharides accumulate in summer and reduce in winter with flow distance, which has an important effect on the overall properties of DOM, as well as on the performance of coagulation, ultrafiltration, and the formation of DBPs. Humic substances, and their hydrophilic content, also increased in summer and decreased in winter with flow distance. In contrast, the concentration of small organic substances (MW ⩽ 1000 Da) increased in both summer and winter with flow distance, which affected both nanofiltration (NF) membrane fouling and DBPs-FP. The results provide a useful case study of spatial and temporal changes in raw water DOM during long distance water transfer and their impact on the treatment and quality of drinking water from the SNWD. [ABSTRACT FROM AUTHOR]

BackgroundThe Qingcaosha Reservoir is facing issues of algal blooms and eutrophication, and the resulting increase in the level of chlorination disinfection by-products in the water has been a major concern. ObjectiveTo evaluate the impact of "Algae Monitoring and Control Program in Qingcaosha Reservoir" (hereinafter referred to as the program) on the control of trihalomethanes (THMs) in conventional finished water. MethodsFrom 2011 to 2019, water samples were collected from the Lujiazui Water Plant once per season, one sample each time, and the concentrations of four THMs (trichloromethane, dichlorobromomethane, monochlorodibromomethane, and tribromomethane) were measured in the samples. Using 2014 when the program was implemented as a cut-off point, the entire study period was divided into two phases: pre-implementation (2011–2013) and post-implementation(2014–2019). Segmented linear regression with interrupted time series analysis was applied to assess the concentrations and trends of THMs in the finished water before and after the program launch. ResultsThe concentration of total THMs in finished water increased by 1.561 µg·L−1 (P=0.010) for each season of time extension before launching the program. The change in the concentration of total THMs in finished water was not statistically significant after the program launch, but the THMs concentration showed a decreasing trend as the slope was −0.626 (P=0.001). From 2017 until the end of 2019, the average concentration of THMs in finished water of Lujiazui Water Plant dropped to 10 μg·L−1 or less.ConclusionsThe algae and eutrophication control measures in Qingcaosha Reservoir have achieved good results, controlling THMs in finished water at a low level, and the trend of THMs has changed from a yearly increase pattern before the program to a yearly decrease pattern after the program.

Swimming is a widely practiced exercise in modern society, where there is a heightened interest in health. The exceptional benefits of swimming are well-known, yet the issue of water quality management inevitably arises due to its nature as an aquatic exercise. Several studies reported that chlorine disinfectants commonly used in swimming pool water disinfection could degrade into toxic disinfection by-products (DBPs) and suggested that the DBPs might induce respiratory disorders, including asthma. Conversely, there were also reports that the DBPs had no significant effects on respiratory conditions. In this study, we investigated the influence of swimming exercise and DBPs on asthma. The decomposition products had little effect on the number of T cells in various immune organs. However, swimming exercise was found to increase the cell count in proportion to the exercise duration. Nevertheless, there were no significant changes in other immune cells and the secretion of asthma-related cytokines. These findings indicate that the effects of swimming pool DBPs on respiratory conditions during swimming exercise are either negligible or absent, and instead, the immunological benefits gained through consistent swimming exercise outweigh any potential drawbacks. HIGHLIGHTS Disinfection by-product (DBP) exposure did not cause lung damage in this model.; Inflammatory cytokine levels were unchanged due to DBP exposure, except IL-6.; There were no significant changes in asthma-related blood cell type distribution.; These results suggest that swimming exercise does not have an effect on asthma and may have a positive long-term effect on the immune system.;

Disinfection by-products (DBPs), generated from the reaction of disinfectants with DBP precursors, have been found to pose unintentional risks to human health. Considering that the concentration and speciation of DBPs formed during disinfection will be affected by the content and composition of dissolved organic matter (DOM), widespread concern about the characteristics of DBP precursors in water sources have been prompted. Three-dimensional excitation–emission matrix (EEM) can quickly and efficiently determine the properties and composition of DOM in water, and thus is generally used to investigate the origin of DBP precursors in water sources. This study overviews the fluorescent properties of different DBP precursors, summarizes the application of different EEM interpretation methods in DBP precursors and analyses the key factors affecting the correlation between the fluorescent components and DBP precursors (e.g., natural organic matter, algal organic matter, effluent organic matter and organic matter derived from other sources). A series of factors, including composition of fluorophores, bromide concentration, spatio-temporal characteristics and disinfectant types, could impact the correlation between DBP formation potential and fluorescent components. As for future research needs, it is of significance to select suitable fluorescence analysis methods and investigate the combination of EEM with other characterization technologies based on different situations. HIGHLIGHTS The main substances and sources of DBP precursors in water are introduced.; Fluorescence analysis methods for DBP precursor are summarized.; The fluorescence properties of DBP precursors from different sources are analyzed.; The correlation between fluorescent substances and DBP precursors are discussed.;

In this study, samples from the Yangtze River, Han River, and Liangzi Lake in Wuhan City were utilized to characterize the formation of disinfection by-products (DBPs) from chlorine-based disinfection residues in drinking water sources. The results indicated that the main DBPs in drinking water sources were trichloromethane (TCM) and trichloroacetic acid (TCAA). The generation of DBPs was significantly positively correlated with oxidative substances, aromatic compounds, pH, and ammonia nitrogen (NH3-N) content in the water. The concentration of TCAA increased from 0 to 2.45 ± 0.31 mg/L when the reaction time increased to 72 h. As the NaClO concentration increased from 5 mg/L to 15 mg/L, the concentrations of TCAA, TBM, and DCAN increased from 2.03 ± 0.04 mg/L, 0 mg/L, and 0 mg/L to 2.49 ± 0.34 mg/L, 0.21 ± 0.07 mg/L, and 0.10 ± 0.04 mg/L before decreasing to 1.75 ± 0.19 mg/L, 0.17 ± 0.07 mg/L, and 0.04 ± 0.05 mg/L, respectively. The orthogonal experimental results showed that Br−, NH3-N, and pH all had significant influences on the TCM generation, whereas temperature affected the formation of TCAA in the Han River. This work reveals the factors influencing the generation of DBPs from chlorine-based disinfection residues, offering a prevention and control method for DBPs in drinking water sources from a theoretical perspective.