Concentrations Of Trihalomethanes Research Articles

Removal of Trihalomethanes from Water using Modified Montmorillonite

Trihalomethanes (THMs) are formed during the water chlorination process through the reaction between chlorine and the organic materials. In this research, montmorillonite (MMT) and its modified form were used to remove the THMs from the water. The optimum conditions for the best adsorption capacity were evaluated using the Taguchi design of experiments. The result of comparing MMT with its modified sulfonated form (SMMT) indicated that SMMT is a more effective adsorbent than MMT. The evaluations showed that the optimum conditions for the THMs removal occur at 20 °C, 10 mg of adsorbent, 1 mg/L of THMs concentration, and 120 min for the adsorption time. The maximum adsorption capacity of CHCl3, CHBrCl2, CHBr2Cl, and CHBr3 was achieved: 0.49, 0.45, 0.43, and 0.38 mg/g at C0=0.10 mg/L; 1.71, 1.62, 1.56, and 1.45 mg/g at C0=0.50 mg/L; and 4.43, 4.35, 4.23, and 3.67 mg/g for C0=5.00 mg/L, respectively. The THMs adsorption was compared between SMMT, powdered activated carbon (PAC), and granular activated carbon (GAC) and the results showed that SMMT is as effective as PAC and better than GAC and its production cost is lower than for the activated carbon.

Modeling of Trihalomethanes in Benha Water Supply Network (Dept.P)

The presence of total trihalomethane (THMs) in Benha Water Supply Network (WSN) is determined and evaluated in this research. Six sampling points located an Different distances from the main water reservoirs, were selected in BWSN in order to follow the evolution | THMs. The gained information from the monthly sampling and laboratory analysis program was used to formulate relationship of total trihalomethanes (THMs) concentration in terms of initial chlorine dose, total organic carbon, bromide ion concentration, contact time, temperature, algae. and pH. To define the accuracy level of the developed model. the predicted (Mx concentrations from the developed model were compared to actual TUMS concentrations measured during the monitoring period. The developed mathematical model and software (EPANET), which was used to determine water age. were used to predict THMs concentrations throughout BWSN. The results showed close agreement between the measured and calculated THMs concentration. Hence the difference in the average calculated values and measured values during the study period ranged from (4.6% to 9.9 %). The model can provide reasonable results for most of the functioned variables and can be used to have a rapid assessment ol'llie trihalomethanes formation.

A multivariate Bayesian network analysis of water quality factors influencing trihalomethanes formation in drinking water distribution systems

Controlling disinfection by-products formation while ensuring effective drinking water disinfection is important for protecting public health. However, understanding and predicting disinfection by-product formation under a variety of conditions in drinking water distribution systems remains challenging as disinfection by-product formation is a multifactorial phenomenon. This study aimed to assess the application of Bayesian Network models to predict the concentration of trihalomethanes, the dominant halogenated disinfection by-product class, using various water quality parameters. Naïve Bayesian and semi-naïve Bayesian models were constructed from Sydney and South East Queensland datasets across 15 drinking water distribution systems in Australia. The targeted variable, total trihalomethanes concentration, was discretised into 3 bins (<0.1 mg L−1, 0.1 – 0.2 mg L−1 and >0.2 mg L−1). The Bayesian network structures were built using water quality parameters including concentrations of individual and total trihalomethanes, disinfectant species (free chlorine, monochloramine, dichloramine, total chlorine), nitrogen species (free ammonia, total ammonia, nitrate, nitrite), and other physical/chemical parameters (temperature, pH, dissolved organic carbon, total dissolved solids, conductivity and turbidity). Seven performance parameters, including predictive accuracy and the rates of true and false positive and negative results, were used to assess the accuracy and precision of the Bayesian network models. After evaluating the model performance, the optimum models were selected to be Bayesian network augmented naïve models. These were observed to have the highest predictive accuracies for Sydney (78%) and South East Queensland (94%). Although disinfectant residuals are among the key variables that lead to trihalomethanes formation, potential concentrations of trihalomethanes in distribution systems can be more confidently predicted, in terms of probability associated with a wider range of water quality variables, using Bayesian networks. The modelling procedure developed in this work can now be applied to develop system-specific Bayesian network models for trihalomethanes prediction in other drinking water distribution systems.

Affection of multiple feeding water supply network on the concentration of trihalomethane. (Dept.C)

The previous researches studied the concentration of (THMs) in water networks having only one feeding source. This research illustration the effect of multiple feeding source for water supply network on the concentration of (THMs). This research focuses on the evaluation and assessment of THMs contamination in Fayoum Water Supply Network. To investigate the influence of multiple feeding source for a distribution water network on the THMs contaminant, an intensive 5-months sampling programmed was undertaken. pH, Free Chlorine, Bromine, Temperature, Travel Time, TOC and THMs were all measured. Results showed that the concentration of THMs in all the selected points in the distribution network were less than the maximum acceptable concentration for THMS, and the chloroform is the predominant THMS compound (it represents an average of 50% of total THMS ). It was noticed that an average chlorine consumption of 0.1 mg/L leads to the increase of THMs concentration by 2.0 to 2.5 μg/L. An increase in temperature by 5°C leads to the increase of THMs concentration by 27% to 32%. The higher the initial THMs formation after post-chlorination, the lower the relative increase in THMs in the distribution system. The mixing between two feeding sources is better for the distribution network not only for flexibility in operation, but also for the properties of the water and the concentration of THMs at point of mixing between conventional treatment plant & small plant is less than the concentration of THMS at point in distribution network for small plant only.

Effects of powdered activated carbon and calcium on trihalomethane toxicity of zebrafish embryos and larvae in hybrid membrane bioreactors

This study investigated the effect of powdered activated carbon and calcium on trihalomethane toxicity in zebrafish embryos and larvae in hybrid membrane bioreactors. Two hybrid membrane bioreactors were configured with the addition of powdered activated carbon or calcium to reduce the trihalomethane formation potential. Trihalomethane formation decreased by approximately 37.2% and 30.3% in membrane bioreactor-powdered activated carbon and membrane bioreactor-calcium, respectively. Additionally, the toxic effect of trihalomethane formation was examined on zebrafish embryos and larvae. About 35% of the embryos exposed to trihalomethanes (800 ppb) showed signs of deformation, with the majority displaying coagulation within 24 h after exposure. Color preference tests, which were conducted to identify any abnormal activities of the embryos, showed an increase in preference from short to longer wavelengths upon exposure to high levels of trihalomethanes. This may indicate damage to the optical organs in zebrafish when exposed to trihalomethanes. Behavioral analysis showed reduced mobility of zebrafish larvae under different trihalomethane concentrations, indicating a decrease in the average activity time with an increasing trihalomethane concentration. The membrane bioreactor effluents were toxic to zebrafish embryos and larvae in the presence of high trihalomethane concentrations. To understand the mechanism behind trihalomethane toxicity, further studies are needed.

Global assessment of trihalomethanes in drinking water

BACKGROUND. Chlorination of drinking water is a major public health intervention to avoid water-borne infections. Disinfection generates undesired by-products such as trihalomethanes (THMs), some of which are carcinogenic. Global information on population exposure to disinfection by-products (DBPs) in water is lacking. We developed global country-wide estimates of the concentrations of THMs in drinking water as a marker of DBP exposure. METHODS. In this global study we collected information about the regulatory status of DBPs and concentrations of total and specific THMs (chloroform, bromoform, dibromochloromethane, bromodichloromethane) in drinking water from the latest year available. Global THM data were collected using a structured questionnaire and database from key national contacts and experts (national agencies, universities, water utilities). We conducted on-line searches of published reports, research studies, and grey literature. We calculated population-weighted average THM levels in each country. Data quality analysis considered the percentage of population covered, the number of water samples, and the source of information used. RESULTS. From the 121 countries included, 90 (74%) regulate THMs in drinking water. In countries with THM regulations, 42 (47%) conduct routine monitoring. Data collection is ongoing. Average THM levels (in μg/L) varied e.g., from 0.02 in Denmark, 0.2 in Netherlands, 24 in UK, 27 in Canada, 34 in USA to 60 in South Africa, and 72 in Australia. Very high levels above 600 were observed in certain areas in India. There were major gaps in global coverage, primarily in Africa, but also in Asia. DISCUSSION. This is the first global assessment of THM levels in drinking water. National data were available for most high and several middle income countries. Results will become open access, and are expected to promote research and policy developments, including better estimates of global burden of disease, comparative risk assessment, and will facilitate control of DBPs in drinking water.

Impact of swimming pool water treatment system factors on the content of selected disinfection by-products

Recommendations regarding disinfection by-products (DBPs) in pool waters consider the content of trihalomethanes (THMs) and combined chlorine (CC) as indicators of DBPs based on which the health risk for swimmers and staff of pool facility can be determined. However, the content of DBPs in swimming pools depends on many factors. In this paper, the influence of selected factors (physicochemical parameters of water and technological parameters) on the content of THMs and CC in pool water was determined. During the 6-month period, 9 pools of various functions were analyzed. The water in pools was subjected to the same method of treatment. The content of THMs and CC was compared against the content of organic matter, free chlorine and nitrates, pH, temperature, redox potential and turbidity, technological, and operational parameters. The THM content did not exceed the limit value of 0.1 mg/L. The content of CC varied significantly, from 0.05 to 1.13 mg Cl2/L. It was found that a very large water volume per person, in comparison to a very small one, contributed to the low content of CC and THMs. The high load expressed as m3 of water per person or m2 of water per person and the specific function of hot tubs (HT1 and HT2) led to the average concentration of CC in these pools exceeding 0.3 mg Cl2/L. The THM concentrations in hot tubs (especially in HT1) were also among the largest (0.038–0.058 mg/L). In terms of the analyzed microbiological indicators, the quality of the tested pool water samples was not in doubt. It was found that the purpose of the pool, its volume, and number of swimmers should be the key parameters that determine the choice of methods of water treatment. The research on the pool water quality in the actual working conditions of swimming pool facilities is necessary due to the need to preserve the health safety of swimmers and staff.

Temporospatial variation and health risk assessment of trihalomethanes (THMs) in drinking water (northwest Iran)

Trihalomethanes (THMs) are one of the most common classes of disinfection by-products. In this study, the temporospatial trends and health risks due to exposure to THMs in the Tabriz water distribution network were investigated. THM series were analyzed using gas chromatography equipped with electron capture detector. The non-carcinogenic and carcinogenic risks due to exposure to THMs were calculated using Monte Carlo simulations. Mean concentrations of THMs in winter and spring were 10.2 ± 9.3μg/l and 252 ± 185.9μg/l, respectively. More than 80% of THMs identified were bromodichloromethane. The mean values of lifetime cancer risk (LTCR) of THMs were calculated as 4.23E-06 and 2.38E-04 for winter and spring, respectively. This study showed that there were noticeable levels of THMs in Tabriz water distribution network, especially in the center of the city. Although the non-cancer risk through THMs was below permissible recommended levels, the cancer risk likely remains due to high levels of THMs in some locations.

Pilot Test on Pre-Swim Hygiene as a Factor Limiting Trihalomethane Precursors in Pool Water by Reducing Organic Matter in an Operational Facility.

Pool water must be constantly disinfected. Chlorine compounds used to disinfect pools react with organic substances such as sweat, urine, and personal care products introduced into pool water by users and results in the formation of disinfection byproducts. Trihalomethanes (THM), including chloroform and dissolved organic carbon (DOC) concentrations, were quantified using a two-stage process: determining initial THM and chloroform levels; then searching for a cheap and easy-to-use method to improve water quality. The method proposed here to limit THM and DOC concentrations in water is controlled showering. At three swimming pool facilities, chloroform concentrations (13.8 ± 0.33 µg/L, 15.5 ± 0.44 µg/L, and 13.9 ± 0.06 µg/L) were below the threshold concentration of 30 μg/L. At a fourth facility, however, the chloroform concentration exceeded that threshold (40.7 ± 9.68 μg/L) when showering was not controlled. Those conditions improved after the introduction of a mandatory shower; concentrations of DOC, THMs, and chloroform all decreased. The chloroform concentration decreased to 29.4 ± 3.8 μg/L, the THM concentration was 31.3 ± 3.9 μg/L, and the DOC concentration was 6.09 ± 0.05 mg/L. Pilot tests were carried out at real facilities to determine whether the control of pre-swim hygiene was possible. The introduction of proper pre-swim hygiene limited the concentration of DOC in water and can lead to a healthier environment for everyone attending the swimming facility.

Spatial and Temporal Variability in Trihalomethane Concentrations in the Bromine-Rich Public Waters of Perth, Australia.

High concentrations of trihalomethanes (THMs) in public water supplies potentially pose a health hazard, but exposure assessment remains a complex task. To interpret research findings and monitoring data for THMs, it is important to evaluate spatial and temporal variations in both total THM and the individual constituent compounds (including brominated species). We therefore aimed to determine the concentrations, and spatial and temporal variability of concentrations, of THMs public water supplies in Perth, Western Australia, which is known historically to have high brominated THM concentrations. We analysed water samples from 21 water distribution zones around Perth (including Busselton and Bunbury) across different seasons over a period of two years. A total of 250 samples provided a median total THM of 72 µg/L (range of 0–157 µg/L), which falls well within Australia’s National Health and Medical Research Council guidelines. The concentration of all species, including brominated forms, also fell the World Health Organization’s guidelines. Total THM concentrations were typically higher in spring and summer. A high degree of spatial variability was detected and appears to relate to the source water. Both the temporal and spatial variability in THM concentrations have implications for epidemiological studies, and monitoring.

Trimester-Specific Blood Trihalomethane and Urinary Haloacetic Acid Concentrations and Adverse Birth Outcomes: Identifying Windows of Vulnerability during Pregnancy

Background:Some disinfection by-products (DBPs) are reproductive and developmental toxicants in laboratory animals. However, studies of trimester-specific DBP exposure on adverse birth outcomes in humans are inconsistent.Objective:We examined whether trimester-specific blood and urinary biomarkers of DBP were associated with small for gestational age (SGA), low birth weight (LBW), and preterm birth.Methods:A total of 4,086 blood and 3,951 urine samples were collected across pregnancy trimesters among 1,660 mothers from Xiaogan City, China. Blood samples were quantified for biomarkers of trihalomethanes (THMs): chloroform (TCM), bromodichloromethane, dibromochloromethane, and bromoform. Urine samples were quantified for biomarkers of haloacetic acids (HAA): dichloroacetic acid and trichloroacetic acid. Birth outcomes were abstracted at delivery from medical records. We used Poisson regression models with log link functions to estimate risk ratios (RRs) and 95% confidence intervals (CIs) for SGA, LBW, and preterm birth across tertiles (or categories) of DBP biomarker concentrations measured across pregnancy trimesters. We also examined the relative exposure differences across gestation comparing adverse outcomes with normal births using mixed-effects models.Results:Blood TCM concentrations in the second trimester were associated with an elevated risk of SGA comparing middle vs. lowest (RR, 2.34; 95% CI: 1.02, 5.35) and highest vs. lowest (RR, 2.47; 95% CI: 1.09, 5.58) exposure groups. Third-trimester blood TCM concentrations were also associated with an increased risk of SGA comparing the second tertile with the first (RR, 2.61; 95% CI: 1.15, 5.92). We found that maternal blood TCM concentrations were significantly higher for SGA compared with non-SGA births across the period from 23 to 34 wk gestation. Other blood and urinary DBP biomarkers examined were unrelated to SGA, LBW, or preterm birth.Conclusion:Blood TCM concentrations in mid to late pregnancy were associated with an increased risk of SGA, whereas other biomarkers of DBPs examined across pregnancy were not associated with birth outcomes. https://doi.org/10.1289/EHP7195

Sorptive removal of disinfection by-product precursors from UK lowland surface waters: Impact of molecular weight and bromide

The current study compared the impact of three different unit processes, coagulation, granular activated carbon (GAC), and a novel suspended ion exchange (SIX) technology, on disinfection by-product formation potential (DBPFP) from two UK lowland water sources with medium to high bromide content. Specific attention was given to the influence of the organic molecular weight (MW) fraction on DBPFP as well as the impact of bromide concentration. Whilst few studies have investigated the impact of MW fractions from Liquid Chromatography with Organic Carbon Detection (LC-OCD) analysis on dissolved organic carbon (DOC) removal by different processes, none have studied the influence of DOC MW fractions from this analysis on DBP formation. The impact of higher bromide concentration was to decrease the total trihalomethane (THM) and haloacetic acid (HAA) mass concentration, in contrast to previously reported studies. Results indicated that for a moderate bromide concentration source (135 μg/L), the THM formation potential was reduced by 22% or 64% after coagulation or SIX treatment, respectively. For a high bromide content source (210 μg/L), the THM formation potential removal was 47% or 69% following GAC or SIX treatment, respectively. The trend was the same for HAAs, albeit with greater differences between the two processes/feedwaters with reference to overall removal. A statistical analysis indicated that organic matter of MW > 350 g/mol had a significant impact on DBPFP. A multiple linear regression of the MW fractions against DBPFP showed a strong correlation (R2 between 0.90 and 0.93), indicating that LC-OCD analysis alone could be used to predict DBP formation with reasonable accuracy, and offering the potential for rapid risk assessment of water sources.

Оценка эффективности применения преаммонизации в целях снижения канцерогенного риска от тригалогенметанов в питьевой воде

In most Russian regions there is still a pressing issue related to providing population with high quality and safe drinking water. Up to now, chlorination has been the primary technique applied to disinfect drinking water as it is highly efficient, reliable, and relatively cheap. However, when chlorine is used to disinfect natural water that contains organic pollutants, it results in risks of by-products occurrence. These products are trihalomethanes, epigenetic carcinogenesis promoters that cause elevated carcinogenic risks under oral, inhalation, and subcutaneous exposure. Our research goal was to hygienically assess efficiency of pre-ammonization applied in water treatment procedures in order to prevent occurrence of carcinogenic organic chlorine compounds during chlorination and to minimize carcinogenic risks. We determined trihalomethanes and residual chlorine contents in model samples of natural water taken from a surface water source after chlorination with different doses of chlorine. We examined 52 pair parallel samples that had undergone pre-ammonization with ammonia sulfate and control ones. Trihalomethanes concentrations were determined in model water samples with gas-liquid chromatography. Basing on the results obtained via experiments on laboratory chlorination of river water, we determined quantitative characteristics and built regression models showing dependence between concentrations of organic chlorine compounds occurring due to chlorination (chloroform, dichlorobrommethane, dibromchloromethane) and chlorine doses and preammonization parameters. It was established that pre-ammonization was the most efficient in terms of preventing trihalomethanes occurrence under such disinfection modes when contents of residual active chlorine didn’t exceed recommended levels (0.8–1.2 mg/L). Basic ways to minimize carcinogenic risks caused by trihalomethanes are systemic control over their contents in drinking water during social and hygienic monitoring procedures; preliminary ammonization of water taken from surface water sources; prevention of unjustified hyper-chlorination; preliminary deep purification of initial water; disinfection with ultrasound radiation instead of preliminary chlorination; etc.

Assessing efficiency of pre-ammonization aimed at reducing carcinogenic risks caused by trihalomethanes in drinking water

In most Russian regions there is still a pressing issue related to providing population with high quality and safe drinking water. Up to now, chlorination has been the primary technique applied to disinfect drinking water as it is highly efficient, reliable, and relatively cheap. However, when chlorine is used to disinfect natural water that contains organic pollutants, it results in risks of by-products occurrence. These products are trihalomethanes, epigenetic carcinogenesis promoters that cause elevated carcinogenic risks under oral, inhalation, and subcutaneous exposure. Our research goal was to hygienically assess efficiency of pre-ammonization applied in water treatment procedures in order to prevent occurrence of carcinogenic organic chlorine compounds during chlorination and to minimize carcinogenic risks. We determined trihalomethanes and residual chlorine contents in model samples of natural water taken from a surface water source after chlorination with different doses of chlorine. We examined 52 pair parallel samples that had undergone pre-ammonization with ammonia sulfate and control ones. Trihalomethanes concentrations were determined in model water samples with gas-liquid chromatography. Basing on the results obtained via experiments on laboratory chlorination of river water, we determined quantitative characteristics and built regression models showing dependence between concentrations of organic chlorine compounds occurring due to chlorination (chloroform, dichlorobrommethane, dibromchloromethane) and chlorine doses and preammonization parameters. It was established that pre-ammonization was the most efficient in terms of preventing trihalomethanes occurrence under such disinfection modes when contents of residual active chlorine didn’t exceed recommended levels (0.8–1.2 mg/L). Basic ways to minimize carcinogenic risks caused by trihalomethanes are systemic control over their contents in drinking water during social and hygienic monitoring procedures; preliminary ammonization of water taken from surface water sources; prevention of unjustified hyper-chlorination; preliminary deep purification of initial water; disinfection with ultrasound radiation instead of preliminary chlorination; etc.

Approaches to Regulating Organic Carbon and the Necessity of Its Obligatory Monitoring in Drinking Water

Background: Current accumulation of organogenic elements in surface waters is mainly attributed to intensive anthropogenic activities. Waterborne organic matter may endanger human health when using surface waters for drinking and recreational purposes. Applied techniques of water treatment fail to ensure complete water purification and part of organic substances (their low molecular weight fraction) still remains. Chlorination of drinking water can generate a variety of halogenated by-products having adverse health effects in humans including carcinogenic ones. Our objective was to substantiate the reference value for total organic carbon (TOC) in water disinfected by chlorine. Materials and methods: We analyzed the results of laboratory testing of surface and treated water samples taken in Yekaterinburg in 2013–2014 and 2017, carried out health risk assessment, and built predicative models of by-products formation. Results: We established that, following chlorination, TOC concentrations became 1.5 times lower while chloroform and total trihalomethane concentrations became 24.5–80.2 and 22.9–54.5 times higher than initial values, respectively. The most significant non-carcinogenic risks were estimated for children aged 0-6 years from exposures to chloroform (HQ = 1.150). Individual carcinogenic risks from exposures to bromoform and dibromochloromethane as measured in water before its supplying to the distribution system, referred to the first value range (less than 1×10–6) while risks from bromodichloromethane and chloroform exposures fell in the second range (from 1×10–6 to 1×10–4). The mathematical model of the correlation between predictors (temperature, reaction time, pH, and certain chemical compounds) and levels of by-products was built. Conclusions: Our model makes it possible to predict generation of organochlorine compounds at the design stage of water treatment technique. Total organic carbon is an important indicator that should be monitored at the stages of water treatment to ensure safety of drinking water and efficiency of its disinfection.

Analysis of the Kinetics of Swimming Pool Water Reaction in Analytical Device Reproducing Its Circulation on a Small Scale.

The most common cause of diseases in swimming pools is the lack of sanitary control of water quality; water may contain microbiological and chemical contaminants. Among the people most at risk of infection are children, pregnant women, and immunocompromised people. The origin of the problem is a need to develop a system that can predict the formation of chlorine water disinfection by-products, such as trihalomethanes (THMs). THMs are volatile organic compounds from the group of alkyl halides, carcinogenic, mutagenic, teratogenic, and bioaccumulating. Long-term exposure, even to low concentrations of THM in water and air, may result in damage to the liver, kidneys, thyroid gland, or nervous system. This article focuses on analysis of the kinetics of swimming pool water reaction in analytical device reproducing its circulation on a small scale. The designed and constructed analytical device is based on the SIMATIC S7-1200 PLC driver of SIEMENS Company. The HMI KPT panel of SIEMENS Company enables monitoring the process and control individual elements of device. Value of the reaction rate constant of free chlorine decomposition gives us qualitative information about water quality, it is also strictly connected to the kinetics of the reaction. Based on the experiment results, the value of reaction rate constant was determined as a linear change of the natural logarithm of free chlorine concentration over time. The experimental value of activation energy based on the directional coefficient is equal to 76.0 . These results indicate that changing water temperature does not cause any changes in the reaction rate, while it still affects the value of the reaction rate constant. Using the analytical device, it is possible to constantly monitor the values of reaction rate constant and activation energy, which can be used to develop a new way to assess pool water quality.

Removal of the precursors of regulated DBPs and TOX from surface waters and wastewater effluents using mixed anion exchange resins

Both organic and inorganic precursors play important roles in the formation and speciation of disinfection by-products (DBPs). This study aimed to investigate the efficacy of three different anion exchange resins for removing both organic and inorganic DBP precursors simultaneously in a single treatment system. Resins in the single (Purolite®-Br, MIEX®-Br, and MIEX®-Gold) and mixed (Purolite®-Br with MIEX®-Gold and MIEX®-Br with MIEX®-Gold) application modes were tested and compared for the removal of dissolved organic carbon (DOC), bromide (Br−), and iodide (I−) from a raw source water and a treated wastewater effluent. Uniform formation condition (UFC) tests were conducted to measure the concentrations of trihalomethanes (THM4), haloacetic acids (HAA9), haloacetonitriles (HAN6), and total organic halides (TOX): total organic chlorine (TOCl), total organic bromine (TOBr), and total organic iodine (TOI) before and after the anion exchange resin treatments. The anion exchange treatment substantially lowered the DOC, UV254 absorbing matter, dissolved nitrogen (DN), Br−, and I−. Consequently, the formation of THM4, HAA9, HAN6, and TOX in the examined chlorinated water samples were reduced significantly. The maximum reduction in THM4 and TOX (66–69% and 61%, respectively) from wastewater effluent was achieved by the mixed resin system, which also reduced the THM4 and TOX by 77% and 77%, respectively, from raw source water. Overall, mixed resin systems (a DOC-selective and a Br-selective resin) resulted in lower amounts of THM4 and HAA9 formation during subsequent chlorination with lower bromine incorporation as compared to single resin systems. Furthermore, they exhibited lower TOBr formation, while TOI formation was not detected.

Multi-route human health risk assessment from trihalomethanes in drinking and non-drinking water in Abadan, Iran

Natural organic matter reacted with chlorine used for disinfection, and finally, trihalomethanes (THMs) are formatted. The main purpose of this study was to determine four THM concentrations and human health cancer risk and non-cancer risk assessment from exposure through oral ingestion, dermal contact, and inhalation for males and females in Abadan. Two sampling sites were selected, and five samples before and after treatment by two different water treatment systems (RO and ion exchange) were collected every week. Results showed that total THM concentrations before and after treatment by RO were 98.1 and 8.88 μg/L, and ion exchange ranged between 101.9 and 14.96 μg/L, respectively, that before treatment was upper than the maximum of 80 mg/L recommended by USEPA. Inhalation was the primary route of exposure by around 80–90% of cancer risk. Total cancer risk was higher than the USEPA acceptable limit of 10−6 via three exposure routes. Oral route has the higher hazard index values than dermal ways.

Toxicity of chlorinated algal-impacted waters: Formation of disinfection byproducts vs. reduction of cyanotoxins

Seasonal algal blooms in surface waters can impact water quality through an input of algal organic matter (AOM) to the pool of dissolved organic matter as well as the release of cyanotoxins. The formation and speciation of disinfection byproducts (DBPs) during chlorination of algal-impacted waters, collected from growth of Microcystis aeruginosa were studied. Second-order rate constants for the reactions of microcystins (MCs) with chlorine and bromine were determined. Finally, the toxicity of chlorinated algal-impacted waters was evaluated by Chinese hamster ovary (CHO) cytotoxicity and genotoxicity assays. Under practical water treatment conditions, algal-impacted waters produced less regulated trihalomethanes (THMs) and haloacetic acids (HAAs), haloacetonitriles (HANs), and total organic halogen (TOX) than natural organic matter (NOM). For example, the weight ratios of DBP formation from AOM to NOM (median levels) were approximately 1:5, 1:3, 1:2 and 1:3 for THMs, HAAs, HANs, and TOX, respectively. Increasing initial bromide level significantly enhanced THM and HAN concentrations, and therefore unknown TOX decreased. The second-order rate constant for the reactions of MC-LR (the most common MC species) with chlorine was 60 M−1 s−1 at pH 7.5 and 21 °C, and the rate constants for MC congeners follow the order: MC-WR > MC-LW > MC-YR > MC-LY > MC-LR ≈ MC-RR. The reaction rate constant of bromine with MC-LR is two orders of magnitude higher than that of chlorine. Unchlorinated algal-impacted waters were toxic owning to the presence of MCs, and chlorination enhanced their cytotoxicity and genotoxicity due to the formation of toxic halogenated DBPs. However, the toxicity of treated waters depended on the evolution of cyanotoxins and formation of DBPs (particularly unknown or emerging DBPs).

Assessment of exposure of children swimmers to trihalomethanes in an indoor swimming pool.

This study aimed to understand the exposure levels of trihalomethanes (THMs) in an indoor swimming pool and calculate the risks of exposure to THMs, based on the presence of each THM species, of children swimmers aged 6-17, in Beijing, China. We obtained exposure factors for the children through questionnaires and measured THM concentrations through laboratory tests, and we combined the results with an exposure model to calculate the risks, with consideration of different exposure routes (oral ingestion, inhalation and dermal absorption). In terms of exposure factors for the swimmers aged 6-17, the average body weight, exposure duration, exposure frequency, swimming time, shower time, changing time, warm-up exercise and rest time, skin surface area and ingestion rate of pool water were 40.46 kg, 2.70 years, 96 events/year, 64.03 min/event, 17.04 min/event, 15.31 min/event, 12.71 min/event, 1.37 m2 and 48.93 ml/event, respectively. The THM concentrations in swimming pool water, shower water, swimming pool air and locker room air were 67.17 μg/L, 12.64 μg/L, 358.66 μg/m3 and 40.98 μg/m3, respectively. The average cancer risk of THMs was 5.44 × 10-6, which is an unacceptable risk according to the United State Environmental Protection Agency (USEPA) Guidelines. The average hazard index was 0.007, i.e., less than 1, indicating that the noncancer risk was acceptable. Chloroform (TCM) was the main substance in four species of THMs and inhalation exposure was the main exposure pathway. The risk of cancer and noncancer from inhalation exposure to THMs accounts for 97-99% of the total risk. As a result, the disease control authorities and administrative department should pay attention to the health and safety of swimming facilities and, at the same time, establish standards for THMs in the air through further research.