Production Of Trihalomethanes Research Articles

A study for producing drinking water with safe trihalomethane concentrations

This article investigates trihalomethanes (THMs) production and simulates water age in Assiut drinking water system using WaterCAD software. Pre-chlorinated water samples were collected from Nazlet Abdellah water treatment plant and post-disinfected with chlorine/chloramines with different chlorine-to-nitrogen ratios (Cl2/N). Experiments have examined varying residence times, ratios of Cl2/N, pH conditions, and storage containers’ type on THMs formation. The results showed that as the residence time increased, THMs concentrations increased. Water age in Assiut drinking water distribution network reaches more than 10 h. Using chloramines instead of free chlorine for post-disinfection resulted in lowering THMs concentrations to 58.9 % after 48 h of disinfection. Ratios of Cl2/N (2:1–6:1) were comparable and effective on lowering THMs concentrations, and the most effective ratio was 4:1. Also, as the pH increased, the THMs increased. The measured THMs concentrations in chloraminated water stored in glass and plastic bottles were approximately the same.

UV and UV/H2O2 Treatment: The Silver Bullet for By-product and Genotoxicity Formation in Water Production

Since Rook showed the production of trihalomethanes by drinking water chlorination, reaction product formation by chemical disinfection/oxidation has been thoroughly investigated. Originally, the focus was on the formation of individual organic products. After chlorination, trihalomethanes (THMs), haloacetic acids (HAAs) and many other halogenated compounds were found. After ozonation, ultraviolet (UV) disinfection and advanced oxidation, biodegradable organic by-products such as carboxylic acids were identified. All reaction products were formed by reaction with the organic water matrix (natural organic matter). Formation of reaction products from the inorganic water matrix proved to be an important issue as well. By ozonation and ozone-based advanced oxidation processes bromate was formed in bromide-rich water. By UV and UV/H2O2 treatment, nitrite was formed in nitrate rich water, especially when medium pressure (MP) UV lamps were applied. In addition to chemical characterization of individual reaction products the side effects of disinfection/ oxidation were investigated by genotoxicity testing. After chlorination a high response was found in the classic Ames test. After ozone and ozone based advanced oxidation a decrease of the response in the classic Ames test was observed, while after UV disinfection and UV-based advanced oxidation no significant effect was found. Modified genotoxicity testing such as in vitro Ames-II has been developed and applied on UV/H2O2-treated water. Once again no or just a small significant genotoxic response was observed after MP UV/H2O2 treatment in a system equipped with natural quartz sleeves. However, a substantially higher response was found after MP UV/H2O2 treatment in a system equipped with synthetic sleeves with a higher transmittance at lower wavelengths. The genotoxic response and the nitrite formation increased in the same order of magnitude, suggesting a relationship with the UV photolysis of nitrate. This was confirmed by UV photolysis of natural organic matter (NOM) and nitrate containing reconstituted water. The genotoxic effect was removed completely by post-treatment with granular activated carbon (GAC) filtration and/or dune infiltration.

CLIMATE CHANGE AND INCREASED PRECIPITATIONS: THE IMPACT OF HEAVY RAINFALLS ON SURFACE WATER TOTAL ORGANIC CARBON (TOC) AND RESULTING HUMAN EXPOSURE TO TRIHALOMETHANES

Background and aims: Several studies suggest that climate change will be accompanied with increased precipitations. Heavy rainfalls can impact surface water total organic carbon (TOC) and, upon treatment, lead to higher trihalomethane levels in drinking water. These meteorological events could therefore exacerbate human exposure to these toxic disinfection by-products. This study aimed at i) assessing the impact of heavy rainfalls on surface water TOC and ii) evaluating subsequent exposure to chloroform and its internal dose metrics in humans. Methods: Surface water TOC was measured in samples taken from an established sampling point used for drinking water production in a small river in Brittany (France) during dry days and following high precipitations (> 10 mm). Trihalomethane production during water treatment was estimated based on TOC levels, temperature and chlorine dose using an established multivariate model. Finally, drinking water chloroform levels were used to construct different scenarios of exposure (i.e., water consumption, shower/bath and inhalation) in newborns, children, adults and pregnant women using a published physiologically based pharmacokinetic (PBPK) model. Results: Following high precipitations, surface water TOC increased from a median of 6.2 to 8.9 mg/L. Consequently, median total trihalomethane levels in drinking water were estimated to increase from 29.7 to 33.1 µg/L. Human exposures to chloroform after > 10 mm rainfalls increased hepatic metabolite levels by 11 % when compared to levels reached during dry days. This increase did not vary substantially between exposure routes or physiologic condition. Conclusions: This study suggests that the occurrence of heavy rainfalls can increase surface water TOC levels. The higher levels of trihalomethanes in drinking water following these precipitations may lead to increased tissue levels in humans. In the context of climate change, risk assessors may need to consider higher exposure to drinking water contaminants.

Disinfection by-product formation and mitigation strategies in point-of-use chlorination with sodium dichloroisocyanurate in Tanzania.

Almost a billion persons lack access to improved drinking water, and diarrheal diseases cause an estimated 1.87 million deaths per year. Sodium dichloroisocyanurate (NaDCC) tablets are widely recommended for household water treatment to reduce diarrhea. Because NaDCC is directly added to untreated water sources, concerns have been raised about the potential health impact of disinfection by-products. This study investigated trihalomethane (THM) production in water from six sources used for drinking (0.6-888.5 nephelometric turbidity units) near Arusha, Tanzania. No sample collected at 1, 8, and 24 hours after NaDCC addition exceeded the World Health Organization guideline values for either individual or total THMs. Ceramic filtration, sand filtration, cloth filtration, and settling and decanting were not effective mitigation strategies to reduce THM formation. Chlorine residual and THM formation were not significantly different in NaDCC and sodium hypochlorite treatment. Household chlorination of turbid and non-turbid waters did not create THM concentrations that exceeded health risk guidelines.

Impact of Booster Chlorination on Chlorine Decay and THM Production: Simulated Analysis

The effect of conventional and booster chlorination on chlorine residuals and trihalomethane (THM) formation in drinking water distribution systems was modeled using the EPANET hydraulic modeling software. The model results suggest that booster chlorination may allow utilities to meet disinfection goals better by carrying chlorine residuals to remote points in the distribution system while lowering the total mass of chlorine applied to the system. The model results suggest that booster chlorination may provide the greatest advantages to points in the distribution system located near storage tanks by providing a more consistent chlorine residual and possibly reducing THM formation. A new version of the EPANET model, the EPANET Multispecies model, was also used to compare chlorine decay due to reactions in the bulk fluid and reactions occurring at the pipe wall. The results suggest that chlorine decay due to wall reactions can be very significant at remote points in the distribution system. Additionally, if THMs are assumed to form primarily through reactions in the bulk fluid, use of the new EPANET Multispecies software allows for calculation of THM formation based solely on chlorine reactions in the bulk fluid rather than on overall chlorine decay.

Combined preoxidation by permanganate and chlorine in enhancing the treatment of surface water

AbstractBACKGROUND: Combined use of permanganate and chlorine has been shown to have synergistic action in disinfection. However, according to the literature the effects of combined preoxidation on coagulation and filtration have not been thoroughly investigated.RESULTS: Laboratory and pilot experiments were conducted to evaluate the effect of the combined preoxidation by permanganate and chlorine on the treatment of River Luan water. Based on the reduction of the residual turbidity and UV254 after sedimentation and filtration, the optimum dosages of permanganate and chlorine were selected. The improvement of treated water quality was also achieved in the pilot processes. Permanganate reduced the amount of chlorine, while it enhanced chlorination and reduced trihalomethane production. The enhanced treatment efficiency could be explained by the synergistic effect of the preoxidants themselves and the effect of chlorine and intermediates such as hydrous manganese dioxide, which was formed in situ by permanganate reduction.CONCLUSION: Laboratory and pilot studies demonstrated that combined preoxidation by permanganate and chlorine could enhance water treatment. Copyright © 2009 Society of Chemical Industry

Characteristics of trihalomethane (THM) production and associated health risk assessment in swimming pool waters treated with different disinfection methods

Swimming pool water must be treated to prevent infections caused by microbial pathogens. In Korea, the most commonly used disinfection methods include the application of chlorine, ozone/chlorine, and a technique that uses electrochemically generated mixed oxidants (EGMOs). The purpose of this study was to estimate the concentrations of total trihalomethanes (TTHMs) in indoor swimming pools adopting these disinfection methods, and to examine the correlations between the concentrations of THMs and TTHMs and other factors affecting the production of THMs. We also estimated the lifetime cancer risks associated with various exposure pathways by THMs in swimming pools. Water samples were collected from 183 indoor swimming pools in Seoul, Korea, and were analyzed for concentrations of each THM, TOC, and the amount of KMnO 4 consumption. The free chlorine residual and the pH of the pool water samples were also measured. The geometric mean concentrations of TTHMs in the swimming pool waters were 32.9 ± 2.4 µg/L for chlorine, 23.3 ± 2.2 µg/L for ozone/chlorine, and 58.2 ± 1.7 µg/L for EGMO. The concentrations of THMs differed significantly among the three treatment methods, and the correlation between THMs and TTHMs and the other factors influencing THMs varied. The lifetime cancer risk estimation showed that, while risks from oral ingestion and dermal exposure to THMs are mostly less than 10 − 6 , which is the negligible risk level defined by the US EPA, however swimmers can be at the greater risk from inhalation exposure (7.77 × 10 − 4 –1.36 × 10 − 3 ).

Reduction of trihalomethane formation and detoxification of microcystins in tap water by ozonation

The efficiency of ozonation in comparison to chlorination for removal of microcystins and production of trihalomethanes (THMs) in water was investigated. One hundred and ninety water samples of ozone and chlorine treated water were collected at a water treatment plant between August 2004 and March 2005. The level of THMs, total organic carbon and residual chlorine were determined. Protein phosphatase 2A inhibition assay was used to detect microcystins and the presence of microcystins was confirmed by HPLC. The results show that 91.5% of the THM species in treated water was chloroform and 8.5% was bromodichloromethane. The mean THM level± standard error of mean in chlorinated water (CW) (45.1±3.0 μg/L) was higher than the mean of THM level in ozonated water (OW) (18.6±2.2 μg/L). In addition, no OW sample exceeded the first stage U.S. EPA maximum THM contaminant level for drinking water (80 μg/L) and only 8% of these samples exceeded the second stage level (40 μg/L). On the other hand, 3% of CW samples exceeded 80 μg/L and 68% exceeded the 40 μg/L level. The microcystin level in all water samples was below the WHO guideline value (1 μg/L) for drinking water.

Disinfection by-product formation and mitigation strategies in point-of-use chlorination of turbid and non-turbid waters in western Kenya

Over 1.1 billion people in the world lack access to improved drinking water. Diarrheal and other waterborne diseases cause an estimated 2.2 million deaths per year. The Safe Water System (SWS) is a proven household water treatment intervention that reduces diarrheal disease incidence in users in developing countries. Because the SWS recommends the addition of sodium hypochlorite to unfiltered water sources, concerns have been raised about the potential long-term health effects of disinfection by-products to SWS users. This study investigated the production of trihalomethanes (THMs) in water treated with sodium hypochlorite from six sources used for drinking water in western Kenya. The turbidity values of these sources ranged from 4.23 NTU to 305 NTU. THM concentrations were analysed at 1, 8, and 24 hours after addition of sodium hypochlorite. No sample exceeded the World Health Organization (WHO) guideline values for any of the four THMs: chloroform, bromodichloromethane, dibromochloromethane, or bromoform. In addition, no sample exceeded the WHO additive total THM guideline value. These results clearly show that point-of-use chlorination of a variety of realistic source waters used for drinking did not lead to THM concentrations that pose a significant health risk to SWS users.

Sources and Properties of Natural Organic Matter (NOM) in Water Along the Dongjiang River (the Source of Hong Kong’s Drinking Water) and Toxicological Assay of Its Chlorination By-Products

The Dongjiang River is the major source of the drinking water supply for Hong Kong and also other parts of the Pearl River Delta in China, and the deterioration in the water quality of this river and the excessive levels of trihalomethanes (THMs) in the tap water of some districts in Hong Kong have become a matter of public concern. The main objective of the present study is to investigate the distribution patterns of natural organic matter (NOM) and their association with THM production in the Dongjiang River. We examined the physicochemical and biological properties of the river water and the corresponding sediment elutriate collected from four sampling sites along the Dongjiang River from upstream to downstream and chlorination experiments were conducted. Algal bioassays were performed in order to test the chlorination effects. The results showed that: (1) upstream NOM was derived from terrestrial input, while that at mid- and downstream was most likely derived from phytoplankton; (2) phytoplankton is a major contributor to NOM in the sediments, whereas sediments seem to be the site for major microbial degradation of NOM, biogeochemical recycling of nutrients and a potential NOM pool for the overlaying water during sediment resuspension; (3) dissolved organic carbon (DOC) in surface water is a good indicator for THM production, whereas ultraviolet (UV) absorbance at 254 nm (UV(254)) is a better predictor for THM formation in the elutriates; (4) the bioassay results showed that toxic compounds other than THMs in the chlorinated water are the major factors causing algal growth inhibition.

Limitations of chlorine dioxide as an alternative disinfectant in comparison with chlorine from the viewpoint of mutagenicity

The change in the mutagenicity of water treated with chlorine dioxide was compared with that of chlorinated water to estimate the mutagenicity of drinking water in distribution systems. We carried out chromosomal aberration tests using Chinese hamster lung (CHL) cells to evaluate the mutagenicity. First, the levels of chloroform and TOX produced by chlorine dioxidation were approximately 1% and 5–7%, respectively, of those produced by chlorination. However, in water treated with chlorine dioxide, the activity that induced chromosomal aberrations was stronger than would be expected based on the quantity of by-products. The observed decreasing rate constant of the activity inducing chromosomal aberrations in chlorinated water was 1.4 to 1.9 times greater than that of water treated with chlorine dioxide, indicating that the mutagenicity of water treated with chlorine dioxide is more stable than that of chlorinated water. The mutagenicity of drinking water treated with chlorine dioxide was estimated to be 70–80% of that of chlorinated drinking water. However, these differences in mutagenicity are reduced when drinking water remains in distribution systems for long periods. The use of chlorine dioxide instead of chlorine can drastically reduce the production of trihalomethanes (THMs). However, the results of this study demonstrate that chlorine dioxide does not have much advantage in terms of the mutagenicity of drinking water. There were no disinfection by-products that demonstrated similar tendencies of change compared to the changes in the activity that induced chromosomal aberrations.

Solutions to fouling in power station condensers

The chlorine use was banned in the Italian Lagoon of Venice, as a consequence, alternative antifouling treatments had to be tested, optimised and, finally, adopted. Now, chlorine dioxide is in use in many plants instead of sodium hypochlorite. Peracetic acid (as antislime) and ammonium quaternary salts (as molluschicide) are also employed in some cases. The treatments are often combined with in-service mechanical cleaning, reducing significantly their cost. The dosage of the alternative oxidant products, now in use, has been optimised by the electrochemical monitoring system BIOX. As requested by Italian regulation, toxicity tests were performed and passed successfully before the adoption of each new treatment. Furthermore, new type of treatments, based on electrochemical low production of oxidant, were also preliminary tested, without significant production of trihalomethanes. The present paper illustrates some detail about the new treatments.

Formation of Trihalomethanes by the Disinfection of Drinking Water

Disinfection of natural water resources by chlorination to produce potable water results in the production of trihalomethanes. A number of environmental authorities have suggested that these trihalomethanes might have toxic and carcinogenic properties and have an effect on human health. Various monitoring studies have demonstrated appreciable concentrations of trihalomethanes in the effluents of water treatment plants, water distribution systems and domestic tap water. Hence, the majority of households that use tap water as a primary drinking source might be subject to any adverse effects. The possibility of health effects from the unwanted trihalomethanes is minimised by regulating their concentration in water. In order to maintain the standards established by the regulations, various approaches have been developed for controlling the level of these compounds. The object of this paper is to present an overview of chlorine disinfection of water and the formation, health effects and control of trihalomethanes as by products.

Potential Effects of Organic Carbon Production on Ecosystems and Drinking Water Quality

Restoration of tidal wetlands in the Sacramento-San Joaquin Delta (Delta) is an important component of the Ecosystem Restoration Program of the CALFED Bay-Delta Program (CALFED). CALFED is a collaborative effort among state and federal agencies to restore the ecological health and improve water management of the Delta and San Francisco Bay (Bay). Tidal wetland restoration is intended to provide valuable habitat for organisms and to improve ecosystem productivity through export of various forms of organic carbon, including both algae and plant detritus. However, the Delta also provides all or part of the drinking water for over 22 million Californians. In this context, increasing sources of organic carbon may be a problem because of the potential increase in the production of trihalomethanes and other disinfection by-products created during the process of water disinfection. This paper reviews the existing information about the roles of organic carbon in ecosystem function and drinking water quality in the Bay-Delta system, evaluates the potential for interaction, and considers major uncertainties and potential actions to reduce uncertainty. In the last 10 years, substantial progress has been made on the role of various forms of organic carbon in both ecosystem function and drinking water quality; however, interactions between the two have not been directly addressed. Several ongoing studies are beginning to address these interactions, and the results from these studies should reduce uncertainty and provide focus for further research.

Trihalomethane formation in drinking water and production within a polyvinyl chloride pipe environment

This project used pipe-incubated water samples collected from a pilot plant in North Vancouver, B.C., and the material-specific simulated distribution system (MS-SDS) test (Brereton 1998) to investigate the interaction between chlorine residuals in drinking water and the interior surface of polyvinyl chloride (PVC) distribution system pipes. Seasonal differences and residence time were important factors in trihalomethane (THM) production, and surface biofilm had a more significant impact on chloroform formation in bulk water than the treatment process. Biofilm adsorption has been identified as one surface mechanism responsible for the removal of THM precursors from the bulk water phase. This study observed that compounds previously adsorbed and extracellular materials from biofilm bacteria (including protoplasm from lysed cells) could participate in the aqueous chloroform formation in the absence of available precursor. Under chlorination conditions typical to the Greater Vancouver Regional District (GVRD) utilities, additional precursors were masked by the chlorine-limited condition; however, experiments confirmed that the practice of rechlorination would increase THM production beyond its bulk water capacity. Heterotrophic plate counts (HPCs), measured from biofilm scrapings, revealed that higher chloroform production was accompanied by bacterial regrowth. A proposed model summarizes the major mechanisms interacting in a PVC pipe environment. Key words: biofilm, chloroform, distribution system, drinking water, material specific simulated distribution system (MS-SDS), PVC pipe, regrowth, trihalomethane (THM) formation.

Power plant condenser performance forecasting using a non-fully connected artificial neural network

The chlorine use was banned in the Italian Lagoon of Venice, as a consequence, alternative antifouling treatments had to be tested, optimised and, finally, adopted. Now, chlorine dioxide is in use in many plants instead of sodium hypochlorite. Peracetic acid (as antislime) and ammonium quaternary salts (as molluschicide) are also employed in some cases. The treatments are often combined with in-service mechanical cleaning, reducing significantly their cost. The dosage of the alternative oxidant products, now in use, has been optimised by the electrochemical monitoring system BIOX.As requested by Italian regulation, toxicity tests were performed and passed successfully before the adoption of each new treatment.Furthermore, new type of treatments, based on electrochemical low production of oxidant, were also preliminary tested, without significant production of trihalomethanes. The present paper illustrates some detail about the new treatments.

Effect Of Irradiation And Free Radicals On Formation Of Trihalomethanes In Chlorinated Water

In order to understand the formation of trihalomethanes (THMs) in chlorinated water and to control the production of THMs more effectively, effects of irradiation and free radical on the formation of THMs were observed. It was found that humic acid (HA) solution contains a semi-quinone free radical, which variation trendency was relative to the production quantity of THMs directly. Irradiating the solutions containing THMs precursor before chlorination could promote the formation of THMs, which reached the highest point at 30 minutes, after then decreased with longer irradiation time in this experimental condition. Irradiating the chlorinated solution, the yield of THMs decreased slowly because of the destruction of chlorine. The production quantity of THMs was inversely proportional to the wavelength of light sources.

THM, haloacetic acids and other organic DBPs formation in disinfection of bromide rich Sea of Galilee (Lake Kinneret) water

Lake Kinneret (Sea of Galilee) is the main freshwater body in Israel and is the water source for the National Water Carrier (NWC). The lake water has a uniquely high bromide content 1.9 mg/L which affects DBPs (disinfection by-products) formation. Controlled experiments using different disinfectants were carried out with the lake water in order to study DBPs formation. Formation and distribution of TOX (total organic halogen) trihalomethanes (THM), haloacetic acids (HAA) and cyanogen halides were studied during the application of the following disinfectants: Chlorine, chloramine, chlorine dioxide and a combination of chlorine dioxide with chloramine. Brominated species dominated the distribution of THM, HAA and cyanogen halide. When a high dose of chlorine was applied an unusually high percent (75%) of the TOX formation potential was identified; THM constituted about 50% of the TOX formation potential and haloacetic acids 22-28%. Tribromoacetic acid was found to undergo decomposition to form bromoform. Chlorine dioxide produced insignificant concentrations of organic DBPs and chloramine produced low concentrations. Chlorine dioxide in combination with chloramine enhanced production of CNBr and THM, but their concentrations were much lower than during chlorination.

Adducts of the chloroform metabolite phosgene.

Chlorination of water for human consumption is important for disease prevention. However, halogenated by-products, such as trihalomethanes (THM), can be formed during this process (Bunn et al 1975). THM production raises public health concerns related to potential human cancer risk (Fawell, 2000). Chloroform (trichloromethane: TCM) is a byproduct that is frequently detected at relatively high concentrations (IARC, 1991), i.e. 0.1 to 300 μg/litre in finished drinking water (Uden and Miller, 1983) and up to 1 mg/litre in chlorinated swimming pool water (Lahl et al 1981).

Potential health effects of drinking water disinfection by-products using quantitative structure toxicity relationship

Disinfection by-products (DBPs) are produced as a result of disinfecting water using various treatment methods. Over the years, chlorine has remained the most popular disinfecting agent due to its ability to kill pathogens. However, in 1974, it was discovered that the superchlorination of drinking water resulted in the production of chloroform and other trihalomethanes. Since then hundreds of additional DBPs have been identified, including haloacetic acids and haloacetonitriles with very little or no toxicological data available, thus necessitating the use of additional methods for hazard estimation. Quantitative Structure Toxicity Relationship (QSTR) is one such method and utilizes a computer-based technology to predict the toxicity of a chemical solely from its molecular attributes. The current research was conducted utilizing the TOPKAT®/QSTR software package which is comprised of robust, cross-validated QSTR models for assessing mutagenicity, rodent carcinogenicity (female/male; rat/mouse), developmental toxicity, skin sensitization, lowest-observed-adverse-effect level (LOAEL), fathead minnow LC 50, rat oral LD 50 and Daphia magna EC 50. A total of 252 DBPs were analyzed for the likelihood that they would produce tumors and developmental effects using the carcinogenicity and developmental toxicity submodels of TOPKAT®. The model predictions were evaluated to identify generalizations between the functional groups (e.g. alcohols, acids, etc.) and specific toxic endpoints. Developmental toxicity was identified as an endpoint common to the majority of aliphatic mono- and dicarboxylic acids, aliphatic halogenated and non-halogenated ketones, and aliphatic haloacetonitriles. In the case of the carcinogenicity submodels, most aliphatic aldehydes were identified as carcinogens only in the female mouse submodel. The majority of the aliphatic and aromatic dicarboxylic acids were identified as carcinogens in the female rat submodel. All other functional groups examined were largely predicted as non-carcinogens in all the cancer submodels (i.e. male/female rats and mice). The QSTR results should aid in the prioritization for evaluation of toxic endpoints in the absence of in vivo bioassays.