Integrated disinfection by-products mixtures research: comprehensive characterization of water concentrates prepared from chlorinated and ozonated/postchlorinated drinking water.

This article describes the disinfection by-product (DBP) characterization portion of a series of experiments designed for comprehensive chemical and toxicological evaluation of two drinking-water concentrates containing highly complex mixtures of DBPs. This project, called the Four Lab Study, involved the participation of scientists from four laboratories and centers of the U.S. Environmental Protection Agency (EPA) Office of Research and Development, along with collaborators from the water industry and academia, and addressed toxicologic effects of complex DBP mixtures, with an emphasis on reproductive and developmental effects that are associated with DBP exposures in epidemiologic studies. Complex mixtures of DBPs from two different disinfection schemes (chlorination and ozonation/postchlorination) were concentrated successfully, while maintaining a water matrix suitable for animal studies. An array of chlorinated/brominated/iodinated DBPs was created. The DBPs were relatively stable over the course of the animal experiments, and a significant portion of the halogenated DBPs formed in the drinking water was accounted for through a comprehensive qualitative and quantitative identification approach. DBPs quantified included priority DBPs that are not regulated but have been predicted to produce adverse health effects, as well as those currently regulated in the United States and those targeted during implementation of the Information Collection Rule. New by-products were also reported for the first time. These included previously undetected and unreported bromo- and chloroacids, iodinated compounds, bromo- and iodophenols, and bromoalkyltins.

Occurrence of a new generation of disinfection byproducts.

A survey of disinfection byproduct (DBP) occurrence in the United States was conducted at 12 drinking water treatment plants. In addition to currently regulated DBPs, more than 50 DBPs that rated a high priority for potential toxicity were studied. These priority DBPs included iodinated trihalomethanes (THMs), other halomethanes, a nonregulated haloacid, haloacetonitriles, haloketones, halonitromethanes, haloaldehydes, halogenated furanones, haloamides, and nonhalogenated carbonyls. The purpose of this study was to obtain quantitative occurrence information for new DBPs (beyond those currently regulated and/or studied) for prioritizing future health effects studies. An effort was made to select plants treating water that was high in total organic carbon and/or bromide to enable the detection of priority DBPs that contained bromine and/or iodine. THMs and haloacetic acids (HAAs) represented the two major classes of halogenated DBPs formed on a weight basis. Haloacetaldehydes represented the third major class formed in many of the waters. In addition to obtaining quantitative occurrence data, important new information was discovered or confirmed at full-scale plants on the formation and control of DBPs with alternative disinfectants to chlorine. Although the use of alternative disinfectants (ozone, chlorine dioxide, and chloramines) minimized the formation of the four regulated THMs, trihalogenated HAAs, and total organic halogen (TOX), several priority DBPs were formed at higher levels with the alternative disinfectants as compared with chlorine. For example, the highest levels of iodinated THMs-which are not part of the four regulated THMs-were found at a plant that used chloramination with no prechlorination. The highest concentration of dichloroacetaldehyde was at a plant that used chloramines and ozone; however, this disinfection scheme reduced the formation of trichloroacetaldehyde. Preozonation was found to increase the formation of trihalonitromethanes. In addition to the chlorinated furanones that have been measured previously, brominated furanones-which have seldom been analyzed-were detected, especially in high-bromide waters. The presence of bromide resulted in a shift to the formation of other bromine-containing DBPs not normally measured (e.g., brominated ketones, acetaldehydes, nitromethanes, acetamides). Collectively, -30 and 39% of the TOX and total organic bromine, respectively, were accounted for (on a median basis) bythe sum of the measured halogenated DBPs. In addition, 28 new, previously unidentified DBPs were detected. These included brominated and iodinated haloacids, a brominated ketone, and chlorinated and iodinated aldehydes.

Chemical and biological characterization of newly discovered iodoacid drinking water disinfection byproducts.

Iodoacid drinking water disinfection byproducts (DBPs) were recently uncovered in drinking water samples from source water with a high bromide/iodide concentration that was disinfected with chloramines. The purpose of this paper is to report the analytical chemical identification of iodoacetic acid (IA) and other iodoacids in drinking water samples, to address the cytotoxicity and genotoxicity of IA in Salmonella typhimurium and mammalian cells, and to report a structure-function analysis of IA with its chlorinated and brominated monohalogenated analogues. The iodoacid DBPs were identified as iodoacetic acid, bromoiodoacetic acid, (Z)- and (E)-3-bromo-3-iodopropenoic acid, and (E)-2-iodo-3-methylbutenedioic acid. IA represents a new class (iodoacid DBPs) of highly toxic drinking water contaminants. The cytotoxicity of IA in S. typhimurium was 2.9x and 53.5x higher than bromoacetic acid (BA) and chloroacetic acid (CA), respectively. A similar trend was found with cytotoxicity in Chinese hamster ovary (CHO) cells; IA was 3.2x and 287.5x more potent than BA and CA, respectively. This rank order was also expressed in its genotoxicity with IA being 2.6x and 523.3x more mutagenic in S. typhimurium strain TA100 than BA and CA, respectively. IA was 2.0x more genotoxic than BA and 47.2x more genotoxic than CA in CHO cells. The rank order of the toxicity of these monohalogenated acetic acids is correlated with the electrophilic reactivity of the DBPs. IA is the most toxic and genotoxic DBP in mammalian cells reported in the literature. These data suggest that chloraminated drinking waters that have high bromide and iodide source waters may contain these iodoacids and most likely other iodo-DBPs. Ultimately, it will be important to know the levels at which these iodoacids occur in drinking water in order to assess the potential for adverse environmental and human health risks.

A new approach to evaluating the toxicity and genotoxicity of disinfected drinking water.

The aim of this study was to evaluate the formation of toxic and genotoxic compounds in surface drinking waters treated with two widely used disinfectants, sodium hypochlorite (NaClO) and chlorine dioxide (ClO(2)), and a new disinfectant, peracetic acid (PAA). For this purpose a pilot plant was set up to add these biocides continuously to pre-filtered lake water flowing into three different basins. During three seasonal experiments, short-term in vivo tests (with plant, fish and molluscs) and in vitro tests (with bacteria, yeast and human cells) were carried out to evaluate the formation of genotoxic disinfection by-products (DBPs). Gas chromatography/mass spectrometry (GC/MS) was used to identify DBPs produced during the different treatments, microbiological analyses were performed to test the biocidal activity of the disinfectants, and chemical analyses were carried out to evaluate the quality of the water. The pilot drinking water plant under study was useful in studying the toxicity and genotoxicity of disinfected drinking water with this combined chemical/biotoxicological approach. This paper describes the setting up of the pilot plant and sets out/reports the results of the microbiological and chemical analyses.

Tribromopyrrole, brominated acids, and other disinfection byproducts produced by disinfection of drinking water rich in bromide.

Using gas chromatography/mass spectrometry (GC/MS), we investigated the formation of disinfection byproducts (DBPs) from high bromide waters (2 mg/L) treated with chlorine or chlorine dioxide used in combination with chlorine and chloramines. This study represents the first comprehensive investigation of DBPs formed by chlorine dioxide under high bromide conditions. Drinking water from full-scale treatment plants in Israel was studied, along with source water (Sea of Galilee) treated under carefully controlled laboratory conditions. Select DBPs (trihalomethanes, haloacetic acids, aldehydes, chlorite, chlorate, and bromate) were quantified. Many of the DBPs identified have not been previously reported, and several of the identifications were confirmed through the analysis of authentic standards. Elevated bromide levels in the source water caused a significant shift in speciation to bromine-containing DBPs; bromoform and dibromoacetic acid were the dominant DBPs observed, with very few chlorine-containing compounds found. Iodo-trihalomethanes were also identified, as well as a number of new brominated carboxylic acids and 2,3,5-tribromopyrrole, which represents the first time a halogenated pyrrole has been reported as a DBP. Most of the bromine-containing DBPs were formed during pre-chlorination at the initial reservoir, and were not formed by chlorine dioxide itself. An exception wasthe iodo-THMs, which appeared to be formed by a combination of chlorine dioxide with chloramines or chlorine (either added deliberately or as an impurity in the chlorine dioxide). A separate laboratory study was also conducted to quantitatively determine the contribution of fulvic acids and humic acids (from isolated natural organic matter in the Sea of Galilee) as precursor material to several of the DBPs identified. Results showed that fulvic acid plays a greater role in the formation of THMs, haloacetic acids, and aldehydes, but 2,3,5-tribromopyrrole was produced primarily from humic acid. Because this was the first time a halopyrrole has been identified as a DBP, 2,3,5-tribromopyrrole was tested for mammalian cell cytotoxicity and genotoxicity. In comparison to other DBPs, 2,3,5-tribromopyrrole was 8x, 4.5x, and 16x more cytotoxic than dibromoacetic acid, 3-chloro-4-(dichloromethyl)-5-hydroxy-2-[5H]-furanone [MX], and potassium bromate, respectively. 2,3,5-Tribromopyrrole also induced acute genomic damage, with a genotoxic potency (299 microM) similar to that of MX.

Mutagenicity and disinfection by-products in surface drinking water disinfected with peracetic acid.

The aims of this research were to study the influence of peracetic acid (PAA) on the formation of mutagens in surface waters used for human consumption and to assess its potential application for the disinfection of drinking water. The results obtained using PAA were compared to those found with sodium hypochlorite (NaClO) and chlorine dioxide (ClO2). The Ames test, root anaphase aberration assay, and root/micronuclei assay in Allium cepa and Tradescantia/micronuclei test were used to evaluate the mutagenicity of disinfected samples. Microbiological tests were also performed, and disinfection by-products (DBPs) were identified using gas chromatography/mass spectrometry (GC/MS). A slight bacterial mutagenicity was found in raw lake and river water, and similar activity was detected in disinfected samples. A plant test revealed genotoxicity in raw river water, and microbiological analysis showed that PAA has bactericidal activity but lower than that of the other disinfectants. The DBPs produced by PAA were mainly carboxylic acids, which are not recognized as mutagenic, whereas the waters treated with the other disinfectants showed the presence of mutagenic/carcinogenic halogenated DBPs. However, additional experiments should be performed with higher concentrations of PAA and using water with higher organic carbon content to better evaluate this disinfectant.