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OCCURRENCE OF A NEW GENERATION OF DISINFECTION BY-PRODUCTS
Citation:
KRASNER, S. W., H. S. WEINBERG, S. D. RICHARDSON, S. J. PASTOR, R. CHINN, M. J. SCLIMENTI, G. D. ONSTAD, AND A. D. THRUSTON,JR. OCCURRENCE OF A NEW GENERATION OF DISINFECTION BY-PRODUCTS. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 40(23):7175-7185, (2006).
Impact/Purpose:
(1) Use a toxicity-based approach to prioritize and identify DBPs that show the greatest toxic response. (2) Comprehensively identify DBPs formed by different disinfectant regimes for the 'Four Lab Study'. (3) Determine the mechanisms of formation for potentially hazardous bromonitromethane DBPs.
Description:
A survey of disinfection by-product (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. 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 pre-chlorination. 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, approximately 30 and 39 percent of the TOX and total organic bromine, respectively, were accounted for (on a median basis) by the 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.