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DRINKING WATER DISINFECTION BY-PRODUCTS: WHAT IS KNOWN
Citation:
Richardson, S D. DRINKING WATER DISINFECTION BY-PRODUCTS: WHAT IS KNOWN. Presented at International Workshop on Exposure Assessment for Disinfection By-Products in Epidemiologic Studies, Ottawa, Canada, May 7-10, 2000.
Impact/Purpose:
(1) Use toxicity-based approach to 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:
Chlorine, ozone, chlorine dioxide, and chloramine are currently the major disinfectants being used to disinfect drinking water. Although the alternative disinfectants (ozone, chlorine dioxide, and chloramine) are increasing in popularity in the United States, chlorine is still used at most treatment plants, with an estimated 150 million people in the U.S. drinking chlorinated water. Following the discovery of chloroform as a chlorination disinfection by-product (DBP) in 1974, researchers began to identify disinfection by-products. Of the disinfectants, chlorination by- products have been the most studied, and, as a result, over 300 chlorine DBPs have been reported in the literature (Richardson, 1998). Fewer studies have been carried out for the alternative disinfectants; however, there is some information known about their by-products. It should be noted that, even for chlorine, not all by-products have been identified and reported. In studying chlorine as a secondary disinfectant, our research group has identified several new by-products of chlorine that have never been reported. It is likely that the lack of available spectroscopic tools limited earlier researchers in their efforts to identify these by-products. Another limitation is the inability to extract highly polar DBPs from water. Derivatization is one way to overcome this limitation. For example, derivatization with pentafluorobenzylhydroxylamine (PFBHA) has allowed a subset of ozonation DBPs--polar aldehydes and ketones--to be extracted and identified. However, it is believed that a large fraction of highly polar DBPs are still not identified. As analytical techniques are developed to address these polar by-products, and derivatization methods are discovered, it is likely that the more polar DBPs will be identified. As with any other chemicals, the knowledge of DBPs will be driven by the analytical techniques that are available. A summary of what is currently known about the DBPs from the major disinfectants and their combinations will be presented. Some were identified in actual drinking water samples, others from reaction of the disinfectant with isolated humic or fulvic acids.