AWWA ACE68688

Most drinking water treatment plants that treat surface waters use enhanced coagulation or enhanced softening to remove precursors for trihalomethanes (THMs) and haloacetic acids (HAAs). In addition, many plants use ozone and chloramines to minimize the formation of the regulated organic disinfection byproducts (DBPs). Although there is no federal standard for N-Nitrosodimethylamine (NDMA), California has a notification level of 10 ng/L and a public health goal of 3 ng/L for NDMA. Moreover, NDMA is in the U.S. Environmental Protection Agency's (USEPA's) Unregulated Contaminant Monitoring Rule 2 and is on the Contaminant Candidate List 3. Thus, there is concern over the source of NDMA precursors in drinking water supplies, as well as treatment/disinfection practices to control NDMA formation. This paper addresses the source of NDMA precursors in the source waters treated by Metropolitan Water District of Southern California (MWDSC) and how various treatment processes at MWDSC's plants impact NDMA precursors. Includes 12 references, tables, figures.