AWWA ACE65609

An objective of the U.S. Environmental Protection Agency's (USEPA's) Stage 2 Disinfectants/Disinfection Byproducts Rule is to provide more equitable protection to the public through more consistent regulation of consecutive systems. A consecutive system is a public water system that receives some or all of its finished water from one or more other water systems. This study evaluates current disinfection byproducts (DPB) levels within 49 consecutive systems in Pennsylvania and their 30 respective wholesalers. For the 3? years of study data, Trihalomethane (THM) levels for the wholesalers averaged 45 µg/L. The THM average for the consecutive systems was 56 µg/L (a 25% increase). For THM and haloacetic acids (HAA) maximum contaminant level (MCL) compliance calculations, the Stage 2 Rule replaces the running annual average (RAA) method with a locational running annual average (LRAA) method. Nine of the 49 consecutive systems (18%) had recent THM LRAA values in excess of the Stage 2 THM MCL (80 µg/L). Two other consecutive systems had a THM LRAA just below the MCL. Because most consecutive systems are small systems (89%), serving less than 10,000 people, only single location is monitored; thus, the RAA and LRAA calculations are identical. Accordingly, the Stage 2 Rule change from an RAA to a LRAA calculation will have minimal affect on Pennsylvania consecutive systems state-wide. This study also indicates that THMs (vs. HAAs) pose a more substantial problem for consecutive systems in Pennsylvania. Includes 8 references, figures.