AWWA JAW65234

Monitoring data from 113 large water systems in North Carolina were analyzed to assess compliance with the trihalomethane (THM) and haloacetic acid (HAA) regulatory requirements of the Stage 1 Disinfectants/Disinfection Byproducts Rule (D/DBPR) as well as potential future compliance with the Stage 2 D/DBPR. Of the 452 sets of data analyzed, only eight exceeded the Stage 1 maximum contaminant level (MCL) for total THMs, and eight exceeded the MCL for the five regulated HAAs, for an overall noncompliance rate below 2%. More than 99.4% of the population served by these North Carolina drinking water systems was exposed to water with DBP concentrations below the regulatory limits. The study provides a template for other states and primacy agencies to examine compliance for their jurisdictions and offers evidence that the Stage 1 MCLs are achievable on a wide-scale basis. However, examination of bromine incorporation patterns among the THM and HAA species suggests that monitoring for only HAA5 tends to underestimate overall HAA occurrence by 20-25%, a factor that may be a key issue in future DPB regulations. Includes 15 references, figures.