David A. Reckhow
Controlling disinfection byproduct formation is one of the biggest challenges facing drinking water providers. This report examines two issues regarding disinfection byproducts in public water systems: 1) watershed sources of DBP precursors and watershed characteristics, such as precipitation, season, and land use, which influence DBP formation; and, 2) factors, such as treatment practices, season, and raw water quality, that affect DBP formation at water treatment plants and in distribution systems. In order to analyze these issues, this project utilized two databases, one consisting of DBP precursor data from Wachusett Reservoir located in Central Massachusetts, and the other consisting of historical water treatment data and DBP concentrations from several communities in Massachusetts. As such, this paper consists of an introductory chapter followed by two main chapters, each dedicated to analyzing one of the databases and each consisting of its own results and conclusions. With respect to watershed influences on DBP precursors, this study shows that: non-aromatic compounds may be significant sources of DBP precursors; DBP precursors and specific DBP-FP are highest during winter months; precipitation tends to favor THM formation rather than HAA formation; rainwater can be a significant source of DBP precursors; specific DBP-FP is significantly correlated with agricultural lands and wetlands (negative) and with urban areas (positive); DOC is significantly correlated with water areas (positive) and urban areas (negative); and, finally, riparian zones probably do not contribute the majority of DBP precursors. With respect to the occurrence of DBPs in public water systems, this study shows that: water sources high in TOC tend to universally filtered while low TOC sources tend to be treated without filtration or by direct filtration; alternative disinfectants are more effective when coupled with multiple precursor removal processes; free chlorine generally results in higher DBP concentrations regardless of precursor removal; ozone is very effective at minimizing DBPs but may result in other unwanted byproducts; high DBP concentrations are observed in systems with low TOC waters if precursor removal is minimal; THM concentrations are highest at water treatment plants during the fall while THM and HAA5 concentrations are highest in distribution systems during the summer; and, finally, DBP formation in distribution systems is considerable and a challenge to water systems. A fourth chapter of this report examines the usefulness of utilizing results from both databases and the final chapter presents recommendations for future work.