Disinfection is the primary microbial control in drinking water treatment to inactivate pathogens in the source water. Chlorine is the most commonly used disinfectant in the United States. Chlorine oxidizes biological agents and provides residual protection to inhibit microbial growth in water distribution systems. However, chlorine can react with naturally-occurring materials in water to form disinfection-by products (DBPs), including trihalomethanes (THMs) and haloacetic acids (HAAs). Some DBPs in drinking water have been linked to cancer and adverse reproductive effects in numerous epidemiological studies. In the Monongahela River basin in Southwestern Pennsylvania, elevated bromide concentrations in source water have been observed to cause increased THMs and HAAs formation in finished water, especially increased brominated-DBPs. Brominated-DBPs are more carcinogenic than chlorinated-DBPs. This study presents a statistical simulation model to evaluate the effect of the increasing source water bromide on THM formation and speciation, and analyzes the changing risks (using cancer slope factors) in treated water from 2010 to 2012. Source water bromide concentration was significantly correlated with cancer risks from dibromochloromethane and bromoform in finished water, and even very low bromide concentrations were associated with increased risk. HAA9 increased with increasing source water bromide as well, but the brominated HAA species in regulated HAA5 show clear linear decrease trend with increasing bromide, suggesting increasing source water bromide could lead to increases in harmful HAAs while still meeting regulatory compliance measured as HAA5.

Assessing the risk associated with increasing bromide in drinking water sources in the Monongahela River, Pennsylvania

252nd National Meeting (2016)

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