Chlorination for
drinking water can form brominated
trihalomethanes (THMs) in the presence of
bromide ions. Recent studies have reported that
bromodichloromethane (BDCM) has a stronger association with
stillbirths and
neural tube defects than other THMs species. In this paper, the results of an experimental investigation into the factors forming THMs in the presence of
bromide ions are presented. The experiments were conducted using synthetic water samples with different characteristics (e.g., pH, temperature, dissolve organic content). Different combinations of these characteristics were considered in the experimental program. The results showed that increased
bromide ion concentrations led to increases in the formation of total THMs, with higher BDCM and
dibromochloromethane (DBCM), and lower
chloroform formation. By increasing the pH from 6 to 8.5, increased
chloroform and decreased BDCM and DBCM formation were observed. Higher
bromide ions to
chlorine ratios increased BDCM and DBCM and decreased
chloroform formation, while higher temperatures increased BDCM, DBCM and
chloroform formation. In most cases,
bromoform (CHBr(3)) concentrations were found to be below the detection limit. Significant factors influencing BDCM formation were identified using a statistical analysis. A model for BDCM formation was estimated from 44 experiments and statistical adequacy was assessed using appropriate diagnostics, including residual plots and an R(2) of 0.97. The model was validated using external data from 17 water supply systems in Newfoundland, Canada. The predictive performance of the model was found to be excellent, and the resulting model could be used to predict BDCM formation in
drinking water and to perform risk-cost balance analyses for best management practices.