Formation of Brominated Organic Compounds in Chlorinated Drinking Water

Bromide in water can be rapidly oxidised to bromine by chlorine. Both halogens are then able to compete to react with natural organic matter (NOM) to form disinfection byproducts (DBPs) containing only chlorine or bromine, or a mixture of the two halogens. Brominated DBPs are not the dominant by-products formed in most waters, but understanding how their formation can be minimised is important, because some are more toxic than their fully-chlorinated counterparts. The key factors that influence the concentrations of brominated DBPs are the concentrations of bromide ion, chlorine, NOM and ammonia, the characteristics of the NOM, pH, reaction time and temperature. The [Br−]:[chlorine] and [Br−]:[NOM] ratios are important in controlling the degree of bromine incorporation into NOM, and therefore the relative abundances of the various brominated DBPs; an increase in both ratios favours increased bromine incorporation. Mechanistic and empirical models have been developed either to provide greater insight into the mechanisms of brominated-DBP formation, or allow prediction of their concentrations.