Development of predictive models for the formation of trihalomethanes and haloacetic acids during chlorination of bromide-rich water

Abstract

The formation of disinfection by-products (DBPs) during chlorination of drinking water is an issue which has drawn significant scientific attention over the last few years, due to the adverse effects of these compounds on human health. The complicated mechanisms of the formation of DBPs are still under investigation, and modelling attempts are being made. One of the major factors affecting the yields of DBPs is the concentration of bromide ion. In bromide-rich waters, the brominated species-bromoform, dibromoacetic acid-which are considered more toxic than their chlorinated analogues, may be the major species formed and therefore the consumption of these waters may be more harmful to human health than the consumption of water containing chlorinated species (chloroform, dichloroacetic acid). During this study, the effect of bromide ion on DBP formation was investigated by bench-scale chlorination experiments and statistically evaluated for individual species of DBPs. The importance of interactions between pairs of chlorination factors, pH, bromide concentration, chlorine dose and time for DBP formation was highlighted by statistical analysis results. Moreover, multiple regression models were developed for the concentrations of total trihalomethanes and total haloacetic acids, the two major DBP groups formed. The models developed provide satisfactory estimations of, but also indicate different formation mechanisms for, these two groups of DBPs. © 2004, CAWQ.