Bromide Influence on Trihalomethane and Haloacetic Acid Formation

Abstract An undesired consequence of adding chemicals such as chlorine to disinfect drinking water is the formation of disinfection byproducts (DBPs). Exposure to high doses of DBPs has been shown to cause cancers as well as adverse reproductive effects in laboratory animals. In contrast, epidemiological studies have not been able to conclusively establish a causal link between chlorinated drinking water containing DBPs to an increased cancer risk in humans consuming them. Regardless, federal regulations restricting the concentrations of several DBP classes (including four trihalomethanes and five haloacetic acids) have been established by the Environmental Protection Agency to reduce any potential risks they may pose. This section briefly describes the effects of changes in the relative concentrations of bromide ion and natural organic matter on the formation and speciation of trihalomethanes and haloacetic acids. Special emphasis is given to the formation of all nine haloacetic acids containing chlorine and bromine even though current and regulations anticipated in the near term do not address them. Additionally, it is shown that even though water treatment processes such as nanofiltration and granular activated carbon reduce the total concentrations of DBP precursors, they shift the relative speciation of THMs and HAAs toward the more brominated ones.