EFFECT OF BROMIDE ION ON HALOACETONITRILE FORMATION BY DISINFECTION WITH CHLORINE

Haloacetonitriles (HANs) are formed during the chlorination of drinking water containing humic substances and other precursor compounds. Although the Trihalomethanes (THMs) and Haloacetic Acids (HAAs) are considered the major portion of chlorination by-products, HANʹs are also formed in lower concentrations and might have a higher adverse health effect compared to the other two groups. Bromide influences the formation of these by-products. To define the influence bromide-ion concentration has on the formation of haloacetonitriles (HANs) in drinking water treated with chlorine, a full factorial matrix was designed to statistically evaluate the influence of various parameters that are relevant to drinking water treatment. The effect of other independent variables, including pH and reaction time, was also investigated. The factorial design incorporated each of the three factors, Br, time and pH at three levels. Also included in the design was a sample set without bromide. The study determined the range of concentrations of Dichloroacetonitrile (DCAN), Bromochloroacetonitrile (BCAN) and Dibromochloreacetonitrile (DBCAN) at varying experimental conditions. Similar to THMs and HAAs, bromide ion in chlorinated humic acid solution was shown to shift the distribution of HANs to more brominated and mixed halogenated species.