Investigation of the formation of chlorination by-products in water rich in bromide and organic matter content

Bench-scale chlorination experiments with river water rich in bromide and organic matter content were performed in order to investigate the behavior and speciation of the chlorination by-products, especially the brominated ones, which are considered more harmful to human health than their chlorinated analogues. The analysis of the compounds was performed by means of gas chromatography. Statistical treatment of the results with Multifactor Analysis of Variance technique revealed the trends of each compound as function of pH, chlorine dose, reaction time and temperature. Brominated species of chlorination by-products predominated, due to the presence of bromide in the river water leading to preferable bromination than chlorination of the organic matter. Bromide incorporation factors were calculated for trihalomethanes and haloacetic acids, the major categories of compounds formed. While bromide incorporation factors decreased with increasing chlorine dose, the opposite was true for low range of chlorine dose, a fact that needs to be considered during treatment of waters with similar properties. Bromide incorporation factors decreased with increasing pH, especially for haloacetic acids. While the organic matter content can be sufficiently removed during water treatment, bromide ion still remains in the treated water. The results of the present study indicate that chlorination conditions should be optimized in order to minimize the incorporation of bromide into the chlorination by-products formed, which would increase their toxic effects on the water consumers.