AWWA WQTC60731

This work investigated the effect of bromide and iodide ions on the formation and speciation of disinfection byproducts (DBPs) from chlorination of natural waters. Two waters containing contrasting group precursors were chlorinated after being spiked with various levels of bromide or iodide ions (0-30µM/L). The molar yields of trihalomethanes (THMs) and haloacetic acids (HAAs) increased as the initial bromide ion concentration increased. The molar yield of THMs was comparatively stable for different initial iodide ion concentrations. No significant change of total organic halogen (TOX) concentration was found for varying bromide concentrations. However, TOX concentrations decreased substantially with increasing initial iodide ion concentrations. The increasing of initial bromide concentrations resulted in decreasing levels of unknown TOX (i.e. not attributed to THMs and HAAs) and unknown TOCl but increasing unknown TOBr. The distribution among tri-, di- and monohalogenated HAAs was dependent of the bromide ion concentrations. Increasing initial bromide concentration resulted in higher fraction of trihalogenated HAAs and lower fraction of dihalogenated HAAs. The general order of the bromine incorporation factor was: TTHM>THA&DHAN>DHA. The general order of the extent of bromine substitution was: DHAN> DHA&TTHM >THA. The extent of iodine substitution was much lower than that of bromine substitution when comparing identical initial concentrations since a substantial amount of iodide was oxidized to iodate. Increasing chlorine dose was able to control the formation of iodinated organic compounds by oxidizing the majority of iodide to iodate. Includes 29 references, table, figures.