NOM's role in bromine and bromate formation during ozonation

Natural organic matter (NOM) can influence the rate and extent of bromide oxidation during ozonation and affect disinfection by-product (DBP) formation. In batch ozonation experiments of model water samples under similar conditions, variable concentrations of bromate and organobromine formed in the presence of different NOM isolates. Differences in the source and composition of NOM, as measured by the ratio of specific ultraviolet absorbance at 254 nm to dissolved organic carbon, can account for variations in the rate of ozone and hydroxyl (HO) radical consumption by NOM. The presence of NOM significantly reduced the bromate formation relative to NOM-free water. The mechanism for the decrease in bromate formation has two components: (1) NOM reacts directly with ozone and HO radicals to reduce the amount of oxidant available for bromide and bromine oxidation, respectively, and (2) NOM reacts with bromine, the main intermediate in the formation of DBPs.