AWWA WQTC59020

Formation of hydroxyl radicals (HO^.) and bromate during ozonation is strongly influenced by water quality and treatment variables. Quantification of HO^. was determined by introducing the R_CT value, expressed as a ratio of HO^. exposure (or concentration) to ozone exposure (or concentration). Two phases of R_CT were performed and the values of R_CT remain unchanged at any specific time throughout the ozonation process with a set of water quality. Linear relationships were observed between extents of water quality parameters and HO^. concentration or rate of bromate formation. Bromate formation can be controlled by adding acid or ammonia to depress intermediate OBr^-. Acid addition to lower water pH from ambient (8.2) to 7.5 and 6.5 reduced bromate formation by 30% and 80%, respectively. In comparison, adding ammonia reduced bromate formation up to 60% and 85% at pH 7.5 and 8.5, respectively. Ammonia's efficiency to mitigate bromate formation was lessened with lowered water pH. Includes 7 references, tables, figures.