Formation potentials of bromate and brominated disinfection by-products in bromide-containing water by ozonation

The ozonation involved in drinking water treatment raises issues of water quality security when the raw water contains bromide (Br-). Br- ions may be converted to bromate (BrO3-) during ozonation and some brominated disinfection by-products (Br-DBPs) in the following chlorination. In this study, the effects of ozone (O-3) dosage, contact time, pH, and Br- and ammonia (NH3-N) concentrations on the formation of BrO3- and Br-DBPs have been investigated. The results show that decreasing the initial Br- concentration is an effective means of controlling the formation of BrO3-. When the concentration of Br- was lower than 100 mu g/L, by keeping the ratio of O-3 dosage to dissolved organic carbon (DOC) concentration at less than 1, BrO3- production was effectively suppressed. The concentration of BrO3- steadily increased with increasing O-3 dosage at high Br- concentration (> 900 mu g/L). Additionally, a longer ozonation time increased the concentrations of BrO3- and total organic bromine (TOBr), while it had less impact on the formation potentials of brominated trihalomethanes (Br-THMFP) and haloacetic acids (Br-HAAFP). Higher pH value and the presence of ammonia may lead to an increase in the formation potential of BrO3- and Br-DBPs.