Evaluation of pretreatments for inhibiting bromate formation during ozonation

This study compared several pretreatment methods for inhibiting BrO3(-) formation during ozonation of tap water, from the DTU (Technical University of Denmark) campus, including H2O2 addition (peroxone), pH depression, and NH4+ and Cl2/NH4+ addition. At the same time, the inhibition of atrazine and carbamazepine removal was evaluated for each pretreatment. The required delivered O3 dose to achieve 90% removal of atrazine in the tap water from the DTU campus was 3.5 mg/L, which produced 130-170 microg/L BrO3(-). Peroxone did not reduce the required O3 dose for contaminant removal; however, it limited BrO3(-) formation to below the drinking water limit of 10 microg/L. Depression of solution pH to 6.0, reduced BrO3(-) formation to half, but it was still well above the water limit. Pretreatment with NH4+ also reduced BrO3(-) formation by approximately 50%, though it reduced atrazine degradation to 65%. Pretreatment with Cl2/NH4+ reduced BrO3(-) formation close to the 10 microg/L limit; however, atrazine removal did not exceed 75%. Carbamazepine was completely removed under all the tested experimental conditions with the 3.5 mg/L O3 dose.