Evaluation of pre-treatments for inhibiting bromate formation during ozonation

This study compared several pre-treatment methods for inhibiting BrO3- formation during ozonation of tap water, from the DTU campus, including H2O2 addition (perozone), pH-depression, NH4+ and Cl2/NH4+ addition. At the same time, the inhibition of atrazine and carbamazepine removal was evaluated for each pre-treatment. 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 µg/L BrO3-. Perozone did not reduce the required O3 dose for contaminant removal, however it limited BrO3- formation below the drinking water limit of 10 μg/L. Depression of solution pH to 6.0, reduced BrO3- formation to half, but it was still well above the water limit. Pre-treatment with NH4+ also reduced BrO3- formation by approximately 50%, though it reduced atrazine degradation to 65%. Pre-treatment with Cl2/NH4+ reduced BrO3- formation close to the 10 μg/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.