LAUSR

Abstract In this research, the formation of bromate and brominated oxidation byproducts (Br-OBPs) by the UVA/TiO2/peroxydisulfate (PDS) process in the presence of bromide was investigated. Bromate formation, undetectable in the UVA/TiO2 and UVA/PDS systems, was found to be significant in the UVA/TiO2/PDS system. The PDS concentration and TiO2 dosage were positively correlated with bromate formation, while the conversion of bromide to bromate was inhibited by the initial concentration of bromide itself. A lag phase was observed when the initial concentration of bromide was 7.0 mg/L. Extreme pH (4 or 10), humic acid, or ammonium completely inhibited the formation of bromate. Chloride, sulfate, and bicarbonate could suppress the bromate formation. Three Br-OBPs were detected in the UVA/TiO2/PDS system spiked with bromide when humic acid was used as the precursor, with a total concentration lower than 4 μg/L. The fluorescence change of humic acid in bromide solution during oxidation by the UVA/TiO2/PDS process could be dissected into three dissimilar components via parallel factor analysis (PARAFAC) of excitation-emission matrix (EEM) spectra. The results of this study demonstrate that bromate and Br-OBPs formation by the UVA/TiO2/PDS process could be well controlled in the presence of humic acid or ammonium.