Oxidation Efficiency and Inorganic Oxyhalide By-product Formation during UV Photolysis of Chlorine and Bromine Species in Water

Abstract

Combined used of halogen-based oxidants such as chlorine/bromine and UV have been increasing for various water treatment applications for the purposes of enhancing elimination efficiency of contaminants and/or lowering residual oxidant levels. This study determined and compared the pH-dependent, 1) photodecomposition parameters of oxidants, 2) abatement efficiency of chemical probe compounds, and 3) halogenated oxyanion by-product formation during UV254nm photolysis of oxidants at pH 6 and 10. To better understand the underlying (photo)chemistry of chlorine and bromine species in water, the kinetic modeling approach was used. Overall, the new kinetic, stoichiometric, mechanistic and modeling information for the photochemistry of chlorine/bromine species in water obtained from this study can be useful for modeling and optimizing the combined applications of UV and halogen oxidants for various water treatments.