Removal of disinfection byproducts and toxicity of chlorinated water by post-treatments of ultraviolet/hydrogen peroxide and ultraviolet /peroxymonosulfate

Abstract

Post-treatment of ultraviolet (UV) irradiation is not efficient in eliminating toxicity of chlorinated water. Removal of disinfection byproducts (DBPs) and toxicity of chlorinated water by UV/hydrogen peroxide (UV/H2O2) and UV/peroxymonosulfate (UV/PMS) was investigated. In the absence of bromide, adding H2O2 or PMS enhanced the removal of nitrogenous DBPs and total organic chlorine (TOCl) than UV alone (1200 mJ/cm2). UV/PMS decreased the cytotoxicity from 10.6 to 4.4 mg-Phenol/L and genotoxicity from 7.1 to 2.0 μg-4-NQO/L, more efficient than UV/H2O2. However, results were quite different in the presence of bromide. PMS led to the increased formation of total organic bromine (TOBr) in chlorinated water. UV/PMS was therefore less efficient in toxicity removal than UV/H2O2. In the presence of bromide, UV/H2O2 decreased the cytotoxicity and genotoxicity by 85% and 68%, while UV/PMS only removed the cytotoxicity and genotoxicity by 59% and 46%. In the UV/PMS process, SO4˙- was more efficient on toxicity removal than ˙OH. Contributions of UV irradiation, ˙OH and SO4˙- were 55%, 14% and 31% to cytotoxicity removal, and 49%, 15% and 36% to genotoxicity removal. This study demonstrated the feasibility of using UV/H2O2 and UV/PMS as post-treatments to enhance the removal of DBPs and toxicity of chlorinated water.