Concerning Toxic Byproducts and Full-Scale UV/Chlorine Advanced Oxidation Water Treatment

This work investigated byproduct formation and <i>in vitro</i> genotoxicity and cytotoxicity at four facilities using UV/chlorine advanced oxidation for potable reuse or drinking water treatment. In arguably the most common application of UV/chlorine, treating reverse osmosis permeate for potable reuse, organic byproduct formation was always either not detected or well-below typical drinking water levels. At a groundwater-source drinking water treatment plant, the trihalomethanes and haloacetic acids each increased by up to 12 μg/L through the UV reactor and 40 μg/L during secondary disinfection, but the final concentrations remained low relative to regulatory limits. Overall, and aside from the known pathways of chlorate formation, the UV/chlorine byproduct and <i>in vitro</i> toxicity formation observed in this study was lower than what is generally found in many chlor(am)inated drinking waters, although there was some observed shift to more brominated species, which might be deserving of future research, given their higher <i>in vitro</i> toxicity compared to typical chlorinated species.