LAUSR

Formation of genotoxic byproducts during different ultraviolet (UV) -related water/wastewater treatment processes (including medium pressure (MP) UV oxidation, LP UV oxidation, chlorination, biological activated carbon (BAC) treatment, H2O2 oxidation, and two or more combined processes) was investigated by Ames fluctuation test using Salmonella strains TA98 and TA100 with and without rat liver enzyme extract S9. Byproducts responsible for genotoxicity were identified. The results showed that MP UV can induce mutagenicity and LP UV treatment does not induce mutagenicity. H2O2 oxidation could degrade part of genotoxic compounds. Compared with chlorination, BAC treatment is more effective in removing genotoxicity. Mutagenicity was found mostly in samples tested with TA100 instead of TA98, especially with TA100 without S9, indicating that guanosine and/or cytosine adducts contribute to mutation or toxicological effects in MP UV treated samples. Potential genotoxic byproducts were selected, most of which were nitrogenous organic compounds with more than 10 carbon atoms. Nitrosamines and histidine were excluded from potential genotoxic candidates. The results could contribute to evaluation of mutagenicity of various UV-based water treatment processes.