Application of Effect Directed Analysis to Identify Mutagenic Nitrogenous Disinfection Byproducts of Advanced Oxidation Drinking Water Treatment

摘要

Advanced oxidation processes are important barriers for organic micropollutants (e.g., Pharmaceuticals, pesticides) in (drinking) water treatment. Studies have indicated that medium pressure (MP) UV/H2O2 treatment leads to a positive response in Ames mutagenicity tests, which is then removed after granulated activated carbon (GAC) filtration. The potentially mutagenic substances formed have been scarcely identified. Earlier research showed that many substances result from the reaction of photolysis products of nitrate with (photolysis products of) natural organic material (NOM). Using an innovative approach to trace the formation of disinfection byproducts (DBPs) of MP UV water treatment, based on stable isotope labeled nitrate combined with high resolution mass spectrometry, we showed that multiple nitrogen containing substances were formed in artificial water during MP UV treatment. Part of these DBPs were also detected in full scale water samples. In these samples, both chemical analysis and the Ames fluctuation test showed an increased response after MP UV/H2O2 treatment. For 14 DBPs the structure of the N-DPB was elucidated using in silico fragmentation tools and confirmed with analytical reference standards. Further identification of the detected N-DBPs, using effect directed analysis to pinpoint the source of the mutagenicity or individual testing of these substances in Ames tests, would provide more insight into the relation of the N-DBPs with the observed mutagenicity. To this end, fractions of MP UV treated and untreated water extracts were prepared using preparative HPLC. These fractions were each concentrated and tested in the Ames fluctuation test. In addition, high resolution mass spectrometry was performed in all fractions to assess the presence of N-DBPs. After evaluating the results, a correlation was observed between the detection of byproducts in the fractions and the mutagenic response. Based on toxicity data and read across analysis, we could indicate five N-DBPs that are potentially genotoxic and were present in relatively high concentrations in the fractions in which mutagenicity was observed. The results of this study offer opportunities to further evaluate the identity, potential health concern and relevance for full scale drinking water treatment plants and varying process conditions of N-DBPs formed during MP UV drinking water treatment.