Influence of the UV/H2O2 Advanced Oxidation Process on Dissolved Organic Matter and the Connection between Elemental Composition and Disinfection Byproduct Formation.

The UV/H2O2 process is a promising advanced oxidation process (AOP) for micropollutant abatement in drinking water treatment and water reuse plants. However, during micropollutant degradation by the AOP, dissolved organic matter (DOM) and the disinfection byproduct (DBP) formation potential may also be altered. This study investigated the influence of the UV/H2O2 AOP on the elemental composition and DBP formation potential of two DOM isolates by using ultrahigh-resolution mass spectrometry (UHRMS). After the AOP, 629 new chemical formulas with an increased degree of oxidation and decreased aromaticity were obtained. Such alterations led to the formation of 226 unknown DBPs with decreased aromaticity indices (AImod) in the subsequent 3-day chlorination. Links between the unknown DBPs and the corresponding precursors in DOM were visualized by network computational analysis. The analysis gave three zones in the van Krevelen diagram based on the possibility of the C7-22HnOm formulas located in each zone to link to the corresponding DBPs. A further investigation with two model compounds reconfirmed the hydroxylation and ring cleavage of DOM by HO· attack during the AOP and the influence on DBP formation. These results obtained from UHRMS build the connection between the elemental composition of DOM and the formation potential of DBPs.