Comprehensive Characterization of the Transformation of Wastewater Effluent via Advanced Oxidation Processes Using Nontarget Mass Spectrometric Analysis

Advanced
oxidation processes (AOPs) have been extensively studied,
employing preselected target compounds to evaluate their performance;
however, this might overestimate their performance in real water.
Herein, we applied nontarget mass spectrometric analysis to characterize
the transformation of wastewater effluent during UV/H2O2 and UV/peroxydisulfate (PDS) processes. A total of 8,986
detected features, including 169 identified micropollutants, were
categorized as stable features, unstable features, and transformation
products (TPs) based on their transformation behaviors. Approximately
40% of the detected features were resistant to both AOPs, highlighting
their need for additional treatment. The UV/H2O2 process eliminated a wider range of organic compounds than the UV/PDS
process with the participation of H2O2-related
nonradical reactive species, while the UV/PDS process exhibited high
selectivity in degrading organic compounds at a faster rate. Oxygen
addition and dealkyl group reactions were the most common reaction
types in the AOPs. Linkage analysis with the four representative reactions
of toxic TPs implied the higher probability of the UV/PDS process
yielding high-toxicity products compared with the UV/H2O2 process. This study provides a comprehensive view of
the two AOPs and is helpful to improving understanding of their performance
in treating wastewater effluent.