Solar-Induced Phototransformation of Peracetic Acid in Chromophoric Dissolved Organic Matter Solutions

Peracetic acid (PAA) has been extensively investigated as an alternative disinfectant for water and wastewater treatments. However, the photochemical transformation of PAA in sunlit surface waters has not been previously investigated. For the first time, the photosensitized transformation of PAA was here observed in chromophoric dissolved organic matter (CDOM)-enriched solutions under simulated solar irradiation. Triplet CDOM (³CDOM^*) is here proposed to play a key role in the phototransformation processes. Using triplet model compounds, the reaction rate constant of ³CDOM^* with PAA can be estimated to around 1.1 × 10⁸ M^-1 s^-1. The reaction mechanism of triplet with PAA involves both energy- and electron-transfer. CH₃COO^• was generated from the reaction between PAA and excited triplets. Furthermore, HO^• and organic reactive species (i.e., CH₃COOO^• and CH₃COO^•) are involved in the photochemical transformation of PAA in sunlit CDOM-enriched solutions. These reactive species (including HO^•, CH₃COOO^•, and CH₃COO^•) also play a role in the removal of contaminants of emerging concerns (CECs). Overall, the current study provided new insights into the photochemical transformation of PAA in CDOM-enriched solutions. The solar irradiation of wastewater with PAA enhancement could be a useful and economically beneficial advanced oxidation process for CEC abatement.