Spectroscopic analysis on effluent organic matter (EfOM) evolution in different UV-based advanced oxidation processes

Abstract

The effluent organic matter (EfOM) removal performance of the advanced wastewater treatment process has drawn great attention owing to the potential ecological risk of EfOM in the receiving aquatic environments. However, the EfOM evolution process is still unclear in the various advanced wastewater treatment processes. In this study, the EfOM evolution process in terms of components, structures, and functional groups was investigated in four kinds of UV-based advanced oxidation processes (AOPs). The overall EfOM removal performances were in the order: UV/NaClO > UV/PMS > UV/H2O2 > UV. According to the spectroscopic analysis results, simple aliphatics/aromatic/acetylenes compounds with C–O, =C–H, amides, or amino structures deriving from protein-like substances, are easily destroyed under UV irradiation. Apart from these structures, microbial metabolic was strongly sensitive to a reactive chlorine species (RCS)-dominated system, especially nutrients, amino acids, and small peptides with ester. Total of 22 species of halogen by-products with high biotoxicity (acetonitrile-based chlorinated EfOM, chlorinated acetate, chlorinated methane) were detected in the UV/NaClO group. In contrast, the reactive oxygen species (ROS)-dominated systems exhibited strong structure selectivity for ester (UV/H2O2) and carbonyl (UV/PMS) in all of the EfOM components, exhibiting strong reaction activity with EfOM at different stages. The results reveal the EfOM evolution in different UV-based AOPs, providing a strategy for selecting suitable UV-based AOPs in the advanced wastewater treatment process in terms of high-efficiency removal of EfOM.