Improving advanced oxidation process efficiency in secondary swine wastewater effluent treatment by concentrating...

The combination of nanofiltration with advanced oxidation processes (AOPs) presents a synergistic strategy for cost-efficient wastewater treatment, yet the mechanistic effect of dissolved organic matter (DOM) enrichment in nanofiltration concentrate on AOP efficacy remains unclear. In this study, we utilized high-resolution mass spectrometry for molecular-level characterization to systematically explore how nanofiltration membrane concentration (NMC) affects the degradation of DOM from secondary swine wastewater effluent during UV/Fenton treatment. Our findings revealed that nanofiltration membranes selectively concentrated DOM molecules with a low oxidation degree (0.1 < O/C < 0.5), which were highly susceptible to oxidative degradation and positively correlated with acute toxicity. As a result, for concentrates with volumetric reduction factors (VRF) of 4 and 8, UV/Fenton treatment achieved DOC removal efficiencies 6.4 % and 8.4 % higher than that of secondary effluent, respectively, accompanied by a obviously reduction in acute toxicity. Additionally, the UV/Fenton process improved the biodegradability of concentrates by converting the unsaturated DOM into the biolabile aliphatic compounds (H/C > 1.5) via potential reactions, such as hydration and hydroxylation, thereby increasing DOC removal during aerobic biodegradation. The study delivers mechanistic evidence supporting NMC-enhanced AOPs performance and post-oxidation biodegradability improvement, providing a molecular framework for optimizing the hybrid treatment process.