Enhanced Removal of Micropollutants from Secondary Effluents Using UV/Sulfite and Biochar-Coupled Advanced Oxidation Processes

Emerging micropollutants (MPs) in environmental matrices have received growing attention due to their detrimental effects on aquatic ecosystems. As a result, there is an urgent need to develop efficient removal strategies. Ultraviolet-based advanced oxidation processes (UV-AOPs) have emerged as a promising approach for degrading MPs in secondary wastewater effluents (SWEs). This study investigated the occurrence and advanced treatment of 50 MPs—including 8 perfluorinated compounds (PFCs), 23 pharmaceuticals, 2 pesticides, 4 endocrine-disrupting chemicals, 7 nitrosamines, 2 corrosion inhibitors, and 4 preservatives—across five wastewater treatment plants (WWTPs) in Korea. Detected concentrations ranged from 4.7 to 7,851 ng/L, with metformin, cimetidine, caffeine, naproxen, atorvastatin, iopromide, estrone, and ibuprofen being the most prevalent. Most targeted PFCs and nitrosamines were detected at trace levels, typically between 1.4 and 28 ng/L. Under UV photolysis, the removal efficiency for most MPs was below 30% at UV fluence < 750 mJ/cm². However, the UV/sulfite process significantly enhanced the removal of UV-resistant MPs (e.g., metformin, DEET, carbamazepine), achieving removal efficiencies greater than 80%. In contrast, PFCs exhibited notable degradation only when treated with UV/sulfite-coupled biochar systems. This study presents a comprehensive dataset on the occurrence, removal efficiency, and potential risks of MPs in Korean WWTPs. Furthermore, it highlights the effectiveness of UV/sulfite-coupled biochar systems as a promising strategy to enhance quaternary treatment and improve overall wastewater management.