Integrated assessment of biological activated carbon filters with UV/peracetic acid pretreatment for the mitigation of organic micropollutants and toxicity

The presence of organic micropollutants (OMPs) in wastewater poses a growing environmental risk, particularly for aquatic ecosystems and water reuse efforts. This study evaluates UV/peracetic acid (UV/PAA) oxidation combined with biofiltration as a sustainable solution for OMP degradation and toxicity mitigation. Over a six-month continuous bench scale study, secondary effluent was treated with UV/PAA or conventional UV/H₂O₂, followed by biological activated carbon (BAC) filtration. Treatment performance was assessed using targeted chemical analysis of common OMPs alongside effect-based bioassays (estrogenicity, cytotoxicity, phytotoxicity, and oxidative stress). Results demonstrated that UV/PAA pretreatment outperformed UV/H₂O₂ in degrading recalcitrant OMPs, achieving notable removal efficiencies for carbamazepine (65 %) and diuron (52 %). Additionally, UV/PAA significantly reduced photosynthesis inhibition (53 %) compared to UV/H₂O₂ (21 %). While the combined UV/PAA-biofiltration process did not further lower photosynthesis inhibition, it achieved a 63 % reduction in algal toxicity and over 60 % reduction in estrogenic load, effectively lowering the estrogenicity risk. Overall, biofiltration played a key role in mitigating most toxicity endpoints. Microbial community analysis revealed that biofilters supported the growth of OMP-degrading bacteria, including Pseudomonas, Mycobacterium, and Rhodococcus. UV/PAA pretreatment enhanced the abundance of Acinetobacter and Anaerolinea, species known for degrading estrogens and other OMPs. Cost analysis indicated higher operational costs for UV/PAA ($5.88 USD/m³) than UV/H₂O₂ ($2.36 USD/m³), but UV/PAA demonstrated better cost-effectiveness per unit of OMP removal. The study underscores UV/PAA-biofiltration as a promising but cost-sensitive alternative to conventional UVAOPs, with key benefits in toxicity mitigation and retrofit potential.