Pilot-scale simultaneous coupling ozonation and biodegradation for enhancing pollutant removal and mitigating...

Penicillin intermediate wastewater contains recalcitrant organics and residual antibiotics that favor the enrichment of antibiotic-resistant bacteria and the dissemination of antibiotic resistance genes (ARGs). In this study, a pilot-scale simultaneous coupling ozonation and biodegradation (SCOB) system was applied to treat the secondary biochemical effluent of penicillin intermediate wastewater. The reactor achieved stable operation under selected conditions of a 6 h hydraulic retention time, a 2 h ozone supply period, and an ozone dosage of 5 mg/(L·h). Compared with the standalone biodegradation system, the SCOB system enhanced chemical oxygen demand removal by 25.90%, UV₂₅₄ removal by 31.34%, and a 34.93-fold increase in chroma removal. The SCOB system attenuated both chronic and acute toxicity in the effluent. Microbial analyses revealed that, despite lower biomass, microbial activity increased by 21.04% in the SCOB system, accompanied by distinct community succession, with Proteobacteria, Actinobacteria, and Chloroflexi as the dominant phyla and Hyphomicrobium as the dominant genus. The SCOB system also reduced intracellular reactive oxygen species levels and suppressed ARGs abundance and dissemination. The total abundance of ARGs decreased by 10.34%, while multidrug resistance plasmids were reduced by 25.40%. This study provides engineering guidance for developing pilot-scale SCOB as an advanced treatment strategy for simultaneously achieving pollutant removal and ARGs risk mitigation in antibiotic-containing wastewater.