Multidrug-resistant and various high-risk ARGs in wastewater effluent exhibit nonnegligible AMR risks

Treated effluent from wastewater treatment plants (WWTPs) is a major source of emerging contaminants in natural aquatic systems. Enhancing the removal of antibiotics and antibiotic resistance genes (ARGs) in WWTPs is critical for mitigating antimicrobial resistance (AMR) risks to human health. This study characterized the occurrence of 16 representative antibiotics and 18 ARG categories in wastewater and sludge across the full treatment trains of two WWTPs. High-risk antibiotics and AMR hotspots were identified, and multiple ARG-carrying pathogenic hosts were detected in both matrices. Key antibiotics in wastewater, including macrolides (e.g., roxithromycin), fluoroquinolones (e.g., ofloxacin and pefloxacin), and sulfonamides (e.g., sulfamethoxazole) impose selection pressure on microbial communities and create potential hotspots for ARG dissemination. The treatment processes significantly reduced antibiotic concentrations and the potential AMR risk. However, after conventional UV₂₅₄ disinfection, the relative abundances of several ARG-harboring pathogens (e.g., Escherichia coli, Aeromonas caviae, and Pseudomonadales) increased, associated with elevated potential AMR risks in the final effluent. These findings provide important insights into AMR propagation within wastewater systems and highlight the necessity of developing alternative UV disinfection wavelengths, together with strengthened upstream control of antibiotics and ARGs prior to biological treatment. Further optimization could focus on enhancing antibiotic attenuation during biological treatment via bioaugmentation and exploring targeted advanced oxidation to reduce residual antibiotics and associated potential AMR risks.