Occurrence and removal of antibiotics in wastewater treatment systems: Insights into treatment stages difference and seasonal variation

The wastewater treatment plants (WWTPs) are considered as the significant source of antibiotics to the receiving water, causing potential ecological risks. Nevertheless, the occurrence and removal efficiencies of antibiotics during wastewater treatment remain incompletely understood. In this study, we examined the occurrence and removal efficiencies of 16 antibiotics in 3 full-scale WWTPs with different treatment processes in both summer and winter. The level of detected antibiotics in influent was 1.87–480.09 ng/L, while less than 150 ng/L in effluent. Macrolides and quinolones were the predominant antibiotics in both influent (total macrolides: 296.99–654.25 ng/L, total quinolones: 462.90–1079.03 ng/L) and effluent (total macrolides: 103.67–523.78 ng/L, total quinolones: 134.26–264.43 ng/L). The removal efficiencies of antibiotics in full-scale wastewater treatment ranged from 45.60% to 79.17%, in which the biological treatment process exhibited the most efficient removal although sludge was still the occurrence hotspots for antibiotics. Furthermore, we demonstrated that some high-risk antibiotics retained ecological risks after treatment. Our findings highlighted the significant role of the biological treatment process in removing antibiotics, and offered valuable insights for optimizing the treatment process to enhance the removal efficiency of antibiotics to avoid the downstream potential ecological risk in receiving water.