Fate characteristics, exposure risk, and control strategy of typical antibiotics in Chinese sewerage system: A review

In China, the sewerage system plays an essential role in antibiotic removal; however, the fate profiles of antibiotics in sewers are not well understood, and risk identification throughout the sewerage system is inadequate. Based on the extensive detection results for typical groups of antibiotics in the discharge sources, influent and effluent from wastewater treatment plants (WWTPs), and excess sludge, a comprehensive evaluation was conducted to reveal the elimination profiles of the antibiotics, identify the fate characteristics in both sewers and WWTPs, assess the exposure risk levels, and propose a control strategy. The total concentration (based on the median concentrations of the target antibiotics) in aqueous waters was estimated to decrease from 7383.4 ng/L at the discharge source to 886.6 ng/L in the WWTP effluent, among which 69.6% was reduced by sewers and 18.4% was reduced by WWTPs. Antibiotic reduction in sewers was a combined effect of dilution, physiochemical reactions, sorption, biodegradation, and retransformation, and the A20-MBR ozonation process in the WWTPs exhibited superior performance in diminishing antibiotics. Notably, accumulated antibiotics in the excess sludge posed a high risk to natural environments (with a risk quotient of approximately 13.0), and the potential risk during combined sewer overflows (CSOs) was undetermined. Thus, enhanced sludge treatment techniques, accurate risk prediction, and proper precautions at CSOs are required to mitigate potential risk. A novel scheme involving an accurate estimation of discharge loads, preliminary treatment of highly concentrated discharge sources, and synergic control in sewers was proposed to eliminate antibiotics at the front end of pipes.