Occurrence, removal and ecological risk assessment of antibiotics in rural domestic wastewater treatment systems in the Beijing-Tianjin-Hebei region.

The pervasive usage of antibiotics has raised increasing concerns regarding their discharge into the environment through domestic wastewater. Relevant studies on antibiotics in rural domestic wastewater has mainly focused on their occurrence characteristics and environmental risks, leaving aside the effectiveness of different wastewater treatment processes and their correlation with conventional pollutant removal. Meanwhile, the antibiotic features across the Beijing-Tianjin-Hebei (BTH) region remain unclear. In this study, 13 rural domestic wastewater facilities, using Anaerobic-Anoxic-Oxic (A2/O) and Anaerobic-Anoxic-Oxic processes with Membrane Bioreactor (A2/O+MBR) processes, in the BTH region were investigated. A total of 22 antibiotics were detected at μg/L levels in both influent and effluent, including enrofloxacin, ciprofloxacin, norfloxacin, and oxytetracycline. There was no significant difference in the removal efficiency of most detected antibiotics between the A2O and A2O+MBR processes. In anaerobic and anoxic units, tetracyclines were significantly removed, and azithromycin removal was significantly positive in relation to chemical oxygen demand. While aerobic units showed broader antibiotic removal, and the removal of total nitrogen was significantly negative in relation to most quinolones (QNs). Three facilities were identified as high-risk due to high effluent risks, which require further treatment. The high-risk antibiotics in the effluents were predominantly QNs (73.9 %).