Residual Characteristics and Ecological Risk Assessment of Antibiotics in Typical Sewage Discharge Sources in Northern Jiangsu, China, During Summer

Wastewater is the primary source of environmental pollutants, particularly antibiotics. Clarifying their residual characteristics and ecological risks is crucial for safeguarding water quality and human health and has garnered widespread global attention. However, the complexity of wastewater sources and the diversity of antibiotics make their residual characteristics and ecological risks unclear. Concentrations of major antibiotics were investigated in eight typical sewage discharge sources (one rural source, three urban sewage treatment plants, a chemical industrial park, a hospital, a chicken farm, and a cattle farm) in northern Jiangsu Province, China. This study evaluated the removal efficiency of antibiotics by treatment processes and the ecological risks posed by antibiotics in effluents. Results show that 29 antibiotics from five categories were detected in the eight sources: including eight fluoroquinolones, 13 sulfonamides (SAs), four tetracyclines, two penicillins, and two macrolides, with a detection rate of 12.5%-100%. The detection rates of ofloxacin (OFX), sulfamethoxazole, and doxycycline (DOX) is 100%. Total antibiotic concentration ranged from 303.41 to 7 414.71 ng·L^-1, with the highest concentration observed at the cattle farm. Individual antibiotic concentrations varied from 0.00 to 3 482.00 ng·L^-1, with the highest concentration detected for DOX at the chicken farm. The sewage treatment systems removed 82.13% to 96.43% of antibiotics, with the highest removal efficiency in the chemical industrial park. This system was particularly effective at removing SAs, whereas other sources showed lower SAs removal efficiencies. Risk quotient sum (RQ_sum) of antibiotics in the eight sewage sources ranged from 3.57 to 143.80, indicating high ecological risk levels. Among them, RQ_sum value for OFX exceeded 1 across all eight sources, contributing 7.22%-84.72% to RQ_sum, emphasizing the need for further attention. The findings provide valuable data to support the management of effluents from sewage treatment plants, optimization of sewage treatment processes, and prevention and control of antibiotic pollution.