Antibiotics in wastewater of Guangdong, China: distribution patterns, and their environmental risk due to incomplete removal.

In this study, the occurrence, removal, spatial distribution and environmental risks of ten antibiotics in 38 wastewater treatment plants (WWTPs) which located in 15 communities (in 12 cities) of the Guangdong province, China. The results indicated that amoxicillin (AMO, 381.00-5230.00 ng·L) and ofloxacin (OFX, 7.01-836.00 ng·L) were predominant in the province with high detection rates (100 %) and high concentrations. The concentration of norfloxacin (NFX) was high in some influents (2070.00 ng·L), but its detection rate was only 47.4 %. In addition, the average daily mass load per 10 capita (ADMLpc) of AMO (383.34 mg·(10 capita)·d) was significantly higher than the other antibiotics. The comparison between the ADMLpc and social-economic factors indicated that adult (age between 18 and 60) was the age group mainly consume antibiotics in the province. Furthermore, the ADMLpc of human antibiotics (e.g., AMO and OFX) were positively affected by the economic development of the region. Comparatively, the ADMLpc veterinary antibiotic (e.g., SMM) was positively related to the livestock related factors. In general, no significant difference (p > 0.05) in antibiotic removal efficiencies among four treatment processes applied in all WWTPs. Nevertheless, the low removal rates of sulfamethazine (SMZ, 44.6 %) and OFX (26.3 %) indicated that they were more difficult to be removed than other antibiotics. Furthermore, high ADMLpc of antibiotics in the influent would cause high ADMLpc in effluents. Therefore, heavy consumption of antibiotics could pose high risk to the ecosystem, especially when multiple antibiotics appeared in the effluent of the WWTPs.