Occurrence, ecotoxicological risks of sulfonamides and their acetylated metabolites in the typical wastewater treatment plants and receiving rivers at the Pearl River Delta

Sulfonamides (SAs) were frequently detected in various environmental water bodies because of their incomplete removal during wastewater treatment process, and this may lead to a negative effect on aquatic ecosystems. This study investigated six SAs and three of their acetylated metabolites in the influents, effluents, and the receiving river waters from four typical wastewater treatment plants (WWTPs) at the Pearl River Delta in Guangdong province, China. The results indicated that sulfadiazine, sulfapyridine and sulfamethoxazole had the highest detection frequency. Moreover, sulfadiazine and sulfamethoxazole had its maximum concentrations (216 ng/L and 200 ng/L, respectively) in the influent during dry season. To evaluate the compound degradability, the removal efficiency of each individual sulfonamide was calculated, and a modified method to assess it was recommended considering the widespread inter-conversion between SAs and their metabolites. Finally, regarding the effluent and river water, potential environmental risk based on the Hazard quotients (HQs) was estimated towards three diverse non-targeted organisms. Sulfamethoxazole was assessed with the highest HQ (>3.6), being the sole sulfonamide that would pose a risk to algae in the effluents and river waters. Thus, SAs emission needs to be further reduced from WWTPs into the environment.