Effects of different carbon sources on the removal of ciprofloxacin and pollutants by activated sludge: Mechanism and biodegradation

This research investigated the effects of ciprofloxacin (CIP) (0.5,5,and 20 mg/L) on SBR sys-tems under different carbon source conditions.Microbial community abundance and struc-ture were determined by quantitative PCR and high-throughput sequencing,respectively.The biodegradation production of CIP and possible degradation mechanism were also stud-ied.Results showed that CIP had adverse effects on the nutrient removal from wastewater.Compared with sodium acetate,glucose could be more effectively used by microorganisms,thus eliminating the negative effects of CIP.Glucose stimulated the microbial abundance and increased the removal rate of CIP by 18％-24％.The mechanism research indicated that Proteobacteria and Acidobacteria had a high tolerance for CIP.With sodium acetate as a car-bon source,the abundance of nitrite-oxidizing bacterial communities decreased under CIP,resulting in the accumulation of nitrite and nitrate.Rhodanobacter and Microbacterium played a major role in nitrification and denitrification when using sodium acetate and glucose as carbon sources.Dyella and Microbacterium played positive roles in the degradation process of CIP and eliminated the negative effect of CIP on SBR,which was consistent with the im-proved removal efficiency of pollutants.