Selective effect and elimination of antibiotics in membrane bioreactor of urban wastewater treatment plant.

Analyzing the temporal dynamics of antibiotics, antibiotic resistance genes (ARGs) and the functional community could contribute to the regulation and optimization of wastewater treatment plant (WWTP) operation to achieve better antibiotics and ARGs removal performances during different seasons. However, there is little research in this area. Therefore, in this study, samples were collected from the influent, activated sludge (AS), and permeate of the membrane bioreactor (MBR) in a WWTP located in Beijing, China, biweekly over 13 months, and then analyzed systematically. The removal efficiency for all detected antibiotics through biodegradation and adsorption was 59.25 ± 2.79%, with the highest rate of 64.79 ± 4.68% observed in summer, indicating that the higher temperature in summer may promote biodegradation in MBR. In contrast, the elimination of antibiotics through microfiltration was negligible and unfavorable, with negative overall removal rates. However, a positive rejection rate of 9.48 ± 8.92% was only observed in winter, indicating that a colder temperature might lead to better, but still limited, antibiotics rejection. Sulfonamides (SAs) were more likely to impose a selective pressure on their corresponding ARGs. However, due to the degradability of tetracyclines (TCs) and potential selection of ARGs in wastewater before entering WWTP, there were still TC resistances with non-detectable TCs. Significantly negative relationships were observed between the relative abundance of nitrifying bacteria (Nitrosomonas and Nitrospira) and the concentrations of certain antibiotic classes, indicating that nitrifying bacteria could be involved in the co-metabolic biodegradation of certain antibiotics through enzyme catalyzation during nitrification.

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