Effects of antibiotic exposure on bioreactor treatment efficiency and dynamic migration of resistance genes in landfill leachate

Abstract

Different concentrations of tetracycline (TC) (10 and 30 mg/L) were added to the anaerobic-anoxic-aerobic reactor to investigate the changes in effluent quality, sludge performance and the dynamic migration of antibiotic resistance genes (ARGs) in simulated landfill leachate. The maximum removal rates of COD, TN, and TP occurred at a TC concentration of 10 mg/L, reaching 75.99 %, 50.46 %, and 60.26 %, while the removal efficiency of NH3-N continued to decline. Microorganisms secreted abundant extracellular polymeric substance (EPS) and combined with antibiotic to form a stable and dense EPS antibiotic complex to resist adverse stress. The concentration of heavy metals showed a trend of first increasing and then decreasing, especially Mn and Zn. At a concentration of 10 mg/L TC, aerobic condition weakened ARGs, while anaerobic facilitated the proliferation of ARGs. The tetA and tetM in leachate were positively correlated with TC, TP, TN, NH3-N, and COD (P < 0.05), while the diffusion and transmission of ARGs in sludge were under the superimposed pressure of TC, various heavy metals, and EPS. Moreover, changes in bacterial communities drove the release of ARGs. To analyze the potential risks of ARGs in landfill leachate under antibiotic exposure, providing clues for the management and risk assessment of sewage biological treatment facilities.