Removal of antibiotics from livestock effluent by two filter-based microbial electrochemical reactors

The widespread use of antibiotics in livestock farming usually results in the environmental release of antibiotics due to inadequate removal capacity of conventional wastewater treatment processes, thereby posing significant ecological risks. For enhancing the removal of antibiotics from livestock effluent, this study developed a filter-based microbial electrochemical reactor (FMER) by integrating microbial electrochemical systems (MES) with biological filter technology. Two FMER configurations with reversed electrode positions, i.e. R1 with the anode positioned near the inlet and the cathode situated downstream, and R2 with cathode positioned near the inlet and the anode situated downstream, were constructed and evaluated. Under an optimized voltage of 1.2 V, both reactors demonstrated high removal efficiency of levofloxacin (LEV), 93.72% for R1 and 90.59% for R2, in synthetic wastewater. When treating secondary effluent of livestock wastewater, the FMERs effectively removed multiple antibiotics at μg/L levels with total removal exceeding 80%, and simultaneously reduced the abundance of ARGs by 95.46% in R1 and 93.95% in R2. The reactor configuration of R1 demonstrated superior stability under short hydraulic retention time (HRT) conditions compared to that of R2. However, this difference in stability became less pronounced at long HRT conditions. Microbial community analysis revealed distinct niche differentiation and functional enrichment in xenobiotics biodegradation pathways in the FMERs. The results indicate that the FMER, particularly the R1 configuration with the anode preceding the cathode, represents a robust and effective process for the advanced treatment of livestock wastewater to control antibiotic pollution and the spread of antimicrobial resistance.