Synchronous high removal efficiency of chlorhexidine and enrichment of antibiotic resistance genes in medical sewage fed microbial fuel cell

Chlorhexidine (CHX) is a commonly used disinfectant in clinical settings. In recent years, the dosage of CHX increased significantly due to the combat towards pandemic COVID-19 worldwide. This study investigated the performance of medical sewage fed microbial fuel cells (MFCs) for simultaneous CHX degradation and electricity generation. Meanwhile, the evolution of typical antibiotic resistance genes (ARGs) in medical sewage is also explored. The maximum degradation rate of CHX was 77.6% at the concentration of 5 mg/L. In contrast, the highest COD removal efficiency (96.8%) was achieved at 20 mg/L CHX. The relatively low CHX concentration enhanced the performance of MFC due to the membrane binding capability of CHX and enhanced electron transfer. Quantitative PCR (qPCR) analysis indicated that representative ARGs ( tet Q , sul 2 , and erm B ) from medical sewage accumulated within the anode biofilm; meanwhile, the maximum power density dramatically increased from 138.4 mW/m 2 in the control group to 240 mW/m 2 upon addition of 20 mg/L CHX. Furthermore, Proteobacteria were found to be dominant in the anode microbial community. When the MFCs were conducted with different concentrations of CHX, the abundance of common drug-resistant bacteria including Pseudomonas , Klebsiella and Acinetobacter and ARGs were synchronously decreased. These findings demonstrate MFCs hold considerable promise for application in antiseptic wastewater treatment, enabling efficient CHX degradation, COD removal and energy recovery. • Degradation of chlorhexidine (CHX) was demonstrated in medical sewage-fed microbial fuel cell (MFC). • Maximum CHX degradation of 77.6% at 5 mg/L and COD removal of 96.8% at 20 mg/L CHX were achieved. • Low CHX concentrations (5–20 mg/L) enhanced power output up to 240 mW/m² by reducing internal resistance. • Antibiotic resistance genes ( tetQ, sul2 , ermB ) were enriched on anode and reduced under high CHX stress.