Enhanced methanogenesis and efficient ciprofloxacin degradation via nZVI@LDH in an electricity-driven anaerobic bioreactor: A biotic-abiotic hybrid system for ROS regulation and ARGs mitigation

Abstract

The escalating presence of antibiotic contaminants in wastewater presents substantial environmental and public health challenges, primarily due to their role in the proliferation of antibiotic resistance genes (ARGs). This study examines the effectiveness of a hybrid system integrating nano zerovalent iron (nZVI) and layered double hydroxides (LDH) in treating wastewater contaminated with ciprofloxacin (CIP). Reactor experiments revealed that incorporating nZVI@LDH mitigated the shock caused by CIP while sustaining a methane production rate that was 116% higher than that of the control group. Furthermore, there was a 50% increase in CIP removal efficiency. Notably, there was a significant enrichment of hydrogenotrophic methanogens, such as Methanobacterium and Methanolinea, in the nZVI@LDH-enhanced reactors. Additionally, the levels of reactive oxygen species decreased by 50%, from 11,813 ± 1,230 to 4,525 ± 1,030 counts/s, and the abundance of ARGs declined by 75% to 88% compared to the control reactors. An external electric field further promoted electron transfer, boosting the relative abundance of electrochemically active bacteria, with Proteobacteria comprising up to 40% of the microbial community in the 1 V + nZVI@LDH reactor. This hybrid system demonstrates significant efficacy in degrading CIP and decreasing ARGs generation, underscoring its potential as a sustainable strategy for managing antibiotic-laden wastewater.