Microbial electrolysis cell as an effective tool for mitigating the toxic effects of Cu2+ on microorganisms in the acid mine drainage treatment: Efficacy and mechanisms

It is poorly understood how the mechanism of heavy metals affect sulfate-reducing bacteria (SRB) in microbial electrolysis cell (MEC) system, however, this is essential to improve the effectiveness of sulfate reduction in acid mine drainage (AMD). This study evaluated the impact of Cu2+ on MEC performance using SRBs enriched biocathode. The sulfate reduction rate and pathway, the fate of Cu, as well as the succession of microbial community were investigated. Results showed that MEC performance was optimized at influent Cu2+ concentration of 20 mg/L, while slight inhibition was observed at 40 mg/L. The removal of Cu2+ was accomplished through bioprecipitation and biosorption, forming CuS and Cu(OH)2. However, MEC performance was inhibited at higher Cu2+ concentrations (60 mg/L) due to damaged cell structure, increased charge transfer internal resistance, and altered microbial communities. Specifically, the relative abundance of Firmicutes and Bacteroidota decreased, and functional genes related to sulfate reduction metabolism were reduced, leading to impairment of the assimilatory and dissimilatory sulfate reduction pathways. This knowledge provides revealing insights and theoretical support for developing a feasible approach to realize the treatment of wastewater containing multiple pollutants.