Microbial Fuel Cells Simultaneously Treating Sulfide and Nitrate under Different Influent Sulfide to Nitrate Molar Ratios

Microbial fuel cells (MFCs), capable of concurrently treating sulfide and nitrate while generating electricity, were evaluated with various influent sulfide to nitrate molar ratios (S:N ratios). All MFCs displayed a good substrate removal capacity regardless of the S:N ratio (i.e., 5:0, 5:1, 5:2, and 5:3) and produced nitrogen gas, elemental sulfur, and sulfate as major products, while low S:N ratios mediated high sulfate conversion. By setting the S:N ratio to 5:2, the electricity generation was maximized, which was consistent with cyclic voltammetry (CV) curves. Through high-throughput sequencing, the taxonomic distribution of a microbial community in suspended sludge was analyzed; the diversity indices and a principal component analysis (PCA) suggest that the S:N ratios may affect the microbial community in MFCs. However, a Pearson correlation analysis infers that the S:N ratios do not have a significant impact on the richness and diversity of the microbial communities in MFCs involved in the simultaneous treatment of sulfide and nitrate (p > 0.05).