The bio-cathode of microbial fuel cells systems: Performance analysis under different microbial community conditions

This study aims to investigate the conversion of different microbial community compositions in the cathode chamber in a dual-chamber bioelectrochemical system. A denitrifying bacterial community, or sludge, was enriched for denitrification by microbial consortia and subsequently acclimatized within the cathodic chamber of microbial fuel cells, either within a mixed microbial community sludge microbial fuel cell (M-MFC) or a pure culture of microorganisms in a microbial fuel cell (P-MFC). The bioelectrochemical systems were treated with different nitrate concentrations in the cathodic chamber: the MFC with low concentration nitrate (MFC 1 , 25 mg/L nitrate; MFC 2 50 mg/L nitrate), the MFC with medium concentration nitrate(MFC 3 , 75 mg/L nitrate; MFC 4 100 mg/L nitrate), and MFC with high concentration nitrate (MFC 5 , 125 mg/L nitrate; MFC 6 150 mg/L nitrate; MFC 7 175 mg/L nitrate), and the initial COD in the anodic chamber was based on demand(C to N ratio is 5). M-MFC exhibited better-electrogenerated capability than P-MFC. However, P-MFC exhibited better nitrogen removal performance compared to M-MFC . The best performance was attained by both types of MFCs when the nitrate content was 100 mg/L. The maximum output voltages in M-MFC 4 and P-MFC 4 were 449 mV and 171 mV, respectively. The average conversion rate of M-MFC 4 and P-MFC 4 were 2.9 mg*L −1 *h −1 and 10.5 mg*L −1 *h −1 , respectively. The analysis of the microbial community of two treated MFCs in the cathode chamber in the optimal state indicated that non-electrode denitrification predominantly occurs in P-MFC. The cathode chambers were mostly populated by denitrifying microorganisms. The dominant species in M-MFC were Azonexus, Zoogloea, Ignavibacterium , and Pirellula , and the dominant species in P-MFC were Comamonas , Aeromonas , and Acidovorax . The species was assessed by qPCR analysis, and the results validated the use of a bacterial consortium for domestication as a more suitable method to improve the stability and performance of the MFCs.