Effect of anaerobic sludge on the bioelectricity generation enhancement of bufferless single-chamber microbial fuel cells

Enhancing the self-buffering capacity is critical in the operation of bufferless microbial fuel cells (BLMFCs). Inorganic carbon (IC) is an ideal endogenous buffer, but its spontaneously accumulated concentration is insufficient to adjust anolyte pH. In this study, BLMFCs were operated with anaerobic sludge to enhance IC accumulation and increase anolyte pH. The accumulated IC concentration during a single running cycle was elevated from 8.3 mM to 12.5 mM, and anolyte pH remained above 7.5. The electric power output was significantly promoted from 332.2 mW·m^-2 to 628.1 mW·m^-2, and the coulombic efficiency (CE) slightly increased from 16.4% to 19.5%. Geobacter was the electro-active genus in the anode biofilms of the MFCs, and its relative abundance in the KCl-S anode biofilm increased from 0.2% to 5.75%. After continuous operation, the predominant genus of the anaerobic sludge had changed from Flavobacterium to Fusibacter.