Electricity generation and microbial community in a submerged-exchangeable microbial fuel cell system for low-strength domestic wastewater treatment

A submerged type microbial fuel cell (MFC) system, which consisted of six readily exchangeable air–cathode MFCs, was evaluated for continuous treatment of low-strength domestic wastewater. When supplied with synthetic wastewater (COD 100 mg/L), the system showed increasing maximum power densities from 191 to 754 mW/m2 as COD loading rates increased (0.20–0.40 kg/m3/day). COD removal efficiencies decreased with increased COD loading rates but the effluent COD concentrations met the relevant effluent quality standard (CODMn 20 mg/L) at all conditions. The system was then operated with domestic wastewater (c.a. 100 mg COD/L) at 0.32 and 0.43 kg/m3/day. The system showed much lower power densities (116–149 mW/m2) at both loading rates, compared to synthetic wastewater. Anodic microbial communities were completely different when the wastewater type was changed. These results suggest that the newly developed MFC system could be applied to treat low-strength domestic wastewater without requiring any additional organic removal stage.

► We developed a submerged exchangeable-microbial fuel cell (SE-MFC) system for treating low-strength wastewater. ► We examined the performance of the SE-MFC system using synthetic and domestic wastewater with various COD loading rates. ► As COD loading rates increased, power density increased but COD removal efficiency decreased. ► The newly developed system successfully treated domestic wastewater at 0.32 kg-COD/m3/day without additional processing. ► Microbial communities in the two wastewater types were entirely different.