This study evaluated the performance of a tubular microbial fuel cell (MFC) having a core of air-chamber wrapped with an anion exchange membrane in sewage wastewater treatment. Three MFCs were vertically assembled into one module and floated in sewage water channels before and after treatments in the primary sedimentation tank. The two MFC-modules exhibited nearly similar electricity production in the range of 1.3-5.7 Wh·m −3 -MFC while the bottom MFCs (60-90 cm) showed a decrease in electricity compared with the top (0-30 cm) and the middle MFCs (30-60 cm) due to the water leakage into air-cathode. One MFC module was then evaluated for its chemical oxygen demand (COD) removal efficiency with two external resistances of 27 and 3 in a chemostat reactor (MFC:reactor = 1:5, v/v) using three hydraulic retention times (HRTs), i.e., 3, 6, and 12 h. The best COD removal efficiency (COD-RE MFC ), 54 ± 14%, and BOD removal efficiency, 37 ± 17%, were observed with a resistance of 3 and a 12 h HRT, which resulted in 3.8 ± 2.0 A·m −3 of current recovery and 15 ± 7.5% of Coulombic efficiency. The electricity generation efficiency (EGE MFC ) was the best with a resistance of 27 and a 12 h HRT, accounting for 0.19 ± 0.12 kWh·kg-COD −1 with a 17 ± 6.4% COD-RE MFC and 0.65 ± 0.10 Wh·m −3 electricity production. Based on calculations using the COD-RE MFC and EGE MFC, the integration of MFC treatments prior to aeration can reduce wastewater treatment electricity consumption by 55%.

Graphene oxide (GO) has recently been shown to be an excellent anode substrate for exoelectrogens. This study demonstrates the applicability of GO in recovering electricity from sewage wastewater. Anaerobic incubation of sludge with GO formed a hydrogel complex that embeds microbial cells via π-π stacking of microbially reduced GO. The rGO complex was electrically conductive (23 mS·cm−1) and immediately produced electricity in sewage wastewater under polarization at +200 mV vs. Ag/AgCl. Higher and more stable production of electricity was observed with rGO complexes (179–310 μA·cm−3) than with graphite felt (GF; 79–95 μA·cm−3). Electrochemical analyses revealed that this finding was attributable to the greater capacitance and smaller internal resistance of the rGO complex. Microbial community analysis showed abundances of Geobacter species in both rGO and GF complexes, whereas more diverse candidate exoelectrogens in the Desulfarculaceae family and Geothrix genus were particularly prominent in the rGO complex.

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The oxidation of a carbon anode has been reported to enhance electricity recovery in a microbial fuel cell (MFC).

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