Sustained energy production from wastewater in microbial fuel cell: effect of inoculum sources, electrode spacing and working volume.

The present study was aimed at producing enhanced and sustained bioelectricity from distillery wastewater in a double chamber microbial fuel cell (MFC) by changing inter-electrode distance, inoculum and reactor volume. Using double chamber MFC with 1 L working volume, when the distance between the electrodes was kept shorter (1 cm), it generated power density of 1.74 W/m3, which was 42.5% higher than that of MFC with electrode spacing of 10 cm (1 W/m3). Using inoculum from different sources viz. garden soil (MFC-GS), wetland sediment (MFC-WS) and sludge from wastewater treatment plant (MFC-S), the highest open circuit voltage (OCV) of 0.84 V and power density of 2.74 W/m3 were produced by MFC-WS, which also showed sustained electricity production (1.68 W/m3) from the wastewater during a 10-day experiment. Relatively lower power density was generated from MFC-S (1.42 W/m3), while that from MFC-GS was the lowest (0.94 W/m3). Bioelectricity generation and overall performance were then assessed using a smaller reactor size. Smaller working volume of MFC (250 ml) favoured greater production of power density (3.2 W/m3) than that with 1 L working volume (2.96 W/m3) with electrode distance of 1 cm. The present study was novel in selecting a suitable mixed-microbial inoculum out of the diverse sources screened and reducing resistance by sharply narrowing down inter-electrode distance and reactor volume, which led to significantly enhanced and sustained electricity generation from double chamber MFC. © King Abdulaziz City for Science and Technology 2021.