Performance Evaluation of Microbial Fuel Cells Using Dairy Wastewater: Effect of Inoculum Concentration on Bioelectricity Generation and Treatment

Abstract

Microbial fuel cells (MFCs) are an emerging sustainable technology that enables simultaneous wastewater treatment and bioelectricity generation. This study evaluates the performance of a laboratory-scale dual-chamber MFC using dairy wastewater as the substrate and sewage as the inoculum. The MFC was operated under an anaerobic anode and aerobic cathode configuration, with a total reactor volume of 5 L and an effective working volume of 2.6 L. The initial physicochemical characteristics of the dairy wastewater were also evaluated. The system was constructed with biochar coated electrodes and an agar–NaCl based proton exchange membrane to enhance electron transfer. Two inoculum concentrations (30% and 40%) were tested over a period of 15 days to assess their effect on power generation and treatment efficiency. The wastewater showed good biodegradability with a BOD/COD ratio of 0.71. The MFC exhibited an initial lag phase, followed by increased voltage generation and gradual decline. The maximum voltage recorded was 0.87 V for the 30% inoculum and 0.86 V for the 40% inoculum. Simultaneously, the 30% inoculum achieved higher COD removal (12.5%), BOD removal (15%), and Coulombic efficiency (22%). SEM analysis confirmed the formation of a stable and dense microbial biofilm on the anode surface. The results indicate that 30% inoculum provides optimal performance for bioelectricity generation and wastewater treatment. Keywords: microbial fuel cells; dairy wastewater; inoculum concentration; biochar electrodes; proton exchange membrane