Effect of Methyl Orange Dye Concentration on Decolorization and Bioelectricity Generation in an Earthen Membrane Cylindrical Microbial Fuel Cell Reactor

Microbial fuel cells (MFCs) offer a sustainable approach for simultaneous azo dye removal and bioelectricity generation from wastewater. In the present study, the effect of methyl orange (MO) dye concentration on the performance of an earthen membrane cylindrical MFC was evaluated under long-term operation. Five MFC configurations, in duplicate, were operated with acetate-fed anodes for 22 operational cycles with dye concentrations ranging from 20 to 100 mg L⁻¹. Throughout the study, stable decolourisation was observed with maximum dye removal efficiencies of 90.0%, 88.1%, 87.8%, 86.9%, and 86.0% at 20, 40, 60, 80, and 100 mg L⁻¹ MO, respectively. The highest power density obtained was 48 mW m⁻² for an MO concentration of 60 mg L⁻¹. Reduced power generation at higher dye concentrations (>60 mg L⁻¹) may be due to inhibitory effects on microbial electron transfer. Considering decolourisation, power output and coulombic efficiency together, 60 mg L⁻¹ was identified as the optimal MO concentration, whereas up to 100 mg L⁻¹ could still be decolourised by >85% at the cost of lower power output. The results indicate that low-cost earthen membrane cylindrical MFCs are a potential technology for sustainable wastewater treatment and can effectively decolourise MO while recovering bioenergy under prolonged operation.