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 this study, we evaluated the effect of methyl orange (MO) dye concentration on the performance of a cylindrical earthen-membrane MFC 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 decolorization 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 decolorization, 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 decolorized by >85% at the cost of lower power output. The results indicate that low-cost earthen-membrane cylindrical MFCs are a promising technology for sustainable wastewater treatment and can effectively decolorize MO while recovering bioenergy during prolonged operation.