Electroactive biofilm enhanced microbial electrolysis for sewage sludge-to-energy conversion

In this study, a two-chambered microbial electrolysis cell (MEC) was fabricated using a carbon cloth electrode, a Nafion-117 membrane, and Escherichia coli as the biocatalyst. The system treated sewage sludge with an initial chemical oxygen demand (COD) of 14,843 ± 350 mg/L, reducing it to approximately 170 ± 12 mg/L over the operational period. This configuration facilitated a significant increase in cell volume utilization of 89.5%, and achieved a maximum current production of 18.03 mA, along with hydrogen generation of 24.34 ± 1.3 mL at a biomass concentration of 13.5 ± 1.1 g/L. Cell growth contributed substantially to the degradation of organic matter, with sludge consumption reaching 12 g/L. The system produced an output voltage of 1.88934 ± 0.0091 V within 72 h and achieved the highest power density of 261,037 ± 1,245 mA/m². The improved performance is attributed to the unique configuration of intermembranous live cells, highlighting the potential of biological electrocatalysts in advancing MEC technology. Further experiments demonstrated that when the initial COD load was 2,443 ± 175 mg/L, the MEC achieved a maximum COD removal efficiency of 98.5%. These findings emphasize the importance of optimizing sewage sludge substrate concentration to maximize power generation in MECs while simultaneously reducing the environmental burden of sludge biomass.