Enhancing waste activated sludge digestion and power production using hypochlorite as catholyte in clayware microbial fuel cell

• Sludge degradation of 81% achieved within 8 days in MFC with NaOCl catholyte.
• Sludge digestion and power production enhanced in MFC with NaOCl as catholyte.
• MFC using NaOCl as catholyte produced two times more power as compared to oxygen.
• Coulombic efficiency of 3.52% using O2 increased to 13.83% with NaOCl as catholyte.
• Electrochemical analysis indicated faster reduction reaction with NaOCl catholyte.

Waste activated sludge was digested in anodic compartment of dual chambered clayware microbial fuel cell (MFC). Performance of MFC was evaluated using oxygen (MFC-1) and hypochlorite (MFC-2) as cathodic electron acceptors. Power production of 8.7 W/m3 was achieved using hypochlorite as catholyte, which was two times higher than using oxygen (4.2 W/m3). Total chemical oxygen demand of sludge was reduced by 65.4% and 84.7% in MFC-1 and MFC-2, respectively. Total and volatile suspended solids reductions were higher in MFC-2 (75.8% and 80.2%, respectively) as compared to MFC-1 (66.7% and 76.4%, respectively). Use of hypochlorite demonstrated 3.8 times higher Coulombic efficiency (13.8%) than oxygen. Voltammetric and impedance analysis revealed increase in reduction peak (from 8 to 24 mA) and decreased polarization resistance (from 42.6 to 26.5 Ω). Hypochlorite proved to be better cathodic electron acceptor, supporting rapid sludge digestion within 8 days of retention time and improved power production in MFC.