An innovative application of osmotic microbial fuel cell (OsMFC) for enhanced activated sludge thickening and stabilization with bioelectricity generation

Abstract

Waste activated sludge (WAS) management presents significant challenges due to its complex composition and the high cost associated with conventional treatment methods. This study investigates the potential of osmotic microbial fuel cell (OsMFC) technology for WAS thickening, stabilization, and bioelectricity generation. Compared to conventional microbial fuel cells (MFCs), OsMFCs offer several advantages, including enhanced sludge thickening performance, improved organic matter degradation efficiency, and increased bioelectricity generation. The OsMFC achieved substantial sludge thickening, with the total suspended solids (TSS) increasing from 1,753, 11,650, and 3,565 mg/L in the OsMFC to 28,550, 28,500, and 20,340 mg/L, respectively, over three consecutive operating cycles with a sludge retention time of 16 days. The total chemical oxygen demand (tCOD) mass reduction in the OsMFC averaged 90.7 %, outperforming the MFC, which achieved 61.3 %. This indicates the superior performance of the OsMFC in organic sludge digestion. Further supporting this, the VSS/TSS ratio of treated WAS was effectively reduced from 0.64 to 0.37, with an average VSS mass reduction of 65.0 % obtained in the OsMFC. Additionally, OsMFC treatment modified the physicochemical properties of the WAS, resulting in smaller floc particle size, and reduced zeta potential, potentially enhancing sludge dewaterability. Furthermore, OsMFC exhibited superior bioelectricity generation compared to MFC, with maximum power densities averaging 1,704.6 mW/m³, outperforming that of 762.3 mW/m³ observed in comparing MFC. Despite its promising potential, further research is needed to optimize OsMFC operation and fully understand its mechanisms. Overall, this study highlights the potential of OsMFC technology for sustainable and efficient management of WAS within the circular economy framework.