Treatment of waste activated sludge and the enhancement mechanism for electron transfer in an osmotic microbial fuel cell.

The osmotic microbial fuel cell (OsMFC) is a novel technology that can achieve electricity generation and water recovery while stabilizing and dewatering waste activated sludge (WAS). By examining electricity generation, WAS stabilization, microbial community shifts, meta-transcriptomic changes, and the enhancement mechanism of electron transfer, this study demonstrated significant advantages of an OsMFC in treating WAS over a conventional microbial fuel cell (MFC). Compared with typical MFCs, the OsMFC performed better in terms of maximum power density (260 mW·m⁻2), removal of total chemical oxygen demand (76%), and WAS thickening, dewatering, and hydrolysis. In the OsMFC, membrane foulants consisted mainly of polysaccharides, proteins, and cells, but back flushing was effective in restoring membrane performance by alleviating pore blockage. Electrogenic genera (such as Geobacter and Rhodopseudomonas) were enriched in the OsMFC, which also showed increased expression of genes for energy generation and carbohydrate catabolism. A denser biofilm, higher microbial activity, and higher concentration of cytochrome c point to an enhancement of electron transfer in the OsMFC. This study provides a foundation for further application of OsMFC towards more sustainable WAS treatment.