Enhanced electricity generation and organic matter degradation during three-chamber bioelectrochemically assisted anaerobic composting of dewatered sludge

Abstract

Composting microbial fuel cells can generate electricity from recycled organic waste at accelerated degradation rates. However, the problem of high internal resistance (Rint), which results in low power density, is a technical obstacle related to this process, and the preferential conversion of the organic fraction by bioelectrogenesis remains unclear. This study involved designing a novel three-chamber bioelectrochemically assisted anaerobic composting process (AnCBE,III) to dispose of dewatered sludge (DS), which was operated at reduced internal resistance. The maximum power density of the AnCBE,III was higher (7.0–8.6 W/m3) than that of the two-chambered AnCBE,II (4.7–5.7 W/m3), with lower Rint (63.8–88.5 Ω) than that of the AnCBE,II (78.8–98.5 Ω). At the end of composting, the AnCBE,III had higher total chemical oxygen demand (TCOD) removal (42.3 ± 0.5%) than the AnCBE,II (32.1 ± 0.5%). During electrogenesis, the dissolved organic carbon (DOC) [hydrophilic fraction and hydrophobic acid fraction of EBOM] (extracellular biological organic matter) was substantially removed, the hydrophobic neutral fraction of aromatic macromolecules was increasingly solubilized (by 13.2%), and the aromatic protein-like and humic acid-like substances were substantially removed. The results demonstrate that the increases in both the proton exchange area and cathode surface area in the AnCBE,III can enhance electricity generation and organic matter degradation.