Enhanced Methane Generation from Anaerobic Tridigestion of Organic Solid Wastes by Direct Interspecies Electron Transfer Stimulation
Pengcheng Li, Ziyi Liu, Mingxing Zhao, Hengfeng Miao, Wansheng Shi, Zhenxing Huang, Wenquan Ruan
Abstract
One of the major challenges of anaerobic codigestion (AcoD) treatment of municipal solid waste (MSW) is the low efficiency of electron transfer between syntrophic bacteria and methanogens. In this study, an effective strategy to improve the methanogenesis efficiency during tridigestion of food waste (FW), kitchen waste (KW), and fruit/vegetable waste (FVW), via adding magnetite to promote direct interspecies electron transfer (DIET), was proposed. The results showed that the accumulative methane yield increased with the addition of magnetite and the maximum cumulative methane yield was 592.56 mL/gVS at the dosage of 6 g/L and was 31.97% higher than control. Magnetite significantly accelerated the degradation of volatile fatty acids (VFAs), such as acetic, propionic, and butyric acids. Electrochemical measurements and scanning electron microscopy (SEM) analyses showed that magnetite attached to the surface of the sludge and improved the redox capacity of inoculated sludge; the values of electron-donating capacity (EDC) and electron-accepting capacity (EAC) increased by 21.58 and 23.69%, respectively. Microbial community analysis revealed that the dominant bacteria were Chloroflexi, Firmicutes, and Actinobacteria. The growth of Methanosaeta and Methanosarcina was promoted after adding magnetite to the system, which also contributes to the enhanced methane production via involving in DIET during the anaerobic tridigestion process.