Carbon cloth-mediated direct interspecies electron transfer effect on the intensification mechanism of high-load...

Acidification under high organic loading conditions and control of dynamic membrane (DM) thickness remain major challenges in the development of anaerobic dynamic membrane bioreactors (AnDMBR). In anaerobic digestion (AD), conductive materials can promote electron exchange between electron donors and acceptors, thereby accelerating electron transfer and enhancing direct interspecies electron transfer (DIET). These processes can improve methane yield and process stability at higher organic loading rates (OLRs). In this study, a carbon cloth anaerobic dynamic membrane bioreactor (CC-AnDMBR) was constructed and compared with a common nylon mesh anaerobic dynamic membrane bioreactor (NM-AnDMBR) to investigate the impact of DIET reinforcement on system performance and stability. The maximum load tolerance of the system and changes in microorganisms during this process were further evaluated to elucidate the mechanisms underlying enhanced system resilience. At a hydraulic retention time of 6.25 days (OLR of 20.13 g COD/L/day), the methane production rate of the carbon cloth reactor (313.74 ± 41.06 mL/g COD) was significantly greater than that of the nylon mesh reactor (256.02 ± 63.29 mL/g COD). Metagenomic analysis revealed that carbon cloth membranes are more conducive to the enrichment of Geobacter, which can exchange electrons with the dominant archaeal genus Methanosarcina, thereby accelerating the DIET rate within the CC-AnDMBR. The enhanced performance of the carbon cloth reactor was attributed to the higher electrical conductivity, more negative oxidation-reduction potential value, and higher electron transport system activity of the sludge. These characteristics together created a more conducive environment for conductive microorganisms and improved the system's electron transfer rate.