Potential enhancement of direct interspecies electron transfer for anaerobic degradation of coal gasification wastewater using up-flow anaerobic sludge blanket (UASB) with nitrogen doped sewage sludge carbon assisted

Waste sewage sludge was converted into the novel conductive material of nitrogen doped sewage sludge carbon (N-SC) to enhance anaerobic degradation of coal gasification wastewater (CGW). The results indicated that N-SC played a significant role in enhanced efficiencies, with chemical oxygen demand (COD) removal efficiency increased by 25.4%, methane production rate improved by 68.1% and total volatile fatty acids (VFA) decreased by 37.5% than that of controlled reactor. The conductivity, activity of electron transport, and extracellular polymeric substances (EPS) of anaerobic sludge were remarkably enhanced with N-SC, which promoted sludge granulation and supplied better conductive environment for microorganisms. The microbial community analysis revealed that potential enhancement of direct interspecies electron transfer (DIET) was achieved by electrical connection between enriched Geobacter, Pseudomonas and Methanosaeta with N-SC assisted, which enhanced the anaerobic degradation of CGW. Moreover, anaerobic degradation with N-SC had higher capacity to resist acidic shocks, facilitating the process stability.