Internal driving mechanisms of microbial community and metabolism for granular activated carbon enhancing anaerobic digestion of high-strength sulfate organic wastewater

In this study, the feasibility of enhancing high-strength sulfate organic wastewater anaerobic digestion by adding granular activated carbon (GAC) and the internal driving mechanisms were investigated in up-flow anaerobic sludge blanket (UASB) reactors. The UASB reactor with GAC (GAC reactor) was more stable in COD removal efficiency and CH4 production than that without GAC (non-GAC reactor). When the influent COD concentration increased to 12,000 mg/L with a COD/SO42- ratio of 4.0, the COD removal efficiency and CH4 yield increased by 10.45 % and 20.50 %, respectively. Under inhibition condition with sulfides of 800 mg/L, specific methanogenic activity of GAC reactor sludge increased by 41.8 % compared to that of non-GAC reactor sludge. Electron transport system and microbial community results showed that GAC enhanced microbial activity and improved direct interspecies electron transfer (DIET) between potential electroactive microorganisms and Methanosaeta. Functional enzyme gene analysis demonstrated that GAC enhanced microbial metabolic activity, covering glycolysis, pyruvate metabolism, sulfate reduction, and methanogenesis. Therefore, the enrichment of key microorganisms, the promotion of DIET methanogenesis, and the improvement of functional metabolism activity may be the important reasons for GAC reactor sludge with higher methanogenic activity. Furthermore, synergistic promotion of sulfate-reducing metabolism and methanogenesis may be due to the establishment of potential syntrophic partnership between sulfate-reducing bacteria (Desulfovibrio) and Methanosaeta. This study deciphered internal driving mechanisms of microbial community and metabolism for GAC enhancing anaerobic digestion of high-strength sulfate organic wastewater.