Biochar-assisted anaerobic membrane bioreactor (BC-AnMBR) towards high-efficient energy recovery from swine wastewater: performances and the potential mechanisms

In this study, a high-efficient energy recovery system of Biochar-assisted Anaerobic Membrane Bioreactor (BC-AnMBR) was established for swine wastewater treatment. Comparing with a conventional AnMBR, biochar addition accelerated VFA degradation during start-up stage, thereby shortened start-up duration by 44.0%. Under a high organic loading rate (OLR) of 21.1 gCOD/L/d, BC-AnMBR promoted COD removal efficiency from 90.1% to 95.2%, and maintained a high energy yield of 4.8L CH4/L/d. The relative abundance of Methanosaeta declined from 53.9% in conventional AnMBR to 21.0% in BC-AnMBR, whereas that of Methanobrevibacter dramatically increased from 10.3% to 70.9%, respectively. Metabolic pathway analysis revealed that introducing biochar not only strengthened hydrogenotrophic methanogenesis pathway, but also upregulated the genes encoding electron transfer carriers and riboflavin metabolism, suggesting the role of biochar facilitating interspecies electron transfer for syntrophic methanogenesis. The excellent energy yield performances under high OLR confirmed BC-AnMBR as an advanced system for high-strength swine wastewater treatment.