Mesophiles outperform thermophiles in the anaerobic digestion of blackwater with kitchen residuals: Insights into process limitations

Abstract

Co-digestion of blackwater (BW) and organic kitchen waste (KW) is a promising and effective resource-recovery based approach for municipal waste and wastewater treatment. In this study, anaerobic co-digestion treatments of BW and KW using anaerobic sequencing batch reactors under mesophilic and thermophilic conditions were compared. Our results showed that although higher sludge specific methanogenesis activities were observed in the thermophilic reactor, mesophilic treatment achieved significantly higher treatment capacity and methane production. It was concluded that thermophilic conditions introduced H2 inhibition and reduced activities of syntrophic acetogenic bacteria and syntrophic acetate oxidizing bacteria in the reactor. Further investigation on microbial communities showed significantly different microbial communities between reactors, where Thermotogaceae and Methanothermobacter were the most prevalent bacteria and archaea in the thermophilic reactor, and Cloacamonaceae and Methanosarcina were the most prevalent ones in the mesophilic reactor.