Enhanced anaerobic digestion of waste-activated sludge via bioaugmentation strategy-Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt2) analysis through hydrolytic enzymes and possible linkage to system performance.

In this study, anaerobic digestion of waste-activated sludge was bioaugmented with hydrolytic bacteria, Bacteroidetes uniformis (Bacteroidetes, B) and Clostridium sp. (Firmicutes, F) at various dosages. Bioaugmentation resulted in enhanced methane conversion of waste-activated sludge. The highest methane yield of 298.1 mL CH/g-COD, 85.2% COD conversion efficiency was obtained when Bacteroidetes uniformis and Clostridium sp. were augmented at 100 and 900 CFU/mL, respectively. The microbial community analysis demonstrated that bioaugmentation increased the proportion of Bacteroidetes, Firmicutes, and Proteobacteria. Furthermore, at the highest methane yield, the principal methanogenic pathway was altered from acetoclastic to a mixture of hydrogenotrophic and acetoclastic; the major species shifted from Methanosaeta concilii to Methanobacterium subterraneum. Predicted gene analysis revealed that increased expression of hydrolases resulted in enhanced methane conversion through bioaugmentation.