Three-stage anaerobic co-digestion of food waste and waste activated sludge: Identifying bacterial and methanogenic archaeal communities and their correlations with performance parameters.

A three-stage anaerobic digester setup was configured and evaluated for enhanced methane production during co-digestion of food waste and waste activated sludge and the corresponding bacterial and methanogen communities were characterized. Results showed that the average methane yield (0.496 L/gVS) in the three-stage digester was 13-52% higher than that of one- and two-stage digesters. Compared to controls, an increase of 12-47% in volatile solids reduction was achieved in the three-stage digester (69.3 ± 6.7%). Bacterial phyla Proteobacteria, Firmicutes and Bacteroidetes dominated in one-, two- and three-stage digester while genera Pseudomonas, Tissierella, and Petrimonas were selectively enriched in the three-stage digester due to functional segregation. Taxonomic analysis identified 8 dominant methanogen genera, of which Methanosarcina, Methanosaeta, Methanobacterium and Methanolinea collectively accounted for 80%. With increasing OLR and digester stage number, the dominant methanogenic pathway shifted from hydrogenotrophic pattern to acetoclastic pattern and reached a final synergy of these two.