Synergistic effect and microbial community structure of waste-activated sludge and kitchen waste solids residue mesophilic anaerobic co-digestion

Abstract

Anaerobic co-digestion was conducted on the solid residues after three-phase separation of kitchen waste (KWS) and waste-activated sludge (WAS), the synergistic effects and process performance were studied during co-digestion at different ratios of KWS to WAS. KWS and WAS mix ratios of 0:1, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1 and 1:0 (based on TS). The results showed that a ratio of KWS to WAS of 1:1 got a very high methane recovery with a methane yield of 310.45 ± 30.05 mL/g VSadded. The highest concentration of free ammonia among all reaction systems was only 70.23 ± 5.53 mg/L, which was not enough to produce ammonia inhibition in the anaerobic co-digestion system. However, when the KWS content exceeded 50%, methane inhibition and prolongation of the lag phase were observed due to the accumulation of volatile fatty acids (VFAs), and during the lag phase. Microbial community analysis showed that various bacterial groups involved in acid production and hydrolysis were mainly dominated by phylum Firmicutes, Chloroflexi, Proteobacteria and Bacteroidetes. Hydrogenotrophic methanogen was found to dominate all archaeal communities in the digesters. Co-digestion of KWS with WAS significantly increased the relative abundance of Methanobacterium compared with anaerobic digestion of WAS alone. HIGHLIGHTS Anaerobic co-digestion of solid residue after three-phase separation of kitchen waste and waste-activated sludge.; When the ratio of KWS to WAS was 1:1, the methane recovery was higher and was 310.45 + 30.05 mL/g VSadded.; As the amount of KWS added increased, the protein-like fluorescence intensity increased in the co-digestion system.; Hydrogenotrophic methanogen (Methanobacterium) dominated all archaeal communities in the digesters.;

Keywords

• anaerobic co-digestion
• kitchen waste solids
• microbial community
• waste-activated sludge