Performance and Microbial Community Evolutions in Anaerobic Fermentation Process of Waste Activated Sludge Affected by Solids Retention Time

Abstract

The effect of solids retention time (SRT) on volatile fatty acids (VFAs) accumulation and microbial community evolutions in enzymolysis-pretreated waste activated sludge (WAS) fermentation process was investigated. SRT played important roles on VFA accumulation efficiency and composition with a best performance of over 2200 mg COD/L at an SRT of 8 days. Volatile suspended solids (VSS)/total suspended solids (TSS) of fermentative sludge decreased obviously during the fermentation tests at various SRTs. Distribution spread index (DSI) of fermentative WAS augmented from 1.175 to 1.218 in accordance with SRT rising from 6 to 11 days. SRT changes led to microbial community (bacterial and archaeal) shifts clearly as well as the community diversity in the fermentation system. Bacterial community evenness tended to be more uneven at an SRT of 8 days compared to SRTs of 6 and 11 days, which indicated that high dominance of bacterial community could be formed at 8 days SRT with more VFA accumulation in WAS fermentation system. RDA inferred that microbial consortia could be driven by the preponderant individual VFA accumulation (acetate, propionate, and N-butyrate) with getting to a relative balance level by SRT optimization in the system.