Performance of anaerobic sludge and the microbial social behaviors induced by quorum sensing in a UASB after a shock loading.

[Display omitted] • A UASB suffered from a shock loading was restored by stage-to-stage OLR regulation. • Balance among functional populations was reestablished in the restoration process. • Performance of functional populations was closely related to specific AHLs secretion. • C 4 -HSL was found as the most dominant AHLs for EPS secretion and AFBs growth. • 3-oxoC 6 -HSL was found as the key signal molecule in enhancing methanogens. To understand the microbial social behaviors regulated by acyl-homoserine lactones (AHLs) in the upflow anaerobic sludge blanket (UASB) during the restored process after a shock loading, the correlation analyses of AHLs and components of extracellular polymeric substances (EPS), AHLs genes and microbes, and AHLs and microbes were investigated. The results showed that the performance could be restored by regulating influent organic loading rate stage-by-stage. A variation in microbial community and endogenous AHLs was also found during the restoration process. It was found that C 14 -HSL had improved the synthesis of protein in EPS and resulted in better aggregation of microbes. C 4 -HSL, as well as C 8 -HSL and 3-oxoC 14 -HSL, could prompt the metabolism of acidogenic fermentation bacteria. While 3-oxoC 6 -HSL was identified as the key signal molecule in enhancing methanogenesis. The present work advanced the understanding of microbial social behaviors and provided an attractive strategy for the restoration of anaerobic digestion after shock loadings. [ABSTRACT FROM AUTHOR]