Exogenous N-acyl-homoserine lactones promote the degradation of refractory organics in oligotrophic anaerobic granular sludge

For refractory industrial wastewaters, anaerobic granular sludge technology cannot be widely used because of its limited treatment capacity, so strengthening the anaerobic degradation of refractory organics should be discussed. In this paper, the feasibility of adding exogenous N-acyl-homoserine lactones (AHLs) to promote the degradation of refractory organics in oligotrophic anaerobic granular sludge was addressed. The results showed that, after easily-degradable organics were completely metabolized, exogenous AHLs strengthened the further degradation of refractory organics and improved the methanogenic activity of anaerobic granular sludge. In addition, adding AHLs could promote the secretion of more extracellular polysaccharides and proteins by anaerobic microorganisms to resist the oligotrophic environment. Microbiological analysis showed that adding AHLs significantly optimized the microbial community in oligotrophic anaerobic granular sludge. With the regulation of AHLs, the abundance proportion of hydrolytic acidifying bacteria for refractory organics in bacterial community and the abundance proportion of acetotrophic methanogens in methanogens community increased obviously. Exogenous AHLs showed concentration-related effects on the optimization of bacteria and methanogens, and AHLs of higher concentration were beneficial to the succession of community structure in a better direction. Exogenous regulation of AHLs-mediated QS provided an attractive strategy for enhancing the anaerobic degradation of refractory organics, and proposed a technical idea for the application of anaerobic granular sludge technology in refractory industrial wastewaters.