Effects of coupling biofilm on the production of short-chain fatty acids (SCFAs) in sludge anaerobic fermentation

Short-chain fatty acids (SCFAs) could be recovered as valuable resources during sludge anaerobic fermentation. Addition of biofilm carriers might benefit the production of SCFAs by making microbial community more diverse or enriching functional microbial species. This study investigated the effects of three biofilm carriers, i.e. polyethylene (PE), polyurethane sponge (PUS), and granule-activated carbon (GAC), on the production of SCFAs during anaerobic fermentation of waste sludge. Experimental results revealed that the SCFAs production was improved at the presence of PE (2185.82 +/- 61.73 mg/L) or PUS (1994.32 +/- 110.99 mg/L), which were 1.4 and 1.27 times higher than that in the control test, respectively. The addition of GAC did not promote the SCFAs production, and furthermore, the concentration of SCFAs declined much faster than in other tests. High-throughput sequencing results showed that the microbial diversity in slurry was negatively related with the production of SCFAs. An increase in the relative abundance of SCFA consumers both in slurry and in biofilm might be an explanation for the effects of GAC. The findings suggest that the way a suitable biofilm carrier promotes the SCFAs production may be related with the enrichment of functional microbial species rather than a more diverse microbial community.