Effects of polysorbate-20 via associated microbial interactions on facilitating the production of volatile fatty acids during anaerobic fermentation of waste activated sludge

Aiming at the problems of low efficiency of sludge lysis, and low yield of volatile fatty acids (VFAs) during waste activated sludge (WAS) anaerobic fermentation, this study proposed a research scheme to boost the efficiency of VFAs production by WAS anaerobic fermentation via polysorbate-20 pretreatment. Results indicated that when dosage of polysorbate-20 pretreatment was 0.3 g/g VS, after 4 hours of pretreatment, the soluble chemical oxygen demand (SCOD) increased to 4332 mg/L. The production of VFAs researched the maximum, 87.09 mg COD/g VS, on the fourth day of the sludge fermentation via polysorbate-20 pretreatment. Mechanism explorations unraveled that polysorbate-20 promoted sludge solubilization and organic matter release. It improved the activity of hydrolase and the abundance of related hydrolytic acid-producing bacteria (like Clostridium, Longilinea and Tissierella), and enhanced the hydrolysis efficiency of organic substances and the efficiency of microbial metabolism to produce VFAs. In addition, polysorbate-20 pretreated sludge had lower capillary suction time after fermentation. Overall, polysorbate-20 could play a positive role in the conversion of solid sludge organic matter transformed into VFAs, and improve the dewatering performance of sludge after anaerobic fermentation, which was demonstrated to turn into an effective strengthening strategy for prospective WAS treatment / bioresource recovery. [Display omitted] •Polysorbate-20 pretreatment promoted the solubilization and hydrolysis of sludge.•Polysorbate-20 pretreatment enhanced the production of VFAs, mainly acetic acid.•Microbial mechanism of polysorbate-20 pretreatment promoting VFAs production was revealed.•Polysorbate-20 pretreatment improved the dewatering performance of fermented sludge.