Effect of rhamnolipid on the performance of compound thermophilic bacteria agent pretreatment system for waste sludge hydrolysis.

This study innovatively introduced rhamnolipid (RL) to compound thermophilic bacteria (TB) agent pretreatment system for further accelerating the waste sludge hydrolysis and substrates transformation. The results showed that combined pretreatment was beneficial for the sludge extracellular polymers (EPS) rupture and dissolved organic matters (DOM) release. In the optimal dosage of 40 mg/g SS RL, the activities of protease and α-glucosidase increased by 20.7 % and 33.3 % than that without RL addition, respectively. The addition of RL enhanced efficient contacts between hydrolases and organic substrates, and excitation emission matrix (EEM) spectrum revealed that combined pretreatment with 40 mg/g SS RL could achieve higher soluble microbial by-products occupancy (54 %) and lower fulvic acid-like substances (6 %) occupancy in DOM, promoting the waste sludge biodegradability. High organics availability conducted to more shifts in microbial community structure, compared with TB agent pretreatment, the relative abundance of genus Geobacillus and norank_f__Synergistaceae were enhanced by 29.08 and 0.33 times in combined pretreatment system, respectively, which was conducive to sludge hydrolysis and subsequent anaerobic fermentation process.