Enhancing short-chain fatty acids recovery through anaerobic fermentation of waste activated sludge with cation exchange resin assisted lysozyme pretreatment: Performance and mechanism

Short-chain fatty acids (SCFAs) biosynthesis through anaerobic fermentation has attracted increasing attention for achieving economic benefits and carbon recovery in waste activated sludge (WAS) management. Lysozyme has been reported as a promising biological pretreatment for WAS hydrolysis and SCFAs generation, whereas the low efficiency and high dosage limited its application. In this study, cation exchange resin (CER) was innovatively employed for extracellular polymer substances (EPS) disruption, expecting to promote the lysozyme-induced enzymolysis and solubilization of dissolved organic matters (DOMs). With 3 g/g SS CER and 0.10 g/g SS lysozyme, 5404 mg/L SCOD (i.e. 36.5% of TCOD) and 43.1% VSS reduction rate were realized in the coupled pretreatment, which were 2.63 and 2.09 times than those with sole lysozyme pretreatment. Large amounts of DOMs were released attributed to EPS disruption and cell lysis, leading to 3760 mg COD/L SCFAs accumulation mainly composed of acetic and propionic acids (i.e. occupying 59.7–65.3%). The coupled pretreatment boosted the enrichment of hydrolysis and SCFAs production bacteria, accompanied by the corresponding metabolic functions enhancement (i.e. organic matters metabolism, microbial proliferation and membrane transport). The new sight into the potential mechanism between lysozyme and CER was proposed, and the engineering implication was demonstrated. The findings provided an environmental and economical solution to realize carbon recovery in WAS management.