Study on the effect of alkali on the production of volatile fatty acids from rhamnolipid‐alkali‐thermal pretreated waste activated sludge

Abstract

This article systematically explores the strengthening effect of NaOH dosage on the fermentation acid production of Waste Activated Sludge (WAS) by the rhamnolipids‐alkali‐thermal combined pretreatment. Analyzed the dissolution characteristics of organic matter in sludge, changes in total volatile fatty acids (VFAs) content and components, and microbial community structure. Research has shown that increasing the amount of NaOH can promote the dissolution of sludge extracellular polymeric substances (EPS) and cell lysis. When NaOH dose was 60 mg/g VS, the dissolution of SCOD was the largest, reaching 5427.78 mg/L. It provides high‐quality substrate for anaerobic flora through the decomposition of refractory humus‐like substances and macromolecular substances, thus improving the production of VFAs. When NaOH dose was 80 mg/g VS, the maximum VFAs yield was 1663.76 mg C/L, and the fermentation type was butyric acid. The increase of NaOH dose promotes the effective enrichment of bacteria, and the dominant bacteria are Proteobacteria, Firmicutes, and Bacteroides at the gate level, with different abundance. The fermentation time plays a decisive role in the evolution of microbial population, and the increase of NaOH dose promotes the enrichment of acid‐producing bacteria, thus improving the production of VFAs.