Synergistic enhancement of sludge solubilization via acidic pH-driven sodium percarbonate pretreatment

pH= 2 + SPC synergistically boosted WAS solubilization, raising SCOD by 11.8- fold. • Acid activated SPC to generate abundant ·OH, the core species disrupting WAS. • Optimal pretreatment produced 2048.7 mg/L SCFAs and shortened fermentation cycle. • pH= 2 + SPC selectively enriched acidogenic Acinetobacter and Proteiniclasticum . • Salt load caused by pH= 2 + SPC remained tolerable for acidogens. Waste activated sludge (WAS) hydrolysis is critically limited by the recalcitrance of extracellular polymeric substances (EPS) and the complex cellular structures of microorganisms. To address this, a novel acidic pH-driven sodium percarbonate (SPC) pretreatment strategy was proposed in this study. The proposed pretreatment strategy could synergistically enhance sludge solubilization and anaerobic fermentation efficiency. Under effective conditions (pH=2, 0.25 g SPC/g TSS, 4 h), the reactive oxygen species (·OH) generated by SPC disrupted sludge flocs and microbial cell walls, elevating soluble chemical oxygen demand by 11.8-fold and soluble proteins by 11.1-fold, respectively, compared to control group. Acidic pH-driven SPC pretreatment conditions significantly boosted short-chain fatty acids (SCFAs) generation, achieving the peak SCFAs concentration of 2048.7 mg/L, which was an 8.4-fold increase over untreated sludge and 1.25-fold higher than SPC-alone treatment. Acinetobacter and Proteiniclasticum , key genera correlated with SCFAs production, were remarkably enriched throughout the anaerobic fermentation process. Mechanistic studies revealed that acidic pH optimized the Fenton-like oxidation of SPC, promoted the generation of ·OH, improved substrates biodegradability, disrupted sludge surface structure, and created favorable conditions for anaerobic bioconversion. This work provides a practical guidance on optimizing sludge treatment and further advancing developing strategies for resource recovery. Download: Download high-res image (317KB) Download: Download full-size image