Mechanistic insights into Fe²⁺/Sodium percarbonate pretreatment for optimizing volatile fatty acid yields from waste activated sludge

Anaerobic fermentation technology presents significant advantages in waste activated sludge treatment, encompassing sludge reduction, detoxification, and resource recovery, primarily by generating high-value volatile fatty acids (VFAs). This study systematically investigated the enhancement effects of Fe²⁺/sodium percarbonate (SPC) pretreatment on sludge disintegration and organic matter hydrolysis. The optimal pretreatment conditions (initial pH=3, SPC dosage=0.3 g/g TSS, Fe²⁺ dosage=0.3 g/g TSS) resulted in a maximum VFAs production of 1598 mg COD/L, representing a 7.26-fold increase compared to untreated sludge. Under these conditions, acetic acid accounted for 52.9 % of the total VFAs. The mechanistic analysis demonstrated that Fe²⁺/SPC pretreatment selectively enriched hydrolytic-acidogenic microbial communities while inhibiting VFAs-consuming populations, thereby directing metabolic flux toward acid accumulation. These findings establish an innovative technical approach and provide a mechanistic framework for advanced resource recovery from waste activated sludge.