Enhancing phosphorus release and acidogenesis via endogenous iron-activated peroxydisulfate and corn gluten meal in sludge anaerobic fermentation

In this study, a ternary co-fermentation system was developed using iron-phosphorus precipitates (FePs)-bearing sludge, peroxydisulfate (PDS), and corn gluten meal (CGM) to activate PDS through a microbe-mediated endogenous iron cycle, thereby promoting phosphorus (P) release and acidogenesis. Fe(II) was released along with P via the dissolution of Fe(II)Ps, resulting from Fe(III)Ps bioreduction. Subsequently, the released Fe(II) induced PDS activation, which avoided the negative impact of external activators on P release by precipitation with P. The optimal PDS dosage for ternary co-fermentation was 0.2 mM/g TSS. At this dosage, P release efficiency increased from 27.3 % (sludge-only group) to 71.6 % and volatile fatty acids (VFAs) production increased from 41.0 (sludge-only group) to 158.5 mg COD/g VSS. SO 4 ·− and ·OH generated through PDS activation disintegrated sludge flocs to promote encapsulated Fe(II)Ps dissolution and organics release. The concentration of soluble chemical oxygen demand in the sludge-CGM-PDS group was 4.4 times greater than that in the sludge-only group. The increased content and biodegradability of hydrolysates (e.g., protein-like, tryptophan-like, and tyrosine-like substances) contributed to the enrichment of hydrolytic-acidogenic bacteria, resulting in a relative abundance of 40.7 %. Unclassified_c__Ignavibacteria , Clostridium , and Rubrivivax were the dominant hydrolytic-acidogenic biomarkers, which enhanced the intracellular metabolisms of glycolysis, amino acid degradation, and acetogenesis, leading to notable increases in VFAs yields. The relative abundance of phosphate acetyltransferase, a key enzyme in acetate biosynthesis, increased by 8.9 %, thus facilitating acetogenesis. In addition, unclassified_c__Ignavibacteria , as putative iron reducers, were the primary microbes mediating endogenous iron reduction. This study provides valuable insights into the PDS self-activation mechanism and microfloral traits during ternary co-fermentation, contributing to the valorization of FePs-bearing sludge waste.