Solubilization augmentation and bacterial community responses triggered by co-digestion of a hydrolytic enzymes blend for facilitating waste activated sludge hydrolysis process

• WAS solubilization could be boosted distinctly by the enzymatic co-digestion.
• The high compressibility of digested WAS might be conducive to a further treatment.
• Bacterial community shifted obviously triggered by the enzymatic co-digestion.
• WAS with high diversity had huge potential to be solubilized by the enzymolysis.
• Rising co-digestion abated community dominance and caused the WAS further lysis.

Performance of a hydrolytic enzymes blend for WAS solubilization augmentation and bacterial community characteristics responses were investigated in this study. The hydrolytic enzymes blend (lysozyme, α-amylase, protease and cellulase) was used to digest WAS with the adding dosage of 0 (control test), 5%, 10% and 15% (enzymes/TSS, w/w, the adding proportion of each enzyme in the mixture was maintained at 1:1:1:1), respectively. Results showed that soluble COD, protein and carbohydrate in solution presented a substantial increase up to about 6000–9000 mg/L, 1500–3000 mg/L and 550–700 mg/L approximately just in 180 min by the enzymatic co-digestion. Moreover, slight augmentation of VSS/TSS inferred that the stubborn substances were solubilized partially in solid phase. Tryptophan protein-like and simple aromatic proteins-like substances were the main digestive compositions in WAS lysis which promoted the biodegradability largely. Increase of particle size and the broad distribution boosted the compressibility of digested WAS. Community traits changes in digested WAS phase contained: (1) bacterial community shifted conspicuously with the enzymes mixture dosage rising which exaggerated the communities’ dissimilarity; (2) community diversity diminished obviously during the enzymatic incubation process, which might decrease the initial community relative stability to cause serious disintegration; (3) community distribution tending to be even with the enhancing co-digestion effect. The observations above sparked an inspiration that the sludge community with high diversity and poor initial evenness might have great potential for carbon resource release by the enzymolysis.