Enhancement of excess sludge hydrolysis and decomposition with different lysozyme dosage

The performance of the lysozyme catalysis on excess sludge (ES) hydrolysis and decomposition was investigated in this study. For this purpose, the release of soluble organic matters from sludge flocs, extracellular polymeric substances (EPS) changes in composition and distribution and the quantity variations of microorganisms were monitored. Results indicated that lysozyme boosted the ES hydrolysis significantly with approximately 236.5 mg/L soluble chemical oxygen demand (SCOD), 58.6 mg/L polysaccharide and 662.7 mg/L protein release within 240 min at the lysozyme dosage of 150 mg/gSS. Arising lysozyme dosages (from 0 to 150 mg/gSS step by step) could dramatically enhance the efficiency of the enzyme on ES with the concentration of polysaccharide increased from 84.6 mg/L to 143.2 mg/L and protein increased from 325.0 mg/L to 987.7 mg/L in total EPS. The decomposition effect of lysozyme on microorganisms improved with dosage, about 15.4%, 17.5% and 20.2% bacteria and 56.3%, 57.2% and 65.0% archaea were disintegrated at the lysozyme dosages of 50, 100 and 150 mg/gSS, respectively. However, fungi were barely influenced by the enzymatic catalysis. Tryptophan-protein like substances and aromatic protein were the dominant ES lysis compositions in EPS.