Study On The Influencing Factors To Related Functional Enzymatic Activity During Sludge Digestion In Microaerobic Conditions

Activated sludge process is used widely in biological wastewater treatment, but it willproduce large amounts of excess sludge, which maybe lead to potential environmentalpollution if not properly disposed. So how to realize the reduction of sludge quantity andvolume have be focused by researchers both at home and abroad.At present, thecommon sludge treatment techniques include sludge concentration, dehydration,digestion, drying, etc., but taking the different regions, environment, cost or otherfactors into consideration, the above techniques all have some limitations.Solubilization by thermophilic enzyme （S-TE）is a new technology for sludgetreatment. Compared with traditional excess sludge pretreatment technologies, theS-TE technology not only has the advantages of being economic and highly efficient,safety, easy to control and significant inactivated e ffect on pathogenic bacteria, butalso can realize the recovery of nitrogen and phosphorus and the gas reutilization.S-TE aerobic reduction process has been on industrial trial in foreign countries.However, the relevant fundamental research is less in China, the process andtechnology related to thermophiles dissolving sludge has not been reported. No matterfrom environmental protection or from new energy development, the S-TE technologyis a highly prospective in sludge reduction or improvement of the anaerobic digestionperformance..This study selected the dominant thermophilic bacteria strains AT07andinoculated into excess sludge after enriched culture to observe the changes of thesludge solubilization. At the same time, the sludge solubilization and relatedfunctional enzyme activity was investigated under different controlling factors todetermine the optimum processing conditions of thermophiles dissolving sludge, inorder to provide references for practical application.This study was carried out from the following three parts1) Effects of different dosage （0.02g/g DS,0.1g/g DS,0.2g/g DS） ofsurfactants （SDBS） on the enzyme activity in thermophilic digestion system ofexcess sludge. Drawing conclusions that:0.02g/g DS was the best dosage of SDBS inthe experiments, the enzyme activity decreased when the dosage of SDBS increased.And the concentration of soluble carbohydrate and protein reached to the highest,sludge was dissolved best when the dosage was0.02g/g DS. 2) Changes of the enzyme activity and the sludge dissolving process inthermophilic digestion system of excess sludge under different initial pH conditions（pH=4.0、6.0、7.0、8.0、10.0）. Arriving at a conclusion: In a neutral condition, theenzyme activity in thermophilic digestion system of excess sludge was the highest,the extracellular enzyme which was secreted by thermophilic bacteria has the highestactivity, and soluble carbohydrates, protein concentration reached to the highest, thesludge was completely dissolved, VSS and TSS removal efficiency was also higherunder this pH condition.3) Studies on changes of enzyme activity and sludge dissolving process inthermophilic digestion system of excess sludge at different temperatures （55℃、60℃、65℃）. Thus concluding that: The activity of amylase and protease wascomparatively higher at60℃and a little lower at55and65℃. And the solubility ofSCOD was higher at60℃, VSS and TSS removal efficiency was also higher at60℃.