Influence Of Extracellular Polymeric Substance On Enzyme Hydrolysis Of Sludge Under Anaerobic Condition

Due to the accelerated process of urbanization, wastewater treatment systems arebecoming more popular. With the improvement of treatment efficiency, the totalamount of excess sludge will also increase, and the resulting secondary pollution cannot be ignored. Anaerobic digestion can reduce the amount of sludge to some extent.And the technology can be harmless and resources, more economical and practical.However, the reaction has a long time and a low degree of hydrolysis. Hydrolysis byenzyme can enhance efficiency of excess sludge hydrolysis to a greater extent. Thetechnology will cut down digesting time, easy to control, and its products areharmless to environment. So it has a broad application prospect. In order to furtherunderstand the effect and mechanism of hydrolysis by various enzyme, and alsoincrease the efficiency of enzyme hydrolysis, the article mainly aims at explaining theinfluence of extracellular polymeric substances （EPS） to enzyme hydrolysis sludge bypreliminary studied and discussed.The effect of extracellular polymeric substance on the enzymatic solubilisationof sludge and the changes of chemical components was investigated. Sludgesolubilization with and without EPS was studied in the enzymatic system, and in thenormal system without enzyme addition, respectively. The result indicated that onlyEPS could be hydrolyzed when the enzyme addition less than20mg/g, while the celllysis occurred significantly with the doses of enzymes increasing. Treatment withlysozyme for the original sludge was proved to have a higher hydrolysis efficiency,and the SCOD/TCOD rate reached up to28.14%. And at the enzyme dosage of60mg/g, the VSS removal rate increased to51.66%and the concentration of DNAattained68.34mg/g （calculated by VSS） after48h reaction, which were29.01%and59.63mg/g higher than the control test, respectively, and were24.86%and53.39mg/g higher than that with EPS removed in advance, respectively. Meanwhile,NH₄⁺-N, P0₄^3--P and SCOD showed high dissolution efficiency, and the maximalconcentrations achieved to503mg/L,78.9mg/L and3171mg/L, respecticely. Afterremoval of extracellular polymers, higher lysis efficiency was also observed byprotease and cellulose, by which VSS reduction rate reached to49.95%and39.85%,respectively. The concentration of DNA showed a correlation coefficient of more than0.9with the concentrations of SCOD，NH₄⁺-N and P0₄^3--P. And the highest hydrolysis rate obtaind in6hours, which was about3hours earlier than the control test.Moreover, under the condition, sludge hydrolyzation could be well realized by onlysmall amount of the enzyme addtion. From the beginning to the maximum hydrolysisrate of time, sludge solubilization with and without EPS followed first-order kinetics.Treatment with protease and cellulose for the original sludge had a smaller reactionrate constant than those enzyme for sludge without EPS, while lysozyme was theopposite.