Research On Extraction Of Excess Sludge Protein By Biological Enzymatic Method

Excess sludge is an inevitable by-product in wastewater.How to deal with the excess sludge became one of the most crucial issues of disposal treatments.There are a large amount of extracellular polymeric substances?short called EPS?in sludge,which is one of the key factors affecting sludge treatment.EPS has important influence on sludge dewatering,flocculation and sedimentation,etc.Excess sludge contains a lot of poisonous and harmful substances and the secondary pollution to environment directly caused by emissions.Excess sludge must be properly handled before discharged,in order to achieve the standard of Recycling,reduction,innocuity and stabilization.The article mainly aims at discussing the influence of SDS or Hydrogen peroxide combined with enzyme to hydrolysis sludge by preliminary studied and discussed.In the paper,study the effect of surfactant type on the enzymatic extraction of protein and found that SDS is the best.When treated at the dosage of 0.20g/g and treatment time=2h,extraction rate of protein in sludge reached highest level.It was founded that compound enzyme is better than single enzyme,the optimum concentration of NaCl is 1.2%?w/v?,the best compound enzyme ratio for alkaline protease: amylase = 3:1,and the best enzyme concentration is 0.06 g/g.In the optimization of SDS combined with enzyme was founded that: extraction rate of protein was increased with the pretreatment of alkaline proteinase with pH= 8 phosphate buffer whose volume is 20 ml.The optimal solid liquid ratio is 1:4.5.Hydrogen peroxide oxides the extracellular polymeric substances in sludge which makes protein releasing easily.Based on the tests,it is the best condition of reaction that dosage of hydrogen peroxide is 5ml/40ml?v/v?,reaction time is 1.5h.It is discovered that Cu²⁺ or Fe²⁺ is the best catalyst,concentration is 0.1 %?w/v?and reaction time is 1.5h.Besides,during the reaction,the pH keeps declining,which means the reaction produces H+.PH has a significant influence on protein dissolving,while the best condition of dissolving is in 50 oCand pH is 8.It was founded that compound enzyme is better than single enzyme,the best compound enzyme ratio for alkaline protease: amylase = 2:1 and the best enzyme concentration is 0.06g/g.It was founded that: a small amount of protein extraction will be increased with the pretreatment of alkaline proteinase with pH= 8 phosphate buffer,but the difference of dosage is not obvious.To sum up,it can effectively extract protein in the sludge by SDS or Hydrogen peroxide combined with enzyme to hydrolysis sludge,a kind of green protection technology.