Study On Enhancement Of Sludge Dewaterability Based With Chemical Cell Lysis

With the rapid development of social economy and the construction of municipalservices facilities in China, the production of excess sludge also significantlyincreased as the increasement of the scale of sewage. Excess sludge has high moisturecontent, so removing the moisture in sludge can significantly reduce the sludgevolume. The composition of raw sludge is complex, and the dewaterability is poor, sohow to enhance sludge dewaterability and achieve more efficient dehydration is a verypractical significance of the research subject.Based with chemical cell lysis, this study respectively investigated the effect onsludge dewaterability of four strong oxidants like hydrogen peroxide, Fenton reagent,potassium ferrate and sodium hypochlorite, and finally determined that hydrogenperoxide was the best antioxidant for sludge conditioning through economic andtechnical comparison. Through the orthogonal test, it was found that hydrogenperoxide dosing quantity, initial pH and concentration of sludge had a greaterinfluence on dewaterability, and the impact of conditioning time and temperature wasmuch smaller when using hydrogen peroxide to condition sludge. The optimalcondition parameters for sludge conditioning were determined as follows: hydrogenperoxide dosing was2mL/L, initial pH and concentration of sludge were3and12000mg/L respectively, conditioning temperature range were10~30℃, conditioningtime was60minutes. Under the optimal conditions, dewatering level and velocityincreased by12.40%and64.25%respectively compared to the control sample.Thisstudy also investigated the impact of pH callback on the sludge dewaterability whenusing hydrogen peroxide to condition sludge, and eventually determined usingcalcium oxide raise pH to6. In this way, dewatering level and velocity increased by11.6%and54.49%respectively compared to the control sample.To further analyze the mechanism of hydrogen peroxide enhancing the sludgedewaterability, this study investigated the effect of lysis effect, sludge floc structure,content and composition of the EPS on sludge dewateability. The results showed thatthere was a elationship between hydrogen peroxide lysis effect and sludgedewateability, and in the same concentration of sludge, the better lysis effect, thebetter dewateability. After sludge was conditioned by hydrogen peroxide, loose sludgeflocs structure was improved and became dense, the average value of sludgetwo-dimensional fractal dimensions (D2) increased from1.23to1.35compared to the control sample.The experimental results showed that there was a relationship betweensludge flocs structure and dewateability, and the more dense and the bigger D2, thebetter dewateability. After sludge was conditioned by hydrogen peroxide, the contentsof LB-EPS and the ratio of LB-EPS/TB-EPS significantly reduced compared to thecontrol sample, which showed that reducing the contents of LB-EPS and the ratio ofLB-EPS/TB-EPS was beneficial to enhance sludge dewaterability.