Effects Of Three Kinds Of Oxidations On The Performance Of Dewatering And Removing Heavy Metals In Municipal Sludge

With the rapid increase of sludge production,the pressure on the environment and the city is increasing.The sludge with high water content and the composition is complex,which contains heavy metals,refractory organic matter is limited to the treatment and disposal of sludge.The objective of the study was to investigate the effects of the strong oxidizing-Fenton,potassium persulfate and calcium peroxide at application in municipal sludge which explore the application of the effect of dewatering performance,heavy metal removal and the ability of transformation in sludge before and after treatment.In order to provide a theoretical reference,which for the study of the advanced oxidation technology treatment of sludge.Based on the experimental results,the conditions were initial pH value of 2,reaction time of 1h,temperature of 25?,the[Fe²⁺]:[H₂O₂]ratio of 9:1,K₂S₂O₈ dosage of 9g/L,CaO₂ dosage of 1.0%,The value of moisture content of the sludge cake decreased from99.08%to 76.1%,74.7%and 66.5%,respectively.The sludge specific resistance decreased by 29.8%,23.2%and 62.7%,respectively,and it demonstrated that these reagent could effectively improve the dewatering performance of sludge.The value of COD,TN in the sludge supernatant increased to 149mg/L,216.3mg/L,163mg/L and 14.3mg/L,25.6mg/L,13.2mg/L from 15.2mg/L and 6.03 mg/L,respectively.The value of TP was changed from 8.15mg/L to 13.0mg/L,12.8mg/L,1.8mg/L,respectively.After adding Fenton and K₂S₂O₈ of the sludge,TSS can be removed by 11.5%and 10.4%,while adding CaO₂ will increase the total amount of TSS.However,the efficiency of removal could increase with in suitable pH value.The removal rates of tested heavy metals increased with increasing oxidant concentration.The heavy metals Pb,Zn,Cu,Cd after treatment with Fenton and K₂S₂O₈ can get good removal effect.When the dosage reached an optimum level,the removal rate of heavy metals has been basically stable.Among the[Fe²⁺]:[H₂O₂]ratio of 9:1 in removing heavy metal from sewage sludge,with the removal rate of 50.6%for Pb and 85.8%for Zn and 91.1%for Cu and 91.7%for Cd after reaction.When the K₂S₂O₈ dosage of 9g/L,Pb,Zn,Cu,Cd removal rate were reached 63.9%,87.1%,86.4%,84.3%respectively.But CaO₂ is relatively poor,Cd only be removed by 10.3%.After Fenton and K₂S₂O₈ oxidation,the heavy metals in the sludge were transferred to the supernatant and it was treated with different concentrations of calcium oxide,the supernatant of pH value has increased.The content of heavy metals Pb,Zn,Cu and Cd in supernatant decreased obviously,and the TN and TP in the liquid could be improved obviously.It has recoverd resource of supernatant.