Effect Of Combined Conditioning Based On Sulfate Radical On Sludge Dewatering Performance

The production of surplus sludge mainly comes from the sewage treatment plant,which is the back end of the wastewater treatment.Sludge has high hydrophilicity and special floe structure.After conventional chemical conditioning and mechanical dehydration,the moisture content of sludge is still as high as 80%or more,and it is difficult to store,transport and dispose of sludge.Sulfate radicals can improve the dewatering performance of sludge flocs,which is mainly due to the strong oxidation of sulfate radicals,which can destroy the colloidal structure of sludge.Under normal temperature conditions,the reaction rate is slow,and the dosage of pharmaceuticals is large.The combination of different sludge conditioning methods is a hot topic in the field of sludge pretreatment in recent years.Therefore,based on the strong oxidizing ability of sulfate radicals,the paper pretreated the sludge through the joint conditioning with lime,polyaluminum chloride(PAC)and polyacrylamide(PAM)to examine the dewatering performance of the sludge.Improve the effect,obtain the optimal pretreatment parameters of joint conditioning;combine the engineering economic analysis to discuss the optimal pretreatment of sludge.The main research results obtained in the paper are as follows:1.The optimum pretreatment parameters for improving the dewatering performance of sludge were determined by advanced oxidation of sulfate radicals.Sulfate radical oxidation alone was used to pretreat the excess sludge.Through the single-factor rotation experiment,the optimal pretreatment conditions for improving the dewatering performance of the sludge were determined.After pretreatment,the moisture content of the sludge was 81%.The SRF of the sludge decreased from 6×1011s2/g to 4.78×109s2/g.The sludge capillary water absorption time was reduced from 234s to 97s,and the amount of sludge decreased.50.6%.2.The use of sulfate radical advanced oxidation and lime combined conditioning can effectively improve the dewatering performance of sludge,sludge reduction effect is obvious.From the perspective of sludge reduction effect and economic cost reduction,based on the 5%of lime dosage,the sludge was pre-treated with a sulfate radical advanced oxidation method to determine the combination of sulfate radicals and lime.The best pretreatment conditions.After combined pretreatment,the moisture content of the sludge was 74%,which was 7%lower than that by using sulfate radical oxidation alone;the SRF of the sludge was 2.2×108s2/g,which was an order of magnitude lower;the CST was 30 s.The reduction of 67 s and the sludge volume decreased by 730%.3.The effect of sulfate radical oxidization combined with PAM+PACl to improve sludge dewatering performance was discussed.(1)In order to further optimize the sludge pretreatment scheme,the sulfate radical oxidizing method and PAM are combined to regulate the sludge,and the reaction parameters are determined under normal temperature conditions.After pretreatment,the water content of the sludge was 83%,the SRT was reduced to 8.14×108m/kg,the CST was 74s,and the sludge volume was reduced by 60.6%.(2)Sludge was pretreated with Fe(?)sulfate radical oxidation and PAM+PAC.Under normal temperature conditions,single-factor optimization experiment was conducted to determine the optimal reaction time was 2h,after sulfate radical oxidation.After combined treatment with PAM+PAC1,the water content of sludge was 70%,which was 11%and 4%lower than that of sulphate radical oxidation and sulphate radical oxidation combined with lime,respectively;SRT fell to 2.02.×108m/kg;CST shortened to 30 s;sludge reduction reached 75.8%,and the final sludge volume decreased by 25.2%and 2.8%,respectively.It can be seen that pretreatment of sludge with Fe(?)sulfate radical high-grade oxidation and PAM+PAC combined conditioning method has the best effect in improving sludge dewaterability and sludge reduction.4.For in-depth mechanism analysis,the original sludge,sulfate radical and lime-conditioned sludge,sulfate radicals,and PAC and PAM-conditioned sludge were respectively examined by microscopy and Malvern particle size analyzer.:Sludge flocculation with sulphate radicals and PAC and PAM has obvious cracking effect.The structure is loose,the cell surface is uneven,and the sludge particle size is increased.The sludge is combined with flocculation and adsorption to form a larger sludge.Flocs,cells adsorb water and release water,thus improving the dehydration effect.5.Considering the cost of chemicals and the actual operation,through the engineering economic analysis,the operating costs of joint conditioning with sulfate radicals and lime and advanced oxidation of sulfate radicals + PAC+PAM were obtained,which were 28 yuan/m3 respectively.And 19 yuan/m3.It can be seen that the pretreatment of sludge with sulfate radical advanced oxidation plus PAC+PAM is economically more feasible.