Study On Sludge Co-conditioning By Disintegration-Reflocculation-Skeleton Building

Excess sludge is a by-product produced in municipal wastewater treatment facilities,and the treatment and disposal of excess sludge introduces significant costs to the operation of these facilities due to excess sludge's highly compressible nature,high organic content,and abundance of colloids.The study took specific resistance of filtration(SRF),moisture content of sludge cake(MC)and time to filtering(TTF)as the major investigation parameters to evaluate the sludge conditioning performance of US/NaCl disintegration,CPAM reflocculation,skeleton structure constructed by RH and to further explore the mechanism of sludge co-conditioning through studying sludge liquid phase,sludge particle and sludge filter cake.The results showed,the SRFs,MCs and TTFs of sludge were improved after conditioning by US-CPAM-RH.Besides,the porosity of sludge cakes gradually rose when the compressibility of cakes were dropping,showing the improved sludge dewatering performances.Sludge was mildly disintegrated by US,sludge matrix was disintegrated into small particle and released the water trapped in there;CPAM can flocculate small sludge particle into big sludge flocs,strengthened the sludge-water separation process;Addition of RH leaded to form a filter cake structure with high mechanical strength,pores and low compressibility.Sludge dewaterability was improved by three sludge conditioning methods.The optimal conditioning situation of US-CPAM-RH was following,US density of 0.3 W/ml,US conditioning time of 12 s,CPAM dosage of 30 mg/L,RH dosage of 50 wt.%and RH particle size of-110 mesh.In optimal condition of US-CPAM-RH,SRF dropped tol.32×108 s2/g by 90.50%reduction.MC dropped to 62.15%by 31.82%reduction.In group of NaCl-CPAM-RH co-conditioning,sludge was disintegrated by NaCl by monovalent cation exchanging effect,and trapped water was released.Through flocculation and construction from CPAM and RH,the sludge dewatering performance was improved.The optimal conditioning situation of NaCl-CPAM-RH was following,NaCl dosage of 0.25 mol/L,NaCl conditioning time of 120 min,CPAM dosage of 30 mg/L,RH dosage of 50 wt.%and RH particle size of-110 mesh.In optimal condition of NaCl-CPAM-RH co-conditioning,SRF dropped to2.14×108 s2/g by 91.23%reduction.MC dropped to 65.44%by 26.74%reduction.In order to cut the energy consumption,NaCl dosage and NaCl conditioning time in US/NaCl-CPAM-RH co-conditioning,US+NaCl-CPAM-RH co-conditioning was developed.The optimal conditioning situation of US+NaCl-CPAM-RH was following,US density of 0.3 W/ml,US conditioning time of 9 s,NaCl dosage of 0.20 mol/L,NaCl conditioning time of 100 min,CPAM dosage of 30 mg/L,RH dosage of 50 wt.%and RH particle size of-110 mesh.Under the optimal situation of co-conditioning,SRF of sludge dropped to 1.33×108 s2/gby 94.59%reduction.MC dropped to 66.48%by 25.57%reduction.This paper analysed US/NaCl-CPAM-RH sludge conditioning methods.The US disintegration had merits of high disintegration efficiency,no second contamination,no drug addition.The NaCl disintegration had advantages that low drug addition cost,recycleable,the mass and volume of skeleton builder decrease.Sludge disintegration by US-NaCl can not only bring great sludge disintegration performance,but also reduced the energy consumption of ultrasonication disintegration,the dosage of NaCl and conditioning time of NaCl.The dewaterability of sludge cakes conditioned by US+NaCl-CPAM-RH conditioning were significantly improved and heat value of sludge cakes were also increased when the CPAM dosage was dropped,reducing the pressure of following sludge processes.