The Pda Used In The Preliminary Study Of Municipal Sludge Dewatering

Application of polymer flocculants for sludge dewatering has been studied in this paper. First,raw sludge 1# used in tests was collected from Sewage Treatment Plant of Eastern Nanjing and sludge 2# from Zhujia Bridge Sewage Treatment Plant of Wuhu,respectively, then the sludge samples were conditioned by using cationic PAM(CPAM),including laboratorial products PDA,anionic PAM(APAM) and nonionic PAM(NPAM) to investigate the effects of flocculant properties and sludge characteristics on sludge dewatering.The filtrative dewatering ability was mainly valued by the size of flocculate and water-containing rate of filter cake,the water quality of the supernatant was valued by COD_Cr,NH₃-N and orthophosphate content.Turbidiity,transmission and Zeta potential of the supernatant were detected and used as supplementary elements for theoretical explanation and result evaluation.The results showed that for sludge 1#,of which the original water content and organic substance content were much higher than that of sludge 2#,laboratorial products PDA33 with cationicity of 30%and intrinsic viscosity of 11.5 dL·g^-1,PDA32 with cationicity of 30%and intrinsic viscosity of 10.0 dL·g^-1,and commercial product c-625p with cationicity of 25%and intrinsic viscosity of 12.5 dL·g^-1 had excellent dewatering ability at the dosage of 60 mg·L^-1, the correspongding water-containing rates of filter cakes after dewater reached 81.78%, 82.90%and 84.31%,respectively.For sludge 2#,commercial products c-635p with cationicity of 35%and intrinsic viscosity of 13.1 dL·g^-1,Zetag7650 with cationic of 25%and intrinsic viscosity of 13.1 dL·g^-1,and laboratorial product PDA33 just mentioned performed excellent dewatering ability at the dosage of 30 mg·L^-1,30 mg·L^-1 and 40 mg·L^-1,respectively, the correspongding water-containing rates of filter cakes after dewater reached 74.14%, 74.75%and 75.93%,respectively.The turbidity,COD_Cr,NH₃-N content and orthophosphate content in the supernatant all decreased first and then increased as the increasing flocculant dosages.In contrary,the transmission of the supernatant increased first and then decreased.Zeta potential of the supernatant always increased from negative to positive after flocculated by CPAM.At the optimal dosage,the values of COD_Cr,NH₃-N and orthophosphate content were among the range of 33.68～81.40 mg·L^-1,14.84～17.84 mg·L^-1,8.76～12.76 mg·L^-1 for sludge 1#, respectively,and for sludge 2# among the range of 27.35～43.76 mg·L^-1,9.47～14.31 mg·L^-1,1.34～3.68 mg·L^-1.The experimental results indicated that for the two sludge samples,the CPAM had significant effect on sludge dewatering,while the NPAM and APAM were not suitable.And for forming optimum size of flocculate,CPAM with higher intrinsic viscosity had their superiorities better than the others when their cationicities were same.At the same time,for CPAM with the approximate intrinsic viscosity values,a cationicity in a proper range was required to achieve a best dewartering effect.It's proved that laboratorial products PDA had close ability to commercial products in sludge dewatering,and the results obtained can be used to provide theoretical support for further development of PDA,also for industrial production and application.Furthermore,the COD_Cr value,NH₃-N content and orthophosphate content of the supernatant met the requirements of the emission control regulations issued by the government.As a result,the supernatant can be recycled or discharged directly.