Bioleaching Role In Improving Dehydration Property Of Municipal Sewage Sludge And Solubilization Of Sludge-born Copper

Bioleaching has become an attractive and cost-effective approach for municipal sewage sludge treatment by which sludge-born heavy metals can be removed and pathogens be eliminated.So far,many factors affecting the bioleaching of municipal sewage sludge and the possible mechanism of heavy metals removal have been widely exploited.But few information on bioleaching role in improving dehydration property of municipal sewage sludge is available.Therefore,the purpose of the present study is to investigate the effect and of different bioleahcing treatments on sludge dehydration property and its mechanism.In addition,some additive agents have been screened out for improving the solubility of sludge-born Cu by bioleaching.After bioleaching with complex substrates of S⁰ and Fe²⁺,the centrifugal dehydration at 4000 r.min^-1 of municipal sludge reached to 74.4%from 60%;the specific resistance was reduced by 4.6 times from 1.82×10¹³ m.kg^-1 to 0.38×10¹² m.kg^-1;and the coefficient of compressibility decreased from 0.98 to 0.58.The results indicated that the decrease of absolute value of Zeta potential and the amount of particles in 20～60μm may be important factors facilitating of municipal sewage sludge.The research indicated that Fe²⁺ is the key factor that significantly effect the dehydration property and the solubilization of sludge-born Cu.Results showed that bioleahcing with mixing substrates of 3 g.L^-1S⁰ and 2g.L^-1Fe²⁺ could significantly improve the dehydration property and the solubilization of sludge-born Cu,the specific resistance reduced from 1.3×10¹³m.Kg^-1 to 1.0×10¹²m.Kg^-1,could be dehydrated directly by pressure;the solubilization rate of sludge-born Cu raised to approximately 100%,inhanced than 88%of non-iron treatment.In this paper,based on the bio-catalysis and oxidation technology,bio-polymeric ferric sulfat（BPFS） wasprepared.And the mechanism of bioleaching role improving dehydration property of sludg were explored by adding BPFS to municipal sewage sludge.The quality parameters of BPFS are similar or come up to the standard of the commercial PFS,and could reduce capillary suction time（CST） of sewage sludge from 45.4S to 16.7S,debase the concentration of SS from 214.4 mg.L^-1 to 25.4 mg.L^-1,complex using with PAM could reduce the CST of bileached acidulated sludge from 172.2S to 8.0S.Results indicated that besides production of BPFS, changing of sludge particles structure mabe an important factors facilitating of municipal sewage sludge.Otherwise,some accelerants have been screened out for improveing the solubility of sludge-born Cu in bioleaching.The results indicatied that accelerant R could promote descending of pH and solubilizing of sludge-born Cu in bieleaching. The pH of R-treatment could reduce to 1.9,but the control treatment just reduce to 2.1; solubilization rate of sludge-born Cu could reach to 96%,while the control treatment just reach to 88%.