Patent ID: 6066256
Filing Date: 2000-05-23
Classification: C02F,Y10S

Abstract:
A continuous process for the biological solubilization of heavy metals in sewage sludge utilizing indigenous sulphur oxidizing bacteria and elemental sulphur as an energy source, which results in a treated sludge possessing a minimal residual sulphur, wherein said process comprises the steps of:(i) enriching the said acidophilic sulphur-oxidizing bacteria in a biological reactor by mixing metal-laden sludge and powdered elemental sulphur and incubating the mixture at or above ambient temperature under aerobic conditions until a pH<3 and an oxidation-reduction potential (ORP) between +400 to +600 mV is obtained;(ii) continuously feeding a mixture of fresh metal-laden sludge and powdered elemental sulphur to this reactor;(iii) maintaining aerobic conditions and operating the biological reactor to allow the said bacteria to achieve a steady state characterized by a pH<3 and an oxidation-reduction potential (ORP) ranging from approximately +400 to 600 mV;(iv) optimizing sulphur addition to achieve minimal residual sulphur in the biosolids; and(v) continuously recovering the mixture from the reactor for further processing.