Patent ID: 6855256
Filing Date: 2005-02-15
Classification: C02F

Abstract:
1. Hybrid chemical and biological process for decontamination of sewage sludge containing heavy metals and pathogenic microorganisms, comprising the following steps: a) treating the sludge with an acidic leaching solution to acidity the sludge to a pH between 2.0 and 3.0 so as to dissolve the majority of the heavy metals and to destroy the majority of the pathogenic microorganisms, the leaching solution containing an oxidizing agent in a quantity sufficient to maintain an oxidation reduction potential higher than +400 mV; b) flocculating the sludge treated in step (a) c) effecting a solid-liquid separation to provide a solid fraction comprising decontaminated and dehydrated acid sludge and a liquid fraction containing the heavy metals; d) neutralizing the decontaminated acid sludge; and e) recovering the decontaminated and neutralized sludge, the recovered sludge having a fertilizing element content which is defined as N