Chemical detoxification of sewage sludge

摘要

A method is disclosed for the chemical detoxification of anaerobically digested organic sludge containing toxic heavy metals in insoluble form. A quantity of the sludge is transferred from a conventional anaerobic digester to an insulated reactor vessel where the sludge is mixed and aerated at a rate sufficient to raise the oxidation reduction potential of the sludge to above +300 mv. and to maintain this condition for a period of 6-12 hours during which the heavy metals are converted to their desired oxidation state. The sludge is then acidified under controlled conditions to pH 1.0-3.0 for a period of 6-12 hours to solubilize the heavy metals. Conventional dewatering techniques are used to separate the detoxified, acidic sludge and the acidic, heavy-metal-containing water. The sludge may be neutralized for safe land application, and the metals can be recovered from the water using existing conventional techniques.