Combined biological-chemical detoxification of organics

Claim 1

A combined biological-chemical method for detoxifying a slurry of sludge of the municipal sewage or industrial organic type, which sludge contains excess-waste thermophilic bacteria, biodegradable organic material, sulfur, and toxic heavy metals in insoluble form, which comprises the sequential steps of: (a) introducing a sufficient quantity of the sludge slurry into an enclosed insulated reactor vessel to fill the same to about one-half of its volume; (b) aerating the slurry with ambient air by means of a self-aspirating aerator, and simultaneously cutting foam produced thereby, thereby to effect autoheating of the slurry by the thermophilic bacteria to a temperature maintained in the thermophilic range of from about 43° C. to about 70° C., said autoheating being achieved by conservation of the metabolic heat of oxidation of the biodegradable organic material in said insulated reactor vessel; (c) retaining said autoheated slurry in said reactor for a hydraulic retention time of 3 to 8 days sufficient to destroy the pathogenic bacteria and increase the oxidation reduction potential to a level greater than +500 mv, whereby the sulfur and heavy metals are converted to a desired higher oxidation state; (d) adding to said autoheated slurry a quantity of concentrated acid in an amount sufficient to acidify said slurry to a pH value ranging from 1.0 to 3.0 for an acidification period of 6 to 12 hours sufficient to solubilize the heavy metals while maintaining said oxidation reduction potential at a level greater than zero mv, and the temperature in the thermophilic range; and (e) dewatering the acidified slurry to remove the solubilized heavy metals therefrom, thereby to produce dewatered, detoxified acidic sludge and acidic, heavy-metal-containing water.