Abstract: A process for achieving the partial dewatering of an organic sludge by isolating a batch of the sludge, acid adjusting its pH into a range from 3 to 5, and adding an oxidizing reagent in the presence of the acid in sufficient quantity so that within one-half hour the cellular structure of the sludge has been partially broken down and enough occluded water released therefrom to increase the pH by at least one, while at the same time changing the color of the sludge to a light tan and deodorizing it and killing the pathogens therein, the sludge and other solids settling down below the supernatant liquid with a clear line of demarcation therebetween.

Abstract: A process for the recovery of selected metal values from silica containing sludges including incineration of the sludge to degrade organic components, followed by acid leaching of the ash, followed by hydrometallurgical recovery of metal values from the remaining solid and liquid residues, wherein the incineration step is carried out at a temperature below the slagging temperature of silicates, whereby to avoid the occluding of metal values in glass matrices which are not attacked by subsequent acid leaching and hydrometallurgical steps.

Abstract: The method of safely disposing of sludge containing metal values capable of displaying toxic ecological properties including the steps of deriving from an organic or inorganic sludge an intermediate product such as a dewatered sludge or an incinerated ash, and adding this intermediate product to a metal smelting step of a type producing a slag such that most of the metal values become encapsulated in the slag, although some precious metal values may be recovered with the metal being smelted, and may be subsequently separated therefrom by appropriate metal winning steps, the sludge product bringing to the smelting process certain additives needed therein such as silica and phosphates for the slag, alumina and magnesium to lower the viscosity of the molten slag, and organic matter serving as reducing agents.

Abstract: A process for the recovery of selected metal values from silica containing sludges including incineration of the sludge to degrade organic components, followed by acid leaching of the ash, followed by hydrometallurgical recovery of metal values from the remaining solid and liquid residues, wherein prior to incineration of the sludge a quantity of soluble sodium and/or potassium salts are mixed with the sludge, the quantity being in excess by weight of the silica content of the sludge, and then the incineration step is carried out on this mixture so that silicates which form during such incineration are predominantly soluble in water and in the leaching acid, whereby to avoid the occluding of metal values in insoluble glass matrices which would not be attacked by subsequent acid leaching and hydrometallurgical steps.