Abstract: A pair of rollers define between them a narrow gap which is supplied with sludge to be treated. The sludge is conveyed by one of the pair of rollers to a third roller in contact with the conveying roller. The third roller is spaced a short distance from a rotating drum carrier to which is applied a thin film of the sludge. The sludge is applied to the carrier by the formation of a sludge bulge, which is an accumulation of sludge, in the area defined by the carrier, the third roller, and the conveying roller. The drum carrier picks up the sludge from the sludge bulge forming a film of sludge whose thickness is limited by the spacing of the third roller from the carrier.

Abstract: Sludge containing metal hydroxide is first subject to a separation treatment where solid particles are removed, and then dewatered to obtain a greater concentration of the metal hydroxide. The dewatered sludge attains a thixotropic character whereupon it is applied to a carrier in a film-like manner. The film is heated and then sintered so as to achieve a metal oxide that is harmless and easily handable. The separation and dewatering steps of the process are carried out in a first apparatus having a suction drum surrounded by a filtering cloth that removes the water contained in the sludge and transfers it to a second apparatus having a rotating carrier for receiving on the circumference thereof the metal hydroxide in a film form, whereupon the film is heated during rotation of the carrier and sent to a sintering apparatus for conversion to a metal oxide in a granular or powder form.