Abstract: The invention concerns an apparatus for the continuous treatment of wet sludge produced in a sewage treatment plant.

Abstract: An apparatus for circulating and/or aerating a liquid, especially waste water located in a tank or basin by means of a centrifugal impeller or rotor immersed in the liquid and rotatable about a substantially vertical axis. The centrifugal impeller is equipped with a multiplicity of at least approximately radially extending liquid conveying channels. The liquid conveying channels at least at the region of their outlet openings or mouths are curved in such a manner in a vertical plane and/or provided at the outlet openings in such a manner with flow deflection surfaces that the liquid emanating from the conveying channels flows at an angle of at least 5.degree. relative to a substantially horizontal plane towards the side of the impeller provided with an inlet opening.

Abstract: An improved, compact biological sewage treatment plant comprised of a series of serially connected treatment tanks of arcuate shape when viewed in top plan view, joined operatively together essentially in an end-to-end circumferential ring-like manner, forming a central space adapted to house additional sludge dehydrating and auxiliary treatment apparatus and equipment for control and maintainance of the plant. A particular advantageous feature includes providing additional concentrically disposed series of said treatment tanks all operatively connected to provide for selectively expandable capacity as needed, with a minimum of adverse environmental impact on the surrounding populace.

Abstract: A clarification plant has an activation tank which is provided with a surface ventilation rotor. Activated sludge from a re-clarification tank is recycled by means of a conduit connected to the re-clarification tank, an outlet aperture thereof being located in the suction zone of the rotor. The activated sludge is sucked from the conduit into the rotor. Oxygen or an oxygen mixture is added in finely divided form to the recycled activated sludge before it enters the rotor to aerate the same.

Abstract: In an installation for the biological purification of effluent at least two basins linked with each other are used. The effluent to be purified is supplied to one basin to introduce oxygen into the effluent. The effluent enriched in this manner with oxygen is supplied after an average residence time to the second basin acting as the final purification basin. The purified water is removed from the said second basin, until the activated sludge concentration in the first basin drops below a certain value, following which the direction of operation is changed, so that the second basin functions as the activated sludge basin and the first basin as the final purification basin connected in series.

Abstract: A method and apparatus for biologically treating refuse or thickened sludge to form compost utilizes a vertical cylindrical chamber havng an upper inlet aperture and a lower outlet aperture. An axial shaft located within the chamber has mounted thereon a plurality of radial arms each having a plurality of gas distributor blades. Sets of arms are spaced axially along the shaft. The chamber wall is formed in part by a plurality of hollow, cylindrical exhaust ducts concentrically arranged and extending differing distances along the chamber side. The end of each duct is flared to form an exhaust aperture which extends around the entire chamber. Material to be treated enters the chamber at the upper inlet and fills the chamber. The rotating radial arms and blades distribute a treating gas mixture to the material, which gas is exhausted by the annular exhaust apertures and exhaust ducts.

Abstract: An aerospacecraft possessing a discus shaped body equipped with at least one disc type air screw driven by a turbine by the exhaust gases of a jet engine. The disc type air screw is equipped with variable pitch blades and works in the manner of a helicopter rotor for the generation of lift.