Abstract: Waste water containing suspended biologically active sludge and circulating in an endless path in a vessel is aerated by withdrawing a stream of the water and recycling it to the vessel in the form of a plurality of downwardly directed jets which penetrate the water surface and thereby entrain air in the water. The jets are directed onto the water surface at an angle of less than 60.degree. and the horizontal component of the motion of the jets is substantially parallel to the recirculation path of the main body of water at the point of impact. The jets are divided regularly over the water surface of the vessel and the energy being imparted to the total number of water jets being at least 2 W per m.sup.3 of water contained in the vessel.

Abstract: A method and apparatus for aerating a body of waste water in which air is supplied to a bell chamber disposed below the surface of the water and in which a stream of water is withdrawn from the body and jetted through the air space in the chamber so as to penetrate the water residing below the chamber and thereby drive air into the water.

Abstract: A process and apparatus for recovering useable materials from discarded scrap material, such as junked automobiles, is disclosed in which non-ferrous metals are separated from non-metals in a hydrocyclone using water as the aqueous separating medium. A particulate scrap/water suspension is injected into the cylindrical area of the hydrocyclone and a predominently non-metal-containing portion is removed from an overflow area of the cyclone while the non-ferrous metal containing portion is removed from the apex area of the cyclone. If required, the scrap material is preferably pulverized prior to treatment and is subjected to a ferrometallic separation operation if such metals are present.