Abstract: Apparatus for injection of compressed air into a liquid such as waste water comprises a tubular basic body surrounded by a flexible, perforated membrane through which compressed air is supplied through radial openings in the basic body to be dispersed by the perforated membrane as fine bubbles into the liquid. The basic body is connected to a compressed air supply pipe through a hollow connecting body that supports the basic body and supplies compressed air to radial openings in the basic body. In one embodiment, air-conducting passageways are arranged concentrically about the hollow connecting body. The hollow connecting body provides a flooding zone in communication with the tubular basic body and sealed from the air-conducting passageways. Liquid flows therethrough to avoid dead zones of untreated liquid. The common flooding zone provides a floodable volume relative to a non-floodable volume of greater than 1.3.

Abstract: An apparatus for injecting compressed air into a liquid comprises a tubular basic body such as a pipe that is surrounded by a perforated membrane through which air is distributed into wastewater and is connected to the nipple of a compressed air supply through a hollow and cylindrical member that transfers compressed air to the space between the membrane and the tubular basic body and also has a passageway for wastewater so that wastewater can flow through the tubular basic body, thereby avoiding stagnant areas of untreated wastewater.

Abstract: A machine for intercepting solid constitutents in a liquid stream, such as sewage, has a frame which carries a downwardly sloping screen positionable in and across the stream so that the liquid flows through but the outer side of the upwardly and forwardly sloping screen intercepts solid constituents. The screen has a stationary grate with parallel grate bars extending from the lower to the upper end of the screen, and a mobile grate with parallel grate bars which alternate with the grate bars of the stationary grate. The mobile grate is repeatedly movable forwardly of the stationary grate to lift off the stationary grate bars those solid constitutents which were intercepted by the two sets of grate bars, and the mobile grate is then moved upwardly to raise the lifted solid constituents along the outer side of the stationary grate prior to redepositing the lifted constituents on the stationary grate.