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 activation plant for the treatment of waste water by the activated sludge method is disclosed wherein the plant has an outer, annular activation tank, a concentric, inner, funnel shaped secondary sedimentation tank, and a rotating aeration bridge rotating about the central axis. The return sludge, excess sludge, and floating sludge chambers, and the associated pumps, are provided in a central shaft that is the central axis for the concentric tanks. The floating sludge chamber is supplied by an annular trough circumscribing the central shaft. Clean water is removed through a conduit in the central shaft. The central shaft, chambers, and aeration bridge are supported by at least three rectangular tubes that are mounted on the wall of the secondary sedimentation tank and extend radially from the conduit for clean water in the central shaft. The rectangular tubes provide a flow space for clean water from the activation plant and are connected to outlet troughs for collecting the clean water.

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.