Abstract: Disclosed is an apparatus for the intermittent aeration of sewage or sewage-activated sludge mixtures. The apparatus is adapted to be disposed below water level and consists of a horizontal air distributor in the form of a pipe jacket closed tightly at both ends except for an aperture for the air supply, and which, in the area of its two opposite lateral longitudinal edges, includes apertures for the passage of air. The apparatus further includes an elastic air distributing foil covering the apertures for the passage of air and the upper portion of the pipe jacket located between the apertures. The foil is provided with air escape openings which are opened by the air supply to the pipe jacket and closed in case of interruption of the air supply by being sealed against the pipe jacket outside the area of the air passage openings.

Abstract: Apparatus for biologically treating sewage in an elongated circulation tank having a central partition extending along the longitudinal axis thereof thereby dividing the tank into two parallel flow channels connected together at opposite ends, aerators rotating about a perpendicular axis located along said longitudinal axis so that the sewage may be forced into a circulating flow about the perpendicular axis and about the partition. The circulating flow about said perpendicular axis thereby being decelerated and the sewage circulating about the partition being guided to and away from the rotating aerators with the full cross-section of the flow channels.