Abstract: A sedimentation tank for separating activated sludge from a suspension of activated sludge and sewage water, with an intake (11) for the suspension, an outlet (3) for the activated sludge at the conical bottom, and a discharge (4) at the top for the sewage water that the activated sludge has been eliminated from. A pipe (7) that is open at the top and closed at the bottom by a floor (9) is accommodated at the center of the tank and an inlet (10) that communicates with the intake opens into the pipe in the vicinity of the floor. The central pipe extends above the surface (20) of the liquid in the tank, which is dictated by how much is leaving, is loosely surrounded by another pipe (8) that extends above and below the surface of the liquid, and accommodates an agitator (12) with a speed that can be set to shape the suspension at the top of the pipe into a paraboloid (21) of rotation, which extends to the edge and from which the suspension spills over the edge.

Abstract: An arrangement for the destruction of foam building up on a sewage surface in form of activated sludge, in which a reaction vessel holds the suspended foam. The reaction vessel has perforated plates which may be raised and lowered. The reaction vessel is furthermore provided with an inlet pipe connection for untreated sewage, and a discharge pipe for the treated suspension. The reaction vessel is closed off at its upper side by a plate member which has at least one flow-through opening. A nozzle located within an enclosure, is connected to this flow-through opening. The nozzle has a lower wall and an upper wall disposed at an acute angle relative to one another. The lower wall and the upper wall of nozzle, furthermore, have adjacent edges forming an outlet opening of the nozzles. One of the walls of the nozzle is pivotably movable relative to the other wall.