Abstract: An apparatus for selectively aerating or anaerobically mixing a liquid in a container includes a hollow, star-shaped, multi-vaned rotor (6) arranged in the bottom region of the container (1) for rotation about a vertical axis. The hollow interior of the rotor at one of the two opposite faces thereof is in communication with a gas feed line (15), and each of the vanes (10) at its trailing flank (11), as viewed in the direction of rotation of the rotor, is provided with a respective gas exit opening (12). The inter-vane spaces of the rotor are open at one of its two opposite faces for admitting liquid from the container into those spaces. The rotor is surrounded by a stator (7) providing a plurality of circumferentially spaced flow channels (9) for receiving and guiding away either liquid with admixed gas when gas flows through the gas feed line or liquid without admixed gas when no gas flows through the gas feed line.

Abstract: An apparatus for aerating liquids includes a gas- and liquid-feeding rotor (6) and a surrounding stator (7) arranged in the bottom region of a container (2). The rotor (6) is mounted for rotation about a vertical axis, and the stator (7) comprises two vertically spaced, horizontally parallel, annular plates (8, 8a) defining a central rotor-accommodating cavity (7b) and includes a plurality of circumferentially spaced guide channels (9) located between the plates and arranged non-radially in the direction of rotation of the rotor (6) for conducting the gas-liquid mixture from the stator cavity (7b) to the outer perimeter of the stator (7).