Mixing and aeration device and a method to mix and aerate

Device mixing and aeration for mixing and aerating a liquid, in particular a body of water (2) in a tank (1) of an installation for treatment of liquids, in particular an installation for water treatment, a team of mixing and aeration (3) with a housing (6) including a first housing part (7) and a second housing part (8), an electric motor (11) disposed in the first housing part (7), a shaft (12) extending through the first and second housing part at a first end of shaft (14) is driven, rotatable about an axis of rotation (a), by the electric motor (11), a hub (34 ) connected to the second shaft end (21) opposite the first end of shaft (14), at least two blades (42) arranged in the hub (34) and a supply tube of air (46) connected to the housing ( 6), the first housing part (7) adjacent to a junction point (9) of the first (7) and second housing part (8) a connecting device (44) with an opening (45) extending radially to the rotation axis (A), the tube being air supply (46) connected to the connection device (44), wherein the second housing part (8), opposite the first housing part (7) configured a cavity (40) through which extends out of the second housing part (8) the shaft (12) and / or the hub (34) connected to the shaft (12) and a hub body (41) dome shaped fixed on the hub side (34) opposite the shaft (12) thereto, characterized in that the body hub (41) shaped hollow dome-shaped is fixed to the hub side (34) opposite the shaft (12) back to the cavity (40) of the second housing part (8).