Mixing/aerating apparatus with an impeller

A process for mixing and aerating a liquid within a liquid body, said process using an apparatus for pumping liquid into a vertical at least partly conical housing, so as to form an upwards flow of pumped fluid into the said vertical at least partly conical housing towards an upper opening, and so as to expel said pumped fluid through said upper opening,

• in which the apparatus comprises:
• a supporting element (1);
• a top-mounted power drive (2) mounted on said supporting element (1), said top-mounted power drive (2) having a rotatable shaft (3) extending downwardly toward the liquid surface of said liquid body;
• an impeller (4) mounted on said rotatable shaft (3) for rotation therewith;
• an at least partly conical housing (6), said housing comprising at least an upper portion (6A) ending with an upper free edge, and a lower portion (6B) ending with a lower free edge, whereby said at least partly conical housing (6) is attached to an element selected from the group consisting of the supporting element (1) and a part attached to the said supporting element (1), whereby said at least partly conical housing (6) defines an inner open channel (6C) between an upper opening and a lower opening, said inner open channel of the at least partly conical housing (6) having substantially a central axis, whereby defining at least a first substantially circular cross section perpendicular to said central axis adjacent to the upper opening and a second substantially circular cross section perpendicular to said central axis of symmetry adjacent to the lower opening, said second substantially circular cross section being greater than the said first substantially circular cross section;
• whereby the impeller (4) has at least a lower portion (4B) extending at least partly within the at least partly conical housing (6), and whereby said impeller (4) is adapted so that when driven into rotation by driving into rotation the said rotatable shaft (3), the impeller (4) generates (a) a pumping of liquid within the at least partly conical housing (6) through its lower opening, whereby generating pumped liquid to flow through said at least partly conical housing (6) from the lower opening towards the upper opening, and (b) to expel said pumped liquid through the upper opening of the at least partly conical housing (6), and
• whereby the upper free edge of the upper portion (6A) of the at least partly conical housing (6) is a corrugated free upper edge defining peaks and valleys, whereby two successive peaks are separated by a valley, and whereby the distance measured parallel to the central axis of the at least partly conical housing (6) between the top of a peak and the bottom of a valley is greater than or equal to 2 cm,
• the said process being characterised in that pumped liquid is expelled from the apparatus in accordance to at least a series of first radial liquid expelling zones and a series of second radial liquid expelling zones, whereby a second radial liquid expelling zone is located between two successive first radial liquid expelling zones, while a first radial liquid expelling zone is located between two successive second radial liquid expelling zones,
• whereby the first radial liquid expelling zones are each characterised by at least a first parameter selected from the group consisting of liquid expelling speed, liquid expelling rate per angular section unit, and combination thereof, while the second radial liquid expelling zones are each characterised by at least a first parameter selected from the group consisting of liquid expelling speed, liquid expelling rate per angular section unit, and
• wherein the first parameter of the first radial liquid expelling zones differs by at least 10% from the second parameter of the second radial liquid expelling zones.