Installation for the mixing of two fluid phases by mechanical stirring, notably for the treatment of water by transfer of oxidizing gas, and use of such an installation

An installation for the mixing of a liquid, such as stored water, waste water and/or filtered water, with a treatment gas, wherein:

• (a) said mixing installation comprises a vessel having an axis of symmetry and said installation further including means defining an inner concentric central chamber having an open top and open bottom within said vessel and fluid flow communication with said vessel through said open top and open bottom, and defining a peripheral chamber outside of said central chamber means and inside said vessel and a central chamber inside of said central chamber means, wherein the central chamber is provided with:
• (i) at least two turbines rotatably mounted one above the other, the rotational axis of which is said axis of symmetry of the vessel;
• (ii) counter-blades comprising plates fixed to an inner wall of the central chamber means according to a symmetrical distribution, so as to counter rotation of fluid induced by blades of the turbines, said counter-blades being placed in an axially alternating position with the turbines;
• said blades and said counter-blades comprising gratings of expanded metal having straps which give the blades and the counter-blades a transparency that is variable according to the incidence of the flow, of the liquid, during operation;
• and
• (iii) means to add a treatment gas to the central chamber for mixing therein with the liquid.