A floating equipment, for injection of a gas into liquid effluents or waste water, and more particularly of a gas rich in oxygen into a basin from the surface, comprising the following elements: a driving device, intended to be disposed over the liquid, provided with a vertical output shaft (8), equipped at its end with a propeller (6) immersed in the liquid a pre-mixing device (5) comprising an injection device (7) positioned above or below a mobile aerator (9) with inclined blades, the propeller being situated at the end of the shaft, under the pre-mixing reactor.