A plant and method for controlling such a plant suitable for treatment of waste water. The plant includes a basin, a flow generating machine adapted to generate a liquid flow in the basin, equipment in the basin that effects the momentum of the liquid flow, and a control unit. The method includes the steps of: storing a predetermined relationship between the operational speed N of the flow generating machine and an operational parameter P from which the torque M of the flow generating machine may be derived, determining the operational speed N, determining a set value of the operational parameter P of the flow generating machine, determining a real value of the operational parameter P of the flow generating machine, and adjusting the operational speed N if the real value of the operational parameter P is different than the set value of the operational parameter P.

An apparatus and method for controlled ventilation and aeration of liquid medium includes a dome supported by a flotation device, a lower housing supported by the flotation device, the lower housing connected to the dome, wherein a sealed space is defined under the dome and above the flotation liquid, one or more orifices, the orifices configured in the dome, and an aeration apparatus positioned within the sealed space and partially submerged in the flotation liquid, wherein the aeration apparatus includes one or more parallel shafts, at least one first disc positioned axially on one of the shafts, at least one second disc positioned axially on another of the shafts, wherein the second disc is interleaved relative to the first disc, and wherein a surface of the first disc rotates in a direction opposite a surface of the second disc relative to each other resulting in a mixing area therebetween.

Disclosed is a method for managing the operation of an apparatus for injecting oxygen into a purification basin. The oxygen notably being used by the biomass present in the purification basin to consume the pollution present in an effluent feedstock contained in the basin. The method comprises varying a rotational speed of the shaft by using a frequency variator, wherein an applied variation in speed is between plus 15% and minus 15% of the nominal speed of the shaft.