Abstract: A liquid treatment apparatus includes a sensor which is sensitive to a variation in gas pressure and which generates signals indicative of sensed pressures. The apparatus also included a casing divided into a first compartment and a second compartment by a flexible membrane, the first compartment having at least one orifice for the introduction of the liquid, and the second compartment being connectable in a leaktight manner to the pressure sensor. A pump is provided to vary a quantity of gas in the second compartment, and a controller is provided to regulate the pump as a function of variations in pressure generated in the second compartment. The controller is configured to receive signals from the sensor and to cause, through the pump, at least two successive pressure variations, having opposite directions, in the second compartment so as to adjust said position of the membrane between a wall of the casing bounding the first compartment and a wall of the casing bounding the second compartment.