Method for treating a liquid with high-frequency acoustic waves in a device of a system comprising at least two devices for acoustic wave treatment, said devices comprising at least: - an open, elongate vessel of which the cross-section tapers progressively toward an opening at the top of the vessel, and - a piezoelectric element, said vessel being filled with a liquid, the piezoelectric element being capable of emitting waves into said liquid, said waves being focused in the vicinity of the vessel opening and exiting into a duct, characterized in that the outlets of the various ducts of the devices, said ducts having a diameter of between 4 mm and 50 mm, converge in a flow collector and in that the waves generated in each device by the piezoelectric element in the vessel and/or in the duct have a frequency greater than 100 kHz. and characterized in that the method comprises the following steps according to which: - a liquid to be treated is introduced into the vessel of said device via a flow circuit; - high-frequency acoustic waves, greater than 100 kHz, preferably greater than 200 kHz, are generated in said vessel by the piezoelectric element; - the acoustic waves propagate in the vessel and focus on a point located in the vicinity of the central portion of the vessel opening and exit into the duct; said waves allowing the liquid to be treated; and - the liquid thus treated is recovered at the outlet of the duct or at the outlet of the flow collector. - an open, elongate vessel of which the cross-section tapers progressively toward an opening at the top of the vessel, and - a piezoelectric element, said vessel being filled with a liquid, the piezoelectric element being capable of emitting waves into said liquid, said waves being focused in the vicinity of the vessel opening and exiting into a duct, characterized in that the outlets of the various ducts of the devices, said ducts having a diameter of between 4 mm and 50 mm, converge in a flow collector and in that the waves generated in each device by the piezoelectric element in the vessel and/or in the duct have a frequency greater than 100 kHz. and characterized in that the method comprises the following steps according to which: - a liquid to be treated is introduced into the vessel of said device via a flow circuit; - high-frequency acoustic waves, greater than 100 kHz, preferably greater than 200 kHz, are generated in said vessel by the piezoelectric element; - the acoustic waves propagate in the vessel and focus on a point located in the vicinity of the central portion of the vessel opening and exit into the duct; said waves allowing the liquid to be treated; and - the liquid thus treated is recovered at the outlet of the duct or at the outlet of the flow collector. - a liquid to be treated is introduced into the vessel of said device via a flow circuit; - high-frequency acoustic waves, greater than 100 kHz, preferably greater than 200 kHz, are generated in said vessel by the piezoelectric element; - the acoustic waves propagate in the vessel and focus on a point located in the vicinity of the central portion of the vessel opening and exit into the duct; said waves allowing the liquid to be treated; and - the liquid thus treated is recovered at the outlet of the duct or at the outlet of the flow collector.