Abstract: Desludging device for a portion of the total volume of a liquid that contains suspended solids and/or can form sludge, arranged in a tank for the total volume of the liquid in such a way that at least a part of said desludging device including its floor is immersed in the total volume, wherein said desludging device has an inlet opening located above said floor through which a portion of the liquid can enter the desludging device, as well as a discharge device beginning above said floor, in the form of an exit pipe, a channel, an overflow weir or at least an opening in the wall, through which the liquid can be removed from the desludging device, and wherein said floor of the desludging device has at least one outlet opening through which sludge that has settled in said desludging device can be returned to the total volume of the liquid or passed to another settling device for concentrating the sludge. Preferably the settled sludge is recycled to the total volume through a Venturi-type nozzle.