Abstract: The invention concerns an apparatus for removing sludge accumulated on the surface of liquid from a basin, which the liquid fills and through which it flows, such as a flotation clarification basin. The apparatus (10) comprises a de-sludging chute (11), which is arranged in the basin and which functions over the entire range of level variations in the basin, or a corresponding de-sludging chute structure (11, 14), the topmost edge of which functions as a discharge edge (11a) for the sludge to be removed, and devices (12, 13) for transferring the sludge (a1, a2) from the liquid's surface (w1, w2) into the de-sludging chute (11) and further from the de-sludging chute over the discharge edge (11a) into a de-sludging basin, channel or other such and out of the clarification basin.