Apparatus for the separation of scum from a liquid including a housing (22) incorporating two side walls in spaced relationship and a scraper wall disposed between said side walls. A rotational device (12) mounted in the housing (22) provides rotational motion about one or more horizontal axes. The rotational device (12) includes one or more paddles (13-16) which extend outwardly with respect to the rotation axis forming a substantial sealing engagement with the opposed inner faces of the side walls of the housing. The scraper wall and rotational device are arranged such that when immersed in water, the paddle(s) (13-16) may be rotated to become at least partly submerged and the outer periphery(ies) engage with the scraper wall to lift a portion of the water and scum above the natural level of the water.