A sludge removal apparatus includes a sludge removal head (10) with a sludge suction duct and an water supply duct with open end portions alongside each other, and a filter (32) adjacent to the open ends of the suction duct (36) and the water supply duct (38) so that the sludge is extracted through the filter (32). A drive mechanism moves the filter so that regions of the filter pass successively over the open ends of the suction duct, where it may become partially blinded with sludge, and then over the water supply duct where it is backwashed.