Appts. for the separation of solids from a liq. flow from a container and the like, such as in recycling industrial waste water for further use, has a sepn. vessel (1) for the liq. to flow through. It contains a body (2) to reduce the flow speed in front of it so that heavier matter can drop through an opening (12) in the vessel (1) into a channel or closed extraction passage (3) with an extraction system, e.g. a curved pipe. The other end of the pipe extends over the water level (15) in the container. A screw or other type of conveyor (4) is within the pipe (3) to carry pptd. matter away from the immersed vessel (1) to an outlet opening (16) for collection.