A sediment separator – often also called sand separator – removes sand or other heavy solids from liquids. In a paper mill, those liquids are mainly filtrates from HD cleaners. The principle is quite simple: the feed flow is fed to a sedimentation tank where the heavy particles settle at the bottom; the settled particles are conveyed upwards by an inclined, shaftless screw while being dewatered further; and the dewatered solids drop off at the top of the screw where they are typically collected in a container.