Abstract: A sand filter is provided where dirtied filter media, generally sand, is continuously withdrawn from the filter container and lifted to the top of a juxtaposed separate wash vessel outside the container. The dirty media cascades in zig-zag fashion across and down a series of vertically spaced inclined baffles in the wash vessel extending alternately from opposite sides of the vessel so that a thin, relatively wide media stream falls from one baffle down to the next. A wash liquid, normally clean filtrate from the sand filter container, enters an inlet port adjacent to the bottom of the wash vessel and due to the coaction of the spaced baffles forms vertically-oriented circular flow patterns or vortices in alternative clockwise and counter clockwise directions so that portions of the wash liquid flow are directed to flow along with and in the same direction i.e. co-current flow, as the downwardly progressing and cascading media stream falling from one baffle member to the next baffle member.

Abstract: The invention relates to an apparatus for filtering a suspension or emulsion and comprising a bed (6, 7) of a particulate filter material arranged in a container or tank (1), one or more inlets (8) arranged at the lower part of the bed for the suspension or emulsion to be filtered, means (3) for removing filtrate and arranged above the bed, elevator means (13) for conveying contaminated filter medium from the lower part of the bed to a means (14) for washing or other treatment of the filter medium, and means for recycling treated filter medium to the upper part of the bed. According to the invention, the elevator means (13) for conveying contaminated filter medium is arranged movable along the horizontal extent of the filter bed and is preferably placed on a carrier means (14) which can be given a reciprocating movement, is arranged above the filter bed and also carries the means (14) for treating the filter medium.