Filtering apparatus

Abstract

Filter apparatus for removing fine solids from aqueous effluents, e.g., waste water filtration, comprises horizontal upper and lower rigid filter plates formed of aggregate fixed in a matrix of cured organic resin defining therebetween a secondary filter zone containing loose filter media, first and second fluid confining chambers above and below said filter plates respectively from which liquid can flow through the filter plates, a vertical conduit for conducting liquid from beneath the lower filter plate for discharge into the first chamber through an opening in the upper filter plate, conduits for inlet and outlet of liquid to said secondary filter zone and second chamber and a sparger to spray wash water on the top surface of the upper filter plate. In a filtering mode, the liquid suspension to be filtered flows into the first chamber via said vertical conduit and then passes, in turn, through the upper filter plate, the filter zone, the lower filter plate and the second chamber to discharge therefrom. In a washing mode, wash water from the sparger cleans the filter cake from the upper filter plate forming a slurry that discharges from the apparatus via the vertical conduit. Wash water to cleanse the lower plate and the filter media in the secondary filter zone is introduced into the second chamber to flow, in turn, through the lower filter plate, the filter zone and the upper filter plate to discharge via the vertical conduit. The new methods and apparatus remove solids with high efficiency while reducing ten fold or more wash water requirements as compared with prior art granular media filtration methods and apparatus.