Rigid filter elements, related apparatus and methods

Claim 1

A quadrilateral module for use in forming a rigid filter bed by laying a plurality of the modules side-by-side upon a flat support base comprising: a bottom grid member molded of rigid plastic and a top porous layer of particulate material of a single nominal size bound in a matrix of rigid cured binder defined by a flat, continuous upper surface and a lower surface substantially parallel to said upper surface, the thickness of said porous layer being appreciably less than the vertical height of said grid member, said grid member comprising a first series of strip elements substantially equally spaced apart, parallel and normal to said lower surface, said first series elements comprising an upper portion with a top edge and a lower portion with a bottom edge, said top edges of said first series elements lying substantially in a first single plane and said bottom edges of said first series elements lying substantially in a second single plane, said first and second single planes being substantially parallel to said lower surface, a second series of strip elements substantially equally spaced apart, parallel and normal to said lower surface and intersecting said first series elements at a right angle, said second series elements comprising an upper portion with a top edge and a lower portion with a bottom edge, said top edges of said second series elements lying substantially in said first single plane and said bottom edges of said second series elements lying substantially in said second single plane, said first and second series elements defining a multiplicity of quadrilateral vertical channels depending from said lower surface, said second series elements having lateral opening therein that extend upwardly into their lower portions from said bottom edges thereof, the maximum widths of said lateral openings being not greater than the distance between adjacent second series elements, said lateral openings defining a plurality of parallel, transverse channels in said module, said upper portions of said first and second series elements having integral bulbous enlargements at their top ends that are embedded in said top porous layer, said enlargements serving as means to anchor said top porous layer to said grid member, the periphery of said module being defined by a third series of strip side elements different from said first and second series elements having lateral outwardly extending projections that form a peripheral ledge around said module that is parallel to said lower surface.