Method of filtering

Abstract

Abstract A liquid filtering method for operating an apparatus comprising a deep bed of dual, vertically separate, granular filter media beds. The first filter media bed has relatively coarse, light grains, e.g. in a size range of 0.050 to 0.375 inches and having a specific gravity in the range of 0.9 to 1.6. The second filter media bed, which underlies the first bed, has finer, heavier grains which have a specific gravity greater than 2.1. During filtration, after flow downwardly through the first bed, a substantial portion of the partially filtered liquid is intercepted and directed upwardly through the second bed to a clean liquid outlet located within the depth of the second bed. The remainder of the partially filtered liquid continues to flow downwardly into and through the second bed to the same outlet. Upon backwashing, the first bed is slurried and turbulently recirculated through a path external of the retaining vessel, while the second bed is only expanded. After backwashing, the filter media beds assume their original respective orientations.

Inventors

• 👤 G Hirs

Bibliographic Details