초록 ▼

A filter for filtering contaminants from liquid, wherein the apparatus includes several distinct, adjacent layers of granular filter medium. The layers are carefully graded for size and density, with the granules constituting the layers increasing in density and decreasing in size in the direction o

A filter for filtering contaminants from liquid, wherein the apparatus includes several distinct, adjacent layers of granular filter medium. The layers are carefully graded for size and density, with the granules constituting the layers increasing in density and decreasing in size in the direction of filter flow. At least some of the layers are composed of essentially uniformly sized and shaped, water-wettable synthetic granules of a specific gravity ranging from about 1.04 to about 1.5. For some applications, all of the bed layers are formed of such synthetic granules; for other applications, some of the layers, preferably the lower layers, are formed of naturally occurring materials, such as anthracite, sand, and fruit pit shells or nut shells. In either form of the invention, the distribution of density and size in the direction of flow－normally downwardly－is such that the layers readily stratify after backwashing to reconstitute the bed in its initial, most efficient filtration configuration. In the operation of the device, staged filtration is achieved with larger contaminants accumulating in the upper filtration layer and smaller contaminants progressively accumulating in the subsequent layers. After backwashing by reverse liquid flow, the layers are reformed substantially in place without substantial intermixing between the layers as a result of the graded granule sizes and specific gravities.

대표청구항 ▼

A deep bed filter, which classifies after backwashing from coarse to fine in the direction of filtration flow, comprising a plurality of vertically superimposed, essentially distinct layers of filter medium granules, wherein the granules in each layer are water-wettable, are substantially uniform in

A deep bed filter, which classifies after backwashing from coarse to fine in the direction of filtration flow, comprising a plurality of vertically superimposed, essentially distinct layers of filter medium granules, wherein the granules in each layer are water-wettable, are substantially uniform in size, are smaller than the granules in the layer thereabove, have a specific gravity ranging from about 1.04 to about 1.5, are of a specific gravity greater than the granules in the layer thereabove, and classify after backwashing from coarse to fine in the direction of filtration flow, each granule in each layer comprising hollow silica beads dispersed in a matrix of cured cement.