Deep bed filter

A deep bed filter, comprising two vertically superimposed, essentially distinct, adjacent layers of filter medium granules, wherein the granules in the lower layer are not highly uniform in size, are naturally occurring materials, are finer than the granules in the layer thereabove and have a specific gravity of greater than about 1.3, the granules in the upper layer having a specific gravity in the range of from about 1.04 to about 0.04 less than the specific gravity of said lower layer and comprising hollow silica beads dispersed in a matrix of cured cement.

A deep bed filter, comprising a plurality of distinct layers, each layer consisting essentially of synthetic, water-wettable, filter medium particles and means for flowing contaminated liquid through said layers in succession, the particles of the successive layers increasing in density and decreasing in size in the direction of liquid flow therethrough, and each of said particles comprising hollow silica beads dispersed in a matrix of cured cement.

In a deep bed filter wherein a plurality of superimposed layers of filter medium particles are utilized to remove contaminants from liquid flowing downwardly through said layers, the improvement of an uppermost water-wettable surface layer consisting essentially of a plurality of filter particles each comprising hollow silica beads dispersed in a cured cement matrix and having a specific gravity ranging from about 1.04 to about 1.5, the particles being of substantially uniform size and shape to provide a water-wettable surface of sufficient porosity to be resistant to surface loading.

In a deep bed filter comprising a bottom, essentially distinct layer of sand, and an intermediate layer of anthracite superimposed over the sand and intermixed therewith along an interface region, the improvement of an essentially distinct, upper layer of filter media particles, the filter media of the upper layer being coarser than the anthracite and the sand;

• the media particles of the upper layer each comprising hollow silica spheres dispersed in a matrix of cured cement, the particles of said upper layer being substantially uniform in size and having an overall specific gravity ranging from about 1.04 to about 1.5.

A deep bed filter comprising a top layer of filter granules comprising hollow silica beads dispersed in a matrix of cured cement, and a lower layer of naturally occurring filter material having a specific gravity of at least about 1.3, the granules of said top layer having a specific gravity ranging from about 0.04 greater than that of the liquid being filtered to about 0.04 less than that of the granules of the lower level, up to a maximum of about 1.5.

A deep bed filter comprising a top layer of filter particles each comprising hollow, essentially spherical, silica beads dispersed in a matrix of cured cement, and at least one lower layer of naturally occurring particulate filter material have a specific gravity of at least 1.3 and greater than that of said top layer.

In a deep bed filter, which classifies after backwashing from coarse to fine in the direction of filtration flow, wherein a plurality of superimposed layers of filter medium particles are utilized to remove contaminants from liquid flowing downwardly through said layers, the improvement of an uppermost water-wettable surface layer of filter particles each comprising hollow silica beads dispersed in a cured cement matrix and having a specific gravity less than that of the media constituting the other layers to provide a water-wettable surface of sufficient porosity to be resistant to surface loading, the particles of the uppermost layer being coarser than the media of any of the underlying layers.

In a deep bed filter, which classifies after backwashing from coarse to fine in the direction of filtration flow, comprising a bottom layer of sand, an intermediate layer of anthracite superimposed on the sand, and a layer of nut shells or fruit pit shells superimposed on the anthracite, the improvement of at least one essentially distinct, upper layer of filter media particles superimposed on the shell layer, the filter media of the upper layer being coarser and lighter than the media of any of the underlying layers;

• the media particles of the upper layer each comprising hollow silica spheres dispersed in a matrix of cured cement.

A deep bed filter, which classifies after backwashing from coarse to fine in the direction of filtration flow, in which the bed comprises a bottom, essentially distinct layer of sand, a layer of anthracite superimposed on the sand, a layer of nut shells or fruit pit shells superimposed on said anthracite layer, and an uppermost layer of filter media particles superimposed on the shell layer, the media particles of the uppermost layer each comprising hollow silica spheres dispersed in a matrix of cured cement and the media of the separate layers being of progressively increasing specific gravity and of progressively decreasing size vertically downwardly of the bed.