Patent Description:
Automatic backwash traveling bridge sand filters are commonly used for the treatment of municipal and industrial water supplies as well as wastewater effluents. Owners attest to the outstanding performance and economics of the automatic backwash filter. In large part, the automatic backwash filter has stayed in the forefront of treatment technology.

The conventional automatic backwash filter underdrain design has been in use since the late <NUM>'s. The original design was constructed out of steel, which was changed to fiberglass in the mid <NUM>'s. However, there are certain difficulties associated with traditional designs. For example, field installation of the system may be labor intensive, caulking must be installed under clean and dry conditions, the caulking must be applied very consistently to provide an adequate seal, the sand media develops leaks in the caulk area, and the sand media leaks are difficult and expensive to repair.

Examples of the known filter underdrain designs are found in <CIT>, <CIT> and <CIT>.

Accordingly, a system is needed that is substantially leak proof and significantly reduces material and labor installation costs.

Some described aspects include a one-piece cell divider for use in a filter underdrain for supporting a porous plate in turn supporting a filter media for filtering a fluid, the one-piece cell divider comprising: a divider portion, wherein at least two divider portions form a cell; a porous plate support portion, comprising a flange that supports the porous plate; a support member portion, comprising a flange that is anchored to the one-piece cell divider to a base-plate.

Some described aspects include a one-piece cell divider wherein the flange that supports the porous plate is substantially perpendicular to the divider portion.

Some described aspects include a divider portion comprises one or more holes or attachment devices to receive a tie-rod or other device to maintain the one-piece cell divider in a set position.

Some described aspects include a one-piece cell divider for use in a filter underdrain for supporting a porous plate in turn supporting a filter media for filtering a fluid, the one-piece cell divider comprising: a divider portion, wherein at least two divider portions form a cell; a porous plate support portion, comprising a flange that supports the porous plate; a support member portion, comprising a flange that is anchored to the one-piece cell divider to a base-plate, and one or more angles attached to the divider portion used to hold the porous plate in contact with the porous plate support portion.

Some described aspects include a porous plate held in contact with the porous plate support portion by a fastener inserted through the porous plate and into the porous plate support portion.

The present invention is defined in the appended claims and includes a filter underdrain for supporting a filter media between a plurality of dividers forming at least one cell, the filter underdrain comprising: at least one porous plate for supporting the filter media for filtering a fluid, the porous plate spanning across at least one of the dividers; the plurality of dividers comprising: plurality of one-piece cell dividers; one or more multiple-piece dividers, each multiple-piece cell divider comprising a divider portion and a support member, the support member being directly under the divider portion.

Some described aspects include a filter underdrain for supporting a filter media between at least two dividers forming at least one cell, the filter underdrain comprising: at least one porous plate for supporting the filter media for filtering a fluid, the porous plate spanning across at least one of the dividers; the at least two dividers comprising: one or more one-piece cell dividers; one or more multiple-piece dividers, each multiple-piece cell divider comprising a divider portion and a support member, the support member being directly under the divider portion, wherein the at least one porous plate spans from one one-piece cell divider to a second one-piece cell divider, and/or wherein the porous plates have butt-joints where the porous plates join into the one-piece cell divider.

Some described aspects include a filter underdrain for supporting a filter media between at least two dividers forming at least one cell, the filter underdrain comprising: at least one porous plate comprised of polyethylene for supporting the filter media for filtering a fluid, the porous plate spanning across at least one of the dividers; the at least two dividers comprising: one or more one-piece cell dividers; one or more multiple-piece dividers, each multiple-piece cell divider comprising a divider portion and a support member, the support member being directly under the divider portion.

Some aspects of the present invention include a multiple-piece divider that comprises a saddle portion, the saddle portion being disposed on top of the porous plate and receiving the dividing portion into a saddle in the saddle portion.

These and other aspects will become apparent from the following description of the invention taken in conjunction with the following drawings, although variations and modifications may be effected without departing from the scope of the novel concepts of the invention.

The present invention can be more fully understood by reading the following detailed description together with the accompanying drawings, in which like reference indicators are used to designate like elements. The accompanying figures depict certain illustrative embodiments and may aid in understanding the following detailed description. Before any embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The embodiments depicted are to be understood as exemplary and in no way limiting of the overall scope of the invention. The detailed description will make reference to the following figures, in which:.

Before any embodiment of the invention is explained in detail, it is to be understood that the present invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The present invention is capable of other embodiments and of being practiced or being carried out in various ways.

The matters exemplified in this description are provided to assist in a comprehensive understanding of various exemplary embodiments disclosed with reference to the accompanying figures. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the exemplary embodiments described herein can be made without departing from the scope of the claims. Descriptions of well-known functions and constructions are omitted for clarity and conciseness. Moreover, as used herein, the singular may be interpreted in the plural, and alternately, any term in the plural may be interpreted to be in the singular.

An illustration of an exemplary conventional automatic backwash filter design is shown in <FIG>(a)-(b). A filter underdrain <NUM> may comprise a series of lateral partitions <NUM>, which may divide the filter bed into a multitude of compartments <NUM>. Each compartment may be arranged for connection to a separate effluent or backwash port <NUM>. Within each partition <NUM>, above the ports, there may be a porous plate <NUM>.

Porous plate <NUM> may act as a supporting deck or ledge for filter sand media <NUM> in each separate compartment <NUM>. Porous plates <NUM> may be typically formed from a heavy plastic, such as polyethylene, or ceramic such as aluminum oxide, and may be designed to support the weight of the filters and media. For example, media depth may be approximately <NUM> (<NUM> inches). In some typical configuration, five porous plates, each measuring approximately <NUM> (<NUM> inches) long by approximately <NUM> (<NUM> inches) wide may be installed in each of a <NUM> (sixteen-foot) wide compartment, or cell.

It is desirable for the joints between each of these porous plates to be sealed or substantially sealed to prevent or deter the sand media from leaking into the effluent port area. The porous plate may be typically sealed in each cell, for example, utilizing caulking. As shown in <FIG>(b), each porous plate <NUM> may be mounted to the partition and secured in place by angle <NUM> and mounting bolt hardware <NUM>. The space between porous plate <NUM> and partition <NUM> may be filled with caulking <NUM>.

<FIG> is an exemplary general diagram illustrating the components of a water filtration system incorporating an automatic backwash filter. During filtration, water may flow into filter tank <NUM> from influent channel <NUM>, through influent ports <NUM>, and onto filter bed <NUM>, which may comprise a plurality of filter cells <NUM>. Flow may be downward through filter media <NUM> contained in each filter cell <NUM> in filter bed <NUM> and into effluent channel <NUM> through each effluent port <NUM> in each underdrain <NUM> of each filter cell <NUM>. The filter media may typically be sand or a similar granular material, as is well known to those of skill in art.

Note that the system may be designed with and without air and/or water distribution. For example, systems may include a traveling bridge filtration system, which may incorporate an air wash or clean effluent sequence and equipment to prevent or deter media loss from an individual cell during air wash or effluent cleaning. In other examples, systems may be incorporated into a low-profile underdrain filtration system. In a filtration system incorporating a low-profile underdrain, an automatic backwash system may not be typically employed and individual filtration cells may not be used. Instead, the fluid to be cleaned fills a filtration bed, filtering down through the filter media and exiting through the underdrain. Backwashing is accomplished by taking the filtration system out of service and passing water (such as but not limited to clean effluent) and/or air is up through the filtration bed. Particulates and other materials released from the filter.

The backwash process may usually be initiated either by a predetermined head loss increase or by a preset time interval. Once initiated, the automatic backwash mechanism <NUM>, typically suspended from a motor-driven carriage <NUM>, may draw water from the effluent channel and discharge it into the underdrain <NUM> of the filter cell <NUM> being backwashed. The backwash water may expand and fluidize media bed <NUM> in the filter cell <NUM> to release at least some collected solids.

A washwater hood and pump <NUM>, also suspended from the carriage <NUM>, may capture the released solids and discharge them into a washwater trough <NUM> to be carried away. In some circumstances, backwash mechanism <NUM> may move along the entire length of the filter, backwashing each compartment in turn until all have been cleaned and the loss of head has returned to normal. At least some of filter cells <NUM>, except those in the compartment being backwashed, may remain in operation. Sufficient clean water is preferably maintained in effluent channel <NUM> to perform a backwash, generally eliminating the requirement for separate backwash water storage. Once carriage <NUM> reaches the end of filter tank <NUM>, it typically sits with the pumps off until another backwash cycle is automatically initiated.

Backwashing is not normally carried to completion. Regularly repeated short cleaning cycles are preferably employed to keep the media in a nearly clean condition and limit solids penetration to the upper <NUM> to <NUM> (<NUM> to <NUM> inches) of the media. The presence of some material within the bed aids in the removal of particulate material during filtration.

<FIG> illustrates some aspects of an automatic backwash filtration system. Automatic filter <NUM> may include a series of lateral partitions <NUM>, which divide the filter into a plurality of compartments <NUM>. Each compartment may be arranged for connection to a separate effluent or backwash port <NUM>. Each partition <NUM> may be supported on porous plate <NUM>. Filter sand media <NUM> may be filled in each compartment. Filter sand media <NUM> is typically, but not necessarily, filled to a depth of approximately <NUM> (eleven inches).

Porous plate <NUM> may be formed so as to be large enough to provide a media support for a plurality of cells, spanning a plurality of underdrain support members <NUM>. In one embodiment, porous plate <NUM> may be approximately <NUM> by <NUM> (four feet by four feet six inches) and provides support for either six <NUM> (eight inch) cells or four <NUM> (twelve inch) cells or other single or multiple combinations of cells.

The automatic backwash filter typically operates at hydraulic loading rates of <NUM> to <NUM> litres (<NUM> to <NUM> gallons) per minute per <NUM> square meters (square foot). Backwash may be initiated at a head loss increase of <NUM> to <NUM> (<NUM> to <NUM> inches) over clean bed conditions. Backwash typically occurs once every <NUM> to <NUM> hours, and each cell is backwashed for approximately <NUM> seconds. The total operating head loss through the filter is typically <NUM> to <NUM> (<NUM> to <NUM> inches) of water. The media in each compartment is preferably a <NUM> (<NUM>-inch) bed of sand, which is supported by the aforementioned plastic or ceramic porous plates. For some applications, alternative media designs such as dual sand and anthracite coal media up to <NUM> to <NUM> (<NUM> to <NUM> inches) in depth or activated carbon up to <NUM> (<NUM>") in depth are employed.

As shown in <FIG> and similar to <FIG> for the automatic backwash underdrain, each porous plate <NUM> may be supported by support members <NUM> at evenly spaced intervals. Porous plates <NUM> may be joined together at lap-joint <NUM> to help prevent the leakage of the filter media into the underdrain.

<FIG> illustrates a one-piece cell divider <NUM>, in accordance with some embodiments of the present invention. The one-piece cell divider <NUM> may be a single unit that replaces a lower support member and cell partition (or cell divider) from earlier systems. The one-piece cell divider <NUM> may therefore comprise an upper portion <NUM> that acts as a cell divider (or partition), and a lower portion that supports the porous plate. Porous plate may sit on surface <NUM>, and may be affixed thereto. In accordance with some embodiments, upper portion <NUM> may comprise one or more holes <NUM> configured to receive tie-rods or other devices to for additional support. The lower portion may further comprise one or more holes <NUM>, and may also comprise a bottom surface, which in turn may comprise one or more holes <NUM> for attachment. Such one-piece cell divider <NUM> may be used in addition to the more traditional multiple piece lower support members and cell partitions. Note that the one-piece cell divider <NUM> may also comprise an integral anchoring device formed into the cell divider, rather than requiring a separate bolt-on angle.

<FIG> illustrates that the one-piece cell dividers may be used, for example, every divider. With reference to <FIG>, the porous plates may be installed between the one-piece cell dividers. The solid one-piece cell divider may prevent or reduce leakage of filtration media (for example, sand) between dividers. Moreover, should a portion of the underdrain system need to be repaired or replaced, this may be accomplished without the need to disassemble most of the system. Moreover, such an arrangement may:.

Moreover, use of a one-piece cell divider may result in simpler maintenance. For example, during installation, a solid partition may be installed once every <NUM> (<NUM> feet). The porous plates may be sized to fit between these solid partitions. Lower partitions may still be present once every <NUM> or <NUM> (<NUM>" or <NUM>"), (depending on the design). This may also result in simpler installation and potentially less labor. The underdrain may now be installed using self-drilling / self-tapping screws. Previous designs often required a threaded stud that had to be located prior to installation of the porous plates and was secured using nuts and washers on the threaded stud. Easier maintenance is also to be expected.

Perhaps even more advantageously, analysis indicates that the use of a one-piece cell divider may even reduce initial capital costs, while installation costs to the customer may be very similar or less than conventional filters where every cell has its own porous plate (which requires additional labor for the caulking of seams).

<FIG> illustrates an exemplary assembly of the cell partitions. For example, as shown in <FIG>, the one-piece cell divider may be used every fourth divider. As noted, the remaining parts between the <NUM> (four-foot) span may comprise a two or three-part support design comprising a lower beam, saddle, and cell sheet. One-piece cell dividers <NUM> may be used, along with more traditional multiple piece support and dividers <NUM>. It can be seen from <FIG> that porous plates 830A, 830B, 830C may be positioned between the one-piece cell dividers <NUM>, and may be supported by the traditional multiple piece support and dividers <NUM>. Such an arrangement prevents media leakage between areas bordered by the one-piece cell dividers <NUM>.

<FIG> illustrates an exemplary system where every fourth divider is a one-piece cell divider. As noted, the remaining parts between the <NUM> (four-foot) span may comprise a two or three-part support design comprising a lower beam, saddle, and cell sheet.

<FIG> illustrates how, in accordance with some embodiments of the present invention, a one-piece cell divider may be used. One-piece divider <NUM> may be bolted or attached to baseplate <NUM> via a bolt, screw, or other fastener <NUM>, and held in place by tie-rod <NUM>. Porous plate <NUM> may be held into place by using an angle <NUM>, attached by a screw, bolt, or other fastener <NUM>.

In accordance with some other embodiments, and as shown in <FIG>, the angle in <FIG> may be omitted. In <FIG> one-piece divider <NUM> may again be attached to a baseplate <NUM> or other surface via fastener <NUM>. Tie-rod <NUM> may again maintain the one-piece divider <NUM> in a vertical or substantially vertical position. However, rather than use angle, a fastener (such as but not limited to a self-tapping screw) <NUM> may be used to attach porous plate <NUM> to the divider <NUM>. The use of self-tapping screws (or other fasteners) is possible since in accordance with some embodiments of the present invention the porous plate may be comprised of a plastic (such as but not limited to polyethylene) or ceramic (such as but not limited to aluminum oxide). Other plate materials may not permit the use of self-tapping screws or similar fasteners.

As noted above, when the one-piece cell divider is not utilized, a two or three-piece cell divider may be used. <FIG> illustrates a two-piece divider 1210A and a three-piece divider 1210B. Both sit atop the porous plate 1220A, 1220B. The two-piece cell divider has a flange <NUM> built in that allows the divider to sit atop the porous plate 1220A, while the three-piece cell divider may utilize a saddle <NUM> that receives a divider 1210B. There may be different variations of components, but the scope of the invention is directed to each variation.

<FIG> illustrates an exemplary arrangement of multiple piece support and dividers and may be used between the one-piece cell dividers. With reference to <FIG>, flanges on cell partitions <NUM> may be mounted to porous plate <NUM> and lower support member <NUM> by bolts or any other means of affixation in porous plate <NUM>. Stainless steel bars <NUM> and <NUM> or caulk beads may also be used. Mounting cell partitions <NUM> to lower support member <NUM> through porous plate <NUM> may be beneficial in that the porous plate may span more than one cell and removes the need for caulking of the mount between the porous plate and the cell dividers, as in conventional systems. An alternative to using flanges on cell partition <NUM> to mount it directly to porous plate <NUM> within a channel of a channel member, which in turn may then be mounted on the porous plate.

Those of ordinary skill in the art will appreciate that there is no limitation on plate size or spacing of the underdrain supports, plates, end pieces, etc. of the invention. Depending on material thickness, any length and width of these components may be made to span large distances. Moreover, the underdrain supports may be formed into single pieces to span a specific distance. The various components used in constructing the invention may utilize any number of materials, such as FRP, all plastics, steel, etc. For example, the porous plate may be made from plastics (such as but not limited to polyethylene), wood, steel, aluminum oxide, etc. The porous plate may also be replaced with some type of screen or mesh material.

The invention has several advantages in installation, such as reduced installation labor. A low-profile bottom cell divider simplifies grouting procedure. The elimination of the need for caulking saves significant installation time per cell. The use of a bolt-in top cell divider provides total access to porous plates during installation. The invention also has reduced risks. The illustrated embodiments provide for the elimination of paths for media leaks via a two-piece cell divider. The end wall pocket for the porous plate also has safety advantages. The elimination of porous plate "ledge joints" reduces risks. The invention has enhanced underdrain strength. For example, the porous plate is continuously supported. The I-beam design for lower cell divider improves strength, as does the bolt-in porous plate. It has a convertible media depth by virtue of a bolt-in top cell divider. It has reduced maintenance by reduced potential for media leaks. It has direct replacement capability for existing old-style design underdrains.

Claim 1:
A filter underdrain (<NUM>, <NUM>) for supporting a filter media (<NUM>, <NUM>) between a plurality of dividers forming at least one cell (<NUM>, <NUM>), the filter underdrain comprising:
at least one porous plate (<NUM>, <NUM>, <NUM>) for supporting the filter media for filtering a fluid, the porous plate spanning across at least one of the dividers;
the plurality of dividers comprising:
a plurality of one-piece cell dividers (<NUM>, <NUM>, <NUM>), each one-piece cell divider comprising:
an upper portion (<NUM>) which is configured to act as a partition between two cells;
a first flange (<NUM>) configured to support the porous plate; and
a lower portion (<NUM>) comprising a bottom surface configured to attach the one-piece cell divider to a base-plate (<NUM>),
wherein the first flange is located between the upper portion and the lower portion, and wherein the first flange is substantially perpendicular to the upper portion and the lower portion ; and
one or more multiple-piece dividers (<NUM>), each multiple-piece cell divider comprising a divider portion and a support member, the support member being directly under the divider portion, the divider portion and the support member being separate components;
wherein the porous plate is positioned between the one-piece cell dividers and supported by the one or more multiple-piece dividers, and
wherein the filter underdrain is assembled without the use of caulk.