Abstract:
A filter media backwash removal method and device for transporting backwash fluid and solids away from re-entering a housing containing circulating filter media.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 10/767,877 filed Jan. 29, 2004, now U.S. Pat. No. 7,223,347 which claims the benefit of priority of U.S. Application No. 60/443,429 filed Jan. 29, 2003 and U.S. Application No. 60/502,383 filed Sep. 12, 2003, all of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a method for removing backwash from a filter apparatus. 
     SUMMARY OF THE INVENTION 
     In embodiments of the invention, a backwash removal method is provided for removing backwash fluid during circulating and scrubbing of compressible media in a filter apparatus by air-elevating backwash fluid to a “highest” localized level above a lower surface level to drive the backwash fluid in a backwash removal device adjacent and contiguous to the localize elevated portion of backwash. In some embodiments, the process of the invention includes using one or more troughs that receive and remove backwash fluid. In further embodiments of the invention, the backwash process of the invention operates in a filter apparatus with a movable housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a single filter apparatus of the present invention showing a flexible housing for containing filter media in an embodiment of the present invention. 
         FIG. 2  is a schematic cross-sectional view of a filter apparatus of the present invention during initial filling with fluid to be filtered. 
         FIG. 3  is a schematic cross-sectional view of a filter apparatus of the present invention as the hydraulic head becomes greater upstream than in the downstream flow and the hydrostatic pressure of the unfiltered fluid compresses the flexible housing in an embodiment of the invention. 
         FIG. 4  is a schematic cross-sectional view of a filter apparatus of the present invention as influent level reaches an optional overflow pipe in an embodiment of the invention. 
         FIG. 5  is a schematic cross-sectional view of a filter apparatus of the present invention during backwash operation in an embodiment of the invention. 
         FIG. 6  is a schematic view of fiber being reduced from spools and bound for cutting into fiber media bundles in an embodiment of the invention. 
         FIG. 7  is a front perspective view of a filter media bundle in an embodiment of the invention. 
         FIG. 8  is a cross-sectional view of a filter media element including a hog ring/binding wire crimping and holding the center of the filter media bundle fibers in an embodiment of the invention. 
         FIG. 9  is a schematic cross-sectional view of a concentric bi-component fiber in an embodiment of the invention. 
         FIG. 10  is a schematic cross-sectional view of an eccentric bi-component fiber in an embodiment of the invention. 
         FIG. 11  is a schematic cross-sectional view a multi-component fiber in an embodiment of the invention. 
         FIG. 12  is a schematic cross-sectional view depicting first and second compression zones of compressible filter media in a filter media housing in an embodiment of the invention. 
         FIG. 13A  is a schematic cross-sectional view of a filter media housing including uncompressed filter media and a backwash removal device in an embodiment of the invention. 
         FIG. 13B  is a schematic top plan view of a backwash removal device along line I-I of  FIG. 13A  in an embodiment of the invention. 
         FIG. 14A  is a schematic top plan view of a plurality of filter units within a large fluid containment in an embodiment of the invention. 
         FIG. 14B  is a schematic cross-sectional view of a plurality of filter units along line II-II of  FIG. 14A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides an apparatus and method for filtering fluids with compressible filter media contained in a flexible housing. In the described embodiments, fluid outside the housing compresses the housing and filter media; however, it will be appreciated that a variety of external forces may be applied to the outer housing and compressible media to achieve the objectives of the invention in other embodiments. It will also be appreciated that although the invention is described in embodiments for top to down filtering of fluid, the apparatuses and components described herein may be positioned such that the filtration may occur in other directions, and repositioning is within the scope of the invention. 
     The present invention thus provides improved filtration, and is particularly adapted for the filtration of stormwater, drinking water and wastewater. Those skilled in the art will further appreciate that in other embodiments the present invention is adapted for use with a variety of fluids and filtering applications. 
     Referring to  FIG. 1 , in an embodiment of the present invention a filter apparatus  10  includes an outer fluid container  15 . Outer fluid containment housings include concrete containers, earthen basins, natural water features (including a lake), and like environments in which fluid to be filtered may be contained. An influent pipe  20  provides fluid to be filtered into the outer container  15 . It will be appreciated that the influent pipe  20  may be located in a variety of positions (such as above or below the top of the filter) and or/include a plurality of influent pipes  20 . 
     Within the outer container  15  an upright filter media housing  25  is provided.  FIG. 1  depicts the filter media housing  25  comprising a flexible membrane in both expanded and compressed embodiments to demonstrate compressibility of the housing. The top of the filter media housing  25  includes an upper perforated plate  30  to allow fluid to be filtered into the housing, as well as backwash fluid out of the housing, while retaining the filter media within housing (such as during backwash processes subsequently described). 
     A housing base  35  secures the filter media housing  25  at the bottom of the outer container  15 . 
     In one embodiment, the base may include baffles  40  that direct filtered fluid to an effluent pipe  45  carrying filtered fluid from the filter housing  25  out of the containment  15 . The baffles  40  may also direct air and make-up water to the center of lower perforated plate  50  during backwashing operations ( FIG. 5 ). 
     Referring to  FIGS. 14A and 14B , in other exemplary embodiments, the containment  15  may include a plurality of filter units  11  wherein the base may be a wall of an effluent channel/conveyance  45 A or a piping network underlying one or more filter units  11 . In such embodiments, the channel wall or piping serves as the base to support one or more filter units  11  is an upright position within the outer containment  15 . The integrated filter unit  11  into the conveyance  45 A may be provided without baffles  40 . 
     In a large containment environment as shown in  FIGS. 14A and 14B , the underlying effluent conveyances (or piping)  45 A may all connect to a larger effluent conveyance  45 B for carrying off filtered fluid. In other embodiments underlying conveyances  45 A may be directed to other desired locations and conveyance points. 
       FIGS. 14A and 14B , also show that one or more backwash pumps  72  may be provided for removing backwash fluid from the containment  15  following the backwash process (subsequently described). 
     In embodiments utilizing a plurality of filter units  11 , it will be appreciated that the containment  15  may include a large basin, natural feature, manmade containments and the like, where a large quantity of fluid is to be filtered. It will also be appreciated each of the filter units  11  includes compressible media  60  and a filter media housing  25  and operates as subsequently described with reference to a single filter unit. 
     Referring again to  FIG. 1 , between the upper plate  30  and base  35 , the lower perforated plate  50  allows filtered fluid to exit the flexible housing  25 . The lower perforated plate  50  also supports filter media  60  ( FIG. 2 ) within the housing  25 . 
     With further reference to  FIG. 2  and  FIGS. 7-11 , compressible filter media  60  is housed within the housing  25  between the upper perforated plate  30  and lower perforated plate  50 . Although the filter bundles disclosed in U.S. Pat. No. 5,248,415 to Masuda et al. and U.S. Patent Application Publication No. US2003/0111431 are particularly adapted for use as filter media  60  in the present invention, a variety of compressible fibrous filter elements may be used. 
     In certain embodiments, the fibrous media  60  of the present invention improves upon the prior art through the use of multi-component fibers where two or more synthetic materials are used in the same fiber to achieve the physical characteristics such as specific gravity, resilience, chemical resistance, stiffness, fiber diameter, and the like. In other embodiments, the filter media fiber may further include components with specifically desired performance characteristics such as specific pollutant removal capabilities. For example, oleophilic fiber components may be used in embodiments for attracting oil from fluid being filtered or hydrophobic fibers may be used to encourage water filtration. Those skilled in the art will appreciate that a wide variety of other combinations of components in the filter media may be adapted for use in the present invention depending on the desired performance the type of fluid and pollutants being filtered. 
     In one embodiment to achieve a chemically resistant fibrous lump of low resilience and lower specific gravity, the fiber is manufactured with a nylon inner core and polypropylene outer cover. 
     In another embodiment to obtain a heavier, more resilient lump  61  ( FIGS. 7 and 8 ), the fiber is manufactured using a polyester inner core with a polypropylene sheath. 
     Referring to  FIG. 9 , in one embodiment the multi-component fiber is a bi-component fiber, wherein an inner fiber  65  and an outer fiber  67  (sheath) are provided/extruded in a generally concentric configuration. 
     Referring to  FIG. 10 , in another embodiment the components are generally eccentric with the inner component  65  being off-center. In such embodiment, subsequently described, the eccentric configuration permits heating of the fiber to produce crimping based on the resultant heat distortion. 
     It will be appreciated that in alternative embodiments a plurality of inner fibers  65  may be contained in a sheath  67 , such as shown in  FIG. 11 . In such embodiments, the plurality of inner fibers  65  may be the same or different component materials. It will also be appreciated that one or more additional outer sheaths could be provided in alternative embodiments to achieve specific pollutant removal as well as exhibit desired physical characteristics. 
     In various embodiments, core and sheath materials may include any combination of the following, or other synthetic fibers: polyester (PET), coPET, polylactic acid (PLA), polytrimethylene terephthalate, polycyclohexanediol terephthalate (PCT), polyethylene napthalate (PEN); high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polyethylene (PE), polypropylene (PP), PE/PP copolymer, nylon, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and polyurethane. 
     Referring to  FIG. 6 , the fibers used as filter media  60  are initially in the form of loosely packed elongated fibers  70  on spools  75 . 
     With continuing reference to  FIG. 6 , several bundles of elongated fibers  70  are brought together from the spools  75  using a reducing device  80 . The device  80  reduces the overall size of the fibers while a hog ring fastener/binding wire  85  or other similar clamp is applied. After the clamps are applied, the fiber bundles are cut at cut lines  90  between each clamp  85  to form a fibrous lump  61  ( FIGS. 7 and 8 ). 
     In embodiments of the invention, the multi-component fibers can be crimped mechanically and/or by heating. 
     A mechanical crimping machine is used in one method. Following extrusion, the fibers are mechanically crimped along the length of the fibers to produce crimped fiber. A second method is to produce the multi-component fiber  65  such that the core materials are placed eccentrically from the sheath  65  ( FIG. 10 ). When heat is applied, the fiber materials distort differently resulting in a helically shaped crimp. The amount of heat applied is dependent on the fiber materials. 
     Referring again to  FIG. 2 , during initial filling, fluid  22  to be filtered enters from the influent pipe  20  and fills the void  28  between the outer container  15  and flexible housing  25 . The air inlet  90  is off. The drain  95  is closed. 
     With continuing reference to  FIG. 2 , initial compression of the filter media is adjustable and can be set by the level of fluid and media inside the filter media housing  25  at the beginning of the filter run. After backwashing (see  FIG. 5  and related description), the media is in a relatively uniform suspension with density equal to the number of filter media bundles  61  per volume of fluid within the flexible membrane  25 . A lower fluid level inside the flexible membrane  25  will result in a greater density of filter media  60  and thus a greater initial compression when the void space  28  begins to fill and the flexible membrane  25  compresses the filter media  60 . A higher fluid level left inside the flexible membrane  25  at the beginning of the filter cycle will result in a lower initial compression. Initial compression is shown in  FIG. 2 . During this initial filling, it will be appreciated that the flexible housing  25  is relatively expanded until the hydrostatic pressure outside the housing  25  exceeds the pressure within the housing  25 . 
     With further reference to  FIGS. 3 and 12 , fluid  22  rises above the upper perforated plate  30  of the flexible membrane housing  25 , the fluid  22  enters the top perforated plate  30  for filtering by the filter media  60 . The fluid being filtered  22  passes downward through the filter media  60  with particulates being removed from the fluid. It will be appreciated that, in general, larger particulates are removed nearer the top of the filter bed with smaller particulates removed deeper in the media bed and as solids begin to bridge the voids between the media fibers a matting takes place resulting in removal of both fine and larger particles in the upper media zone ( FIG. 12 ). It will also be appreciated that less compression with media open to the fluid being filtered  22  results in the upper zone of the media bed and more compression results in the lower zone. Because of the compression zones, the filter bed becomes more effective in removing a larger amount of particulates per unit of media and protect the finer particulates from passing through the filter. The compression differential described above between the upper and bottom zones of the media bed is created in the initial compression developed after backwashing or during initial filter operation. 
     With continuing reference to  FIG. 12 , initial compression shows the lower filter media bed  60 B to be compressed inward by the filter media housing  25 . The upper filter media bed  60 A is relatively uncompressed as the housing  25 , in embodiments where the housing is a flexible membrane, remains tight and relatively inflexible at the upper portion of the housing  25  between upper plate  30  and a taper point  27 . 
     In other embodiments the filter media housing  25  may include a plurality of components to achieve the similar effect of multiple compression zones. For example, the upper portion of the housing  25  may comprise a rigid element connected to a lower membrane (lower portion of housing  25 ). The upper filter media  60 A in such embodiment would be uncompressed from the external fluid as the rigid upper portion would not flex inward. The flexible lower portion of the filter membrane would be compressible by the outer fluid to generate compressed lower bed  60 B. 
     In still other embodiments, the housing  25  could include a lower housing portion with hinged plate walls instead of a flexible membrane. In such embodiments, the hinged wall could be provided with a hinge near taper point  27 , wherein the upper portion of the housing  25  would be a relatively rigid component. Such walls could be provided in a variety of shapes, including flat wall plates with leak-resistant membranes or materials joining one plate to the next plate. Sliding mechanisms may also be used for a portion of the housing to compress inward. It will be appreciated that all such embodiments permit the external fluid pressure to compress the lower portion of the housing and the lower filter media bed  60 B inward. 
     In embodiments where the housing  25  is flexible, it may be constructed of single or multi-ply membranes of chlorosulfonated polyethylene (Hypalon), polyvinyl chloride (PVC), rubber, viton, polypropylene, polyethylene, vinyl, neoprene, polyurethane and woven and non-woven fabrics. In embodiments where rigid materials are used, such as those including an upper rigid portion or including pivotable or sliding housing walls, construction materials could include steel, stainless steel, other metals, reinforced and unreinforced plastics. It will be appreciated, however, that the filter media housing  25  may be constructed of any suitable material depending on the desired filtering use, types of fluids being filtered, desired corrosive characteristics and the like. 
     It will also be appreciated that although the present invention is shown in embodiments with external fluid pressure generating compressive force against the housing  25  and filter media  60 , other external forces may also, or additionally, be used to compress the lower filter media bed  60 B. For example, in other embodiments, the side walls of the housing  25  may be actuated in an inwardly pivotable or sliding manner through mechanical, electrical, hydraulic and similar operation. In other embodiments, inflatable components may be provided external to the housing and inflated in a balloon-like manner to press against the housing and compress the filter media. 
     Referring again to  FIG. 12 , the top surface of the filter media bed  60  includes space  62  (see also  FIGS. 2-4 ) that is open and untouched by the upper perforated plate. In such embodiment, the upper filter media zone  60 A remains uncompressed by not only the housing  25 , but also avoids external top to down compression from the upper plate  30  because of spacing  62 . It will also be appreciated that the initial compression with relatively uncompressed upper filter media bed  60 A with an open surface and the compressed lower filter media bed  60 B will result in greater particulate penetration than if the upper filter media bed  60 A were compressed or the entire bed were compressed. Finer particulates may therefore be captured in the lower media bed  60 B as greater penetration is achieved. It is thus an object of the present invention to maximize fluid filtering efficiency. 
     Referring further to  FIGS. 3 and 4 , as filtration proceeds and more particulates are removed, the hydraulic head differential across the filter becomes greater ( FIG. 3  to  FIG. 4 ) causing greater compression in the lower zone  60 B to prevent smaller particulates from passing through. There is also a slight upheaval of upper media zone  60 A as the lower zone  60 B compresses to allow more particulates to enter the filter media  60 . Compression of the filter media  60 , as described with reference to  FIGS. 3 and 4 , thus improves filtering as increasingly smaller and more particulate is removed in the filter media bed  60 . 
     In embodiments of the invention, the flexible housing  25  shape is also generally wider at the upper portion than at the lower portion of the housing  25 . It will be appreciated that in such embodiments, less filter media  60  is required at the bottom as the filter bed narrows to direct the fluid out of the housing  25  and the fluid  22  being filtered is “cleaner” toward the bottom. Further, the generally tapered embodiment provides additional filter benefits as the media is more loosely packed near the more “open” upper portion and is more densely packed nearer the bottom portion of the housing. 
     In other embodiments, it will be appreciated that in addition to or instead of tapering housing shapes, different compression levels may be created by higher media concentrations with lower inner fluid levels. Different filter materials and combinations of materials with desired physical properties may also be used to achieve different compression levels, including the layering of filter media with different densities, compressibility or other desired physical and performance characteristics to achieve a desired filter bed that may include one or more zones. 
       FIG. 3  shows the hydraulic head in the upstream portions outside the flexible housing  25  becoming greater than the downstream hydrostatic pressure. The hydraulic head differential is due to both the flow stream through the filter media  60  and the build-up of particles on the filter media  60 , resulting in increasing upstream fluid level as solids are removed ( FIGS. 3 and 4 ). As the hydrostatic pressure outside the filter media housing  25  becomes greater than the hydrostatic pressure inside the housing  25 , the housing  25  is further compressed inward, thereby further compressing the filter media  60 . In embodiments of the invention, the housing  25  and filter media  60  are compressed in a direction non-parallel, including generally perpendicular in some embodiments ( FIGS. 2-4  and  12 ), to the direction of the fluid flow through the filter media. And as also shown in  FIG. 12 , and previously described, a plurality of compression zones may be established, such as lower portion of the filter media bed  60 B being compressed to remove finer particulates and protect the filter media bed  60  from particle breakthrough. 
     Referring to  FIG. 4 , an embodiment of the invention is shown when the filtration cycle has reached its latter stages and/or during a period of peak upstream fluid flow. The latter stage of the filtration cycle is reached when the filter media  60  captures its maximum particle load, and the depth of fluid  22  over the top of the upper perforated plate  30  reaches it maximum fluid level. 
     In one embodiment of the invention, when the fluid  22  over the filter apparatus  10  reaches it maximum fluid level, closing the influent  20  stops the filter cycle. In this embodiment the backwashing cycle ( FIG. 5 ) is initiated. 
     In another embodiment of the invention where an overflow pipe  100  is provided, the filter cycle continues whereby fluid  22  is both filtered through the media bed  60  and a portion of the fluid bypasses the filter and is discharged from the outer housing  15  along with the filtered effluent  45 . It will be appreciated that filtration of wet weather flows, such as treatment of stormwater or treatment of wet weather discharges from sewer systems, can be designed to remove a specific particle load according to a desired need for a particular event, and after the load is reached or the design flow rate is reached, excess flows and excess particle loads may be discharged from the filter. 
       FIG. 5  shows the filter media  60  being backwashed to remove particulate build up. During a backwash operation fluid entry from the influent pipe  20  is stopped. Make-up water  23  is introduced into the filter effluent pipe  45  or to an open-close connection valve to the outer section of the housing base portion  35 . A backwash outlet, such as a backwash pump discharge  105  connected to a backwash pump  72  ( FIG. 14A ), can be used to remove the backwashed particles from the containment housing  15  or the backwashed fluid can be removed from the containment  15  by opening a drainpipe  95 . During backwash the fluid level within the containment housing  15  is lower than the water level within the filter media housing  25  causing the housing  25  to expand. 
     In the backwash cycle, an air inlet  90 , provides air from a blower at the base portion  35  or under the lower perforated plate  50 . It will be appreciated that the backwashed fluid containing the concentrated particulates from the fluid to be filtered  22  is typically transferred to a sanitary sewer system for further treatment, removed by vacuum vehicle equipment for transport to other facilities for further process or by further processing the backwash fluid on-site by other concentrating and dewatering processes. 
     The air from the air inlet  90  enters the center section of the base  35  and rises through the center of the lower perforated plate  50  and up through the center of the filter media  60 . The upward center airflow causes the filter media  60  to circulate within the expanded filter media housing  25  during the washing cycle. Circulation of the filter media  60  causes the media  60  to collide with the upper perforated plate  35  and with other media bundles  60 , helping particulates to dislodge. The lower specific gravity of the air/fluid mixture or the hydraulic head of the backwash water within the housing  25  causes the fluid level within the housing  25  to rise and flow over the upper perforated plate  30  into the void  28  inside of the outer container  15  and outside the housing  25 . The backwash fluid exits containment  15  by either gravity drainage through drain  95  or pumping through outlet  105 . 
     Another embodiment, shown in  FIGS. 13A and 13B , includes backwash removal device  200  having troughs  201 , placed on the upper perforated plate  30 . In this embodiment, troughs  201  form a donut-shape around the center of the air inlet on the upper perforated plate  30 . The troughs  201  receive the backwash fluid with concentrated particulates as the backwash fluid rises above the perforated plate  30  (through the action of centrally directed air) and is directed through the radial troughs  201  to the void  28 , thus minimizing particulate recirculation during the backwash mode. It can be appreciated that the quicker the backwash fluid is separated from the circulating media, the less make-up water is required to clean the filter and the shorter the backwashing cycle time. It can also be appreciated that water level in the center of the upper plate  30  is at the highest level caused by the central rising air and this hydraulic head is used to drive the backwash fluid through the radial toughs  201  into the void  28  for removal. 
     In another embodiment, a drain  95  is provided at the bottom of the outer container  15 . The drain  95  can also be opened to remove fluid from inside the outer container  15 , such as following backwashing. Further, the void  28  between the outer container  15  and housing  25  can be cleaned, and the drain  95  opened to remove the cleaning fluid. It will be appreciated that a plurality of drains  95  may also be provided. 
     In another embodiment, the backwash removal device  200  can be designed with troughs  201  being enclosed, for example, using pipes to carry backwash water out of the outer containment  15 . It can be appreciated that in certain outer containment structures such as earthen basins with permanent lower water levels or natural water features (such as lakes), the outer containment  15  would not be drained and it may be desired that backwash water be discharged outside of the outer containment  15 . It can be further appreciated that in this application the compressible media housing  25  may be actuated inwards or outwards by an inflatable balloon or similar alternative method as described previously. It can be further appreciated that in an application where the outer containment  15  is a natural water feature with a fixed water level, the fluid inlet to the filter may be closed when backwashing occurs. 
     Accordingly, while the invention has been described with reference to the structures and processes disclosed, it is not confined to the details set forth, but is intended to cover such modifications or changes as may fall within the scope of the following claims.