Abstract:
An apparatus, system, and method for removing sediment from water is disclosed. According to one embodiment of the present invention, the apparatus includes a tubular filter assembly comprising a support member; and a filtratable element surrounding the support member, the filtratable element comprising a backing mesh; and a fibrous batting. A system for removing sediment from water is disclosed. According to one embodiment, the system includes a filter chamber to receive a liquid having suspended particles therein; at least one filtration cartridge housed within the filter chamber, wherein the filtration cartridge comprises at least one elongated filtratable element, each filtratable element comprising a support member, and a filtratable media adapted to surround the inner core. A method for removing sediment from water is disclosed. According to one embodiment, the method for removing suspended particles from a liquid includes (1) receiving liquid containing suspended particles into a filter chamber, wherein the filter chamber comprises an inlet and outlet positioned to create pressure differential sufficient to drive the liquid through the filter chamber; (2) filtering the suspending particles from the liquid through at least one elongated filtratable element; and (3) discharging the filtered liquid.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to an apparatus, system, and method for removing sediment from water, and, more particularly, to an elongated filtratable element used for removing sediment from stormwater. 
         [0003]    2. Description of the Related Art 
         [0004]    Stormwater runoff is rainfall or snowmelt that travels over the ground or impervious surfaces—roofs of buildings, homes and sheds, roadways, parking lots, sidewalks and driveways—and drains into natural or manmade drainage ways. In some cases, stormwater runoff drains directly into bodies of water. Stormwater runoff does not usually receive any treatment before it enters streams, lakes, and other surface waters, and it is a major source of water pollution. For example, various harmful pollutants, such as pesticides, fertilizer, litter, car oil, bacteria, trace metals, and sediment, are washed off with stormwater runoff into storm drains, or directly into streams, rivers, and lakes. 
         [0005]    One of the harmful pollutants of major concern is sediment. Sediment is soil particles from stream banks, construction sites, and other areas, that are dislodged by stormwater runoff and deposited into streams, lakes, and rivers. Sediment accumulates in water bodies and destroys feeding grounds for aquatic life, clogs fish gills, blocks light, increases water temperature, and can cause other adverse environmental impacts. 
         [0006]    Currently, sedimentation-based tanks are used to remove the majority of sediment that is dislodged by stormwater runoff. Sedimentation-based tanks, however, cannot completely remove all of the fine sediment from stormwater because of the required settling time needed for fine sediment to be removed from stormwater. For example, settling out the fine sediment in stormwater would require a large and uneconomical sedimentation-based tank. Therefore, in addition to sedimentation-based tanks, granular media filter systems are used downstream of sedimentation-based tanks to remove fine sediment. Granular media filter systems utilize different types of granular media to trap fine sediment in the interstitial gaps formed between the granular media. However, as the fine sediment continues to accumulate, the interstitial gaps eventually clog and must be frequently recharged. Granular media filter systems can be partially recharged through pressurized backwashing, but pressurized backwashing piping and controls are complicated and expensive. 
         [0007]    In addition to granular media filter systems, a variety of other filter systems are available for filtering contaminated fluids. For example, filter cloths consisting of pile threads may be used, U.S. Pat. No. 6,103,132, which is incorporated by reference herein. While these types of filters and others like them have their merits, they also have their drawbacks. For example, the filters have a small amount of surface area available for trapping fine sediment. As a result, during high flow events, the filter systems quickly clog, causing the stormwater runoff to back up. In addition to filter cloths, flexible hose-type filter elements have been used, U.S. Pat. No. 4,163,724, which is incorporated by reference herein. Such hose-type filter elements, however, rely on pressurized flow to effect separation. 
       SUMMARY OF THE INVENTION 
       [0008]    An apparatus, system, and method for removing sediment from water is disclosed. According to one embodiment of the present invention, the apparatus includes a tubular filter assembly comprising a support member; and a filtratable element surrounding the support member, the filtratable element comprising a backing mesh; and a fibrous batting. 
         [0009]    A system for removing sediment from water is disclosed. According to one embodiment, the system includes a filter chamber to receive a liquid having suspended particles therein; at least one filtration cartridge housed within the filter chamber, wherein the filtration cartridge comprises at least one elongated filtratable element, each filtratable element comprising a support member, and a filtratable media adapted to surround the inner core. 
         [0010]    According to another embodiment of the present invention, the system includes a filter chamber adapted to receive stormwater runoff; at least one filtration cartridge housed within the filter chamber, wherein the filtration cartridge comprises at least one elongated filtratable element, each filtratable element comprising support member; and a filtratable media adapted to surround the inner core. 
         [0011]    A method for removing sediment from water is disclosed. According to one embodiment, the method for removing suspended particles from a liquid includes (1) receiving liquid containing suspended particles into a filter chamber, wherein the filter chamber comprises an inlet and outlet positioned to create pressure differential sufficient to drive the liquid through the filter chamber; (2) filtering the suspending particles from the liquid through at least one elongated filtratable element; and (3) discharging the filtered liquid. 
         [0012]    According to another embodiment of the present invention, the method includes (1) introducing sediment-laden stormwater into a filter chamber, wherein the filter chamber houses a plurality of elongated filtratable elements that are removably attached to at least one filtration cartridge; (2) allowing the sediment-laden stormwater to permeate through the plurality of elongated filtratable elements, wherein the plurality of elongated filtratable elements trap a substantial amount of sediment; and (3) discharging filtrate from the filter chamber. 
         [0013]    According to another embodiment of the present invention, a separator tank is disclosed. The separator tank includes a tank having an inlet and an outlet; a divider dividing the tank into a treatment portion and a bypass portion; a first opening in the divider proximal to the inlet of the tank and enabling communication between the treatment portion and the bypass portion; a second opening in the divider proximal to the outlet of the tank and enabling communication between the treatment portion and the bypass portion; a weir disposed between the first opening and the second opening and operative to create a hydraulic head between the first opening and the second opening; and at least one filtration cartridge attached to the divider, wherein the filtration cartridge comprises a plurality of elongated filtratable elements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    For a more complete understanding of the present invention, the objects and advantages thereof, reference is now made to the following descriptions taken in connection with the accompanying drawings in which: 
           [0015]      FIG. 1A  is a perspective view of a elongated filtratable element according to one embodiment of the present invention; 
           [0016]      FIG. 1B  is a perspective view of a elongated filtratable element according to one embodiment of the present invention; 
           [0017]      FIG. 2  is a perspective view of a preassembled filter mat according to one embodiment of the present invention; 
           [0018]      FIGS. 3A-3C  are perspective views of magnified sections of a filter mat according to one embodiment of the present invention; 
           [0019]      FIGS. 4A-4B  are perspective views of a filtration cartridge according to one embodiment of the present invention; 
           [0020]      FIG. 5A-5B  are perspective views of a filtration cartridge according to one embodiment of the present invention; 
           [0021]      FIG. 6  is a perspective view of a shaking mechanism according to one embodiment of the present invention; 
           [0022]      FIG. 7  is a perspective view of a filtering system according to one embodiment of the present invention. 
           [0023]      FIG. 8  is a perspective view of the inlet device according to one embodiment of the present invention. 
           [0024]      FIGS. 9A-9B  are perspective views of the filtration system according to one embodiment of the present invention. 
           [0025]      FIGS. 10A-10B  are a perspective views of a filtration system according to one embodiment of the present invention. 
           [0026]      FIG. 11  is a perspective view of a filtration system with a backwashing mechanism according to one embodiment of the present invention. 
           [0027]      FIGS. 12A-12B  are perspective views of a valve assembly according to one embodiment of the present invention. 
           [0028]      FIG. 13  is a perspective view of a filtration system with a backwashing mechanism with a partition, where accumulated filtrate is above each valve assembly according to one embodiment of the present invention. 
           [0029]      FIG. 14  is a perspective view of a filtration system with a backwashing mechanism where each elongated filtratable element has been backwashed according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0030]    Although the present invention is described in the context of stormwater filtration, the invention is not so limited. Rather, the present invention has application as a filter media for many types of liquid, including water. Stormwater runoff generally has an “organic portion” and an “aqueous portion.” The organic portion of stormwater runoff typically has a relatively high amount of sediment, which includes, for example, dislodged soil particles from stream banks, construction sites, and other areas. The aqueous portion of stormwater is primarily water. As used herein, the term “downstream” in a process system means later in the direction of general process or fluid flow, and the term “upstream” means earlier in the direction of general process or fluid flow. 
         [0031]    Disclosed embodiments of the present invention and their advantages may be understood by referring to  FIGS. 1-14 , wherein like reference numerals refer to like elements. 
         [0032]    In accordance with an embodiment of the present invention described herein is an elongated filtratable element that has a large amount of surface area for filtering a substantial amount of fine sediment from stormwater. The disclosed filtratable element can be used individually or in combination with other filtratable elements. And, the filtratable elements can be combined with current stormwater filtering systems to improve efficiency. 
         [0033]    According to one embodiment of the present invention, the elongated filtratable element may be a tubular element or hollow tube with a permeable fiberglass filter media that surrounds a flexible inner core. The fiberglass filter media may have a porosity such that it allows the aqueous portion of stormwater to pass through, while trapping sediment. 
         [0034]    Referring to  FIG. 1A , a perspective of elongated filtratable element  100  and its components is shown. According to one embodiment, each elongated filtratable element  100 , or tentacle, includes three general components: support member  101 , filter mat  102 , and outer casing  103 . In general, support member  101  prevents the surrounding filter mat  102  from collapsing. Filter mat  102  consists of any permeable filtratable material that surrounds inner core  101 . Filter mat  102  may be adapted to filter a substantial amount of fine sediment from stormwater runoff. Outer casing  103  protects filter mat  102  from abrasion. Each component will be described in greater detail below. 
         [0035]    In one embodiment, support member  101  may be adapted to be an inner core that serves as a frame for elongated filtratable element  100 , and may be provided to prevent elongated filtratable element  100  from collapsing upon itself. Support member  101  may comprise a flexible support tube made of any water permeable member, such as a polymer membrane. While any water permeable polymer materials may be used, in one embodiment, support member  101  may be made of a plastic, such as polyurethane, acrylate, polypropylene or polyethylene. 
         [0036]    In another embodiment, support member  101  may be made of any water impermeable member. Support member  101  may be adapted so that it has a negligible effect on sediment removal and negligible head loss. 
         [0037]    In another embodiment, support member  101  may comprise a more rigid, even an inflexible, support structure made of metal or plastic that is adapted to allow for the passage of stormwater. 
         [0038]    In still another embodiment, support member  101  may be an inner frame comprised of support rings or rods, or a combination of both. In still another embodiment, support member  101  may be formed as an integral component of filter mat  102 . Support member  101  may be of any suitable shape, and for example, may be round, square, or rectangular in shape. Support member  101  may be made of a corrosion-resistant material, as is well known in the art. Other sizes, shapes, or materials may be used for support member  101  as necessary and/or desired. 
         [0039]    Referring to  FIG. 1B , support member  101  is shown according to another embodiment of the present invention. In this embodiment, support member  101  may be a flexible coil that serves as the foundation for the elongated filtratable element  100 . 
         [0040]    Filter mat  102  serves to filter and trap sediment and other particles in stormwater. In one embodiment, filter mat  102  may comprise a tube of non-woven filtration media that surrounds support member  101 , if provided. In one embodiment, shown in  FIG. 2 , filter mat  102  may be comprised of two parts: backing mesh  202  and fiberglass batting  201 . Backing mesh  202  may include a comparatively course, non-woven plastic support layer, and fiberglass batting  201  may include a plurality of individual fiberglass fibers. 
         [0041]    The use of fiberglass batting  201  provides several advantages. For example, fiberglass batting  201  may be high in surface area, self-cleanable, easily maintained, durable, and economical. 
         [0042]    In order to create filter mat  102 , a plurality of fiberglass fibers, of the same or different diameters and/or lengths, may be attached to backing mesh  202 . In another embodiment, filter mat  102  may be comprised of any natural filaments or synthetic filaments. For example, filter mat  102  may also comprise graphite filaments, metallic filaments, glass filaments, or any other suitable material as necessary and/or desired. 
         [0043]    In one embodiment, filter mat  102  may have a relatively high porosity (i.e., it allows relatively large particles to pass). For example, backing mesh  202  may be comprised of 10-20 cm plastic fibers that form openings of more than about 200 μm, and fiberglass batting  201  may be comprised of less than 1 μm fiberglass fibers that are loosely packed. 
         [0044]    In another embodiment, filter mat  102  may have a relatively low porosity (i.e., it allows only relatively small particles to pass). In this embodiment, backing mesh  202  may be comprised of 10-20 cm plastic fibers that form openings of less than about 200 μm, and fiberglass batting  201  may be comprised of less than 1 μm fiberglass fibers that are tightly packed. 
         [0045]    One of ordinary skill in the art can readily determine appropriate fiber length and percentage of porosity for filter mat  102  depending on the expected stormwater flow rate and sediment particle size. 
         [0046]    Referring to  FIG. 3A , a magnified portion of filter mat  102  is shown, according to one embodiment of the present invention. In one embodiment, individual filter media filaments  301 , made of any suitable material, are attached to backing mesh  202 . In the aggregate, individual filaments  301  comprise fiberglass batting  201 . When filter mat  102  is exposed to stormwater flow, as shown in  FIG. 3B , fiberglass batting  201  may be pressed against backing mesh  202  to create a compact, yet permeable, filter bed. When filter mat  102  is backwashed, as shown in  FIG. 3C  and described in greater detail below, filtrate flows through each filtratable element  100  in the opposite direction, causing filaments  301  of fiberglass batting  201  to be forced away from backing mesh  202 . Backwashing regenerates each element  100  by removing a substantial amount of trapped sediment. 
         [0047]    Referring again to  FIGS. 1A and 1B , according to one embodiment, filter mat  102  may be formed into a tube. Filter mat  102  may be adapted to surround support member  101  so that backing mesh  202  faces or contacts support member  101 . 
         [0048]    In one embodiment, spacers  105  may be disposed between support member  101  and filter mat  102 . Spacers  105  may be used to fasten or attach filter mat  102  to support member  101 . Spacers  105  may also allow for the aqueous portion of the stormwater to freely permeate through filter mat  102 . Spacers  105  may be made of the same material as support member  101 , or any other suitable material. The size, shape, number, and location of spacers  105  may be varied as necessary and/or desired. 
         [0049]    Outer casing  103 , according to one embodiment of the present invention, protects filter mat  102  and fiberglass batting  201  from abrasion. Because stormwater runoff may contain a substantial amount of sediment, it has a tendency to abrade and destroy unprotected filter media as it permeates through. In one embodiment, outer casing  103  may be a wire mesh screen. In another embodiment, outer casing  103  may be a nylon screen. The mesh size of outer casing  103  may be adapted such that the screen does not trap sediment, nor become clogged. One of ordinary skill in the art can readily determine the appropriate mesh size. Further, in addition to protecting filter mat  102  from abrasion, outer casing  103  adds to the stability and strength of the elongated filtratable element  100 . 
         [0050]    In one embodiment, elongated filtratable element  100  may be constructed without outer casing  103 . Under some flow conditions and depending on the amount of sediment expected in the stormwater runoff, outer casing  103  may be unnecessary. Moreover, filter mat  102  may be constructed of a material that reduces the risk of abrasion and eliminate the need for outer casing  103 . One of ordinary skill in the art can readily determine the need for outer casing  103 . 
         [0051]    In one embodiment, support member  101 , filter mat  102 , and outer casing  103  may be coated or treated with an antimicrobial agent. Antimicrobial agents are materials that are able to reduce or eliminate the microbial growth, e.g., bacteria, yeasts, molds. Microbes, if left untreated, may reduce the separation efficiency of filtratable elongated element  100 , and eventually clog the filter media. In one embodiment, chitosan may be introduced into the stormwater or used to coat filtratable element  100  to prevent or reduce microbial degradation. Chitosan causes the fine sediment particles to bind together and may also remove phosphorus, heavy minerals, and oils from stormwater. Other antimicrobial agents may also be used as necessary and/or desired. 
         [0052]    Elongated filtratable element  100  may be adapted to increase the available surface area for removing sediment. In one embodiment, this may involve pleating, crimping, or finning the surface of elongated filtratable element  100 . Other constructions that increase the surface area may be used as necessary and/or desired. 
         [0053]    In one embodiment, elongated filtratable element  100  may be provided with a packing or granular filtration media, for example, sand, polyethylene beads, clay, perlite, etc, in order to adsorb contaminants that might be present in stormwater. 
         [0054]    Referring to  FIGS. 4A and 4B , filtration cartridge  400  is shown, according to embodiment of the present invention. Filtration cartridge  400  may include two general components: central manifold  401  and a plurality elongated filtratable elements  100 . Central manifold  401  may be a deck with a plurality of holes  402 , adapted to receive a plurality of elongated filtratable elements  100 . 
         [0055]    In one embodiment, central manifold  401  may be comprised of an impermeable plastic, and it may be of any suitable shape. For example, central manifold may be round, square, or rectangular in shape. In one embodiment, the shape of central manifold  401  may be selected to correspond to the opening in which it is to be placed. 
         [0056]    In one embodiment, central manifold  401  may also be coated with an antimicrobial agent to prevent unwanted microbe growth, as discussed above. 
         [0057]    Central manifold  401  may include a plurality of holes  402 , with each hole  402  being sized and adapted to receive at least one elongated filtratable element  100 . 
         [0058]    Referring to  FIGS. 5A and 5B , according to one embodiment of the present invention, central manifold  401  of filtration cartridge  400  may have a sidewall with at least one notch  403 . Notch  403  may be provided so that central manifold  401  may be easily fitted into stormwater filtration systems. 
         [0059]    With reference to  FIGS. 1 ,  4 A,  4 B,  5 A and  5 B, each elongated filtratable element  100  may be fitted with a cap  104  for attaching each elongated filtratable element  100  to central manifold  401 . For example, in one embodiment, holes  402  may be sized to hold 1″ diameter elongated filtratable elements  100 . In another embodiment, each hole  402  may be adapted to hold more than one elongated filtratable element  100 . Further, the shape of holes  402  may vary to accommodate differently shaped elongated filtratable elements  100 . 
         [0060]    In one embodiment, holes  402  are open and uncovered so as to reduce the chance of additional clogging. Although, in another embodiment, holes  402  can be provided with a filter, for example, a layer of porous media, to provide an additional filtration. 
         [0061]    In one embodiment, filtration cartridge  400  may include a substantial number of filtration elements  100 . For illustration only, more than 100 elongated filtration elements  100  may be provided. More or fewer filtration elements  100  may be provided. Each elongated filtration element  100  may be about 1″ in diameter, although each filtration element  100  may have a different diameter, length, and/or shape. 
         [0062]    Filtration cartridge  400  may be of any size and shape to accommodate different operating conditions. Filtration cartridge  400  may be assembled such that elongated filtration elements  100  dangle freely from cartridge  400 . Because each elongated element  100  may be flexible and dangle freely from cartridge  400 , filter cartridge  400  may be easily maintained by mechanical means, such as vibration and/or shaking. Moreover, if one elongated filtratable element  100  becomes clogged or damaged, filtration cartridge  401  allows for it to be individually replaced. 
         [0063]    Referring to  FIGS. 6A-6D , a shaking mechanism for filtration cartridge  400  is shown, according to an embodiment of the present invention. In one embodiment, shaking mechanism  600  may be an accessible, manually-operated mechanism that includes a hand crank  601 , a shaft  602 , a base  603 , and a bar  604 . Shaking mechanism  600  may be designed such that it causes at least one filtration cartridge  400  to rotate, thereby removing any trapped sediment from each elongated element  100 . Hand crank  601  may be adapted so that it extends above filtration cartridge  400  and may be easily turned. Turning hand crank  601  causes shaft  602  to rotate base  603 . Bar  604  connects base  603  to a deck in which filtration cartridge  400  may be installed. The rotating motion of filtration cartridge  400  causes the freely dangling elongated filtratable elements  100  to shake, which may remove trapped sediment. In another embodiment, shaking mechanism  600  may be automated. Other shaking and/or vibration mechanisms may be used as necessary and/or desired. 
         [0064]    Referring to  FIG. 7 , a filtration system  700  is shown, according to one embodiment of the present invention. Filtration system  700  may include five general components: a filtration chamber  701 , an inlet line  702 , an inlet device  703 , one or more filtration cartridges  400 , and an outlet line  704 . In general, one or more filtration cartridges  400  may be placed inside filtration chamber  701 . Inlet line  702  introduces stormwater into filtration chamber  701  through inlet device  703 , and outlet line  704  discharges the filtrate. 
         [0065]    In one embodiment, filtration chamber  701  may house a single filtration cartridge  400 . Filtration chamber  701  may either be open to the atmosphere, or it may be enclosed. Further, filtration chamber  701  may either be located above-ground or underground. Filtration chamber  701  may be of any conventional type or shape and may be constructed from steel or plastic, or other material generally resistant to corrosion and heat. 
         [0066]    Filtration cartridge  400  may be flush with the walls of filtration chamber  701  so as to prevent stormwater from seeping upwards between filtration cartridge  400  and filtration chamber  701 . Filtration cartridge  400  may be fitted with a conformable seal to contact the sidewalls of filtration chamber  701  to prevent seepage. 
         [0067]    In another embodiment, filtration chamber  701  may house a plurality of filtration cartridges  400 . One of ordinary skill in the art can readily determine the number of filtration cartridges, and, correspondingly, the number of elongated filtratable elements  100  needed for a given operation. One advantage to filtration chamber  701  having a plurality of filtration cartridges  400  is that more filtration cartridges  400  provides for more filtratable surface area, increasing the operating life of filtration system  700 . In another embodiment, filtration cartridge  400  may be configured or fitted in a different arrangement. For example, filtration cartridge  400  may be adapted to be horizontal or inverted. Further filtration cartridge  400  may be located inside inlet line  702 . Other configurations and locations for filtration cartridge  400  may be used as necessary and/or desired. 
         [0068]    Referring to  FIG. 8 , inlet device  703  is shown, according to one embodiment of the present invention. Inlet device  703  consists of a mesh screen  804 , a deck  805 , a weir  803 , and a base  801 . Base  801  may be comprised of a buoyant, impermeable material. Base  801  may have a hole  807  formed through it to allow stormwater to fill filtration chamber  701 . In another embodiment, base  801  may be made of a porous material instead of having a hole. In one embodiment, weir  803  may be attached to and extend upward from base  801 . Weir  803  may be comprised of a water-impermeable material. Mesh screen  804  may be attached to base  801  and may extend upwardly above and outside of weir  803 . Mesh screen  804  forms a porous wall. In one embodiment, mesh screen  804  may be a wire or nylon mesh screen, with a mesh size that is larger than the expected sediment particle size. Impermeable deck  805  may be attached to mesh screen  804  above the top of weir  803 . Deck  805  forms an impermeable deck and has a small inlet hole  806 , in which stormwater flows through. The stormwater may be introduced from inlet line  702 , through inlet device  703 , and into filtration chamber  701 . In one embodiment, deck  805  may be sloped so that the influent stormwater is directed toward hole  806 . 
         [0069]    Inlet device  703  may be adapted so that it moves with the level of the stormwater in filtration system  700 . During operation, inlet device  703  may be positioned such that the top of base  801  may be level with the bottom of inlet line  702 . In this arrangement, the influent stormwater may be directed into the filtration chamber  701  through hole  807 . Weir  803  may prevent unfiltered stormwater from bypassing inlet device  703 . Weir  803  may also prevent unfiltered stormwater from backing up into inlet device  703 . During high flow events-flooding or thunderstorms-water may pass over inlet device  703 , through mesh screen  804 , and flow downstream, to prevent the filtration system from backing up. 
         [0070]    Referring to  FIG. 9A , inlet device  703  may also be positioned such that deck  805  may be level with the bottom of inlet line  702 . In this arrangement, the influent stormwater flows simultaneously through hole  806  into filtration chamber  701 , and also through mesh screen  804 , through elements  100  and into filtration chamber  701 , thus backwashing elements  100 . Referring to  FIG. 9B , as the level of water in the filtration chamber rises, the inlet device  703  may rise until the top of base  804  may be level with the bottom of influent line  702 . The influent stormwater may be directed into the filtration chamber  701  through hole  807 , and normal filtration operation proceeds. 
         [0071]    In normal operation, stormwater is introduced into filtration system  700  via inlet line  702 . The stormwater flows through inlet device  703  and fills filtration chamber  701 . As filtration chamber  701  fills with water, the aqueous portion of the stormwater permeates through each elongated filtration element  100 . Fiberglass batting  201 , which is exposed to the stormwater, traps a substantial amount of the sediment in the stormwater. As the aqueous portion flows through each elongated filtratable element  100 , fiberglass batting  201  is pressed against backing mesh  202 , forming a permeable filter bed. An impermeable deck  1000  separates filtration system  700  into two parts: a lower housing and an upper housing. After the lower housing of filtration system  700  fills completely with stormwater, influent stormwater accumulates on inlet device  703  creating the driving forces for stormwater to permeate through each elongated filtratable element  100 . The aqueous portion, after permeating through filter mat  102 , travels upward through elongated filtration element  100  and out holes  402  in filtration cartridge  400 . Impermeable deck  100  separates the influent stormwater from the filtrate. The filtrate then flows downstream away from the filtration system  700 . 
         [0072]    Referring to  FIG. 10A , a filtration system with a backwashing mechanism is shown, according to one embodiment of the present invention. In this embodiment, filtration system  700  has an inlet impermeable weir  1001  and an outlet impermeable weir  1002 . In operation, the stormwater flows through an inlet opening created by impermeable weir  1001  and fills filtration chamber  701 . Impermeable weir  1001  separates the influent stormwater from the filtrate. As filtration chamber  701  fills with water, the aqueous portion of the stormwater permeates through each elongated filtration element  100 . The filtrate then accumulates above impermeable deck  1000  until it overflows outlet impermeable weir  1002  and exits system  700 . Outlet impermeable weir  1002  allows for a level of filtrate to accumulate above impermeable deck  1000 . When flow stops, the stormwater that remains in lower chamber of filtration system  700  drains down through infiltration, connection to a dry well, or any other drain-down mechanism. As the water level in the lower chamber drops, the filtrate that is accumulated above impermeable deck  1000  flows downward through each filtration cartridge  400 , backwashing each elongated filtratable element  100  and removing any trapped sediment. 
         [0073]    Referring to  FIG. 10B , in another embodiment, inlet line  702  may feed directly into filtration chamber  701  beneath impermeable deck  1000 . In this embodiment, inlet line  702  would be positioned, in relation to filtration chamber  701 , so that a sufficient hydraulic head is created to cause stormwater to flow through elongated filtratable elements  100  and out outline line  704 . In general, this will require inlet line  702  to be positioned at a height above filtration chamber  701  and outlet line  702 . 
         [0074]    Referring to  FIG. 11 , a filtration system with a backwashing mechanism is shown, according to another embodiment of the present invention. In this embodiment, filtration system  700  has a plurality of filtration cartridges  400  with each cartridge  400  being equipped with its own backwashing valve assembly  1200 . Referring to  FIG. 12A , valve assembly  1200  may generally include five components: a cartridge cover  1201 , a release valve  1202 , a float  1203 , a hole  1204 , and a tether  1205 . In general, valve assembly  1200  enables each elongated filtratable element  100  to be backwashed between rain events in order to remove trapped sediment. 
         [0075]    Cartridge cover  1201  may be adapted so that it sealably and removably covers each filtration cartridge  400  in filtration system  700 . Tether  1205  attaches release valve  1202 , which may be pivotally attached to cartridge cover  1201 , to float  1203 . Release valve  1202  may have a plug that fits into hole  1204 . Valve assembly  1200  has two primary operating positions: a generally closed position, as shown in  FIG. 12A , and an open position, as shown in  FIG. 12B . 
         [0076]    Referring to  FIG. 13 , filtration system  700  is in an operating position where stormwater has completely filled the lower housing and a small amount of filtrate has accumulated above each valve assembly  1200 . In normal operation, not the backwashing operation, release valve  1200  may be slightly forced open by the filtrate flowing upward through filtration cartridge  400  so that filtrate accumulates on impermeable deck  1000  before it flows out of filtration system  700 . In one embodiment, as shown in  FIG. 13 , each valve assembly  1200  may be separated using a partition  1300  so that each filter cartridge  400  may have its own “tank” of filtrate for later use during backwashing. In this embodiment, outlet line  704  (not shown) may be at the level of the top of partition  1300 . 
         [0077]    During normal operation, filtrate flows up through each elongated filtratable element  100  as usual. When the flow of influent stormwater stops, release valve  1202  closes to prevent any of the filtrate that has accumulated on the upper housing of filtration system  700  from draining down through each filtration cartridge  400 . When flow stops, the stormwater that remains in lower chamber of filtration system  700  drains down through infiltration, connection to a dry well, or any other drain-down mechanism. Float  1203  travels downward as the stormwater in the lower housing is drained. When the water level in the lower chamber drops to the desired level, release valve  1202  may be pulled open by float  1203  via tether  1205 . In one embodiment, tether  1205  may be long enough to allow float  1203  to reach a level below each elongated filtratable element  100 . When release valve  1202  opens, the “tank” of accumulated filtrate above each filtration cartridge  400  flushes downward, backwashing each filtratable element  100  and removing any trapped sediment. 
         [0078]    Example. An experiment was conducted using five filtration cartridges, each having eighteen elongated filtratable elements, for a total of 90 elements. Each elongated filtratable element was constructed by wrapping filter mats around a flexible inner core, and enclosing the filter mats in a nylon screen. Each filtratable element was 0.75″ in diameter and 48″ long. The elongated filtratable elements tested had a surface area of about 90 square feet. The filtration cartridges were placed inside a 3′ diameter filtration chamber. With less then 5 inches of headloss, the prototype filtration system was able to remove over 5 kg of sil-co-sil  106  (a standard fine sediment mixture) from the influent water having a flow rate of 1 L/s and a sediment concentration of 300 mg/L. The filter cartridge occupied approximately 1 square foot of area in an impermeable deck separating the unfiltered and filtered water. The effluent water stream had a sediment content less than 20% of the influent concentration. It is reasonable to assume, based on these results, that this type of device could remove fine sediment for the runoff generated by an acre of impervious area, be contained in a chamber less than 10 feet in diameter, and last for over 1 year before the filter had clogged or needed to be replaced. The total suspended solid removal, or sediment removal, efficiency was 90-92%.