Abstract:
A system and related method for separating floating and nonfloating particulate and entrained, suspended, and/or dissolved contaminants from a fluid. The system includes a tank with a lower chamber spaced from an outlet or upper chamber by a confinement deck. The deck includes one or more sockets for receiving one or more filter units for fluid treatment. In addition, the lower chamber of the tank acts as a pretreatment sump to remove floating and nonfloating particulates, thereby reducing the load on the filter units. The filter units are configured for radial and/or upward flow of the fluid from the lower chamber. The filter units may include one or more filter media through which the fluid pass prior to exiting the tank. The filter units include a removable screening retainer for retaining the filter media and/or to screen relatively large contaminants. The filter unit may be removed for ease of tank maintenance and replacement of filter media. The system allows a method of contaminated fluid treatment under varying flow conditions by directing the fluid radially and/or upwardly through the retainer. Establishing both types of flow through the filter unit improves filtering and extends filter life without compromising desired flow through rates.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the priority benefit of U.S. provisional patent application Ser. No. 60/590,776, filed Jul. 23, 2004, entitled “FLUID FILTER SYSTEM AND RELATED METHOD” of the same named inventors. The entire contents of that prior application are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to systems for filtering contaminants from fluids such as drain water and stormwater. More particularly, the present invention relates to a filter system and related method for removing contaminants from a fluid stream by forcing upward and/or radial flow of the fluid through the filter means. 
     2. Description of the Prior Art 
     Fluid transfer systems have been and will remain an important aspect of municipal services and commercial facilities management. The protection of ground water and natural bodies of water requires systems for diverting and/or treating water that contacts roadways, parking lots, and other man made structures. If such diversion or treatment systems are not provided, particulate and contaminants located on or forming part of such structures may be carried by drain water or stormwater to the natural water bodies and contaminate them. Local, state and federal laws and rules require municipalities, businesses, and in some instances, private entities, to establish means to reduce particulate and dissolved pollutant levels permissibly transferred to natural bodies of water from property under their control. Particular requirements may vary from jurisdiction to jurisdiction, but all are likely to become more stringent. 
     Previously, municipal water transfer and treatment facilities provided the only mechanism for diverting contaminated water away from natural bodies of water, either for holding or treatment for subsequent transfer to natural settings. In general, that process involved, and continues to involve, the establishment of a system of drains, such as in a parking lot or at a street curb, by which water enters a system of pipe conduits. Eventually, the water received from the drains reaches either a final outlet destination or is directed to a treatment system for contaminant removal. For purposes of the description of the present invention, “contaminated water” is to be understood to mean any water including floating particulate, such as Styrofoam™ containers and oil, for example; non-floating particulate, such as sand and silt, for example; and suspended and dissolved contaminants, such as fine solids, oil, grease, organic contaminants including fertilizers, herbicides, and pesticides, and metals, for example. 
     Land development produces increased quantities of drain water and stormwater runoff, resulting in increased strain on existing water transfer and treatment infrastructure and an increased likelihood of natural water contamination. In an effort to reduce the impact of development on natural resources and municipal services, initial upstream fluid treatment has become a requirement in many land development, restoration and repair projects. That is, requirements in various forms have been established to ensure that before contaminated water enters the municipal water transfer and/or treatment system or a natural body of water, it must be treated in a manner that reduces the level of contaminants entering the municipal system or the natural body of water. Therefore, most new land development plans and upgrades to existing paved surfaces involve the insertion of a preliminary separation system, generally for connection to the municipal water-handling infrastructure. In other cases, the outflow from the separation system may be transferred directly to a natural body of water. 
     Any preliminary separation system must be designed with the capability to receive fluid flowing in at a wide range of rates. For example, a mild rainfall resulting in rain accumulation of less than 0.25 inches over a span of 24 hours produces a relatively low flow rate through the system. On the other hand, for example, a torrential rainfall resulting in rain accumulation of more than two inches over a span of three hours produces relatively high flow rates through the system. It is desirable, then, to have a separation system capable of handling variable fluid flow rates with reduced likelihood of backup and flooding of the surface above. 
     In addition to having a reasonable fluid flow throughput capacity, the separation system must be capable of performing the separation function for which it is intended. Relatively large floating particulate and relatively heavy non-floating particulate have been, and are, handled in a number of ways. For example, biofiltration swales, settling ponds, fluid/particle density separators, mechanical separators and media absorbers and filters are employed to remove such types of contaminants. Swales and settling ponds take up significant real estate and are therefore generally not particularly desirable in many settings. The separators require less space to operate, but are relatively costly and require considerable servicing on a regular basis. Existing absorbers and filter mechanisms may be effective at removing specified contaminants; however, they tend to do so at the expense of flow through rates. That is, the filtration efficiency is relatively low in comparison to the required water flow through desired. That may be acceptable under relatively low flow rates; but not so under relatively high flow rates. More efficient systems such as the one described in U.S. Pat. No. 5,759,415 issued to Adams on Jun. 2, 1998, assigned to Vortechnics, Inc. and entitled METHOD AND APPARATUS FOR SEPARATING FLOATING AND NON-FLOATING PARTICULATE FROM RAINWATER DRAINAGE, have been developed and employed to treat water in areas where treatment space is limited. However, regulations regarding the removal of suspended/fine solid particulates and/or dissolved and un-dissolved chemical contaminants have resulted in the need for supplemental removal arrangements. 
     There is an increasing need and requirement for separation systems associated with drain water and stormwater introduction to municipal water handling systems and natural bodies of water to remove a substantial portion of all forms of contaminants entering the municipal systems or bodies of water at a point closer to the source. However, it is important that the separation systems not be prohibitively expensive in order to ensure that meeting those needs and requirements is feasible. It is also of importance that such separation systems are relatively easy to maintain. It is becoming increasingly important that these separation systems include means for removing suspended solids and/or chemical contaminants, but without sacrificing the other desired characteristics. Fluid filter systems that are configured to allow for loading of the filter by all floating and nonfloating particulates require maintenance over relatively short intervals. In subsequent fluid treatment cycles, contaminants that remain caked-on the filter surface reduce fluid flow through effectiveness and must therefore be removed relatively frequently. In addition, wet, caked filters are very heavy and therefore require the use of assistive equipment, such as cranes, when they are to be removed for maintenance. 
     Therefore, what is needed is a separation system and related method for removing suspended and/or chemical contaminants from a fluid stream as part of a separation system that may or may not be part of a larger fluid handling system, wherein the separation system is effective in accommodating varied fluid flow rates. What is also needed is such a separation system that is cost effective and configured for ease of maintenance, including, for example, addressing the limitations of contaminant retention on the filter and filter device weight that shorten maintenance cycles and increase maintenance difficulty. Further, what is needed is such a separation system that includes a filter system capable of removing identified contaminants with minimal impact on fluid flow rates. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a separation system that is effective in accommodating varied fluid flow rates. It is also an object of the present invention to provide such a separation system that conforms or substantially conforms with established contaminant removal requirements. Further, it is an object of the present invention to provide such a separation system that is cost effective and configured for ease of maintenance. In that regard, it is an object of the present invention to maximize contaminant retention within the system while minimizing retention on the surface of the filter and to reduce filter device weight at the time of maintenance activities. The separation system preferably includes a filter system capable of removing identified contaminants with minimal impact on fluid flow rates. 
     These and other objectives are achieved with the present invention. The invention is a fluid separation system and related method for removing an array of contaminants from a fluid stream with minimal impact on the passage of the fluid stream through the system. The method involves the transfer of contaminated water through the separation system and the separation of contaminants therein. The separation system includes a filter system arranged to remove suspended and/or dissolved contaminants from the fluid stream. 
     The separation system is preferably established in a treatment chamber having an inlet, an outlet, one or more filter units, and a pretreatment sump referred to herein as a containment chamber. The inlet may be in direct contact with a fluid or it may be connectable to an upstream fluid transfer conduit. The outlet may be in direct contact with a surface water location or it may be connectable to a downstream fluid transfer conduit. If applicable, the upstream fluid transfer conduit and the downstream fluid transfer conduit may be part of a common municipal water handling system. For example, the upstream conduit may be associated with a drain arranged for water on a surface, such as a parking lot surface, to be removed from the surface, and the downstream conduit may form part of the water transfer mechanism designed to divert that water from the drain to a municipal treatment plant or natural surface waters. The separation system of the present invention is designed to remove contaminants from the water before the water reaches the treatment plant or natural surface waters. The containment chamber of the separation system provides a means to remove much or all of the floating and nonfloating particulates from the fluid prior to contacting the filter unit, or alternatively, to allow for sloughing off of some portion of loaded contaminants from the filter unit in a manner that keeps the contaminants away from the filter unit. The filter unit of the present invention is designed for upward and/or radial flow of the fluid into and through the filter unit. That configuration, coupled with the use of the containment chamber, allows sloughing off of bulk contaminants that may be retained thereon when the fluid flow subsides. As a result, the filter unit of the present invention experiences much less contaminant loading over a given period as compared to prior devices that allow for loading of all or substantially all contaminants to the filter system, or that otherwise impose excessive amounts of contaminants on the filter system. As a result, maintenance cycles are lengthened for the separation system of the present invention. The filter unit of the present invention further allows for any filter media contained therein to be released prior to removal of the filter device from the treatment chamber. This allows for simple maintenance without the need for assistive removal equipment. 
     In one aspect of the invention, a separation system is provided for removing suspended and/or dissolved contaminants from a fluid. As noted, the system includes a tank having an inlet, an outlet, a confinement deck, and a containment chamber below the confinement deck and one or more filters removably retained to the confinement deck, wherein the fluid entering the containment chamber through the inlet passes through the one or more filters to the outlet, and wherein the one or more filters are configured to remove a portion or all of the suspended and/or dissolved contaminants in the fluid prior to the fluid passing through to the outlet. The outlet may be part of an outflow chamber above the confinement deck, wherein fluid exiting the one or more filters enters the outflow chamber before passing to the outlet. The outlet may also simply be any sort of container, port, flow conveyance conduit, siphon conduit, opening, or arrangement in direct or indirect fluid communication with the filter unit discharge(s). The confinement deck may include one or more openings to allow fluid entering the containment chamber under excess flow conditions to bypass the one or more filters and pass to the outlet. The openings may include standpipes extending into the containment chamber and into the outflow chamber. The number of filters employed may be selected as a function of desired flow rate and/or contaminant level and/or content of the fluid passing from the inlet to the outlet. The filters include a retainer with a floor and a perimeter retainer wall, either or both of which may be porous, arranged to define an interior retainer space in fluid communication with the outlet of the filter and arranged to allow fluid to flow through the perimeter wall into the interior retainer space. The retainer may include a porous interior conduit spaced within the interior retainer space and in fluid communication with the outlet. In that arrangement, the retainer may retain one or more filter media within the interior retainer space but not within the interior conduit. The filter media may be releasably retained within the retainer. For example, the retainer floor may have one or more media retention plates hingedly affixed to the perimeter retainer wall. The filter unit may also include a housing containing the retainer therein. When a porous retainer perimeter wall is used, the housing is preferably spaced therefrom to allow fluid to flow therebetween. The filter unit with the housing may be configured for the retainer floor to have one or more media retention plates pivotably hinged to the housing perimeter wall. 
     In another aspect of the invention a method is provided for treating a fluid to remove suspended and/or dissolved contaminants therefrom to produce a treated fluid having the suspended and/or dissolved contaminants substantially removed. The method includes the steps of directing the fluid to a confinement chamber of a tank where pretreatment occurs, directing the pretreated fluid to one or more filters, wherein the pretreated fluid passes into each of the one or more filters radially and/or upwardly for treatment to produce the treated fluid, and allowing the treated fluid to pass from the one or more filters to an outlet. Additionally, the method may further include the steps of releasably retaining within one or more of the one or more filters one or more filter media. A method is also provided for removing a fluid, filter media, and/or contaminants from a separation system having a tank with a containment chamber separated from and spaced below an outlet by a confinement deck, wherein the confinement deck includes one or more releasably retained filter units, each retaining therein the filter medium and removably retained, either by positioning within filter unit sockets therein, or by connecting to the confinement deck by other means. The method includes the steps of accessing the containment chamber with removal means, removing a portion or all of the fluid, filter media, and/or contaminants contained within the containment chamber, removing the one or more filter units from the confinement deck, accessing the containment chamber through the filter unit sockets and/or any overflow means or port, such as a standpipe, and removing the remainder of the fluid, filter media, and/or contaminants from the containment chamber. The removal method may also include the steps of releasing the filter media from the filter units prior to the step of accessing the containment chamber with the removal means, inserting new filter media into the one or more filter units released from the confinement deck, and re-inserting the filled filter units into the confinement deck sockets after the step of removing the remainder of the fluid, filter media, and/or contaminants from the containment chamber. 
     These and other features of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the separation system of the present invention, showing a partial cut-away view of the tank to expose the tank interior. 
         FIG. 2  is a perspective view of the interior of the tank of the separation system showing a partial cut-away view of the confinement deck with filter units. 
         FIG. 3  is a close-up perspective view of the confinement deck of the separation system showing the standpipe and two filter units in partial cross-section. 
         FIG. 4  is a perspective view of a cylindrical version of the tank of the present invention. 
         FIG. 5  is an exploded view of the filter unit.  FIG. 5A  is a perspective view of the optional porous interior conduit.  FIG. 5B  is a perspective view of a first retainer floor door.  FIG. 5C  is a perspective view of a second retainer floor door. 
         FIG. 6  is a perspective view of the filter unit of the present invention, showing a portion of the exterior of the retainer. 
         FIG. 7  is a perspective view of the filter unit showing a partial cut-away view of the housing and retainer to show the retainer filled with filter media and showing the interior conduit. 
         FIG. 8  is a simplified elevation view of a cross-section of the filter unit of the present invention. 
         FIG. 9  is a perspective view of the filter unit shown retained in the confinement deck with a partial cut-away view of the housing and retainer. 
         FIG. 10A  is a perspective view of the housing from the top.  FIG. 10B  is a perspective view of the housing from the bottom. 
         FIG. 11  is a cross sectional view of the housing. 
         FIG. 12  is a perspective view of a portion of the separation system of the present invention, showing the interior of the tank including the confinement deck and a plurality of filter units with media retention plates open. 
         FIG. 13  is a perspective view of the separation system of the present invention, showing a partial cut-away view of the tank to expose the tank interior during filter unit removal from the containment chamber. 
         FIG. 14  is a perspective view of the separation system of the present invention, showing a partial cut-away view of the tank to expose the tank interior with filter units removed, and showing the access hatch open for fluid and filter media removal. 
         FIG. 15  is an overhead view of the exterior of the separation tank showing a removed filter unit thereon overturned for filter media filling. 
         FIG. 16A  is a plan view of the separation tank of the present invention showing an alternative containment chamber outlet arrangement.  FIG. 16B  is an elevation view of the separation tank showing the alternative containment chamber outlet arrangement of  FIG. 16A . 
         FIG. 17  is an elevation view of an alternative embodiment of the separation tank including a forebay. 
         FIG. 18A  is a plan view of the separation tank of the present invention showing alternative positioning of the filter units with respect to the confinement deck.  FIG. 18B  is a cross-sectional elevation view of the separation tank showing the alternative filter unit positioning of  FIG. 18A  at section A-A. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A separation system  100  of the present invention is illustrated in the accompanying drawings. As shown in  FIGS. 1-3 , the system  100  includes a tank  110  having an outflow chamber  111  and a containment chamber  112  spaced below the outflow chamber  111  by a confinement deck  200 . The containment chamber  112  includes a tank inlet port  113  through which a fluid to be treated enters the containment chamber  112  from an inlet conduit  120 . The outflow chamber  111  includes a tank outlet port  114  through which a treated fluid exits the outflow chamber  111  via an outlet conduit  130 . The tank  110  also preferably includes an access hatch  115  for accessing the interior of the tank  110  at the outflow chamber  111 , and a manhole  116  with cover  117 . While the preferred embodiment of the present invention describes the separation system  100  with a specific outflow chamber  111  above the confinement deck  200 , it is to be understood that in an alternative embodiment, the fluid may pass from the containment chamber  112  through the one or more filter units to be described herein directly to the outlet conduit  130  or some other form of treated fluid exit means. 
     The tank  110  is preferably made of concrete but may alternatively be fabricated in whole or in parts of metal, plastic, such as fiberglass, or other suitable materials. It may be rectangular, round, oval or other suitable shape. The inlet conduit  120  may be used to connect the tank  110  to an upstream fluid transfer system. Similarly, the outlet conduit  130  may be used to connect the tank  110  to a downstream fluid transfer system. For example, the upstream fluid transfer system may include a drainage system from a roadway or a parking lot, or a preliminary separation system, and the downstream fluid transfer system may include a municipal water treatment plant or natural or artificial surface waters. 
     With continuing reference to  FIGS. 1-3 , the confinement deck  200  includes one or more openings  210  that allow for overflow fluid to pass directly from the containment chamber  112  to the outflow chamber  111  under relatively very high fluid flow conditions. Preferably, the one or more openings  210  retain therein a standpipe  220 . The standpipe  220  also allows excess untreated fluid to pass directly from the containment chamber  112  to the outflow chamber  111  without being treated, for example when fluid flow rates through the inlet conduit  120  are excessively high. However, the standpipe additionally builds driving head on one or more filter units  300  and preferably extends into the containment chamber  112  far enough to ensure that under such conditions, floating contaminants cannot pass directly from the containment chamber  112  to the outflow chamber  111 . The standpipe  220  may also be used as a portal for the removal of fluid and/or particulates from the containment chamber  112  when accessed through the manhole  116 . The confinement deck  200  also includes one or more filter sockets  230  for removably retaining in each one thereof a filter unit  300 . One or more filter clamps  240  are used for that purpose. In general consideration of the intended operation of the separation system  100 , untreated fluid entering containment chamber  112  passes through the one or more filter units  300  where undesirable entrained and/or dissolved matter is filtered out. The treated water then passes out of the filter unit(s)  300  into the outflow chamber  111  from which it exits. While the tank  110  of  FIGS. 1-3  is shown to be rectangular in shape, it is to be understood that the tank may be of another shape, such as cylindrical, as shown by tank  110 ′ of  FIG. 4 . The inlet to a tank such as tank  110 ′ may be arranged to impart a swirling motion of the fluid entering the containment chamber so as to further enhance separation of floating and non-floating matter by directing it to the center of the tank. The advantages of inducing fluid swirl are described in U.S. Pat. No. 5,759,415 issued to Adams on Jun. 2, 1998, assigned to Vortechnics, Inc. and entitled METHOD AND APPARATUS FOR SEPARATING FLOATING AND NON-FLOATING PARTICULATE FROM RAINWATER DRAINAGE. The contents of that patent are incorporated herein by reference. 
     An important aspect of the present invention is the design of the filter unit  300 . With reference to  FIGS. 5-11 , the filter unit  300  preferably includes a housing  301  with a housing lid  302  and a housing perimeter wall  303 . The filter unit  300  further includes a retainer  305  positionable within the housing  301 . The retainer  305  includes a retainer perimeter wall  306 , a retainer floor  307 , and, optionally, a porous interior conduit  308 . The housing lid  302  includes a discharge port  309  at the top surface of thereof. The housing  301  optionally includes one or more lifting handles  310  for insertion and removal of the filter unit  300  with respect to the filter socket  230 . The housing  301  may be fabricated of any material, but is preferably fabricated of a nonmetallic material, such as plastic. The housing lid  302  may be formed integrally with the housing perimeter wall  303 , or it may be removably affixed to the housing perimeter wall  303 . The housing  301  is designed to be easily insertable into and removable from the filter socket  230  of the confinement deck  200  for ease of maintenance of the tank  110  as well as the filter unit  300 . A gasket  304  may be employed to seal the housing  301  to the confinement deck  200 . In an alternative embodiment of the invention, there may be no housing perimeter wall  303 , with the retainer  305  simply affixed to the lid  302  and provided with an outlet for passage of treated fluid either to the outflow chamber  111  or some other fluid transfer means. When in position in the socket  230 , the housing  301  extends into the containment chamber  112 , thereby acting to block floating contaminants from reaching the retainer  305 . However, if there is no housing perimeter wall  303 , such floating contaminants will be retained by the retainer  305 . For purposes of this description, the housing perimeter wall  303  may effectively be the retainer perimeter wall  306  when only up flow of the fluid is desired. 
     The retainer perimeter wall  306  and the floor  307  define an interior retainer space  319  into which fluid to be treated passes. The interior retainer space  319  is in fluid communication with the outlet  114  of the tank  110 . The retainer perimeter wall  306  of the retainer  305  preferably includes an upper retainer wall flange  311  for affixing the perimeter wall  306  to the housing lid  302 . For upflow of fluid into the retainer  305 , the floor  307  is porous. For radial flow into the retainer, the retainer perimeter wall  306  is porous. In particular, in order to maximize fluid flow conditions, the retainer perimeter wall  306  is porous and is spaced from the interior of the housing perimeter wall  303  to create a space for fluid to enter the housing around the perimeter of the retainer  305  prior to entering it through the retainer perimeter wall  306 . If upflow and radial flow are desired, the retainer perimeter wall  306  and the floor  307  are both porous. The porous interior conduit  308  is only required if one or more filter media are employed to remove contaminants. When in use, the porous interior conduit  308  of the retainer  305  includes a conduit mounting flange  312  for affixing the porous interior conduit  308  to the housing lid  302  preferably approximately centered in relative position to the discharge port  309  of the housing lid  302 . Thus, in this embodiment of the filter unit  300 , the retainer perimeter wall  306  and the interior conduit  308  are not connected together but are instead separately connected to the housing lid  302 . The retainer perimeter wall  306 , the floor  307 , and the interior conduit  308  may be fabricated of metallic or nonmetallic material. When made porous, they may be made as perforated, corrugated, or pleated screening elements, or other configuration as selected by the user. 
     With continuing reference to  FIGS. 5-11 , the interior of the housing perimeter wall  303  preferably includes a means for releasably retaining thereto a rotatable release rod  316  that extends through a housing lid hole  315  of the housing lid  302 . The means for releasably retaining may be a retaining clip (not shown) to which the release rod  316  may be clipped and allowed to rotate therein. The rotatable release rod  316  terminates at a first end thereof with a release handle  317  adjacent to the housing lid  302 , and at an opposing second end thereof in a retention leg  318 . The retention leg  318  is designed to fix the retainer floor  307  in a first position when the filter unit  300  is operational, and in a second position when the filter unit  300  is undergoing maintenance. The retention leg  318  may be rotated between the first and second positions by rotating the release handle  317 . 
     As noted, the space defined by the retainer perimeter wall  306 , the optional interior conduit  308  if used, and the retainer floor  307  defines the interior retainer space  319  within which one or more filtering media  320  may be located. The one or more filter media may include perlite, zeolite, granular activated carbon, peat, or other suitable filter media selectable as a function of the contaminants to be removed. The filtering media  320  are preferably selected for their effectiveness in removing entrained and/or dissolved matter from the fluid to be treated, but that allow the fluid to pass from the outside of the retainer  305  to the interior of the interior conduit  308  at specified flow conditions. Combinations of different filter media may be employed based on porosity, contaminant affinity, and the like. Such combinations may be mixed or layered, either vertically or horizontally. The porosity of the retainer perimeter wall  306 , the retainer floor  307 , and the interior conduit  308  must also be designed with both objectives in mind. In some instances, tightly packed filter media and/or relatively small pore sizes for the retainer  305  may be required or desired, whereas in other instances, loosely packed and/or large pore sizes for the retainer  305  may be required. It is to be noted that the retainer  305  may be used without any filter media  320  in those situations where it acts as a gross filtering device for separating relatively large particulates from the fluid prior to entering the outflow chamber  111  (or other form of outlet arrangement). In an arrangement in which there are no filter media  320  used, the interior conduit  308  is not required and the retainer  305  simply includes the retainer perimeter wall  306  and the retainer floor  307 . In an arrangement in which the filter media  320  are used in an up flow only system, a top screen may be used to block the filter media  320  from escaping into an exit space  360  prior to discharge, wherein the top screen and exit space  360  effectively act as an interior conduit. 
     An important aspect of the design of the retainer  305  for the purpose of maintaining the filter unit  300  as well as the system  100  is the arrangement of the retainer floor  307 . As shown in  FIG. 5 , the retainer floor  307  is preferably a hinged structure and more preferably, a center-hinged structure. The retainer floor  307  includes a pivot shaft  321 , a first media retention plate  322  hingedly connected to the pivot shaft  321 , and a second media retention plate  323  hingedly attached to the pivot shaft  321 . Each of media retention plates  322  and  323  includes a perforated or porous body  325  and an optional outer flange  326 . The media retention plates  322  and  323  are selected and designed to provide structural support for any filter media to be retained by the retainer  305 , and to withstand the hydrostatic pressure to be experienced when the filter unit  300  is in use. The pivot shaft  321  pivots and is retained in openings  328  of the housing perimeter wall  303 . The retainer floor  307  may be fabricated of metallic or nonmetallic material. In an arrangement where there is no housing  301  but only retainer  305 , the media retention plates  322  and  323  may be retained in place by inserting the pivot shaft  321  into opposing holes of the retainer perimeter wall  306 . In that arrangement, the release rods  316  and the release handles  317  may be employed to releasably retain the media retention plates  322  and  323  in place until the filter media are to be released. Further, if there are no filter media  320  to be used, the hinged media retention plates  322  and  323  are unnecessary and the retainer floor  307  may be releasably or permanently affixed to the retainer perimeter wall  306 . 
     In operation, the system  100  enables the removal of undesirable matter from the fluid stream during the fluid&#39;s passage from the inlet conduit  120  to the outlet conduit  130 . Untreated fluid  330  entering the containment chamber  112  fills that containment chamber  112  and reaches the underside of the filter unit  300  during which time floating and non-floating contaminants are separated from the pretreated fluid reaching the underside of the filter unit  300 . This produces hydrostatic pressure on the filter unit  300 , thereby forcing the pretreated fluid into the retainer  305 . Preferably, floating and non-floating contaminants of relatively large size remain trapped in the containment chamber  112  by the housing  301 , the retainer perimeter wall  306 , the standpipe  220  or any combination of one or more thereof. As shown in  FIGS. 3 and 8 , the pretreated fluid  330  enters the housing  301  through the retainer floor  307 . As hydrostatic pressure increases on the filter unit  300  with the filling of the containment chamber  112 , the pretreated fluid  330  moves into radial flow space  340  between the housing perimeter wall  303  and the retainer perimeter wall  306 . The pretreated fluid  330  enters space  319  by way of both the retainer perimeter wall  306  via radial flow space  340  and directly through the perforated body  325  of the retainer floor  307 . If there are no filter media  320  in space  319 , the fluid-under-treatment  350  passes directly through the space  319  before exiting the discharge port  309  into the outflow chamber  111 . It is anticipated that entrained relatively larger particulates will be trapped by either or both of the retainer perimeter wall  306  and the retainer floor  307 . If there are filter media  320  in space  319 , the fluid-under-treatment  350  dwells in space  319  for trapping entrained, suspended, and/or dissolved contaminants before passing through interior conduit  308  into exit space  360  and exiting the discharge port  309  into the outflow chamber  111 . When the pretreated fluid  330  in the containment chamber  112  recedes, contaminants trapped on the exterior of the retainer  305  and/or the housing  301  are more likely to drop back into the containment chamber  112  rather than remain caked on. This enhances the chance of the filter unit  300  remaining sufficiently clear to conduct subsequent filtering operations without the need to halt the fluid transfer process for filter unit  300  maintenance. 
     As illustrated in  FIGS. 12-15 , the design of the system  100  of the present invention enables effective treatment of a fluid as well as ease of maintenance of the system  100  itself. The process of maintaining the system  100  when the filter media  320  are in use includes the step of releasing either or both of retainer media retention plates  322  and  323  to allow the filter media  320  to fall into the containment chamber  112 . That releasing step may be accomplished by rotating the release handles  317  to the second position to allow the hinged media retention plates  322  and  323  to pivot about the pivot shaft  321 . If no filter media are used, this step may be omitted and, in fact, hinged media retention plates  322  and  323  are not required as there is no need to remove filter media  320  therefrom. In the next step, pretreated fluid, trapped contaminants, and any released filter media are removed from the containment chamber  112  using removal means, such as vacuum means, to draw out the pretreated fluid, trapped contaminants, and any released filter media. This removal may be achieved by inserting the removal means into the manhole  116  and through the standpipe  220 , or port  210  if there is no standpipe  220 . Either while undertaking the removal step or thereafter, the one or more filter units  300  retained to the confinement deck  200  in filter sockets  230  may be removed by releasing filter unit clamps  240 , shown in  FIGS. 1 and 12 , fixed against the housing lid  302  (or by other means of connection to the confinement deck) and removing the filter units  300  from the confinement deck  200 , preferably using lifting handles  310 . The filter units  300  in situ may be accessed via access hatch  115 . This method of removing the filter media  230  from the retainer  305  prior to removing the filter unit  300  substantially reduces the weight of the filter unit  300  to be maintained, thereby allowing such removal without using assistive mechanical equipment, such as a crane. 
     Upon removal of the one or more filter units  300  from the confinement deck  200 , the same or additional removal means may be used to remove untreated fluid and/or filter media from the containment chamber  112 . That additional removal step may be achieved by inserting the removal means into the access hatch  115  and through the one or more sockets  230  to access substantially all of the interior of the containment chamber  112 . As shown in  FIG. 15 , the removed filter unit  300  may be inverted such that it rests on housing lid  302 . A new batch of filter media may be inserted into space  319  via either or both of open media retention plates  322  and  323 . The door(s)  322  and/or  323  may then be closed by rotating the release handles to the first position to clamp the door(s)  322  and/or  323  into the retained position(s). The filled and closed filter unit(s) may then be re-installed in the confinement deck  200 , the access hatch  115  closed, and the system  100  made available for treating the fluid. 
     An additional optional step of the filter method of the present invention involves draining down the fluid within the containment chamber  112  to keep the filter media  320  relatively dry under low or no flow conditions in the containment chamber  112 . For that step, a containment chamber outlet  400  is positioned in the containment chamber  112  as shown in  FIGS. 16A and 16B . The containment chamber outlet  400  also acts as the outlet for the outflow chamber  111  via outlet port  401  that provides fluid communication from the outflow chamber  111  to the containment chamber outlet  400  through confinement deck  200 , effectively replacing outlet conduit  130 . An optional containment chamber downspout  402  may be included in that arrangement to trap floating particulates while allowing fluid to pass from the containment chamber  112  to the outlet  400 . Flow control means such as perforations  403  of the downspout  402  enable regulation of the flow of fluid out of the filter unit(s)  300  when flow into the containment chamber  112  subsides. In operation, the system of  FIGS. 16A and 16B  allows pretreated fluid to flow into the containment chamber  112  as previously described. The standpipe  220  also allows for pretreated fluid under relatively higher flow conditions to bypass the fluid unit(s)  300 , also as previously described. However, the outlet  400  in the containment chamber  112  positioned below the underside of the confinement deck  200  ensures that the standing fluid surface in the containment chamber  112  is below the bottom of the filter media  320 . If there is a housing  301 , the outlet  400  is preferably positioned so that the standing fluid surface is just below the bottom of the filter media  320  but just above the bottom of the housing  301 . This arrangement keeps previously separated floatables confined in the containment chamber  112  and away from the filter media  320 . Treated fluid passing through the filter unit(s)  300  exit the discharge  309 , passes along the upper side of the confinement deck  200 , and then drops down into the outlet port  401  to the containment chamber outlet  400  for discharge. 
     Another alternative arrangement of the system  100 ″ shown in  FIG. 17  includes a pre-treatment forebay  500  to isolate the tank inlet conduit  120  from the containment chamber  112 ″ when the outlet conduit  130  cannot be positioned above the inlet conduit  120 , or when confinement of gross pollutants away from the filter units  300  is desired. In that situation, the forebay  500  is partially spaced from the containment chamber  112 ″ by a baffle  501 , and completely isolated from the outflow chamber  111 ″ by tank wall  502 . A forebay outlet conduit  503  provides the passageway for fluid entering the forebay  500  to enter the containment chamber  112 ″ via intermediate space  504  that forms part of the containment chamber  112 ″ when the fluid reaches and exceeds the standing fluid level  505 . The inlet of the forebay outlet conduit  503  is submerged and sealed to the baffle  501  such that floatables are retained in the forebay  500 . Under very high flow conditions, the fluid rises to the level of the top of the baffle  501  and drops over it into the intermediate space  504  without reaching the outflow chamber  111 ″. The baffle  501  also retains floating particulates, at least until the fluid flow rate causes the fluid level in the forebay  500  to exceed the top of the baffle. From there, the untreated fluid is subject to the same filtering process previously described. It is preferred for this arrangement that a forebay manhole  506  be provided directly over the forebay  500  to allow for removal of excess contaminants without directly reaching the containment chamber  112 ″. Although not shown, the tank  110 ″ of system  100 ″ may include a standpipe for bypass, also as previously described. 
     An alternative arrangement of the filter units  300 ′ with respect to a modified confinement deck  200 ′ is shown in  FIGS. 18A and 18B  as part of tank  600 . The filter units  300 ′ are positioned substantially in the outlet chamber  111  rather than substantially in the containment chamber  112 . Each of the filter units  300 ′ is in fluid communication with pretreated fluid of the containment chamber  112  through a filter port  601 . Each filter port  601  is preferably sealed such that pretreated fluid only enters the filter unit  300 ′ therethrough. The filter units  300 ′ include modified housings  301 ′ including a housing perimeter  306 ′ and a housing floor  307 ′. The housing floor  307 ′ includes a port  350  in fluid communication with the confinement deck port  601  that is configured to ensure that the pretreated fluid entering the filter units  300 ′ is forced to pass into filter area  320  for either or both of upward and radial flow. The filtering of the fluid upon entering the filter unit  300 ′ is achieved in the manner previously described with respect to filter unit  300 . The alternative arrangement of tank  600  enables the placement of more filter units  300 ′ in a defined area, it limits wetting of the filter media when the fluid subsides, and the sealing of the filter units  300 ′ with respect to the confinement deck  200 ′ may be easier to achieve. The filter units  300 ′ may include a filter outlet extension  360  to assist in drawing treated fluid out of the filter units  300 ′. 
     It is to be understood that the above-described steps are intended to represent primary aspects of the invention and that additional steps may be implemented. Further, the order of the steps illustrated as part of the process is not limited to the order described herein, as the steps may be performed in other orders, and one or more steps may be performed in series or in parallel to one or more other steps, or parts thereof. Additionally, in an alternative embodiment of the filter unit  300 , the retainer  305  is the only component of the filter unit  300  that is removable, whereas there is either no housing  301  and the retainer  305  is affixed directly to the confinement deck  200 , or the housing  301  is permanently affixed to the confinement deck  200 . 
     While the present invention has been described with particular reference to certain embodiments of the separation system, it is to be understood that it includes all reasonable equivalents thereof as defined by the following appended claims.