Patent Publication Number: US-2019177184-A1

Title: Fluidized bed media contact chamber

Description:
RELATED APPLICATIONS 
     The application claims priority to U.S. Provisional Application No. 62/377,327, filed on Aug. 19, 2016, which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to a fluidized bed media contact chamber. Such contact chambers, which are sometimes referred to as reaction chambers or reactors, are used to pretreat fluid prior to the fluid&#39;s end use, which may include consumption (e.g., as drinking water) or introduction of the fluid into a downstream system. Examples of downstream systems include, without limitation: the plumbing of a building; a reverse osmosis (RO) system; a water heater; a boiler; and a humidifier. The treated fluid may reduce adverse effects (e.g., scale buildup or corrosion) on such downstream systems. In some applications, the contact chamber may be integrated with the downstream system. 
     Within the contact chamber is a fluid treatment media which treats the fluid in desired ways, but usually by ion exchange or catalytic treatment. Consequently, the fluid treatment media discussed in this specification can be characterized as media that engages in ion exchange or catalytic treatment with the fluid it contacts. For example, some types of fluid treatment media (referred to as scale control media) are used to reduce the formation of scale in a downstream system. The fluid treatment media may be provided in a variety of natural and synthetic materials, which are often provided in the shape of beads. One example of a fluid treatment media is a resin useful for reducing scale. 
     SUMMARY 
     The disclosure provides a contact chamber in which a bed of fluid treatment media is fully fluidized by using a fluidizer. The fluidizer may be, for example, an internal or external eductor that acts as a pump for a media and fluid mixture to boost fluid flow and generate recirculation that keeps the media suspended in the fluid or an arrangement of nozzles, mixing blades, pumps, baffles, or irregular cross-sectional shapes (or combinations of any of these) to promote fully fluidizing the media in the chamber and causing the media to recirculate within the chamber. 
     Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a conventional contact chamber set up for relatively low fluid flow rates, the contact chamber being in a low flow condition. 
         FIG. 2  illustrates a conventional contact chamber set up for relatively high fluid flow rates and in an at-rest condition. 
         FIG. 3  illustrates the contact chamber of  FIG. 2  in a high flow condition. 
         FIG. 4  illustrates a conventional contact chamber in a fully fluidized condition. 
         FIG. 5  illustrates a contact chamber modified with a fluidizer to promote full fluidization of the media according to some constructions. 
         FIG. 6  illustrates a section view of the contact chamber of  FIG. 5  taken along the line  6 - 6 . 
         FIG. 7  illustrates an enlarged view of a portion of  FIG. 6 . 
         FIG. 8  illustrates a contact chamber modified with a fluidizer to promote full fluidization of the media according to another construction. 
         FIG. 9  illustrates a section view of the contact chamber of  FIG. 8  taken along the line  9 - 9 . 
         FIG. 10  illustrates an enlarged view of the fluidizer of  FIG. 9 . 
         FIG. 11  illustrates a contact chamber modified with a fluidizer to promote full fluidization of the media according to another construction. 
         FIG. 12  illustrates a section view of the contact chamber of  FIG. 11  taken along the line  12 - 12 . 
         FIG. 13  illustrates an enlarged view of the fluidizer of  FIG. 12 . 
         FIG. 14  illustrates a contact chamber modified with a fluidizer to promote full fluidization of the media according to another construction. 
         FIG. 15  illustrates an exploded view of the contact chamber of  FIG. 14 . 
         FIG. 16  illustrates a detail view of a fluidizer for use with the contact chamber of  FIG. 14 . 
         FIG. 17  illustrates an enhanced recirculating contact chamber having an external eductor. 
         FIG. 18  illustrates a contact chamber according to the present disclosure including a plurality of external mixing nozzles. 
         FIG. 19  illustrates a contact chamber according to the present disclosure including a plurality of internal mixing nozzles. 
         FIG. 20  illustrates a contact chamber according to the present disclosure including mechanical mixing and recirculation. 
         FIG. 21  illustrates a contact chamber according to the present disclosure including an internal pump. 
         FIG. 22  illustrates a contact chamber according to the present disclosure including an external pump. 
         FIG. 23  illustrates a contact chamber according to the present disclosure including a plurality of baffles. 
         FIG. 24  illustrates a contact chamber according to the present disclosure having an irregular shape. 
         FIG. 25  is a graph of the efficacy, in terms of maintaining the production water flow rate, of a reverse osmosis (RO) system receiving water from a conventional contact chamber compared to that of an RO system receiving water from a contact chamber according to the present disclosure. 
         FIG. 26  is a graph of the efficacy, in terms of maintaining the ion rejection percentage, of a reverse osmosis (RO) system receiving water from a conventional contact chamber compared to that of an RO system receiving water from a contact chamber according to the present disclosure. 
         FIG. 27  is a graph demonstrating the efficacy of the present disclosure for scale prevention in water heaters. 
     
    
    
     DETAILED DESCRIPTION 
     Before any constructions of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other constructions and of being practiced or of being carried out in various ways. 
     Conventional Contact Chambers 
     The term “conventional contact chamber” is used to describe a contact chamber through which a fluid (e.g., water) flows in a single pass without substantial change in velocity or intentional recirculation of the fluid within the contact chamber. Such conventional contact chambers are usually defined within a cartridge that includes a fluid inlet and a fluid outlet that communicate with the contact chamber. Fluid flows through the fluid inlet into the contact chamber at an inlet flow rate and flows out of the contact chamber through the fluid outlet at an outlet flow rate. The inlet flow rate and outlet flow rate are usually equal because the fluid entering the contact chamber through the fluid inlet displaces an equal volume of fluid out of the contact chamber through the fluid outlet. Within the conventional contact chamber is a bed of fluid treatment media (referred to simply as the “media”). The media engages in ion exchange with or catalytic treatment of the fluid flowing through the contact chamber. 
     The media is most effective (i.e., catalytic effect or ion exchange is improved) when the media is fluidized. The term “fluidized” and its variations means that the media is suspended in the fluid within the contact chamber. The media can be said to be “fully fluidized” when all media in the bed is suspended in the fluid. Fully fluidized media maximizes the contact and interaction (such as mass transfer) between the fluid and the media for most efficient use of the media in a conventional contact chamber. Conventional contact chambers are designed for a fixed or narrow range of fluidic conditions (e.g., fluid temperature, media size, media weight or density, bed height, bed void volume, total mass of solids in the bed, and fluid flow rate). Only if the fluidic conditions are met will the media be fully fluidized. 
     A common fluid treated with a conventional contact chamber is water. One aspect of the fluidic conditions—flow rate—can be widely variable for water in many environments. In a residential application the water flow rate can vary 0-10 gpm. Thus a conventional contact chamber may be ineffective over much of the range of water flow rates it will experience in operation. 
     For example, media with a bead size of 0.3-1.1 mm and density of 7.7 g/liter can be fully fluidized in a 23.5 cm height conventional contact chamber with 5 cm media bed depth when operated with the water at a temperature of 20° C. flowing vertically upwards at a velocity of 132 cm/min. If the water velocity is less than about 42 cm/min with 5 cm media depth, the bed does not fully fluidize; the vertical lift caused by the fluid friction is not enough to overcome gravity and much of the media remains packed in the bottom of the contact chamber. This can be referred to as the low flow case. Under 25 cm/min flow speed, the media does not expand at all. If the velocity is greater than 160 cm/min under these conditions the media bed is only partially fluidized; the vertical lift caused by the fluid friction is too high and overcomes gravity, resulting in much of the media being trapped at the top of the contact chamber and forming a packed bed. This can be referred to as the high flow case. 
       FIG. 1  illustrates a conventional contact chamber  10  set up for relatively low fluid flow rates. The contact chamber  10  is defined within a cartridge  14  having a feed fluid inlet  18  at one end and a treated fluid outlet  22  at an opposite end. The feed fluid inlet  18  and treated fluid outlet  22  both communicate with the contact chamber  10 . The contact chamber  10  is illustrated as being vertically-extending with the feed fluid inlet  18  at the bottom and the treated fluid outlet  22  at the top. The contact chamber  10  is always illustrated in this orientation throughout this specification for consistency. In some constructions and applications, however, the contact chamber  10  may be positioned in other attitudes or orientations; the disclosure is not limited to the vertical orientation illustrated. 
     A bed of media  26  is deposited at the bottom of the contact chamber  10 . The media bed is relatively short, shallow, or small because a relatively low fluid flow rate is expected. Such low fluid flow rate gives rise to only sufficient friction and lift to fully fluidize a relatively small amount of media  26 . Also, the slower-moving fluid will have more time to interact with each media particle or bead, so a relatively small amount of media  26  can adequately treat the fluid moving at a relatively lower rate. 
     The fluid flows in an upward direction  30  from the feed fluid inlet  18 , through the media  26 , to the treated fluid outlet  22 . The media  26  is more dense than the fluid and therefore settles to the bottom of the contact chamber  10  in the absence of sufficient upward fluid flow. In other constructions, the media  26  may be of lower density such that the media beads are buoyant in the fluid. In such instances, the fluid flow may be directed downwardly into the contact chamber  10  (i.e., the contact chamber  10  and plumbing are flipped upside down from what is illustrated in the examples of this specification), or the contact chamber  10  may be mounted horizontally, relying on the higher velocity provided by recirculation to fluidize the media  26 . 
     Plastic mesh  34  may be provided at each end of the contact chamber  10 . The mesh  34  size is smaller than the media  26  to prevent the media  26  from escaping the contact chamber  10  through the feed fluid inlet  18  and treated fluid outlet  22 . Alternatively, screens, strainers, open cell foam or fiber pads may be used to prevent the media from escaping the contact chamber through the feed fluid inlet  18  or treated fluid outlet  22 . Inlet check valves, or inlet isolation valves may also be used to prevent the media  26  from leaving the contact chamber  10  through the feed fluid inlet  18 . A gasket, O-ring, thread, or compression fitting may be provided at either or both ends to ensure a fluid-tight seal with the fluid supply to the feed fluid inlet  18  or the downstream system. 
       FIG. 2  illustrates a conventional contact chamber  10 ′ set up for relatively high fluid flow rates. The contact chamber  10 ′ is the same as in  FIG. 1 , but the media bed is much higher than the media bed illustrated in  FIG. 1  because of the expected high fluid flow rate. Like parts in the construction of  FIG. 2  will be indicated using the prime symbol (“′”). With higher flow rates, there is less contact time between the media  26 ′ and the fluid and more media  26 ′ is required to achieve the desired treatment. In this regard, conventional contact chambers are tuned for the expected flow rate by adjusting the size or height of the media bed to reflect the contact time the fluid is expected to have with the media. More media is used since the expected contact time decreases (i.e., as the expected fluid flow rate increases). 
     As noted, the contact chambers  10  and  10 ′ illustrated in  FIGS. 1 and 2  are set up for an expected low or high fluid flow rate, respectively. The performance of the contact chamber  10 ,  10 ′ is optimized (i.e., the media  26 ,  26 ′ is fully fluidized) when the fluid flow is within a given range around the expected flow rate. When fluid flow rates are outside of the given range, dead zones  38 ,  38 ′ (i.e., bands of media-free fluid) are formed in which the media  26 ,  26 ′ is not fluidized. The fluid is not being treated in the dead zones  38 ,  38 ′ and the contact time of fluid and media  26 ,  26 ′ is shortened to a non-optimal level. 
     In a low flow condition (i.e., when the fluid flow rate is lower than the optimum range), the media  26 ,  26 ′ may not be fluidized throughout the entire contact chamber  10 ,  10 ′. The media  26 ,  26 ′ may only be lifted part way up the height of the contact chamber  10 ,  10 ′. In such conditions, the area above the fluidized media is a dead zone  38 ,  38 ′. 
       FIG. 3  illustrates the conventional contact chamber setup of  FIG. 2  in the high flow condition (i.e., when fluid flow exceeds the optimum range). As illustrated, a portion of the media  26 ′ is compacted against the top of the contact chamber  10 ′ by the higher-than-optimum flow rates. A remaining portion of the media bed is fluidized at the bottom portion of the contact chamber  10 ′. A dead zone  38 ′ forms between the fluidized media  26 ′ at the bottom and the non-fluidized media  26 ′ at the top. 
       FIG. 4  illustrates a conventional contact chamber  10 ,  10 ′ in a fully fluidized condition. Here it can be seen that the media bed is dispersed throughout the entire volume of the contact chamber  10 ,  10 ′. This achieves maximum interaction between the media  26 ,  26 ′ and the fluid. 
     An example of fluid treated by the illustrated conventional contact chambers of  FIGS. 1-4  is water, and an example of media is scale control media. The scale control media may be, for example, a resin. There are many other types of media used for treating water and other fluids, and the present disclosure is not limited to scale reduction applications. 
     Improved Contact Chamber 
     One aspect of the present disclosure is to provide a fluidizer which achieves full fluidization of a bed of media over a wider range of flow rates compared to a conventional contact chamber. Another aspect of the present disclosure is to provide a fluidizer which achieves full fluidization of a wider range of media bed depths for a given flow rate compared to a conventional contact chamber. Yet another aspect of the present disclosure is to provide a recirculation enhancing contact chamber (RECC) which promotes recirculation of fluid in the contact chamber. The term “recirculation” is used to refer to the media in the contact chamber moving in a direction opposite the main flow of fluid in the contact chamber and thereby resulting in more time for the media particles to interact with the fluid and rub against other media particles. 
     In the case where the media is used for scale control purposes, the shearing forces arise from the media particles rubbing against each other, and the shearing forces cause crystals to break off of the media particles and become suspended in the fluid. Shearing crystals off of the media particles regenerates the media in the sense that nucleation sites are re-opened on the media. Additionally, the suspended crystals continue to offer nucleation sites. In summary, recirculation can give rise to much more interaction of the media with the fluid than the single-pass flow profile of a conventional contact chamber. 
     In the example of water as the fluid and scale control media as the media, the scale control media absorbs calcium and carbonate ions from the water, forming crystals of calcium carbonate on the surface of the media. Additionally, scale that is formed after treatment through the system is typically of a different crystal structure—aragonite form instead of calcite form—which is less adherent onto surfaces in downstream systems. 
       FIGS. 5-7  illustrate a cartridge  62  including a feed fluid inlet  66  and a treated fluid outlet  70  and defines a contact chamber  74 . The feed fluid inlet  66  may be adapted to engage a fluid inlet conduit  78  for receiving inlet fluid from a source. The treated fluid outlet  70  is adapted to engage a fluid outlet conduit for transferring treated fluid to a downstream application. The contact chamber  74  includes a fluidizer  82 , a lower mesh layer  86 , a deflector cap  94 , and media. The lower mesh layer  86  is positioned near the feed fluid inlet  66  to prevent media from entering the feed fluid inlet  66 . In some constructions, an upper mesh layer (not shown) may be positioned near the treated fluid outlet  70  to prevent media from entering the treated fluid outlet  70 . In other constructions, the deflector cap  94  includes openings  90  sized to allow treated fluid to flow to the outlet  70  while preventing the media from entering the treated fluid outlet  70 . The deflector cap  94  may be positioned at the top of the contact chamber  74  to deflect fluid downwardly to promote recirculation. 
     As shown in  FIGS. 6-7 , the fluidizer  82  is an eductor including a nozzle  106 , a venturi tube  110 , and one or more suction openings  114  positioned between the nozzle  106  and the venturi tube  110 . As is best shown in  FIG. 7 , in the illustrated construction, the nozzle  106  includes an upper portion  118 , a seat  122 , a lower portion  126 , and a tapered interior cavity  130 . The nozzle  106  is positioned between the feed fluid inlet  66  and the fluid inlet conduit  78  so that the tapered interior cavity  130  is in fluid communication between the fluid inlet conduit  78  and the cartridge  62 . As shown in  FIG. 7 , the lower portion  126  of the nozzle  106  is positioned within the fluid inlet conduit  78 . The tapered cavity  130  is dimensioned so that the nozzle  106  increases a flow rate of fluid flowing into the contact chamber  74 . For example, in the illustrated construction, a cross-sectional area of the tapered cavity  130  is widest proximate the feed fluid inlet  66  and decreases so that the cross-sectional area is smallest proximate the contact chamber  74 . In the illustrated construction, the seat  122  is positioned between the fluid inlet conduit  78  and the feed fluid inlet  66 . In the illustrated construction, the lower portion  126  of the nozzle  106  includes external threads  134  proximate the seat  122 . The external threads  134  engage internal threads of the fluid inlet conduit  78 . In other constructions, the nozzle  106  may be engaged with the fluid inlet conduit  78  using other methods, such as a compression fitting, an adhesive, or sealing devices such as o-rings. In the illustrated construction, o-rings  138  are used to form a fluid-tight seal between the nozzle  106  and the feed fluid inlet  66 . In other constructions, the nozzle  106  may be secured to cartridge  62  using a threaded connection, a friction fit, or an adhesive. 
     As shown in  FIG. 7 , a suction zone  142  of the fluidizer  82  is generated or established between the nozzle  106  and the venturi tube  110 . In the illustrated construction, the suction zone  142  is established or generated between an inner protrusion  146 , the venturi tube  110 , and the bottom of the cartridge  62 . The inner protrusion  146  extends upwardly (e.g. into the contact chamber  74 ) from the bottom of the cartridge  62  and is adapted to engage the venturi tube  110  as is described in more detail below. A plurality of suction openings  114  is formed around the circumference of an upper portion of the inner protrusion  146 . In some constructions, an outer protrusion  150  may surround the inner protrusion  146 . In such constructions, a plurality of ribs  154  extends between the inner protrusion  146  and the outer protrusion  150 . In such a construction, the suction openings  114  are formed between pairs of ribs  154 . The inner protrusion  146  and the outer protrusion  150  may be substantially circular and concentric with respect to each other and with respect to the nozzle  106 . 
     With continued reference to  FIG. 7 , the venturi tube  110  includes a venturi tube inlet  158 , a venturi tube outlet  162 , a cavity  166 , and a cartridge engagement portion  170 . The cavity  166  includes a first tapered portion  174 , a choke portion  178 , and a second tapered portion  182 . In the illustrated construction, the first tapered portion  174  extends between the venturi tube inlet  158  and the choke portion  178 . The first tapered portion  174  is dimensioned so that a cross-sectional area of the first tapered portion  174  is the widest proximate the venturi tube inlet  158  and the cross-sectional area of the first tapered portion  174  is the narrowest adjacent the choke portion  178 . The second portion  182  is dimensioned so that a cross-sectional area of the second tapered portion  182  is narrowest adjacent the choke portion  178  and the cross-sectional area of the second tapered portion  182  is widest proximate the venturi tube outlet  162 . The choke portion  178  is substantially cylindrical and has a cross-sectional area that is substantially the same as the narrowest cross-sectional area of the first tapered portion  174  and the narrowest cross-sectional area of the second tapered portion  182 . In the illustrated construction, the cartridge engagement portion  170  is adapted to engage the inner protrusion  146  formed in the bottom of the cartridge  62 . In the illustrated construction, the cartridge engagement portion  170  is compression fitting against the inner protrusion  146 . In other constructions, the cartridge engagement portion  170  may be secured to the inner protrusion  146  by other methods, such as a threaded connection, an adhesive, or sealing members such as o-rings. 
     In the construction of  FIGS. 5-7 , a venturi tube extension  186  ( FIGS. 6 and 7 ) may engaged with the venturi tube  110 . In some constructions, a length of the venturi tube  110  can be effectively increased and decreased by adding and removing venturi tube extensions  186 . The venturi tube extensions  186  may be used, for example, when the media bed is particularly deep so that the venturi tube  110  extends higher than the media bed. Stated more broadly, the media bed is at a first end of the contact chamber  74  and the venturi tube extension  186  extends through the media bed and is operable to move media from the media bed to a second end of the contact chamber  74  opposite the first end. The venturi tube extension  186  may be length-adjustable (telescoping or comprised of stackable extension segments, for example) or replaceable with a venturi tube extension  186  of different length for a given contact chamber  74  and media bed depth. 
     In operation, the nozzle  106  causes the velocity of fluid entering the contact chamber  74  to increase as it enters the venturi tube  110 . At the same time, the nozzle  106  causes the pressure to drop in the suction zone  142  (i.e., a vacuum at the suction openings  114 ). The vacuum draws a fluid and media mixture through the suction opening(s)  114  into the suction zone  142  where it is entrained in the flow from the nozzle  106  to the venturi tube  110 . The pressure of the fluid increases as the fluid approaches the top of the venturi tube  110 . 
     The fluidizer  82  therefore entrains media into the fluid flow and boosts the pressure of the fluid so that the fluid flows higher in the contact chamber  74  than it would under the conventional contact chamber configuration  10 ,  10 ′. A shown in  FIG. 6 , the fluidized media is discharged out of the venturi tube  110 . A volume of the treated fluid (arrows  184 ) flows around the deflector cap  94  and through the treated fluid outlet  70 . A volume of fluid and media (arrows  188 ) equal to the volume of fluid and media drawn in through the suction opening(s)  114  is recirculated back to the bottom of the contact chamber and into the suction opening(s)  114  again. Thus, the eductor increases the volumetric flow of fluid and media in the contact chamber  74  compared to a conventional single-pass contact chamber  10 ,  10 ′. 
     The fluidizer  82  is sized to create a fully-fluidized media bed in both the low flow condition and the high flow condition to avoid dead zones  38 ,  38 ′ in the contact chamber  74 . The eductor creates a fully-fluidized media bed in the low flow condition because the venturi effect increases the fluid velocity within the contact chamber  74  to as much as (more or less) four times the velocity of fluid entering the contact chamber  74  through the feed fluid inlet  66 . This higher velocity flow prevents media from settling at the bottom of the contact chamber  74  in the low flow condition. 
     The fluidizer  82  creates a fully-fluidized media bed in the high flow condition by deflecting much of the fluid and media off of the deflector cap  94 . The deflected fluid and media (arrows  188 ) create downward recirculation that flows down along the outside of the venturi tube extension  186  and the venturi tube  110  and is drawn into the suction openings  114  again. The fluid and media mixture recirculate within the contact chamber  74  at a rate of (more or less) three times the inlet/outlet fluid velocity. The downward velocity of recirculating fluid and media (arrows  188 ) prevents a packed bed from forming at the top of the contact chamber  74 . Fluid flows out of the openings  90  in the cap  94  to the treated fluid outlet while keeping the media in the contact chamber  74 . If an upper mesh layer is used instead of the openings  90 , the mesh layer may be positioned around the deflector cap  94  to prevent media from circumventing the deflector cap  94 . The flow rate out of the contact chamber  74  through the treated fluid outlet  70  equals the flow rate into the contact chamber  74  via the feed fluid inlet  66 . The deflector cap  94  bears most of the impact of the media. 
     The fluidizer  82  illustrated in  FIGS. 6-7  is merely one example of a fluidizer according to the present disclosure. Other examples of fluidizers are included in the following figures and description. 
       FIGS. 8-10  illustrate a cartridge  190  according to another construction, in which the cartridge  190  includes a feed fluid inlet  194 , a treated fluid outlet  198 , and defines a contact chamber  202  ( FIG. 9 ). The feed fluid inlet  194  may be adapted to engage a fluid inlet conduit (not shown) for receiving inlet fluid from a source. The fluid outlet  198  may be adapted to engage a fluid outlet conduit (not shown) for transferring treated fluid to a downstream application. The contact chamber  202  includes a fluidizer  206 , a lower mesh layer  210 , an upper mesh layer  214 , a deflector cap  218 , and media. The lower mesh layer  210  is positioned near the feed fluid inlet  194  to prevent media from entering the feed fluid inlet  194 . The upper mesh layer  214  is positioned near the treated fluid outlet  198  to prevent media from entering the treated fluid outlet  198 . The deflector cap  218  may be positioned on the mesh at the top of the contact chamber  202  to deflect fluid downwardly to promote recirculation. 
     As shown in  FIG. 10 , the fluidizer  206  is an integrated eductor formed in a monolithic block having a first portion  242  defining a nozzle  230 , a second portion  246  defining a venturi tube  234 , and a suction zone  262  defined between the first and second portions  242 ,  246 . The suction zone  262  includes a plurality of suction openings  238  through a circumferential wall  278  of the fluidizer  206 . 
     In the illustrated construction, a diameter of the first portion  242  is smaller than a diameter of the second portion  246 . The nozzle  106  includes a nozzle inlet  250 , a nozzle outlet  254 , and a nozzle cavity  258  formed between the nozzle inlet  250  and the nozzle outlet  254 . The nozzle inlet  250  is engagable with the feed fluid inlet  194  of the cartridge  190  and positioned adjacent a bottom of the cartridge  190  ( FIG. 9 ). The nozzle outlet  254  communicates with the suction zone  262  through a wall  266  of the first portion  242 . In the illustrated construction, the nozzle cavity  258  includes a cylindrical portion  270  proximate the nozzle inlet  250  and a tapered portion  274  proximate the nozzle outlet  254 . The tapered portion  274  is shaped so that a cross-sectional area of the tapered portion  274  decreases towards the nozzle outlet  254 . Accordingly, a cross-sectional area of the nozzle inlet  250  is larger than a cross-sectional area of the nozzle outlet  254 . 
     Referring again to  FIG. 10 , the venturi tube  234  includes a venturi tube inlet  282 , a venturi tube outlet  286 , and a cavity  290 . The venturi tube inlet  282  is adjacent and in fluid communication with the suction zone  262 . The cavity  290  includes a first tapered portion  294 , a choke portion  298 , and a second tapered portion  302 . In the illustrated construction, the first tapered portion  294  extends between the venturi tube inlet  282  and the choke portion  298 . The first tapered portion  294  is dimensioned so that a cross-sectional area of the first tapered portion  294  is the widest proximate the venturi tube inlet  282  and the cross-sectional area of the first tapered portion  294  is the narrowest adjacent the choke portion  298 . The second tapered portion  302  is dimensioned so that a cross-sectional area of the second tapered portion  302  is narrowest adjacent the choke portion  298  and the cross-sectional area of the second tapered portion  302  is widest proximate the venturi tube outlet  286 . The choke portion  298  is substantially cylindrical and has a cross-sectional area that is substantially the same as the narrowest cross-sectional area of the first tapered portion  294  and the narrowest cross-sectional area of the second tapered portion  302 . 
     In the construction of  FIGS. 8-10 , a venturi tube extension  306  ( FIG. 9 ) is engaged with the venturi tube  234 . The venturi tube extension  306  is substantially similar to the venturi tube extension  186  and will not be described in detail for the sake of brevity. 
     The fluidizer  206  therefore entrains media into the fluid flow and boosts the pressure of the fluid so that the fluid flows higher in the contact chamber  202  than it would under the conventional contact chamber configuration  10 ,  10 ′. A shown in  FIG. 9 , the fluidized media is discharged out of the venturi tube  110 . A volume of the treated fluid (arrows  304 ) flows around the deflector cap  218  and through the treated fluid outlet  198 . A volume of fluid and media (arrows  308 ) equal to the volume of fluid and media drawn in through the suction opening(s)  238  is recirculated back to the bottom of the contact chamber and into the suction opening(s)  238  again. Thus, the fluidizer  206  increases the volumetric flow of fluid and media in the contact chamber  202  compared to a conventional single-pass contact chamber  10 ,  10 ′. 
       FIGS. 11-13  illustrate a cartridge  310  according to another construction. The cartridge  310  includes a feed fluid inlet  314 , a treated fluid outlet  318 , and defines a contact chamber  322  ( FIG. 12 ). The feed fluid inlet  314  may adapted to engage a fluid inlet conduit (not shown) for receiving inlet fluid from a source. The treated fluid outlet  318  may be adapted to engage a fluid outlet conduit (not shown) for transferring treated fluid to a downstream application. The contact chamber  322  includes a fluidizer  326 , a lower mesh layer  330 , an upper mesh layer  334 , a deflector cap  338 , and media. The lower mesh layer  330  is positioned near the feed fluid inlet  314  to prevent media from entering the feed fluid inlet  314 . The upper mesh layer  334  is positioned near the treated fluid outlet  318  to prevent media from entering the treated fluid outlet  318 . The deflector cap  338  may be positioned on the mesh at the top of the contact chamber  322  to deflect fluid downwardly to promote recirculation. 
     As shown in  FIGS. 12-13 , the fluidizer  326  is an eductor including a nozzle  350 , a venturi tube  354 , and one or more suction openings  358  positioned between the nozzle  350  and a cavity  360  formed in a bottom of the cartridge  310 . With particular reference to  FIG. 13 , the fluidizer  326  includes a first portion  362  including the nozzle  350  and a second portion  366  defining a cavity  370 . In the illustrated construction, a diameter of the first portion  362  is smaller than a diameter of the second portion  366 . The nozzle  350  includes a nozzle inlet  374 , a nozzle outlet  378 , and a nozzle cavity  382  formed between the nozzle inlet  374  and the nozzle outlet  378 . The nozzle inlet  374  is aligned with the feed fluid inlet  314  of the cartridge  310  and spaced from the cavity  360  formed in the bottom of the cartridge  310  so that the cavity  360  acts as a suction zone. In the illustrated construction, the nozzle cavity  382  includes a cylindrical portion  394  proximate the nozzle inlet  374  and a tapered portion  398  proximate the nozzle outlet  378 . The tapered portion  398  is shaped so that a cross-sectional area of the tapered portion  398  decreases towards the nozzle outlet  378 . Accordingly, a cross-sectional area of the nozzle inlet  374  is larger than a cross-sectional area of the nozzle outlet  378 . 
     The venturi tube  354  is formed by a valve body  406  positioned in the cavity  370  of the second portion  366  of the fluidizer  326 . The venturi tube  354  is seated against a wall  390  formed between the first portion  362  and the second portion  366  of the fluidizer  326 . In the illustrated construction, the valve body  406  is a duckbill valve body. The valve body  406  forms a cavity  410  and includes a valve outlet  414 . The cavity  410  is adjacent and in fluid communication with the nozzle outlet  378 . The cavity  410  includes a first portion  422  having a generally circular cross section and a second portion  426  having a generally trapezoidal cross section. The valve outlet  414  is formed in an upper wall  432  of the second portion  426 . In the illustrated construction, the valve outlet  414  is a rectangular slit. Accordingly, a cross-sectional area of the cavity  410  is wider than a cross-sectional area of the valve outlet. 
     In the construction of  FIGS. 11-13 , a venturi tube extension  434  ( FIG. 12 ) is engaged with the venturi tube  354 . The venturi tube extension  434  is substantially similar to the venturi tube extension  186  and will not be described in detail for the sake of brevity. 
     The fluidizer  326  therefore entrains media into the fluid flow and boosts the pressure of the fluid so that the fluid flows higher in the contact chamber  322  than it would under the conventional contact chamber configuration  10 ,  10 ′. A shown in  FIG. 9 , the fluidized media is discharged out of the venturi tube  354 . A volume of the treated fluid (arrows  432 ) flows around the deflector cap  338  and through the treated fluid outlet  318 . A volume of fluid and media (arrows  436 ) equal to the volume of fluid and media is drawn in through the suction opening(s)  358  is recirculated back to the bottom of the contact chamber and into the suction opening(s)  358  again. Thus, the fluidizer  326  increases the volumetric flow of fluid and media in the contact chamber  322  compared to a conventional single-pass contact chamber  10 ,  10 ′. 
       FIGS. 14-16  illustrate a cartridge  438  according to another construction. The cartridge  438  includes an inlet cap  442  and an outlet cap  446 . The inlet cap  442  is engaged with a mounting wall  448  formed in an inlet end  450  of the cartridge  438  and includes a feed fluid inlet  454 . The feed fluid inlet  454  may be adapted to engage a fluid inlet conduit (not shown) for receiving feed fluid from a source. The outlet cap  446  is engaged with an outlet end  458  of the cartridge  438  and includes a treated fluid outlet  462 . The treated fluid outlet  462  may be adapted to engage a fluid outlet conduit (not shown) for transferring treated fluid to a downstream application. The cartridge  438  and the inlet cap  442  cooperatively form a fluidizer  466  ( FIGS. 15-16 ). The cartridge and the outlet cap  446  cooperatively form a contact chamber  470 . The contact chamber  470  may include a lower mesh layer, an upper mesh layer, a deflector cap, and media similar to what is described above with respect to  FIGS. 5-7 . 
     As shown in  FIG. 16 , the fluidizer  466  is formed in the inlet end  450  of the cartridge  438 . The fluidizer  466  includes a fluidizer inlet  474 , a plurality of radial flow paths  478 , and a plurality of circumferential slits  482 . The fluidizer inlet  474  and the plurality of radial flow paths  478  are formed in a wall  486  of the cartridge  438 . The circumferential slits  482  are formed about a circumference of the wall  486 . The wall  486  includes securing portions  490  engaged with the inlet cap  442  in a fluid-tight connection. Accordingly, all of the fluid entering the contact chamber  470  must pass along a flow path defined by the feed fluid inlet  454 , the fluidizer inlet  474 , the radial flow paths  478 , and the circumferential slits  482  to enter the contact chamber  470 . As shown by the arrows  484 , the fluid travels along the radial flow paths  478 , the fluid flows in a direction generally perpendicular to the flow path of fluid entering the fluidizer  466  at the fluidizer inlet  474 . As shown by the arrows  488 , when the fluid enters the circumferential slits  482  from the radial flow paths  478 , the fluid flows in a direction generally perpendicular to the flow path of the fluid in the radial flow paths  478 . The flow pattern produced by the radial flow paths  478  and the circumferential slits  482  causes the fluid to flow in a manner that fluidizes the media bed. 
       FIG. 17  illustrates a cartridge  492  including contact chamber  494  fitted with a fluidizer  498  that is an external eductor. The fluidizer  498  is positioned beneath the contact chamber  494 . A suction conduit  502  is positioned between a bottom of the contact chamber  494  and the external fluidizer  498 . An inlet  506  of the suction conduit  502  is positioned within an area of the contact chamber  494  that is occupied by the media bed in an at-rest condition. An outlet  510  of the suction conduit  502  is connected with the fluidizer  498 . The external fluidizer  498  includes an eductor nozzle  514 , a suction zone  518 , and a venturi tube  522 . The eductor nozzle  514  includes an inlet  526  engaged with a feed fluid conduit  530  and an outlet  534  positioned in the suction zone  518 . The suction zone  518  is generated or established between the eductor nozzle  514  and the venturi tube  522 . The venturi tube  522  is spaced from the eductor nozzle  514  within the suction zone  518 . 
     With continued reference to  FIG. 17 , the fluid enters the fluidizer  498  (arrow  528 ) through the feed fluid conduit  530  and the nozzle  514 , resulting in a high velocity of fluid through the suction zone  518  and into the venturi tube  522 . This creates a vacuum in the suction zone  518  which draws a fluid and media mixture through inlet  506  into the suction zone  518 . The media  538  is entrained into the fluid feed flow to form a mixture. The mixture travels through an external conduit  542  that extends along an exterior of the contact chamber  494  (arrows  532 ), and enters the contact chamber  494  proximate a deflector cap  546 . A portion the fluid flows around the deflector cap  546  (arrows  536 ) and exits the contact chamber  494  through a treated fluid outlet  540 . The deflector cap  546  deflects much of the portion of fluid and media downwardly along the sides of the contact chamber  494  (arrows  544 ), recirculating the mixture of media and fluid. The media  538  is fully fluidized within the contact chamber as a result of the mixing in the suction zone  518  and external conduit  542 , and introducing the media and fluid at the top of the contact chamber  494  against the deflector cap  546 . A mesh layer  547  is positioned between the deflector cap  546  and the treated fluid outlet  540  to prevent media from entering the treated fluid outlet  540 . 
       FIGS. 18 and 19  illustrate alternative constructions of a cartridge having a contact chamber having a fluidizer in which strategically-positioned and angled nozzles form the fluidizer. The strategic positioning and angling of the nozzles causes the media to become fully fluidized in the contact chamber. In these constructions, fluidization is achieved without an eductor. The nozzles are positioned and angled to promote recirculation in the contact chamber. Although single nozzles ( FIG. 18 ) and pairs of nozzles ( FIG. 19 ) are illustrated, it will be understood that nozzles can be provided in singles, pairs, or sets of more than two in alternative constructions to promote fluidization and recirculation. Also, although the angles of the nozzles are illustrated as vertical and horizontal, these nozzle angles can be adjusted to achieve the desired results, as noted below. 
       FIG. 18  illustrates a cartridge  548  having contact chamber  550  including a fluidizer  554  comprising a plurality of external mixing nozzles  558 ,  560 ,  562 . A first mixing nozzle  558  is positioned at a bottom of the contact chamber  550  within an area occupied by the media bed in an at-rest condition. A second mixing nozzle  560  is positioned along a side of the contact chamber  550  and within the area occupied by the media bed in the at-rest condition. A third mixing nozzle  562  is positioned along a side of the contact chamber and above the second mixing nozzle  560 . The third mixing nozzle  562  is disposed above the area occupied by the media bed in an at-rest condition. Feed fluid flowing into the contact chamber  550  through the first mixing nozzle  558  and the second mixing nozzle  560  lifts the media  566  and causes the media  566  to become at least partially fluidized. Feed fluid flowing into the contact chamber  550  through the second mixing nozzle  560  and the third mixing nozzle  562  urges fluid in a horizontal direction. The combination of vertical flow from the first mixing nozzle  558  and the horizontal flow of the second mixing nozzle  560  and the third mixing nozzle  562  cause mixing of the media  566  and the fluid. The result is a fully fluidized contact chamber  550  of media and fluid with vertical and horizontal components of flow. This promotes thorough mixing and recirculation of the media  566 . Treated fluid flows out of the contact chamber  550  through a treated fluid outlet  563 . A mesh layer  564  is positioned near the treated fluid outlet  563  to prevent the media  566  from entering the treated fluid outlet  563 . 
       FIG. 19  illustrates a cartridge  568  having a contact chamber  570  including a fluidizer  572  comprising a plurality of internal mixing nozzles. A distribution tube  574  extends from a feed fluid inlet  578  at the bottom of the contact chamber  570  up through the at-rest media bed and to the top portion of the contact chamber  570 . The distribution tube  574  includes a first pair of mixing nozzles  582 , a second pair of mixing nozzles  586 , and a third pair of mixing nozzles  590 . The first pair of mixing nozzles  582  is illustrated as horizontal, but may be angled down toward the bottom of the contact chamber  570  within an area occupied by the media bed in an at-rest condition. The downward flow of feed fluid from the first pair of mixing nozzles  582  reaches the bottom of the contact chamber  570  and deflects upwardly, causing an upward flow of media  594  that has settled along the bottom of the contact chamber  570 . The second pair of mixing nozzles  586  is positioned above the first pair of mixing nozzles  582 . In the illustrated construction, the second pair of mixing nozzles  586  is above the at-rest height of the media bed. The second pair of mixing nozzles  586  directs feed fluid horizontally or radially toward the walls of the contact chamber  570 . The feed fluid flowing radially from the second pair of mixing nozzles  586  deflects up and down off the side walls of the contact chamber  570 , mixing the media and the fluid. The third pair of mixing nozzles  590  is directed upward to send feed fluid upwardly. A portion of the upward flow of feed fluid from the third pair of mixing nozzles  590  deflects off a top of the contact chamber  570  or off a screen  598  or deflector (not shown) near the top of the contact chamber  570 . Another portion of the fluid flows out of the contact chamber  570  through the treated water outlet  599 . The net result of the three pairs of nozzles  582 ,  586 ,  590  is to cause full fluidization and recirculation of the media  594  in the contact chamber  570 . Although the nozzles  582 ,  586 ,  590  are illustrated in pairs in the two-dimensional drawing of  FIG. 19 , there may be more than two nozzles in each set. For example, there may be three or four nozzles, with some being directed into or out of the page to a selected degree. 
       FIG. 20  illustrates a cartridge  600  having a contact chamber  602  including a fluidizer  606  that does not use an eductor or nozzles to promote fluidization and recirculation. Instead, an internal shaft  610  is provided in the contact chamber  602 . The internal shaft  610  includes one or more mixer blades. A first mixing blade  614  is positioned proximate a bottom of the contact chamber  602  within an area occupied by the media bed in an at-rest condition. A second mixing blade  618  may be disposed above the first mixing blade  614 . A third mixing blade  622  may be disposed above the second mixing blade  618 . The internal shaft  610  is rotated by a motor  626  to cause mechanical mixing and recirculation of the mixture of fluid and media in the contact chamber  602 . The motor  626  may be powered by electricity, water, air, or any other suitable motive force. Feed fluid enters through a feed fluid inlet  630  in a bottom of the contact chamber  602 . A lower mesh layer  632  is positioned adjacent the feed fluid inlet  630  to prevent media from entering the feed fluid inlet  630 . Treated fluid exits the contact chamber  602  through a treated fluid outlet  634  positioned at a top of the contact chamber  602 . An upper mesh layer  635  is positioned adjacent the treated fluid outlet  634  to prevent the media from entering the treated fluid outlet  634 . 
       FIG. 21  illustrates a cartridge  636  having a contact chamber  638  including a fluidizer  642  that does not use an eductor or nozzles or mixer blades to promote fluidization and recirculation. Instead, a submersible pump  646  is positioned in the contact chamber  638 . The submersible pump  646  has an inlet  650  within an area of the contact chamber  638  that is occupied by the media bed in an at-rest condition. A tube  654  is engaged with an outlet  658  of the submersible pump  646  and extends towards a top of the contact chamber  638 . The submersible pump  646  includes a motor  662  that creates a vacuum at the inlet  650  of the submersible pump  646 , which entrains a mixture of feed fluid and media from a bottom of the contact chamber  638  and releases the combined flow of fluid and media proximate a deflector cap  666  positioned near the top of the contact chamber  638 . A portion of the treated fluid flows around the deflector cap  666  and exits the contact chamber  638  through a treated fluid outlet  664  (arrows  667 ). Much of the combined flow of fluid and media is deflected by the deflector cap  666  (arrows  668 ) to promote full fluidization and recirculation. A mesh layer  669  is positioned between the deflector cap  666  and the treated fluid outlet  664  to prevent media from entering the treated fluid outlet  664 . A feed fluid inlet  670  may be positioned at the bottom of the contact chamber  638  or at a side of the contact chamber  638  and proximate to the bottom of the contact chamber  638 . The motor  662  of the submersible pump  646  may be driven electrically, hydraulically, pneumatically, or by any other suitable motive force. 
       FIG. 22  illustrates a cartridge  672  including a contact chamber  674  that includes a fluidizer  642  comprising an external pump  682 . In the illustrated construction, the external pump  682  is positioned along an external conduit  686  having a feed fluid inlet  690  at a bottom of the contact chamber  674  and an outlet proximate  694  a top of the contact chamber  674 . As shown in  FIG. 22 , in some constructions the feed fluid inlet  690 ′ may be at a side of the contact chamber  674  proximate the bottom of the contact chamber  674 . In an alternate construction, the feed fluid inlet  690 ″ may be positioned along the external conduit  686  and downstream of the external pump  682 . In the alternate construction, the feed fluid inlet  690  may be positioned along the external conduit  686  and upstream of the external pump  682 . 
     A suction force downstream of the external pump  682  pulls a mixture of feed fluid and a mixture of media and fluid from the bottom of the contact chamber  674  into the external conduit  686  (arrows  696 ). The external conduit  686  releases the mixture of media and feed fluid proximate a deflector cap  698  (arrows  700 ). A portion of the treated fluid flows around the deflector cap  698  (arrows  702 ) and flows through the treated fluid outlet  694 . The deflector cap  698  deflects a portion (which may be a majority in some constructions) of the fluid and media mixture downward (arrows  704 ), creating recirculation of the media and fluid mixture as discussed above. A mesh layer  699  is positioned between the deflector cap  698  and the treated fluid outlet  694  to prevent the media from entering the treated fluid outlet  694 . A motor  706  of the external pump  682  may be driven electrically, hydraulically, pneumatically, or by any other suitable motive force. 
       FIG. 23  illustrates a cartridge  708  having a contact chamber  710  that includes a fluidizer  714  comprising internal baffles  718  or mixing blades. The internal baffles  718  extend along a majority of an internal area of the contact chamber  710  and cause mixing of the fluid and media  722  by forcing the fluid and media  722  to follow a tortuous flow path between a feed fluid inlet  726  at a bottom of the contact chamber and a treated fluid outlet  730  at a top of the contact chamber  710 . A lower mesh layer  728  is positioned adjacent the feed fluid inlet  726  to prevent media from entering the feed fluid inlet  726 . An upper mesh layer  734  is positioned adjacent the treated fluid outlet  730  to prevent media from entering the treated fluid outlet  730 . 
       FIG. 24  illustrates a cartridge  736  including a contact chamber  740  having an irregular shape that acts as a fluidizer. As shown in  FIG. 24 , adjacent portions of the contact chamber  740  have different cross-sectional shapes. For example, a first portion  744  may have a cross section substantially larger than a second  748 , adjacent, portion. The alternating first and second cross sections cause the flow velocity to change as the fluid travels between adjacent portions  744 ,  748 . As shown by the arrows  760 , when the flow encounters a portion having an increased cross-sectional area, a portion of the fluid will circulate within the wider first portions  744 , mixing the media and the fluid. Although the contact chamber  740  of  FIG. 24  is symmetrical about a central axis, the contact chamber  740  may be asymmetrical in other constructions. A lower mesh layer  754  is positioned adjacent a feed fluid inlet  752  to prevent media from entering the feed fluid inlet  752 . An upper mesh layer  756  is positioned adjacent a treated fluid outlet  758  to prevent media from entering the treated fluid outlet  758 . 
     Each of the various constructions described above includes a fluidizer to promote full fluidization and recirculation of the media in the contact chamber. The fluidizer can take any form that achieves these purposes. Examples given above for fluidizers include: eductors, nozzles, mixer blades, pumps, baffles, and irregular wall shapes, but these examples are not limiting of the disclosure. It is within the scope of the present disclosure to use combinations of these exemplary fluidizers and other forms of fluidizers to fully fluidize and recirculate the media in the contact chamber. 
     Example Fluidization Study 
     A study was conducted of the range of flow velocities over which full fluidization can occur in a given contact chamber. The study first found the range of flow velocities for a conventional contact chamber, and then studied the range of flow velocities for a contact chamber according to the present disclosure. 
     The contact chambers in the study used an up-flow configuration (because the scale control media has a specific gravity greater than 1.0) so that feed water enters the contact chamber from a bottom of the contact chamber and exits at a top of the contact chamber. The test conditions for the fluidization study were:
         Scale control media had a diameter of 0.2-1.2 mm, a density of 750 g/liter, and a void area of ˜40%, resulting in a specific gravity of ˜1.25.   The fluid was water at a temperature of 16° C.   The height of the test contact chamber was 30 cm and its inner diameter was 5 cm.   Three different media depths were tested (5 cm, 10 cm, and 15 cm).       

     Scale control media was added in the test contact chamber to yield 5, 10, and 15 cm media depth. Water was introduced into the test contact chamber at seven different flow rates and the resulting media height was measured at each flow rate. 
     The flow rate and fluidized media height for the conventional chamber (30 cm tall) are summarized in Table 1A (media height in cm) and Table 1B (percent media height expansion) below: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1A 
               
               
                   
                   
               
               
                   
                 Flow Velocity 
                   
               
               
                   
                 (cm/min) 
                 Results (media height, cm) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 0 
                 5 
                 10 
                 15 
               
               
                   
                 7 
                 5 
                 13 
                 20 
               
               
                   
                 10 
                 10 
                 20 
                 25 
               
               
                   
                 53 
                 15 
                 25 
                 Overflow 
               
               
                   
                 80 
                 20 
                 30 
                 Overflow 
               
               
                   
                 106 
                 25 
                 Overflow 
                 Overflow 
               
               
                   
                 133 
                 30 
                 Overflow 
                 Overflow 
               
               
                   
                 160 
                 Overflow 
                 Overflow 
                 Overflow 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1B 
               
               
                   
                   
               
               
                   
                 Flow Velocity 
                   
               
               
                   
                 (cm/min) 
                 % of media expansion 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 0 
                  0% 
                  0% 
                  0% 
               
               
                   
                 7 
                  0% 
                  30% 
                 33% 
               
               
                   
                 10 
                 100% 
                 100% 
                 67% 
               
               
                   
                 53 
                 200% 
                 150% 
                 Overflow 
               
               
                   
                 80 
                 300% 
                 200% 
                 Overflow 
               
               
                   
                 106 
                 400% 
                 Overflow 
                 Overflow 
               
               
                   
                 133 
                 500% 
                 Overflow 
                 Overflow 
               
               
                   
                 160 
                 Overflow 
                 Overflow 
                 Overflow 
               
               
                   
                   
               
            
           
         
       
     
     In the Table 1A, full fluidization (30 cm) was witnessed only at 133 cm/min (i.e., at some flow range between 106 and 160 cm/min) for a 5 cm bed and only at 80 cm/min (i.e., at some flow range between 53 and 106 cm/min) for a 10 cm bed. The 15 cm bed did not become fully fluidized at any flow rate monitored and reached the overflow condition at a relatively low flow rate (53 cm/min) and above. 
     The test results show that in a conventional contact chamber the percent of bed expansion depends on the fluid velocity and characteristics of the media and fluid (for example specific gravity, viscosity, surface finish, etc.). The height of fluidization changes depending on the percent bed expansion and the depth of media. If the fluid velocity is too high, the frictional forces of the fluid acting on the media lift the media and cause some media to be trapped at the top of the contact chamber (overflow condition). In overflow conditions, most of the media may collect in the top of contact chamber generating a dead zone in the lower part of the contact chamber. 
     Even with the fluidized conditions, there are still inactive or dead zones in a conventional contact chamber. For 100% of the contact chamber to be active, the fluid velocity must be optimized. In a conventional contact chamber, this only occurs over a narrow flow range+/−less than about 27 cm/min. For example, referring to Table 1, full fluidization was only achieved in a 30 cm tall contact chamber for a 5 mm media bed between the flow rates of 106 and 160 cm/min (i.e., 133+/−27 cm/min) and for a 10 mm media bed between the flow rates of 53-106 (i.e., 80+/−˜27 cm/min). Full fluidization was not achievable in the test setup for a media bed of 15 cm in a conventional contact chamber. This also shows that the optimum velocity changes based on initial media depth. Fluid temperature is another factor that can change the optimum velocity for full fluidization. 
     The flow rate and fluidized media height for a contact chamber including a fluidizer according to the present disclosure are summarized in Table 2 below: 
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Flow Velocity 
                 Results 
                   
               
               
                 (cm/min) 
                 (media height, cm) 
                 % Bed Expansion 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 0 
                 10 
                 0 
               
               
                 7 
                 25 
                 150% 
               
               
                 10 
                 30 
                 200% 
               
               
                 53 
                 30 
                 200% 
               
               
                 80 
                 30 
                 200% 
               
               
                 106 
                 30 
                 200% 
               
               
                 133 
                 30 
                 200% 
               
               
                 160 
                 30 
                 200% 
               
               
                   
               
            
           
         
       
     
     Based on Table 2, it is clear that full fluidization in the 30 cm contact chamber (i.e., where “Results” equals “30”) was achieved over a wide range of flow rates for an initial media bed height of 10 cm. The range of fluid velocity over which full fluidization was achieved was at least 150 cm/min. The upper limit of flow velocity at which full fluidization can occur was not reached in the study. 
     Example Efficacy Study 
     Another study was conducted to compare the performance of a reverse osmosis (RO) membrane receiving water from a conventional contact chamber and from a contact chamber according to the present disclosure. The performance of the RO membranes was measured based on two factors: RO membrane permeate flow (Flux Rate) and RO membrane salt rejection. 
     Both contact chambers were 5 cm in diameter and 30 cm in height. The enhanced contact chamber was equipped with an eductor and diffuser tube extension as described above with respect to  FIG. 5 . Both contact chambers had 300 ml (225 g) of media or a (no flow) media depth of 15 cm. The water velocity was 100 cm/min. The conventional contact chamber was observed to have nearly 100% fluidized condition. 
       FIGS. 25 and 26  illustrate the results of the efficacy test for an RO system with a conventional contact chamber versus an RO system with a recirculating enhancing contact chamber (RECC). As can be seen in  FIG. 25 , the RO system that received water from a conventional contact chamber failed after producing ˜15 tons of purified water. The flux dropped by 50% with the dropping from ˜1200 to ˜500 ml/min. With reference to  FIG. 26 , the conventional RO system salt rejection dropped from ˜90% to ˜65% after producing 15 tons of purified water, and kept declining until the test was terminated at ˜20 tons. 
     The RO system receiving water from the RECC fared much better than the conventional setup. As illustrated in  FIGS. 25 and 26 , the RO system with RECC performed well through &gt;28 tons of purified water (minimum life=22 tons). The test results show that the flux ( FIG. 25 ) remained above 1000 ml/min and the salt rejection ( FIG. 26 ) remained relatively constant at ˜90%. 
       FIG. 27  is a graph showing the performance of the scale prevention system of the present disclosure when used before a tankless water heater. In this graph, the baseline condition is with no treatment, the “conventional reactor” is the same as a conventional reactor described above, and the “new reactor” is the improved RECC device of the present disclosure. The graph plots flue gas outlet temperature of the water heater as a function of the total gallons of water through the system. As scale builds up and insulates the heat exchange surfaces, less heat is transferred from the gas to the water, and the flue gas temperature increases. A level flue gas temperature is an indicator of a lack of scale formation. The flue temperatures for the new reactor are more consistent than those of the baseline or the conventional reactor, staying in the rage of 95-100 F for the tested water heater. By contrast, the baseline and conventional reactor plots show significant increases in flue gas temperature after a relatively low volume of water had flown through the heater. 
     Thus, the disclosure provides, among other things, a contact chamber in which the bed of fluid treatment media is fully fluidized by using a fluidizer. The fluidizer may be, for example, an internal or external eductor that acts as a pump for a media and fluid mixture to boost fluid flow and generate recirculation that keeps the media suspended in the fluid or an arrangement of nozzles, mixing blades, pumps, baffles, or irregular cross-sectional shapes (or combinations of any of these) to promote fully fluidizing the media in the chamber and causing the media to recirculate within the chamber. Various features and advantages of the disclosure are set forth in the following claims.