Abstract:
A fluid treatment system for treating feed water includes a first tubular member having first and second ends, at least one second tubular member having first and second ends, a pump positioned within the first tubular member, a filtering membrane positioned within the second tubular member, a first end cap for receiving the first ends of the first and second tubular members, and a second end cap for receiving the second ends of the first and second tubular members.

Description:
PRIORITY 
       [0001]    The present invention claims priority to U.S. Provisional Application Ser. Nos. 61/173,255, filed Apr. 28, 2009 and 61/323,965, filed Apr. 14, 2010, the entirety of which are incorporated herein by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to fluid treatment systems and, in particular, relates to a compact reverse osmosis based treatment system that occupies a small footprint and that is easily expandable. 
       BACKGROUND OF THE INVENTION 
       [0003]    Various methods and apparatus are known for purifying solvents, particularly water. One such method utilizes the principle of reverse osmosis to reduce or eliminate the quantity of dissolved solids in a liquid. According to the reverse osmosis principle, a semi-permeable membrane is used to separate the solvent from the dissolved solids. For example, in purifying water, a membrane is selected that exhibits greater permeability to water than the dissolved solids carried by the water. Raw feed water is applied to the membrane at a pressure generally greater than the osmostic pressure of the water. Under pressure, water passes through the membrane leaving behind the dissolved solids. The liquid passing through the membrane is generally termed “permeate” whereas the liquid remaining on the input side of the membrane is generally termed “concentrate” and is usually discarded to a drain. 
         [0004]    Since the concentration of the solutes increases on the concentrate side of the membrane during the reverse osmosis process precipitation of one or more of the dissolved solids can occur. This precipitation can cause plugging of the membrane, thereby lowering the efficiency of the process. To remedy this, some systems recycle a portion of the permeate back through the membrane to flush the membrane of these precipitates. One such example of a conventional fluid treatment system using a permeate flush is illustrated in U.S. Pat. No. 4,629,568 entitled “Fluid Treatment System” to Ellis III, which is herein incorporated by reference and attached hereto as an appendix. 
         [0005]    Due to the number of products and byproducts generated by the reverse osmosis process, as well as the need to periodically flush the membrane, conventional fluid treatment systems require a multitude of plumbing connections and space to accommodate all the necessary processing and storage components. Such systems are therefore susceptible to leaks and require a large amount of space. There is therefore a need to provide a fluid treatment system that is capable of performing all the aforementioned tasks while minimizing the probability of leakage and requiring a minimal amount of space. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with an embodiment of the present invention a fluid treatment system for treating feed water includes a first tubular member having first and second ends, at least one second tubular member having first and second ends, a pump positioned within the first tubular member, a filtering membrane positioned within the second tubular member, a first end cap for receiving the first ends of the first and second tubular members, and a second end cap for receiving the second ends of the first and second tubular members. 
         [0007]    In accordance with another aspect of the present invention a fluid treatment system includes at least one first tubular member containing a membrane filter. The first tubular member has first and second ends. A first end cap structure sealingly receives a first end of the tubular member and a second end cap structure sealingly receives a second end of the tubular member. A pump delivers water to be treated to one of the end cap structures. At least one of the end cap structures serves as a mounting for temperature and pressure sensors for monitoring the temperature and pressure of the water communicated by the pump to the one end cap structure. 
         [0008]    In accordance with another aspect of the present invention a fluid treatment system includes a filtering membrane located within a first tubular member. The filtering membrane has an input for receiving water to be treated. A pump delivers water to be treated to the filtering membrane. The pump is located within a second tubular member. Each of the tubular members has first and second ends. The first and second ends of at least one of the tubular members are received by respective first and second end cap. At least of the end caps serves as a mounting for temperature and pressure sensors that monitor the temperature and pressure of water to be treated. The sensors communicate with associated fluid passages defined within the one end cap. 
         [0009]    In accordance with another aspect of the present invention a fluid treatment system for treating feed water includes a first tubular member having first and second ends and a second tubular member having first and second ends. A pump is positioned within the first tubular member and a filtering membrane is positioned within the second tubular member. A first end cap receives the first end of the first tubular member and a second end cap receives the second end of the first tubular member. An adapter secures the pump to the first end cap and prevents relative rotation between the pump and the first end cap. The adapter includes a plurality of shoulders that mate with recessed portions of the first end cap. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The foregoing and other features and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which; 
           [0011]      FIG. 1  is a schematic illustration of a fluid treatment system in accordance with the present invention; 
           [0012]      FIG. 2  is a schematic illustration of a reverse osmosis unit of the fluid treatment system of  FIG. 1 ; 
           [0013]      FIG. 3  is an exploded assembly view of the reverse osmosis unit of  FIG. 2 ; 
           [0014]      FIG. 4  is an enlarged vim of a bottom portion of the reverse osmosis unit of  FIG. 3 ; 
           [0015]      FIG. 5  is an enlarged view of a top portion of the reverse osmosis unit of  FIG. 3 ; 
           [0016]      FIG. 6A  is a perspective view of a bottom plate of the reverse osmosis unit of  FIG. 2 ; 
           [0017]      FIG. 6B  is a top view of the bottom plate of  FIG. 6A ; 
           [0018]      FIG. 6C  is a section view of the bottom plate of  FIG. 6A ; 
           [0019]      FIG. 6D  is a section view of the bottom plate of the reverse osmosis unit of  FIG. 6A  taken along line D-D; 
           [0020]      FIG. 7A  is a perspective view of a top plate of the reverse osmosis unit of  FIG. 3 ; 
           [0021]      FIG. 7B  is a top view of the top plate of  FIG. 7A ; 
           [0022]      FIG. 7C  is a section view of the top plate of  FIG. 7A ; 
           [0023]      FIG. 7D  is a section view of the top plate of the reverse osmosis unit of  FIG. 7A  taken along, line D-D; 
           [0024]      FIG. 8  is a front sectional view of  FIG. 2 ; 
           [0025]      FIG. 9A  is a schematic illustration of an alternative embodiment of the fluid treatment system in accordance with the present invention; 
           [0026]      FIG. 9B  is a schematic illustration of another embodiment of the fluid treatment system in accordance with the present invention; 
           [0027]      FIG. 9C  is a schematic illustration of another embodiment of the fluid treatment system in accordance with the present invention; 
           [0028]      FIG. 10  is a perspective view of a reverse osmosis unit of the fluid treatment system of  FIG. 9C ; 
           [0029]      FIG. 11A  is a section view of the reverse osmosis unit of  FIG. 10  taken along line  11 A- 11 A; 
           [0030]      FIG. 11B  is a section view of the reverse osmosis unit of  FIG. 10  taken along line  11 B- 11 B; 
           [0031]      FIG. 12A  is a section view of the reverse osmosis unit of  FIG. 10  taken along line  12 A- 12 A; 
           [0032]      FIG. 12B  is a section view of the reverse osmosis unit of  FIG. 10  taken along line  12 B- 12 B; 
           [0033]      FIG. 13  is a section view of the reverse osmosis unit of  FIG. 10  taken along line  13 - 13 ; 
           [0034]      FIG. 14  is a schematic illustration of a fluid treatment system in accordance with another aspect of the present invention; 
           [0035]      FIG. 15  is schematic illustration of an adjustable flow control element for the fluid treatment system of  FIG. 14 ; 
           [0036]      FIGS. 16A-B  illustrate an outer sleeve of the adjustable flow control element of  FIG. 15 ; 
           [0037]      FIGS. 16C-E  illustrate an inner sleeve of the adjustable flow control element of  FIG. 15 ; 
           [0038]      FIGS. 16F-H  illustrate a flange of the adjustable flow control element of  FIG. 15 ; 
           [0039]      FIG. 17  is a section view of a pressure end cap in accordance with another aspect of the present invention; and 
           [0040]      FIG. 18  is a schematic illustration of an adapter for use in the pressure end cap of  FIG. 17 . 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    The present invention relates to fluid treatment systems and, in particular, relates to a fluid treatment system that has multi-function end caps,  FIG. 1  illustrates a fluid treatment system  20  in accordance with the present invention. The system includes a reverse osmosis (R/O) unit  30  connected to an input conduit or feed conduit  32  through which feed water to be purified is communicated to the R/O unit. The R/O unit  30  also communicates with output conduits  40  and  43  through which “permeate” and “concentrate” are discharged, respectively, from the R/O unit. The R/O unit  30  includes a pump  70  for pumping the feed water through the R/O unit and a semi-permeable membrane  80  for processing the feed water into concentrate and permeate. The membrane  80  may constitute an R/O membrane or a nanofiltration membrane. According to the reverse osmosis principle, feed water supplied through the feed conduit  32  as indicated by arrow A is applied to the membrane  80  at a pressure greater than the osmotic pressure. Water passes through the membrane  80  and becomes permeate that is released into the permeate conduit  40  as indicated by arrow B while dissolved solids in the feed water remain on the application side of the membrane and are eventually discharged from the concentrate conduit  43  and into a drain conduit  60  as indicated by arrow C. 
         [0042]    As shown in  FIG. 1 , raw feed water is fed to the R/O unit  30  through the feed conduit  32 . A valve, such as a solenoid valve  34  controls fluid communication between the feed conduit  32  and the R/O unit  30 . A drain opening  218  in the R/O unit  30  directs the concentrate out of the R/O unit and to the drain conduit  60 , where the concentrate flows, to a drain or waste (not shown). A valve, such as a solenoid valve (not shown), or other flow regulating structure, may control fluid communication between the R/O unit  30  and the drain conduit  60 . Alternatively, the concentrate may be fed to at least one more membrane (not shown) in serial and/or parallel connection with the membrane  80  in order to process the feed water in a cascading fashion. 
         [0043]    A permeate check valve  42  controls fluid communication between the R/O unit  30  and the permeate conduit  40 . The permeate check valve  42  allows fluid to flow from the R/O unit  30  to the permeate conduit  40  but prevents reverse flow. The permeate conduit  40  connects the R/O unit  30  to an atmospheric storage tank  46  or a pressurized storage tank  47 . For purposes of illustration, it is presumed that the permeate conduit  40  connects the R/O unit  30  to the atmospheric storage tank  46 . The permeate check valve  42  between the R/O unit  30  and the permeate conduit  40  therefore controls fluid communication between the R/O unit and the storage tank  46 . The atmospheric storage tank  46  stores permeate exiting the R/O unit  30 . A supply conduit  50  provides fluid communication between the storage tank  46  and a process demanding permeate, such as a faucet  52 . A pump  48  maintains the permeate in the supply conduit  50  under pressure. 
         [0044]    A permeate rinse conduit  54  taps into the supply conduit  50  and fluidly connects the storage tank  46  back to the R/O unit  30 . A permeate rinse valve, such as a solenoid valve  56 , controls fluid communication between the storage tank  46  and the R/O unit  30  through the rinse conduit  54 . A check valve  58  allows fluid to flow from the storage tank  46  to the R/O unit  30  but prevents reverse flow. 
         [0045]    A controller  90  (not shown, see  FIG. 2 ) in the RD wilt  30  controls operation of the inlet valve  34  and the rinse valve  56  as well as operation of the pump  70 . In operation, when it is desirable for fluid treatment to begin, the controller  90  activates the pump  70  and opens the inlet valve  34  to allow feed water to enter the R/O unit  30  through the feed conduit  32  as indicated at A. The feed water may be supplied by an external source (not shown) that supplies the feed water under pressure at about 50-70 psi. The pump  70  forces the feed water through the semi-permeable membrane  80  via reverse osmosis, thereby separating the teed water into concentrate and permeate. Flow regulating discs  406  and  412  in the R/O unit  30  restrict the flow of fluid through the R/O unit, thereby creating the necessary back pressure required to perform reverse osmosis on the feed water. 
         [0046]    A low feed pressure switch  400  monitors the pressure of the feed water entering the R/O unit  30  via the feed conduit  32 . If the feed pressure falls below a predetermined amount, the controller  90  deactivates the pump  70  and turns off the inlet valve  34 , thereby shutting down the R/O unit  30 . As long as the inlet valve  34  remains open and the pump  70  remains activated, the permeate is forced out of the R/O unit  30  through the permeate check valve  42  and into the permeate conduit  40 . The permeate flows through the conduit  40  in the direction B and into the storage tank  46  where it is collected. Permeate also fills the supply conduit  50  and the rinse conduit  54 . Since the rinse valve  56  is closed, the pump  48  maintains the permeate under pressure within the supply conduit  50  and the rinse conduit  54 . Once the supply conduit  50  and the rinse conduit  54  are filled with pressurized permeate, the storage tank  46  begins to till with permeate. 
         [0047]    The volume of the storage tank  46  is monitored by the controller  90  via a switch, such as a float switch positioned within the tank  46 . When the volume of the storage tank  46  reaches a predetermined level or it is otherwise no longer necessary to generate more permeate, the controller  90  closes the inlet valve  32  and deactivates the pump  70  to cease the flow of feed water into the R/O unit  30 . The controller  90  concurrently opens the rinse valve  56 . 
         [0048]    Since the permeate in the supply conduit  50  and the rinse conduit  54  is under pressure, opening the rinse valve  56  causes the permeate within the rinse conduit, the supply conduit and the storage tank  46  to pass through the rinse valve, the check valve  58 , and into the R/O unit  30  as indicated by arrow D. In the case of the pressurized storage tank  47 , the pump  48  is omitted and the pressure within the tank forces the stored permeate through the rinse conduit  54 . In either case, permeate enters the R/O unit  30  and is flushed though the membrane  80  for a predetermined time to remove built up particulates and debris, thereby promoting longevity of the membrane. The controller  90  then closes the rinse valve  56  to cease permeate flow from the rinse conduit  54 . The inlet valve  32  can then be opened and the pump  70  activated to reinitiate the fluid treatment process. This process can be repeated as required or desired. 
         [0049]    Instead of using the pressurized storage tank  47  or the storage tank  46  to flush the membrane  80 , a separate flush accumulator  51  or storage tank may be provided. A fluid connection  63  having a check valve  65  fluidly connects the flush accumulator  51  with the permeate conduit  40  in order to fill the flush accumulator with permeate exiting the R/O unit  30 . A fluid connection  67  fluidly connects an output of the flush accumulator  51  with the rinse conduit  54  leading to back to the R/O unit  30 . 
         [0050]    A valve  59  on the permeate conduit  40  leading to the storage tank  46  is operable to prevent permeate from entering the storage tank while cooperating, with the check valve  65  to pressurize the flush accumulator  51 . When the flush accumulator  51  supplies pressurized permeate to flush the membrane  80 , portions of the supply conduit  50 , illustrated by phantom arrows  53  and  55 , extending from the storage tanks  46  and  47 , respectively, are omitted or isolated from the fluid connection  67  on the flush accumulator  51 . 
         [0051]      FIGS. 2-5  illustrate the R/O unit  30  in accordance with the present invention. As shown in  FIGS. 2-3 , the R/O unit  30  includes a first tube  100  and a second tube  150 . The first tube  100  includes a first end  122  that has an opening  124  and a second end  126  that has an opening  128 . A passage  130  extends the length of the first tube  100  and connects the opening  124  in the first end  100  to the opening  128  in the second end  126 . The second tube  150  includes a first end  152  that has an opening  154  and a second end  156  that has an opening  158 . A passage  160  extends the length of the second tube  150  and connects the opening  154  in the first end  152  to the opening  158  in the second end  156 . The first tube  100  and the second tube  150  may have any shape such as, for example, circular, square, rectangular, triangular, etc. The first tube  100  and the second tube  150  may be constructed of metals, plastics or combinations thereof. 
         [0052]    The pump  70  is used to force the feed water through the R/O unit  30  and is sized to fit within the passage  130  of the first tube  100 . The pump  70  may be a submersible ground water well pump and is connected to a motor  170  that supplies power to the pump. A flexible coupler  71  connected to the pump  70  helps to secure the pump within the R/O unit  30  and absorbs pump starting torque and loads experienced during shipment of the R/O unit. The motor  170  is also sized to fit within the passage of the first tube  100 . The pump  70  and the motor  170 , however, do not occupy the entire passage  130  of the first tube  100  to allow feed water to be collected within the first tube. 
         [0053]    The membrane  80  used for processing feed water into permeate and concentrate is sized to fit within the passage  160  of the second tube  150 . The membrane  80  has a generally rolled, cylindrical shape and includes a first end  82  and a second end  84 . The membrane  80 , however, does not occupy the entire passage  160  of the second tube  150  to allow incoming feed water to collect within the second tube. The membrane  80  may constitute any conventional membrane commonly used in reverse osmosis units. Alternatively or additionally, the membrane  80  may use a nanofiltration element in order to, for example, desalinate the fed water. 
         [0054]    In conventional fluid treatment systems, the reverse osmosis membrane and the pump supplying feed water are provided in separate, spaced apart units requiring additional plumbing connections and floor space. Since both the pump  70  and the membrane  80  of the present invention can be housed in compact tubes  100  and  150  within the same R/O unit  30 , respectively, the present invention provides a very small footprint which is beneficial in both commercial and residential applications. The present invention also eliminates the need for additional plumbing connections between the membrane  80  and the pump  70 . Furthermore, since the pump  70 , the motor  170  for operating the pump, and the membrane  80  are provided in two adjacent, tubes  100  and  150  in fluid communication with one another, any heat generated by the motor during operation of the fluid treatment system  20  is transferred to the feed water, which improves the permeate production rate. 
         [0055]    A suction end cap  200  receives and retains the second ends  126  and  156  of the first and second tubes  100  and  150 , respectively, and a pressure end cap  300  receives and retains the first ends  122  and  152  of the first and second tubes, respectively. When the suction end cap  200  and the pressure end cap  300  are secured to the first and second tubes  100  and  150 , the pump  70  and the motor  170  become retained within the first tube and the membrane  80  becomes retained within the second tube. An O-ring  180  is provided at the first end  122  and the second end  126  of the first tube  100  in order to fluidly the seal the first tube with the pressure end cap  300  and the suction end cap  200 . Likewise, an O-ring  190  is provided at the first end  152  and the second end  156  of the second tube  150  in order to fluidly the seal the second tube with the pressure end cap  300  and the suction end cap  200 . 
         [0056]    A plurality of support rods  194  extend between the suction end cap  200  and the pressure end cap  300 . The support rods  194  are positioned around both the first tube  100  and the second tube  150  and help stabilize the R/O unit  30 . A plurality of rails  430  may be secured to the suction end cap  200  in order to give the R/O unit  30  stability when standing on the floor. Alternatively, the rails  430  may be omitted and wall mount brackets may be secured to the suction end cap  200  and the pressure end cap  300  to mount the R/O unit  30  to the wall. 
         [0057]    The R/O unit  30  may be protected by a removable cover (not shown) that extends over the pressure end cap  300 . The cover may be made of a durable material, such as a polymer, and may include openings or other structure for vertically or horizontally mounting the cabinet and, thus, the R/O unit  30 . A plurality of feet or rolling casters may be secured to the suction end cap  200  or the cover. 
         [0058]    The suction end cap  200  provides an efficient means to route and distribute all fluid flow into, e.g., feed water and permeate rinse water, and out of, e.g., concentrate and permeate, the R/O unit  30  while minimizing plumbing connections and, thus, the likelihood for leakage in the R/O unit. In particular, the inlet valve  34  for controlling the flow of feed water into the R/O unit  30  the suction end cap  200  by a nipple  422  and the feed conduit  32  is coupled to the inlet valve. The pressure switch  400  for monitoring the pressure of the incoming feed water is also mounted to the suction end cap  200 . Alternatively, the inlet valve  34  is mounted in a portion of the suction end cap  200  (not shown). 
         [0059]    The drain fitting  410  for directing concentrate from the R/O unit  30  is also mounted to the suction end cap  200  and the drain conduit  60  is coupled to the drain fitting. If a valve is provided for regulating the concentrate flow to the drain conduit  60  the valve may be mounted in a portion of the suction end cap  200  (not shown). A flow regulating disc  412  regulates the flow of concentrate through the drain fitting  410  and out of the suction end cap  200  and thereby helps to create the back pressure in the R/O unit  30  required to perform reverse osmosis. The permeate check valve  42  for controlling the flow of permeate out of the R/O unit  30  is connected to the suction end cap  200  by a fitting  404  and the permeate conduit  40 . 
         [0060]    The controller  90  for controlling the inlet valve  34 , the pump  70 , and the rinse valve  56  is mounted to the pressure end cap  300  by a nipple  444 . Alternatively, the rinse valve  56  is mounted in a portion of the pressure end cap  300  (not shown). A first wiring harness (not shown) is disposed within an electrical conduit  426  that extends from the controller  90  and is connected to the inlet valve  34  by a fitting  432 . The first wiring harness electrically connects the controller  90  to the inlet valve  34  to enable the controller  90  to control the inlet valve. A second wiring harness  428  extends from the pump motor  170  to the controller  90  to enable the controller to control the motor and thus, control the pump  70 . A temperature switch  450  for monitoring the temperature of the feed water is also mounted to the pressure end can  300 . Furthermore, a pressure gauge  452  for monitoring the pressure of the feed water flowing between the pump  70  and the membrane  80  as well as the permeate rinse valve  56  controlling the flow of permeate rinse into the R/O unit  30  from the rinse conduit  54  are secured via fittings  57  to the pressure end cap  300 . 
         [0061]      FIGS. 6A-D  illustrate the suction end cap  200  in accordance with the present invention. The suction end cap  200  has a generally rectangular shape and is constructed of any substantially rigid material such as metal, plastic or combinations thereof. The suction end cap  200  includes a first recess  202  for receiving the second end  126  of the first tube  100  and a second recess  210  thr receiving the second end  156  of the second tube  150 . The first recess  202  and the second recess  210  are positioned on the same side of the suction end cap  200 . The first recess  202  and the second recess  210  may be circular in shape or otherwise constructed to accommodate the second end  126  of the first tube  100  and the second end  156  of the second tube  150 , respectively. A chamfer  230  extends around, and is coaxial with, each oldie first and second recesses  202  and  210 . The chamfer  230  around the first recess  202  guides the second end  126  of the first tube  100  and the O-ring  180  into the first recess to provide the sealed connection between the first recess and the second end of the first tube. The chamfer  230  around the second recess  210  guides the second end  156  of the second tube  150  and the O-ring  190  into the second recess to provide the sealed connection between the second recess and the second end of the second tube. 
         [0062]    The first recess  202  includes a feed opening  204  that places the first recess in fluid communication with a blind passage  205  that extends away from the first recess to a feed passage  206  extending through a peripheral side of the suction end cap  202 . In other words, together the blind passage  205  and the feed passage  206  may have a substantially L-shaped pathway through the suction end cap  200 . The feed opening  204 , the blind passage  205 , and the feed passage  206  may be circular in shape or may have an alternative shape such as triangular, rectangular, square, etc. The feed passage  206  receives the nipple  422  connected to the inlet valve  34 . 
         [0063]    Accordingly, when the inlet valve  34  is open, feed water flows from the feed conduit  32  and through the inlet valve into the suction end cap  200  via the feed passage  206 . The feed water then flows through the feed passage  206 , the blind passage  205 , the feed opening  204 , and finally into the first recess  202 . This causes the first tube  100  to fill with feed water from the second end  126  towards the first end  122 , thereby submerging the pump  70  and the motor  170 . The O-rings  180  prevent feed water from leaking out of the first tube  100  while the pump  70  and the motor  170  are submerged. It is the feed water supplied by the feed conduit  32  and collected in the first tube  100  that is pumped by the pump  70  to the membrane  80  to undergo reverse osmosis. 
         [0064]    The second recess  210  includes a permeate opening  212  that places the second recess in fluid communication with a permeate passage  214  that extends away from the second recess and through a peripheral side of the suction end cap  200 . In other words, the permeate passage  214  ma have a substantially L-shaped pathway through the suction end cap  200 . The permeate opening  212  and the permeate passage  214  may be circular in shape or may have an alternative shape such as triangular rectangular, square, etc. The second recess  210 , the permeate opening  212 , and at least a portion of the permeate passage  214  are sized to accommodate the membrane  80 . 
         [0065]    The permeate passage  214  receives the permeate fitting  404  connected to the permeate conduit  40  and the check valve  42 . Accordingly, when the inlet valve  34  is open and the pump  70  is activated, feed water is pumped from the pomp to the membrane  80 . The feed water then undergoes reverse osmosis, allowing permeate to pass through the membrane  80  and leaving the concentrate behind. The permeate exits the second end  84  of the membrane  80 , flows through the permeate opening  212 , the permeate passage  214 , and finally out of the suction end cap  200  into the permeate fitting  404 . The O-rings  190  prevent permeate from leaking out of the second tube  150  during the reverse osmosis process. Once permeate enters the permeate fitting  404 , the check valve  42  allows the permeate to flow through the permeate conduit  40  and into the storage tank  46 . 
         [0066]    The second recess  210  also includes a drain opening  216  that places the second recess in fluid communication with a drain passage  218  that extends away from the second recess and through a peripheral side of the suction end cap  200 . In other words, the drain passage  218  may have a substantially L-shaped pathway through the suction end cap  200 . The drain opening  216  and the cram passage  218  may be circular in shape or may have an alternative shape such as triangular, rectangular, square, etc. The feed passage  206 , the permeate passage  214 , and the drain passage  218  may all extend to and through the same peripheral wall of the suction end cap  200 . Alternatively, one or more of the feed passage  206 , the permeate passage  214 , and the drain passage  218  may extend to and through different peripheral walls of the suction end cap  200  from one another. 
         [0067]    The drain passage  218  receives the drain fitting  410  connected to the drain conduit  60  and the drain opening  216  receives the flow regulating disc  412  to regulate the flow of concentrate out of the drain passage and thereby create the back pressure required to perform reverse osmosis. Accordingly, during the reverse osmosis process in the second tube  150 , concentrate from the feed water is maintained in the gap between the membrane  80  and the second tube. The concentrate then flows through the drain opening  216  and the drain passage  218 . Since the flow regulating disc  412  is positioned in the drain opening  216 , fluid flow through the drain passage is restricted. In other words, the flow regulating disc  412  provides a restricted orifice relative to the drain passage  218  such that back pressure is created. It is the back pressure in the drain passage  218  that helps to facilitate the reverse osmosis process within the second tube  150 . The concentrate flows through the flow regulating disc  412  and into the drain fining  410 . The concentrate can then be directed via the drain conduit  60  to a drain or fed to another membrane as described above to cascade the reverse osmosis process. 
         [0068]    The second recess  210  may further include an opening  220  that places the second recess in fluid communication with a recycling passage  222  that extends away from the second recess and into fluid communication with the blind passage  205  and the first recess  202 . The opening  220  thereby places the second recess  210  into fluid communication with the first recess  20  and, thus, into fluid communication with the first tube  100 . 
         [0069]    In operation, some of the concentrate that otherwise would be expelled from the second tube  150  to the drain conduit  60  via the drain opening  216  and the drain passage  218  instead flows through the opening  220  and into the recycling passage  222  to be passed through the blind passage  205  and the first recess  202 . The concentrate is therefore recycled back to the first tube  100  in fluid communication with the first recess  202  and thus, back to the pump  70 . The recycled concentrate is then pumped back through the membrane  80  in order to further separate permeate from the concentrate. A flow regulating disc  406  (see  FIG. 4 ) is secured within the opening  220  via an E-clip  408 . The flow regulating disc  406  regulates the flow of concentrate through the recycling passage  222  and thereby helps to generate the back pressure required to perform reverse osmosis in the membrane  80 . 
         [0070]    As shown in  FIGS. 6B-D , since the recycling passage  222  is in fluid communication with the blind passage  205 , the recycling passage is also in communication with the feed passage  204 . A pressure monitoring passage  226  formed in the suction end cap  200  is in fluid communication with the recycling passage  222  and extends toward the peripheral wall of the suction end cap  200 . A plug (not shown) seals the pressure monitoring passage  226  at the peripheral wall of the suction end cap  200 . 
         [0071]    A pressure monitoring opening  227  formed in the top of the suction end cap  200  with the first and second recesses  100  and  105  is in fluid communication with the pressure monitoring passage  226 . A pressure switch  400  (see  FIG. 4 ) is mounted in the pressure monitoring opening  221  and monitors the pressure of the pressure monitoring passage  226  and, thus, the feed passage  204 . In particular, the pressure switch  400  monitors the pressure of the feed water entering first tube  100  from the feed conduit  32 . If the pressure falls below a predetermined amount, the pressure switch  400  communicates with the controller  90  in order to close the inlet valve  34  and deactivate the pump  70  in order to shut down the R/O unit  30 . 
         [0072]    The opening  220  in the suction end cap  200  is also in fluid communication with a auxiliary passage  224  that extends away from the blind passage  205  and to an auxiliary opening  225  in a peripheral side of the suction end cap. The auxiliary passage  224  and the auxiliary opening  225  are in fluid communication with the recycling passage  222 . The auxiliary passage  224  and the auxiliary opening  225  may be circular in shape or may have an alternative shape such as triangular, rectangular, square, etc. The auxiliary opening  225  receives a plug (not shown) to seal the auxiliary opening and the auxiliary passage  224 . 
         [0073]      FIGS. 7A-D  illustrate the pressure end cap  300  in accordance with the present invention. As with the suction end cap  200 , the pressure end cap  300  provides an efficient means to route and distribute fluid through the R/O unit  30  and, in particular, between the pump  70  and the membrane  80  while minimizing plumbing connections and, thus, the propensity for leakage. 
         [0074]    As noted, the suction end cap  200  and the pressure end cap  300  cooperate to retain the membrane  80  within the second tube  150 . Although the pressure end cap  300  is illustrated as being constructed of a single piece, those having ordinary skill in the art will appreciate that the pressure end cap could be configured such that a portion  301  (see  FIG. 3 ) is removable in order to access the interior of the second tube  150 . The removable portion  301  of the pressure end cap  300  is received in an opening  303  in the pressure end cap and is held against the membrane  80  and within the end cap by a retaining ring  305  that fits within an annular grove  307  in the end cap. By providing access to the interior of the second tube  150 , the membrane  80  within the second tube can quickly and easily be removed and replaced. Although  FIG. 3  illustrates that the pressure end cap  300  includes the removable portion  301  those having ordinary skill will contemplate that the suction end cap  200  may alternatively or additionally include a removable portion for accessing the membrane  80  without removing the suction end cap. 
         [0075]    The pressure end cap  300  has a generally rectangular shape and is constructed of any substantially rigid material such as metal, plastic or combinations thereof. The pressure end cap  300  includes a first recess  302  and a second recess  330  positioned on the same side of the suction end cap  200 . The first recess  302  is ring-shaped and configured to receive the first end  122  of the first tube  100 . The second recess  330  is circular in shape or otherwise configured to receive the first end  152  of the second tube  150 . A chamfer  340  extends around, and is co-axial with, each of the first and second recesses  302  and  330 . The chamfer  340  around the first recess  302  guides the first end  122  of the first tube  100  and the O-ring  180  into the first recess to provide the sealed connection between the first recess and the first end of the first tube  100 . The chamfer  340  around the second recess  330  guides the first end  152  of the second tube  150  and the O-ring  190  into the second recess to provide the sealed connection between the second recess and the first end of the second tube. 
         [0076]    The pressure end cap  300  further includes a pump connection hole  304 . The pump connection hole  304  is configured to receive a threaded portion (not shown) of the pump  70  and constitutes a threaded bore positioned inward of the ring-shaped first recess  302  and. The pump connection hole  304  is in fluid communication with a blind passage  311  that extends away from the pump connection hole and through the interior of the pressure end cap  300 . 
         [0077]    The second recess  330  includes a connection opening  332  that places the second recess in fluid communication with a connection passage  334  that extends away from the second recess and into fluid communication with the blind passage  311 . In other words, the connection passage  334  may have a substantially L-shaped pathway through the pressure end can  300 . The connection opening  332  and the connection passage  334  may be circular in shape or may have an alternative shape such as triangular, rectangular, square, etc. 
         [0078]    The second recess  330  also includes a membrane connection hole  336  that is configured to receive the first end  82  of the membrane  80 . In particular, the membrane connection hole  336  may constitute a blind bore that may be circular in shape or may have an alternative shape such as triangular, rectangular, square, etc. 
         [0079]    Since the connection passage  334  is in fluid communication with the blind passage  311 , the connection passage and, thus, the connection opening  332  is in fluid communication with the pump connection hole  304 . Accordingly, the first tube  100  is in fluid communication with the second tube  150  through the pressure end cap  300 . Due to this configuration the feed water within the first tube  100  is pumped by the pump  70  and exits the pump and the first tube through the pump connection hole  304 . The pumped feed water then flows through the blind passage  311 , the connection passage  334 , through the connection opening  332 , and into the gap between the second tube  150  and the membrane  80 . The feed water submerses the membrane  80  in the second tube  150  and subsequently undergoes reverse osmosis as described. 
         [0080]    Due to the close proximity between the first tube  100  and the second tube  150 , any heat generated by the motor  170  is imparted to the feed water as it flows from the first tube, through the pressure end cap  300 , and to the membrane  80  within the second tube. Heating the feed water increases the rate of permeate production. In other words, since the pressure end cap  300  internally routes the feed water from the first tube  100  to the second tube  150 , there are no external plumbing connections required to supply the feed water from the pump  70  to the membrane  80 . The lack of plumbing connections ensures that the first tube  100  and the second tube  150  are in close proximity to one another and, thus, the feed water surrounding the motor  170  remains heated by the time the feed water reaches the membrane  80 . The lack of plumbing connections in the R/O unit  30  also reduces the likelihood of leakage. 
         [0081]    The pressure end cap  300  further includes a temperature monitoring hole  308  located on a side of the pressure end cap opposite the first recess  302  and the second recess  330 . The temperature monitoring hole  308  may constitute a threaded bore and is in fluid communication with the blind passage  311  and, thus, the pump connection passage  334 . The temperature monitoring hole  308  receives the temperature switch  450  (see  FIG. 3 ) for monitoring the temperature of the feed water flowing between the pump  70  in the first tube  100  and the membrane  80  in the second tube  150 . 
         [0082]    A permeate rinse opening  312  is located on the periphery of the pressure end cap  300  and is in fluid communication with a permeate rinse passage  314 . The permeate rinse passage  314  extends substantially perpendicular to the blind passage  311  and is in fluid communication with the blind passage and, thus, the connection passage  334 . The permeate rinse opening  312  receives a fitting  57 , such as a tee shaped fitting. The fitting  57  is connected to the pressure gauze  452  (see  FIG. 3 ) for monitoring the pressure of the feed water flowing between the pump  70  in the first tube  100  and the membrane  80  in the second tube  150 . The controller  90  communicates with the temperature switch  450  and the pressure switch  400  and ma shut down the R/O unit  30  if the temperature and/or the pressure reaches undesirable, i.e., high or low, levels. 
         [0083]    The fitting  57  is also connected to the permeate rinse valve  56 , the rinse conduit  54  (see  FIG. 1 ), and the check valve  58  (not shown). Since the rinse conduit  54  is in fluid communication with the fitting  57  and, thus, the rinse opening  312 , the rinse conduit is also in fluid communication with the connection passage  334  extending to the connection opening  332 . In operation, once the R/O unit  30  has been shut down, the rinse valve  56  is opened to allow the rinse permeate supplied by the storage tank  46  to flow through the rinse valve and into the rinse opening  312  in the pressure end cap  300 . The rinse permeate then flows through the rinse passage  314 , the blind passage  311 , the connection passage  334 , and out through the connection opening  332  into the second tube  150  in order to flush the membrane  80 . Flushing the membrane  80  removes built up particulate and debris on the concentrate side of the membrane, thereby lengthening the useful life of the membrane. A check valve (not shown) integral with the pump  70  prevents the permeate rinse from flowing backwards through the pump during flushing of the membrane  80 . When flushing of the membrane  80  is complete, the controller  90  closes the permeate rinse valve  56  to shut of the supply of rinse permeate from the storage tank  46 . If desired, the inlet valve  34  can be opened again and the pump  70  activated to reinitiate the reverse osmosis process. 
         [0084]    A control box receiving hole  316  is located on the periphery of the pressure end cap  300  and is in fluid communication with a control box receiving passage  318 . A portion of the control box receiving passage  318  extends substantially perpendicular to the pressure monitoring passage  314  and another portion of the control box receiving passage extends substantially parallel to the blind passage  311 . In other words, the control box receiving passage  318  may have a substantially L-shaped pathway through the pressure end cap  300 . The control box receiving hole  316  receives the controller  90  to mount the controller to the pressure end cap  300 . 
         [0085]    As noted, the second wiring harness  428  (see  FIG. 3 ) connects the pump motor  170  to the controller  90 . In particular, the second wiring harness  428  extends from the motor  170  and within the first tube  100  to the control box receiving passage  318 . A pass through section (not shown) on the second wiring harness  428  seals to the wires and to the passage  318  to prevent feed water from getting into the controller  90 . The second wiring harness  428  then extends through the control box receiving hole  316  and into the controller  90 . 
         [0086]    The temperature monitoring hole  308 , the blind passage  311 , the pressure monitoring opening  312 , the pressure monitoring passage  314 , the control box hole  316 , the control box passage  318 , the connection opening  332 , and the connection passage  334  may be circular in shape or may have an alternative shape such as triangular, rectangular, square, etc. 
         [0087]    It is clear from the above that the suction end cap  200  and the pressure end cap  300  eliminate a multitude of external plumbing connections (see  FIG. 8 ) that are present in conventional fluid treatment systems. For example, the suction end cap  200  and the pressure end cap  300  internally provide all the necessary fluid connections between the R/O unit  30  and the input/output fluid lines, e.g., the feed conduit  32 , the permeate conduit  40 , the permeate rinse conduit  54 , the concentrate conduit  43 , and the drain conduit  60 . The connection opening  332  and the connection passage  334  in the pressure end cap  300  that provide fluid communication between the pump  70  and the membrane  80  also eliminate conventional plumbing connections; as does the integral recycling passage  222  in the suction end cap  200  and the permeate rinse passage  314  in the pressure end cap  300 . By reducing the amount of plumbing connections, the present invention reduces both cost and the likelihood for leaks within the fluid treatment system  20 . The present invention also reduces the overall size of the fluid treatment system  20 , thereby saving floor space. 
         [0088]    In accordance with another embodiment of the present invention, the fluid treatment system and in particular the R/O unit may include more than one membrane for separating permeate and concentrate from feed water in a cascading manner. Such fluid treatment systems may operate with a single pump or multiple pumps.  FIGS. 9A-9C  illustrate several configurations for such a cascading fluid treatment system. Features in  FIGS. 9A-9C  that are substantially identical to features in  FIGS. 1-8  are referred to by the same reference number and similar features are given the suffix. Where the same feature is provided multiple times, each instance of that feature is given the suffix “a, b, c,” etc. 
         [0089]      FIG. 9A  illustrates a fluid treatment system in which the feed conduit  32  supplies feed water to a first membrane  80   a  and a second membrane  80   b  configured in series with one another. In other words, the concentrate exiting the first membrane  80   a  through the drain opening  216  becomes the feed liquid for the second membrane  80   b . The concentrate exiting the second membrane  80   b  is in fluid communication with the drain conduit  60  and the recycling passage  222  for recycling concentrate back through the first membrane  80   a . Permeate from the first membrane  80   a  and the second membrane  80   b  flows through the permeate opening  212  and the permeate passage  214  into the permeate conduit  40  leading to the storage tank  46  (not shown). The serial connection between the first membrane  80   a  and the second membrane  80   b  allows the concentrate exiting the first membrane that otherwise would be discarded to be further purified by the second membrane in order to salvage or generate more permeate. 
         [0090]      FIG. 9B  illustrates an alternative fluid treatment system in which the feed conduit  32  supplies feed water to a first membrane  80   a  and a second membrane  80   b  configured in parallel with one another. In other words, the feed conduit  32  supplies feed water to both the first membrane  80   a  and the second membrane  80   b  at substantially the same time. Permeate from the first membrane  80   a  and the second membrane  80   b  flows through the permeate openings  212   a  and  212   b , respectively and into the permeate conduit  40  leading to the storage tank  46 . 
         [0091]    The concentrate from the first membrane  80   a  and the concentrate from the second membrane  80   b  exit the respective drain openings  216   a  and  216   b  and combine to act as the feed liquid to a third membrane  80   b . The third membrane  80   c  is therefore configured in series with the first and second membranes  80   a  and  80   b . The concentrate exiting the third membrane  80   c  is in fluid communication with the drain conduit  60  and the recycling passage  222  for recycling concentrate back through the first membrane  80   a  and/or the second membrane  80   b . Permeate from the third membrane  80   c  flows through the permeate opening  212   c  and into the permeate conduit  40  leading to the storage tank  46 . 
         [0092]      FIG. 9C  illustrates an alternative fluid treatment system in which the feed conduit  32  supplies feed water to a first membrane  80   a  and a second membrane  80   b  configured in parallel with one another. In other words, the feed conduit supplies feed water to both the first membrane  80   a  and the second membrane  80   b  at substantially the same time. Permeate from the first membrane  80   a  and the second membrane  80   b  flows through the permeate openings  212   a  and  212   b , respectively, and into the permeate conduit  40  leading to the storage tank  46 . 
         [0093]    The concentrate from the first membrane  80   a  exits the drain opening  216   a  and acts as the feed liquid to a third membrane  80   c . The third membrane  80   c  is therefore configured in series with the first membranes  80   a . The concentrate from the second membrane  80   b  exits the drain opening  216   b  and acts as the feed liquid to a fourth membrane  80   d . The fourth membrane  805  is therefore configured in series with the second membrane  80   b.    
         [0094]    The concentrate exiting the third membrane  80   c  is in fluid communication with the drain conduit  60  and the recycling passage  222  for recycling concentrate back through the first membrane  80   a  and/or the second membrane  80   b . Permeate from the third membrane  80   c  flows through the permeate opening  212   c  and into the permeate conduit  40  leading to the storage tank  46 . 
         [0095]    The concentrate exiting the fourth membrane  80   d  is in fluid communication with the drain conduit  60  and the recycling passage  222  for recycling concentrate back through at least one of the first membrane  80   a , the second membrane  80   b , and the third membrane  80   c . Permeate from the fourth membrane  80   d  flows through the permeate opening  212   d  and into the permeate conduit  40  leading to the storage tank  46 . 
         [0096]    Although the fluid treatment systems illustrated in  FIGS. 9A-9C  are illustrative of the configuration of the respective membranes only, those having ordinary skill in the art will appreciate that the fluid treatment systems in  FIG. 9A-9C  may have more than one recycling passage  222  and may include one or more permeate rinse passages  314  in order to flush one or more membranes. Furthermore, those skilled in the art will appreciate that any number of membranes  80  can be configured in any number of parallel and/or serial connections in accordance with the present invention. Accordingly, the suction end cap  200  and pressure end cap  300  may also be configured to accommodate any number of membranes  80  in order to provide the same compact, efficient fluid treatment system having minimal plumbing connections in accordance with the present invention. 
         [0097]      FIGS. 10-13  illustrate an R/O unit  30  that has the four membrane  80   a - d  configuration shown in  FIG. 9C . The R/O unit  30 ′ includes a pump  70  and a motor  170  retained within a first tube  100 . Each of four membranes  80   a - d  is retained in a second tube  150 . The first and second tubes  100  and  150  are closed at their ends by a suction end cap  200 ′ and a pressure end cap  300 ′. Although the suction end cap  200 ′ and the pressure end cap  300 ′ each appear to be made from separate pieces connected together, the suction end cap and/or the pressure end cap may each be made as a single, unitary piece. The pressure end cap  300 ′ may be provided with a removable portion, illustrated by phantom  301 , corresponding with each membrane  80   a - d  in order to access and remove each membrane from each second tube  150   a - d  without completely removing the pressure end cap. A controller not shown) controls operation of the R/O unit  30 ′. The R/O unit  30 ′ may also include some or all of the fittings, sensors, gauges, etc. that the R/O unit  30  includes. 
         [0098]    In operation, the controller opens the inlet valve  34  to allow feed water to enter the R/O unit  30 ′ through the inlet conduit  32 . As with the R/O unit  30 , the feed water may be supplied to the R/O unit  30 ′ under pressure at about 50-70 psi. The pump  70  forces the feed water through the connecting passage  334   a  and the connecting passage  334   b  in the pressure end cap  300 ′ in order to supply feed water to both the first membrane  80   a  and the second membrane  80   b  in parallel. Permeate from the first membrane  80   a  and the second membrane  80   b  flows through the permeate openings  212   a  and  212   b , respectively, out of the suction end cap  200 , and into the permeate conduit  40  leading to the storage tank  46 . In particular, permeate from the first membrane  80   a  flows through the permeate opening  212   a , into the permeate passage  214   a , and into the permeate conduit  40  leading to the storage tank  46 . Permeate from the second membrane  80   b  flows through the permeate opening  212   b , into the permeate passage  214   b , into the permeate passage  214   d , through a permeate transfer element (illustrated schematically by arrow  490  in  FIGS. 11A-B ), into the permeate passage  214   c , and into the permeate conduit  40  leading to the storage tank  46 . The permeate transfer element  490  ma a tube or pipe or any structure capable of directing permeate flow from the permeate passage  214   d  to the permeate passage  214   c.    
         [0099]    Concentrate from the first membrane  80   a  exits the drain opening  216   a  and acts as the feed liquid to the third membrane  80   c . In particular, concentrate from the first membrane  80   a  flows through the drain opening  216   a , the drain passage  218   a  connecting the first membrane  80   a  to the third membrane  80   c , and into an inlet end  462  of a first transfer pipe  460  that extends upwards to the pressure end cap  300 ′ (see  FIG. 13 ). The first transfer pipe  460  terminates at an outlet end  464  within a transfer passage  480   c  in the pressure end cap  300 ′, which is in fluid communication with the third membrane  80   c  via the connection passage  334   c . The third membrane  80   c  is therefore configured in series with the first membranes  80   a.    
         [0100]    Likewise, concentrate from the second membrane  80   b  flows through the drain opening  216   b , the drain passage  218   b , and into an inlet end  472  of a second transfer pipe  470  that extends upwards to the pressure end cap  300 ′ (see  FIG. 13 ). The second transfer pipe  470  terminates at an outlet end  474  within a transfer passage  480   d  in the pressure end cap  300 ′, which is in fluid communication with the fourth membrane  80   d  via the connection passage  334   d . The second membrane  80   b  is therefore configured in series with the fourth membranes  80   d.    
         [0101]    Both of the transfer passages  480   c ,  480   d  extend through the periphery of the pressure end cap  300 ′. Although the transfer passages  480   c ,  480   d  are illustrated as being plugged with plugs  486 , those having ordinary skill will contemplate that one or more of the plugs may be omitted such that concentrate may pass from the transfer passage(s) to for example, additional membranes. Likewise, the drain passages  218   a ,  218   b  extend through the periphery of the suction end cap  200 ′ and are plugged with plugs  486 , although one or more of the plugs may be omitted to allow concentrate to pass from the drain passage(s) to, for example, additional membranes. 
         [0102]    Concentrate exiting the third membrane  80   c  is in fluid communication with the drain conduit  60  via the drain opening  216   c  and the drain passage  218   c . Concentrate exiting the third membrane  80   c  is also in fluid communication with the recycling passage  222  via the opening  220   c  for recycling concentrate back to and through the first membrane  80   a . Permeate from the third membrane  80   c  flows through the permeate opening  212   c  and the permeate passage  214   c  to the permeate conduit  40  leading to the storage tank  46 . 
         [0103]    Concentrate exiting the fourth membrane  80   d  is in fluid communication with the drain conduit  60 . Concentrate from the fourth membrane  80   d  may flow through the drain opening  216   d , the drain passage  218   d , and into a connection passage, illustrated by phantom lines  217  in  FIG. 11B , that is in fluid communication with the opening  220   c  via a connection opening  219 . Concentrate from the fourth membrane  80   d  and, thus, the second membrane  80   b  may therefore flow to the drain conduit  60  via the drain opening  216   c  and/or through the recycling passage  222  via the opening  220   c . Permeate from the fourth membrane  80   d  flows through the permeate opening  212   d , to the permeate passage  214   d , and into the permeate conduit  40  leading to the storage tank  46 . 
         [0104]    From the above configuration, it is clear that a single recycle passage  222 , a single permeate conduit  40 , and a single drain conduit  60  in the suction end cap control fluid processing of all the membranes  80   a - d  in a simple, compact, and efficient manner. This is advantageous for the reasons discussed. 
         [0105]      FIG. 14  illustrates an R/O unit  30 ″ in accordance with another aspect of the present invention. Features in  FIG. 14  that are substantially identical to features in  FIGS. 1-8  are referred to by the same reference number. The R/O unit  30 ″ in  FIG. 14  includes an adjustable flow control element  500  for regulating the flow rate and pressure within the R/O unit. More specifically, the flow control element  500  regulates the flow rate and pressure of concentrate passing through the recycling passage  222  to be recycled by the membrane  80 A as well as concentrate passing through the drain passage  218  to be drained out of the R/O unit  30 ″ via the drain conduit  60 . The flow control element  500  may be positioned within or integral with the suction end cap  200  or may be positioned outside of the suction end cap. 
         [0106]    As noted, concentrate residue leftover from the permeate passing through the membrane  80 A passes through the opening  220  in the suction end cap  200  as a single stream before it is divided between concentrate re-circulated back through the membrane or waste sent to drain. The flow control element  500  receives the single stream from the opening  220  and divides it evenly or unevenly into two streams, namely, a stream passing to the recycling passage  222  and a stream passing to the drain passage  218 . 
         [0107]    Integral with the flow control element  500  are, two fluid resistance elements such as first and second orifices  502 ,  504  that provide resistance to each of the streams heading to the recycling passage  222  and the drain passage  218 . Each of the orifices  502 ,  504  is adjustable to vary the resistance to flow of the respective concentrate stream to the recycling passage  222  and the drain passage  218 . The orifices  502 ,  504  may be separately or simultaneously adjusted. The resistance value for one orifice  502  or  504  may be the same as or different from the resistance value for the other orifice  502  or  504  at any given time. The combined resistance value of the two orifices  502 ,  504  may be constant over the adjustment range. The constant total fluid resistance serves to maintain a constant flow rate from the pump  70 . 
         [0108]    In one aspect of the present invention the adjustable flow control element may comprise a continuously variable flow control element  500  as shown in  FIG. 15 . The flow control element  500  may have a rotary motion adjustment configuration and includes an outer sleeve  510 , an inner sleeve  530  positioned within the outer sleeve, and a flange  550  that connects the inner sleeve to the outer sleeve. The outer sleeve  510  may have a cylindrical or conical shape and extends along, a longitudinal axis  512 . The inner sleeve  530  may have a cylindrical or conical shape and extends along a longitudinal axis  532  aligned with the axis  512  of the outer sleeve  510 . The outer sleeve  510  and inner sleeve  530  may have any shape so long as the outer sleeve and inner sleeve have the same shape. The outer sleeve  510  and inner sleeve  530  mate sealingly with one another (not shown) to ensure that no fluid passes in between the inner and outer sleeves. For example, the inner sleeve  530  may have a flexible zone that when energized from the incoming fluid pressure serves to enhance the sealing engagement between the inner sleeve and the outer sleeve  510  around the orifices  502 ,  504 . 
         [0109]    As shown in  FIGS. 16A-16B , the outer sleeve  510  includes a first opening  514  and a second opening  516  that extend entirely through the outer sleeve. The first and second openings  514 ,  516  are located around the periphery of the outer sleeve  510 . The first and second openings  514 ,  516  may be axially aligned with one another or may be offset. The first opening  514  is configured to direct fluid to the recycling passage  222  of the suction end cap  200  and the second opening  516  is configured to direct fluid to the drain passage  218  of the suction end cap. The first and second openings  514 ,  516  each have a rectangular shape but may alternatively have any shape such as circular, square, triangular, etc. 
         [0110]    An inlet opening  518  extends through the outer sleeve  510  and is in fluid communication with the opening  220  in the suction end cap  200 . The inlet opening  518  receives concentrate from the opening  220  leftover from the reverse osmosis process through the membrane  80 A. The outer sleeve  510  further includes a groove  520  that extends around a portion of the periphery of the outer sleeve  510  at the top of the outer sleeve as viewed in  FIG. 15 . The groove  520  is configured to mate with a portion  560  of the flange  550  to secure the outer sleeve  510  to the flange. 
         [0111]    The inner sleeve  530  is configured for rotation within and relative to the outer sleeve  510  about the axes  512 ,  532  when the inner and outer sleeves are connected to the flange  550 . The inner sleeve  530  ( FIGS. 16C-E ) includes a first opening  534  and a second opening  536  that extend entirely through the inner sleeve to an interior  540  of the inner sleeve. An inlet opening  538  extending through the inner sleeve  510  and into the interior  540  is axially and radially aligned with the inlet opening  518  in the outer sleeve  510  and, thus, the inlet opening  540  is in fluid communication with the opening  220  in the suction end cap  200 . 
         [0112]    Each of the first and second openings  534 ,  536  has a shape with a variable cross-section, such as a wedge or triangular shape. The first and second openings  534 ,  536  may have the same shape or different shapes. As shown in FIGS.  15  and  16 C-D, the first and second openings  534 ,  536  may have the same triangular shape and are positioned about the periphery of the inner sleeve  530  such that each of the first and second openings tapers inwardly, i.e., becomes narrower, in a direction extending away from one another around the periphery of the inner sleeve. Alternatively, the first and second openings  534 ,  536  may have any shape whose width increases in a controlled manner in a radial direction around the inner sleeve  530 , e.g., frustoconical, parabolic. 
         [0113]    The first opening  534  in the inner sleeve  530  is axially and radially aligned with the first opening  514  in the outer sleeve  510  to form the first orifice  502  ( FIG. 15 ). More specifically, the upper and lower boundary edges of the first orifice  502  are defined by the rectangular opening  514  in the outer sleeve  510  and the lateral boundary edges are defined by the variable cross-section opening  534  in the inner sleeve  530 . The second opening  536  in the inner sleeve  530  is axially and radially aligned with the second opening  516  in the outer sleeve  510  to form the second orifice  504 . More specifically, the upper and lower boundary edges of the second orifice  504  are defined by the rectangular opening  516  in the outer sleeve  510  and the lateral boundary edges are defined by the variable cross-section opening  536  in the inner sleeve  530 . The first and second opening  534 ,  536  may be defined by edges of the inner sleeve  530  that are raised in the radially outward direction to increase the localized sealing force on the inner surface of the outer sleeve  510  at the resulting orifices  502 ,  504 . 
         [0114]    The upper portion of the inner sleeve  530  includes an adjustment device  542  ( FIGS. 16C-E ) for rotating the inner sleeve to control the radial position of the openings  534 ,  536  in the inner sleeve relative to the openings  514 ,  516  in the outer sleeve  510 . The adjustment device  542  may receive a tool such as an alien wrench or screwdriver to facilitate rotation of the inner sleeve  530  relative to the outer sleeve  510 . 
         [0115]    As shown in  FIGS. 16F-H , the flange  550  has a generally rectangular shape and receives both the outer sleeve  510  and the inner sleeve  530 . A plurality of mounting holes  554  are provided in the flange  550  to secure the flange and, thus, the flow control element  550  to the suction end cap  200  or other portion of the fluid treatment system  30 ″. The flange  550  includes a passage  352  for slidably receiving the adjustment device  542  of the inner sleeve  530  and a projection  560  that mates with the groove  520  on the outer sleeve  510  to secure the outer sleeve to the flange. When the inner sleeve  530  is inserted into the flange  550  a plurality of teeth  544  on the inner sleeve  530  engage a plurality of mating teeth  558  on the flange  550 . The adjustment device  542  is axially movable relative to the flange  550  such that the teeth  544  of the inner sleeve are releasably engageable with the teeth  558  of the flange  550  to allow the inner sleeve to move to any one of a plurality of radial positions relative to the flange and the outer sleeve  510 . 
         [0116]    The flange  550  further includes indicia  556  corresponding with predetermined radial settings or positions of the inner sleeve  530  relative to the outer sleeve  510 . The indicia  556  terminate at positions indicated at  557  that correlate with the maximum travel of the adjustment device  542  relative to the outer sleeve  510  and, thus, maximum rotation of the inner sleeve  530  relative to the outer sleeve in either direction. 
         [0117]    The flow control element  500  includes structure for limiting rotation of the inner sleeve  530  relative to the outer sleeve  510  to define the radial positions at which the end positions  557  reside. The inner sleeve  530  includes a projection  546  that cooperates with a groove  562  in the flange  550  to limit rotation of the inner sleeve in both the clockwise and counterclockwise directions relative to the outer sleeve  510 . When the adjustment device  542  is positioned within the passage  552  of the flange  550  the projection  546  on the inner sleeve is positioned within the grove  562  on the flange. The adjustment device  542  may rotate in either the clockwise or counterclockwise direction relative to the outer sleeve  510  until the projection  546  engages an end stop  564  at either end of the groove  562 , thereby preventing additional rotation of the inner sleeve  530  in either direction. 
         [0118]    The inner sleeve  530  is rotatable relative to the outer sleeve  510  via the adjustment device  542  to align different portions of the variable cross-section first and second openings  534 ,  536  in the inner sleeve with the constant cross-section first and second openings  514 ,  516 , respectively, in the outer sleeve. At least a portion of the opening  536  in the inner sleeve  530  is always in radial alignment with a portion, however small, of the opening  516  in the outer sleeve  510 . The opening  534 , however, is configured such that the opening  534  can be completely out of alignment with the opening  516 . Moreover, the inlet openings  518 ,  538  in the outer and inner sleeves  510 ,  530  are always at least partially aligned regardless of the radial position of the inner sleeve relative to the outer sleeve. The openings  534 ,  536  in the inner sleeve  530  are configured such that when the inner sleeve rotates relative to the outer sleeve  510  the size of the openings  534 ,  536  in the inner sleeve aligned with the openings  514 ,  516  in the outer sleeve varies. 
         [0119]    As the inner sleeve  530  rotates clockwise relative to the outer sleeve  510  in the direction indicated at R ( FIG. 5 ), the size of the portion of the opening  534  aligned with the opening  514  in the outer sleeve increases while the size of the portion of the opening  536  aligned with the opening  516  in the outer sleeve decreases. The change in size of the openings  534 ,  536  is due to the tapered, non-uniform cross-section of the openings. Likewise, as the inner sleeve  530  rotates counterclockwise relative to the outer sleeve  510  the size of the portion of the opening  534  aligned with the opening  514  in the outer sleeve decreases while the size of the portion of the opening  536  aligned with the opening  516  in the outer sleeve increases. 
         [0120]    Alternatively, the orientation of the openings  534 ,  536  in the inner sleeve  530  may be reversed such that clockwise rotation of the inner sleeve causes the size of the first opening  534  aligned with the opening  514  in the outer sleeve to decrease while the size of the second opening  536  aligned with the opening  516  in the outer sleeve increases, in any case, the total area of the openings  534 ,  536  aligned with the openings  514 ,  516  in the outer sleeve  510  remains substantially constant. Since the openings  514 ,  516  have a fixed cross-section the total area of the orifices  502 ,  504  is therefore substantially constant. Likewise, the combined fluid resistance through the orifices  502 ,  504  remains substantially constant regardless of the radial position of the inner sleeve  530  relative to the outer sleeve  510 . 
         [0121]    The openings  514 ,  516  and  534 ,  536  in the sleeves  510  and  530  provide the only means by which fluid may exit the fluid control element  500 . The variable cross-section openings  534 ,  536  in the inner sleeve  530  therefore dictate the flow rate and pressure of fluid flowing to the openings  514 ,  516  in the outer sleeve  510  and, thus, flow out of the flow control element  500 . By aligning larger or smaller sized portions of the openings  534 ,  536  in the inner sleeve  530  with the uniformly sized openings  514 ,  516  in the outer sleeve  510  the flow control element  500  provides continuously variable flow proportion outputs. 
         [0122]    Since the variable cross-section openings  534 ,  536  in the inner sleeve  530  provide continuously variable flow proportions through the orifices  502 ,  504 , the adjustment device  542  may be set to any position between and including the end positions  557  of the indicia  556  corresponding with predetermined flow proportions through the flow control device  500 . The fineness or amount of mating teeth  544 ,  558  on the inner sleeve  530  and the flange  550  dictate the amount of positions between the end positions  557  in which the inner sleeve  530  can be locked relative to the outer sleeve  510 . As more mating teeth  544 ,  558  are provided the number of different configurations for the alignment of the openings  534 ,  536  with the openings  514 ,  516  increases and, thus, the variability in controlling the flow output through the flow control element  500  increases. 
         [0123]    One end position  557  of the indicia  556  correlates with a position at which a predetermined minimum of the opening  536  in the inner sleeve  530  is aligned with the opening  516  in the outer sleeve  510 . The other end position  557  of the indicia  556  correlates with a position at which the opening  534  in the inner sleeve  530  is completely out of radial alignment with the opening  514  in the outer sleeve  510 . Therefore, the adjustment device  542  can be set to positions in which at least a portion of both openings  534 ,  536  are aligned with the openings  514 ,  516  in the outer sleeve  510  or positions in which only the opening  536  is aligned with the opening  516  in the outer sleeve. This ensures that at least some fluid always flows through the orifice  504  to the drain passage  218  regardless of the position of the adjustment device  542  to prevent excessive pressure build up and damage to the membrane  80 A. 
         [0124]    in operation, the concentrate residue from the membrane  80 A flows through the inlet openings  518 ,  538  into the interior  540  of the inner sleeve  530 . The concentrate is then split by the flow control element  500  according to the preset proportion via the adjustment device  542  in order to direct the concentrate out of the flow control element through the first orifice  502 , i.e., the aligned openings  514 ,  534 , to the recycling passage  222  in the suction end cap and through the second orifice  504 , i.e., the aligned openings  516 ,  536 , to the drain passage  218 . Since the adjustment device  542  may vary the flow proportions through each orifice  502 ,  504  by adjusting the size of the openings  534 ,  536  in the inner sleeve  530  radially aligned with the openings  514 ,  516  in the outer sleeve  510  the flow control element  500  may continuously vary the flow proportions to the recycling passage  222  and the drain passage  218  depending on desired performance criterion in accordance with the present invention. As noted, the combined resistances to fluid flow through the orifices  502 ,  504  remains constant regardless of the particular flow proportions through the orifices dictated by the adjustment device  542 . 
         [0125]    Fluid pressure within the flow control element  500  biases the inner sleeve  530  into any one of a plurality of locked positions relative to the flange  550  and thus, relative to the outer sleeve  510  to prevent the inner sleeve from drifting relative to the outer sleeve once the desired flow proportions have been set by the adjustment device  542 . The teeth  544  on the inner sleeve  530  are biased into engagement with the teeth  558  on the flange  550  such that the inner sleeve can be releasably locked relative to the outer sleeve  510  at an position between and including the end stops  564  dictated by the position of the adjustment device  542 . To overcome the bias of the fluid pressure the adjustment device  542  is forced downward slightly to disengage the mating teeth  544 ,  558  and then rotated accordingly to place the inner sleeve  530  is the desired position relative to the outer sleeve  510 . The downward force on the adjustment device  542  is then released to allow the fluid pressure to bias the mating  544 ,  558  back into engagement with one another, thereby locking the position of the inner sleeve  530  relative to the outer sleeve  510 . 
         [0126]    In another aspect of the present invention the variable cross-section openings  534 ,  536  in the inner sleeve  530  may be replaced with a series of spaced-apart openings having incremental sizes (not shown). In this configuration, the flow control element provides discrete variations in flow pressure and rate to the recycling passage  222  and drain passage  218  rather than continuously variable flow pressure and rate. The openings  534 ,  536  in the discrete flow control element may each constitute a plurality of openings that increase and decrease, respectively, in size around the periphery of the inner sleeve  530  such that the sizes of the aligned openings are inversely related while maintaining a constant total flow area through the flow control element. 
         [0127]    The teeth  544  on the inner sleeve  530  and the teeth  558  on the flange  550  are spaced and configured such that the adjustment device  542  can only be locked to the flange in radial positions that place one of the sets of openings  534 ,  536  in alignment with the openings  514 ,  516  in the outer sleeve  510  to allow concentrate to flow out of the fluid control element  500 . In other words, the inner sleeve  530  cannot be locked in a radial position relative to the outer sleeve  510  that prevents concentrate from exiting the flow control element. 
         [0128]    Similar to the variable flow control element the indicia  556  on the discrete flow control element may correlate with predetermined flow pressures and rates to the recycling passage  222  and the drain passage  218  in the suction end cap  200 . For example, the indicia  556  may correlate with the relative flow proportions shown in Table 1: 
         [0000]                                                                      TABLE 1                       Setting   Recirculation   Waste   Total   Efficiency                                        1   3   1   4   High           2   2.5   1.5   4   . . .           3   2   2   4   . . .           4   1.5   2.5   4   Low                        
The values in Table 1 represent relative flow proportions of concentrate directed to the recycling passage  222 , i.e., recirculation, and concentrate directed to the drain passage  218 , i.e., waste, by the orifices  502 ,  504  in the flow control element. Table 1 illustrates that the cumulative flow of concentrate directed by the discrete flow control element remains constant regardless of the setting or flow proportions.
 
         [0129]    In use, the adjustment device  542  is depressed slightly to overcome the fluid pressure within the flow control element in order to disengage the mating teeth  544 ,  558  on the inner sleeve  530  and the flange  550 . The adjustment device  542  is then rotated to vary the site of the discrete openings  534 ,  536  in the inner sleeve  530  aligned with the openings  514 ,  516  in the outer sleeve  510  until a desired flow pressure and rate through the orifices  502 ,  504  is achieved. Visual verification of the flow proportion through the orifices  502 ,  504  is achieved via the indicia  556 . The downward force on the adjustment device  542  is then released to allow the fluid pressure in the flow control element to bias the teeth  544  of the inner sleeve  530  back into engagement with the teeth  558  on the flange  550 . The inner sleeve  530  is thereby locked in a desired radial position relative to the outer sleeve  530  corresponding with desired concentrate flow proportions to the recycling passage  222  and the drain passage  218  in the suction end cap  200 . 
         [0130]      FIGS. 17-18  illustrate a pressure end cap  300 ″ in accordance with another aspect of the present invention. In  FIGS. 17-18  a pump end bell or adapter  600  is used to secure the pump  48  to the pressure end cap  300 ″ instead of the threaded pump connection hole  304  illustrated in  FIG. 7D . The adapter  600  is configured to provide resistance to rotation of the pump  48  relative to the pressure end cap  300 ″. 
         [0131]    The adapter  600  has a cylindrical shape that includes a head portion  604  and a body portion  620 . The head portion  604  includes an annular recess  610  for receiving an o-ring or seal  611  to help seal the adapter  600  within the pressure end cap  300 ″. At least a pair of projections or shoulders  614  extends from the body portion  620 . Each shoulder  614  includes a threaded passage  612  that extends through the body portion  620  into an inner chamber  624  defined by the body port on. The outer surface of the body portion  620  includes threads  622  configured to threadably engage a casing of the pump  48  in order to seal against water leakage and resist/inhibit unscrewing of the pump casing from die adapter  600 . A cylindrical retaining portion  630  is positioned within the inner chamber  624  of the body portion  620  and is configured to receive a portion of the pump  48  in order to further secure the pump to the adapter  600 . 
         [0132]    The head portion  604  of the adapter  600  is received in a first cavity  700  in the pressure end cap  300 ″ and the body portion  620  of the adapter is received in a second cavity  702 . The first cavity  700  and second cavity  702  are in fluid communication with the connection passage  334  leading to the membrane  80  and the permeate rinse passage  314  (not shown). Together, the surfaces defining the first and second cavities  700 ,  702  in the pressure end cap  300 ″ substantially mirror and mate with the head portion  604  and the body portion  620  of the adapter  600  to prevent relative rotation between the pressure end cap  300  and the adapter  600  and thus, between the pressure end cap and the pump  48  securely fixed to the adapter. 
         [0133]    A series of passages  706  having a counterbore  708  extend through the pressure end cap  300 ″ and are configured to correspond with the number and positioning of the threaded passages  612  in the adapter  600 . The passages  706  terminate at recesses or surfaces  704  of the pressure end cap  300 ″ configured to mate with the shoulders  614  on the adapter  600  to prevent relative rotation between the adapter, the pump  48 , and the pressure end cap  300 ″. 
         [0134]    To secure the adapter  600  to the pressure end cap  300 ″, the head portion  604  is positioned within the first cavity  702  in the pressure end cap such that the seal  611  in the annular recess  610  seals with a surface  710  defining the first cavity. A plurality of fasteners  720 , such as threaded bolts, are fed through the passages  706  in the pressure end cap  300 ″ and threaded into the threaded passages  612  in the adapter  600  until the head of each fastener abuts the counterbore  708  of the passage to securely fix the pressure end cap to the adapter. O-rings or seals  730  may be positioned around the shanks of the fasteners  730  to help seal the connection between the fasteners and the passages  706  in the pressure end cap  300  and allow a small amount of axial free play of the pump  48 . 
         [0135]    When the adapter  600  is secured to the pressure end cap  300 ″ the pump  48  in is fluid communication with the inner chamber  624  of the adapter  600 , which fluidly communicates with the first cavity  700  in the pressure end cap and, thus, fluidly communicates with the connection passage  334  leading to the membrane  80 . The pump  48  may thereby pump the incoming feed water through the adapter  600 , through the pressure end cap  300 ″ and into the second tube  150  having the membrane  80  therein. 
         [0136]    From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.