Patent Publication Number: US-2021178328-A1

Title: Method and system for performing reverse osmosis with integrated pump storage

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 16/801,255 filed Feb. 26, 2020, which claims the benefit of U.S. provisional application 62/810,407 filed Feb. 26, 2019, and U.S. provisional application 62/830,705 filed Apr. 8, 2019. The entire disclosures of each of the above applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to reverse osmosis systems, and, more specifically, to methods and systems for using an elevated reservoir for supplying feed for reverse osmosis. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Reverse osmosis systems typically use a lot of energy during the process. Reverse osmosis systems use a membrane within a membrane housing to separate a stream of liquid (feed) containing dissolved solids into two streams. The first stream is a pure liquid that is formed by passing fluid through the membrane of the reverse osmosis system. This is referred to as permeate. A second stream of liquid also leaves the membrane housing and has a higher concentration of dissolved solids, which is referred to as brine fluid or reject. Pump storage hydraulic energy systems are one way to reduce the overall costs of the system by reducing energy costs. 
     Referring now to  FIG. 1 , a reverse osmosis system  10  according to the prior art is set forth. The reverse osmosis system  10  has a reverse osmosis membrane housing  12  that has a membrane  14  disposed therein. The membrane housing  12  has a feed fluid inlet  12 A, a brine outlet  12 B, and a permeate outlet  12 C. As briefly mentioned above, feed fluid enters the feed fluid inlet  12 A and, with the membrane  14 , divides the fluid into a permeate stream exiting the membrane housing  12  at the permeate outlet  12 C and a brine stream at the brine outlet  12 B. Feed fluid is provided to the feed fluid inlet  12 A from a fluid source  18  through a pipe  22 , a booster pump  20 , a pipe  24 , a pretreatment system  26 , a pipe  28 , a high pressure pump  30  and a pipe  32 . The pipe  32  is coupled to a turbocharger  40  that has a pump portion  40 A and a turbine portion  40 B. The turbocharger  40  may have a common shaft  41  coupling the pump portion  40 A to the turbine portion  40 B. 
     The pump portion  40 A is in fluid communication with the feed fluid inlet  12 A through a pipe  44 . The brine outlet  12 B is coupled to a pipe  46  which in turn communicates brine fluid to the turbine portion  40 B. A drain  48  receives the brine from the turbine portion  40 B. Because the brine fluid within the brine pipe  46  is highly pressurized, the turbine portion  40 B uses the energy of the brine fluid to rotate the pump impeller within the pump portion  40 A and to increase the pressure of the feed fluid. This reduces the amount of pressure required to be generated at the high pressure pump  30 . The brine fluid exiting the turbine portion  40 B has its energy reduced and thus low pressure brine fluid is communicated to the drain  48 . 
     Referring now to  FIG. 2 , a pump storage system  60  according to the prior art is illustrated. The pump storage system  60  is used to accumulate or store hydraulic energy for later use when needed. The fluid source  18  is located at a lower elevation than a reservoir  62 . The reservoir  62  may be a tank or storage pond. The reservoir  62  has a water level  64 . The reservoir  62  is located at an elevated portion of land  66 . A pump-turbine  68  is a combination of a pump this is capable of pumping fluid to the reservoir  62  and act as a turbine drawing fluid from the reservoir  62 . The reservoir  62  is disposed a predetermined distance D above the pump-turbine  68 . A pipe or penstock  70  communicates fluid to and from the reservoir  62  and the pump-turbine  68 . 
     To use electrical resources efficiently, the pump-turbine  68  pumps water from the fluid source  18  to the reservoir  62  when electrical energy is cheap or abundant. When there is an increased demand for electrical energy, water is released from the reservoir  62  and passes through the penstock  70  to the pump-turbine  68  which generates electrical power to be returned to the grid or stored in a battery system at the generator  72 . The generator  72  acts as a motor when pumping water to the reservoir  62  and a generator when water is released from the reservoir to generate electricity. It is not uncommon for the reservoir  62  to encompass many acres of land. Because of geographical limitations, finding an area of land that is adjacent to a large body of water and has suitable elevations is difficult. 
     Referring now to  FIG. 3 , a reverse osmosis membrane housing  12  is incorporated into the prior art system of  FIG. 2 . As well, the pretreatment system  26  is shown in communication with the feed fluid inlet  12 A. The pump-turbine  68  is in communication with alternate forms of energy such as solar panels  76  and wind turbines  78 . Solar panels  76  and wind turbines  78  are unpredictable power sources that are coupled to the pump-turbine  68  through wires  80 ,  82 , respectively. The pump-turbine  68  operates at a speed that is consistent with the available power from the solar panels  76 , the wind turbines  78 , and the elevated water from the reservoir  62 . The reverse osmosis system is most efficient when operating at a relatively steady flow and pressure. The pump-turbine  68  may be used to provide fluid from the fluid source  18  when the solar or wind power are in excess. When the solar power or wind power are in excess, the penstock  70  receives fluid pumped from the fluid source  18  by way of the pump-turbine  68 . The pump-turbine  68  also provides the reverse osmosis housing  12  with fluid and adds to fluid from the reservoir  62  when the amount of fluid from the pump-turbine  68  is not adequate. 
     Referring now to  FIG. 4 , the turbocharger  40  and the membrane housing  12  of  FIG. 1  are incorporated into the prior art system. In this example, the pretreatment system  26  is disposed at the same elevation as the turbocharger  40 . The turbocharger  40  receives brine fluid from the brine outlet  12 B, which is used to pressurize the feed fluid at the pump portion  40 A. Typically, the pump section may raise the feed pressure by about 30 bar, and thus the inlet pressure to the pump is about 30 to 50 bar. The elevation of the reservoir  62  is between 300 and 350 meters, which is reduced from 600 meters in the previous examples and thus the development site costs are reduced. This also increases the amount of development sites possible. The change from 600 to 650 meters or 300 to 350 meters corresponds to systems that do not use versus systems that use a turbocharger, respectively. A large area of land coupled with the need for being close to a large body of seawater is typically very expensive. The required membrane pressure varies due to changes in the feed temperature, the feed water solidity, and the age of the membranes. Therefore, no single reservoir height optimally meets all the membrane operating requirements. 
     The pretreatment system  26  illustrated in  FIG. 3  exposes the equipment to high pressures. The high pressures may approach 65 bar when a turbocharger is not used or 35 bar when a turbocharger is used. Typically, pretreatment systems are rated between 4 and 6 bars using non-metallic construction. Using high alloy stainless steels in the construction of a pretreatment system increases significantly the expense of such systems. Dissolved air filtration is also a preferred method for pretreatment. However, highly pressurized fluid is provided and thus dissolved air filtration cannot be used by such systems. 
     SUMMARY 
     The present disclosure provides a reverse osmosis system and method for operating the same for efficient use of resources in geographic locations having elevated land located adjacent to a fluid source. 
     In one aspect of the disclosure, a reverse osmosis system is coupled to a reservoir and a fluid source below the reservoir. The system includes a first pretreatment system and a first membrane housing comprising a reverse osmosis membrane therein. The membrane housing comprises a feed fluid inlet, a brine outlet and a permeate outlet. A first turbocharger comprises a first pump portion and a first turbine portion. The first pump portion receives feed fluid from the first pretreatment system, pressurizing the feed fluid and communicating the feed fluid to the feed fluid inlet. The first turbine portion receives brine fluid from the brine outlet. A second turbocharger comprises a second pump portion and a second turbine portion. A third turbocharger comprising a third pump portion and a third turbine portion. The second turbine portion and the third turbine portion receives brine fluid from the first turbine portion. The system further comprises a second pretreatment system and a booster pump in series with the second pretreatment system. The second pretreatment system communicates second feed fluid to the second pump portion to increase a pressure of the second feed fluid. The second pump portion communicates second feed fluid to the third pump portion to increase the pressure of the second feed fluid. The third pump portion communicates the second feed fluid to the first pump portion. 
     In yet another aspect of the disclosure. a method of operating the system of the preceding paragraph comprises communicating fluid to a fluid reservoir from the fluid source through a pump-turbine, communicating the fluid through the first pretreatment system to form feed fluid, pressurizing the feed fluid at the first pump portion, communicating the feed fluid to the first feed fluid inlet from the first pump portion, communicating brine fluid from the first brine outlet of first membrane housing to the first turbine portion to operate the first pump portion, communicating brine fluid from the first turbine portion to the second turbine portion to operate the second pump portion and the third turbine portion to operate the third pump portion, communicating second feed fluid from the fluid source through the second pretreatment system to the second pump portion, increasing a pressure of the second feed fluid at the second pump portion, thereafter, communicating the second feed fluid to the third pump portion to increase the pressure of the second feed fluid and communicating the second feed fluid from the third pump portion to the first pump portion. 
     In another aspect of the disclosure, a reverse osmosis system coupled to a reservoir and a fluid source below the reservoir includes a first pretreatment system and a first membrane housing comprising a first reverse osmosis membrane therein. The first membrane housing comprises a first feed fluid inlet, a first brine outlet and a first permeate outlet. A second membrane housing of the system comprises a second reverse osmosis membrane therein. The second membrane housing comprises a second feed fluid inlet, a second brine outlet and a second permeate outlet. A first turbocharger comprises a first pump portion and a first turbine portion. The first pump portion receives feed fluid from the pretreatment system, pressurizes the feed fluid and communicates the feed fluid to the feed fluid inlet. The first turbine portion receives brine fluid from the brine outlet. A second turbocharger comprises a second pump portion and a second turbine portion. A third turbocharger comprises a third pump portion and a third turbine portion. The second turbine portion and the third turbine portion receive brine fluid from the first turbine portion. A booster pump in series with the first pretreatment system communicates second feed fluid to the first pump portion to increase a pressure of the feed fluid. The second pump portion increases the pressure of the feed fluid and communicates the feed fluid to the first feed fluid inlet. The first brine outlet couples first brine fluid to the second feed fluid inlet through the third pump portion. The second brine outlet fluidically is coupled to the third turbine portion and wherein the third turbine portion drives the third pump portion. The third turbine portion communicates the second brine fluid to the first turbine portion. The second turbine portion drives the second pump portion. 
     In another aspect of the disclosure, a method for operating the system of the preceding paragraph comprises communicating fluid to a fluid reservoir from the fluid source through a pump-turbine, communicating fluid from the reservoir to the first turbine portion, said first turbine portion operating the first pump portion, communicating the fluid from the first turbine portion through the pretreatment system to form feed fluid, pressurizing the feed fluid at a booster pump and the first pump portion, communicating the feed fluid to the feed fluid inlet through the first pump portion and the second pump portion, communicating brine fluid from the first brine outlet of first membrane housing to the feed fluid inlet of the second membrane housing through the third pump portion, communicating brine fluid from the second brine outlet to the third turbine portion to operate the third pump portion, and communicating brine fluid from the third turbine portion to the second turbine portion to operate the second pump portion. 
     In yet another aspect off the disclosure, a reverse osmosis system is coupled to a reservoir and a fluid source below the reservoir. The system comprises a first pretreatment system, a booster pump, and a first membrane housing comprising a first reverse osmosis membrane therein. The first membrane housing comprises a first feed fluid inlet, a first brine outlet and a first permeate outlet. A first turbocharger comprises a first pump portion and a first turbine portion. The first turbine portion receives feed fluid from the reservoir. The first pump portion receives feed fluid from first turbine portion through the pretreatment system and the booster pump. The first pump portion pressurizes the feed fluid. A second turbocharger comprises a second pump portion and a second turbine portion. The first pump portion communicates the feed fluid to the feed fluid inlet through the second pump portion. The second turbine portion receives brine fluid from the brine outlet. The second pump portion increases the pressure of the feed fluid and communicates the feed fluid to the first feed fluid inlet. The first brine outlet couples first brine fluid to the second turbine portion. 
     In another aspect of the disclosure, a method of operating the system in the preceding paragraph includes communicating fluid to a fluid reservoir from the fluid source through a pump-turbine, communicating fluid from the reservoir to the first turbine portion, said first turbine portion operating the first pump portion, communicating the fluid from the first turbine portion through the pretreatment system to form feed fluid, pressurizing the feed fluid at a booster pump and the first pump portion, communicating the feed fluid to the feed fluid inlet through the first pump portion and the second pump portion, and communicating brine fluid from the first brine outlet of first membrane housing to the second turbine portion to operate the second pump portion. 
     In another aspect of the disclosure, a reverse osmosis system is coupled to a fluid reservoir having a surface. The system includes a pretreatment system fluidically coupled to the fluid reservoir disposed a predetermined distance below the fluid reservoir. A membrane housing comprising a reverse osmosis membrane therein. The membrane housing comprises a feed fluid inlet, a brine outlet and a permeate outlet. A first turbocharger comprises a first pump portion and a first turbine portion. The first pump portion is fluidically coupled to the fluid reservoir through the pretreatment system. A second turbocharger comprises a second pump portion and a second turbine portion. The brine outlet is coupled to the second turbine portion. The first pump portion is in fluid communication with the feed fluid inlet through the second pump portion. The first turbine portion fluidically coupled to the reservoir. 
     In another aspect of the disclosure, a method of operating the reverse osmosis system of the previous paragraph comprises communicating untreated fluid to a fluid reservoir from the fluid source through a pump-turbine, communicating untreated fluid from the reservoir to the first turbine portion, said first turbine portion operating the first pump portion, communicating the untreated fluid from the reservoir through the pretreatment system to the first pump portion to form feed fluid, pressurizing the feed fluid at the first pump portion, communicating the feed fluid to the feed fluid inlet through the first pump portion and the second pump portion and communicating brine fluid from the first brine outlet of first membrane housing to the second turbine portion to operate the second pump portion. 
     In another aspect of the disclosure, a reverse osmosis system coupled to a fluid reservoir has a surface. The system includes a pretreatment system fluidically coupled to the fluid reservoir disposed a first predetermined distance below the fluid reservoir, a membrane housing comprising a reverse osmosis membrane therein. The membrane housing comprises a feed fluid inlet, a brine outlet and a permeate outlet. A first turbocharger comprises a first pump portion and a first turbine portion. The brine outlet is coupled to a first pipe directing brine fluid to the first turbine portion. The first pump portion is in fluid communication with the feed fluid inlet. The brine outlet is coupled to a first turbine portion. 
     In yet another aspect of the disclosure. a method of operating the system of the preceding paragraph comprises communicating fluid to a fluid reservoir from the fluid source through a pump-turbine, communicating the fluid from the reservoir through the pretreatment system to the first pump portion to form feed fluid, pressurizing the feed fluid at the first pump portion, communicating the feed fluid to the feed fluid inlet through the first pump portion and communicating brine fluid from the first brine outlet of first membrane housing to the first turbine portion to operate the first pump portion. 
     In another aspect of the disclosure, a reverse osmosis system is coupled to a reservoir and a fluid source below the reservoir. The system comprises a storage bag disposed in the reservoir, a pretreatment system communicating the fluid source to the storage bag and a membrane housing comprising a reverse osmosis membrane therein. The membrane housing comprises a feed fluid inlet, a brine outlet and a permeate outlet. A first turbocharger comprises a first pump portion and a first turbine portion. The brine outlet is coupled to a first pipe directing brine fluid to the first turbine portion. The first pump portion couples feed fluid in the storage bag to the feed fluid inlet. The brine outlet is coupled to a first turbine portion. 
     In yet another aspect of the disclosure, a method of operating a reverse osmosis system includes communicating fluid to a fluid reservoir from the fluid source through a pump-turbine, communicating fluid from the fluid source through a low pressure pump booster pump to the pretreatment system to form feed fluid, communicating the feed fluid through a high pressure pump to a bag in the reservoir, communicating the feed fluid from the bag in the reservoir to the first pump portion, pressurizing the feed fluid at the first pump portion, communicating the feed fluid to the feed fluid inlet through the first pump portion and communicating brine fluid from the first brine outlet of first membrane housing to the first turbine portion to operate the first pump portion. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a schematic view of a reverse osmosis system having a turbocharger according to the prior art. 
         FIG. 2  is a schematic view of an elevated reservoir system according to the prior art. 
         FIG. 3  is a schematic view of a reverse osmosis system powered according to alternative energy prior art. 
         FIG. 4  is a schematic view of a reverse osmosis system with a turbocharger according to the prior art. 
         FIG. 5A  is a schematic view of an elevated reverse osmosis system reservoir according to the first example of the present disclosure. 
         FIG. 5B  is a flow chart of a method for operating the system of  FIG. 5A . 
         FIG. 6A  is a schematic view of an elevated reverse osmosis system reservoir according to the second example of the present disclosure. 
         FIG. 6B  is a flow chart of a method for operating the system of  FIG. 6A . 
         FIG. 7A  is a schematic view of an elevated reverse osmosis system reservoir according to the third example of the present disclosure. 
         FIG. 7B  is a flow chart of a method for operating the system of  FIG. 7A . 
         FIG. 8A  is a schematic view of a reverse osmosis system with multiple turbochargers according to a fourth example of the present disclosure. 
         FIG. 8B  is a flow chart of a method for operating the system of  FIG. 8A . 
         FIG. 9A  is a schematic view of a fifth example of a system having a pretreatment system near the body of water in elevation. 
         FIG. 9B  is a flow chart of a method for operating the system of  FIG. 9A . 
         FIG. 10A  is a schematic view of a dual membrane housing reverse osmosis system according to a sixth example of the present disclosure. 
         FIG. 10B  is a flow chart of a method for operating the system of  FIG. 10A . 
         FIG. 11A  is a schematic view of a seventh example of the present disclosure having three turbochargers. 
         FIG. 11B  is an alternate configuration for two of the turbochargers of  FIG. 11A . 
         FIG. 11C  is a flow of a method for operating the systems of  FIGS. 11A and 11B . 
         FIG. 12A  is a schematic view of a tunnel system used for housing the penstock and the piping connecting to a turbocharger. 
         FIG. 12B  is a detailed side view of the tunnel and the reservoir with the pipe therein. 
         FIG. 13  is a block diagrammatic view of a prior art filtration system. 
         FIG. 14  is a schematic view of a pretreatment system according to the present disclosure. 
         FIG. 15  is a schematic representation of a pressurization system used for a heat exchanger. 
         FIG. 16  is a schematic view of a filtration system using a pump system. 
         FIG. 17  is a schematic view of a pre-treatment system having a dual stage depressurization prior to filtration. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
     In the examples below, turbochargers are used as energy recovery devices that use energy in a turbine portion to pressurize fluid at a pump portion. Thus, the energy from the fluid in the turbine stream is recovered. The systems below set forth improvements for reducing energy particularly in elevated areas. 
     Referring now to  FIG. 5A , an improved reverse osmosis system  100  is set forth. In this example, the same components in the background are provided with the same reference numerals. In this example, the feed fluid at the pretreatment system  26  is performed at a relatively low pressure. A bag  110  is disposed within the reservoir  62 . The bag  110  is a closed volume that does not interact with the other fluid within the reservoir  62 . A first pipe  112  communicates fluid from the fluid source  18  to a low pressure booster pump  114 . A pipe  116  communicates fluid from the booster pump  114  to the pretreatment system  26 . The booster pump  114  pressurizes the feed fluid to a pressure suitable for use in the pretreatment system  26 , such as between 3 and 5 bar. A pipe  118  couples the pretreatment system  26  to a high pressure pump  120  provides pressurized fluid to a bag  110  within the reservoir  62 . The booster pump  114  thus provides enough pressure to overcome the elevation of the bag  110 . The pretreatment system  26  is located at about the same elevation as the fluid source  18 . The elevation of the pretreatment system  26  may, for example be within 15 m of the body of water. This allows for the use of a low pressure booster pump  114  to be utilized to move the water from the body of water to the pretreatment system  26 . 
     The reservoir  62  may have a cover  122  disposed thereover to prevent debris from entering into the fluid within the reservoir  62 . This is a concern if a bag  110  is not used. With the use of the bag  110 , the cover  122  is not required. Untreated water from the fluid source  18  may be provided through the pump-turbine  68  and a pipe  124  to the reservoir  62 . The pump-turbine  68  may act as a motor or generator as described above. 
     A pipe  126  provides pretreated water to the pump portion  40 A of the turbocharger  40  which is used in the reverse osmosis process. If a bag  110  is not used, the pipe  126  receives fluid of the turbocharger  40  from the reservoir  62  which is covered by the cover  122 . In either case, the pump portion  40 A receives pretreated fluid. As will be described in more detail relative to  FIG. 7 , sensors and a controller may be used to automate the operation of the system. 
     Referring now to  FIG. 5B , a method of operating the system of  FIG. 5A  is set forth. In step  510  fluid is communicated to the pretreatment system  26  through a low pressure booster pump which boosts the pressure to between 3 and 5 bar. In step  512  the fluid is pretreated using one or more various types of filtration, such as cartridge filters. The pretreated feed fluid is pressurized further at a high pressure pump  120  at step  514  to overcome the elevational change. The pretreated fluid is provided from the high pressure pump  120  to the reservoir  62 . When a bag  110  is used, the pretreated fluid is communicated to the bag  110 . If the bag  110  is not used, the fluid from the reservoir  62  is used. That is, fluid is communicated to the reverse osmosis process through the pump portion  40 A through the pipe  126 . The pipe  126  may be a penstock  70 . The fluid is pressurized that is received by the pump portion  40 A. That is, in step  516  the pressurized feed fluid from the reservoir  62  or more specifically the bag  110 , if used, is communicated to the pump portion  40 A of the turbocharger  40 . The pump portion  40 A pressurizes the feed fluid to an increased pressure where it is provided to the reverse osmosis membrane housing  12 . Permeate passes through the membrane housing  12  and exits the system through the permeate outlet  12 C in step  518 . In step  520  brine fluid is communicated form the brine outlet  12 B through the brine flow adjustment valve  42  and to the turbine portion  40 B of the turbocharger  40 . The brine fluid is highly pressurized and turns the pump portion  40 A to increase the pressure of the fluid entering the membrane housing  12 . In step  522  the depressurized brine fluid is communicated to the fluid source  18 . 
     In step  524 , the reservoir is filled with a pump-turbine  68 . Thus, pretreated water may be handled by the pretreatment system  26 , but the bulk of the water being communicated to the reservoir  62  may be handled by the pump-turbine  68 . The pump-turbine  68  may thus be used for providing power to the entire system when the power available to the system is low or inadequate. Thus, the separated pretreated fluid may be used for the reverse osmosis system while the remainder of this fluid within the reservoir  62  may be used for power generation at the pump-turbine  68  in step  526 . 
     Referring now to  FIG. 6A , the pretreatment system  26  has been moved adjacent to the reservoir  62 . The pretreatment system  26  illustrated in  FIG. 6A  is about 30-40 meters below the surface of the reservoir at a distance D 4 . At this location, a booster pump is not required and the elevational head difference provides sufficient pressure, but not too much pressure, for operation of the pretreatment system  26 . The turbocharger  40  is located at a distance D 5  below the surface of the reservoir  62 , such as between 300 and 500 meters below. 
     Referring now to  FIG. 6B , the operation of the system in  FIG. 6A  is set forth. The reservoir  62  may be filled by the pump-turbine  68  at step  610 . In step  612 , when reverse osmosis is desired, the feed fluid from the reservoir  62  is pretreated at the pretreatment system  26 . In step  614 , the pretreated feed fluid is communicated to the pump portion  40 A of the turbocharger  40 . In step  616 , permeate is formed through the membrane  14 . In step  618 , brine fluid is communicated to the turbine portion  40 B to increase the inlet feed fluid pressure. Low pressure brine fluid is then communicated to the body of water in step  620 . The reservoir fluid may be used for generation of power at the pump-turbine  68  at step  622 . 
     Referring now to  FIG. 7A , the turbine  40 B is provided with a motor  130  that is operated by a controller  132 . The motor  130  coupled to the turbine portion  40 B allows variable boost from the pump portion  40 A that is independent from the power available from the turbine portion  40 B. Thus, the feed pressure to the membrane  14  may be maintained at optimal levels to accommodate changes in the reservoir elevation. During the design phase, changes in reservoir height during filling and draw down, and changes in the feed conditions and membrane age. That is, the temperature and salinity of the feed water may change and thus the controller  132  may change the speed of the motor  130  in response to the temperature and salinity sensed at a temperature sensor  134  corresponding to the temperature of the water at the body of water. As mentioned above, the salinity may also change and thus a salinity sensor  135  may be coupled to the controller  132  and the speed of the motor  130  may be changed in response to the salinity. Likewise, a timer  133  may be used to time the amount of time since the last membrane change. That is, the timer  133  may generate a signal corresponding to the age of the membrane  14  and thus the speed of the motor  130  may be changed accordingly. 
     One or more pressure sensors  136  and flow meters  137  may be used throughout the system. Although not specifically illustrated, the pressure sensors  136  may be located before and/or after the pump-turbine  68 , before and or after the pretreatment system  26 , at the feed fluid inlet  12 A, at the brine outlet  12 B, at the permeate outlet  12 C, before or after the pump portion  40 A, before or after the turbine portion  40 B and at the drain. The controller  132  may be used to control the brine flow adjustment valve  42  at the turbine, the motor  130 , the pump—turbine  68 . In addition the sensors described above can be used in any of the example in  FIGS. 5A, 6A, 8A, 9A, 10A and 11A  including before or after the additional turbochargers, membrane housings and in various piping. Likewise the controller may control the various additional components in the above figures such as additional turbine valves, boost pumps and generators. 
     In this example, the motor  130  allows a wider range of reservoir elevation values over the fluid source  18 . The motor  130  can be used to provide extra rotational force for the turbine portion which in turn provides extra rotational force to the pump portion to increase the pressures generated at the pump portion. For example, the elevation of the reservoir  62  may be between 200 and 400 meters above the fluid source  18 . 
     Referring now to  FIG. 7B , various conditions are monitored in step  710 . As mentioned above, the membrane age, salinity, and water temperature may be among the conditions monitored. In step  712 , the speed of the turbine portion  40 B is changed in response to the conditions monitored in step  710 . The speed of the turbine portion  40 B is changed by changing the motor speed in step  714 . The motor speed directly affects the speed of the turbine  40 B. The motor speed change in step  714  accommodates for differences in the flow to the turbocharger  40 . This allows the distance D 6  to be anywhere about 200 meters and about 400 meters above the level of the fluid source  18 . After step  714 , steps  616 - 622  are repeated. 
     In  FIGS. 7A and 7B , the cover over the reservoir  62  is not needed because the pretreatment system filters the feed fluid from the reservoir  62  prior to entering the turbocharger  40 . 
     Referring now to  FIG. 8A , an example is set forth for even lower reservoir elevations. The distance D 7  corresponds to reservoir heights of around 200 meters. In this example, a second turbocharger  140  is incorporated into the fluid flow. The turbocharger  40  receives treated feed fluid from the pretreatment system  26 . Because of the elevation change, a pressure of about 20 bars is generated based on the elevation and the pumping action of the turbocharger  40 . The pump portion  40 A communicates pressurized fluid at about 20 bar to the pump portion  140 A. 
     The turbine portion  40 B of the turbocharger  40  is fluidically coupled to the pipe  124  between the pump-turbine  68  and the reservoir  62 . The pressure in the pipe  124  drives the turbine  40 B which may be supplemented by the operation of the motor  130  as described above. The motor  130  may operate with the controller and the timer and sensors illustrated above in  FIG. 7A  but have not been repeated in this figure. The turbine  40 B thus operates with fluid that has not been pretreated. The depressurized fluid from the turbine  40 B enters the fluid source  18  through the pipe  144 . 
     The pressurized fluid from the pump portion  40 A is communicated to the pump portion  140 A through a pipe  146 . The pump portion  140 A raises the pressure of the pretreated feed fluid from the 40 bar pressure generated by the pump portion  40 A to about 60 bar, which is a pressure sufficient for the membrane  14 . The pressurized fluid from the pump portion  140 A is communicated to the feed fluid inlet  12 A. Permeate is produced at the permeate outlet  12 C for fluid that passes through the membrane  14 . The brine outlet  12 B is in fluid communication with the turbine portion  140 B through the brine flow adjustment valve  142 . The turbine portion  140 B rotates the pump portion  140 A to add the 20 bar of pressure to the fluid received at the turbocharger  140 . A pipe  148  in fluid communication with the turbine portion  140 B communicates low pressure brine fluid to the fluid source  18 . The total boost of the two turbochargers would typically be 60 bar although the contribution by each turbocharger will be dependent in specific process conditions 
     Referring now to  FIG. 8B , the reservoir  62  is filled using the pump-turbine  68  through a pipe  124 . In step  812 , the untreated water within the pipe  124  may also be communicated to the turbine portion  40 B and returned to the fluid source  18 . In step  814 , pretreated feed fluid is communicated to the first pump portion  40 A. In step  816 , the speed of the motor  130  is adjusted to compensate for various conditions such as the age of the membrane  14 , the temperature of the feed fluid, the salinity of the feed fluid, and the pressure of the feed fluid at the turbine portion  40 B. In step  820 , the pretreated fluid from the first pump portion  40 A is communicated to the second pump portion  140 A. In step  822 , the pump portion  140 A further increases the pressure of the pretreated feed fluid. In step  824 , the pressurized feed fluid from the pump portion  140 A is communicated to the feed fluid inlet  12 A of the membrane housing  12 . In step  826 , the membrane housing generates brine fluid at high pressure and permeate. In step  828 , the pressurized brine fluid from the brine outlet  12 B is communicated through the brine flow adjustment valve  142  to the turbine portion  140 B where the pressure is used to rotate the turbine portion  140 B, which in turn rotates or drives the pump portion  140 A to increase the pressure of the incoming feed fluid. The turbine portion  140 B communicates the depressurized brine fluid to the fluid source  18 . The brine fluid is communicated to the turbine portion  140 B which drives the pump portion  140 A to pressurize the feed fluid. 
     Additional turbochargers may be added to boost the feed pressure from the pretreatment system as needed to meet the feed fluid inlet pressure of the turbocharger  40 . The elevation may be decreased to 100 meters or less using turbochargers in series on the feed stream and parallel on the water from the reservoir. This allows the number of locations that such a system may be implemented to increase. 
     Referring now to  FIG. 9A , another example of a system that includes two turbochargers is set forth. In this example, the pretreatment system  26  is located at a lower elevation such as near the elevation of the fluid source  18 . In this example, non-pretreated water from the penstock  70  is communicated to the first turbine portion  40 B through the brine flow adjustment valve  42 . Fluid from the turbine portion  40 B is communicated to the pretreatment system  26  through pipe  158 A and a booster pump  160  to the first pump portion  40 A. That is, all of the fluid from the turbine portion  40 B is communicated to the pump portion  40 A after being depressurized at the turbine portion  40 B and pretreated through the pretreatment system  26  at a low pressure. The pressure of the feed fluid is increased at the booster pump  160 . The pressure of the feed fluid is then further increased at the pump portion  40 A. The energy of the depressurized fluid is applied to the same fluid on the pump portion after pretreatment. Advantageously, pretreatment is at a lower pressure and the system components are less expensive. 
     The pump portion  40 A is in fluid communication with the pump portion  140 A through the pipe  146  in a similar manner to that illustrated in  FIG. 8A . The feed fluid is further increased in pressure at the pump portion  140 A where it is communicated to the feed fluid inlet  12 A. The brine fluid generated at the membrane housing  12  is communicated through the brine flow adjustment valve  142  to the turbine portion  140 B where the pressure is increased for the feed fluid. Pipe  148  communicates the depressurized brine fluid to the fluid source  18 . 
     Referring now to  FIG. 9B , a method of operating the system illustrated in  FIG. 9A  is set forth. In step  910 , the reservoir  62  is filled using the pump-turbine  68  and the penstock  70 . The reservoir  62  is filled with non-pretreated fluid. In step  912 , untreated water is communicated to the first turbine portion  40 B through the pipe or penstock  70 . The turbine portion  40 B depressurizes the untreated water at the first turbine portion  40 B in step  914 . The untreated water becomes feed fluid by pretreating the untreated water at the pretreatment system  26  is step  916 . In step  918 , the pretreated feed fluid is pressurized at the booster pump  160 . The booster pump  160  communicates the pressurized and pretreated feed fluid to the pump portion  40 A where the feed fluid is further pressurized by action of the motion of the first turbine portion  40 B. That is, the pressurization step  914  results in the re-pressurizing of the feed fluid at the pump portion  40 A. The pressurized feed fluid from the pump portion  40 A is communicated to the pump portion  140 A through the pipe  146 . Steps  822 - 828  are performed in a similar manner and are therefore not repeated in  FIG. 9B . 
     Referring now to  FIG. 10A , additional permeate may be recovered from the feed from the penstock  70  using an additional membrane housing  12 ′. The membrane housing  12 ′ adds a membrane  14 ′, a feed fluid inlet  12 A′, a permeate outlet  12 C′, and a brine outlet  12 B′. A third turbocharger  170  is also used. In this example, the fluid is communicated through the same paths except that the penstock  71  having the turbocharger  40  has been separated from penstock  70  which has the pump-turbine  68 . The feed fluid flows through the penstock  71  to the turbocharger  40  and through the pretreatment system  26  and the booster pump  160  as described above. Fluid is communicated from the pump portion  40 A through the pipe  146  to the second pump portion  140 A. In this example, however, the brine outlet  12 B is coupled to the third pump portion  170 A of the turbocharger  170 . The pump portion  170 A pressurizes the brine fluid to a higher pressure prior to communicating the brine fluid to the second feed fluid inlet  12 A′ of the second membrane housing  12 ′. The membrane  14 ′ generates permeate which exits the membrane housing  12 ′ through the permeate outlet  12 C′. Brine exits the second membrane housing  12 ′ through the brine outlet  12 B′. A pipe  172  communicates brine fluid from the brine outlet  12 B′ to the brine flow adjustment valve  174  of the turbocharger  170 . More specifically, the brine is communicated to the turbine portion  170 B of the turbocharger  170  through the brine flow adjustment valve  174 . The pressure in the brine fluid from the brine outlet  12 B′ is used to pressurize the pump portion  170 A to pressurize the input to the second membrane housing  12 . Because not all of the pressure is removed at the third turbine portion  170 B, the brine fluid is communicated from the third turbine portion  170 B to the second turbine portion  140 B through a pipe  176 . The pressure of the brine fluid within the pipe  176  is used at the second turbine portion  140 B to pressurize the feed fluid at the second pump portion  140 A. 
     Referring now to  FIG. 10B , the reservoir is filled using the pump-turbine  68  in step  1010 . In this example, a separate pipe is used from the penstock  70 . 
     In step  1012 , untreated water is communicated to the first turbine from the reservoir  62  to the penstock  70 . Steps  1014 - 1022  correspond to steps  914 - 922  in which the feed fluid is depressurized at the first turbine portion  40 B, pretreated, and ultimately pressurized at the booster pump  160 , the first pump portion  40 A, and the second pump portion  140 A. The pressure of the pretreated feed fluid is increased at step  1024  prior to entering the feed fluid inlet  12 A of the membrane housing  12 . 
     The brine outlet  12 B of the membrane housing  12  is in fluid communication with the third pump portion in step  1026 . In step  1028 , the third pump portion  170 A pressurizes the feed prior to entering the feed fluid inlet  12 A′. In step  1030 , the brine fluid pressurized by the pump portion  170 A is communicated to the feed fluid inlet  12 A′. 
     In step  1032 , brine fluid is generated at the second membrane housing  12 ′. 
     In step  1034 , the pressurized brine fluid is communicated from the brine outlet  12 B′ to the third turbine portion  170 B. The pressure from the brine fluid is used to increase the pressure of the brine fluid communicated from the first membrane housing  12  to the second membrane housing  12 ′ in step  1036 . 
     In step  1030 , the brine fluid is communicated to the second turbine portion  140 B. In step  1040 , the pressure of the feed fluid to the first membrane housing  12  is increased using the excess pressure in the brine fluid by rotating the turbine portion  140 B which in turn rotates the pump portion  140 A of the second turbocharger  140 . In step  1042 , the depressurized brine fluid from the second turbine portion  140 B is communicated to the fluid source  18 . 
     Referring now to  FIG. 11A , a configuration that is suitable for use when the elevation of the reservoir  62  is between about 300 and 350 meters. In this example, the first turbocharger  40  has a pump portion  40 A fluidically coupled to both the pump portion  140 A of the turbocharger  140  and the pretreatment system  26 . The pump portion  40 A is in fluid communication with a pump portion  240 A of a third turbocharger  240 . The pump portion  240 A is in fluid communication with a pretreatment system  26 ′ and a booster pump  242 . Thus, fluid may be provided to the system in two paths. The pump-turbine  68  communicates fluid through the pipe  244  to the reservoir  62 . In addition, to use the extra energy in an efficient manner, the booster pump  242  provides untreated water to the pretreatment system  26 ′. The pump portion  240 A increases the pressure in the treated fluid from the pretreatment system  26 ′. The pump portion  240 A receives fluid that has been pressurized at the pump portion  240 A. The pump portion  240 A communicates fluid that has been twice pressurized to either the pump portion  140 A or the pretreatment system  26  and ultimately to the reservoir  62 . Pretreated fluid enters the pump portion  140 A where it is pressurized and communicated to the feed fluid inlet of the membrane housing  12 . Permeate is produced at the membrane housing  12  and pressurized brine fluid is removed at the brine outlet  12 B. The pressurized brine fluid is used at the turbine portion  140 B to rotate the pump portion  140 A to pressurize the feed fluid. Because the elevations are great, the turbine portion  140 B may receive more energy in the brine fluid than is required for increasing the pressure in the feed fluid. A generator  248  is used to generate electricity at the turbine portion  140 B. 
     The depressurized brine fluid from the turbine portion  140 B is communicated to pipe  250  which in turn is in fluid communication with pipe  252 . The pipe  252  is in communication with both the first turbine portion  40 B and the second turbine portion  240 B. The brine fluid is communicated to an integral brine flow adjustment valve  42 ,  254  respectively. Each turbine portion  40 B,  240 B rotates in response to the energy within the brine fluid and rotates the pump portion  40 A,  240 A using common shafts, respectively. Fluid from the turbine portions  40 B,  240 B is communicated through respective pipes  256 ,  258  to the fluid source  18 . The brine fluid within the pipes  256 ,  258  has been depressurized. 
     Referring now to  11 B, an alternate configuration for the turbocharger  40 ,  240  are set forth. In this example, the pipe  252  has been eliminated and thus the pipe  250  is in communication with the turbine portion  240 B which communicates partially de-energized brine fluid from the turbine portion  240 B to the pipe  260  which is in fluid communication with the turbine portion  40 B. Thus, the turbine portions  240 B and  40 B are in series rather than parallel as in  FIG. 11A . De-energized fluid from the turbine portion  40 B is communicated through the pipe  256  to the fluid source  18 . The pump portions  240 A,  40 A are also coupled in series in a manner similar to that illustrated above with respect to  FIG. 11A . The configuration set forth in  FIG. 11B  is used when the brine pressure from the turbine portion  140 B is high (such as above 30 bar) and there is a low flow rate. 
     Referring now to  FIG. 11C , a method for operating the configurations set forth above in  FIGS. 11A and 11B . In step  1110 , fluid is communicated to the fluid from the reservoir  62  and is pretreated at the pretreatment system  26  in step  1112 . In step  1114 , pretreated fluid is communicated to the pump portion of the turbocharger  140  and the pressure of the feed fluid is increased at the pump portion  140 A. The pressurized feed fluid is communicated to the membrane housing  12  where brine fluid and permeate are produced. The brine fluid is communicated from the brine outlet to the turbine portion  140 B to recover some of the energy of the brine stream. In the present example, a generator  248  may generate electricity therefrom. Likewise, the energy in the brine stream is used to rotate the turbine which in turn rotates the pump portion  140 A to pressurize the feed fluid in step  1118 . In step  1120 , partially pressurized brine fluid from the turbine portion  140 B are communicated to the turbochargers  40 ,  240  where the pressurized brine fluid is used to pump the pump portions  40 A,  240 A. As mentioned above, the turbine portions may be in parallel as set forth in  FIG. 11A  or in series as set forth in  FIG. 11B . In step  1122 , the depressurized brine fluid is communicated to the fluid source  18 . 
     Water from the fluid source  18  is pretreated in step  1126 . The pretreated water has its pressure increased at the pump portions  40 A,  240 A. As mentioned above, the pressurized water is communicated to the pump portion  140 A or the pretreatment system  26  or both. Fluid entering the pretreatment system  26  may be communicated to the reservoir  62 . Fluid entering the pump portion  140 A is further pressurized by the turbine portion  140 B in step  1130   
     Referring now to  FIG. 12 , a land mass  270  is illustrated. The land mass  270  has a tunnel  272  drilled therein. The tunnel  272  may act as a penstock. The pump-turbine  68  communicates fluid through the penstock  70  which is formed from the tunnel  272 . In this example, the pretreatment system  26  is located adjacent to the reservoir  62 . Pretreated water may be communicated through a pipe  274  that is disposed within the tunnel  272 . The pipe  274  connects the pretreatment system  26  to the pump portion  140 A of the turbocharger  140 . A check valve  276  may be coupled to the pipe  274  and is disposed within the reservoir  62 . The check valve  276  prevents the pipe from dropping lower than the pressure within the penstock  70  and thus the tunnel  272 . The pipe  274  may be formed of a light weight material and thus if a high differential of pressure exists, the pipe may be compromised. That is, a thin wall and light weight construction, such as non-metallic materials, may be used for the pipe  274 . Thus, the check valve  276  prevents the pressure within the pipe from dropping below that of the penstock  70 . The check valve  276  allows water from the reservoir  62  to enter the pipe  274 . A pressure sensor  278  disposed on the check valve  276  may provide a warning signal if it opens to allow operators to make necessary adjustments to restore normal operation to the system. 
     By monitoring the pressure at the pressure sensor  278 , the pressure within the pipe  274  may be monitored to be about 0.5 to 1.0 bar higher than the water in the penstock  70  to keep the pipe stiffened with internal pressure. 
     Referring now to  FIG. 12B , the pipe  274  may be coupled to the tunnel  272  with a flange  280 . An elbow  282  provides an angle within the tunnel  272  so that the end of the pipe  274  extends from the flange  280 . A plurality of struts  284  disposed within the tunnel  272  may attach the pipe  274  within the tunnel  272 . It should also be noted that the density of the untreated water and the pretreated water is the same and thus there is not build-up of pressure difference due to the difference in the fluid density. 
     Referring now to  FIG. 13 , a system according to the prior art set forth. In this example a fluid source  1312  provides fluid to a valve  1314  which in turn provides low pressure fluid to the pretreatment system  26 . Details of the pretreatment system  26  is illustrated in further detail. Filtration of fluids is used to remove suspended solids or dissolve materials. The pretreatment system  26  is illustrated as having a dissolved air flotation tank  1318 . However, other types of filtration systems may be used such as sand filters and cartridge filters. Filtration systems in the prior art are typically designed for operating under relatively low pressure rating such as 10 bar. Some filtration devices are available for up to 15 bar. In some industries such as all of the oil and gas industry, high fluid stream pressures are available but filtration without substantial reduction in pressure must be used. Such filtration equipment is cost prohibitive in many applications. 
     The dissolved air flotation tank  1318  has an outlet  1320  for removing the solids for disposal. The dissolved air flotation tank  1318  has a booster pump  1322  that is used to overcome the flow resistance through a filter  1324 . A drain  1324 A of the filter  1324  removes undesired solids for disposal. Once the filtered fluid leaves the pretreatment system  26 , a high-pressure pump  1326  provides high pressure fluid to a process such as to a reverse osmosis system membrane housing  1328  that has a reverse osmosis system membrane  1330  therein. High pressure brine fluid is removed from the housing  1328  through a pipe  1332 . A valve  1334  controls the amount of brine fluid that is provided to a drain  1336 . Permeate flows from the housing  1328  through the permeate outlets  1338 . The permeate is at low pressure. The low-pressure permeate is communicated to a high pressure pump  1340  for further processing by a process  1342 . The pump  1326  is heavy and requires a very large motor and power supply for a typical system such as a reverse osmosis system. 
     Referring now to  FIG. 14 , and improved filtration system  1410  is set forth. The pretreatment system  26  is configured in a similar manner to that set forth above in  FIG. 13  and thus will not be described in detail. In this example, the high pressure fluid is communicated from the source  1312  through a pipe  1412 . The high-pressure fluid is communicated to a turbocharger  1420 . In particular, the high-pressure fluid is communicated to an auxiliary nozzle  1422  to a turbine portion  1420 A of the turbocharger  1420 . The turbine portion  1420 A depressurizes the high-pressure fluid prior to entering the pretreatment system  26  through the pipe  1424 . The depressurized fluid from the fluid source  1312  is filtered and communicated through a low pressure pipe  1426  to the pump portion  1420 B of the turbocharger  1420 . The pump portion  1420 B pressurizes the low-pressure filtered fluid from the pretreatment system  26 . A motor (motor/generator)  1432  having a shaft  1434  which is common to both the turbine portion  1420 A and  1420 B may be used to rotate the pump portion  1420 B to increase the pressure as needed to a desired pressure. The pressurized fluid leaves the pump portion  1420 B and is communicated to the process  1430  through a pipe  1440 . When the process  1430  requires a higher pressure than that which the pump portion  1420 B can provide, the motor  1432  rotates to increase the pressure provided by the pump portion  1420 B. When excess power is provided by the pump portion  1420 B, the motor  1432  acts as a generator to generate electrical energy for other equipment. That is, when the turbine portion  1420 A rotates, the generator can absorb some of the excess electrical power so that that the pump is providing a lower amount of pressure as required by the system. 
     Referring now to  FIG. 15 , the energy recovery system may also be used with a heat exchanger  1510 . The heat exchanger  1510  has a plurality of thin metal passages to achieve the highest possible heat transfer for either heating or cooling a fluid. In this example for cooling, a pipe  1518  provides heated fluid to the heat exchanger  1510  with the excess heat removed from the fluid supplied by the pipe  1518 . Cooling fluid is provided to the heat exchanger  1510  through the inlet pipe  1512 . The outlet pipe  1514  communicates the cooling fluid away from the heat exchanger  1510 . The temperature of the fluid at the pipe  1514  is increased due to the heat exchanging process. The low-pressure fluid is then communicated through the outlet pipe  1520  to the pump portion  1420 B of the turbocharger  1420 . 
     In operation, the high-pressure fluid from the source  1312  is communicated through the auxiliary nozzle  1422  and is depressurized at the turbine portion  1420 A. The depressurized fluid is provided through the pipe  1518  and through the heat exchanger  1510 . Fluid from the heat exchanger is communicated to the pump portion  1420 B. The heat exchanger  1510  may be used for heating or cooling the fluid from the source  1312 . The pressure of the depressurized fluid is increased at the pump portion  1420 B to be used in a process  1430 . 
     Referring now to  FIG. 16 , one example of a pump for use in providing depressurized fluid to the pretreatment system  26  is illustrated. In this example the turbocharger of the previous figures has been replaced by a direct acting pump  1610 . The direct acting pump  1610  receives unfiltered high-pressure fluid for depressurization and eventual communication to the pretreatment system  26 . The direct acting pump  1610  re-pressurizes the filtered fluid in the pipe  1612  with a pump  1614  and the direct acting pump  1610 . The re-pressurized fluid is provided to the process chamber  1618 . 
     Many types of direct acting pumps may be used. In this example, the direct acting pump  1610  includes a first chamber  1620 A and a second chamber  1620 B. A partition  1622 A is located in the first chamber  1620 A to separate the first chamber into two volumes; an upper volume and lower volume. A second partition  1622 B is located in the second chamber  1620 B to separate the second chamber  1620 B into an upper volume or lower volume. The partitions  1622 A,  1622 B move freely to prevent the unfiltered fluid from mixing with the filtered fluid. 
     Unfiltered fluid is provided to the chamber  1620 A,  1620 B through a four way valve  1626  from the fluid source  1312 . The four way valve  1626  alternately transmits high pressure unfiltered process fluid to one chamber while allowing low-pressure fluid to drain from the other chamber. The four way valve  1626  is coupled to the pretreatment system  26  through the pipes  1630 . The upper volumes of the chambers  1620 A and  1620 B receive the untreated fluid. Filtered fluid is received and the bottom portions of the chamber  1620 A and  1620 B through ports  1632 A and  1632 B. 
     The pump  1614  and the lower portion of the chamber  1620 A,  1620 B are coupled to the process chamber  1618  through pipe  1616 . As was mentioned above, the chambers  1620 A,  1620 B alternate in providing low-pressure fluid to the pretreatment system  26 . Likewise, high-pressure fluid that has been filtered by the pretreatment system  26  is provided to the process chamber  1618  from the direct acting pump  1610 . A plurality of check valves  1640 A- 1640 D allow fluid to be communicated from the pump  1614  to the lower portion of chambers  1620 A,  1620 B or from the chambers  1620 A,  1620 B to the process chamber  1618 . The pump  1614  raises the filtered fluid pressure sufficiently high to force unfiltered fluid through the pretreatment system. In a typical situation it is believed that between four and five bars of pressure may be provided by the pump  1614  to increase the pressure of the filtered fluid beyond the capability of the direct acting pump  1610 . 
     In operation, as one chamber is filling with untreated fluid the other chamber is exhausting low-pressure fluid to the pretreatment system  26 . Likewise, when one chamber is filling with filtered fluid the other is exhausting the filtered fluid to the process chamber  1618 . 
     Referring now to  FIG. 17 , the pretreatment system  26  is illustrated with the same components illustrated above and will not be described in more detail. In this example, the fluid source  1312  communicates high-pressure unfiltered fluid to a first turbocharger  1712  and in particular to a turbine portion  1712 A of the first turbocharger  1712  through an auxiliary nozzle  1714 . The first turbocharger  1712  (turbine portion  1712 A) partially depressurizes the pressurized fluid from the fluid source  1312 . The partially depressurized fluid is communicated to a second turbocharger  1716  and, in particular, to a second turbine portion  1716 A. The turbocharger  1716  depressurizes the feed fluid for a second time for communication into the pretreatment system  26 . 
     The outlet pipe  1720  of the pretreatment system  26  is used to communicate filtered (pretreated) fluid to the pump portion  1712 B of the first turbocharger  1712 . The pump portion  1712 B pressurizes the filtered fluid and communicates the filtered and pressurized fluid to the third turbocharger  1726 . In particular, the pretreated partially pressurized filtered fluid is communicated to a pump portion  1726 B of the turbocharger  1726 . The pump portion  1726 B further pressurizes the fluid from the second pump portion  1712 A. The pressurized and filtered feed fluid is communicated to the reverse osmosis housing  1730 . A portion of the pressurized feed fluid passes through the membrane  1732  and leaves the housing  1730  through a permeate outlet  1734 . The permeate which is under low pressure is communicated through the pipe  1736  to the pump  1738 . The pump pressurizes the permeate to the pump portion  1716 B where it is communicated to a process  1740  under high pressure. The pressure of the low pressure permeate is increased at the pump  1738  and pump portion  1716 B. 
     In the reverse osmosis system housing  1730 , a brine outlet  1746  communicates high-pressure brine fluid through an auxiliary valve  1748  to the turbine portion  1726 A of the third turbocharger  1726 . The pressure from the brine fluid is used to increase the pressure of the fluid from the second pump portion  1712 A. That is, the energy from the brine fluid at the turbine portion  1726 A is converted into pressurizing the inlet to the reverse osmosis system housing  1730 . Fluid passing through the turbine portion  1726 A is communicated to the drain  1750 . The fluid to the drain  1750  is depressurized. It should be noted that the turbocharger  1716  and the pump portion  1716 B provide the filtered fluid with the bulk of the pressure while being supplemented by the pump  1738 . 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.