Abstract:
An energy efficient membrane based desalination process, which utilizes an osmotically driven energy recovery sub-process. Energy recovery sub-process involves the extraction of water from low salinity first aqueous solution by using a high salinity content, pressurized second aqueous solution to draw the water from first aqueous solution across a semi-permeable membrane. High salinity content, pressurized second solution can be used to generate osmotic pressure on the low salinity content first solution to drive water from first solution to the second solution with respect to chemical potential differences. The process also harvests the Gibbs free energy of mixing in terms of pressure conservation in the second solution, while the volume of second solution is increasing by the drawn water from the first solution.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates generally to the field of water treatment and energy recovery. More particularly, the invention relates to high salinity water treatment, seawater desalination, pressure recovery from desalination processes, energy production from desalination processes or any other rejection of solutes from a high salinity aqueous solution and related energy and/or pressure recovery. 
       BACKGROUND OF THE INVENTION 
       [0002]    Due to the constant increasing demand for potable water for drinking and irrigational use, seawater desalination maintains its importance. Furthermore, economically feasible and large scale seawater desalination is specifically important because of the continuous growth in the population and related growth of the industry. Even though, membrane based desalination is less energy intensive process, compared to thermal desalination, the energy consumption is still high and needs to be lowered with a more environmentally friendly and economically feasible desalination process. 
         [0003]    Several methods for less energy intensive desalination have been developed including forward osmosis and harvesting of hydraulic energy from a direct osmosis process (PCT/US02/02740, PCT/ES2011/070218). Despite its theoretical energy free mechanism, no feasible applications have been found for forward osmosis. The main problem with the forward osmosis is the extraction of the drawn water from draw solution and the recovery of the draw solution with a continuous and feasible process. On the other hand pressure retarded osmosis (PRO) has been proven to be more than promising process for energy production and recovery process (Statkraft Osmotic Power Pilot Plant, Norway). However, an innovative engineering design for the maximum energy recovery and/or production is required for the commercialization of the PRO process. 
         [0004]    The driving force of the osmotic process is the osmotic pressure difference between the two aqueous solutions on the opposite sides of the semi-permeable membrane. Osmotic pressure of an aqueous solution can be calculated by using Van&#39;t Hoff relation: 
         [0000]      π=θ· v·c·R·T.  
 
         [0005]    where, v is the number of ions produced during dissociation of the solute, θ is the osmotic coefficient, c is the concentration of all solutes (moles/l), R is the universal gas constant (0.083145 l·bar/moles·K), and T is the absolute temperature (K). 
         [0006]    The water flux through a semi-permeable membrane by osmotic pressure difference is given as (McCutcheon and Elimelech, 2007): 
         [0000]        J   w   =A (π D,b −π F,b )
 
         [0007]    where, Jw is the water flux through the semi-permeable membrane, A is the pure water permeability coefficient of the semi-permeable membrane, πD,b and πF,b are the bulk osmotic pressures of draw and feed solutions, respectively. 
         [0008]    PRO can be used to generate or recover energy (power) by utilizing the Gibbs free energy of mixing with respect to the salinity difference of two aqueous solutions (Sandler, S. I.,  1999 , Chemical Engineering Thermodynamics, 3rd ed.; Wiley). 
         [0000]      −Δ Gmix=RT{[Σx   i  ln(γ i   x   i )] M −θ A   [Σx   i  ln(γ i   x   i )] A −θ B   [Σx   i  ln(γ i   x   i )] B }
 
         [0009]    where, xi is the mole fraction of species i in solution, R is the gas constant, T is temperature, and γ is the activity coefficient of the species. 
         [0010]    In a PRO system, a constant hydraulic pressure is applied on the high salinity aqueous solution and permeation of water from low salinity aqueous solution continues while the osmotic pressure difference of two solutions is higher than the applied hydraulic pressure. Pressure of the high salinity aqueous solution can be conserved with the additional energy from Gibbs free energy of mixing while the volumetric flux of the solution increases. Yip and Elimelech (2012) found that the highest extractable work in a constant-pressure PRO process is 0.75 kWh/m3 when seawater and river water were used for draw and feed solutions, respectively. Therefore harvested Gibbs free energy of mixing, in terms of pressure and volume, can be used to produce energy and/or recover pressure. 
         [0011]    In case of energy production; a water turbine can be used to generate power by utilizing the pressure and volumetric flux of the aqueous solution. Even though the modern Pelton turbines can reach up to 92% efficiency, the average efficiency is generally around 90%. 
         [0012]    In case of pressure recovery; there has not been an engineering application to use the harvested Gibbs free energy of mixing with a PRO process for pressure recovery of a membrane desalination process. Modern seawater reverse osmosis processes use pressure exchangers to recover pressure from the brine and to pre-pressurize the seawater before entering the RO process. In this way, up to 60% of the required energy for pressurizing the seawater for RO process can be saved. Modern pressure exchangers, such as isobaric pressure exchangers, can reach an efficiency of 97%. Therefore pressure recovery can be a better alternative than energy production for membrane based seawater desalination because of its higher recovery efficiency. 
       SUMMARY OF THE INVENTION 
       [0013]    The invention provides a method of integrating an osmotic process, such as PRO, into the membrane based (or pressure driven) desalination process, such as SWRO, in order to lower the energy consumption of the SWRO process by harvesting Gibbs free energy of mixing in terms of pressure conservation. 
         [0014]    The inventive method of energy recovery is illustrated by a first embodiment of the invention in which pre-treated high salinity aqueous inlet solution, such as seawater, is exposed to two different pressure exchange devices in order to manipulate the pressure of the solution. First of the two pressure exchange devices is set to increase the pressure of the inlet aqueous solution to a lower level than the second pressure exchange device. Inlet aqueous solution from first and second pressure exchange devices are then exposed to a further pressure manipulation by two different devices, such as pumps, in order to elevate the pressure of the final inlet aqueous solution to a level which is suitable for membrane based desalination, such as SWRO. 
         [0015]    The low salinity aqueous solution, from membrane based desalination process, is then taken as a product and can be used for potable purposes. 
         [0016]    High salinity and high pressure product from the membrane based desalination process, named as brine, is then given to the second pressure exchange devise, where the pressure of the brine stream is lowered by the pressure exchange device. Low pressure brine stream is then given to the third pressure manipulation device, such as pump, where the pressure of the stream is increased to moderate level. 
         [0017]    Moderate pressure brine stream, named as draw solution, is then given to an osmotic membrane process, such as PRO, where it is exposed to the first surface of the semi-permeable membrane. A second low salinity aqueous solution, named as feed solution, such as treated wastewater, brackish water, or surface water, is exposed to the second surface of the semi-permeable membrane. Before it is exposed to the second surface of the semi-permeable membrane, feed solution is given to a pretreatment and/or pressure and volumetric flow rate manipulation device, such as filtration and pumps. 
         [0018]    The concentration gradient between draw and feed solutions then draws the water from the feed solution through the semi-permeable membrane and into the draw solution increasing the volumetric flow rate of the draw solution. During the drawing process of water from feed to draw solution, the mixing of the water, which is drawn through the semi-permeable membrane and has low salinity, and the draw solution releases the Gibbs free energy of mixing. The released Gibbs free energy of mixing is harvested in terms of pressure conservation and keeps the pressure of the draw solution relatively constant while the volumetric flow rate of the draw solution increases. 
         [0019]    Concentrated feed solution is then taken from the osmotic membrane process and can be recycled back to its source or can be used in a further treatment process. 
         [0020]    Diluted, moderate pressure and high volumetric flow rate draw solution, which has the same volumetric flow rate as the inlet aqueous solution which is given to the first pressure exchanger device, in order to pressurize the inlet high salinity aqueous solution. 
         [0021]    After pressure exchange, low pressure high volumetric flow rate draw solutions are taken from the process and can be disposed or can be used in further treatment process. 
         [0022]    Above mentioned process parameters are to be adjusted with respect to the quality and quantity data for the inlet aqueous solutions and desired system parameters. The data can be collected by using various methods including but not limited to; literature review, bench and/or pilot scale experiments, quality monitoring, and etc. 
         [0023]    Additional features, advantages, and embodiments of the invention may be set fourth or apparent from consideration of the following detailed description, drawings, and claims. Moreover, it is to be understood that both the foregoing summary of the invention and the following detailed description are exemplary and intended to provide further explanation without limiting the scope of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the detailed description serve to explain the principles of the invention. In the drawings: 
           [0025]      FIG. 1  is the first preferred schematic diagram of the water treatment method in accordance with the invention. 
           [0026]      FIG. 2  is the detailed exemplary flow diagram of the first preferred schematic diagram of the water treatment method in accordance with the invention. 
           [0027]      FIG. 3  is the exemplary mass and energy balance of the detailed osmotic membrane process which is used in the first and second preferred schematic diagram of the water treatment method in accordance with the invention. 
           [0028]      FIG. 4  is the second preferred schematic diagram of the water method in accordance with the invention. 
           [0029]      FIG. 5  is the detailed exemplary flow diagram of the second preferred schematic diagram of the water treatment method in accordance with the invention. 
           [0030]      FIG. 6  is the exemplary mass and energy balance of the detailed osmotic membrane process which is used in the second preferred schematic diagram of the water treatment method in accordance with the invention. 
           [0031]      FIG. 7  is the third preferred schematic diagram of the water method in accordance with the invention. 
           [0032]      FIG. 8  is the detailed exemplary schematic diagram of the third preferred schematic diagram of the water treatment method in accordance with the invention. 
           [0033]      FIG. 9  is the exemplary mass and energy balance of the detailed osmotic membrane process which is used in the third preferred schematic diagram of the water treatment method in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    The invention is generally directed to a method and apparatus for energy efficient desalination process. Both the method and the apparatus of the invention, for three preferred embodiments, are shown and described with reference to  FIGS. 1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 , and  9 . Throughout the description like reference numbers are used in all figures to describe same features. 
         [0035]    As for the first preferred embodiment,  FIG. 1  is the first preferred schematic diagram of the water treatment method in accordance with the invention, and  FIG. 2  is the detailed exemplary flow diagram of the first preferred schematic diagram of the water treatment method in accordance with the invention, and  FIG. 3  is the exemplary mass and energy balance of the detailed osmotic membrane process which is used in the first and second preferred schematic diagram of the water treatment method in accordance with the invention. 
         [0036]    As shown in  FIG. 1 , the inlet solution with high salinity stored in chamber  1 , for example, pretreated seawater is given to the first pressure exchange device  36  as the first solution  2  and is pressurized. Pressurized first solution  57  is then separated to the second solution  70  and the third solution  56  by means of separation for example, multi-way valve, and then the third solution  56  is exposed to the second pressure exchange device  17 . Pressurized third solution  46  in the second pressure exchange device  17  is further exposed to the first pressure manipulation device  19 , for example, booster pump. 
         [0037]    The second solution  70  is exposed to the second pressure manipulation  58 , for example, high pressure pump, and pressurized second solution  10  is mixed with further pressurized third solution  47 , and the fourth solution which is the mixed solution of pressurized second solution  10  and further pressurized third solution  47 , is given to the first osmosis chamber  11  which includes the first semi-permeable membrane for desalination, for example, reverse osmosis. 
         [0038]    Low salinity and potable quality solution  12 , for example, permeate or product water, is taken from the first osmosis chamber  11  and is given to the chamber  13  for further use, such as drinking, irrigation, or industrial use. 
         [0039]    The fifth solution  14  which is the fourth solution with high pressure and concentrated by being exposed to the first semi-permeable membrane of the first osmosis chamber  11 , is exposed to the second pressure exchange device  17  for pressurizing the third solution  56 . 
         [0040]    The pressure of the fifth solution  14  is lowered after being exposed to the second pressure exchange device  17 . Low pressure fifth solution  50  is than exposed to the third pressure manipulation device  51 , such as booster pump, where the low pressure fifth solution  50  is pressurized to the desired levels. 
         [0041]    The fifth solution pressurized in the third pressure manipulation device  51 , as high salinity and high pressure fifth solution  52 , is given as draw solution to the second osmosis chamber  25  where the high salinity and high pressure fifth solution  52  is exposed to the first surface of the second semi-permeable membrane for osmotically driven process. 
         [0042]    Meanwhile, the chamber  62  stores any one or more than one of the primary treated wastewater, the secondary treated wastewater, the tertiary treated wastewater, brackish water, ground and surface water, and the sixth solution  63  which has lower salinity than the high salinity and high pressure fifth solution  52 , is given to the chamber  28 , where the quality, quantity, pressure and volumetric flow rate of the sixth solution  63  is adjusted to the desired levels for said second semi-permeable membrane. Chamber  28  may include any manipulation device to differentiate pressure and volumetric flow rate with respect to desired quality and quantity of the aqueous solution. 
         [0043]    Manipulated sixth solution  64  is then given to the second osmosis chamber  25  as a feed solution, and exposed to the second surface of the second semi-permeable membrane. The salinity gradient between the high salinity and high pressure fifth solution  52  and the manipulated sixth solution  64  draws water from the manipulated sixth solution  64  to the high salinity and high pressure fifth solution  52 , increasing the volumetric flow rate of the high salinity and high pressure fifth solution  52 . 
         [0044]    Said first and second semi-permeable membrane may be chosen from those of nano osmosis membrane, reverse osmosis membrane, PRO membrane, RO membrane, NF membrane, etc. 
         [0045]    Drawn water from the manipulated sixth solution  64  through the second semi-permeable membrane in the second osmosis chamber  25  has a very low salinity, and when said drawn water is mixed with the high salinity and high pressure fifth solution  52 , the salinity gradient between two solutions releases Gibbs free energy of mixing. Released Gibbs free energy of mixing conserves the moderate pressure level in the high salinity and high pressure fifth solution  52 . 
         [0046]    Diluted fifth solution  59  which has larger volumetric flow rate and relatively same pressure with the high salinity and high pressure fifth solution  52 , is taken from the second osmosis chamber  25 , and is given to the first pressure exchange device  36  for pressurizing the first solution  2 . Depressurized fifth solution  60  is then given to chamber  61  for further treatment or disposing processes. 
         [0047]    Meanwhile, concentrated sixth solution  65 , which lost water by being exposed to the second semi-permeable membrane, is given to the chamber  66  for further treatment or saving. 
         [0048]      FIG. 2  shows a detailed exemplary diagram of the mass balance of the first preferred embodiment including the salinity, volumetric flow rate, and pressure specifications of the solutions. Mass balance calculations are based on 100 m 3 /h volumetric flow rate of inlet high salinity aqueous solution, such as pre-treated seawater, 50% recovery efficiency of first semi-permeable membrane process, such as SWRO, of the first osmosis chamber  11 , and 100% volumetric flow rate increase from the second semi-permeable membrane process, such as PRO, of the second osmosis chamber  25 . 
         [0049]      FIG. 3  is the exemplary mass and energy balance of the detailed osmotic membrane process which is used in the first and second preferred schematic diagram of the water treatment method in accordance with the invention. 
         [0050]    As for the second preferred embodiment,  FIG. 4  is the second preferred schematic diagram of the water method in accordance with the invention,  FIG. 5  is the detailed exemplary flow diagram of the second preferred schematic diagram of the water treatment method in accordance with the invention, and  FIG. 6  is the exemplary mass and energy balance of the detailed osmotic membrane process which is used in the second preferred schematic diagram of the water treatment method in accordance with the invention. 
         [0051]    As shown in  FIG. 4 , the inlet solution  2  with high salinity stored in chamber  1 , for example, pretreated seawater is given to the chamber  3 , where the inlet solution  2  is separated into two solutions  43  and  44 . Solution  43  is given to the pressure manipulation device  49  which includes, for example, high pressure pump, and pressurized. 
         [0052]    The first solution  44  is given to the first pressure exchange device  36  and pressurized. Pressurized first solution  45  is then separated to the second solution  68  and the third solution  67 , and the third solution  67  is given to the second pressure exchange device  17  where the third solution  67  is pressurized. Pressurized third solution  46  is further exposed to the first pressure manipulation device  19 , for example, booster pump. 
         [0053]    Meanwhile, the second solution  68  is given to the second pressure manipulation device  48 , for example, high pressure pump. 
         [0054]    The solution  43  is exposed to chamber  49 , and pressurized by pressurizing means for example, high pressure pump. Further pressurized solution  43 , as solution  69 , further pressurized second solution  10 , and further pressurized third solution  47  in the first pressure manipulation device  19  are mixed to be the fourth solution. The fourth solution is then given to the first osmosis chamber  11  which includes the first semi-permeable membrane for desalination, for example, reverse osmosis. 
         [0055]    Low salinity and potable quality stream  12 , for example, permeate or product water, is taken from the first osmosis chamber  11  and is given to the chamber  13  for further use, such as drinking, irrigation, or industrial use. 
         [0056]    The fifth solution  14  which is the fourth solution with high pressure concentrated by being exposed to the first semi-permeable membrane of the first osmosis chamber  11 , is exposed to the second pressure exchange device  17  for pressurizing the third solution  67 . 
         [0057]    The pressure of the fifth solution  14  is lowered after being exposed to the second pressure exchange device  17 . Low pressure fifth solution  50  is than exposed to the third pressure manipulation device  51 , such as booster pump, where the low pressure fifth solution  50  is pressurized to the desired levels. 
         [0058]    The fifth solution pressurized in the third pressure manipulation device  51 , as high salinity and high pressure fifth solution  52 , is given as draw solution to the second osmosis chamber  25  where the high salinity and high pressure fifth solution  52  is exposed to the first surface of the second semi-permeable membrane for osmotically driven process. 
         [0059]    Meanwhile, the chamber  62  stores any one or more than one of primary treated wastewater, secondary treated wastewater, tertiary treated wastewater, brackish water, ground and surface water, and the sixth solution  27  which has lower salinity than the high salinity and high pressure fifth solution  52 , is given to the chamber  28 , where the quality, quantity, pressure and volumetric flow rate of the sixth solution  27  is adjusted to the desired levels for said second semi-permeable membrane. Chamber  28  may include any manipulation device to differentiate pressure and volumetric flow rate with respect to desired quality and quantity of the aqueous solution. 
         [0060]    Manipulated sixth solution  29  is then given to the second osmosis chamber  25  as a feed solution, and exposed to the second surface of the second semi-permeable membrane. The salinity gradient between the high salinity and high pressure fifth solution  52  and the manipulated sixth solution  29  draws water from the manipulated sixth solution  29  to the high salinity and high pressure fifth solution  52 , increasing the volumetric flow rate of the high salinity and high pressure fifth solution  52 . 
         [0061]    Said first and second semi-permeable membrane may be chosen from those of nano osmosis membrane, reverse osmosis membrane, PRO membrane, RO membrane, NF membrane, etc. 
         [0062]    Drawn water from the manipulated sixth solution  29  through the second semi-permeable membrane in the second osmosis chamber  25  has a very low salinity, and when said drawn water is mixed with the high salinity and high pressure fifth solution  52 , the salinity gradient between two solutions releases Gibbs free energy of mixing. Released Gibbs free energy of mixing conserves the moderate pressure level in the high salinity and high pressure fifth solution  52 . 
         [0063]    Diluted fifth solution  53  which has larger volumetric flow rate and relatively same pressure than the high salinity and high pressure fifth solution  52 , is taken from the second osmosis chamber  25 , and is given to the first pressure exchange device  36  for pressurizing the first solution  44 . Depressurized fifth solution  54  is then given to chamber  55  for further treatment or disposing processes. 
         [0064]    Meanwhile, concentrated sixth solution  30 , which lost water by being exposed to the second semi-permeable membrane, is given to the chamber  31  for further treatment or saving. 
         [0065]      FIG. 5  shows a detailed exemplary diagram of the mass balance of the second preferred embodiment including the salinity, volumetric flow rate, and pressure specifications of the streams. Mass balance calculations are based on 100 m 3 /h volumetric flow rate of inlet high salinity aqueous solution, such as pre-treated seawater, 50% recovery efficiency of first semi-permeable membrane process, such as SWRO, of the first osmosis chamber  11 , and 70% volumetric flow rate increase from the second semi-permeable membrane process, such as PRO, of the second osmosis chamber  25 . 
         [0066]      FIG. 6  is the exemplary mass and energy balance of the detailed osmotic membrane process which is used in the second preferred schematic diagram of the water treatment method in accordance with the invention. 
         [0067]    As for the third preferred embodiment,  FIG. 7  is the third preferred schematic diagram of the water method in accordance with the invention, and  FIG. 8  is the detailed exemplary schematic diagram of the third preferred schematic diagram of the water treatment method in accordance with the invention, and  FIG. 9  is the exemplary mass and energy balance of the detailed osmotic membrane process which is used in the third preferred schematic diagram of the water treatment method in accordance with the invention. 
         [0068]    As shown in  FIG. 7 , the inlet solution with high salinity stored in chamber  1 , for example, pretreated seawater is given to the chamber  3  as the first solution  2 . In chamber  3 , the first solution  2  is separated into two solutions  4  and  5 , and then, the solution  5  is given to the chamber  6 , and separated into two solutions  7  and  8 . The stream of the solution  7  is the start-up stream for the desalination process and after the desalination process is started, the stream of the solution  7  is shut-down. The solution  8  is given to the second pressure exchange device  17  as the third solution and is pressurized to predetermined level. Pressurized third solution  18  is exposed to the first pressure manipulation device  19  for example, booster pump. 
         [0069]    The solution  4  is given to the first pressure exchange device  36  and is pressurized. Pressurized solution  4 , as the second solution  37 , is then exposed to the second pressure manipulation device  9 , for example, high pressure pump, and is pressurized. 
         [0070]    Pressurized second solution  10  is mixed with further pressurized third solution  20  to be the fourth solution, and the fourth solution is given to the first osmosis chamber  11 , which includes the semi-permeable membrane for desalination, for example, reverse osmosis. 
         [0071]    Low salinity and potable quality stream  12 , for example, permeate or product water, is taken from the first osmosis chamber  11  and is given to the chamber  13  for further use, such as drinking, irrigation, or industrial use. 
         [0072]    The fifth solution  14  which is the fourth solution with high pressure concentrated by being exposed to the first semi-permeable membrane of the first osmosis chamber  11 , is given to the chamber  15  and separated into two solutions  16  and  22 . 
         [0073]    The solution  16  is given to the second pressure exchange device  17  for pressurizing the third solution  8 . 
         [0074]    Depressurized solution  16  which is depressurized after being exposed to the second pressure exchange device  17 , is given as solution  21  to the third pressure manipulation device  23  where the solution  16  is mixed with solution  22  and pressurized. Mixed and pressurized solution, as the fifth solution  24 , is then given to the second osmosis chamber  25 . The fifth solution  24  as high salinity and high pressure draw solution, is given to the second osmosis chamber  25  where the fifth solution  24  is exposed to the first surface of the second semi-permeable membrane for osmotically driven process. 
         [0075]    Meanwhile, the chamber  26  stores any one or more than one of primary treated wastewater, secondary treated wastewater, tertiary treated wastewater, brackish water, ground and surface water, and the sixth solution  27  which has lower salinity than the fifth solution  24 , is given to the chamber  28 , where the quality, quantity, pressure and volumetric flow rate of the sixth solution  27  is adjusted to the desired levels for said second semi-permeable membrane. Chamber  28  may include any manipulation device to differentiate pressure and volumetric flow rate with respect to desired quality and quantity of the aqueous solution. 
         [0076]    Manipulated sixth solution  29  is then given to the second osmosis chamber  25  as a feed solution, and exposed to the second surface of the second semi-permeable membrane. The salinity gradient between the fifth solution  24  and the manipulated sixth solution  29  draws water from the manipulated sixth solution  29  to the fifth solution  24 , increasing the volumetric flow rate of the fifth solution  24 . 
         [0077]    Said first and second semi-permeable membrane may be chosen from those of nano osmosis membrane, reverse osmosis membrane, PRO membrane, RO membrane, NF membrane, etc. 
         [0078]    Drawn water from the manipulated sixth solution  29  through the second semi-permeable membrane in the second osmosis chamber  25  has a very low salinity, and when said drawn water is mixed with the fifth solution  24 , the salinity gradient between two solutions releases Gibbs free energy of mixing. Released Gibbs free energy of mixing conserves the moderate pressure level in the fifth solution  24 . 
         [0079]    Diluted fifth solution  32  which has larger volumetric flow rate and relatively same pressure than the fifth solution  24 , is taken from the second osmosis chamber  25 , and is given to the chamber  33  where the diluted fifth solution  32  is separated into two solutions  34  and  35 . 
         [0080]    Solution  35  is given to the first pressure exchange device  36  for pressurizing the solution  4 . Depressurized solution  35  is then given to chamber  39  for further treatment or disposing processes. 
         [0081]    Meanwhile, concentrated sixth solution  65 , which lost water by being exposed to the second semi-permeable membrane, is given to the chamber  66  for further treatment or saving. 
         [0082]      FIG. 2  shows a detailed exemplary diagram of the mass balance of the first preferred embodiment including the salinity, volumetric flow rate, and pressure specifications of the solutions. Mass balance calculations are based on 100 m3/h volumetric flow rate of inlet high salinity aqueous solution, such as pre-treated seawater, 50% recovery efficiency of first semi-permeable membrane process, such as SWRO, of the first osmosis chamber  11 , and 100% volumetric flow rate increase from the second semi-permeable membrane process, such as PRO, of the second osmosis chamber  25 . 
         [0083]    Solution  34  is given to the energy producing device  40 , such as Pelton turbine, where the potential and kinetic energy of the solution  34  is converted to energy. Depressurized solution  34 , as solution  41 , is then given to the chamber  42  for further treatment or disposing processes. 
         [0084]    Meanwhile, concentrated sixth solution  30 , which lost water by being exposed to the second semi-permeable membrane, is given to the chamber  31  for further treatment or saving. 
         [0085]      FIG. 8  shows a detailed exemplary diagram of the mass balance of the first preferred embodiment including the salinity, volumetric flow rate, and pressure specifications of the solutions. Mass balance calculations are based on 100 m 3 /h volumetric flow rate of inlet high salinity aqueous solution, such as pre-treated seawater, 50% recovery efficiency of first semi-permeable membrane process, such as SWRO, of the first osmosis chamber  11 , and 100% volumetric flow rate increase from the second semi-permeable membrane process, such as PRO, of the second osmosis chamber  25 . 
         [0086]      FIG. 9  is the exemplary mass and energy balance of the detailed osmotic membrane process which is used in the third preferred schematic diagram of the water treatment method in accordance with the invention. 
         [0087]    Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein, to details of the illustrated embodiments are not intend to limit the scope of the claims, which themselves recite those features. It should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true meaning and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process step or steps, to the objective, meaning and scope of the present invention. All such modifications are intended to e within the scope of the claims appended hereto.