Reverse osmosis systems and methods

Abstract

A reverse osmosis system includes a pressure vessel comprising first and second ports. Membrane modules, disposed in the pressure vessel, permeate water through membranes disposed in the modules and block permeation of dissolved solids from concentrate flowing between the first and second ports. A high pressure pump includes an inlet and an outlet. A circulation pump is configured to circulate the concentrate between the first and second ports. The circulation pump includes an inlet and an outlet. A valved circulation apparatus is configured to select between a forward flow mode and a discharge mode of the system. In the forward flow mode, the circulation pump inlet is connected to the second port and the circulation pump outlet is connected to the first port. In the discharge mode, the circulation pump inlet is connected to the high pressure pump inlet and the circulation pump outlet is connected to the first port.

Description

REVERSE OSMOSIS SYSTEMS AND METHODSTECHNICAL FIELD

[0001] The present disclosure relates to reverse osmosis systems and methods. More specifically, the disclosure relates to reverse osmosis systems having at least a forward flow mode and a discharge mode of operation.BACKGROUND

[0002] Reverse osmosis is a process, often used to purify water, that uses one or more semi- permeable membranes to separate permeate molecules, such as water molecules, from other dissolved solids, such as salts. Reverse osmosis applies pressure to overcome osmotic pressure that favors even distribution of salts in solution. Below the osmotic pressure, no permeate will flow through the membranes.

[0003] Referring to prior art FIG. 1, a conventional reverse osmosis (“RO”) system 10 typically has two stages 12, 14 with about half as many pressure vessels (or membrane housings) 16 in the second stage 14 compared to the first stage 12. Each pressure vessel 16 may contain about six membrane modules 13. Each membrane module 13 contains one or more semi-permeable membranes 15. Within each pressure vessel 16, feedwater 18 flows from membrane module to membrane module with the dissolved solids in the feedwater 18 becoming gradually more concentrated as about 15% of the water entering each membrane module 13 may be forced through the thin film membrane 15 as permeate 20. The feedwater 18 with concentrated dissolved solids, which exits the pressure vessels 16, is often referred to as “concentrate” or “brine” 24.

[0004] The high pressure pump 22 supplies high pressure feedwater 18 to the pressure vessels 16 to force pure water as permeate 20 through the membranes 15, leaving dissolved solids on the concentrate side of the membranes 15. Permeate 20 is collected from each pressure vessel 16 and concentrate 24 is bled out through a flow regulator valve 26 to limit the buildup of salts (dissolved solids) to a level close to but lower than the saturation level. When the concentration of salts in the concentrate exceeds the saturation level, the salts start to precipitateout, which may clog the membranes. Therefore care must be taken to not exceed the saturation concentration level of the salts. Problematically however, each of the various salts in the concentrate will have a distinct saturation level, so the critical salt must be identified and carefully controlled. For at least this reason, conventional reverse osmosis systems are operated at constant output and temporarily shut down when the product storage tank for receiving the produced permeate is full. The fraction of the feedwater that is produced as permeate is referred to as the recovery of the system. Given the cost of pretreatment of the feedwater, and disposal of the concentrate, the level of recovery is critically important.

[0005] Problematically also, the reverse osmosis system 10 must continuously feed high pressure water with dissolved salts to the membrane modules in the vessels 16, which is separated into a permeate 20 stream and a concentrate stream 24. This requires automatic control of the flow of concentrate 24 to drain if the system is to maintain efficiency under changing characteristics of the feedwater.

[0006] Also problematically, under constant output conditions, biological growth builds up on the membranes 15 of the membrane modules 13 and dissolved solids may become saturated and build up on the concentrate side of the membranes 15 of the membrane modules 13 within the pressure vessels 16. This requires the system to be periodically shut down for extended periods of time in order to chemically clean-in-place the membrane modules 13.

[0007] Also problematically, in conventional RO systems such as system 10, the maximum salt concentration will be present in the last membrane module 13 in the pressure vessels 16 of the last stage 14. Because the system 10 operates in a steady state, the saturation concentration of the least soluble salt must not be exceeded to avoid precipitation and clogging of the membranes 15 of that last membrane module 13.

[0008] As mentioned earlier, osmotic pressure is the minimum pressure required for water to permeate through a reverse osmosis membrane, and it increases with increasing salinity.Permeate 20 flow (flux) increases in proportion to how much the pressure in the concentrate exceeds the osmotic pressure. Problematically however, in conventional RO system 10, thesalinity doubles in the first stage 12 and then double again in the second stage 14, so the flux is substantially higher in the first membrane module 13 in the pressure vessels 16 of the first stage 12 than in the last membrane module 13 in the pressure vessels 16 of the last stage 14. The membrane modules 13 have an upper limit to the flux, so the membrane modules 13 after the first membrane module 13 are progressively less able to use their full flux capacity.

[0009] Referring to prior art FIG. 2, a closed circuit reverse osmosis (“CCRO”) system 30 is depicted as an alternative to the conventional reverse osmosis system 10 of FIG. 1. The CCRO system 30 adds a circulation pump 32 to recirculate the concentrate 24 to the inlet 34 of the pressure vessel 16. The high pressure pump 22 maintains the pressure in the system 30 and makes up for the water 20 that permeates out of the system 30. Periodically (for example, about every 10 minutes for about 1 minute) the exit valve 36 is opened and the concentrate 24 is purged from the system 30 by the high pressure pump 22 injecting fresh feedwater to displace the concentrate. The main advantages of CCRO system 30 over the conventional RO system 20 is higher recovery (less concentrate to waste) and avoidance of much of the biological growth in the membrane modules due to the variations in dissolved salts. Another advantage of the CCRO system 30 is that the recirculation allows high recovery in a single stage.

[0010] Problematically however, the CCRO system 30 takes a substantial amount of time to discharge the concentrate 24 from the system using the high pressure pump 22. This is because the high pressure pump 22 is designed for high pressure and moderate flow, whereas concentrate discharge is more efficient under low pressure and high flow conditions.

[0011] To mitigate this problem, CCRO systems keep the system 30 at high pressure with the high pressure pump 22, continuously producing permeate 20, even while the concentrate 24 is discharging. Discharging at high pressure (for example up to 40 bar) involves a substantial amount of energy loss, is inefficient and, therefore, is more expensive than discharging at lower pressures (for example, under 2 bar).

[0012] Moreover, because permeate is produced even while the system is purging the concentrate, the water leaving the pressure vessel at the end of the purge cycle is partiallyconcentrated and the membrane modules closest to the concentrate outlet never receive the full benefit of exposure to fresh feedwater, which could otherwise redissolve crystal seeds on the membrane surface.

[0013] Also problematically, because the high pressure pump 22 is designed for high pressure and moderate flow, the high pressure pump 22 usually cannot achieve the maximum inflow permitted by the membrane modules 13 during discharge of the concentrate 24, which also increases the time required to purge the system 30.

[0014] Accordingly, there is a need for a reverse osmosis system that can discharge at lower pressures and higher flows, and in less time than conventional RO or CCRO systems. Also, there is a need for a more energy efficient reverse osmosis system. Additionally, there is a need for a reverse osmosis system that can more effectively avoid membrane fouling by biological growth and salt precipitation without overly complex flow switching.BRIEF DESCRIPTION OF THE INVENTION

[0015] The present disclosure offers advantages and alternatives over the prior art by providing a reverse osmosis system having at least a forward flow mode and a discharge mode. In the forward flow mode, feedwater and recirculated concentrate flows in a forward flow direction from a first port to a second port of a pressure vessel of the system. In the forward flow mode, a circulation pump of the system is connected across the pressure vessel to circulate the concentrate from the second port back to the first port.

[0016] In the discharge mode, the circulation pump inlet is connected, via a valved circulation apparatus, to the high pressure pump inlet instead of the second port of the pressure vessel and the circulation pump outlet is connected to the first port, in order to discharge the concentrate out of the second port of the pressure vessel. Because the circulation pump is designed to operate at higher flow and lower pressure than the high pressure pump of the system, discharge of the concentrate can be achieved more energy efficiently and more rapidly than conventional RO and CCRO systems.

[0017] In some embodiments, the reverse osmosis system of the present disclosure may also include a reverse flow mode. In the reverse flow mode, concentrate flows in a reverse flow direction from the second port to the first port of the pressure vessel. The first and second ports alternate in function between serving as inlet to the pressure vessel and concentrate outlet from the pressure vessel. The forward flow mode and the reverse flow mode together constitute the permeate production mode. The combination of the forward flow mode, discharge mode and reverse flow mode substantially reduces biological growth and precipitated salt build up, as well as increasing the recovery relative to conventional RO and CCRO systems.

[0018] A reverse osmosis system in accordance with one or more aspects of the present disclosure includes a pressure vessel. The pressure vessel includes a first port, a second port and a permeate outlet. One or more membrane modules are disposed in the pressure vessel. Each membrane module has one or more membranes disposed therein. The membrane modules are configured to permeate water, via reverse osmosis, as a permeate from a concentrate flowing between the first and second ports. The membrane modules are also configured to block permeation of dissolved solids from concentrate. The pressure vessel is configured to flow the permeate out the permeate outlet. A high pressure pump is configured to pressurize feedwater to be added to the concentrate. The high pressure pump includes a high pressure pump inlet through which the feedwater is supplied and a high pressure pump outlet. A circulation pump is configured to circulate the concentrate between the first and second ports. The circulation pump includes a circulation pump inlet and a circulation pump outlet. A valved circulation apparatus is configured to select between a forward flow mode of the system and a discharge mode of the system. In the forward flow mode, the circulation pump inlet is connected to the second port and the circulation pump outlet is connected to the first port. In the discharge mode, the circulation pump inlet is connected to the high pressure pump inlet and the circulation pump outlet is connected to the first port.

[0019] Another reverse osmosis system in accordance with one or more aspects of the present disclosure includes a pressure vessel. The pressure vessel includes a first port, a second port and a permeate outlet. One or more membrane modules are disposed in the pressure vessel. Each membrane module has one or more membranes disposed therein. The membranes are configuredto permeate water, via reverse osmosis, as a permeate from a concentrate flowing between the first and second ports. The membranes are also configured to block permeation of dissolved solids from the concentrate. The pressure vessel is configured to flow the permeate out the permeate outlet. A high pressure pump is configured to pressurize feedwater to be added to the concentrate. The high pressure pump includes a high pressure pump inlet through which the feedwater is supplied and a high pressure pump outlet. A circulation pump is configured to circulate the concentrate between the first and second ports. The circulation pump includes a circulation pump inlet and a circulation pump outlet. A valved circulation apparatus is configured to select between a forward flow mode of the system and a discharge mode of the system and a reverse flow mode of the system. In the forward flow mode, the circulation pump inlet is connected to the second port and the circulation pump outlet is connected to the first port. In the discharge mode, the circulation pump inlet is connected to the high pressure pump inlet and the circulation pump outlet is connected to the first port. In the reverse flow mode, the circulation pump inlet is connected to the first port and the circulation pump outlet is connected to the second port.

[0020] A method of reverse osmosis in accordance with one or more aspects of the present disclosure includes selecting a forward flow mode of a reverse osmosis system, via a valved circulation apparatus of the system, wherein a circulation pump outlet of a circulation pump of the system is connected to a first port of a pressure vessel of the system and a circulation pump inlet of the circulation pump is connected to a second port of the pressure vessel. Concentrate is pressurized, via a high pressure pump of the system, to flow through the pressure vessel in a forward flow direction from the first port to the second port. Water is permeated from the concentrate, via reverse osmosis, through one or more membranes of one or more membrane modules disposed in the pressure vessel, as the concentrate flows in the forward flow direction. Permeation of dissolved solids from the concentrate through the membranes is blocked, as the concentrate flows in the forward flow direction. The concentrate is circulated, via the circulation pump, back from the second port to the first port. A discharge mode of the system is selected, via the valved circulation apparatus, wherein the circulation pump inlet is connected to a high pressure pump inlet of the high pressure pump and the circulation pump outlet is connected tothe first port. The concentrate flowing from the second port is discharged out of the system, via the circulation pump, when the system is in the discharge mode.

[0021] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein and may be used to achieve the benefits and advantages described herein.DRAWINGS

[0022] The disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0023] FIG. 1 depicts an example of a schematic of a prior art conventional reverse osmosis system;

[0024] FIG. 2 depicts an example of a schematic of a prior art closed circuit reverse osmosis system;

[0025] FIG. 3A depicts an example of a schematic of a reverse osmosis system in a forward flow mode,

[0026] according to aspects described herein;

[0027] FIG. 3B depicts an example of a schematic of the reverse osmosis system of FIG. 3A in a discharge mode, according to aspects described herein;

[0028] FIG. 3C depicts an example of a schematic of the reverse osmosis system of FIG. 3A with an energy recovery device included, during the discharge mode, according to aspects described herein;

[0029] FIG. 4A depicts an example of a cross-sectional view of a membrane module, according to aspects described herein;

[0030] FIG. 4B depicts an example of an enlarged view of the membrane module within circle 4A-4A of FIG. 4A, according to aspects described herein;

[0031] FIG. 5A depicts another example of a schematic of a reverse osmosis system in a forward flow mode, according to aspects described herein;

[0032] FIG. 5B depicts an example of a schematic of the reverse osmosis system of FIG. 5A in a discharge mode, according to aspects described herein;

[0033] FIG. 5C depicts an example of a schematic of the reverse osmosis system of FIG. 5A in a reverse flow mode, according to aspects described herein;

[0034] FIG. 5D depicts an example of a schematic of the reverse osmosis system of FIG. 5A with an energy recovery device included, during the discharge mode, according to aspects described herein;

[0035] FIG. 6A depicts an example of a flow diagram of a method of reverse osmosis, according to aspects described herein; and

[0036] FIG. 6B depicts an example of a flow diagram of a continuation of the method of reverse osmosis of FIG. 6A, according to aspects described herein.DETAILED DESCRIPTION

[0037] Certain examples will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the methods, systems, and devices disclosed herein. One or more examples are illustrated in the accompanying drawings. Those skilled in the art will understand that the methods, systems, and devices specifically described herein and illustrated in the accompanying drawings are non-limiting examples and that the scope of the present disclosure is defined solely by the claims. The features illustrated or described in connection with one example may be combined with the features of other examples.Such modifications and variations are intended to be included within the scope of the present disclosure.

[0038] The terms "significantly", "substantially", "approximately", "about", “relatively,” or other such similar terms that may be used throughout this disclosure, including the claims, are used to describe and account for small fluctuations, such as due to variations in processing from a reference or parameter. Such small fluctuations include a zero fluctuation from the reference or parameter as well. For example, they can refer to less than or equal to ± 10%, such as less than or equal to ± 5%, such as less than or equal to ± 2%, such as less than or equal to ± 1%, such as less than or equal to ± 0.5%, such as less than or equal to ± 0.2%, such as less than or equal to ± 0.1%, such as less than or equal to ± 0.05%.

[0039] Referring to FIGS. 3 A and 3B, an example is depicted of a schematic of a reverse osmosis system 100 in a forward flow mode (FIG. 3A) and a discharge mode (FIG. 3B), according to aspects described herein. The system 100 is a novel type of closed circuit reverse osmosis (CCRO) system. The reverse osmosis system 100 includes a pressure vessel 102. The pressure vessel 102 includes a first port 106, a second port 108 and a permeate outlet 110. One or more membrane modules 104 are disposed in the pressure vessel. Each membrane module 104 has one or more membranes 105 disposed therein. The one or more membranes 105 are configured to permeate water 114, via reverse osmosis, as a permeate 114 from a concentrate 115 flowing through the first and second ports 106, 108. The membranes 105 are also configured to block permeation of dissolved solids (not shown) from the concentrate 115. The pressure vessel 102 is configured to flow the water 114 as a permeate 114 out the permeate outlet 110.

[0040] The system 100 also includes a high pressure pump 116 and a circulation pump 122. The high pressure pump 116 is configured to pressurize feedwater 112 to be added to the concentrate 115. The high pressure pump 116 includes a high pressure pump inlet 118 through which the feedwater 112 is supplied and a high pressure pump outlet 120. The circulation pump 122 is configured to circulate the concentrate 115 between the first and second ports 106, 108. The circulation pump includes a circulation pump inlet 124 and a circulation pump outlet 126.

[0041] A valved circulation apparatus 128 is configured to select between a forward flow mode of the system 100 and a discharge mode of the system 100. In the forward flow mode, the circulation pump inlet 124 is connected to the second port 108 and the circulation pump outlet 126 is connected to the first port 106. In the discharge mode, the circulation pump inlet 124 is connected to the high pressure pump inlet 118 and the circulation pump outlet 126 is connected to the first port 106.

[0042] As used herein, the term “feedwater” 112 is the flow of solution of water (as the solvent of the solution) and dissolved solids (as the solute of the solution) that enters the reverse osmosis system 100, but has not yet been subjected to the process of reverse osmosis, i.e., has not yet entered the pressure vessel 102 where reverse osmosis occurs. By way of example, the feedwater 112 may be brackish water or sea water.

[0043] Also as used herein, the term “concentrate” 115 is the flow of a solution of water that has become more concentrated with dissolved solids than the fresh feedwater 112 that first enters the system 100. This is because the concentrate 115 has been subjected to the process of reverse osmosis, wherein pure water 114 as a permeate 114 is removed from the fresh feedwater 112. Therefore, the concentration of dissolved solids in the concentrate increases over the time the concentrate is subjected to the reverse osmosis process. Accordingly, the term concentrate is used herein to describe the flow of the solution of water passing through the pressure vessel 102 and circulating throughout the system 100.

[0044] Also as used herein, the term “connected” between two components of the system 100 means that the components are in fluid communication with each other. Therefore, a fluid flow path is established between the components and any valve (for example) in that flow path would be open to allow flow of the fluid (e.g., permeate, concentrate or feedwater) of the system therethrough. So, for example, when the inlet 124 of the circulation pump 122 is said to be connected to the second port 108 of the pressure vessel 102, then the valve 130 is open to allow concentrate flow through the lines connecting the circulation pump inlet 124 to the second port 108.

[0045] The membranes 105 (see FIG. 4A) in the membrane modules 104 may be semi- permeable membranes that are designed to act as a barrier to salts and other dissolved solids, but allow water molecules to pass or permeate through the membrane 105 as permeate 114. During reverse osmosis, the water molecules in feedwater 112, such as brackish water or sea water, will pass through the membrane 105 when subjected to pressure, but the dissolved solids will remain in the concentrate 112. Each membrane 105 may be housed in a membrane module 104 (see FIG. 4A). Each membrane module 104 would be disposed in the pressure vessel 102. Each membrane module 104 is configured to provide the mechanism that separates the concentrate into a permeate 114 stream and a concentrate 112 stream. The permeate 114 stream flows out of the permeate outlet 110 of the pressure vessel 102 and the concentrate stream 113 (sometimes called a “concentrated feedwater stream”) flows out of the second port 108 of the pressure vessel 102.

[0046] The high pressure pump 116 is configured to pressurize the feedwater 112 and, therefore, the concentrate 115. For example, operating pressure is typically in a range of 10-20 bar for brackish water and typically in a range of 45-70 bar for seawater. The high pressure pump 116 includes the high pressure pump inlet 118 through which the feedwater 112 is supplied and the high pressure pump outlet 120. The outlet 120 of the high pressure pump 116 may be connected to the first port 106, as exemplified in FIGS. 3A and 3B. However, as exemplified in FIGS. 5A and 5C, the connection of the outlet 120 of the high pressure pump 116 may be switchable, via the valved circulation apparatus 128, between the first port 106 and the second port 108. The high pressure pump 116 may have a variable frequency drive to adjust flow and pressure.

[0047] The circulation pump 122 is configured to circulate the concentrate 115 between the first and second ports 106, 108. The circulation pump 122 only needs to overcome the pressure drop through a feed spacer mesh 152, which is disposed adjacent to the membranes 105 (see FIG. 4A) and on the concentrate side of the membranes 105. The example, the operating pressure of the circulation pump 122 may only be in a range of 0.5 to 1.5 bar. The circulation pump 122 would have a relatively high flow compared to the high pressure pump 116 (for example twice the flow) in order to create eddies (e.g., turbulent flow) in the mesh 152 and thereby reduce concentration gradient between the bulk flow and the surface of the membrane 105, and the tendency for biological growth on the membranes 105. The eddies also enhance the rate of permeate flowthrough the membranes 105. The circulation pump 122 includes the circulation pump inlet 124 and the circulation pump outlet 126. The circulation pump 122 may have a variable frequency drive to adjust flow and pressure.

[0048] The valved circulation apparatus 128 is configured to select between a forward flow mode (FIG. 3A) of the system 100 and a discharge mode (FIG. 3B) of the system 100. In the forward flow mode (FIG. 3A), the circulation pump inlet 124 is connected to the second port 108 and the circulation pump outlet 126 is connected to the first port 106. In the discharge mode (FIG. 3B), the circulation pump inlet 124 is connected to the high pressure pump inlet 118 and the circulation pump outlet 126 is connected to the first port 106.

[0049] In the forward flow mode (FIG. 3 A), the concentrate 115 flows through the pressure vessel 102 in a forward flow direction from the first port 106 to the second port 108 and the concentrate 115 circulates back to the first port 106 via the circulation pump 122. During the forward flow mode (FIG. 3 A), the system 100 produces permeate 114 through the permeate outlet 110. Additionally, in the forward flow mode, the high pressure pump 116 output pressure may be greater than or equal to the circulation pump 122 output pressure and the high pressure pump 116 output flow rate may be less than the circulation pump 122 output flow rate. For example, the operating pressure of the high pressure pump 116 may be in a range of 10-20 bar for brackish feedwater and 45-70 bar for seawater or 100 bar for high recovery seawater RO, whereas the circulation pump boost pressure may be only within a range of 0.5- 1.5 bar. Additionally, the output capacity of the circulation pump 122 may be two times the capacity of the high pressure pump 116.

[0050] The valved circulation apparatus 128 of the system 100 in FIGS. 3 A and 3B includes the following structure. A first valve 130 is connected via a first tee 136 to the inlet 124 of the circulation pump 122. The first valve 130 is also connected via a second tee 138 to the second port 108 of the pressure vessel 102. A second valve 132 is connected via the first tee 136 to the inlet 124 of the circulation pump 122. The second valve 132 is also connected via a third tee 140 to the inlet 118 of the high pressure pump 116. A third valve 134 is connected via the second tee 138 to the second port 108 of the pressure vessel 102. The circulation pump outlet 126 and thehigh pressure pump outlet 120 are connected via a fourth tee 142 to the first port 106 of the pressure vessel 102. Finally, a feed line 144 for supplying the feedwater 112 is connected to the third tee 140.

[0051] The valves (such as the first, second and third valves 130, 132 and 134) and tees (such as the first, second, third and fourth tees 136, 138, 140 and 142) as used herein, may include stand alone functioning valves and tees or may be internal components to more complicated flow control devices. For example, the first valve 130, second valve 132 and first tee 136 may comprise a single three-way valve that performs the same flow control functions.

[0052] Referring more specifically to FIG. 3A, during the forward flow mode (FIG. 3A), the first valve 130 of the valved circulation apparatus 128 is open and the second and third valves 132, 134 are closed. The forward flow mode is configured to enable the high pressure pump 116 to pressurize the system 100 and to compensate for concentrate 115 lost during permeate production, i.e., to make up for the water as permeate 114 that flows out the permeate outlet 110 and, therefore, reduces the volume of concentrate 115. The forward flow mode is also configured to enable the circulation pump 122 to circulate the concentrate 112 through the pressure vessel 102 in a forward flow direction from the second port 108 to the first port 106. In other words, as indicated by flow arrows 146, the concentrate 115 circulates from the second port 108, to the first valve 130, to the circulation pump 122 and back to the first port 106.

[0053] When the concentration of salts in the concentrate 115 exceeds the saturation level, these salts start to precipitate, which clogs the membranes 105 within the membrane modules 104. The time required to precipitate salts after their concentration has reached the saturation level is known as the induction time, which depends primarily on the degree to which the saturation level is exceeded. Accordingly, to prevent the precipitation of salts from the concentrate 115, the system 100 may switch to the discharge mode after a predetermined saturation level of the system 100 has been reached, and before an additional predetermined induction time of the system 100 has elapsed. Mode switching allows the system to exceed the saturation level within the limits of the induction time, thereby increasing the recovery, which is not possible in conventional RO systems.

[0054] CCRO systems 30, 100 may take advantage of the induction time using non-steady- state operation to obtain higher recovery, with less feedwater consumption and less concentrate to dispose of. Induction time, as mentioned above, is the time it takes for salts in a super saturated solution to start to crystalize and precipitate, generally in the range of a few minutes. For example, the induction time may be 2 minutes, or 3 minutes or 4 minutes.

[0055] CCRO systems 30, 100 may do this by circulating the concentrate while producing permeate, thereby increasing the salinity past the saturation level. The prior art CCRO systems 30 will then discharge the concentrate before the induction time is exceeded using the high pressure pump. Problematically, with prior art system 30, there is relatively slow progression of the feedwater through the pressure vessel, due to the relatively moderate flow rate of the high pressure pump. Because the final membrane module of the pressure vessel will contain super saturated concentrate until the fresh feedwater has travelled the length of the pressure vessel to reach it, the flush time reduces the useable induction time. System 100 advantageously mitigates this issue with the significantly higher flow rate of the circulation pump that is uniquely used during the discharge mode, which significantly reduces the time for the feedwater to reach the last membrane module.

[0056] Referring more specifically to FIG. 3B, during the discharge mode, the first valve 130 is closed and the second and third valves 132, 134 are open to enable discharge of the concentrate 115 through the third valve 134. The discharge mode is configured to enable the feedwater 112 to flow into the pressure vessel 102 from the first port 106 displacing the concentrate 115 out through the second port 108, to be discharged out of the system 100 through the third valve 134. In other words, as indicated by flow arrows 146, the feedwater 112 enters the circulation pump inlet 124 through the open second valve 132, and is pumped primarily by the circulation pump 122, through the fourth tee 142, into the first port 106, wherein the feedwater 112 displaces the concentrate 115, which flows through the second port 108, through the third valve 134 and out of the system 100.

[0057] Also, during the discharge mode, the high pressure pump 116 outlet pressure may be turned down such that the high pressure pump 116 outlet pressure is equal to or less than a predetermined threshold osmotic pressure of the system and also equal to or greater than theoutput pressure of the circulation pump 122. As a result, the circulation pump 122 cannot force back flow through the high pressure pump 116, because the high pressure pump 116 pressure is equal to or greater than the circulation pump 122 pressure. Optionally, a check valve may be placed at the high pressure pump outlet 120. Additionally, the system 100 stops permeate production through the permeate outlet 110, because the system pressure is below the system’s predetermined threshold osmotic pressure.

[0058] Below the osmotic pressure, no permeate 114 (i.e., water 114) will flow through the membranes 105. The threshold osmotic pressure to produce permeate depends on the dissolved solids in the feedwater 112. As an example, for brackish water the threshold osmotic pressure may be about 2 bar and for seawater the threshold osmotic pressure may be about 15 bar.

[0059] Advantageously, the discharge mode is very energy efficient and rapid compared to conventional RO and CCRO systems. Also advantageously, the high pressure pump 116 is available to provide additional flow that can combine with the circulation pump 122 flow for maximum allowable flow into the membrane modules 104 during discharge.

[0060] Also advantageously, the CCRO system 100 uniquely reduces the discharge time by using the circulation pump 122 to execute the discharge as well as the high-pressure pump 116, thereby making better use of the induction time. The high-pressure pump 116 may be used only to make up the water lost to permeate 114 production, which flow may be about 1 / 3 the maximum concentrate flow for the membrane modules 104. It would be inefficient and costly to size the high-pressure pump 116 to provide the maximum concentrate flow. The circulation pump 122 is sized to attain this maximum flow and is only required to provide the pressure lost to friction as the concentrate 115 circulates and is eventually discharged, so the circulation pump 122 can execute the discharge mode more efficiently than prior art CCRO systems.

[0061] Referring to FIG. 3C, an example is depicted of a schematic of the reverse osmosis system 100 of FIG. 3 A with an energy recovery device (ERD) 148 included, during the discharge mode, according to aspects described herein. Energy recovery devices, or pressure exchangers, are well known devices that transfer pressure energy from a high pressure fluidstream to a low pressure fluid stream. An example of at least one such ERD is manufactured under the trademark PX® Pressure Exchanger®, by Energy Recovery, Inc. of San Leandro, CA, USA.

[0062] During the discharge mode of system 100 of FIG. 3C, the valved circulation apparatus 128 is configured such that feedwater 112 from the feedline 144 enters feedwater input port 148A of the ERD 148 as low pressure feedwater 112LP, and concentrate 115 from the pressure vessel 102 enters concentrate input port 148C of the ERD 148 as high pressure concentrate 115HP. Energy from the hydraulic pressure of the high pressure concentrate 115HP is transferred from the high pressure concentrate 115HP to the low pressure feedwater 112LP within the ERD 148. Thereafter, the feedwater 112 exits feedwater output port 148B of the ERD 148 as high pressure feedwater 112HP and flows into the circulation pump inlet 124. Simultaneously, the concentrate 115 exits the concentrate output port 148D of the ERD 148 as low pressure concentrate 115LP, wherein it is discharged from the system 100.

[0063] Advantageously, by transferring the high pressure energy of the high pressure concentrate 115HP, that would otherwise be wasted, to the low pressure feedwater 112LP, the pressure fluctuations that the pressure vessel 102 and membrane modules 104 are exposed to when switching from the forward flow mode FIG. 3A to the discharge mode FIG. 3C are significantly reduced. As such, the material fatigue on the pressure vessel 102 and membrane modules 104 are also advantageously significantly reduced.

[0064] In the discharge mode of system 100 of FIG. 3C, permeate 114 is produced out of the permeate outlet 110 of the pressure vessel 102. This is because the pressure in the pressure vessel 102 is kept above the osmotic pressure of the system 100.

[0065] Referring to FIG. 4A, an example is depicted of a cross-sectional view of a membrane module 104, according to aspects described herein. The membrane module 104 is designed to fit into the pressure vessel 102 and to house the membrane 105. The membrane module 104 is configured to provide the mechanism that separates the concentrate 115 into a permeate (water) 114 stream and a concentrate 115 stream.

[0066] The membrane module 104 includes an outer sheath 154 and a permeate collection tube 156. The permeate collection tube 156 extends along the central axis 150 of the membrane module 150.

[0067] The membrane 105 is disposed against a feed spacer mesh 152 (see FIG. 4B). The membrane 105 and mesh 152 are spirally wound around the collection tube 156, wherein the mesh 152 forms the spiral-shaped channel between the sheets of the spirally wound membrane 105.

[0068] Feedwater 112 is pressurized by the high pressure pump 116. As the feedwater 112 enters the membrane module 104 and is subjected to the process of reverse osmosis, the feedwater becomes concentrate 115. The concentrate 115 flows axially through the spacer mesh 152 within the spirally wound sheets of the membrane 105. Permeate 114 from the concentrate 115 flows radially through the membrane 105 via reverse osmosis and tangentially spirals through the mesh 152 towards the centrally located collection tube 156. As a result, the concentrate 115 becomes progressively more concentrated with dissolved solids as it flows axially from the upstream end 158 of the membrane module 104 to the downstream end 160 of the membrane module 104.

[0069] The permeate 114 in the collection tube 156 forms a permeate 114 stream that is directed out of the permeate outlet 110 of the pressure vessel 102. The concentrate 115 exiting the downstream end 160 of the membrane module 150 enters the upstream end 158 of the next membrane module in line (if there is one). Concentrate 115 from the last membrane module 104 in line forms a concentrate 115 stream that is directed out of the first or second ports 106, 108 of the pressure vessel 102.

[0070] Referring to FIG. 4B, an example is depicted of an enlarged view of the membrane module 104 within circle 4A-4A in FIG. 4A, according to aspects described herein. As discussed earlier herein, the membrane 105 and spacer mesh 152 are spirally wound around the collection tube 156, wherein the spacer mesh 152 forms the spiral-shaped channels between the spirally wound sheets of the membrane 105. In other words, the spacer mesh 152 and membrane 105form alternating spiral-shaped channels and spiral-shaped sheets around the collection tube 156. The feedwater 112 and concentrate 115 flow axially along the spiral-shaped channel of the mesh 152. The permeate (water) 114 from the concentrate 115 flows radially through the membrane 105 via reverse osmosis and tangentially spirals through the spacer mesh 152 towards the centrally located collection tube 156. The permeate (water) 114 enters the collection tube 156 through collection tube orifices 162, where it combines with other permeate 114 to form a permeate stream 114 that flows axially along the collection tube 156.

[0071] Referring to FIGS. 5A, 5B and 5C, another example is depicted of a schematic of a reverse osmosis system 200 in a forward flow mode (FIG. 5A) a discharge mode (FIG. 5B) and a reverse flow mode (FIG. 5C), according to aspects described herein. The reverse osmosis system 200 is similar to the reverse osmosis system 100, wherein the same or similar features will be referenced with the same or similar reference numbers.

[0072] The reverse osmosis system 200 includes the pressure vessel 102. The pressure vessel 102 includes the first port 106, the second port 108 and the permeate outlet 110. One or more membrane modules 104 are disposed in the pressure vessel. Each membrane module 104 has one or more membranes 105 disposed therein. The one or more membranes 105 are configured to permeate water 114, via reverse osmosis, as the permeate 114 from the concentrate 115 flowing between the first and second ports 106, 108. The membranes 105 are also configured to block permeation of dissolved solids (not shown) from the concentrate 115. The pressure vessel 102 is configured to flow the water 114 as a permeate 114 out the permeate outlet 110.

[0073] The high pressure pump 116 is configured to pressurize the feedwater 112 and, therefore, the concentrate 115. The high pressure pump 116 includes the high pressure pump inlet 118 through which the feedwater 112 is supplied and the high pressure pump outlet 120 that is selectively connected to the first port 106 via first valve 202. The circulation pump 122 is configured to circulate the concentrate between the first and second ports 106, 108. The circulation pump 122 includes the circulation pump inlet 124 and the circulation pump outlet 126. Both the high pressure pump 116 and circulation pump 122 may include variable frequency drives to enable adjustment of their respective output pressure and flow.

[0074] A valved circulation apparatus 204 is configured to select between the forward flow mode (FIG. 5A) of the system 200 and the discharge mode (FIG. 5B) of the system 200 and a reverse flow mode (FIG. 5C) of the system 200. In the forward flow mode, the high pressure pump outlet 120 is connected to the first port 106, the circulation pump inlet 124 is connected to the second port 108 and the circulation pump outlet 126 is connected to the first port 106. In the discharge mode, the high pressure pump outlet 120 is connected to the first port 106, the circulation pump inlet 124 is connected to the high pressure pump inlet 118 and the circulation pump outlet 126 is connected to the first port 106. In the reverse flow mode, the high pressure pump outlet 120 is connected to the second port 108, the circulation pump inlet 124 is connected to the first port 106 and the circulation pump outlet 126 is connected to the second port 108.

[0075] In the forward flow mode (FIG. 5 A), the concentrate 115 flows through the pressure vessel 102 in a forward flow direction from the first port 106 to the second port 108 and circulates back to the first port 106 via the circulation pump 122. In the forward flow mode, the system 200 produces permeate (i.e., water) 114 through the permeate outlet 110. In the discharge mode (FIG. 5B), the feedwater 112 flows into the pressure vessel 102 from the first port 106, displacing the concentrate 115 through the second port 108 and the concentrate 115 is discharged out of the system 200. In the discharge mode, the system 200 stops permeate production through the permeate outlet 110. In the reverse flow mode (FIG. 5C), the concentrate 115 flows through the pressure vessel 102 in a reverse flow direction from the second port 108 to the first port 106 and circulates back to the second port 108 via the circulation pump 122. In the reverse flow mode, the system 200 produces permeate (i.e., water) 114 through the permeate outlet 110.

[0076] In both the forward flow mode (FIG. 5A) and the reverse flow mode (FIG. 5C) of system 200, the high pressure pump 116 output pressure may be greater than the circulation pump 122 output pressure. Additionally, the circulation pump 122 output flow rate may be preferably greater than the high pressure pump 116 output flow rate.

[0077] During the discharge mode (FIG. 5B), the high pressure pump 116 outlet pressure may be turned down such that the high pressure pump 116 outlet pressure is equal to or less than apredetermined threshold osmotic pressure of the system 200 and also equal to or greater than the output pressure of the circulation pump 122. As a result, the circulation pump 122 cannot force back flow through the high pressure pump 116, because the high pressure pump 116 pressure is greater than the circulation pump 122 pressure. Optionally, a check valve may be placed at the high pressure pump outlet. Additionally, the system 200 stops permeate production through the permeate outlet 110, because the system pressure is below the system’s predetermined threshold osmotic pressure.

[0078] The valved circulation apparatus 204 of the system 200 in FIGS. 5 A, 5B and 5C includes the following structure. The first valve 202 is connected via first tee 206 to the first port 106 and also connected to the high pressure pump outlet 120 via a second tee 208 in series connection with a third tee 210. A second valve 212 is connected via the first tee 206 to the first port 106 and also connected to the circulation pump inlet 124 via a fourth tee 214 in series connection with a fifth tee 216. A third valve 218 is connected to the fourth tee 214 and also connected to the second port 108 via a sixth tee 220 in series connection with a seventh tee 222. A fourth valve 224 is connected to the second port 108 via the seventh tee 222. A fifth valve 226 is connected to the second tee 208 and sixth tee 220. The circulation pump outlet 126 is connected to the third tee 210. A sixth valve 228 is connected to the circulation pump inlet 124 via the fifth tee 216 and also connected to the high pressure pump inlet 118 via an eighth tee 230. A feed line 232 for supplying the feedwater 112 is connected to the eighth tee 230.

[0079] Referring more specifically to FIG. 5A, during the forward flow mode, the first valve 202 and third valve 218 are open and the second valve 212, fourth valve 224, fifth valve 226 and sixth valve 228 are closed. Configuring the valves in this way, enables the high pressure pump 116 to pressurize the system 200 and to replenish concentrate 115 lost during permeate 114 production (i.e., to replenish the water 114 lost through the permeate outlet 110). Additionally, this valve configuration enables the circulation pump 122 to circulate the concentrate 115 through the pressure vessel 102 in a forward flow direction from the first port 106 to the second port 108. In other words, as indicated by flow arrows 146, the concentrate 115 circulates from the first port 106, to the second port 108, to the seventh tee 222, to the sixth tee 220, to the third valve 218, to the forth tee 214, to the fifth tee 216, through the circulation pump 122, to the thirdtee 210 to the second tee 208 to the first valve 202, to the first tee 206 and back to the first port 106.

[0080] When the concentration of salts in the concentrate 115 exceeds the saturation level, these salts start to precipitate which clogs the membranes 105. The time required to precipitate salts after their concentration has reached the saturation level is known as the induction time, which depends primarily on the degree to which the saturation level is exceeded. Accordingly, to prevent the precipitation of salts from the concentrate 115, the system 200 may switch to the discharge mode after a predetermined saturation level of the system 200 has been reached, and before an additional predetermined induction time of the system 200 has elapsed.

[0081] Referring more specifically to FIG. 5B, during the discharge mode, the first 202, fourth 224 and sixth 228 valves are open and the second 212, third 218 and fifth 226 valves are closed to enable discharge of the concentrate 115 through the fourth valve 224. In other words, as indicated by flow arrows 146, the feedwater 112 flows from the feed line 232, to the eighth tee 230, to the sixth valve 228, to the fifth tee 216, through the circulation pump 122, to the third tee 210, to the second tee 208, to the first valve 202, and to the first tee 206, wherein the feedwater 112 enters the first port 106 of the pressure vessel 102. Accordingly, the feedwater 112 displaces the concentrate 115 in the pressure vessel 102, which flows through the pressure vessel 102, to the seventh tee 222, through the fourth valve 224 and out of the system 200.

[0082] Also, during the discharge mode, the feedwater 112 flows through the high pressure pump via feed line 232 and eighth tee 230. During the discharge mode, the high pressure pump 116 outlet pressure may be turned down such that the high pressure pump 116 outlet pressure is equal to or less than a predetermined threshold osmotic pressure of the system and also equal to or greater than the output pressure of the circulation pump 122. As a result, the circulation pump 122 cannot force back flow through the high pressure pump 116, because the high pressure pump 116 pressure is greater than the circulation pump 122 pressure. Optionally, a check valve may be placed at the high pressure pump outlet. Additionally, the system 200 stops permeate production through the permeate outlet 110, because the system pressure is below the system’s predetermined threshold osmotic pressure. Advantageously, both the high pressure pump 116and the circulation pump 122 may contribute to feeding fresh feedwater into the pressure vessel 102, at the maximum flow rate allowed by the membrane modules 104, to displace concentrate 115 out through the fourth valve 224 in the shortest time possible.

[0083] Referring more specifically to FIG. 5C, during the reverse flow mode, the second valve 212 and fifth valve 226 are open and the first 202, third 218, fourth 224 and sixth 228 valves are closed. Configuring the valves in this way, enables the high pressure pump 116 to pressurize the system 200 and to replenish concentrate 115 lost during permeate 114 production (i.e., to replenish the water 114 lost through the permeate outlet 110). To accomplish this, feedwater 112 enters the system 200 through the feed line 232, the eighth tee 230, the high pressure pump 116 and the third tee 210, where it is mixed with recirculated concentrate 115. The mixture proceeds to the second tee 208, through the fifth valve 226 and the sixth tee 220, to the seventh tee 222, to the second port 108 and through the pressure vessel 102 in a reverse flow direction to port 106. Additionally, this valve configuration enables the circulation pump 122 to recirculate the concentrate 115 from the first port 106 to the second port 108. In other words, as indicated by flow arrows 146, the concentrate 115 circulates from the first port 106, to the first tee 206, through the second valve 212, to the forth tee 214, to the fifth tee 216, through the circulation pump to the third tee 210, where it mixes with the feedwater 112.

[0084] It should be noted that the valves and tees as used herein, may include stand alone functioning valves and tees or may be internal components to more complicated flow control devices. For example, in the system 200, the first 202 valve, fifth 226 valve and second tee 208 may comprise a single three-way valve.

[0085] Advantageously in system 200, the use of the reverse mode has the added advantage of a scrubbing effect, introduced by the back-and-forth flow. The feed spacer mesh 152, which is oriented diagonally to reduce dead zones, has regions of high and low flow caused by the unidirectional flow in the forward flow mode (FIG. 5A). When the flow is reversed (FIG. 5C), the regions of high and low flow are inverted, so that crystallization of salts and growth of microbes are impeded. Also, the concentrate side of the membranes 105 is mildly scrubbed by the bidirectional flow.

[0086] Also advantageously, the last membrane module which has been subjected to the highest salinity during forward flow becomes the first when the flow is reversed and is now exposed to the lowest salinity of the feedwater, increasing the cleaning effect and the inhibition of microbial growth.

[0087] Referring to FIG. 5D, an example is depicted of a schematic of the reverse osmosis system 200 of FIG. 5 A with an energy recovery device (ERD) 148 included, during the discharge mode, according to aspects described herein. During the discharge mode of system 200 of FIG. 5D, the valved circulation apparatus 128 is configured such that feedwater 112 from the feedline 232 enters feedwater input port 148A of the ERD 148 as low pressure feedwater 112LP, and concentrate 115 from the pressure vessel 102 enters concentrate input port 148C of the ERD 148 as high pressure concentrate 115HP. Energy from the hydraulic pressure of the high pressure concentrate 115HP is transferred from the high pressure concentrate 115HP to the low pressure feedwater 112LP within the ERD 148. Thereafter, the feedwater 112 exits feedwater output port 148B of the ERD 148 as high pressure feedwater 112HP and flows into the circulation pump inlet 124. Simultaneously, the concentrate 115 exits the concentrate output port 148D of the ERD 148 as low pressure concentrate 115LP, wherein it is discharged from the system 200.

[0088] Advantageously, by transferring the high pressure energy of the high pressure concentrate 115HP, that would otherwise be wasted, to the low pressure feedwater 112LP, the pressure fluctuations that the pressure vessel 102 and membrane modules 104 are exposed to when switching from the forward flow mode FIG. 5A to the discharge mode FIG. 5D are significantly reduced. As such, the material fatigue on the pressure vessel 102 and membrane modules 104 are also advantageously significantly reduced. Moreover, the same advantages occur when switching from the reverse flow mode FIG. 5C to the discharge mode FIG. 5D.

[0089] In the discharge mode of system 200 of FIG. 5D, permeate 114 is produced out of the permeate outlet 110 of the pressure vessel 102. This is because the pressure in the pressure vessel 102 is kept above the osmotic pressure of the system 200.

[0090] Referring to FIG. 6A, an example is depicted of a flow diagram of a method 300 of reverse osmosis, according to aspects described herein. The method 300 begins at 302 by selecting a forward flow mode (FIG. 3A or 5A) of a reverse osmosis system 100, 200, via a valved circulation apparatus 128, 204 of the system , wherein a circulation pump outlet 126 of a circulation pump 122 of the system 100, 200 is connected to a first port 106 of a pressure vessel 102 of the system 100, 200 and a circulation pump inlet 124 of the circulation pump 122 is connected to a second port 108 of the pressure vessel 102.

[0091] At 304, concentrate 115 is pressurized, via a high pressure pump 116 of the system 100, 200 to flow through the pressure vessel 102 in a forward flow direction from the first port 106 to the second port 108. In the forward flow mode, the high pressure pump 116 output pressure may be greater than the circulation pump 122 output pressure, and the circulation pump 122 output flow rate may be preferably greater than the high pressure pump 116 output flow rate.

[0092] At 306, water 114 is permeated from the concentrate 115 via reverse osmosis through one or more membranes 105 of membrane modules 104 disposed in the pressure vessel 102, as the concentrate 115 flows in the forward flow direction. In the forward flow mode, the water 114 is directed to flow as a permeate 114 out of a permeate outlet 110 of the pressure vessel 102.

[0093] At 308, permeation of dissolved solids from the concentrate 115 is blocked from getting through the one or more membranes 105, as the concentrate 115 flows in the forward flow direction.

[0094] At 310, the concentrate 115 is circulated, via the circulation pump 122, back from the second port 108 to the first port 106.

[0095] At 312, a discharge mode of the system is selected, via the valved circulation apparatus 128, 204, wherein the circulation pump inlet 124 is connected to a high pressure pump inlet 118 of the high pressure pump 116 and the circulation pump outlet 126 is connected to the first port 106. In the discharge mode, the high pressure pump 116 outlet pressure may be equal to or less than a predetermined threshold osmotic pressure of the system, and equal to or greater than theoutput pressure of the circulation pump 122. As a result, the flow of water as a permeate out of the permeate outlet is stopped. Additionally, to prevent the precipitation of salts from the concentrate 115, the system 100, 200 may switch to the discharge mode after a predetermined saturation level of the system 100, 200 has been reached, and before an additional predetermined induction time of the system 100, 200 has elapsed.

[0096] Also during the discharge mode, feedwater 112, from a feedline 144, 232 connected to the high pressure pump inlet 118, may flow, as a low pressure feedwater 112LP, into an energy recovery device (ERD) 148. Further during the discharge mode, the concentrate 115, from the pressure vessel 102, may flow as a high pressure concentrate 115HP into the ERD 148. Within the ERD 148, energy from hydraulic pressure of the high pressure concentrate 115HP may be transferred to the low pressure feedwater 112LP. Thereafter, the feedwater 112 as a high pressure feedwater 112HP may flow out of the ERD 148 and into the circulation pump inlet 124. Simultaneously, the concentrate 115, as a low pressure concentrate 115LP, may flow out of the ERD 148 and may be discharged out of the system 100, 200 as a low pressure concentrate out 115LP.

[0097] At 314, in the discharge mode, the concentrate 115 flowing from the second port 108 is discharged out of the system 100, 200, impelled by the circulation pump 122 injecting fresh feedwater 112.

[0098] Referring to FIG. 6B, an example is depicted of a flow diagram of a continuation of the method 300 of reverse osmosis of FIG. 6A, according to aspects described herein. The method 300 continues at 316 by selecting a reverse flow mode (FIG. 5C), via the valved circulation apparatus 204, wherein the circulation pump inlet 124 is connected to the first port 106 and the circulation pump outlet 126 is connected to the second port 108.

[0099] At 318, concentrate 115 is pressurized, via a high pressure pump 116 of the system 200 to flow through the pressure vessel 102 in a reverse flow direction from the second port 108 to the first port 106. In the reverse flow mode, the high pressure pump 116 output pressure may begreater than the circulation pump 122 output pressure, and the circulation pump 122 output flow rate may be preferably greater than the high pressure pump 116 output flow rate.

[0100] At 320, water 114 is permeated from the concentrate 115 via reverse osmosis through one or more constituent membranes 105 of the membrane modules 104 disposed in the pressure vessel 102, as the concentrate flows in the reverse flow direction. In the reverse flow mode, the water 114 is directed to flow as a permeate 114 out of the permeate outlet 110 of the pressure vessel 102.

[0101] At 322, permeation of dissolved solids from the concentrate is blocked from getting through the one or more membranes 105, as the concentrate flows in the reverse flow direction.

[0102] At 324, the concentrate 115 is circulated, via the circulation pump 122, back from the first port 106 to the second port 108.

[0103] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail herein (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein.

[0104] Although the invention has been described by reference to specific examples, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the disclosure not be limited to the described examples, but that it has the full scope defined by the language of the following claims.

Claims

CLAIMSWhat is claimed is:

1. A reverse osmosis system comprising: a pressure vessel comprising a first port, a second port and a permeate outlet; one or more membrane modules disposed in the pressure vessel, each membrane module having one or more membranes disposed therein, wherein the membranes are configured to permeate, via reverse osmosis, water as a permeate from a concentrate flowing between the first and second ports, wherein the membranes are also configured to block permeation of dissolved solids from the concentrate, and wherein the pressure vessel is configured to flow the permeate out the permeate outlet; a high pressure pump configured to pressurize feedwater to be added to the concentrate, wherein the high pressure pump includes a high pressure pump inlet through which the feedwater is supplied and a high pressure pump outlet; a circulation pump configured to circulate the concentrate between the first and second ports, wherein the circulation pump includes a circulation pump inlet and a circulation pump outlet; and a valved circulation apparatus configured to select between a forward flow mode of the system and a discharge mode of the system, wherein: in the forward flow mode, the circulation pump inlet is connected to the second port and the circulation pump outlet is connected to the first port, and in the discharge mode, the circulation pump inlet is connected to the high pressure pump inlet and the circulation pump outlet is connected to the first port.

2. The reverse osmosis system of claim 1, wherein, in the forward flow mode: the concentrate flows through the pressure vessel in a forward flow direction from the first port to the second port and the concentrate circulates back to the first port via the circulation pump; and the system produces permeate through the permeate outlet.

3. The reverse osmosis system of claim 2, wherein, in the forward flow mode: the high pressure pump output pressure is greater than the circulation pump output pressure; and the high pressure pump output flow rate is less than the circulation pump output flow rate.

4. The reverse osmosis system of claim 1, wherein, in the discharge mode: the concentrate flows through the pressure vessel from the first port to the second port and is discharged out of the system from the second port; and the system stops permeate production.

5. The reverse osmosis system of claim 4, wherein, in the discharge mode, the high pressure pump outlet pressure is: equal to or less than a predetermined threshold osmotic pressure of the system; and equal to or greater than the output pressure of the circulation pump.

6. The reverse osmosis system of claim 1 , wherein the valved circulation apparatus comprises: a first valve connected via a first tee to the inlet of the circulation pump and also connected via a second tee to the second port; a second valve connected via the first tee to the inlet of the circulation pump and also connected via a third tee to the inlet of the high pressure pump; a third valve connected via the second tee to the second port; the circulation pump outlet, the high pressure pump outlet and the first port connected together at a fourth tee; and a feed line for supplying feedwater connected to the third tee; wherein, during the forward flow mode, the first valve is open and the second and third valves are closed to: enable the high pressure pump to pressurize the system and to compensate for feedwater lost during permeate production, andenable the circulation pump to circulate the concentrate back through the pressure vessel in a forward flow direction from the first port to the second port; and wherein during the discharge mode, the first valve is closed and the second and third valves are open to enable discharge of the concentrate through the third valve.

7. The reverse osmosis system of claim 6, wherein the first valve, second valve and first tee comprise a single three-way valve.

8. The reverse osmosis system of claim 1, wherein the valved circulation apparatus is further configured to additionally select a reverse flow mode of the system, wherein: in the reverse flow mode, the circulation pump inlet is connected to the first port and the circulation pump outlet is connected to the second port.

9. The reverse osmosis system of claim 8, wherein, in the reverse flow mode: the concentrate flows through the pressure vessel in a reverse flow direction from the second port to the first port and circulates back to the second port via the circulation pump; and the system produces permeate through the permeate outlet.

10. The reverse osmosis system of claim 8, wherein the valved circulation apparatus comprises: a first valve connected via first tee to the first port and also connected to the high pressure pump outlet via a second tee in series connection with a third tee; a second valve connected via the first tee to the first port and also connected to the circulation pump inlet via a fourth tee in series connection with a fifth tee; a third valve connected to the fourth tee and also connected to the second port via a sixth tee in series connection with a seventh tee; a fourth valve connected to the second port via the seventh tee; a fifth valve connected to the second tee and sixth tee; the circulation pump outlet connected to the third tee; a sixth valve connected to the circulation pump inlet via the fifth tee and also connected to the high pressure pump inlet via an eighth tee; anda feed line for supplying feedwater connected to the eighth tee.

11. The reverse osmosis system of claim 10 wherein: during the forward flow mode, the first and third valves are open and the second, fourth, fifth and sixth valves are closed to: enable the high pressure pump to pressurize the system and to replenish feedwater lost during permeate production, and enable the circulation pump to circulate the concentrate back through the pressure vessel in a forward flow direction from the first port to the second port.

12. The reverse osmosis system of claim 10, wherein: during the discharge mode, the first, fourth and sixth valves are open and the second, third and fifth valves are closed to enable discharge of the concentrate through the fourth valve.

13. The reverse osmosis system of claim 10, wherein: during the reverse flow mode, the second and fifth valves are open and the first, third, fourth and sixth valves are closed to enable the circulation pump to circulate the concentrate back through the pressure vessel in a reverse flow direction from the second port to the first port.

14. The reverse osmosis system of claim 10, wherein the first valve, fifth valve and second tee comprise a single three-way valve.

15. The reverse osmosis system of claim 1, comprising: an energy recovery device (ERD), having a feedwater input port, a feedwater output port, a concentrate input port and a concentrate output port; wherein, during the discharge mode, the valved circulation apparatus is configured such that the feedwater from a feedline connected to the high pressure pump inlet enters the feedwater input port of the ERD as a low pressure feedwater and the concentrate from the pressure vessel enters the concentrate input port of the ERD as a high pressure concentrate; wherein, within the ERD, energy from hydraulic pressure of the high pressure concentrate is transferred to the low pressure feedwater; andwherein the feedwater exits the feedwater output port of the ERD as a high pressure feedwater and flows into the circulation pump inlet, and the concentrate exits the concentrate output port of the ERD as a low pressure concentrate and is discharged from the system.

16. A reverse osmosis system comprising: a pressure vessel comprising a first port, a second port and a permeate outlet; one or more membrane modules disposed in the pressure vessel, each membrane module having one or more membranes disposed therein, wherein the membranes are configured to permeate, via reverse osmosis, water as a permeate from a concentrate flowing between the first and second ports, wherein the membranes are also configured to block permeation of dissolved solids from the concentrate, and wherein the pressure vessel is configured to flow the permeate out the permeate outlet; a high pressure pump configured to pressurize feedwater to be added to the concentrate, wherein the high pressure pump includes a high pressure pump inlet through which the feedwater is supplied and a high pressure pump outlet; a circulation pump configured to circulate the concentrate between the first and second ports, wherein the circulation pump includes a circulation pump inlet and a circulation pump outlet; and a valved circulation apparatus configured to select between a forward flow mode of the system and a discharge mode of the system and a reverse flow mode of the system, wherein: in the forward flow mode, the circulation pump inlet is connected to the second port and the circulation pump outlet is connected to the first port, in the discharge mode, the circulation pump inlet is connected to the high pressure pump inlet and the circulation pump outlet is connected to the first port, and in the reverse flow mode, the circulation pump inlet is connected to the first port and the circulation pump outlet is connected to the second port.

17. The reverse osmosis system of claim 16, wherein: in the forward flow mode, the concentrate flows through the pressure vessel in a forward flow direction from the first port to the second port and the concentrate circulates back to thefirst port via the circulation pump, and the system produces permeate through the permeate outlet; in the discharge mode, the concentrate flows through the pressure vessel from the first port to the second port and is discharged out of the system from the second port, and the system stops permeate production; and in the reverse flow mode, the concentrate flows through the pressure vessel in a reverse flow direction from the second port to the first port and the concentrate circulates back to the second port via the circulation pump, and the system produces permeate through the permeate outlet.

18. The reverse osmosis system of claim 16, wherein: in the forward flow mode and the reverse flow mode: the high pressure pump output pressure is greater than the circulation pump output pressure, and the circulation pump output flow rate is greater than the circulation pump output flow rate; and in the discharge mode, the high pressure pump output pressure is: equal to or less than a predetermined threshold osmotic pressure of the system, and equal to or greater than the output pressure of the circulation pump.

19. The reverse osmosis system of claim 16, comprising: an energy recovery device (ERD), having a feedwater input port, a feedwater output port, a concentrate input port and a concentrate output port; wherein, during the discharge mode, the valved circulation apparatus is configured such that the feedwater from a feedline connected to the high pressure pump inlet enters the feedwater input port of the ERD as a low pressure feedwater and the concentrate from the pressure vessel enters the concentrate input port of the ERD as a high pressure concentrate; wherein, within the ERD, energy from hydraulic pressure of the high pressure concentrate is transferred to the low pressure feedwater; andwherein the feedwater exits the feedwater output port of the ERD as a high pressure feedwater and flows into the circulation pump inlet, and the concentrate exits the concentrate output port of the ERD as a low pressure concentrate and is discharged from the system.

20. A method of reverse osmosis comprising: selecting a forward flow mode of a reverse osmosis system, via a valved circulation apparatus of the system, wherein a circulation pump outlet of a circulation pump of the system is connected to a first port of a pressure vessel of the system and a circulation pump inlet of the circulation pump is connected to a second port of the pressure vessel; pressurizing concentrate, via a high pressure pump of the system, to flow through the pressure vessel in a forward flow direction from the first port to the second port; permeating water from the concentrate via reverse osmosis through one or more membranes of one or more membrane modules disposed in the pressure vessel, as the concentrate flows in the forward flow direction; blocking permeation of dissolved solids from the concentrate through the membranes, as the concentrate flows in the forward flow direction; circulating, via the circulation pump, the concentrate back from the second port to the first port; selecting a discharge mode of the system, via the valved circulation apparatus, wherein the circulation pump inlet is connected to a high pressure pump inlet of the high pressure pump and the circulation pump outlet is connected to the first port; and discharging out of the system, via the circulation pump, the concentrate flowing from the second port when the system is in the discharge mode.

21. The method of claim 20 comprising: in the forward flow mode, flowing the water as a permeate out of a permeate outlet of the pressure vessel; and in the discharge mode, stopping the flow of water as a permeate out of the permeate outlet.

22. The method of claim 20 comprising:in the forward flow mode, the high pressure pump output pressure is greater than the circulation pump output pressure, and the high pressure pump output flow rate is less than the circulation pump output flow rate; and in the discharge mode, the high pressure pump outlet pressure is equal to or less than a predetermined threshold osmotic pressure of the system, and equal to or greater than the output pressure of the circulation pump.

23. The method of claim 20, comprising: switching from the forward flow mode to the discharge mode after a predetermined saturation level of the system has been reached, and before an additional predetermined induction time of the system has elapsed.

24. The method of claim 20 comprising: selecting a reverse flow mode, via the valved circulation apparatus, wherein the circulation pump inlet is connected to the first port and the circulation pump outlet is connected to the second port; pressurizing the concentrate, via the high pressure pump, to flow through the pressure vessel in a reverse flow direction from the second port to the first port; permeating water from the concentrate via reverse osmosis through the membranes disposed in the membrane modules, as the concentrate flows in the reverse flow direction; blocking permeation of dissolved solids from the concentrate through the membranes, as the concentrate flows in the reverse flow direction; and circulating, via the circulation pump, the concentrate back from the first port to the second port.

25. The method of claim 24 comprising, in the reverse flow mode, flowing the water as a permeate out of the permeate outlet of the pressure vessel.

26. The method of claim 20, wherein, during the discharge mode: flowing feedwater, from a feedline connected to the high pressure pump inlet, as a low pressure feedwater into an energy recovery device (ERD);flowing the concentrate, from the pressure vessel, as a high pressure concentrate into theERD transferring energy from hydraulic pressure of the high pressure concentrate to the low pressure feedwater, within the ERD; flowing the feedwater as a high pressure feedwater out of the ERD and into the circulation pump inlet; flowing the concentrate as a low pressure concentrate out of the ERD; and discharging the low pressure concentrate out of the system.

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