FIELD OF THE TECHNOLOGY

[0001] One or more aspects relate generally to osmotic separation. More particularly, one or more aspects involve the use of osmotically driven membrane processes, such as forward osmosis, to separate solutes from aqueous solutions and systems and methods for maximizing solvent and/or solute recovery.

BACKGROUND

[0002] Forward osmosis has been used for desalination. In general, a forward osmosis desalination process involves a container having two chambers separated by a semi-permeable membrane. One chamber contains seawater. The other chamber contains a concentrated solution that generates a concentration gradient between the seawater and the concentrated solution. This gradient draws water from the seawater across the membrane, which selectively permits water to pass, but not salts, into the concentrated solution. Gradually, the water entering the concentrated solution dilutes the solution. The solutes are then removed from the dilute solution to generate potable water.

SUMMARY

[0003] Aspects of the invention relate generally to osmotically driven membrane systems and methods, including forward osmosis separation (FO), direct osmotic concentration (DOC), pressure-assisted forward osmosis (PAFO), and pressure retarded osmosis (PRO).

[0004] In one aspect, the invention relates to a system (and its corresponding method steps) for the osmotic extraction of a solvent from a first solution. The system includes a plurality of forward osmosis units, each having a first chamber having an inlet fluidly coupled to a source of the first solution, a second chamber having an inlet fluidly coupled to a source of a concentrated draw solution, and a semi-permeable membrane system separating the first chamber from the second chamber and configured for osmotically separating the solvent from the first solution, thereby forming a second solution in the first chamber and a dilute draw solution in the second chamber. The system also includes a separation system in fluid communication with the plurality of forward osmosis units and configured to separate the dilute draw solution into the concentrated draw solution and a solvent stream.

[0005] In various embodiments of the foregoing aspects, the concentrated draw solution includes ammonia and carbon dioxide in a desired molar ratio of greater than one to one.

However, other draw solutions are contemplated and considered within the scope of the invention, including, for example, NaCl or any of the various alternative draw solutions disclosed in PCT Patent Publication No. WO2014/078415 (the '415 publication), the disclosure of which is hereby incorporated by reference herein in its entirety. In addition, other systems and methods for separating and recovering draw solutes and the solvent, such as those disclosed in the '415 publication, are contemplated and considered within the scope of the invention.

Furthermore, various pretreatment and post-treatment systems can be incorporated in the forgoing aspects of the invention. The pretreatment systems can include at least one of a heat source for preheating the first solution, means for adjusting the pH of the first solution or the draw solution, means for disinfection (e.g., chemical or UV), separation and clarification, a filter or other means for filtering the first solution (e.g., carbon or sand filtration or reverse osmosis), means for polymer addition, ion exchange, or means for softening (e.g., lime softening) the first solution. The post-treatment systems can include at least one of a reverse osmosis system, an ion exchange system, a second forward osmosis system, a distillation system, a pervaporator, a mechanical vapor recompression system, a heat exchange system, or a filtration system (e.g., nano-, micro-, or ultrafiltration). In additional embodiments, the system can also include a recycling system including an absorber configured to facilitate reintroduction of the draw solutes to the second chamber to maintain the desired molar ratio of the draw solution.

[0006] In yet another aspect, the invention relates to a system for the osmotic extraction of a solvent from a first solution and maximizing recovery of a draw solute. The system includes a forward osmosis unit having at least one membrane having a first side and a second side. The one or more membranes can be arranged in series, parallel, or a combination of both. The first side of the at least one membrane is fluidly coupled to a source of the first solution and the second side of the at least one membrane is fluidly coupled to a source of a concentrated draw solution. The at least one membrane is configured for osmotically separating the solvent from the first solution, thereby forming a more concentrated first solution on the first side of the at least one membrane and a dilute draw solution on the second side of the at least one membrane. The system further includes a separation system in fluid communication with the forward osmosis unit and configured for receiving the dilute draw solution from the forward osmosis unit. The separation system includes a pressure driven membrane device, such as one or more reverse osmosis devices (e.g., arranged in series, parallel, or a combination of both), either alone or in combination with other pressure driven membrane devices, such as nanofiltration, ultrafiltration, and/or microfiltration to suit a particular application. The pressure driven membrane device includes an inlet configured for receiving a first portion of the dilute draw solution. The pressure assisted membrane device further includes a first outlet configured for outputting a retentate portion of the dilute draw solution (i.e., the portion of the dilute draw solution retained by the membrane) and a second outlet configured for outputting a permeate portion of the dilute draw solution (i.e., the portion of the dilute draw solution (solvent) that passes through the membrane under pressure). The separation system further includes an osmotically assisted, pressure driven membrane (OAPDM) device in fluid communication with the pressure driven membrane device. The OAPDM device includes a first inlet configured for receiving a second portion of the dilute draw solution, a second inlet configured for receiving the retentate portion of the dilute draw solution; a first outlet configured for outputting a further diluted dilute draw solution, and a second outlet configured for outputting a more concentrated retentate portion of the dilute draw solution (or re-concentrated draw solution). Typically, the first portion would be a substantial portion of the dilute draw solution; however, this may vary to suit a particular application (e.g., the nature of the separation systems, number of devices, etc.), and in some embodiments may be essentially all of the available dilute draw solution where an alternative solution is used to provide the osmotic assist.

[0007] In various embodiments of the foregoing aspect, the second outlet of the osmotically assisted pressure driven membrane device is in fluid communication with the second side of the forward osmosis membrane for providing the concentrated draw solution to the forward osmosis unit. The separation system can also include a valve arrangement (e.g., one or more valves, with or without the necessary sensors and controls for operating the valves) for returning the further diluted draw solution back to the dilute draw solution source. In some embodiments, the further diluted draw solution may be directed to an additional or alternative recovery process. In other embodiments, the second portion of the dilute draw solution is replaced by an alternative draw solution whose composition can be customized for the particular application (e.g., the desired differential pressure offset across the OAPDM device). In some embodiments, the re-concentrated draw solution output from the OAPDM device can be directed to an additional process/device, such as an evaporator or membrane brine concentrator for further concentration and/or solvent recovery.

[0008] In additional embodiments, the separation system further includes one or more booster pumps and/or other pressure transfer devices disposed between the forward osmosis unit and the pressure driven membrane device to pressurize the dilute draw solution. The separation system can further include one or more booster pumps and/or pressure transfer devices disposed between the first outlet of the pressure driven membrane device and the second inlet of the osmotically assisted pressure driven membrane device for boosting a pressure of the retentate portion of the dilute draw solution. In one or more embodiments, the pressure driven membrane device includes at least one RO unit. In some embodiments, multiple RO units are arranged in series, parallel, or combinations thereof. In some embodiments, the pressure driven membrane device includes different types of pressure driven membrane devices (e.g., at least one nanofiltration unit and at least one reverse osmosis unit in series). Typically, the permeate portion output from the pressure driven membrane device is the product solvent substantially free of any draw solutes. In various embodiments, the dilute draw solution and/or alternative saline solution can be tailored or otherwise modified in the case of the dilute draw solution to produce a specific differential osmotic pressure across the osmotically assisted pressure driven membrane device, which in turn can allow the device to operate at a higher hydraulic pressure, thereby obtaining greater concentration of the retentate stream. In some embodiments, the ideal differential osmotic pressure (Δπ) across the osmotically assisted pressure driven membrane device is zero, which would allow for a maximum net driving force applied to the retentate stream. However, the actual Δπ will vary depending on the overall osmotic pressure of the saline solution introduced to the draw side (e.g., envelope) of the osmotically assisted pressure driven membrane device. Additionally, the system can include a plurality of forward osmosis units arranged in series, wherein the first solution is introduced to each forward osmosis unit in countercurrent to the concentrated draw solution. In some embodiments, the concentrated feed exiting the last forward osmosis unit can be directed to an additional process/device, such as a crystallizer or spray dryer, for further concentration.

[0009] In another aspect, the invention relates to a method of extracting a solvent from a first solution and maximizing recovery of a draw solute. The method includes providing a forward osmosis unit having at least one membrane, such as that described above. Each of the one or more membranes in the system has a first side and a second side, wherein the

membrane(s) is configured for osmotically separating the solvent from the first solution. The method further includes the steps of introducing the first solution to the first side of the forward osmosis membrane; introducing a concentrated draw solution comprising the draw solute to the second side of the forward osmosis membrane; fluxing a portion of the solvent from the first solution across the at least one membrane into the concentrated draw solution, thereby forming a more concentrated first solution on the first side of the at least one membrane and a dilute draw solution on the second side of the at least one membrane; directing a first portion of the dilute draw solution to a pressure driven membrane device; introducing, under pressure, a retentate portion of the dilute draw solution from the pressure driven membrane device to a feed side of an osmotically assisted pressure driven membrane device; introducing a second portion of the dilute draw solution to a draw side of the osmotically assisted pressure driven membrane device to offset the total differential pressure across the osmotically assisted pressure driven membrane device; and directing a retentate output from the osmotically assisted pressure driven membrane device to the forward osmosis unit, wherein the retentate output includes the draw solute. [0010] Various embodiments of the method include the steps of outputting a permeate portion of the dilute draw solution from the pressure driven membrane device as a product solvent and/or returning the second portion of the dilute draw solution and a permeate from the osmotically assisted pressure driven membrane device to the dilute draw solution source. In some embodiments, the differential osmotic pressure across the osmotically assisted pressure driven membrane device can be regulated to control the concentration level of the retentate from the pressure driven membrane device, thereby controlling the concentration of the concentrated draw solution directed to the forward osmosis unit. Generally, the maximum draw solution concentration, and by extension recovery of solvent, can be controlled by increasing the net pressure applied to the retentate being concentrated in the osmotically assisted pressure driven membrane device (i.e., total driving force), which can be represented by J _w = Α(ΔΡ-Δπ), where J _w represents the flux across the membrane, A represents membrane permeability (essentially constant), ΔΡ represents the net hydrostatic pressure across the membrane, and Δπ represents the net osmotic pressure across the membrane. The Δπ is reduced by increasing the salinity of the dilute draw solution or alternative solution, thereby allowing for the increase of J _w and additional recovery of solvent.

[0011] Still other aspects, embodiments, and advantages of these exemplary aspects and embodiments, are discussed in detail below. Moreover, it is to be understood that both the foregoing information and the following detailed description are merely illustrative examples of various aspects and embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and embodiments. Accordingly, these and other objects, along with advantages and features of the present invention herein disclosed, will become apparent through reference to the following description and the accompanying drawings. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention and are not intended as a definition of the limits of the invention. For purposes of clarity, not every component may be labeled in every drawing. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which:

[0013] FIG. 1 is a schematic representation of a system for osmotic extraction of a solvent in accordance with one or more embodiments of the invention;

[0014] FIG. 2 is a schematic representation of an alternative system for osmotic extraction of a solvent in accordance with one or more embodiments of the invention;

[0015] FIG. 3 is a graphical representation of the effect of decreasing the differential osmotic pressure across the osmotically assisted pressure driven membrane device;

[0016] FIG. 4 is a schematic representation of another alternative system for the osmotic extraction of a solvent in accordance with one or more embodiments of the invention; and

[0017] FIG. 5 is a schematic representation of yet another alternative system for the osmotic extraction of a solvent in accordance with one or more embodiments of the invention.

DETAILED DESCRIPTION

[0018] In accordance with one or more embodiments, an osmotic method for extracting water from an aqueous solution may generally involve exposing the aqueous solution to a first surface of a forward osmosis membrane. A second solution, or draw solution, with an increased concentration relative to that of the aqueous solution may be exposed to a second opposed surface of the forward osmosis membrane. Water may then be drawn from the aqueous solution through the forward osmosis membrane and into the second solution generating a water-enriched solution via forward osmosis, which utilizes fluid transfer properties involving movement from a less concentrated solution to a more concentrated solution. The water-enriched solution, also referred to as a dilute draw solution, may be collected at a first outlet and undergo a further separation process to produce purified water. A second product stream, i.e., a depleted or concentrated aqueous process solution, may be collected at a second outlet for discharge or further treatment. Alternatively, the various systems and methods described herein can be carried out with non-aqueous solutions.

[0019] In accordance with one or more embodiments, a forward osmosis membrane module may include one or more forward osmosis membranes. The forward osmosis membranes may generally be semi-permeable, for example, allowing the passage of water, but excluding dissolved solutes therein, such as sodium chloride, ammonium carbonate, ammonium bicarbonate, and ammonium carbamate. Many types of semi-permeable membranes are suitable for this purpose provided that they are capable of allowing the passage of the solvent (e.g., water) while blocking the passage of the solutes and not reacting with the solutes in the solution. In some embodiments, the membrane(s) may have high selective permeability properties, thereby allowing the aforementioned solutes to pass through the membrane; however alternative types of membranes may be used to maximize performance of the system for a particular application, for example, feed chemistry, draw solution chemistry, ambient conditions, etc. [0020] In accordance with one or more embodiments, at least one forward osmosis membrane may be positioned within a housing or casing. The housing may generally be sized and shaped to accommodate the membranes positioned therein. For example, the housing may be substantially cylindrical if housing spirally wound forward osmosis membranes. The housing of the module may contain inlets to provide feed and draw solutions to the module as well as outlets for withdrawal of product streams from the module. In some embodiments, the housing may provide at least one reservoir or chamber for holding or storing a fluid to be introduced to or withdrawn from the module. In at least one embodiment, the housing may be insulated.

[0021] In accordance with one or more embodiments, a forward osmosis membrane module may generally be constructed and arranged so as to bring a first solution and a second solution into contact with first and second sides of a semi-permeable membrane, respectively. Although the first and second solutions can remain stagnant, it is preferred that both the first and second solutions are introduced by cross flow, i.e., flows parallel to the surface of the semipermeable membrane. This may generally increase membrane surface area contact along one or more fluid flow paths, thereby increasing the efficiency of the forward osmosis processes. In some embodiments, the first and second solutions may flow in the same direction. In other embodiments, the first and second solutions may flow in opposite directions. In at least some embodiments, similar fluid dynamics may exist on both sides of a membrane surface. This may be achieved by strategic integration of the one or more forward osmosis membranes in the module or housing.

[0022] In accordance with one or more embodiments, draw solutes may be recovered for reuse. A separation system may strip solutes from the dilute draw solution to produce product water substantially free of the solutes. In some embodiments, the separation system may include a distillation column or other thermal or mechanical recovery mechanism. Draw solutes may then be returned, such as by a recycling system, back to the concentrated draw solution. Gaseous solutes may be condensed or absorbed to form a concentrated draw solution. An absorber may use dilute draw solution as an absorbent. In other embodiments, product water may be used as an absorbent for all or a portion of the absorption of the gas streams from a solute recycling system. Examples of different osmotically driven systems, including separation/recovery systems are described in U.S. Patent Nos. 6,391,205, 8,002,989, 9,039,899, and 9,044,711; and U.S. Patent Publication Nos. 2011/0203994, 2012/0273417, 2012/0267306, and 2014/0224718, PCT Patent Application No. PCT/US 15/23542, filed March 31, 2015, and PCT/US 15/45059, filed August 13, 2015; and U.S. Provisional Patent Application No. 62/163,781, filed May 19, 2015; the disclosures of which are hereby incorporated by reference herein in their entireties.

[0023] FIG. 1 depicts a system 200 for the osmotic extraction of a solvent that is configured to enhance maximum brine concentration. The exemplary embodiment of the system 200 shown in FIG. 1 generally includes one or more FO modules 212 (the descriptions of which are incorporated herein), each including one or more FO membranes 213, one or more pressure driven membrane modules 242 (e.g., RO) including membranes 243, and one or more osmotically (i.e., FO) assisted pressure driven membrane modules 246, each including one or more FO membranes 247. This arrangement would typically be beneficial in/with systems that utilize a pressure driven membrane process for recovering draw solutes and/or other industries where maximum brine concentration is desirable.

[0024] Generally, pressure driven membrane devices, such as RO units, are typically limited to about 1500 psi (more typically about 1000 psi) and can only produce a

brine/concentrate of about 75,000 mg/1 to about 105,000 mg/1. In FO systems that utilize RO (or other pressure driven membrane process) for draw solution re-concentration, this limits the maximum draw solution concentration. By operating a FO membrane (e.g., a spiral wound membrane, although other configurations such plate and frame and hollow fiber are also contemplated and considered within the scope of the invention) in a pressure driven mode, with a saline solution passing through the draw solution chamber of the FO module/membrane, the net driving force on the solution passing through the feed solution chamber of the FO

module/membrane is increased as the osmotic pressure on the draw side offsets the osmotic pressure on the feed side, thereby reducing Δπ and allowing for a higher hydrostatic pressure on the feed side as discussed herein.

[0025] Referring back to FIG. 1, a feed or first solution is introduced to the one or more

FO units 212, while a concentrated draw solution 216 is introduced to the FO unit(s) 212 on the opposite side(s) of the membrane(s) 213. The concentrated draw solution 216 has a higher osmotic pressure than the feed solution 214, thereby causing a solvent 248 to flux across the membrane(s) 213. The FO unit(s) 212 outputs the resulting concentrated feed stream (e.g., brine) 214' and dilute draw solution 216' . The concentrated feed 214' can be sent for further processing or otherwise discarded. The dilute draw solution 216' is sent for recovery of the solvent 248 and re-concentration of the draw solution 216.

[0026] As shown in FIG. 1, a first portion 216a' of the dilute draw solution 216' is directed to the pressure driven membrane device 242 via one or more valve arrangements 257 and a booster pump 259b or other pressure transfer device and a second portion 216b' of the dilute draw solution is directed to the osmotically assisted pressure driven membrane device 246 via the valve arrangement 257a and optionally a pressure transfer device 259a. Generally, the valve arrangements 257 can be manually or automatically actuated as necessary to regulate the flow of dilute draw solution 216' to the various membrane devices. In some embodiments, the valve arrangements 257 are configured to isolate the first and second portions of the dilute draw solution (e.g., via multiple multi-directional valves 257a, 257b), prevent "short-circuiting" of dilute draw solution through the OAPDM device (e.g., check valve 257d), and/or control mixing of draw solution streams of different concentrations.

[0027] More specifically, a further diluted dilute draw solution 215 (this is the first portion 216a' of the dilute draw solution mixed with the further diluted draw solution 216" from the OAPDM 246) is introduced to the pressure driven membrane device 242 under pressure via the pump 259b. In one or more embodiments, the solution 215 is introduced at about 1000 psi to about 3000 psi, preferably about 1500 psi to 2000 psi. Generally, it is desirable to introduce the solution 215 at as high a pressure as possible, within the limitations of the system components operating capacities. The desired solvent 248 will pass through the membrane as the permeate, where it can be used as is or sent for further processing. The retentate portion 215' (essentially an intermediate concentrated draw solution), with a substantial portion of the solvent removed, is now directed to the osmotically assisted pressure driven membrane device 246, either via the residual pressure from the pump 259b or via an additional pump 259c to further boost the pressure of the intermediate concentrated draw solution 215' . In some embodiments, a backpressure valve 257c is used to maintain a desired pressure on the retentate passing through the OAPDM device 246. At the same time, the second portion 216b' of the dilute draw solution 216' is directed to the opposite side (e.g., draw side or envelope side in a spiral wound membrane module) of the membrane 247 in the OAPDM device 246 via the valve arrangement 257a and optionally a low pressure pump or other pressure transfer device 259a, as necessary. Additional solvent 248 from the retentate 215' is pushed through the membrane 247 and into the dilute draw solution 216b' , further diluting the dilute draw solution. This further diluted dilute draw solution 216" is then directed back to and mixed with the first portion of the dilute draw solution 216a' directed to the pressure driven membrane device 242 via valve arrangement 257b. This arrangement allows for the essentially continuous recovery of additional solvent not otherwise recoverable via pressure driven membrane processes alone, which also results in maximizing the concentration of the draw solution or any other brine source. In some embodiments, the system 200 includes a by-pass line 231 and valve arrangement 257e that can be used to direct all or a portion of the retentate 215' from the pressure driven membrane device 242 directly to the FO unit(s) 212. In some cases, the by-pass may be used as necessary to maintain/deliver a draw solution having the desired concentration to the FO unit(s) 212. For example, a portion of the retentate can by-pass the OAPDM device 246 and be mixed with the output therefrom to customize the concentration of the dilute draw solution for a particular feed solution composition. In other examples, the by-pass can be used to take the OAPDM device 246 off-line for maintenance purposes.

[0028] In an alternative embodiment, the second portion of the dilute draw solution is replaced with an independent source of saline solution 261 (361 in FIG. 2). In this arrangement, the entire or substantially all of the dilute draw solution 216' is directed to the pressure driven membrane device 242. The independent source of saline solution can be selected to provide a desired osmotic pressure (π^ in Fig. 2) sufficient to offset the osmotic pressure (πρ in FIG. 2) of the retentate 215', thereby allowing for additional concentration of the retentate 215' . Ideally, the independent source of saline solution has a sufficient osmotic pressure to offset about 100% of the osmotic pressure of the retentate 215' ; however, in most embodiments, the will offset about 25% to about 75% of πρ, and preferably at least 50%. In some embodiments, the independent saline solution can be made up of a portion of the retentate 215' mixed with the dilute draw solution 216' and/or product solvent 248 as necessary to achieve the desired osmotic pressure.

[0029] FIG. 2 depicts an alternative embodiment of a system 300 for the osmotic extraction of a solvent from a first solution and the maximizing of a concentrate stream, similar to the system of FIG.l. As shown in FIG. 2, there is a basic system 310 for the extraction of a solvent from a first solution via one or more FO units, as described above, and a separation system 339 for the extraction of the solvent 348 and the recovery of the draw solutes. The separation system 339 includes one or more pressure driven membrane devices 342 and one or more osmotically assisted pressure driven membrane devices 346, along with assorted pumps 359 and valve arrangements 357 as necessary for the operation thereof.

[0030] In one exemplary embodiment, the various streams have the characteristics given in Table 1. The foregoing concentrations may vary depending on the nature of the feed stream and the draw solution composition.

G A further diluted dilute draw solution with a concentration of about 20,000 mg/1.

Table 1

[0031] During operation, stream A is fed to both the pressure driven membrane device

342 and the OAPDM device 346 with a concentration of about 30,000 mg/1. At the pressure driven membrane device 342, stream A is concentrated up to about 100,000 mg/1 as stream D. Stream A (stream F as directed to the OAPDM device 346) is diluted by the OAPDM device 346 to a concentration of about 20,000 mg/1 (stream G), which is directed back to pressure driven membrane device 342. At start-up this may be the case, but as the system reaches a steady state, stream A to device 342 is replaced by stream B, which is a mixture of stream A and stream G. Stream D exiting the pressure driven membrane device 342 is then directed to the OAPDM device 346 on the feed side of the membrane 347, where it is further concentrated up to about 125,000 mg/1 (stream E) to form the concentrated draw solution 316.

[0032] FIG. 3 is a graphical representation of the effect of the inventive arrangement on the recovery of solvent via the OAPDM device 246, 346. Specifically, FIG. 3 depicts the improvement in recovery of solvent (i.e., increased flux J _w ) over the length (oi) of the device

246, 346 as represented by J _w = Α(ΔΡ-Δπ). As shown, the differential hydrostatic pressure (ΔΡ) stays relatively constant as the streams pass through the OAPDM device, while the differential osmotic pressure (Δπ) increases. This is, at least in part, because the saline stream on the draw or envelope side of the device becomes more dilute, thereby lowering πκ, while the retentate stream on the feed side becomes more concentrated, thereby increasing π and resulting in an overall increase in Δπ. Referring back to J _w = Α(ΔΡ-Δπ), as Δπ increases, flux decreases; approaching zero as the feed stream passes through the membrane device (point A in FIG. 3, where ΔΡ = Δπ;

J _w = 0). In a typical pressure driven membrane device, there is no saline stream introduced to the opposite side of the membrane (i.e., = 0), so Δπ starts out high and reaches ΔΡ quickly. By introducing a saline stream to the opposite side of the pressure driven membrane (i.e., > 0), the Δπ is lowered and takes longer to reach ΔΡ as the opposing streams pass through the device 246, 346 (point B in FIG. 3), which significantly improves the overall solvent recovery through the membrane device 246, 346. As shown in FIG. 3, this additional recovery is represented by the shaded area bound by lines Δπ(Α) and Δπ(Β). Lowering Δπ leads to increased solvent recovery and solute concentration.

[0033] FIG. 4 depicts another alternative embodiment of a system 400 for the osmotic extraction of a solvent from a first solution and maximizing concentration of a second solution, similar to those previously described. Generally, the overall system 400 includes a basic FO module/system 212, 310, as previously described and not shown in FIG. 4 for the sake of clarity, in fluid communication with a separation system 439. The separation system 439 depicted in FIG. 4 includes one or more pressure driven membrane devices 442 in fluid communication with one or more OAPDM devices 446 and any necessary pumps, valves, sensors, plumbing, etc.

[0034] As shown in FIG. 4, a dilute draw solution stream 416' is directed to the separation system 439, in particular to the first pressure driven membrane device 442a. In some embodiments, only a portion of the dilute draw solution 416a' is directed to the first pressure driven membrane device 442a, while a typically smaller portion of the dilute draw solution 416b' is directed to the OAPDM device 446. Alternatively or additionally, an independent source of a saline solution 461 can be directed to the OAPDM device 446. Similar to the system depicted in FIG. 2, the retentate 415' from device 442a can be directed to the OAPDM device 446.

However, all or a portion of the retentate 415' can be directed to a second pressure driven membrane device 442b for further concentration of the draw solution. The permeate 448a from device 442a can be output as a product solvent, sent for further processing or discarded. The retentate 429 from the second device 442b can be directed to the OAPDM device 446 for further concentration and reuse as concentrated draw solution 416. In some embodiments, a plurality of pressure driven membrane devices 442 in series may be used to suit a particular application, for example, to achieve a particular concentration of the draw solution. The permeate 448b of the second device 442b can be output as a product solvent, sent for further processing or discarded. In some embodiments, all or a portion of the permeate 448b is directed to the inlet of the first device 442a to create a more diluted draw solution 415 and increase the recovery of the first pressure driven membrane device 442a. Additionally or alternatively, all or a portion of the permeate 448b of the second device 442b (or last in a series of devices) can be combined with the permeate 448a of the first device 442a. In some cases, it may be particularly useful to combine the permeate 448b of the second device 442b with the permeate 448a of the first device and/or return at least a portion of the permeate 448b to the inlet of the first device 442a, as the permeate 448b may have a higher TDS concentration than acceptable for certain uses.

[0035] Generally, the OAPDM device 446 operates essentially as described with respect to FIGS. 2 and 3. In particular, the retentate 415a' of the first device 442a, either alone or in combination with the separate saline source 461, is directed to the draw side of the FO membrane 447 (stream 421), while the retentate 429 of the second (or final) device 442b is directed to the feed side of the membrane 447 under pressure for further concentration. The diluted output 416" is directed back to the inlet of the first device 442a, while the concentrated output 416 is directed back to the FO module(s) for reuse as concentrated draw solution.

[0036] FIG. 5 depicts another alternative embodiment of a system 500 for the osmotic extraction of a solvent from a first solution and maximizing concentration of a second solution, similar to those previously described. Generally, the overall system 500 includes a sub-system 510 of one or more forward osmosis modules 512 and related componentry, similar to that previously described or incorporated herein, in fluid communication with a separation system 539. The separation system 539 depicted in FIG. 5 includes one or more pressure driven membrane devices 540, 542 in fluid communication with one or more OAPDM devices 546 and any necessary pumps, valves, sensors, plumbing, etc. In addition, the system 500 shown in FIG. 5 includes optional sub- systems/devices for further concentrating the concentrated feed stream 514' (e.g., a crystallizer or spray drier 564) and/or further recovering solvent from the dilute draw solution 516' (e.g., an evaporator or FO sub-system 566), as described below. The system 500 may also include means 550 for chemical addition at various locations throughout the system 500, such as those previously described or incorporated herein. For example, the means 550 can be used for adding an acidic or caustic substance to adjust the pH of one or more streams within the system 500, such as lowering the pH of the feed or concentrated draw solutions 514, 516 or raising the pH of the dilute draw solution 516' .

[0037] As generally shown in FIG. 5, the dilute draw solution 516' is directed to a

NF/UF unit 540 and related circuitry, and one or more pressure driven membrane devices 542 in combination with one or more OAPDM devices 546, similar to those described with respect to FIGS. 1, 2, and 4. In some embodiments, unit 540 can be an ion exchange or similar treatment unit. As shown in FIG. 5, the re-concentrated draw solution 554 exiting the OAPDM device 546 is directed to an additional process prior to being returned to the FO module(s) 512. In various embodiments, the additional process includes the use of a thermal and/or mechanical device 566, such as an evaporator or membrane brine concentrator (e.g., one or more FO modules 512), with the device 566 outputting the final concentrated draw solution 516 and one or more product solvent streams 548" (in the case of an evaporator), 549 (in the case of an FO module). The system 500 may also include a combined heat and power source 568 (e.g., a gas turbine) for supplying the necessary thermal and/or electrical energy 569 to the device 566 and a brine maker 556 as previously described. In one optional embodiment, the system 500 incorporates an electrodialysis reversal unit (EDR) 567 instead of or in addition to the brine maker 556 to provide make-up draw solutes.

[0038] As shown in FIG. 5, the EDR 567 is disposed between the feed stream 514 (prior to the FO module 512) and the separation system 539 and can be operated continuously or as needed. Specifically, the EDR 567 receives a portion of the feed stream 514 and a portion of the dilute draw solution (e.g., a portion of the dilute draw solution 552 permeated through the NF/UF membrane unit 540) and transfers a portion of the salt dissolved in the feed 514 to the dilute draw solution to make up for any draw solutes (e.g., NaCl) lost to the NF/UF membrane unit 540 or elsewhere in the system 500. The retentate 537 output from the NF/UF unit 540 can be recycled back to the feed stream 514. The EDR 567 provides a less expensive way of replacing the draw solutes lost in the system than continuously adding new draw solutes (e.g., the cost of the EDR 567 vs. the cost of the brine maker 556 and raw materials).

[0039] The separation system 539 shown in FIG. 5 differs, in part, from the previously described systems insofar as it includes a third pressure driven membrane device 542c in the form of a polishing reverse osmosis device. The device 542c is configured to receive permeate and/or product solvents 548, 549 from any of the other devices within the system 539 and output potable water 548'. In some embodiments, this output 548' can be combined with the product solvent 548" output by device 566 if it is of sufficient quality, or if not, the product solvent 549 of the device 566 can be processed by the third pressure driven membrane device 542c. The retentate 529b of the third device 542c can be directed back through the separation system 539 to recover additional draw solutes and/or solvent.

[0040] In addition, the system 500 shown in FIG. 5 may include the afore-mentioned additional system/device 564 for further concentration of the feed solution, which in one embodiment is a crystallizer for outputting a solid waste product 514". As shown in FIG. 5, the device 564 is configured for receiving the concentrated feed 514' from the FO module(s) and/or any overflow 528 from the hydrocyclone circuits 523, which includes one or more

hydrocyclones 524 in fluid communication with the forward osmosis module 512 via underflow, overflow, and feed lines 527, 528, 526. Generally, the hydrocyclone 524 is used to control solids size and dwell time within a particular forward osmosis module 512. The hydrocyclone circuit 523 can be used to feed/forward the right amount of solids (typical with some amount of clear solvent or portion of feed stream) generated in each stage to the following stage in the system 500. As also shown, the device 564 is configured for receiving thermal and/or electrical energy 569 from the combined heat and power source 568.

[0041] In accordance with one or more embodiments, the devices, systems and methods described herein may generally include a controller for adjusting or regulating at least one operating parameter of the device or a component of the systems, such as, but not limited to, actuating valves and pumps, as well as adjusting a property or characteristic of one or more fluid flow streams through an osmotically driven membrane module, or other module in a particular system. A controller may be in electronic communication with at least one sensor configured to detect at least one operational parameter of the system, such as a concentration, flow rate, pH level, or temperature. The controller may be generally configured to generate a control signal to adjust one or more operational parameters in response to a signal generated by a sensor. For example, the controller can be configured to receive a representation of a condition, property, or state of any stream, component, or subsystem of the osmotically driven membrane systems and associated pre- and post-treatment systems. The controller typically includes an algorithm that facilitates generation of at least one output signal that is typically based on one or more of any of the representation and a target or desired value, such as a set point. In accordance with one or more particular aspects, the controller can be configured to receive a representation of any measured property of any stream, and generate a control, drive or output signal to any of the system components, to reduce any deviation of the measured property from a target value.

[0042] In accordance with one or more embodiments, process control systems and methods may monitor various concentration levels, such as may be based on detected parameters including pH and conductivity. Process stream flow rates and tank levels may also be controlled. Temperature and pressure may be monitored. Membrane leaks may be detected using ion selective probes, pH meters, tank levels, and stream flow rates. Leaks may also be detected by pressurizing a draw solution side of a membrane with gas and using ultrasonic detectors and/or visual observation of leaks at a feedwater side. Other operational parameters and maintenance issues may be monitored. Various process efficiencies may be monitored, such as by measuring product water flow rate and quality, heat flow and electrical energy consumption. Cleaning protocols for biological fouling mitigation may be controlled such as by measuring flux decline as determined by flow rates of feed and draw solutions at specific points in a membrane system. A sensor on a brine stream may indicate when treatment is needed, such as with distillation, ion exchange, breakpoint chlorination or like protocols. This may be done with pH, ion selective probes, Fourier Transform Infrared Spectrometry (FTIR), or other means of sensing draw solute concentrations. A draw solution condition may be monitored and tracked for makeup addition and/or replacement of solutes. Likewise, product water quality may be monitored by conventional means or with a probe such as an ammonium or ammonia probe. FTIR may be implemented to detect species present providing information which may be useful to, for example, ensure proper plant operation, and for identifying behavior such as membrane ion exchange effects.

[0043] Those skilled in the art should appreciate that the parameters and configurations described herein are exemplary and that actual parameters and/or configurations will depend on the specific application in which the systems and techniques of the invention are used. Those skilled in the art should also recognize or be able to ascertain, using no more than routine experimentation, equivalents to the specific embodiments of the invention. It is, therefore, to be understood that the embodiments described herein are presented by way of example only and that, within the scope of the appended claims and equivalents thereto; the invention may be practiced otherwise than as specifically described.

[0044] Moreover, it should also be appreciated that the invention is directed to each feature, system, subsystem, or technique described herein and any combination of two or more features, systems, subsystems, or techniques described herein and any combination of two or more features, systems, subsystems, and/or methods, if such features, systems, subsystems, and techniques are not mutually inconsistent, is considered to be within the scope of the invention as embodied in the claims. Further, acts, elements, and features discussed only in connection with one embodiment are not intended to be excluded from a similar role in other embodiments.

[0045] What is claimed is: