Field of the Invention

The present invention relates to the field of water purification. More particularly, the invention relates to a forward osmosis purification unit.

Background of the Invention

The phenomenon by which water is transported across a semi-permeable membrane is referred to as osmosis. Osmosis, often known as forward osmosis, is generally driven by a difference is solute concentrations across the membrane that allows permeation of water, but rejects many solute molecules or ions. Water flows across the membrane from a region of low osmotic pressure, which is proportional to the concentration of a solute within a solvent, to a region of high osmotic pressure until the difference in hydrostatic pressure of the two regions counterbalances the difference in osmotic pressure.

One common method of water purification is associated with reverse osmosis, whereby the hydraulic pressure of an aqueous feed solution containing solutes to be filtrated is increased to a level greater than the osmotic pressure. Water is consequently driven across the membrane while the solutes remain. Although this purification method is effective, it is energy intensive since a pump is required, and therefore does not provide a feasible solution for large capacity water purification, such as during periods of a water pollution catastrophe.

Many forward osmosis purification units are known in the prior art. The difference in osmotic pressure is the driving force in causing water to be transported across the semi-permeable membrane from a feed solution to a highly concentrated draw solution. The time for water to permeate the membrane while diluting the draw solution is relatively long, and therefore prior art forward osmosis purification methods will not generate potable water at a sufficiently high rate needed for emergency relief. Also, the draw solute has to be separated from the draw solution in order to benefit from the transported water.

It is an object of the present invention to provide a forward osmosis purification unit that purifies water at a significantly higher rate that of prior art units.

It is an additional object of the present invention to provide a forward osmosis purification unit that also separates draw solutes from the water that has been transported across the semi-permeable membrane.

Other objects and advantages of the invention will become apparent as the description proceeds.

Summary of the Invention

The present invention provides a forward osmosis purification unit, comprising an inlet chamber into which an unpurified feed solution is introducible, an outlet chamber from which purified permeate is dischargeable, and a dual membrane section for purifying said feed solution and for directing said permeate to said outlet chamber, wherein said dual membrane section comprises a first semi-permeable membrane having a first pore size in fluid communication with said inlet chamber, a second semi-permeable membrane in fluid communication with said outlet chamber and having a second pore size which is substantially equal to or greater than said first pore size, a plurality of expandable cells interposed between said first and second membranes, and a draw solution containing a draw agent which is received in each of said cells of an osmotic pressure significantly greater than the osmotic pressure of said feed solution, wherein a sufficient amount of solvent derived from said feed solution is permeable through said first membrane to increase the hydraulic pressure of said draw solution within each of said cells while solutes of said feed solution are substantially rejectable, wherein the hydraulic pressure of said draw solution within each of said cells is sufficiently high to force said permeate to be discharged from said second membrane to said outlet chamber while said draw agent is substantially rejected.

In one aspect, the purification unit further comprises a conduit in fluid communication with the outlet chamber and with a vacuum source for increasing the rate of generating the permeate.

In one aspect, the purification unit is a hydration bag.

In one aspect, the hydration bag comprises an outer bag made from a waterproof and elastic material, an inner bag comprising the dual membrane section which is disposed within said outer bag, a liquid impermeable seal line applied to said outer bag to define and separate the inlet chamber and outlet chamber, said seal line being attached to an edge of said inner bag which faces the outlet chamber, and a completely sealed terminal surface covering an edge of said inner bag which faces the inlet chamber, wherein the feed solution is forced to be transported osmotically across, and around the entire periphery of, the first membrane of said inner bag, and the permeate is discharged from the second membrane of said inner bag into an inner bag interior in fluid communication with the outlet chamber.

In one aspect, the inlet chamber and outlet chamber are rigid tanks. The inlet chamber is positioned on top of a base, the outlet chamber being configured with an open top is positioned in abutting relation with, and at a same height as, said base, and the dual membrane section is attached to a side of the inlet chamber so as to be above the outlet chamber, the permeate being discharged gravitationally from the dual membrane section to the outlet chamber. In one aspect, the inlet chamber is positioned on top of the outlet chamber and the dual membrane section is positioned between, and in fluid communication with, the inlet chamber and the outlet chamber, the permeate being transportable gravitationally and osmotically through the dual membrane section and dischargeable gravitationally from the dual membrane section to the outlet chamber.

In one aspect,the dual membrane section is a replaceable cartridge.

Brief Description of the Drawings

In the drawings:

-Fig. 1 is a schematic illustration of a forward osmosis purification unit according to one embodiment of the present invention;

-Fig. 2 is a schematic illustration of the expansion of a cell of the purification unit of Fig. 1, according to one embodiment of the present invention;

-Fig. 3 is a schematic illustration of the expansion of a cell of the purification unit of Fig. 1, according to another embodiment of the present invention;

-Fig. 4 is a schematic illustration of a purification unit according to another embodiment of the present invention;

-Fig. 5 is a schematic illustration of a purification unit according to another embodiment of the present invention;

-Fig. 6 is a schematic illustration of apparatus used in conjunction with the purification unit of Fig. 5;

- Fig. 7 is a front view of a hydration bag comprising the purification unit of Fig.

5;

- Fig. 8 is a schematic illustration of the hydration bag of Fig. 7, showing the relative position of the dual membrane section;

-Fig. 9 is a rear view of a hydration bag which comprises a vacuum port;

-Fig. 10 is a perspective view of another implementation of the purification unit of Fig. 1; - Fig. 11 illustrates the test apparatus used to determine the efficacy of the purification unit of the present invention as described in Example 1;

-Fig. 12 illustrates the test apparatus used in conjunction with Example 2;

-Fig. 13 is a schematic illustration of a hydration bag according to another embodiment of the invention, showing the flow of liquid to the outlet chamber; - Fig. 14 is a perspective view from the front and bottom of an implementation of the inner bag of the hydration bag of Fig. 13, shown in a collapsed condition; and

- Fig. 15 is a front view of an implementation of the hydration bag of Fig. 13, shown in a collapsed condition.

Detailed Description of Preferred Embodiments

The present invention is a novel forward osmosis purification unit that comprises two semi-permeable membranes and a plurality of cells interposed between the two membranes for generating a sufficiently high hydraulic pressure which causes potable water to be separated from a draw agent.

Fig. 1 schematically illustrates a forward osmosis purification unit according to one embodiment of the present invention, which is generally designated by numeral 10. Purification unit 10 comprises an inlet chamber 6 through which an unpurified feed solution F flows, an outlet chamber 17 through which purified permeate P discharged from purification unit 10 is flowable, a first semi-permeable membrane 5 having a first pore size 1 in fluid communication with inlet chamber 6, and a second semi-permeable membrane 8 in fluid communication with outlet chamber 17 and having a second pore size 3 substantially equal to, or greater than, first pore size 1, across which permeate P, generally fresh water, is discharged at the end of the purification process. Outlet chamber 17 may have a larger volume than inlet chamber 6. A plurality of substantially parallel partition elements 4 extend from membrane 5 to membrane 8. A plurality of cells 9 are thereby defined by the two membranes 5 and 8 and by two adjacent partition elements 4. Each partition element is connected to a membrane by an attachment 11, e.g. an adhesive such as made from urethane or an ultrasonic connection.

Semi-permeable membranes 5 and 8 act as a barrier for allowing small molecules such as water to pass through while rejecting larger molecules such as salts, sugars, starches, proteins, viruses, urea, bacteria, and parasites. Each of the membranes may be based on any suitable filtration technology, such as microfiltration for separating macro-molecules such as microorganisms including bacteria on the order of 2 μπι, ultrafiltration for separating viruses and molecules including organic compounds having a size of as little as 100 nm, and nanofiltration for separating ions having a size of as little as 10 nm. A membrane type is selected based on the type of solute commonly found in feed solution F.

Into each cell 9 is introduced a sufficiently large amount of draw agent 12 that will produce a draw solution D which is more concentrated than feed solution F. Due to the increased osmotic pressure of draw solution D with respect to feed solution F, the solvent of feed solution F is caused to be transported across first membrane 5 to each of the pluralities of cells 9, while the feed solution solutes including contaminants or pollutants are rejected by first membrane 5.

Draw agent 12 may be introduced in many different forms, such as a powder, crystal, solid plate, semi-wet (gel form) and wet. The ratio between the mass of draw agent in each cell to the cell volume may be any selected value, although draw solution D is preferably saturated in order to increase the filtration volume.

Exemplary and non-limitating types of a draw agent that may be employed include glucose, dextrose, trehalose, sucrose, cellulose, cellulose derivates, polysaccharides, polyamines, salts, and calcium chloride. It will be appreciated that other types of a draw agent may be employed, insofar that its molecular size is sufficiently high, generally on the order of microns, to be substantially rejected by the second membrane 8. Consequently, the draw agent concentration within permeate P will be relatively low or marginal at outlet chamber 17.

As shown in Fig. 2, the osmotically induced influx of the feed solution derived solvent into a cell 9 increases the cell volume. Following the transport of a significant amount of solvent into cell 9, the hydraulic pressure of draw solution D is increased. Eventually thin-walled membranes 5 and 8, which may be made of a flexible material, e.g. a material such as a polyester mesh, PVDF or cellulose acetate which is embedded within polymer material, yield between two adjacent connections 11 in response to the pressure differential between hydrostatic pressure H applied thereto by draw solution D and the combined effect of near atmospheric pressure A and the hydraulic pressure applied onto the membranes by feed solution F or permeate P. The membranes may change their configuration from a substantially planar configuration 13 illustrated schematically by dotted lines to a concave configuration. As a result of the change in configuration, the cell volume increases to permit an additional influx of solvent, resulting in a corresponding increase of the pressure of draw solution D. The change in size of a cell 9 in response to the influx of the feed solution derived solvent may range from 0.1mm to 4 cm.

Although the membranes change their configuration in response to the pressure differential to which they are exposed, partition elements 4 do not change their configuration since an equal but oppositely directed hydrostatic pressure H is applied onto each partition element from each adjacent cell 9. By employing a plurality of expandable cells 9, the purification unit 10 is advantageously adapted to convert a difference in osmotic pressure between feed solution F and draw solution D into mechanical power as a result of the increased hydraulic pressure with each cell, and to thereby cause the draw agent to be separated from the associated solvent and permeate P to be transported across second membrane 8 into outlet chamber 17.

The difference in hydraulic pressure between cell 9 and outlet chamber 17, which may range from 10-30 bar, is the driving force for separating draw agent 12 from draw solution D. Due to the hydraulic pressure differential between cell 9 and outlet chamber 17, draw solution D is forced to flow towards second membrane 8. The pore size of membrane 8 is selected to allow permeate P to pass therethrough while rejecting draw agent 12. The separated draw agent which remains in cell 9 can be reused. Even though there is also a hydraulic pressure differential between cell 9 and inlet chamber 6, permeate P flows only to outlet chamber 17 but not to inlet chamber 6 due to the large difference in osmotic pressure between cell 9 and inlet chamber 6 which counteracts the effect of the hydraulic pressure differential. Alternatively, a sufficiently increased pore size of second membrane 8 relative to first membrane 5, if so desired, and the corresponding decreased hydraulic resistance through second membrane 8 will prevent permeate from flowing to the inlet chamber. The difference in osmotic pressure between feed solution F and draw solution D may range from 5-60 bar, depending on the type of feed solution, in order to ensure a suitable flux of solvent into cell 9 while overcoming the opposing hydraulic pressure differential between cell 9 and inlet chamber 6.

The net amount of permeate that is generated by the purification unit is the product of permeate flux from each cell and the number of cells, and is significantly greater than that of the prior art due to the significantly increased hydraulic pressure of draw solution D within each cell 9 which drives the transport of permeate to outlet chamber 17.

In the embodiment illustrated in Fig. 3, membranes 25 and 28 are rigid. In order to generate the increased hydraulic pressure in each cell 9, each partition element 4 is connected to a membrane by a flexible attachment 21, e.g. an adhesive having elastic characteristics and a highly flexible bondline. The pressure of draw solution D within cell 9 is increased due to the osmosis caused influx of solvent. Since membranes 25 and 28 are rigid and each partition element 4 is connected to a membrane by a flexible attachment 21, the ends 26 of each partition element 4 flex in response to the hydraulic pressure differential between draw solution D and feed solution F or permeate P. The central portion of the partition elements 4 however does not change its configuration since an equal but oppositely directed hydrostatic pressure is applied onto each partition element from the two adjacent cells.

In the embodiment illustrated in Fig. 4, purification unit 20 shown in plan view has a dual membrane section which comprises a plurality of laterally spaced intermediate membranes 24a-c, each of which extends between sidewalls 22 and 23 of the dual membrane section and is substantially parallel to first membrane 5 and second membrane 8. Each of a plurality of transversally spaced partition elements 4, which may be substantially perpendicular to the intermediate membranes 24a-c, extend from first membrane 5 to second membrane 8, defining an array of cells 9. In addition to vertically spaced cells as shown in Fig. 1, the array also comprises a plurality of groups M-P of cells wherein a group is positioned between two adjacent intermediate membranes. Each group of cells includes a plurality of transversally adjacent cells 9 between sidewalls 22 and 23.

There is a concentration gradient of draw agent within cell groups M-P such that the osmotic pressure gradually increases from cell group M to cell group P, to induce flow of the permeate towards outlet chamber 17 as a result of the flow through laterally adjacent cells while increasing filtration efficiency by virtue of the intermediate membranes. The pore size of intermediate membranes 24a-c may be uniform.

It will be appreciated that only one cell group comprising a plurality of transversally adjacent cells for increasing the permeate flux may be provided.

In the embodiment illustrated in Fig. 5, purification unit 30 comprises a conduit 33 in fluid communication with outlet chamber 17 and with a vacuum source 34. Conduit 33 extends from the upper surface 35 of outlet chamber 17 while preventing the passage of permeate P therethrough. Vacuum source 34 may be generated by a vacuum pump 36 as shown, or alternatively, may be generated by oral pressure. When vacuum source 34 is generated, the transport rate between feed solution F and draw solution D, and between draw solution D and permeate P will be considerably increased. The degree to which each cell 9 is expanded as a result of the hydraulic pressure differential will be limited by the presence of the partition elements 4.

Fig. 6 schematically illustrates an apparatus 40 used in conjunction with purification unit 30. Purification unit 30 comprises inlet chamber 6, an inlet conduit 37 leading to inlet chamber 6, outlet chamber 17, dual membrane section 31 interposed between inlet chamber 6 and outlet chamber 17, conduit 33 in fluid communication with both outlet chamber 17 and the vacuum source, and outlet conduit 38 in fluid communication with outlet chamber 17 through which is discharged the permeate produced by purification unit 30. Inlet chamber 6, dual membrane section 31, and outlet chamber 17 are delimited by enclosure 39. Dual membrane section 31, which comprises the first and second semipermeable membranes, the plurality of expandable cells, and the draw agent, as described hereinabove, may be permanently attached to enclosure 39, or alternatively, may be detachable from enclosure 39, e.g. embodied by a replaceable rigid cartridge. Dual membrane section 31 may be proportionally thinner than illustrated.

An unpurified feed solution source 29 is hydraulically connected via pipe 32 to inlet conduit 37. Feed solution source 29 is generally a publicly accessible or naturally found source of unpurified liquid, but also may be a self contained receptacle derived from industrial processes. The feed solution may be free flowing in a steady state from source 29 to inlet conduit 37 and then to outlet conduit 38, whether naturally or by means of a pump, depending on the hydraulic head. Alternatively, the feed solution may be delivered by pulses whereby source 29 is isolated from purification unit 30 after each pulse and the feed solution derived solvent permeates the two membranes by forward osmosis.

As shown in Figs. 7-9, one implementation of the purification unit may be in the form of a hydration bag. Hydration bag 50 comprises an outer bag 52 made from a waterproof and elastic, relatively thick polymeric material. Inlet chamber 56 is located at the upper region of hydration bag 50. An inner bag 59 functioning as the dual membrane section is disposed within outer bag 52. After unpurified water is introduced via inlet conduit 55 and inlet chamber 56 and its solvent is transported osmotically to inner bag 59, fresh water is discharged from the dual membrane section into outlet chamber 61 by means of the hydraulic pressure differential. The fresh water may be consumed by means of a drinking straw 54 protruding from outer bag 52 and in fluid communication with outlet chamber 61. The generation of the fresh water may be accelerated by applying a vacuum with conduit 33 or 60. The dual membrane section may be replaced by means of cartridge 57 via port 58.

Fig. 13 schematically illustrates an embodiment of a hydration bag 80. The outer bag is provided with a liquid impermeable seal line 84, to define an inlet chamber 86 and an outlet chamber 89. After hollow and collapsible inner bag 92 has been inserted within the interior of the outer bag, edge 83 of inner bag 92 facing outlet chamber 89 is attached to seal line 84. Inner bag 92, which may be cylindrical as shown, or may be configured in any other desired fashion, comprises first membrane 85 which is contactable by the liquid in inlet chamber 86 and second membrane 88 facing the interior of the inner bag. A terminal surface 96 of inner bag 92, which is generally indicated by shading in order to illustrate the flow of liquid through hollow interior I into outlet chamber 89, is disposed completely within inlet chamber 86 and spaced from seal line 84 while covering and sealing the hollow interior I of inner bag 92. Partitions 94 extend radially from first membrane 85 to second membrane 88 and extend longitudinally from outlet chamber facing edge 83 to terminal surface 96, to define a plurality of expandable cells 99. The end of interior I facing inlet chamber 86 is sealed with respect to water penetration by virtue of terminal surface 96; however, the end of interior I facing outlet chamber 89 is unobstructed, thereby enabling the flow of permeate to outlet chamber 89.

As the terminal surface of inner bag 92 is sealed, the feed solution F within inlet chamber 86 is forced to be transported osmotically around the entire periphery of, and across, first membrane 85 into the plurality of cells 99. After the plurality of cells 99 expand, fresh water permeates second membrane 88 and is discharged into hollow interior I of inner bag 92 and then to outlet chamber 89 as a result of the increased hydraulic pressure of the draw solution. When hydration bag 80 is positioned such that inlet chamber 86 is above outlet chamber 89, the fresh water permeate P is discharged gravitationally through interior I into outlet chamber 89. When hydration bag 80 is positioned such that inlet chamber 86 is below outlet chamber 89, the fresh water permeate P is discharged into interior I and is supported by the terminal surface of inner bag 92. The fresh water will eventually flow into outlet chamber 89 and able to be consumed after a sufficient amount of permeate P has been discharged. Upon inverting the hydration bag, the entire amount of discharged fresh water can be consumed.

An implementation of hydration bag 80 is illustrated in Figs. 14-15. Fig. 14 illustrates inner bag 92 in a collapsed condition while showing outlet chamber side edge 97 thereof. Fig. 15 illustrates a front view of hydration bag 80 while indicating that seal line 84 is applied at approximately the centerline of outer bag 91.

Another implementation of the purification unit may be in the form of two rigid tanks, as shown in Fig. 10. Purification unit 70 comprises a waterproof base 73. Inlet chamber 76 is positioned on top of base 73, and outlet chamber 77 with an open top is positioned in abutting relation with, and at the same height as, base 73. Base 73, inlet chamber 76, and outlet chamber 77 may all be rectilinear. Cartridge 79 functioning as the dual membrane section is releasably attached to a side of inlet chamber 76 so as to overly, or to be accessible to, and therefore in fluid communication with, outlet chamber 77. Alternatively, cartridge 79 is positioned below inlet chamber 76. The weight of the feed solution will apply a pressure on the dual membrane section, and will cause the permeate to flow to outlet chamber 77, directly or through a channel.

When a sufficient amount of feed solution has been introduced into inlet chamber 76 via inlet conduit 67, the feed solution rises within inlet chamber 76. The feed solution derived solute is transported to cartridge 79 by osmosis, causing the cells thereof to expand and to discharge permeate. The solute separated from the feed solution remains in inlet chamber 76 and is periodically removed. The permeate falls gravitationally to outlet chamber 77.

One suitable application of purification unit 70 is for desalinating seawater while potable water exits outlet chamber 77. A large volume of seawater in inlet chamber 76 can induce a significant difference in osmotic pressure, promoting rapid transport of the feed solution to traffic across the first membrane rapidly without need of a pump. Thus a large volume of potable water may be generated by means of the dual membrane section without need of expensive equipment.

Example 1

In order to estimate the efficacy of the purification unit of the present invention, a test model was employed that had two membranes (220nm pore size) and a chamber which contained the osmotic draw agent (plant fibers— polysaccharides) that generated a force which induced diffusion of the water molecules into the reservoir. The probability test was made during January 2010 in the laboratory of Odis LTD., Israel.

The aims of the probability test were:

1. To estimate the core technology efficacy to generate a force which will overtake the connection forces between the water molecules and the polysaccharides fibers and as well, to push them though the second membrane into the reservoir.

2. The one chamber testing chamber model: Ultra filtration (220nm) purification process with a draw agent based onplant fibers - polysaccharides.

A test was performed to estimate the generated driven force generation within a single chamber. A chamber means: a single space created by the two vertical membranes and the partition elements as the sides walls. The chamber also contained the draw agent. A clear rigid polymer tube was positioned between the two membranes was used to simulate the partition elements, in order to raise the hydraulic pressure within the chamber while preventing a significant membrane swelling.

In order to construct a purification chamber, two membranes (Milipore, Millex®-GV Ο^μιη), made of PVDF and have a pore size of 220nm (Micro- filtration and Ultra-filtration scale) were used. The draw agent was a polysaccharide - Benfiber (Novartis). The draw agent was introduced between the membranes.

All of the components were identical in two systems, with the exception of the draw agent which were present only in the test system. The control system did not contain the draw agent.

Fig. 11 illustrates the test apparatus. The test model was constructed by using two filters (220nm pore size) and polysaccharide fibers between them. The external membrane was integrated within a PVC tube (the dark tube) functioning as the inlet chamber that was connected to the dual membrane section by a conduit. The second membrane (220nm pore size), the internal membrane, was connected to the external membrane. The connection between those membranes creates a channel. Polysaccharide fibers ware inserted in this channel (the clear tube in A.). Prior the insertion of the draw agent, the membranes were moistened by injected water. Unpurified water (B) was inserted into the PVC tube which at the end by the external membrane. Water drop rate was taken in time slides of minutes.

Results

The water drop rate results of the test system (with the draw agent) were: 1. After 10 minutes of purification process: average drop rate was 26 drops/minute.

2. After 20 minutes of purification process: average drop rate was 24.7drops/minute.

3. After 30 minutes of purification process: average drop rate was 23 drops/minute.

4. After 40 minutes of purification process: average drop rate was 21.5drops/minute .

5. After 50 minutes of purification process: average drop rate was 21.8drop s/minute .

6. After 60 minutes of purification process: average drop rate was 22.2 drop s/minute .

The water drop rate results of the control system (without the draw agent) were:

Generation of a single drop was not observed after 15 minutes after the purification process had been initiated.

These results demonstrated the generation of a driven force within the clear tube chamber by the transport of water through the external membrane into the chamber, producing increased hydraulic pressure within the chamber to generate a driven force vector. The driven force vector directed water from the chamber though the internal membrane to the purified water reservoir.

Example 2

Fig. 12 illustrates another test apparatus made mainly by polycarbonate polymer. The driven force chamber was made of a dual membrane (Millipore, the external membrane - catalog number VMWP04700 or VMTP04700) composed of mix cellulose ester (MCE) and had a pore size of 50nm. The internal membrane (Millipore) had a pore size of 450 nm and made of PVDF. The test included 2 identical modules such that the first system- the control- was not provided with any draw agent and between the membranes of the second system- the test model- was introduced the draw agent. The draw agent was selected from glucose, dextrose, trehalose, sucrose, cellulose and CaC . The inlet chamber was the upper chamber and the outlet chamber was positioned below the dual membrane section.

The flow of filtrated water was recorded in time intervals of 15 minutes (filtrated volume). The results are summarized in Table 1.

The same test apparatus and draw agents can be used, with the addition of the application of a vacuum in the lower chamber.

From the results of this study and of Table 1, it can be concluded that:

1. The structure and material of the membrane affects the filtration rate of the water. Membrane type A (Membrane 50 nm, Millipore, VNWPO4700), provides a better water filtration flow rate then Membrane type B (Membrane 50 nm, Millipore, VMTP04700).

2. Different types of draw solutions provide a different purification rate.

3. The filtration rate (in both membrane types) of the water when glucose was used as the draw agent was more rapid than with respect to the control module (without the draw agent). Similar results were observed when Dextrose and Trehalose were used as the draw agent.

4. Membrane type A (VNWPO4700) provided the best filtration results when Glucose was used as the draw agent. After 1 hour of filtration, the dual membrane section having a surface area of approximately 12mm ² filtrated 3.5 ml of water in comparison to the control module which provided an average filtration volume of 2.6 ml.

5. Hygroscopic draw agents such as silica gel and CaC12 were also used. The Table 1

Time Control CelluTrehalose Sucrose Glucose Dextrose (min) lose

Membra B B A A A B B A B B B ne type

15 min O ml Oml 0.1 ml 0.5 ml 1.1ml 0.1 ml 0.5ml

30 min 0 ml 0 ml 0.15 ml 1.15 ml 1.8 ml 0.2 ml 0.8ml 45 min 0 ml Oml 0.2 ml 1.2 ml 2.9 ml 0.25 ml 0.9ml

270 min

285 min results (not presented) indicate that an improvement in the water filtration flow results can be achieved by introducing a sugar/polysaccharide or salt with the hygroscopic draw agent.

6. It is foreseen that the application of a vacuum at the outlet chamber will accelerate the filtration process.

While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried out with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without departing from the spirit of the invention or exceeding the scope of the claims.