GB2458184A

GB2458184A - Apparatus for the generation of purified water

Info

Publication number: GB2458184A
Application number: GB0804437A
Authority: GB
Inventors: Philip Peter Monro
Original assignee: Hampshire Advisory and Technical Services Ltd
Current assignee: Hampshire Advisory and Technical Services Ltd
Priority date: 2008-03-11
Filing date: 2008-03-11
Publication date: 2009-09-16
Also published as: GB0804437D0; WO2009112816A1

Abstract

Apparatus for the generation of purified water comprises; a container 1 which comprises at least one primary and secondary selectively permeable membranes 2 and 3, which will exclude pathogens. The primary membrane will also selectively retain a substance for promoting osmosis 5, which may be sodium chloride. A method of use is also provided which comprises water from a contaminated water source 9 being drawn into the container through a membrane 2 from a flow tray 8 by the sodium chloride crystals 5 forming saline solution, the container is inverted so the saline solution contacts a sodium chloride selectively permeable membrane 3 and the sodium chloride passes into the contaminated water feed. The potable water can then be removed through a port 6, which has a removable cover 7.

Description

Apparatus for the generation of purified water

Description

The present invention relates to a water purifying container and methods of using such a container. In particular, the present invention relates to a container having at least two selectively permeable membranes located in different regions of the container, both of which will exclude pathogens but only one will retain a rehydration driver. By pre-loading the apparatus with rehydration driver and initially contacting an external contaminated water supply with that membrane that excludes the driver a dilute pathogen free solution is generated. If the external water supply is then placed in contact with the membrane that is porous to the dissolved rehydration driver its concentration is significantly reduced and so generates purified water within the container.

Note: In all the following examples where there are proposals and designs where there are proposed mechanisms and or procedures for changing or alternating between the salt excluding membrane and the salt releasing membrane being in contact with the external water supply those skilled in the art will be aware that the same effect will result if, where appropriate contact with or between the external water supply is alternated or reversed.

Such a container has applications in the many parts of the world, where supplies of clean water arc not always readily available and may contain harmful substances including pathogenic organisms. Conventional apparatus for providing potable water from a contaminated source is often complicated, expensive and not easily transportable. Our expectation is that if food grade sodium chloride is used as the rehydration driver, potable water can be generated at low cost from a highly contaminated water supply. The present invention is intended to provide such potable using a relatively simple apparatus that is easy and efficient to use and inexpensive to manufacture and to deploy in areas of need. Using materials and rehydration drivers of an appropriate quality the same technology can be used to provide water of higher purity and free from toxins and pyrogens.

The container can be any receptacle suitable for holding a rehydration driver to be dissipated and may be of a variety of possible shapes, including cubic, cuboidal, spherical, cylindrical, conical, pyramidal, and so forth. The inside of the container may be predominantly hollow and may be partitioned into one or more different chambers or compartments. In an embodiment, the container comprises a single compartment with a rehydration driver contained therein. The container can be fabricated from any suitable material, including quartz, glass, leather, wood, metal, ceramic, and natural or synthetic polymers. In an embodiment, the container is fabricated from a recyclable material, such as a regenerated cellulose film. In another embodiment, the container is made from a lightweight plastics material for case of manufacture and transportation. In yet another embodiment, the container is of rigid or semi-rigid construction, so that it is at least partly self-supporting in use. The selectively permeable membranes will generally be located in or form part of a surface of the container, although this is not essential. In an embodiment, the container is in the form of a rigid or semi-rigid box and, in this case, the selectively permeable membrane may form one or more sides or walls of the box, preferably opposite sides or walls of the box. The other walls of the box may be constructed of any suitable non-permeable material, such as a non-permeable cardboard or paper, a non-permeable polyurethane, polysuiphone, polysulphide, phenolic resin, silicone, polyolcfin, polyvinyl resin, polyester resin, nitrogen polymer or polyether, although their exact composition is not critical as long as they are not permeable to water or to the con tents of the container. In an embodiment, the walls of the container are constructed of a suitable grade of a polyolefin, such as polythene. The container may be manufactured to a standard or grade suitable for the intended application of the composition or for the conditions in which the container will be used. In an embodiment, the container is manufactured to a standard that allows rehydration of the rehydration driver to take place under conditions that ensure that it is sterile and pathogen or pyrogen free. This is especially important in the case of a composition intended, for example, for intravenous (TV) administration. In an embodiment, the container is manufactured from materials that render some or all of it biodegradable, preferably as much, of the container as possible. In this case, the materials will generally be organic matter, such as plant or animal matter or other matter originating from living organisms or manufactured from plastics specifically formulated and or fabricated to achieve that result.

The composition inside the container can be any single substance, mixtures of substances or compound capable of generating a osmotic pressure. The composition may be in the form of a solid or solution, preferably a concentrated solution. In the context of the present invention, the term "solid" should be understood to include a powder, a particulate, a gel, or any combination thereof. In an embodiment, the composition to be rehydrated is in the form of a hydro-gel.

In one embodiment, any combination of rehydration agents of a quality and purity are used, to provide a supply of potable water. In others, using membranes of appropriate exclusion characteristics and the container of compatible standard together with rehydration drivers of a higher quality water can enable the generated water to a standard required for more stringent applications. By way of example for the rehydration or reconstitution of a medicinal or a pharmaceutical product, a drug or a dried blood or blood product, or a blood or blood fraction substitute.

Alternatively, for rehydration of specific pathogen free (SPF) products selected from the group consisting of oral products, oral drugs, oral rehydration salts or solutions (ORS), simple medicines, intravenous (IV) solutions, topical products, attenuated live vaccines, cytotoxic drugs and unstable industrial products. Thus, the water so generated according to the present invention can be used for rehydrating a wide range of different products, such as any living plant or animal species, including bacteria, viruses and phages, any isolated eggs, embryos and seeds or dormant forms of such species, and any living or dead fractions of such species. In particular, the resulting product may be used, without limitation, for: the hydration of any component or fraction of whole blood from any human or non-human animal; the rehydration of any dry component of any artificial whole blood or artificial blood fraction for administration to any human or non-human animal; the rehydration of dried living but inert food species, such as, for example, the living component of yoghurts and those food types classed as "probiotic"; the rehydration of living but dormant species used for agricultural purposes, which include silage or compost generating species; the rehydration of any dry component of any dried food intended for consumption by any human or non-human animal; the rehydration of the dry component of any labile product classed as medicine for human or non-human administration by any route within the definitions of the medicines and veterinarian acts of any country, such as, for example, live attenuated oral vaccines; the rehydration of any dried and/or inactivated and/or attenuated live micro-organism of use in any medical, veterinarian, agricultural, or horticultural, food processing or industrial process; the rehydration of any dried and/or inactivated and/or attenuated live cell, or cellular or tissue or organ fraction used in any medical or veterinarian treatment or application; the rehydration of any dried and/or inactivated and/or attenuated donor (or the recipient's own) cells, tissues or organs of use in any medical or veterinarian treatment or application; the rehydration of any dry component of material used for any human or veterinarian test, assay or diagnostic assay; and the rehydration of potentially harmful or toxic materials, including category 4 organisms such as smallpox, wherein the material that is being rehydrated is enclosed behind a specific pathogen retaining first membrane to protect the material from external contamination or for reasons of human or non-human safety.

In the above examples of items that can be rehydration the container can be fabricated so that, that which is to be rehydrated are located in an isolated and / or separate region of the container and so rehydration only takes place once the mass or concentration of the temporary rehydration driver has been adequately reduced.

The preferred mode of action water generation is by osmosis but this is non-limiting example and so water generation by other modes of action including by pervaporation (PV), arc also possible. Osmosis is the process of diffusion of a solvent, generally water, through a selectively permeable membrane from a place of lower solute concentratiob to a place of higher solute concentration (i.e., from a region of low osmotic pressure to a region of high osmotic pressure).

l'ervaporation involves molecules permeating through a selectively permeable membrane in the vapour phase. In an embodiment, the rehydration driver is an osmotic agent that is capable of increasing the rate of diffusion of a solvent across a selectively permeable membrane by creating an osmotic potential across the membrane. The rehydration driver vil1 generally be a low molecular weight compound, such as an inorganic or organic salt, like sodium or potassium chloride, or a sugar of low molecular weight, such as glucose or fructose. In an embodiment, the rchydration driver includes at least one hygroscopic component, such as glycerine. In this embodiment, the hygroscopic component may be a deliquescent component, such as calcium chloride. In yet another embodiment, the rehydration driver is a compound capable of generating or maintaining a substantially constant osmotic pressure within the container during rehydration. In this embodiment, the rehydration driver may be an osmotic buffer, such as a poorly dissociated salt of a weak organic acid or base, such as trisodium citrate. In another embodiment, the rehydration driver i-nay be fixed or coated on at least a portion of the selectively permeable membrane. In this embodiment, composition or driver may be fixed or coated on a region of the selectively permeable membrane that is not directly in contact with a rehydration solvent.

In the context of the invention, a selectively permeable membrane, which is also termed a semi-permeable membrane, is a membrane that allows passage of certain substances through it but restricts the passage of other substances. That is to say, the membrane is porous to certain substances but not to others, generally as a result of the pore size of the membrane and the size and shape of the molecules concerned, although it may also depend upon how a particular solute or a solvent interacts with a specific membrane. In an embodiment, the selectively permeable membrane(s) is a flexible membrane. However, this is not essential and a rigid, semi-rigid or stiff selectively permeable membrane may be equally useful. Suitable selectively permeable membranes can be obtained, for example, from Koch Membrane Systems, Inc., 850 Main Street, Wilmington, Massachusetts, United States of America, who manufacture a range of membranes of differing degrees of porosity. Such membranes are graded in terms of their general ability to exclude bacteria and suspended solids whilst allowing passage of water, monovalent ions, multivalent ions and viruses (microfiltration or MF membrane); to exclude viruses, bacteria and suspended solids whilst allowing passage of water, monovalent ions and multivalent ions (ultrafiltration or UF membrane); to exclude most multivalent ions and viruses, bacteria and suspended solids whilst allowing passage of water and monovalent ions (nanofiltration or NF membrane); and to exclude monovalent ions, multivalent ions, viruses, bacteria and suspended solids whilst allowing passage of water (reverse osmosis or RO membrane). Thus, for example, a nanofiltration membrane that can be used for softening water may reject 85% of salt (sodium chloride) but 99% of the hardness ions (calcium and magnesium), whilst the highest salt rejection rates (99.7% or higher), which can be provided by reverse osmosis membranes, are required for seawater desalination. A pore reducing coating may be applied to the membrane in order to generate the desired degree of porosity. Such a coating may have the additional benefit of enhancing the physical integrity of the membrane by covering any minute defects, fissures or tears in the membrane, thereby improving its solute exclusion or retention properties. Alternatively, the container may comprise one or more layers of the selectively permeable membrane, such that any random defect present in one layer of the membrane is compensated for by a defect-free region of an immediately adjacent membrane. In this case, the layers of the selectively permeable membrane may be fused or heat-sealed to one another, so as to maintain them in close proximity. Such coated or laminated membranes are generally found to have an enhanced integrity relative to membranes that have not been coated or are not present as laminates, such that the incidence of leakage or rupture is substantially decreased, often by at least 50%, preferably 70%, and most preferably over 80%. The selectively permeable membrane or membranes may be present in the container as a flat sheet or layer or may be suitably folded so as to maximize its available surface area. In an embodiment, the membrane is a sinusoidal curved membrane, although other arrangements may be found to be equally effective, for example as a cartridge to maximise surface area in a restricted space. In an embodiment, the membrane is made from a polyurethane, such as a solid vapour transmitting membrane of the type classed as a P4 membrane by its manufacturers PIL Membranes� of King Lynn, Norfolk, England. The selectively permeable membrane may also be treated to enhance or alter its physical or chemical properties in other ways. The selectively permeable membrane could be treated, for example, so as to render it more hydrophilic or hydrophobic, or so as to render it more lipophilic or lipophobic, or so as to increase its effective surface area.

Such properties could be imparted by coating the membrane with suitable substances, for example, or could be introduced at a molecular level during manufacture of the membrane, for example, by polymerising monomers containing charged groups. In an embodiment, the selectively permeable membrane is coated with a layer of a substance that is capable of inactivating potential toxins or killing pathogenic micro-organisms. For example, the selectively permeable membrane may be coated with a porous thin film of titanium dioxide, so as to absorb malodorous substances, harmful substances in the air such as NO or SO, or environmentally polluting organic chemicals dissolved in water such as organic solvents and agricultural pesticides. In this case, electrons and positive holes are generated in the thin film of titanium oxide when it is exposed to sunlight or artificial light, and the oxidizing-reducing activity of the electrons and positive holes quickly and continuously decomposes and removes the adsorbate. Since this photocatalyst simply requires exposure to light, it operates inexpensively, consumes little energy, and does not require maintenance. When this film of titanium oxide is coated with a metallic film such as of platinum, rhodium, ruthenium, palladium, silver, copper, iron, or zinc, Its performance in decomposing and removing the adsorbed organic compounds by catalytic activity is further enhanced. In this case, since the thin film of titanium oxide is porous, the metal disperses smoothly in the thin film and coats the photocatalyst. As a result, the metal is able to manifest its catalytic activity with particularly high effect.

Dissipation of the driver from the container refers to the loss of the majority of rehydration driver remaining after liquid has been generated within the container.

This includes losses of rehydration driver from the container by simple equilibration or diffusion processes. In an embodiment, the composition within the container is substantially free of driver after dissipation has taken place, such that at least 75%, 80%, 85%, 90%, 95% or 100% of the amount of driver originally present in the composition prior to rehydration is lost following this stage.

In the preferred embodiment, the container comprises a first selectively permeable membrane that substantially excludes passage of the driver and a second selectively permeable membrane that substantially permits passage of the driver. In this context, a membrane that substantially excludes passage of the driver means the selectively permeable membrane has greater permeability to solvent than to the driver, so that solvent may pass more freely across the membrane, whereas the passage of the driver is greatly hindered or even entirely prevented. Also, a membrane that substantially permits passage of the driver means the selectively permeable membrane is highly permeable to the driver, such that most, if not all, of the driver is able to pass freely across the membrane. It will be appreciated by those skilled in the art that multiple static rinses of a fixed volume of solvent or an optimised flow of a thin film of solvent across the exterior surface of the secondary membrane can bc used to remove a significant proportion of the dissolved driver with a minimum mass of solvent. The first and/or second selectively permeable membrane may be isolatable from a rehydration source in contact with the first and/or second selectively permeable membrane.

In a preferred embodiment, the first and second selectively permeable membranes are located in or form different regions of the container, such that they can be physically isolated from each other during rehydration and dissipation. The container may include a selectively permeable membrane that has a low molecular weight exclusion limit, such that the membrane substantially excludes simple inorganic salts, such as sodium chloride. For example, the container may include a first selectively permeable membrane that is a reverse osmosis membrane of the kind obtainable from Koch Membrane Systems, Inc., 850 Main Street, Wilmington, Massachusetts, United States of America. Such a container has the further advantage that it could be used, for example, to generate solvent using a brackish sourcc of water for the initial rehydration step.

In other embodiments of the invention, the first and/or second selectively permeable membrane is a specific pathogen excluding membrane. Containers comprising specific pathogen excluding membranes may be used to generate liquids that are specific pathogen free. In the context of the invention, the term specific pathogen free (which may be abbreviated to SPF) may include an environment free not only of specific pathogens, such as parasitic nematodes, protozoa, bacteria and prions, but also of specific toxins and toxic substances having molecular weights above the specific exclusion point (cut-off point) of the selectively permeable or semi-permeable membrane. However, it must be understood that the precise meaning of the term SPF is dependent on the intended purpose of the rehydrated composition and, thus, may vary in different circumstances. For example, certain pathogens' may be present in water that is suitable and safe for drinking which could not be included in a composition for intravenous administration to a patient.

It will be appreciated by those skilled in the art that, as the effective pore size of a selectively permeable membrane is reduced, the possibility of blocking and or fouling the membrane by contaminants present in a water source is increased. Such a consideration may be of particular importance in the case of selectively permeable membranes that are specific microscopic pathogen excluding, although this will also depend upon the quality of the water source available for rehydration and the manner in which this is carried out. Containers in accordance with the present invention may incorporate devices and/or procedures to minimise these concerns and, by way of example only, may include pre-filters or anti-fouling chemicals, or may be used in conjunction with parallel devices that effect precipitation or flocculation of any insoluble or colloidal material present in a water source. In addition any such physical filters and membranes may be protected internally and or externally by for example protective grids.

The container may be a discrete, portable unit that can be easily transported to areas of sudden need, such as, for example, in the case of a naturally occurring disaster.

In such circumstances, the container may be designed to be disposable after a single use. In an embodiment, the container is manufactured from materials that render some or all of it biodegradable, so as to minimize further contamination of the environment. In an alternative embodiment, the container may be designed for continuous or repeated used, so as, for example, to ensure that a continuous supply of potable drinking water is available. In the latter case, the container may be of a relatively large or robust construction. The container may also include anti-fouling or blocking means of the kind described above or, for repeat cycles, may be operated to include a step of back-flushing a solvent across the membrane, so as to remove any trapped particles or deposits and ensure that acceptable rates of rehydration can be maintained. In an embodiment, the container further comprises a reservoir for a source of water for rehydration of the composition, the reservoir -10 -being separated from the composition by the first selectively permeable membrane.

In another embodiment, the container further comprises a reservoir for a source of water for dissipation of the driver, the reservoir being separated from the composition by the second selectively permeable membrane. In the aforementioned embodiments, the reservoir may be an open or sealed chamber provided with independent supply means for ingress or egress of a water source. In an embodiment, the reservoir is adapted to allow the water source to contact the first or the second selectively-permeable membrane continuously, such that rchydration or dissipation of the driver is driven to completion as rapidly as possible. In this and other embodiments of the invention, the rate of rehydration may be further increased by pumping of a water source across the membrane. This may be particularly appropriate where, for example, potable drinking water is required as a matter of urgency. Where a natural power source, such as the wind or sun, is available, this can be used as a source of energy to drive an electric pump or, where appropriate, the moving parts directly. Similarly, natural forces, such as gravity, can be exploited for the same purpose. In another embodiment, the reservoir is adapted to allow the water source to contact the first or the second selectively-permeable membrane periodically. Such an arrangement is useful when the container is intended to be used repeatedly, such as, for example, to provide a source of clean water at specified periods of the day after a complete rehydration and dissipation cycle. In a further embodiment, the reservoir is adapted to allow the water source in contact with the first or the second selectively-permeable membrane to be -recycled, which may be desirable for practical reasons, such as a limited supply of dirty water, or for environmental reasons. In yet a further embodiment, the container is adapted to allow a single rehydration and dissipation cycle.

In an embodiment, the container is adapted to allow a continuous rehydration and dissipation cycle. In an alternative embodiment, the container is adapted to allow multiple rehydration and dissipation cycles. In these embodiments, the container may be provided with means for introducing rehydration driver into the container, preferably under sterile conditions or as close to such conditions as is achievable under the circumstances. Alternatively, the container may be provided with means for introducing rchydration driver under conditions that are specific pathogen free -11 - (SPF) with respect to the intended USC of the rehydrated composition. This allows the container to be repeatedly or continually topped up with driver as it becomes depleted following rehydration and dissipation. In another embodiment, the container further comprises a sump, for retaining at least a portion of the s rehydration driver or a concentrated solution thereof within the container. Such an arrangement is particularly useful when the container is intended to be used repeatedly, as it ensures that there is always a ready supply of driver or a concentrated solution thereof available to commence the next rehydration and dissipation cycle. In a further embodiment, the container also comprises means for removIng rehydrated composition from the container under sterile or substantially sterile conditions. In yet a further embodiment, the container also comprises a compartment for allowing Continuous access to rehydrated product. In this last embodiment, the container may also comprise means that concurrently allow independent rehydration of a separate source of rehydration driver. In another embodiment, two or more containers may be linked together, for example, so as to prepare a composition of increasing or decreasing solute concentration. Further there could be one or more further linked containers where the completed product is stored and from where it is dispensed from.

In cases where assessment of sterility is important, such as, for example, where the container is to be used to prepare sterile solutions for intravenous administration, the container may further comprise or be used in conjunction with suitable indicators to confirm sterility or physical integrity of the system and independently means to validate the integrity of the container and its contents prior to rehydration, after rehydration has been completed and prior to use of the generated solvent.

The container may be constructed from materials that are capable of being sterilized, for example, by heat treatment, gamma irradiation, ionisation, ozonation or chlorination. Such a container can, thus, be sterilized so as to ensure that the interior of the container does not contain any harmful pathogens.

For certain applications, it may be important to ensure there is a visual indication that an intended volume of solvent is present in a particular chamber or compartment of the container. For example, this could be indicated by including a -12- "fill line" on the container. Alternatively, such a result could be achieved by ensuring that the volume of one or more particular compartments is limited and cannot be exceeded, or by only allowing access to a limited volume of rehydration solvent. For those skilled in the art, it will be apparent that it may be advantageous to incorporate in the product a visual and/or chemical indicator of a specific "end-point" to a process, such as, for example, that the solution has diluted to the required degree. Such indicators could be in the form of electrical test equipment or also be present as a solute or solvent, on thc opposite side of the selectively permeable membrane to the composition to be rehydrated. /0

In a further embodiment, any selectively permeable membrane can be present as a laminate with a permeable support layer. The permeable support layer has a porosity that is greater than that of the selectively permeable membrane, such that the porosity of the selectively permeable membrane is the rate determining factor in rehydration or dehydration. The support layer provides additional rigidity and strength to the selectively permeable membrane. The permeable support layer may be located on the side of the selectively permeable membrane in contact with the contents of the second compartment. In the case where the water source in the second compartment is muddy water, for example, the support layer can also help to prevent the selectively permeable membrane from becoming clogged and thus, can help to maintain an acceptable rate of rehydration or dissipation of rehydration driver. In another embodiment, the selectively permeable layer is sandwiched between two permeable support layers. This arrangement provides further protection against mechanical damage or tearing of the selectively permeable membrane during manufacture, storage, transportation or use of the container. It will be appreciated that such forms of protecting the selectively permeable membrane against physical damage or clogging are equally applicable to all embodiments where they can be applied to. The container may be supplied with the rchydrauon driver already in place, though this is not essential. This includes the use of selectively permeable membrane wherein the membrane has been doped with a rehydration driver. Such an arrangement ensures intimate contact between the driver and the membrane during the critical early stages of rehydration, thereby ensuring efficient uptake of a water source. In an embodiment, a surface of the -13 - membrane is coated with the driver. In this case, a driver may be applied to a pre-formed or commercially available selectively permeable membrane and in a manner best suited to the intended application.

For example, the driver can be applied to the selectively permeable membrane after the container has been assembled and in a manner that ensures that the SPF status of the container is not compromised. In a further embodiment, the driver is present in a sponge layer or open mesh layer on the surface. In a yet further embodiment, the driver is present in admixture with an adhesive. In this last embodiment, the adhesive may be a water-soluble adhesive, such as, for example, an edible compound that has adhesive properties until it makes contact with water. Once again, it will be appreciated by those skilled in the art that such doped membranes may be uscd in any of the various aspects of the invention described herein. Such membranes may also be treated with indicators or anti-microbial substances or toxin-reducing agents, so as to verify or maintain the integrity of the contents and external surfaces of the container in accordance with any of the techniques or methods previously described. The selectively permeable membranes in accordance with this aspect of the invention can be used in a wide range of applications, including, without limitation, humanitarian, medicinal and industrial applications.

In order that the invention and its attendant advantages may be better understood, it will now be described in relation to a number of exemplary embodiments thereof, with reference to the accompanying drawings, wherein: Figure 1 shows a cross-sectional view of a container in accordance with a first aspect of the invention; Figure 2 shows a cross-sectional view of the container of Figure 1 in use, during rehydration: Figure 3 shows a cross-sectional view of the container of Figure 1 in use, during salt dissipation; Figure 4 shows a cross-sectional view of the container of Figure 1 in use, during sampling of the rehydrated composition; -14 -Figure 5 shows a cross-sectional view of a container having additional water reservoirs in accordance with a second aspect of the invention; Figure 6 shows a cross-sectional view of a container having additional water reservoirs and a sump in accordance with a first aspect of the invention; Figure 7 shows a cross-sectional view of a container having additional water reservoirs, a surnp and a septum in accordance with a first aspect of the invention; Figure 8 shows a perspective view of cylindrical container with a third aspect of the invention and with additional components intended to give improved physical protection to the selectively permeable membranes and reduce the incidence of them being occluded by particulate matter.

Figure 9 shows a perspective view of a cylindrical container capable of being dismantled and compressed for the purpose of ease of transportation and storage and then being assembled at the location where it is to be used.

Figure 10 shows a variation of figure 9 where the rigidity required for optimum use is achieved by inflation of integrated regions of the flexible sleeve.

Figure 11 shows the sequence of actions and positions that are involved in generating water of improved quality.

Figure 12 shows a perspective view of a cylindrical container capable of being pivoted at its fulcrum and floated Out over water to facilitate its use.

Figure 13 shows a perspective view of a cylindrical container shaped to facilitate self-inversion once a certain mass of water accumulates within the container.

Figure 14 shows a perspective view of a container shaped to enhance the speed of self-inversion, once a certain mass of water accumulates within the container.

Figure 15 shows a cross-sectional view of a container in accordance with a fourth aspect of the invention and shows a cross-sectional view of a multi-compartment container that facilitates concurrent water up-take, salt dissipation and water storage.

Figure 16 shows the sequence of stages that occur in a multi-compartment container that facilitates concurrent water up-take, salt dissipation and water storage.

Figure 17 shows a cross-sectional view of a container in accordance with a fifth aspect of the invention and shows a cross sectional view of a container designed for the repeat external deliver of the rehydration driver as a concentrated solution. -15-

Figure 1 8 shows a cross sectional view of a container designed for the repeat deliver of predetermined masses of rehydration driver, preloaded into the container.

In Figure 1, a container (1) accordance with a first aspect of the invention is in the form of an "osmotic box", a first selectively permeable membrane (2) that excludes a rehydration driver and a second selectively permeable membrane (3) that allows passage of the rehydration driver, forming opposite side walls of the box (1). The first and second selectively permeable membranes (2, 3) arc both specific pathogen excluding membranes. The remaining side walls (4) of the box (1) are formed of non-permeable polyurethane. The box (1) contains crystals of anhydrous sodium chloride (5) as a rehydration driver. The box (I) has a water-tight consumption port (6) for gaining access to its contents, port (6) being protected by a removable cover (7) when not in use. The box (1) is located with rehydration driver excluding membrane (2) face down in a flow tray (8). In Figure 2, a contaminated external water source (9) flows through the flow tray (8) and water is drawn therefrom into the box (1) through rehydration driver excluding membrane (2) by osmosis due to higher osmotic pressure within the box (1) generated by sodium chloride crystals (5), which dissolve to form a concentrated SPF saline solution within the box (1).

The contaminated water source (9) in flow tray (8) is fed across the face of membrane (2) to maximize the rate of osmosis across membrane (2). In Figure 3, the box (1) has been inverted and the rehydration driver permeable selectively permeable membrane (3) is now face down in flow tray (8), 50 that sodium chloride in the SI'F saline solution within box (1) is allowed to dissipate by passing through rehydration driver permeable membrane (3) into contaminated water source (9). In Figure 4, dissipation of sodium chloride is complete and box (1) containing SPF water is tilted to allow sampling of potable water through port (6) following removal of removable cover (7).

In Figure 5, a container (10) in accordance with a second aspect of the invention, for continuous or repeated use, comprises a central compartment (11), a first selectively permeable membrane (12) that excludes an rehydration driver and a second selectively permeable membrane (13) that allows passage of the rehydration driver forming opposite side walls of the central compartment (11). Central -16 -compartment (11) is flanked on one side by a first reservoir compartment (14) for a water source for rehydrating a composition in central compartment (11), central compartment (11) and reservoir compartment (14) being separated by the rehydration driver excluding membrane (12). On an opposite side, central compartment (11) is flanked by a second reservoir compartment (15) for containing a water source for dissipating rehydration driver present in a composition in central compartment (11), central compartment (11) and reservoir (15) being separated by rehydration driver permeable membrane (13). Reservoir compartments (14, 15) arc each provided with a water inlet (16) and a water outlet (17), the rate of flow of water through the reservoir compartments (14, 15) being controlled by a tap (18).

Central compartment (11) is also provided with an inlet (19) for introduction of SPF rehydration driver, inlet (19) being protected by a removable lid (20), and an outlet (21) for collection of SPF solution from the central compartment (11), the outlet (21) comprising valve means (22) to ensure integrity of the SPF system inside central compartment (11). In use, after ensuring that tap (18) in the second reservoir compartment (15) is closed, tap (18) in the first reservoir compartment (14) is opened to allow water to flow through inlet (16) and into contact with rehydration driver excluding membrane (12) and through outlet (17). Rehydration driver in a composition in central compartment (11) induces passage of water across membrane (12) by osmosis, to form an SPF driver-containing solution inside central otnpartment (ii). Once the composition has been rehydrated, tap (18) in the first reservoir compartment (14) is closed and tap (18) in the second reservoir compartment (15) is opened to allow water to flow through inlet (16) and into contact with membrane allowing passage of the driver (15) and through outlet (17).

Rehydration driver in rehydration driver-containing Sl'F solution in central compartment (11) is dissipated across membrane (15), leaving rehydration driver reduced SPF solution in central compartment (11). SPF solution can be sampled via outlet (21) by opening valve (22). For further cycles, fresh SPF rehydration driver can be added via inlet (19) after removal of lid (20).

In Figure 6, a container (23) in accordance with a second aspect of the invention, for continuous or repeated use, comprises a central compartment (24), a first selectively permeable membrane (25) that excludes an rehydration driver and a -17-second selectively permeable membrane (26) that allows passage of the rehydration driver, forming opposite side walls of the central compartment (24). Central compartment (24) is flanked on one side by a reservoir compartment (27) for containing a water source for rehydrating a composition in the central compartment (24), central compartment (24) and reservoir compartment (27) being separated by the rehydration driver excluding membrane (25). On an opposite side, central compartment (24) is flanked by a reservoir compartment (28) for containing a water source for dissipating rehydration driver present in a composition in the central compartment (24), central compartment (24) and reservoir compartment (28) being separated by the rehydration driver permeable membrane (26). Reservoir compartments (27, 28) are each provided with a water inlet (29) and a water outlet (30), the flow of water through the reservoir compartments (27, 28) being controlled by a tap (31). Central compartment (24) is also provided with an inlet (32) for introduction of SPF rehydration driver, inlet (32) being protected by a removable lid (33), and an outlet (34) for collection of SPF solution from the central compartment (24), the outlet (34) comprising valve means (35) to ensure integrity of the SPF system inside central compartment (24). The central compartment (24) is also provided with a septum (36) which partially divides the central compartment (24) into two regions, a rehydration region (37) and a dissipation region (38). In use, rehydration driver-containing SPF solution is generated essentially as described above in relation to Figure 5. However, excess rehydration driver-containing SPF solution passes over septum (36) into dissipation region (38) of central compartment (24), where it can be processed for dissipation of rehydration driver and pure S]F solution sampled via outlet (34). A reserve of rehydrauon driver-containing SPF solution remains in rehydration region (37) of central compartment (24), for future rehydration-dissipation cycles.

In Figure 7, a container (39) in accordance with a second aspect of the invention, for continuous or repeated use, comprises a central compartment (40), a first selectively permeable membrane (41) that excludes an rehydration driver and a second selectively permeable membrane (42) that allows passage of the rehydration driver, forming opposite side walls of the central compartment (40). Central compartment (40) is flanked on one side by a reservoir compartment (43) for containing a water source for rehydrating a composition in the central compartment -18- (40), central compartment (40) and reservoir compartment (43) being separated by the rehydration driver excluding membrane (41). On an opposite side, central compartment (40) is flanked by a reservoir compartment (44) for containing a water source for dissipating rehydration driver present in a composition in the central compartment (40), central compartment (40) and reservoir compartment (44) being separated by the rehydration driver permeable membrane (42). Reservoir compartments (43, 44) are each provided with a water inlet (45) and a water outlet (46), the flow of water through the reservoir compartments (45, 46) being controlled by a tap (47). Central compartment (40) is also provided with an inlet (48) for introduction of SPF rehydration driver, inlet (48) being protected by a removable lid (49), and an outlet (50) for collection of SPF solution from the central compartment (40), the outlet (50) comprising valve means (51) to ensure integrity of the SPF system inside central compartment (40). The central compartment (40) is also provided with a septum (52) which partially divides the central compartment (40) Into two regions, a rehydration region (53) and a dissipation region (54), and a sump (55). In use, rehydration driver-containing SPF solution is generated and subjected to dissipation essentially as described above in relation to Figures 5 and 6.

However, the sump (55) below the level of membrane (41) ensures that a residual amount of rehydration driver always remains present in the system as a solution.

In Figure 8, a container (56) in accordance with a third aspect of the invention is in the form of a cylinder, comprising a first selectively permeable membrane (57) that excludes an rehydration driver and a second selectively permeable membrane (58) that allows passage of the rehydration driver, forming opposite ends of the cylinder (59). The first and second selectively permeable membranes (57, 58) arc both specific pathogen excluding membranes. The side walls of the cylinder are formed of rigid non-rusting / salt-resisting metal or materials that can protected from such effects. The cylinder (56) contains crystals of anhydrous sodium chloride (60) as an rchydration driver. The cylinder (56) has a water-tight consumption port (61) for 3o gaining access to its contents, this port (61) being protected by a removable cover (62) when not in use. The cylinder (56) has a water-tight access port (63) for adding defined masses of rehydration driver, being protected by a removable cover (64) when not in use. In use the cylinder (56) is initially located with rehydration -19-driver excluding membrane (57) face down in either flowing water or a relatively large volume of a static water source that can flow tangcntally across the external surface of either of the selectively permeable membranes. Both selectively permeable membranes are recessed in their framework. External to both the sealed in selectively permeable membranes, are removable pre-filters (65) whose removal, does nor compromise the SPF security of the cylinder. External to the pre-filters are removable protective screens (66) designed to minimise damage to the filters below. The cylinder is rnountcd on pivots (67) at as near as is practical to the centre of gravity of the empty cylinder so that it can be rotated around this axis to allow either selectively permeable membrane to be in contact with the external water source with the minimum of physical exertion. Alternatively it can be positioned horizontally to facilitate the addition of fresh rehydration driver and alternatively collection of the purified water. Further the location of the fulcrum and dimensions of the cylinder are such that either selectively permeable membrane can be submerged to an optimum depth in the external water supply.

In Figure 9, a container (68) accordance with a third aspect of the invention is in the form of a cylinder whose design is intended to facilitate its transport and storage.

The walls of the cylinder (69) are formed of flexible impervious strong welded plastic or rubber capable of being collapsed and compressed into a small space while being transported or stored but containing the similar ports for the addition of rehydration drivers and removal of the contents of that container described in Figure 8. This flexible sleeve (69) can either be permanently welded to the framework holding the selectively permeable membranes or can be temporarily separated from these during storage and transportation and then reassembled and sealed into place using an SPF excluding fixing device (70). In operation the cylinder is restored to its original shape by means of bracing rods (71) that are inserted into recesses (not shown) external to the selectively permeable membranes.

In Figure 10, a container (72), similar in purpose to that described in Figure 9 and in accordance with a third aspect of the invention, is in the form of a cylinder whosc design is intended to facilitate its transport and storage and where Its required shape when is use can be established by means of inflation of built in inflatable or permanently inflated strips or built in regions providing rigidity (73).

-20 -In Figure 11, the sequential use of a container used in accordance with a third aspect of the Invention is illustrated by a series of diagrams to show the position and contents of the cylinder at different stages of its operation. In position "A" the cylinder has been refilled with dry rehydration driver (73). In position "B" the cylinder is positioned in contact with the external water supply so that water (74) is drawn into the box through the rehydration driver excluding membrane (75) by osmosis due to higher osmotic pressure within the cylinder (76) generated by rehydration drivet, (73), which dissolve to form a concentrated SPF saline solution within the box. The contaminated water source is fed across the face of membrane (2) to allow purified water to move by osmosis across the salt excluding membrane (75). In position "C" the cylinder, now containing dilute SPF free saline solution, has been inverted and the rehydration driver permeable selectively permeable membrane (77) is now face down in the water, so that sodium chloride in the SPF saline solution within box is allowed to dissipate by passing through the rehydration driver permeable membrane (77) into contaminated water source. In position "D", dissipation of sodium chloride is complete and box containing SPF water is tilted to the horizontal position allow sampling of potable water through port (78) following removal of removable cover (79) and when empty for further rehydration driver to added in a similar manner through a separate port (not shown). At this point the cycle is initiated again, It will be understood by those skilled in the art that if three such units are used in sequence then a continuous supply of potable water will be available.

In Figure 12, a container (80) in accordance with a third aspect of the invention is in the form of a cylinder whose mountings and support framework arc intended to facilitate water generation and salt dissipation when located over an external water supply even if this fluctuates in depth and height. Here the cylinder is mounted on a floating raft (81) so that regardless of any fluctuations of the depth or height of the external water supply the appropriate selectively permeable membrane can be maintained at the optimum height above the external water supply when it is in active use and in the example shown, held in that position by a locking nut (82).

In Figure 13, a container (83) accordance with a third aspect of the invention is in the form of a cylinder whose design is intended to facilitate self inversion of the -21 -cylinder once the rehydration driver had generated a predetermined mass of a dilute solution of the rehydration driver. In the example shown, the container consists of two regions (84) and (85) where region (85) and containing the salt releasing membrane has a region to the main axis containing the centre of gravity (86). When the container is placed in the primary position prior to rehydration of the rehydration driver taking place, the container is stable and the salt excluding membrane (87) will remain in contact with the external water supply. It remains in this position until the solution of the rchydration driver is diluted to a predetermined amount by the ingress of water. This will take the water level to a depth where it is now present to a predetermined depth in the offset region of the wider cylinder. At this point the centre of gravity is no longer below the fulcrum (88) and is displaced laterally from its stable position. Consequently the container will now start to tilt. As it does so the lateral movement of water increases its instability and the container becomes inverted. Once inverted it is stable in this position with the salt releasing membrane (89) in contact with the external water supply. It will be appreciated by those skilled in the art that were the purified water to be removed with the cylinder in this position via a tap located just above the salt releasing membrane, then once the container is empty of purified water the container can be re-inverted with minimum effort or may itself tilt back to that position so that the salt excluding membrane (87) is again at the lowest point of the device.

Figure 13 also illustrates further independent features of the invention that, arc particularly suitable to be incorporated into designs based on the third aspect of the invcntion, but can where appropriate also be utilised, where appropriate in other aspects of the invention. The cylinder is shown located on a wheeled (90) bowser trolley (91) to facilitate its transport and independently location in a external water supply or on a secure dry site from where for example, the safe water can be removed and br the container reloaded with fresh dry rehydration driver. The cylinder can be secured in any required using a locking device (92) on the fulcrum (88) or the usc of ropes (93). The latter could include pulleys (not shown) to facilitate a change in position of the container.

-22 -In Figure 14, a container (94) accordance with a third aspect of the invention is in the form of a pair of rectilinear boxes (95) and (96) and where the design is intended to facilitate and enhance self inversion of the cylinder once the rehydration driver had generated a predetermined mass of a dilute solution of the rehydration driver. This is achieved by having an offset region (97) of the container where the salt releasing membrane (98) Is located being shaped so that liquid that accumulates within a localised region (99) exerts a high angular momentum as the liquid accumulates a significant lateral distance from the pivot point (100).

Consequently, once liquid starts to accumulate in region (99) there is a rapid lateral movement of the centre of gravity and the container rapidly inverts. Once this is complete and the container becomes inverted and stable in this position with the salt releasing membrane in contact with the external water supply. As explained above with respect of the design shown in figure 12, the product can be shaped so that once largely empty of liquid it will re-invert and return to its previous position.

Figure 15 a container (101) in accordance with the fourth aspect of the invention is shown in cross-sectional view. The container consists of three inter-connecting chambers where chambers "A" and "B" are supported over running water and where chamber "C" rests on an adjacent hard standing. That is an "osmotic box" of a multi-compartment design that facilitates concurrent water up-take, salt dissipation and water storage. On the base of chamber "A" is a first selectively permeable membrane (102) that excludes an rehydration driver and on the base of chamber "B" is a second selectively permeable membrane (103) that allows passage of the rehydration driver. The first and second selectively permeable membranes (102 and 103) arc both specific pathogen excluding membranes. Either manually or automatically a predetermined mass of crystals of anhydrous sodium chloride (104) is delivered from a dispenser (105) located in the roof of chamber "A" so that they rest on the inside of selectively permeable membrane (102). This delivery takes place in a manner that is intended to maintain the SPF status of the chamber. To function, the water supply must be in continuous contact with both membranes (membranes (102 and (103)). The direction of flow of the water (106) should ensure that if a common source of external water is used the water should first flow -23 -across chamber "A" and not chamber "B" so that water of the lowest possible salinity only enters chamber "A".

Chambers "A" and "B" are connected by a continuous connecting tube (108) that is attached near the base of chamber "A" and near the top of chamber "B". When appropriate, liquid can be retained in chamber "A" by the closing of valve (109).

Alternatively when appropriate, liquid can be transferrcd from chamber "A" to chamber "B" when valve (109) is opened and electric pump (110) is activated.

Alternatively such transfer could take place by means of a siphon (not shown) or by manually operated pumps. Where appropriate electrical power can be supplied by integrated solar panels (111) and optional electrical storage devices (not shown) and where if power is generated in this manner, it is preferable to use components adapted for DC power. A similar arrangement of connecting tubes, valves and pumps connects chamber "B" with a storage chamber "C" located on the bank of the river. Chamber "C" has a water-tight consumption port (112) for gaining access to its contents, port (112) being protected by a removable cover (113) when not in use.

While not restricted to the fourth embodiment of the invention, figure 15 shows a toxic metal capture module (107) located to reduce toxic metal contamination of the water entering the device (101). By locating it in the position shown toxic metal contamination is reduced for both the water that enters the device and that which flows past it. Thus for example, if the feed water was contaminated with arsenic or heavy mctals and these could be retained with the module (107) and if the exit water was commonly used for agricultural applications then there would be primary and secondary health benefits to the use of such a device.

The sequence of operations required to generate potable water will now be explained with reference to figure 15 and the flow diagrams in figure 16 and will be initiated with all containers empty of liquid. Here each cycle time is given as 24 hours but this time is given purely as an example. Again for illustration purposes it is assumed that the storage tank can contain "two units" of generated purified water.

-24 - 1. At the start of day one, a unit of salt is added to chamber "A" and osmosis initiates the generation of SPF saline solution in chamber "A".

2. At the start of day two if depth detectors in chamber "A" have shown the chamber contains an adequate volume of dilute saline solution, this is then pumped to chamber "B" where the salinity reduction by dialysis commences.

Once chamber "A" is largely empty of dilute saline, a further charge of dry salt is dispensed into chamber "A".

3. At the start of day three, the next stage of eh cycle commences if (for example using an integrated conductivity meter in chamber "B") it is known that the salinity concentration of the solution in chamber "B" has been reduced for this solution to be classed as potable. If this is the case, the contents of chamber "B" are now pumped to the storage tank "C" from where it can be consumed. Once chamber "B" is largely empty of potable water, the dilute saline now generated in chamber "A" is pumped into chamber "B" and a fresh charge of salt added to chamber "A".

4. I.e. at this point a total of two units of potable water have been pumped into the storage chamber. The salinity of a solution in chamber "B" is being reduced and diluter saline is accumulating in chamber "A".

5. By day four a continuous cycle of SPF saline solution and its desalination can take place if the potable water is being consumed at approximately the rate it is being generated.

It will be understood that the depth indicator in the storage tank "C" must be positioned so that this indicates a predetermined maximum volume of liquid is present whcn the next batch of liquid is pumped to ensure there is always an adequate space to pump in a full "charge" of purified liquid. Consequently, until this depth indicator shows that a full load of potable water can be transferred to chamber "C" from chamber "B" no pumping can take place in any chamber and any -25 -pumping of liquids is suspended. This does not cause any problems as it is not disadvantageous if liquids remain in chambers "A" and "B" for longer than the minimum period.

The sequence of operations needed for this can utilise manual control mechanisms and detection equipment or those better suited to automated processes. By way of example the manner in which a measured mass of salt is added via port (105) could be manually dispensed or delivered by an electrically operated Archimedes screw.

Similarly the depth of liquid present in any chamber could be simply observed via sight gauges (not shown) built into the walls of chambers or depth gauges with electrical sensors (114) and linked to electrical water pumps. Similarly, the salinity of liquid in chamber "B" could be observed by sensitive floating hydrometers or more accurately measured by a conductivity meter (115) and where the pumping of the contents of chamber "B" to chamber "C" is triggered by the a predetermined minimum conductively level corresponding to that appropriate to potable water.

In Figure 17, a container (116) accordance with a fifth aspect of the invention is shown and where the purified water is generated by dilution of a concentrated solution of already highly purified saline solution. While not restricted to this application such a container is specifically suited to the production of highly purified water of the type used for solutions intended for example for the production of intra-venous (IV) solutions. That is solutions of absolute sterility and free from toxins and pyrogens. The concentrated saline solution can be manufactured to meet these stringent requirements and if for example all internal surfaces are manufactured free of such contaminants. Such a standard will be maintained if adverse contaminants are excluded by the membranes. In the example shown in figure 17, a stock concentrated solution of purified saline (117) is connected via a luer connector (11 8) so that concentrated sterile saline can be delivered directly to the lumen of the sterile pyrogen free chamber (119). This can include a mechanism / procedure so that the mass added can be accurately delivered and will include a tap (1 20) to seal the upper region of the lumen. The walls of the lumen will contain on opposite sides of the chamber a first selectively permeable membrane (121) that excludes an rehydration driver and the other side a second selectively permeable membrane (122) that allows passage of the rehydration driver.

-26 -The first and second selectively permeable membranes (121 and 122), are both specific pathogen excluding membranes and are manufactured free of any pyrogens.

Water that is free of low molecular weight impurities, that if present would make the water unsuitable for the intended purpose of the generated water, is delivered down connecting tube (1 23). Depending which of two taps (124) or (125) is open this water is directed in one of two directions, however in both cases this liquid flows out of the product to waste (126) but in a manner that further contaminates cannot come into contact with the selectively permeable membranes. Initially the flow is solely past but external to the salt excluding membrane (124) such that, for example by osmosis, a dilute sterile solution is generated within the lumen of chamber (119). Then once an adequate mass of dilute sterile saline has been generated, valve (124) is shut and value (125) is opened so that water now flows instead across the salt releasing membrane (122). Once the salinity of the water within the lumen has been adequately removed, both valves (124 and 125) are shut and highly purified water can now be removed for the lumen through the now opened valve (127) and temporary linked luer lock (128) to a separate storage container. It will be understood that such a container can be used to sequentially generate multiple masses of high quality water. It will be further understood that the generation of such solutions can be automated using variations on the parallel technologies and components already considered in the second aspect of the invention.

In Figure 18, is a container (129) accordance with a fifth aspect of the invention is shown and where the purified water is again generated by dilution of a concentrated solution of already highly purified saline solution water utilising many features already described in figure 17. However, in this example burstable ampoules of concentrated saline solutions (130) or dry anhydrous sodium chloride (131) arc pre-loaded into the lumen of the chamber while maintaining its high purity status and made of materials manufactured and of a quality that this status is maintained. Here ampoules are burst by, for example, by external compression one at a time to generate cycles of dilute saline solutions and purified water. As the burst ampoules remain within the lumen of the product there is a mesh (132) to prevent the ampoules blocking the drainage tube inlet port (133).

-27 -Discussion The above diagrams and linked embodiments represent devices of varying sizes, complication and application and where the following are given as non-limiting examples. Using figures generated by McConnan (Ed) in ISBN 0 85598 445 7 2004 and published by Oxfam in 2004, 2.5 -3.0 litres of potable water are needed to satisfy an adult individual's daily survival needs for water. From this we are have assumed ten litres a day are the survival requirements for a "standard" family of two adults and two infants. Further, for convenience a "turnover time" of 24 hours is assumed for the generation of water using embodiments based on the first, second and third embodiments.

The first aspect of the invention, the simple "osmotic box" is intended to be manually inverted and so must be capable of being physically lifted ideally by a single adult and so a reasonable total weight would be twenty kilograms.

Consequently, a "set" of three of these so that if one is used for water generation, the second for salt removal and the third for consumption would provide the emergency needs for a family.

The third aspect of the invention, the simple "inverting cylinders" is intended to be capable of inversion and manipulation by an individual and using pulleys etc. For such a device we expect a maximum water volume would be I cu metre of water or 1000 litres. Consequently, a "set" of three of these, again so that if one is used for water generation, the second for salt removal and the third for consumption would provide the emergency needs for 100 families or a moderate sized village.

Both of these aspects can be readily adapted to facilitate water generation and salt dissipation when located over an external water supply of fluctuating depth and height. For example (as shown in figure 12) mounted on a suitable sized floating raft so that regardless of any fluctuations of the depth or height of the external water supply the appropriate selectively permeable membrane is maintained at the optimum height above the external water supply when it is in active use.

-28 -The second aspect of the invention, the "automatic unit" is intended to at least match that of the inverted unit and so could equally provide the needs of 100 families. This would use existing washing machine and dishwasher technology and the compact and the compact rolled cartridge filter units would be produced using equipment already in use in modules already used reverse osmosis desalination plants.

An alternative application for such an embodiment is as a fitted unit in an individual home or apartment block. It would appropriate to use such a device if an adequate supply of fresh water was being piped that dwelling buts its safety was not guaranteed. It would use water supplied by that source and the purified water could be stored using its own integrated storage tank or be transferred to an existing water storage tank. Similarly its power supply could be integrated with an already installed power unit or for example be supplied from its own integrated solar power unit. The discharged water could either go to waste or be used as a source of water where minor salt contamination was not of concern. As noted previously, such water could have improved quality with respect to its previous level of, for example, toxic metal content.

The fourth aspect of the invention, the utilisation of separate water generation and salt dissipating units, is only limited in size by mechanical considerations and the water flow of for example the feed river. Consequently we would anticipate the unit could easily generate five cubic metres of water per day and so provide essential daily potable water for 500 families per day. The electrical unit is no more complex than that already in use in domestic washing machines and dishwashers and so could be fabricated at low cost once mass produced and could easily run off locally generated solar power or miniature water turbines located in the water gully.

Similarly, water usage could be optimised by computer control mechanisms with feedback loops.

In any large units based on any of the proposed embodiments, and where it is possible that the hydrostatic head of water above a selectively permeable membrane -29 -may adversely affect its intended purpose the dimensions of the container can be configured to minimise this effect. By way of example only, in the forth aspect of the invention the dimensions of chambers "A" and "B" shown in Figure 1 5 can be extended laterally beyond the area of the selectively permeable membrane to reduce the depth of liquid above their respective selectively permeable membranes.

Depending on water availability, and where to waste water is being discharged to any of the cited embodiments can be used in such a manner that the external mass of water used is minimised leading to the highest practical concentration of salt contamination of water distal to the device or alternatively minimum restriction Ofl water usage to give the lowest practical salt concentration. With electronic control and feedback mechanisms to continually determine salinity and not only regulate gross water flow but change this to take into account changing proximal and distal salinity ratios, both water uptake rates and external salinity levels can be regulated to independently meet specific objectives for independent optimisation of water usage and water discharge quality.

Using water uptake rates already achieved in Table 3, we can already generate I litre of water with 10 grams of domestic salt in 24 hours and if this is purchased in reasonable amounts this equates to a net potable water cost of 0.1 UK pence per litre. If the salt is retained in the primary stage for 28 hours this mass can be doubled and hence potable water costs halved. With expected improvements generated by optimised membranes it is reasonable to halve this cost again.

Consequently, even with manufacturing and plant costs this is still a very low cost for generating potable water to isolated families and in the immediate aftermath of disasters and with minimum technology and power and where the only consumable item will be domestic food grade salt.

Taking the UK Thames River in mid-season flow we have calculated the number of families such a river can support in an emergency using this technology and where the "exit" water must still meet WHO guidelines for potable water. This suggests that this technology the Thames could supply over 15 million adults with their essential water supply without adversely affecting the water supply to people distal -30 -to the positioning of such units. Further as the technology improves, this number will increase.

While not yet experimentally investigated we would expect there to be a very significant reduction in exposure to heavy metal and toxic chemical exposure to families who arc supplied with water using this technology compared with if they consumed the water made "safe" by for example chlorination.

The fifth aspect of the invention covers a separate requirement: the supply of toxin / pyrogen free water for isolated medical needs from a local water source. For such water it is relatively easily to reduce metallic and chemical contamination to an acceptable level of WFI (water for injection) by ion exchange modules but removing residual pyrogens is only possible by complex multi-stage processes in sealed units with expensive consumable items. Independently, terminal heat sterilisation at moderate heat levels (including autoclaving) does not destroy toxins and in certain situations may in fact increase them. Consequently, however using water purified by ion exchange as the feed water for the devices shown in the fifth embodiments combined with concentrated WFI concentrated saline solutions to minimise transport and storage costs will provide a low cost solution to this problem for rural health centres.

The invention will now be illustrated by a number of specific examples, using the following experimental procedures.

Materials and Methods Experiments were conducted using the following membranes: Porelle P412 (PIL Membranes Ltd, King's Lynn, Norfolk, UK) having a nominal wall thickness of 12 microns. This membrane is a viral excluding, solid vapour transmitting polyurethane film. Independent experiments indicate that the membrane has a molecular weight cut-off of between 500 and 1,000. Samples of production grade material were used in all cited experiments.

-31 -HTI membrane This was a fresh section of membrane removed from a commercially purchased Hydrowell TM pack Lot number 0604101960149 supplied by Hydration Technologies, mc, 24484 Ferry Street. S.W. Albany, OR 97322, USA Experiments with the Porvair membrane were conducted using specially constructed standard test chambers, in which disks of membranes were secured by water-tight "o" rings. The base of such test chambers consisted of a supported piece of one of the above types of membrane, with a circular cross-sectional area of approximately 10 cm2 and an internal volume of 50 cm2. This enabled a standard area of membrane to be placed just below the surface of a known solution to determine, by gravimetric and other methods, changes in the volumes and compositions both internal and external to the test chambers. Multiple test chambers could be placed in a common water bath, having a water volume of 19 litres. Normally "tap" water was used.

The experiment with the HTI membrane was conducted immediately the membrane was removed from the original device and while it was still wet. A circular disc (exposed area 400 cm2) was sealed into a cylinder 22.5 cm internal diameter and 45 cm high. The mass of salt added to the test chamber was pro-rata with respect of membrane surface area to the 1 gram of rehydration driver used in the "standard" experimental test chambers described above for the Porvair membrane. The test rig was placed in a water bath containing approximately 50 litres of "tap" water. At all times the surface of the lkuid within the test chamber was maintained at not more than 5 cm difference from the surface of the liquid in the water bath.

Mass changes within the test-pots were determined gravimetrically. Changes in solute concentration and mass were determined by conductivity measurements using aJcnway (Dunmow, Essex, UK) model 4310 temperature compensated conductivity meter. All parameters were recorded on a specially constructed database that facilitated data comparisons both within and between experiments.

-32 -Experimental Results Part 1 Experiments with the Porelle P412 membrane

Example 1:

The uptake of water. using Porelle P412 membranes, by test pots present in a large excess of water and each containing 1 gram of dry analytical grade sodium chloride Table 1: mass of water in grams generated against time within the test chambers and equivalent mass in kilograms generated by one square metre of same membrane Time (hours) 6 13.5 24 48 Mass per pot 8.4 10.7 11.3 11.6 Mass per metre2 7.0 8.9 9.4 9.6 This confirms that a reasonable mass of virus (and hence bacteria) free saline solution can be generated with an rehydration box with salt applied internally to the P412 membrane at this loading density.

Time may be varied in order to optimise the amount of liquid generated for a given salt concentration. For example, with this membrane approximately 30% more liquid is generated if the time the product is left in contact with feed water is extended from six to twenty four hours.

Additionally, where salt density is changed product optimisation is further possible by regulating the salt concentration on the first membrane for either maximum water uptake or minimum salt utilisation.

Increased salt concentration at the outset will increase the rate of water generation but results in a higher salt residue. Accordingly, when optimising product performance, such an increase in water generation i-nay in part be offset by both increased problems relating to salt disposal and increased time taken to remove the salt by the secondary membrane.

Example 2:

Removal of sodium chloride from thc SPF saline solution by dialysis Duplicate test pots containing 40 mIs of 0.5, 1.0, 2.0 and 4.0 percent saline solutions (0.2, 04, 0.8 and 1.6 grams of sodium chloride per pot respectively) were placed in a common water bath. The salinity of the individual test pots was determined at intervals by measuring the conductivities of the solutions. The following data represents the average values for the duplicate test chambers. The concentration of the saline solutions (as a percentage w/w) remaining in the test chambers against time and against the background salinity present in the water bath was measured.

Table 2: salinity measurements against time for different starting concentrations of saline solutions Time (hours) 4.0 6.0 12.8 24.0 36.0 0.5% saline 0.32 0.25 0.13 0.04 0.02 1.O% saline 0.70 0.49 0.25 0.14 0.05 2.O% saline 1.35 0.90 0.42 0.17 0.07 4.0% saline 2.25 1.70 0.80 0.28 0.14 Initial equivalent conductivity of the "tap water" was O.O35% Consequently, product optin-iisation can be directed at maximising the degree to which osmosis can take place concurrently with the removal of the rehydration drivers.

-34 -Also, the palatability of a range of saline solutions, prepared using "domestic grade, table salt" in a safe environment, were accessed "blind". This suggested that water with a salinity of 0.2% salt concentration did not taste "salty".

Part 2 Experiments with the HTI membrane Experiment 3 (over-leaf) shows comparative the results between the HTI and Porvair P412 membrane. The water uptake rate was much faster, saline was better retained and the absolute mass of water generated (over 100 ml) flowed over the top of the standard test chamber making it unsuitable for comparative experiments.

Consequently, a matched experiment was conducted using a specially constructed deeper test chamber of a larger surface area into which an increased mass of sodium chloride was added on a pro-rata basis.

As was expected from the preliminary experiment the results for the HTI membrane grossly exceed those for the Porvair P412 membrane with respect of mass of water generated within the test chamber per gram of salt added. Further for the HTI membrane, it was apparent that osmotic uptake continued for many days even when the concentration was lower than where osmotic uptake ceased with the Porvair membrane. Consequently, then potentially not only have the experiment shown that for the HTI membrane one gram of sodium chloride can generate almost 100 mis of water this mass of water can be even higher if the equipment can be left running an extended period. This results in lower unit costs and reduced environmental contamination of the environment for the waste salt solution.

With the complex manufacturing processes (and hence high cost) used to produce the i-un membrane and its inability to withstand any drying out cycles, its use would be limited in certain applications it does suggest that once a membrane is specifically manufactured for maximum water uptake and salt dilution the projected salt usage per unit of potable water generated and hence unit costs of such water can be considered conservative and are likely to be improved in the future.

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Example 3:

The relative and absolute water uptake rates and salt losses for Porclle P412 membranes and a test HTI membrane Table 3: water uptake rates and salinity losses against time for Porelle 412 and HTI membranes Membrane A B C D E F G H I J K HTI 24h 4035.0 100.08 4.20 1.09 0.87 80.00 44.00 35.10 8.90 0.371 9.271 HTI 48h 6116.0 152.90 3.19 0.72 0.58 80.00 44.00 35.47 8.53 0.178 4.443 HTI 120h 9860.0 246.50 2.10 0.45 0.33 74.00 44.00 32.53 11.47 0.096 2.390 P412 24h 10.50 11.30 0.47 10.0 0.19 1.90 1.00 0.019 0.981 0.041 45.417 P412 48h 10.50 11.30 0.23 10.0 0.10 1.00 1.00 0.010 0.990 0.020 22.222 Tap water 0.03 Key A Total water uptake in grams B Water uptake in kg/m2 C Water uptake in kg/m2/hour D Theoretical sodium chloride uptake as percentage expected concentration E Actual sodium chloride uptake as percentage expected concentration F Theoretical percentage retention of sodium chloride G Mass of sodium chloride added to each test chamber I-I Estimated mass of sodium chloride present at stated time 1 Estimated mass of sodium lost (G -H) J Mass of sodium chloride lost per hour K Mass of sodium chloride lost per hour /m2 -36 -General discussion For drinking water, the WHO recommended a maximum upper concentration of dissolved solids of O.15%, with the preferred level being 0.050%. The above results confirm that these concentrations can be achieved in a reasonable period of time using a combination of membranes intended to enhance osmosis (first membrane) and salt reduction (second membrane).

It will also be apparent to those skilled in the art that as the above concentrations represent maximum concentrations that are expected at the end of forward osmosis there is considerable scope for product optimisation. The above experiments indicate that even for non-optimised systems the area of membrane required to remove the generated saline can be smaller in area than that used in the first membrane to generate the SPF solution. However, in product optimisation it may be considered advantageous to use a relatively large second membrane to maximise the rate at which the low molecular weight drivers are removed.

It is apparent that by using saline as the rehydration driver there will be some increase in sodium consumption. However, those skilled in the art will be aware that with "normal" liquid consumptions this will be an acceptable contribution to the RDA of sodium.

END OF MAIN TEXT

Claims

-37 -Claims 1. A container, for generating a solvent of improved quality including a driver to facilitate rehydration thereof within the container, wherein the container comprises at least a first selectively permeable membrane and is adapted to allow sequential rehydration of the composition and dissipation of the driver from the container.
2. A container as claimed in claim 1, comprising a first selectively permeable to membrane for rehydration of the composition and a second selectively permeable membrane for dissipation of the driver from the container.
3. A container as claimed in claim 2, wherein the first selectively permeable membrane substantially excludes passage of the driver and the second selectively permeable membrane substantially permits passage of the driver.
4. A container as claimed in claims 2 or 3, wherein the second selectively permeable membrane is isolatable from a rehydration source in contact with the first selectively permeable membrane.
5. A container as claimed in claim 4, further comprising a removable protective layer covering the second selectively permeable membrane.
6. A container as claimed in claims 2, 3, 4 or 5, wherein the first and second selectively permeable membranes are located in or form different regions of the container.
7. A container as claimed in claim 6, in the form of a box, the first and second selectively permeable membranes being located in or forming different sides of the box.

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8. A container as claimed in any of claims 2 to 7, wherein the first or second selectively permeable membrane is a specific pathogen excluding membrane.
9. A container as claimed in any of the preceding claims, wherein the composition to be rehydrated is in the form of a solid or a concentrated solution.
10. A container as claimed in any of the preceding claims, wherein the rehydratcd composition is a specific pathogen free solid, semi-solid or solution.
11. A container as claimed in any of the preceding claims, wherein the rehydrated composition is a consumable product.
12. A container as claimed in any of the preceding claims, wherein the driver is capable of generating a substantially constant osmotic pressure in the container during rehydration of the composition.
13. A container as claimed in claim 12, wherein the driver is a salt of a weak acid or base.
14. A container as claimed in any of the preceding claims, further comprising a reservoir for a source of water for rehydration of the composition, the reservoir being separated from the composition by the first selectively permeable membrane.
15. A container as claimed in any of claims 2 to 14, further comprising a reservoir for a source of water for dissipation of the driver, the reservoir being separated from the composition by the second selectively permeable membrane.
16. A container as claimed in claims 14 or 15, wherein the reservoir is adapted to allow the water source to contact the first or the second selectively-permeable membrane continuously.

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17. A container as claimed in claims 14 or 15, wherein the reservoir is adapted to allow the water source to contact the first or the second selectively-permeable membrane periodically.
18. A container as claimed in any of claims 14 to 17, wherein the reservoir is adapted to allow the water source in contact with the first or the second selectively-permeable membrane to be recycled.
19. A container as claimed in any of the preceding claims, wherein the container is adapted to allow a single rehydration and dissipation cycle.
20. A container as claimed in any of the preceding claims, wherein the container is adapted to allow a continuous rehydration and dissipation cycle.
21. A container as claimed in any of claims I to 19, wherein the container is adapted to allow multiple rehydration and dissipation cycles.
22. A container as claimed in any of the preceding claims, comprising means for introducing rehydration driver into the container under specific pathogen free conditions.
23. A container as claimed in any of the preceding claims, further comprising a sump, for retaining at least a portion of the rehydration driver or a concentrated solution thereof within the container.
24. A container as claimed in any of the preceding claims, comprising means for removing rehydrated composition from the Container under specific pathogen free conditions.
25. A container as claimed in any of the preceding claims, further comprising a compartment for allowing continuous access to rehydrated product.

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26. A container as claimed in any of the preceding claims, wherein the container is adapted to allow staged or stepwise rehydration of the composition.
27. A container as claimed in claim 26, wherein the container comprises at least a first compartment and a second compartment, the first compartment containing a first fraction of the composition for initial rehydration thereof and the second compartment containing a second fraction of the composition for subsequent rehydration through contact with rehydrated first fraction of the composition.
28. A container as claimed in any of the preceding claims, further comprising of it being in the form of a box, the first and second selectively permeable membranes being located in or forming different sides of the box and where box can be rotated around a fulcrum enabling either some or none of the selectively permeable membranes to be in contact with the external water source.
29. A container as claimed in claim 28 and where Its dimensions and weight distribution enable self-inversion once a certain mass of water accumulates within the container.
30. A container as claimed in claim 28 and where its dimensions and weight distribution enhances the speed of self-inversion once a certain mass of water accumulates within the container by being so shaped that liquid can accumulate in a region distant from the fulcrum.
31. A container as claimed in claim 28 and where its dimensions and weight distribution enable a reversal of self-inversion once a certain mass of water has been removed from within the containcr.
32. A container as claimed in claim 28 and where its dimensions and weight distribution enhances the speed of reversal of self-inversion once a certain mass of water accumulates within the container by being so shaped that once a certain mass of liquid has been removed from with the container.

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33. A container as claimed in any of the preceding claims, further comprising of it being in the form of a box, the first and second selectively permeable membranes being located in or forming different sides of the box and where box is capable of being dismantled and regions of the walls not containing a selectively permeable membrane are water tight but flexile for the purpose of ease of transportation and storage and then being assembled at the location where it is to be used.
34. A container as claimed in claim 33 and where the rigidity required for optimum use is achieved by inflation of integrated regions of the flexible sleeve.
35. A container as claimed in claim 33 and where the rigidity required for optimum use is achieved by incorporation of permanently inflated or rigid struts.
36 A container as claimed in any previous claim which is supported by a floatation device that allows a selectively permeable membrane to remain at the optimum contact depth to an external water supply.
37. A container as claimed in any previous claim, for generating a solvent of improved quality including a driver to facilitate rehydration thereof within the container, wherein the container comprises at least a first selectively permeable membrane restricted to one region of the container and containing a rehydration driver so facilitate independent rehydration of that driver and a separate discrete region of the container where is located a secondary selectively permeable membrane and where that selectively permeable membrane facilitates independent dissipation of the driver from the container.
38. A container as claimed in claim 37 so constructed that the primary membrane in contact with the rehydration driver can act to draw solute into a discrete region of the container while concurrently in a different but connected region of the container a secondary selectively permeable membrane is dissipating a previously generated solution of now diluted rehydration driver.
39. A container as claimed in claim 37 where the sub-unit containing the secondary selectively permeable membrane is itself connected to a further storage -42 -region of the container to which solvent of a reduced concentration of osmotic driver can be directly delivered to.
40. A container as claimed in claim 27 in which both primary and secondary osmotic membranes are in simultaneously in contact with the same external water source but in design that this does not significantly adversely affect the function of either membrane.
41. A container as claimed in the previous claim 37 being a multi-compartment container that facilitates concurrent water up-take, salt dissipation and water storage and where the correct sequence of operations required for the correct generation of such solutions can be monitored, controlled and regulated automatically.
42. A container as claimed in any previous claim in which the rehydration driver can be delivered into that container in discrete individual measured amounts in a manner that does not risk the integrity of purpose for which that container is being used.
43. A container as claimed in claim 42 in which the rehydration driver is already present with the container in discrete individual measured amounts in a manner and where their contents can be individually released in a manner that does not risk the integrity of purpose for which that container is being used.
44. A container as claimed in any previous claim in which is designed and constructed so that the rehydration driver can be in the form of concentrated solution of that rehydration driver.
45. A container as claimed in claim 44 in which all aspects of the container, rehydration driver and mode of action make it suitable for the production of high quality solvents of which IV solutions are a typical example.
46. A container as claimed in 44 in which defined masses of that concentrated solution of that rehydration driver can be directly applied to the region containing the primary membrane.

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47. A container in which the quality of the source water can be improved, prior to it being in contact with a particular selectively permeable membrane, by a reduction in concentration of a substance that is disadvantageous if present in the water in its original concentration for its intended end use.
48. A container as claimed in any of the preceding claims, wherein thc first or second selectively permeable membranes is an enhanced integrity membrane.
49. A selectively permeable membrane for use in rehydration apparatus, wherein the membrane has been doped with a rehydration driver.
50. A container wherein the first or second selectively permeable membrane has been treated with a pore reducing coating.
51. A container wherein the first or second selectively permeable membrane is a laminate comprising at least two layers of membrane.
52. A container wherein the selectively permeable membrane is a specific pathogen excluding membrane.
53. A selectively permeable membrane wherein the driver is evenly distributed on the surface.
54. A selectively permeable membrane wherein the rehydration driver is in gel or hydro-gel form.
55. A selectively permeable membrane wherein the dtiver is present in admixture with an adhesive.
56. A selectively permeable membrane wherein any rehydration driver adhesive is water-soluble.

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57. A selectively permeable membrane where in the selectively permeable membrane has a secondary open layer to give it increased protection from physical damage.
58. A selectively permeable membrane where in thc selectively permeable membrane has a secondary open layer to reduce its occlusion by particulate matter.
59. A selectively permeable membrane where in the selectively permeable is manufactured in a form and by a method that maximises surface area in a restricted space.
60. A method as claimed in any previous claim which includes a step of washing the contents of the container.
61. A method as claimed in claim 60 wherein the wash step includes a disinfectant rinse.
62. A container as claimed in any previous claim which incorporates a means of determining the depth of a solution in a particular compartment.
63. A container as claimed in any previous claim which incorporates a means of determining the salinity of a solution in a particular compartment.
64.. A container comprising: a first compartment for holding a first component for rehydration thereof and having a selectively permeable membrane; and a second compartment for holding a second component for subsequent mixing with the rchydratcd first component, the container being reversibly convertible between a first conformation in which the first and second compartments arc not in fluid contact with one another and a second conformation in which the first and second compartments are in fluid contact with one another, so as to allow mixing of the first and second components.-45 -
65. A method of rehydrating a composition within a container comprising at least one selectively permeable membrane, the composition including a driver to facilitate rehydration thereof, which comprises sejuentially, contacting the container with a water source to allow rehydration of the composition and contacting the container with a water source to allow dissipation of the driver from the container.END OF CLAIMS