A PORTABLE WATER FILTRATION DEVICE

Abstract

A portable water filtration device is provided. The portable water filtration device comprises a housing defining an interior volume, said housing comprising; an input port for receiving water under pressure from an external source, and; an output port having an open position and a closed position. The device further comprises; a filter comprising an an array of hydrophilic capillary fibre membranes, said filter being positioned within the housing so as to form a fluid path between the interior volume of the housing and the output port such that, in use, when the output port is in the open position, water received at the input port flows under a pressure differential induced by the external source through walls of the capillary fibre membranes to respective open ends of the capillary fibre membranes to the output port, and further wherein; the filter fills at least 65% of the interior volume of the housing.

Claims

1-33. (canceled)

34. A portable water filtration device, comprising: a housing defining an interior volume, said housing comprising; an input port for receiving water under pressure from an external source; a filter comprising an array of hydrophilic capillary fibre membranes; a reservoir surrounding the filter, and; an output port having an open position and a closed position; wherein the device further comprises; the filter being positioned within the housing so as to form a fluid path between the reservoir and the output port such that, in use, when the output port is in the open position, water received at the input port flows under a pressure differential induced by the external source through walls of the capillary fibre membranes to respective open ends of the capillary fibre membranes to the output port, and further wherein; the filter fills at least 65% of the interior volume of the housing.

35. The device of claim 34, wherein the filter fills at least 75%, preferably at least 80%, of the interior volume of the housing.

36. The device of claim 34, wherein the housing is elongate in a first direction, and preferably wherein the capillary fibre membranes are elongate, and wherein the capillary fibre membranes and the housing are elongate in the same direction.

37. The device of claim 34, wherein the housing is substantially cylindrical.

38. The device of claim 34, wherein the housing further comprises a bleed valve operable to remove air from the interior volume of the housing.

39. The device of claim 34, wherein the housing further comprises a drainage port located below the input port, the drainage port having an open position and a closed position, preferably wherein the drainage port is located at the substantially lowest part of the housing.

40. The device of claim 34, wherein the filter is removably positioned within the housing.

41. The device of claim 34, wherein the filter is a cartridge filter.

42. The device of claim 34, further comprising mounting means for securely mounting the device, preferably wherein said mounting means comprise legs positioned on a bottom side of the housing arranged for mounting the device stably on a surface.

43. The device of any of claim 42, wherein the mounting means comprise at least one recess and/or loop arranged for receiving a strap such that the device may be hung.

44. The device of claim 34, wherein the device does not comprise pressurisation means.

45. The device of claim 34, wherein the housing further comprises a pressure regulator adapted to prevent the pressure in the device being raised above a predetermined level, preferably wherein the pressure regulator comprises a valve.

46. The device of claim 34, wherein the array of capillary fibre membranes comprises a plurality of pores having a mean size of less than 20 nanometres, preferably less than 15 nanometres.

47. The device of claim 34, wherein the fluid path comprises a secondary filter located between the filter and the output port, preferably wherein the secondary filter is a carbon filter and/or wherein the secondary filter is removable.

48. The device of claim 34, wherein at least one of the housing and output port is constructed from plastic materials, preferably at least one of water-grade acrylonitrile butadiene styrene, high-density polyethylene, medium-density polyethylene or polypropylene.

49. The device of claim 34, wherein at least the output port comprises an anti-microbial additive.

50. A water filtration system comprising: a portable water filtration comprising: a housing defining an interior volume, said housing comprising; an input port for receiving water under pressure from an external source, and; an output port having an open position and a closed position; wherein the device further comprises; a filter comprising an array of hydrophilic capillary fibre membranes, said filter being positioned within the housing so as to form a fluid path between the interior volume of the housing and the output port such that, in use, when the output port is in the open position, water received at the input port flows under a pressure differential induced by the external source through walls of the capillary fibre membranes to respective open ends of the capillary fibre membranes to the output port, and further wherein; the filter fills at least 65% of the interior volume of the housing; an external water source, and; connection means adapted to connect the external water source to the input port of the water filtration device such that water under pressure is provided to the water filtration device from the external water source.

51. The water filtration system of claim 50, further comprising a filter positioned between the external water source and the portable water filtration device.

52. The water filtration system of claim 50, comprising a plurality of portable water filtration devices having at least two input ports, wherein said plurality of water filtration devices are connected together by connection means such that each device is in fluid communication with the external water source and water under pressure is provided to each device from the external water source.

53. The water filtration system of claim 50, wherein the external water source is at least one of: a water harvesting tank providing a head pressure, a mains water supply, bore hole, reservoir, river and a well.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The invention will now be described with reference to the accompanying drawings, in which:

[0045] FIG. 1a illustrates a side view of a portable water filtration device according to the invention;

[0046] FIG. 1b illustrates an end view of a the portable filtration device;

[0047] FIG. 2 is a cross-sectional view of the portable filtration device;

[0048] FIG. 3 is a schematic diagram illustrating the portable filtration device connected to an external water source in use;

[0049] FIG. 4 schematically illustrates a plurality of portable filtration devices linked together;

[0050] FIGS. 5a and 5b illustrate a portable water filtration device according to the invention;

[0051] FIG. 6 shows a preferred filter for use in the filtration device of the present invention, and;

[0052] FIG. 7 illustrates a cut-away section of a filter for use in a preferred embodiment the present invention.

DETAILED DESCRIPTION

[0053] FIG. 1a illustrates a side view of a portable water filtration device 100 according to the invention. The filtration device 100 comprises an elongate, hollow, substantially cylindrical, main body 1 that defines an interior volume. The main body 1 has an open first end la and a permanently sealed second end 1 b. As can be seen in FIG. 1, the second end 1 b has a curved form and in some embodiments may be hemispherical or torispherical in geometry.

[0054] The first end 1a of the main body 1 is sealed by a removable end cap 3 so as to create a sealed interior of the filtration device. The main body 1 and end cap 3 together form a housing of the filtration device 100. The end cap 3 is removably attachable to the first end 1 a of the main body 1 by means of a screw thread interface (shown at 3a in FIG. 2), although other means of attaching the end cap 3 to the main body 1 are envisaged as would be known to those skilled in the art, such as a push-fit interface. The end cap 3 comprises an output port 5 having an open position and a closed position. In this embodiment, the output port is a tap.

[0055] The length, L, of the water filtration device (excluding the output port) is in the range of approximately 30 cm to 200 cm, preferably in the range of 70 cm to 100 cm and most preferably 84 cm. The cross-sectional diameter, D, of the device (as seen in the end-on view of FIG. 1b) is in the range of approximately 10 cm to 25 cm, preferably in the range of 15 cm to 20 cm and most preferably 19 cm. These dimensions ensure that the water filtration device 100 is portable and easily transportable.

[0056] The substantially cylindrical form of the main body 1, together with the curved form of the second end 1b, advantageously means that water and air are able to be stored under pressure within the filtration device without substantial deformation of the main body.

[0057] The main body 1 comprises first 7a and second 7b input ports, and a drainage port 9 located at an underside portion of the main body. Each of the input and drainage ports have an open position and a closed position, and will be explained further below.

[0058] FIG. 2 is a cross-sectional view of the filtration device 100, and illustrates a filter 20 comprising an array of elongate hydrophilic capillary fibre membranes. The filter is typically provided as a filter cartridge. The filter cartridge 20 is substantially cylindrical in shape and fits into the interior volume defined by the main body 1. With the filter cartridge 20 inserted into the main body 1, a reservoir 30 is defined within the main body 1 surrounding the filter 20. The reservoir is substantially annular is cross-section. Water within the reservoir 30 in contact with the fibre membranes of the filter 20 may pass, under a pressure differential, through pores in the walls of the fibre membranes, along their respective lengths to respective open ends proximal to the tap 5. Advantageously, water may therefore be filtered at any position along the length of the filtration device.

[0059] The fibre membranes are elongate in the same direction as the long axis of the main body 1, which advantageously means that the surface area of the fibre membrane walls in contact with water within the reservoir 30 is maximised. This ensures good flow rate of water through the filter (typically at least 51/min).

[0060] The structure of the filter cartridge 20 will be described in more detail with reference to FIGS. 6 and 7.

[0061] The filter 20 takes up at least 65%, preferably at least 75% and most preferably at least 80% of the internal volume of the housing (as defined by the main body and end cap). The filtration device 100 therefore has minimal storage capacity (relative to the size of the whole device) within reservoir 30, and is designed to allow a high rate of water throughput when connected to an external water source.

[0062] The filter 20 may be inserted and removed from the main body 1 through the first end 1a when the end cap 3 is removed. This advantageously allows the filter to be replaced when required. Preferred filters typically provide an estimated 250,000 litres of potable water before they require replacing. In other embodiments, the end cap 3 may not be removable and the housing is provided as a unitary member.

[0063] In order for water to pass from the reservoir 30 through the fibre membranes of the filter cartridge 20, a pressure differential must be generated across the walls of the fibre membranes. The filtration device 100 does not comprise pressurisation means, and FIG. 3 schematically illustrates a suitable arrangement for generating such a pressure differential.

[0064] As illustrated in FIG. 3, a harvesting tank 200 is supported by stand 210 at a height h above the top of the filtration device 100 (more specifically a height h above the height of the filter 20). The harvesting tank 200 has a volume of water (for example harvested rainwater) that is desired to be filtered to potable quality and consumed. A hose 202 is connected between the harvesting tank 200 and an input port (in this case second input port 7b) of the filtration device 100. Any other ports (here first input port 7a and drainage port 9) are in their closed position such that the interior of the filtration device 100 is sealed. A valve assembly 204 such as a tap may be used to control the flow of water from the harvesting tank 200 to the filtration device 100.

[0065] The input ports 7a, 7b are typically standard threaded ports.

[0066] In use, water is allowed to flow from the harvesting tank 200 into the reservoir 30 of the filtration device 100 along hose 202, with the tap 5 in its closed position. More specifically, water flows into reservoir 30 of the main body interior such that the water is in contact with the fibre membranes of the filter 20. The height of the harvested water in the tank 200 provides a water pressure of pgh, where p is the density of the water, g is the acceleration due to gravity and h is the height of the harvested water above the filter. This head pressure generates a pressure differential between the sealed interior of the filtration device and the external atmosphere.

[0067] When the tap 5 is moved to the open position, water stored in the reservoir 30 is driven by this pressure differential through the walls of the capillary fibre membranes to respective open ends of the capillary fibre membranes and out of the tap 5. Water will continue to flow through, and be filtered by, the filtration device 100 due to the head pressure induced by the harvesting tank. This means that the filtration device 100 does not require substantial storage capacity, or pressurisation means. Instead, the filtration device 100 of the present invention is portable and may be used to generate clean, potable water in locations where an external water source may provide the required pressure differential.

[0068] The example provided in FIG. 3 is in relation to a harvesting tank which may typically already be installed in the location of interest. Alternatively or in addition, the filtration device 100 may be connected, via first and/or second input port, to a mains water supply that is capable of providing a sufficient pressure differential such that water is driven from reservoir 30, through filter 20 and out through the tap 5. Other external water sources may be utilised, for example bore holes, rivers, reservoirs and wells where pumps may be used to provide the water under pressure.

[0069] Two input ports 7a, 7b have been shown in the examples so far. This advantageously allows two or more filtration devices to be linked together and be in fluid communication with one water source. Such an arrangement is schematically illustrated in FIG. 4, where three filtration devices 100a, 100b, 100c are linked to harvesting tank 200. As in FIG. 3, a hose 202 connects the harvesting tank 200 to the second input port 7b of first filtration device 100a. As shown in FIG. 4, a hose 202b is attached between first input port 7a of first filtration device 100a and a first input port of second filtration device 100b. Similarly, a hose 202c is connected between a second input port of second filtration device 100b and a first input port of third filtration device 100c. If the taps 5 of each filtration device are closed, water from the harvesting tank may flow through the hoses such that water surrounds the filters in the filtration devices. Subsequently, the head pressure from the harvesting tank provides sufficient head pressure to drive water through the filter of each filtration device once the respective tap is open. In this manner, a plurality of filtration devices may advantageously provide clean, potable water.

[0070] Although three filtration devices are illustrated in FIG. 4, two devices, or more than three devices, may be linked in such a manner.

[0071] Alternatively or in addition, the ports 7a, 7b may be connected to two harvesting tanks, or one connected to a harvesting tank and one to a mains water supply, such that there will always be a source of pressurised water available to the filtration device 100. Filtration devices comprising one input port, or three or more input ports, are envisaged.

[0072] As seen in FIG. 3, the filtration device 100 may optionally comprise a bleed valve 10, located in a top portion of the main body 1. The bleed valve 10 has an open position and a closed position. When the filtration device 100 is connected to an external water supply that supplies water under pressure, a user is able to move the bleed valve 10 to the open position in order to let air within the internal volume of the main body 1 escape (i.e. bleed the filtration device). This is not essential, but doing so advantageously allows an increased volume of water into reservoir 30, which consequently increases the flow rate of water through the filtration device as more water is in contact with the fibre membranes of the filter 20.

[0073] The bleed valve 10 may also act as a safety pressure release valve, and may be operable to automatically open when the pressure within the filtration device 100 reaches a predetermined threshold value. In such an instance the filtration device 100 comprises a spring rated pressure regulation device, where the spring rate is set such that the bleed valve 10 opens when the pressure within the main body 1 reaches a predetermined level. Once the pressure drops below the predetermined level, the bleed valve 10 automatically closes.

[0074] The drainage port 9 has an open position and a closed position. When the filtration device 100 is being used to filter water, the drainage port is in its closed position such that the internal volume of the filtration device 100 is sealed and the requisite pressure differential is generated. However, when the drainage port is in the open position, water provided to the filtration device 100 through one of the input ports will simply flow from the input port to the drainage port 9, rather than through the fibre membranes of the filter. This flow of water advantageously rinses the outer surfaces of the fibre membranes, removing any debris or sediment that may have previously been filtered out by the pores of the membranes and has settled on the filter. Rinsing the outer surfaces of the membranes in this manner prevents the filter from getting clogged with debris or sediment, thereby maintaining a suitable flow rate through the filter, and prolonging the life of the filter.

[0075] If the filtration device 100 is mounted off the ground (as seen in FIG. 3), the drainage port 9 is preferably located at the lowest point on the main body 1 (as seen in FIGS. 1-3), as this location allows the greatest amount of dirt, solids or sediment to be flushed from the device. If the device 100 is not mounted off the ground, the drainage port may be located away from the lowest point (as illustrated at 9a in FIG. 3) such that the drainage port does not foul the ground. In general, the drainage port is located below the level of the input port(s) such that water is able to flow under gravity from the input port(s) to the drainage port in order to flush out the filtration device.

[0076] A sediment pre-filter, shown schematically at 206 in FIG. 3, may be located between the external water source and the filtration device in order to remove coarse-size particles of dirt and sediment before reaching the filtration device, and therefore minimise the clogging of the filter membranes with dirt and sediment.

[0077] Referring to FIG. 2, a space 40 is defined within the filtration device 100 between the filter cartridge 20 and the tap 5. A secondary filter (not shown) may be positioned within this space 40 such that water passes through the filter cartridge 20, through the secondary filter and then out through the tap 5.

[0078] Due to the minimal relative storage capacity of the filtration device 100, it may be easily transported to a suitable location and connected to an external water source. In some embodiments, the filtration device 100 may comprise a carry handle to aid transportation. When in the desired location, the filtration device is typically mounted in a stable manner to prevent undesired movement, and preferably spaced from the ground, particularly when the drainage port 9 is located at the lowest point on the main body 1.

[0079] FIG. 5a illustrates a further example filtration device 200 according to the invention. The device 200 in FIG. 5a is mounted on spaced apart feet 102a, 102b such that the main body is spaced from the ground (as in FIG. 3). The feet 102a, 102b may be integrally moulded with the main body or may be provided as separate parts. The feet may comprise screw holes 103 (more clearly shown in FIG. 5b) that allow for secure fixing of the feet if desired. In such an instance it is desirable that the feet and filtration device are provided as separate parts such that the device may be removed from the feet, e.g. for cleaning purposes.

[0080] The main body 1 seen in FIG. 5a also comprises a plurality of strengthening ribs (shown at 104a, 104b, 104c, 104d) extending around the outer surface of the main body, and acting to increase the stiffness of the main body in order to resist deformation due to the internal pressure. Although four ribs are illustrated in FIG. 5a, more than four, or fewer than four, such ribs may be used.

[0081] As an alternative to mounting using feet 102a, 102b, the device may be hung (e.g. from a tree or ceiling) by straps or ropes. The gaps between adjacent strengthening ribs advantageously provide suitable recesses for placement of such straps such that they do not foul the input ports. A rope (or other suitable material) carry handle could be attached between the strengthening ribs. Hanging loops attached to the main body (not shown) are also contemplated.

[0082] The filtration device 200 seen in FIG. 5a comprises three input ports 7a, 7b, 7c to provide further flexibility in the set-up of such a device (e.g. linking to other devices as described above).

[0083] The filter cartridge 20 will now be described in more detail with reference to FIGS. 6 and 7.

[0084] FIG. 6 shows a preferred filter cartridge 20 for use in the water filtration device of the present invention. It may be used in the invention and located as illustrated by filter 20 in the previous figures. The filter may be substantially cylindrical in shape and as described above may fit into the interior volume of the main body 1.

[0085] Preferred water filters for use with the present invention are suitable for ultrafiltration: that is to remove all particles of a size greater than 0.01 microns. In another preferred embodiment the filter is suitable for nanofiltration or reverse osmosis. Reverse osmosis filters are capable of removing everything (including salts and oils) apart from pure water (H.sub.2O) from a liquid. Nanofiltration removes particles of a size greater than 0.001 microns (including aqueous salts).

[0086] Water is passed through the water filter under a pressure differential. This allows the water to be passed through finer filters than would be possible if the filtration device 100 were not pressurised.

[0087] A pore size of less than or equal to 25 nanometres is sufficient to remove most microbiological matter from the water, including viruses, thereby providing safe drinking water. However, for additional security, in preferred embodiments of the invention, the filter has a pore size of less than or equal to 20 nanometres, and more preferably have a pore size of less than or equal to 15 nanometres.

[0088] As is known in the art, the pore size of a material is in fact an average of the individual sizes of the pores (or holes) in the material, since it is inevitable that any material comprising a large number of pores will include some variation in these individual sizes. Preferred filters for use in the present invention have a tightly defined distribution of pore sizes such that the difference between the maximum pore size and the average pores size is minimized. Preferably, the standard deviation of the pore size distribution is less than 30% of the average pore size, and more preferably is less than 15% of the average pore size. In preferred embodiments of the invention, the filter has a maximum pore size of less than or equal to 30 nanometres, more preferably less than or equal to 25 nanometres, even more preferably less than or equal to 20 nanometres and most preferably less than or equal to 15 nanometres. In other embodiments, the maximum pore size may be even lower in order to perform nanofiltration or reverse osmosis, for example.

[0089] Preferably, the filtration device of the present invention will filter water with a pressure differential of any size. For example, the operating pressure differential of a preferred embodiment is preferably greater than 5 kPa (0.05 bar), more preferably in the range of 10 kPa (0.1 bar)-300 kPa (3 bar), even more preferably in the range of 50 kPa (0.5 bar)-100 kPa (1 bar). The large surface areas used in the filter of the present invention allow for a greater flow rate for a given pressure differential across the filter or between the reservoir-side of the filter and the ambient pressure of the surrounding environment. Thus the filtration device of the present invention can be used at lower pressures than smaller hand-held containers while still achieving a satisfactory flow-rate through the filters. As described above, the system is sealed so as to allow a pressure differential between the inside of the filtration device and the outside atmosphere to be created to drive water through the filter and out of the tap when opened.

[0090] The water filter of the present invention is preferably a membrane filter and comprises an array of hydrophilic capillary fibre membranes. Hydrophilic membranes are attractive to water and therefore water is passed through them in preference to other liquids and to gases. In this way, not only is the filtration offered by the preferred embodiments improved, but it is possible to use the filter even when it is not completely immersed in the water.

[0091] Preferably, the membranes are capillary hollow fibre membranes. These membranes act to filter the water as only particles smaller than their pore size may pass through them. The fibre membranes may incorporate carbon or other chemical elements, or reverse osmosis membranes. A combination of different types of filter membranes may be included in the filter. These may include ultrafiltration, nanofiltration and reverse-osmosis membranes.

[0092] In a preferred embodiment, the water filter comprises a filter cartridge comprising a plurality of fibre membranes. Preferably, the interior of the main body 1 of the filtration device 100 incorporates a seat to receive the filter cartridge to resist lateral movement. This helps reduce the strain on the preferred fibre membranes.

[0093] Once water enters through the wall of a hollow fibre membrane under the influence of a pressure differential, it is transferred along its tube-like structure to the output.

[0094] As a result, water may enter at any point along the membrane wall and reach the output while also being filtered.

[0095] The preferred fibre membranes have a retention of greater than 99.999995% of bacteria, cysts, parasites and fungi, and greater than 99.999% of viruses from the water. The fibre membranes also remove sediments and other deposits from the water.

[0096] Fibre membranes suitable for use with the present invention are available commercially, for example from SUEZ Water. The hollow fibre ultra-filtration membranes are effective to screen all turbidity, bacteria as well as viruses.

[0097] In a preferred embodiment of the filtration device 100, the length of the preferred fibre membranes is between 30 to 200 cm, preferably 80 cm. For such lengths in the device of the present invention, the preferred filter cartridge incorporates 600 to 800, preferably 650 to 700, fibre membranes, giving an initial flow rate of between 5 to 10 litres/minute, which may be achieved at a pressure differential across the filter of between 10 and 50 kPa (0.1 to 0.5 bar). Each of seven bundles of fibres in the filter cartridge 20 may comprise 96 individual fibres. It is important to provide a reasonable flow rate to encourage users to take filtered water from the filtration device when required, rather than transfer filtered water to a different container for storage, where it would quickly become contaminated. Advantageous flow rates may be achieved where the total surface area provide by the filter membranes is in the region of 3 m.sup.2 to 6 m.sup.2, preferably around 4.6 m.sup.2.

[0098] In FIG. 7 a cut-away section of a filter cartridge 20 for use in a preferred embodiment the present invention is illustrated. The filter cartridge has a plurality of sub-groups (bundles) 61 of filter membranes 611. Each sub-group 61 in the example illustrated has 96 filter membranes 611, however, useful numbers of filter membranes per sub-group can be in the range of 80 to 100 filter membranes per sub-group. Each sub-group may be surrounded by a sheath 612 for holding the sub-group together in a single bundle. This can prevent damage during assembly and hold the sub-group together for increased structural integrity. The sheath 612 may be constructed of a mesh or net or polynet or other rigid or resilient water-penetrable material.

[0099] The filter membranes 611 may be bundled in further groups of seven within each subgroup 61 as illustrated. This configuration allows some spacing to be kept between adjacent membranes, which makes efficient use of space in the filter while allowing a sufficient flow-area for water to reach the membranes and establish the required flow-rate through the filter.

[0100] A spacer (shown at 62) is optionally provided in between sub-groups 61 of filter membranes 611. The spacer may have a central circular or hexagonal portion surrounding a central sub-group and a series of spokes protruding substantially radially from the central portion such that spacing is maintained in between adjacent sub-groups 61 of filter membranes 611. A plurality of spacers may optionally be provided at plural axial locations along the length of filter cartridge 101 to provide support and spacing relatively evenly along the length of the filter cartridge.

[0101] Surrounding the filter membranes is an outer structural member 63 in the form of a substantially cylindrical grid-patterned or mesh-like structure, which may comprise a structure through which water can penetrate to reach the filter membranes 611, while maintaining a structural support around the filter membranes 611.

[0102] Around the structural member 63 is a primary filter here illustrated in the form of an outer filter mesh 64, which acts as a primary filter to prevent silt, dirt and sediment from contacting the filter membranes 611 inside the structural member 63. Filter mesh 64 may be made from cloth or other fibrous material or from a fine plastic mesh having an opening size of around 100microns. The outer filter mesh 64 may comprise activated carbon.

[0103] The fibre membranes 611 may be potted at an open end proximal the tap 5 and sealed and capped at a distal end thereto. A mesh wrap helps hold the fibre membranes together. In a configuration where the filtration device has taps or valves on opposite sides, and/or taps or valves are arranged at opposite ends of a filter cartridge 101, (for example the filtration device 100 may further comprise an output port at second end 1 b of the main body), the fibre membranes 611 may not be capped, but may be open at both ends, such that water entering the fibre membranes 611 can be delivered to either one of the taps or valves at either end of the filter cartridge 101.