WO2011139835A2

WO2011139835A2 - Water treatment device and method of use

Info

Publication number: WO2011139835A2
Application number: PCT/US2011/034327
Authority: WO
Inventors: Thomas Tranfaglia; David Colbert
Original assignee: Global Material Technologies, Inc.; H2O, Inc.
Priority date: 2010-04-28
Filing date: 2011-04-28
Publication date: 2011-11-10
Also published as: WO2011139835A3

Abstract

A water treatment device includes a wire mesh that includes wire that is randomly oriented and a container adapted to hold water, wherein the wire mesh contacts water in the container.

Description

Title

[0001] Water Treatment Device and Method of Use

Background of the Invention

[0002] The present invention relates to the field of water treatment, and in particular to a bactericidal device for producing potable water from water polluted with bacteria.

[0003] Safe drinking water is a basic necessity of life, yet in many parts of the world the only available water may be polluted with bacteria. It has been estimated that over a billion people are currently at risk of drinking harmfully polluted water. Often in these areas no infrastructure exists for delivery of water to homes. Instead water is collected in containers from wells, rivers, lakes, or any convenient source. It is estimated that there are currently about 50 million 20 liter "Jerry Cans" in use for transporting water in Africa alone.

[0004] Collected water can be filtered; however, filters capable of excluding bacteria are expensive and the vast majority of people living in areas lacking infrastructure are poor. The collected water can be treated by the addition of chemical disinfectants to the water, such as chlorine or bromine; however, in addition to being expensive, the storage of such chemicals may be dangerous and the use of such chemicals may result in a taste or smell in the water that will result in lowered use. A device for water treatment is needed to allow water taken from a polluted well, lake, or river to be rendered potable easily and cheaply. The device should be rugged enough for daily use over several years without loss of efficacy. The present invention attempts to solve these problems, as well as others.

Summary of the Invention

[0005] In one embodiment, a water treatment device comprises a wire pad that includes wire that is randomly oriented and a container adapted to hold water, wherein the wire pad contacts water in the container.

[0006] In another embodiment, a water treatment device comprises a wire pad of silver-coated wire, wherein the wire is randomly oriented, and a container having at least a portion of an interior surface thereof coated with a metal selected from the group of metals consisting of copper and alloys of copper, wherein the container holds water and the randomly oriented pad contacts the water. [0007] In a further embodiment, a method of treating water includes the steps of introducing water into a container and exposing the water to a wire pad that includes wire that is randomly oriented.

[0008] In yet another embodiment, a method of treating water includes the steps of introducing water into a container having at least a portion of an interior surface thereof coated with a metal selected from the group of metals consisting of copper and alloys of copper and exposing the water to a wire pad of silver-coated wire wherein the wire is randomly oriented.

Brief Description of the Drawings

[0009] FIG. 1 schematically illustrates an embodiment of a water treatment device in use.

[0010] FIG. 2 A is an illustration of an embodiment of a water treatment device having a pad of wire where the wire is randomly oriented; and FIG. 2B is an enlarged view of a portion of the water treatment device of FIG. 2A; and FIG. 2C is a further enlarged view of the water treatment device of FIGS. 2A and 2B, illustrating an embodiment of a strand of wire; and FIG.

2D is a further enlarged view of the water treatment device of FIGS. 2A and 2B, illustrating another embodiment of a strand of wire.

[0011] FIG. 3A is an illustration of a container; FIG. 3B is an illustration of another container;

FIG. 3C is an illustration of a further container; and FIG. 3D is an illustration of yet another container.

[0012] FIG. 4 is plan view of the water treatment device of FIGS. 2A-2C disposed within the container of FIG. 3A.

[0013] FIG. 5A illustrates an elongated embodiment of a water treatment device; and FIG. 5B illustrates another embodiment of a water treatment device further elongated than the water treatment device of FIG. 5 A.

[0014] FIG. 6A illustrates the water treatment device of FIG. 5A having a porous cover; FIG. 6B illustrates the water treatment device of FIG. 5B having a porous cover.

[0015] FIG. 7A is an illustration of another embodiment of a pad of wire where the wire is randomly oriented; FIG. 7B is an enlarged view of a portion of the pad of wire of FIG. 7A; FIG. 7C is a further enlarged view of the pad of wire of FIGS. 7A and 7B, illustrating a strand of wire; and FIG. 7D is an illustration of a container that forms a water treatment device with the pad of wire of FIGS. 7A-7C. [0016] FIG. 8 illustrates a comparison of E. coli kill rate of an embodiment of a water treatment device with water motion and without water motion.

[0017] FIG. 9 illustrates a comparison of E. coli kill rate of another embodiment of a water treatment device with water motion and without water motion.

[0018] FIG. 10 illustrates a comparison of E. coli kill rate of a silver-plated embodiment of a water treatment device and an unplated embodiment of a water treatment device.

[0019] FIG. 11 illustrates a comparison of E. coli kill rate of a 5 foot rope mesh embodiment of a water treatment device and a 10 foot rope mesh embodiment of a water treatment device.

Detailed Description of the Preferred Embodiments

[0020] Silver possesses properties to keep water safe to drink. Sufficient addition of silver to bacteria-infested water kills the bacteria, the mechanism by which the killing works is not well understood. The water treatment device disclosed herein indicates that silver metal in contact with water is lethal to bacteria, fungi, microbes, parasites, and other microorganisms contained in such water. The silver ions interact with thiol groups and other target sites on amino acids, enzymes, and proteins plays the role of antimicrobial, antifungal, antiparasitic, and anti-protozoa action. The water treatment device shows with data presented hereinbelow (see FIGS. 8 and 9) that E. coli in water that is both in contact with silver and in motion experiences about twice the kill rate of E. coli in silver-contacted water that is not caused to be in motion, all others factors having been held constant in other embodiments.

[0021] The water treatment device provides motion of the infested water with respect to the silver metal in many ways, including for example, but not limited to, stirring and shaking. Motion is a change in position of the water with respect to the water treatment device. In one embodiment, the act of transporting water from one location to another causes the water to be in motion. In another embodiment, transporting a container of water from a well, river, or lake to one's residence puts the water in motion with regard to the container or any silver metal disposed within the container. For example, water transported by carrying, on a bicycle, in or on a self- propelled vehicle, via an animal, on a cart or otherwise transported is in motion with regard to its container and any silver metal disposed therein. Thus, a water treatment device, for example, including a silver metal biocide, effectively delivers silver metal to water in a container to disinfect the water in the container, as the container is being transported at a rate that is greater than if the water is held still. [0022] Such a water treatment device can also disinfect water flowing through a mechanical system, whether the mechanical system is stationary or in motion. In fact, the silver metal biocide can have many industrial, commercial, and/or residential uses. For example, the silver metal biocide may be applied in industrial water chillers, reverse osmosis systems, harvested rainwater treatment, recycled process water treatment, aquaculture, and the like. Commercial and/or residential applications of the silver metal biocide can include rainwater treatment, greywater treatment, fish tanks, hot tubs, and swimming pools, to name a few applications, the number of which is not intended to be limiting as to yet other applications.

[0023] Referring now to the drawings wherein like numerals refer to like parts, FIG. 1 illustrates a potential example for use of an embodiment of a water treatment device 50. Starting with the top left of FIG. 1, the water treatment device 50 is introduced into a container 60. Infested or questionable water 62 (here shown being poured from a second container) is introduced into the container 60 in Step B such that the water treatment device 50 is in contact with the infested water 62. The container 60 containing the infested water 62 in contact with the water treatment device 50 is transported by a user in Step C. Jostling motion caused by carrying or otherwise transporting the container accelerates the bactericidal effect of the water treatment device 50 such that by the time the user gets to his or her destination, the formerly infested water 62 is now potable water 64, or treated water, and safe to drink, as illustrated in Step D. Preferably, the motion of the water relative to the water treatment device is between about between about 0.55 and about 1.10 mm/s. Alternatively, the motion of the water relative to the water treatment device is between about 0.01 mm/s to 100 mm/s. Alternatively, the motion of the water relative to the water treatment device is between about 0.1 mm/s to about 50 mm/s. Alternatively, the motion of the water relative to the water treatment device is between about 0.5 mm/s to about 20 mm/s. The motion of the water relative to the water treatment device takes into account the size of the container 60, the amount of water within the container 60, and the size and weight of the water treatment device 50. The motion of the water relative to the water treatment device 50 may be increased or decreased depending on the amount of bacteria suspected in the water or level of infestation of microbes. The size of the container 60 may be between about 0.1 L and 100 L, alternatively between about 0.5 L and 50 L, alternatively, between about 1 L and 20 L, and the like. [0024] FIGS. 2A-2C illustrate an embodiment of the water treatment device 50. FIG. 2A illustrates a generally pad- shaped mesh 52 of one or more wires 54 that are randomly oriented. For illustration purposes, an exemplary pad-shaped mesh 52 has a mass of about 35 grams (g). Alternatively, the mass is between about 1 and 1000 g, alternatively, the mass is between about 5 and 75 g, alternatively, the mass is between about 10 and 50 g. The mass of the mesh 52 may be adjusted according to the amount of water to be treated and the level of contaminants. The shape of the mesh 52 may be generally cuboidal, polygonal, square, rectangular, tubular, rope-like shape, and the like. The shape of mesh 52 may be selected according to the type of container 60 as to fit securely within the container and allow for sufficient motion of the water contained therein.

[0025] Referring to FIGS. 2C and 2D, the wires 54 are comprised of a metal that is partially or completely coated with silver. The diameter of the wire 54 may comprise an average cross- sectional diameter d ranging between about 10 microns and 12 mm. A superfine wire 54 includes an average cross-sectional diameter d of 25 microns. An extra fine wire 54 includes an average cross-sectional diameter d of 35 microns. A very fine wire 54 includes an average cross- sectional diameter d of 40 microns. A fine wire 54 includes an average cross-sectional diameter d of 50 microns. A medium wire 54 includes an average cross-sectional diameter d of 60 microns. A medium coarse wire 54 includes an average cross-sectional diameter d of 75 microns. A coarse wire 54 includes an average cross-sectional diameter d of 90 microns. An extra coarse wire 54 includes an average cross-sectional diameter d of 100 microns. In one embodiment, the wire 54 may include an irregular cross-section and rough outer surfaces with projections and fissures formed along the outer surfaces. The irregular cross-sections vary continuously along the length of the resulting metal wire to provide generally asymmetrical metal fibers in the longitudinal and horizontal direction. The nature of the wire 54 provides increased surface area of the wire for silver coatings.

[0026] In one embodiment, the silver partially coats the wire 54, as illustrated in FIG. 2C, by a plurality of coated portions 56 indicated by the horizontal cross-hatching and a plurality of uncoated portions 58 indicated by the vertical cross-hatching. Suitable methods for silver coating the wire 54 include electroplating and chemical plating, and the like. The silver may be applied in any pattern as desired to partially plate the wire 54. Suitable methods for creating a desired coating pattern include photo- selective plating, masking, brush plating, and the like. In another embodiment, the silver completely coats the wire 54, as illustrated in FIG. 2D, by the coated portion 56 extending the entire length of the wire 54, as indicated by the horizontal cross- hatching. Alternatively, the wire 54 may include the coated portion 56 extending at least a portion of the length of the wire, alternatively, the wire 54 may include the coated portion 56 extending at least between about 10 to 99% of the length of the wire 54. The coating of silver may be adjusted on the wire 54 to include a total silver amount on the mesh 52. The total silver coating amount may be between 10 and 1000 milligrams (mg). Alternatively, the total silver coating amount may be between 20 and 500 mg. Alternatively, the total silver coating amount may be between 5 and 100 mg. The total silver coating may be affected by the thickness of the coating. The thickness of the silver coating may be between 0.1 μιη and 10 mm. The silver coating may also include a surface roughness or smooth exterior coating. Alternatively, the total silver coating amount and thickness may be selected according to the amount of bacteria in the contaminated water.

[0027] In some embodiments, wires 54 of the pad- shaped mesh 52 are comprised of copper, aluminum, zinc, tin, gold, brass, stainless steel, or other metals. In other embodiments, the wires 54 are comprised of an alloy of copper, zinc, aluminum, tin, stainless steel, or other metals, such as, by way of example and not limitation, a variety of bronze or brass. The selection of how much exposed surface area of silver and the underlying copper or alloy of copper can be preselected by selection of the ratio of total area of the covered portions 56 to the uncovered portions 58.

[0028] In other embodiments, a non-metallic porous or stranded material is used to form the pad- shaped mesh 52. Suitable examples of such a non-metallic porous or stranded material include by way of example and not limitation, ceramics, wood, nylon, wool, cotton, and other natural and synthetic porous or stranded materials. Suitable methods for plating or coating the non- metallic porous or stranded material include chemical plating, ultrasound irradiation, powder coating, and the like.

[0029] The water treatment device 50 is designed for use with any container known in the art that can hold water in contact with the water treatment device 50. FIGS. 3A-3D illustrate a variety of containers 60 adapted to hold water. The container 60 may be rigid or flexible and may, for example, take the form of a bucket as in FIG. 3A. The container may include a lid 66 with or without a cap 67 for closing the container 60. The container may take the form of a bottle as in FIG. 3C or any container including a narrowed neck portion mounted on a wider body portion. The container 60 may take the form of a "Jerry Can," as known in the art and illustrated in FIG. 3D, and including a pour spout 68 and a carrying handle 69. The container 60 may take any form suitable for holding water and having an opening large enough for the pad- shaped mesh 52 to be introduced into the container 60, for example, as indicated by the arrow 70, and as known in the art. The container 60 in this embodiment may be made of any material suitable for making a flexible or rigid container such as, by way of example and not limitation, wood, plastic, metal, ceramic, bone, leather, and the like. The container 60 when included with flexible material may be flexed to alter the internal volume of the container 60 as to displace any fluid or water contained therein. Such flexing of the flexible container 60 may provide for further motion of the water to interact with the water treatment device 50 for water decontamination and the like.

[0030] FIG 4 illustrates the water treatment device 50 disposed within the container 60. Referring again to FIG. 1, in operation, the water treatment device 50 is introduced into the container 60 and polluted or questionable water 62 to be treated is introduced into the container 60 and so as to contact the water treatment device 50. The anti-bacterial action of the partially or completely silver-coated wire 54 acts to kill bacteria in the water.

[0031] In one embodiment, after a time period, for example, from about 10 minutes to about 24 hours, the treated water is safe to drink. In another embodiment, after a time period, for example, from about 10 minutes to about 6 hours, the water is safe to drink. In a further embodiment, after a time period of, for example, from about 10 minutes to about 2 hours, the water is safe to drink. In other embodiments, after a time period, for example, from about 10 minutes to a time between about 10 minutes and about 1 hour, the water is safe to drink, which time period can be about 15 minutes, about 20 minutes, about 30 minutes, about 40 minutes, or about 50 minutes. These indicated time frames for contact of the water 62 and the water treatment device 50 are provided as alternative examples of useful steps in the inventive method set forth and claimed herein, and are not intended to be limiting of said claims. If the water hardness is above 500ppm, then an increased time period should be used for water treatment. Water hardness is defined as the mineral content of water, where high water hardness includes high concentrations of Ca²⁺ and Mg²⁺ ions. As yet a further example, it is contemplated that the water treatment device 50 and water 62 can be in contact indefinitely in, for example, a large pottery jug or a cistern designed for long-term water storage.

[0032] The water treatment device 50 may be manufactured to have any shape or size as desirable and as known in the art. For example, the water treatment device 50 may resemble a pad having a slightly elongated rectangular shape, as illustrated in FIG. 2 A. Alternatively, in other embodiments, the water treatment device 50 can take on a more elongated rope-like form as shown as rope-shaped mesh 52A and 52B, as illustrated in FIGS. 5A and 5B, respectively. In one embodiment, the shape of the water treatment device 50 is a factor in bactericidal efficacy. A rope-shaped mesh 52B can extend from an opening of the container 60, for example, the spout 68 of the Jerry Can illustrated in FIG. 3D, into and around an interior of the container 60. In contrast to the pad-shaped mesh 52, such a rope-shaped mesh 52B presents a more extended cross-section for contact with the infested water 62 in the container 60, whether the infested water 62 is in motion or stationary. The rope-shaped mesh 52B may be cylindrically disposed within the container as to provide maximum contact area with the contaminated water. The length of the rope-shaped mesh 52B may be selected according to the size of the container and may be between about 0.5 m to about 100m, alternatively, between about 1 to about 50 m, alternatively, between about 5 and 20 m. Data presented hereinbelow (see FIGS. 11 and 12) suggest that an extended cross-section of a wire mesh is a contributing factor in determining the E. coli kill rate.

[0033] Regardless of the shape or size, the water treatment device 50 may include a single mesh 52, 52A, 52B or may include a plurality of meshes. In embodiments having a single mesh 52, 52A, 52B, one or more of the wires 54 can be made from a first material, for example, silver, and one or more of the wires 54 can be made of a second material, for example, copper or an alloy of copper. As yet a further alternative embodiment, the first material can be any material, metallic or non-metallic, to or by which silver material is suitably attached or coated or encased and to or by which silver has been attached or coated or encased, such as, for example, steel, wool, nylon, copper, aluminum, zinc, or an alloy of copper, zinc, aluminum and the like that has been coated with silver or in which silver has been included in a manner such that the silver has a surface that is not encased by the first material.

[0034] In embodiments having a plurality of meshes, one or more of the meshes can be made from a first material, for example, silver or a silver coated material, and one or more of the meshes can be made of a second material, for example, copper or an alloy of copper. The selection of how much surface area of each component metal making up the water treatment device 50 can be pre-selected by selection of the ratio of meshes or wires of each metal used to make the water treatment device. The use of a second metal and the selection of the ratio of surface areas of the metals may be factors in the efficacy of other embodiments of a water treatment device discussed hereinbelow.

[0035] In another embodiment of a water treatment device 75, one or more meshes 52, 52A, 52B made up of wires 54 are encased in a porous sleeve or cover 77, as illustrated in FIGS. 6A and 6B. The porous cover 77 may be useful in protecting the mesh or meshes 52, 52A, 52B from being clogged with dirt and dust, or in preventing portions of the mesh or meshes 52, 52A, 52B from breaking off into the container with repeated use. The porous cover 77 may also be useful as providing a convenient surface to grab. The porous cover 77 may be made from any material as known in the art that allows the passage of water therethrough. For example, suitable materials for the porous cover include, by way of example and not limitation, a plastic or polypropylene fabric or cloth through which water can pass that is woven from a synthetic or natural fiber. The porous cover 77 may include an attachment portion 79, which may be attached to the top of the container. The attachment portion 79 may be rope or line, or chain or link as to attach to a hook portion on the container or inside the lid of the container. The attachment portion 79 may further provide for the agitation or motion of water by swinging in a pendulum motion. The length of the attachment portion 79 may be increased or decreased as to affect the pendulum motion of the meshes.

[0036] In some embodiments, design of a water treatment device may benefit from knowledge of or control over the concentration of silver ions in the water. The water treatment device 50 may be coupled to a silver ion detector, sensors, ion-exchange resins, or chromatography paper that turns a different color when the concentration of silver is above a particular threshold. Although silver metal is not very soluble in water, silver metal introduced into a volume of water will produce an equilibrium concentration of silver ions that depends on the purity of the water including the concentrations of organic and other inorganic ions. Silver ions are not known to be toxic to humans. In fact, the United States Environmental Protection Agency (USEPA) reports that the "critical effect in humans ingesting silver is argyria, a medically benign but permanent bluish-gray discoloration of the skin." USEPA Integrated Risk Information System: silver; CASRN 7440-22-4. Nevertheless, the USEPA and some other national agencies have decreed an upper safe limit for the concentration of silver ions in drinking water. For example, the USEPA upper limit is set at 100 parts per billion (ppb).

[0037] In an alternative embodiment, the addition of a second metal to water in contact with silver metal can change the concentration of silver ions from what the silver ion concentration was before adding the second metal. For example, the introduction of copper or an alloy of copper into water in contact with silver metal decreases the concentration of silver ions in the water. Alternatively, the second metal may be below the silver coating on the wire, such that when the silver coating diffuses, the second metal on the wire is copper that generates copper ions to decrease the concentration of the silver ions in the water that have diffused into the water. Thus, the thickness of the silver coating may be adjusted to be optimized to a level just above 100 ppb and be equilibrated when the silver coating has diffused into the water and exposing the copper metal underneath the silver coating. Without intending to be bound by any theory, the concentration of silver ions in the water is believed to decrease when copper metal is introduced into the water, because copper serves as a reducing agent that provides an excess of electrons as copper ions enter the water. The reducing agent (or reductant or reducer) is the element or compound in a reduction-oxidation (redox) reaction that donates an electron to another species, and in case the electrons need to be donated to silver ions. The excess of electrons then reduces the silver ions to silver metal. The silver metal may be precipitated and removed from the container before the treated water is provided for human consumption. Such lowering of the concentration of silver ions may be useful in a water treatment device applied to containers for long term storage of potable water for keeping the concentration of silver ions at or below 100 ppb. Any of the embodiments described hereinabove with regard to FIGS. 1-6B may take advantage of a second metal acting as a reducing agent to a first metal, where the second metal is included to control the equilibrium concentration of the silver ions.

[0038] Again, not intending to be bound by any theory, the ratio of exposed surface areas of the first and second metals may be predetermined to control the equilibrium concentration of silver ions in the water with which the first and second metals are in contact. The higher the proportion of exposed silver metal to the non-silver metal that serves as a reducing agent relative to the silver ions in a volume of water, the higher the equilibrium concentration of silver ions in that volume of water. In embodiments that are designed along the lines of using a first and second metals for the purpose of minimizing the silver ion concentration in water, the second metal (i.e., the non-silver metal) is one or more of copper, zinc, aluminum, manganese, or a copper alloy.

[0039] An embodiment of a water treatment device 100 having a second metal to act as a reducing agent is illustrated in FIGS. 7A-7D. In this embodiment, a mesh 102 includes one or more randomly oriented wires 104 that is comprised of a metal and entirely coated with a coat of silver 106, as illustrated by the enlarged view of the wire 104 in FIG. 7C. The metal may be comprised of any metal to which silver can be attached; in certain embodiments, the metal is copper or an alloy of copper.

[0040] The water treatment device 100 includes a container 108, illustrated for simplicity as a bucket in FIG. 7D. The container 108 includes at least a portion 110 of an interior surface 112 thereof that is coated with or comprised of copper, an alloy of copper, zinc, aluminum, manganese, or another metal or alloy that is known to be a reducing agent. The container 108 may otherwise be identical to the container 60 described hereinabove with regard to FIGS. 3A- 3D.

[0041] In operation, the water treatment device 100 works the same as the water treatment device 50, 75. Water to be treated is added to the container 100 and the mesh 102 is introduced into the water. The anti-bacterial action of the mesh 102 acts to kill bacteria in the water, and after an appropriate time period, for example, from about 1 hour to about 24 hours or more preferably from about 1 hour to about 6 hours, or yet more preferably from about 1 hour to about 2 hours, the water, now treated, is safe to drink. In another embodiment of the water treatment device 100, the time period used ranges from about 10 minutes to about 2 hours; in yet another embodiment, the time period used ranges from about 10 minutes to about 90 minutes, from about 10 minutes to about 60 minutes, from about 10 minutes to about 45 minutes, from about 10 minutes to about 30 minutes. In yet another embodiment of the water treatment device 100, the time period used is at least about 10 minutes. The selection of the surface area of each of the mesh 102 and the portion 110 of the interior surface 112 can be pre- selected as desired to make the water treatment device 100 such that it imparts an effective level of silver ion concentration in the water that remains below the EPA recommended 100 ppb.

[0042] Any water treatment device 50, 75, 100 may be cleaned in an appropriate cleaning solution, rinsed with water, such as to restore the water treatment devices treating ability. The cleaning solution may be acidic solution, including, but not limited to, fruit juice, vinegar, and the like.

[0043] The following Examples are provided to exemplify further the present invention and should not be interpreted as limiting claims thereto. Materials and chemicals used are common in the art and available from many vendors. Tests were conducted under a wide range of operating conditions including variations in container volume, water motion, mesh size, mesh geometry, wire gauge, wire plating, and mesh covering.

[0044] Example 1: The following experiment illustrates the phenomenon of killing bacteria in water that is in contact with silver metal, with and without water movement relative to the silver metal.

[0045] To prepare a sample of water for testing, a container is filled with distilled water in an amount that is 100 milliliter (ml) less than the capacity of the container (in the instant case, 18.4 liters). A 100 ml aliquot of stationary phase E. coli that had been prepared by an overnight culture in Luria broth (a standard, fully nutritive medium for E. coli) under standard conditions is added to the water in the container. The 18.5 liter container, now including E. coli, is left overnight on a rotary shaker under standard conditions to allow the E. coli to multiply. At this point, the 18.5 liter of infested water is ready for testing.

[0046] Before adding any silver metal to the 18.5 liter container, a 100 μΐ sample of the now E. co //-infested water is removed from the container. The 100 μΐ sample of the culture in the 18.5 liter container is serially diluted for four 1:10 dilutions by adding it to 900 μΐ of Luria broth in a first test tube, thereby creating a l:10-diluted sample; taking a 100 μΐ sample from the first test tube and adding it to a second test tube that contains 900 μΐ of Luria broth, thereby creating a

1:100 diluted sample; and so on twice more, thereby creating 10 -^"3 and 10 -^"4 dilutions in test tubes three and four. A 100 μΐ aliquot is taken from each of the dilution series and spread out on agar containing nutritive media for the E. coli in a Petri dish, and allowed to grow overnight at standard conditions. Subsequently, the number of E. coli colonies (referred to as Colony Forming Units or CFUs) on the media is counted on those dishes that contain between about 10 and 100 CFUs. The number of CFUs is then multiplied by the inverse of the dilution factor for the source of the bacteria growing on the selected Petri dish. The resulting number is then recorded as a measure of the number of CFUs of E. coli that were present in the 18.5 liter container at time zero (t=0). [0047] In a first series of tests, a pair of fine-gauge unwound, uncovered, silver-plated bronze mesh pads having a total weight of about 73 grams are introduced into the 18.5 liter container of E. coli infested water at time, t=0. The water in the container is left undisturbed. After an amount of time has passed, for example, 30 minutes, a 100 μΐ sample of water is removed from the 18.5 ml container. The 100 μΐ sample is subjected to the serial dilutions and counting procedure described hereinabove to yield a measure of the number of CFUs in the 18.5 liter container at 30 minutes. After another amount of time has passed where the water is left undisturbed, for example, 60 minutes, another 100 μΐ sample is removed from the 18.5 liter container and subjected to the serial dilution and counting procedure to yield a measure of the number of CFUs in the 18.5 liter container at time, t=60 minutes. At t=120 minutes, the sample removal, serial dilution, and counting process for the undisturbed water is repeated to yield a measure of the number of CFUs in the 18.5 liter container at time, t=120 minutes.

[0048] The numbers of CFUs measured in the first series of tests, and generally in all of the tests, are very large numbers that are difficult to visualize on a plot vs. time. The magnitude of the measured numbers also makes it inconvenient to make comparisons of killing efficiency between test runs. Therefore, a useful simplification of the measured numbers is to take the base ten logarithm of each number to yield a data point for plotting. This series of data points are plotted in FIG. 8 as the "No Motion" series.

[0049] In a second series of tests, apparatus and methodology nearly identical to that used in the "No Motion" series is used to generate data points at 0, 10, 30, and 60 minutes. The only difference in the procedure is that the infested water in a second 18.5 liter container is stirred via rotating paddles at about 100 revolutions per minute (rpm) between acquisition of samples. This second series of data points are plotted in FIG. 8 as the "100 rpm stir" series.

[0050] To summarize the data series plotted in FIG. 8, the "No Motion" series represents data collected in motionless water, whereas the "100 rpm" series represents data collected in water that is stirred at about 100 rpm. The "No Motion" series demonstrates a 7.02 log kill of about 10,462,000 CFU of E. coli in 120 minutes. In comparison, the "100 rpm" series demonstrates a 6.79 log kill of about 6,131,000 CFU of E. coli in only 60 minutes. Thus, the rate of kill of E. coli with water motion is about twice the rate of kill of E. coli without water motion. [0051] Example 2: The following experiment illustrates the phenomenon of killing bacteria in water that is in contact with silver metal, with and without water movement relative to the silver metal.

[0052] This example follows the methodology as described hereinabove for Example 1. However, in this example, a first container having a volume of 3 liters is prepared for testing using non-chlorinated tap water instead of distilled water. In this example, a single fine gauge wound, covered, silver-plated bronze mesh pad weighing about 38.4 grams is introduced into the first 3 liter container of E. coli infested, non-chlorinated tap water. In a third series of tests, samples from the first 3 liter container are acquired and data points generated using the procedure described in Example 1 above at time, t=0, 30, 60, and 120 minutes, where the E. coli infested water is left undisturbed between acquisition of samples. This series of data points are plotted in FIG. 9 as the "No Motion" series.

[0053] In a fourth series of tests, using nearly identical apparatus and methodology as for the third series of tests, data points are generated at 0, 10, 30, and 60 minutes. The only differences in apparatus and procedure of the fourth series of tests as compared to that of the third series of tests is that the silver-plated bronze mesh pad weighs about 37 grams and the E. coli infested water in a second 3 liter container is stirred via rotating paddles at about 200 rpm for a ten- minute period between acquisition of samples. This fourth series of data points are plotted in FIG. 9 as the "200 rpm, 10 minutes" series.

[0054] To summarize the data series plotted in FIG. 9, the "No Motion" series represents data collected in motionless water, whereas the "200 rpm, 10 minutes" series represents data collected in water that is stirred at about 200 rpm, for 10 minutes between sample acquisitions. The "No Motion" series demonstrates a 4.36 log kill of about 19,863,000 CFU of E. coli in 120 minutes. In comparison, the "200 rpm, 10 minutes" series demonstrates a 3.77 log kill of 6,131,000 CFU of E. coli in only 60 minutes. Again, the rate of kill of E. coli with water motion is about twice the rate of kill of E. coli without water motion.

[0055] Example 3: The following experiment illustrates the efficacy of killing bacteria in water that is in contact with silver-plated bronze mesh versus water that is in contact with unplated bronze mesh.

[0056] An interesting and unexpected result of the testing is illustrated in the comparison of data in FIG. 10. In this example, the apparatus and methodology are nearly identical as that described above for sample preparation, sampling, and data generation, with the following exceptions. A "Plated" series of data is collected using a single fine gauge unwound, uncovered, silver-plated bronze mesh pad introduced into a first 3 liter container of E. coli infested, reverse- osmosis-treated water. An "Unplated" series of data is collected using a single fine gauge unwound, uncovered, unplated bronze mesh pad introduced into a second 3 liter container of E. coli infested, reverse-osmosis-treated water. The silver-plated mesh weighs about 37 grams and the unplated mesh weighs about 31.7 grams. Both containers are stirred continuously at about 500 rpm.

[0057] Referring to FIG. 10, the "Plated" series demonstrates a 6.91 log kill of about 8,164,000 CFU of E. coli in 10 minutes. In comparison, the "Unplated" series demonstrates a 7.38 log kill of 24,192,000 CFU of E. coli in 20 minutes. It is an unexpected result that the "unplated" series demonstrates about the same rate of killing of E. coli as that of the "Plated" series. This result taken together with the difference in kill rates between both the data series in FIG. 10, measured at 500 rpm continuous stir, and the kill rates of the test series in FIGS. 8 and 9, also supports the discovery that motion of the infested water with respect to the wire mesh is a large factor in determining the E. coli kill rate.

[0058] Example 4: The following experiment illustrates the efficacy of killing bacteria in water that is in contact with a 5-foot long mesh versus water that is in contact with a 10-foot long mesh.

[0059] This example utilizes essentially the same apparatus and methods as described hereinabove, with the following exceptions. FIG. 11 is a comparison of a series of E. coli kill data for a 5 foot medium gauge silver-plated bronze mesh rope and a series of E. coli kill data for a 10 foot medium gauge silver-plated bronze mesh rope. Both series of tests are conducted in an 18.5 liter container of E. coli infested reverse-osmosis-treated water stirred continuously at 300 rpm. The 5 foot long mesh rope weighs about 87 grams and the 10 foot long mesh rope weighs about 157.5 grams. Each rope is covered in an identical porous polypropylene covering. The "5 foot rope mesh" series demonstrates a 4.66 log kill of about 2,046,000 CFU of E. coli in 120 minutes. In comparison, the "10 foot rope mesh" series demonstrates a 6.00 log kill of about 991,000 CFU of E. coli in 120 minutes. The higher kill rate of the 10 foot rope mesh suggests that the effective cross-sectional area of a wire mesh in contact with E. coli infested water is a contributing factor in determining the E. coli kill rate of the wire mesh. [0060] Example 5: The following experiment illustrates the efficacy of killing bacteria in water that is water flowing at various flow rates through silver-plated bronze meshes.

[0061] Preparation, sampling, CFU measurement, and data generation in this example follow the same procedure as that described hereinabove for the previous examples. However, in this example, time is not a factor because a first measure of the number of CFUs was taken in water before flowing through a mesh and a second measure of the number of CFUs is taken in the water after flowing through the mesh.

[0062] In a first series of flow tests, E. coli infested, de-chlorinated tap water is introduced into a 2" diameter cylinder and allowed to drain through a single fine gauge silver-plated bronze mesh weighing about 34 grams. The 2" flow test demonstrates a 1.75 log kill for E. coli infested water passing through the silver-plated bronze mesh, reducing the E. coli from about 1,374,000 CFU to about 24,192 CFU (a 98.2% reduction). In a second series of flow tests, E. coli infested water is introduced into a 1" diameter cylinder at about 1/16^th of the volumetric flow rate of the infested water introduced into the 2" diameter cylinder, with all other factors equal. The 1" flow test demonstrates about a 6 log kill of E. coli for infested water passing through the silver-plated bronze mesh.

[0063] Because the 2" diameter cylinder has four times the area of the 1" diameter cylinder, 1/16^th the volumetric flow rate through the 1" diameter cylinder yields 1/4^ώ the flow velocity through the 1" diameter cylinder as compared to the 2" diameter cylinder. Not to be held to any theory, it is contemplated that the much higher demonstrated kill rate of the 1" flow test may be attributable to the higher residence time of the E. coli infested water flowing through the mesh of the 1" diameter cylinder at 1/4^ώ the speed of the E. coli infested water flowing through the 2" diameter cylinder. Further data indicates that the best E. coli kill rates are achieved in water flowing at a rate of between about 1 and about 2 liters/hour (between about 0.55 and about 1.10 mm/s through a 1" diameter cylinder). One test series utilizing the above methodology and a fine gauge 37 gram mesh in de-chlorinated tap water flowing through the mesh at 1.3 liters/hour (about 0.71 mm/s through a 1" diameter cylinder) demonstrates a 7.38 log kill of about 24,192,000 CFU of E. coli in only 10 minutes.

[0064] The present invention should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention. Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the present specification.

Industrial Applicability

[0065] A water treatment device is presented that conveniently and economically treats water infested with bacteria and other biological pollutants. The water treatment device is especially suitable for use in rural or undeveloped areas of the world where a safe supply of drinking water is problematic.

[0066] While the present invention has been described with reference to its preferred embodiments, those of ordinary skill in the art will understand and appreciate that variations in materials, dimensions, geometries, and fabrication methods may be or become known in the art, yet still remain within the scope of the present invention.

Claims

CLAIMS: We claim:

1. A water treatment device, comprising:

a wire mesh including wire that is randomly oriented; and

a container adapted to hold water, wherein the wire mesh contacts water in the container.

2. The water treatment device of claim 1, wherein the wire mesh includes silver-coated wire.

3. The water treatment device of claim 1, wherein the wire of the wire mesh comprises copper.

4. The water treatment device of claim 3, wherein the wire of the wire mesh comprises an alloy of copper.

5. The water treatment device of claim 1, wherein the wire mesh has a rope-like shape.

6. The water treatment device of claim 1, wherein the wire mesh is encapsulated by a porous cover.

7. The water treatment device of claim 1, wherein the wire mesh is configured to be in motion relative to the container.

8. A water treatment device, comprising:

a wire mesh of silver-coated wire that is randomly oriented; and

a container having at least a portion of an interior surface thereof coated with a metal selected from the group of metals consisting of: copper and alloys of copper, wherein the container holds water and the randomly oriented mesh contacts the water.

9. The water treatment device of claim 8, wherein the wire mesh has a rope-like shape.

10. The water treatment device of claim 8, wherein the wire mesh is encapsulated by a porous cover.

11. A method of treating water, comprising the steps of:

introducing water into a container; and

exposing the water to a wire mesh including wire that is randomly oriented.

12. The method of treating water of claim 11, wherein the wire mesh includes silver-coated wire.

13. The method of treating water of claim 11, wherein the wire of the wire mesh comprises copper.

14. The water treatment device of claim 13, wherein the wire of the wire mesh comprises an alloy of copper.

15. The water treatment device of claim 11, further comprising the step of causing the water to be in motion relative to the wire mesh.

16. The water treatment device of claim 15, further comprising the step of causing the water to be in motion relative to the wire mesh for a predetermined period of time.

17. The water treatment device of claim 16, wherein the predetermined period of time is greater than or equal to 30 minutes.

18. The water treatment device of claim 16, wherein the predetermined period of time is greater than or equal to 90 minutes.

19. The water treatment device of claim 15, further comprising the step of causing the water to be in motion relative to the wire mesh by transporting the container.

20. The water treatment device of claim 19, wherein the step of transporting the container comprises carrying the container while walking.

21. The water treatment device of claim 19, wherein the step of transporting the container comprises carrying the container on a self-propelled vehicle.

22. The water treatment device of claim 19, wherein the step of transporting the container comprises carrying the container on a human-powered vehicle.

23. The water treatment device of claim 19, wherein the step of transporting the container comprises carrying the container via an animal.

24. A method of treating water, comprising the steps of:

introducing water into a container having at least a portion of an interior surface thereof coated with a metal selected from the group of metals consisting of: copper and alloys of copper; and

exposing the water to a wire mesh of silver-coated wire that is randomly oriented.

25. The water treatment device of claim 24, further comprising the step of causing the water to be in motion relative to the wire mesh.

26. The water treatment device of claim 25, further comprising the step of causing the water to be in motion relative to the wire mesh for a predetermined period of time.

27. The water treatment device of claim 26, wherein the predetermined period of time is greater than or equal to 30 minutes.

28. The water treatment device of claim 26, wherein the predetermined period of time is greater than or equal to 90 minutes.

29. The water treatment device of claim 25, further comprising the step of causing the water to be in motion relative to the wire mesh by transporting the container.

30. The water treatment device of claim 29, wherein the step of transporting the container comprises carrying the container while walking.

31. The water treatment device of claim 29, wherein the step of transporting the container comprises carrying the container on self-propelled vehicle.

32. The water treatment device of claim 29, wherein the step of transporting the container comprises carrying the container on a human-powered vehicle.