Patent Publication Number: US-6905598-B2

Title: Porous grog composition, water purification device containing the porous grog and method for making same

Description:
Continuation-in-Part of Prior Application No. 09/692,203 filed Oct. 20,2000 now U.S. Pat. No. 6,537,939. 
    
    
     BACKGROUND OF THE INVENTION 
     (i) Field of the Invention 
     The present invention relates to a novel porous grog composition. Further, the present invention relates to a water purification filter and water purification device employing the novel porous grog composition. Additionally, the present invention relates to a method of making the novel porous grog composition and a method for employing the same in a water purification filter and water purification device. 
     (ii) Discussion of Related Art 
     Due to worldwide growth in population and industrialization, along with natural disasters, world supplies of safe drinking water are dwindling. Key pollutants that pose a threat to humans via polluted water consumption are pathogens (bacteria and viruses) and organics. Additionally, water resources may contain suspended material, dissolved solids, bacteriological contaminants, and biological contaminants. Conventional water filters are commonly used in American households to remove water impurities and provide cleaner, more aesthetically pleasing drinking water. However, there are many disadvantages that make these filters difficult to use, especially in developing countries. Typically, such filters are expensive, bulky, difficult to install and replace, and cumbersome to use. Further, most filters available in the United States are not designed to remove pathogens because it is assumed that the water is pathogen free. With regard to available earthenware, most earthenware products are not porous enough to be adequately permeable to water or, if they are permeable, the water flow rate through them is too small to make them practical as water filters. 
     A number of ceramic water filters are known in the art. These filters typically are composed of clay and sawdust (which is thought by some to turn into charcoal when fired). For example, in the early 1980s, Fernando Mazareigos developed a porous clay filter for the Central American Research Institute for Industry (ICAITI). Since its development, this filter has been introduced and promoted in Central and South America. The body composition of Mazareigos&#39; filter is 50% dry clay and 50% dry sawdust, by volume, of between 35 mesh and 60 mesh. 
     The ceramic water filters known in the art do not make use of porous grog. As such, they have a disadvantage of having a lower permeability. A further disadvantage of filters known in the art is that, in order to achieve an appropriate flow rate, their lower permeability requires that their size be larger. Larger filters have a disadvantage of being more susceptible to breakage which makes shipping from an efficient central production facility difficult and often requires that such filters be created at the site of intended use. 
     As such, there exists a need for a method of filtration which is inexpensive, relatively simple to manufacture, utilizes readily available components and, yet, still provides adequate water filtration. There also exists among earthenware products a distinct need for a composition which can provide the earthenware with an increased permeability and thereby allow smaller, less breakable filters with appropriate flow rates. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the difficulties and problems discussed supra by providing for a composition of, and method for making, a porous grog (i.e., a very porous, pre-fired clay material). The porous grog of the present invention may be used to increase the permeability of earthenware. According to the present invention, the porous grog has a body composition of water, clay and combustible material. The clay may be selected from any fine-grained, firm earth material that is plastic when wet and hardens when heated. The combustible material is selected from any material which burns off during firing to create voids in the fired clay. 
     The resultant pressed body is then fired until the body matures into earthenware or until the pressed body can no longer be readily broken down by water. The earthenware is then crushed to yield granules of porous grog. The voids created during the burning off of the combustible material provide the porous grog with its unique permeability. 
     The present invention also addresses the difficulties and problems discussed supra by providing for a water purification filter employing the porous grog and a method for making same. The water purification filter is inexpensive and relatively simple to produce. Additionally, the water purification filter utilizes material components which are commonly and widely available. Further, it has been found through testing that the water purification filter of the present invention is capable of removing about 99% of particles of all sizes down to about 1.0 micron. 
     The water purification filter has a body composition of water, clay, porous grog and combustible material. The body is allowed to dry to a relatively low moisture content before it is pressed within a set of dies, which resemble a mold. The resultant pressed body is then fired until the body matures into earthenware or until the pressed body can no longer be readily broken down by water. Following firing, silver may be applied to the water purification filter. The present invention further provides for a water purification system employing the water purification filter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a perspective view of an exemplary liquid purification filter embodying the porous grog of the present invention; 
         FIG. 2  is a cross-sectional side view of the liquid purification filter of  FIG. 1 ; 
         FIG. 3  is a cross-sectional side view of an exemplary liquid purification device incorporating the liquid purification filter of FIG.  1  and  FIG. 2 ; 
         FIG. 4  is a cross-sectional bottom view of the liquid purification device of  FIG. 3 ; 
         FIG. 5  is a perspective view, with portions in section, of an exemplary liquid purification system incorporating the liquid purification device of FIG.  3  and FIG.  4 . 
         FIG. 6  is a cross-sectional side view of a further exemplary liquid purification system incorporating the liquid purification filter of FIG.  1  and FIG.  2 . 
         FIG. 7  is a cross-sectional side view of a further exemplary liquid purification system incorporating the porous grog of the present invention. 
         FIG. 8  is a cross-sectional side view of a further exemplary liquid purification system incorporating the liquid purification filter of FIG.  1  and FIG.  2 . 
         FIG. 9  is a perspective top view of the liquid purification system of FIG.  8 . 
         FIG. 10  is a cross-sectional side view of a further exemplary liquid purification system incorporating the porous grog of the present invention. 
         FIG. 11  is a cross-sectional side view of a further exemplary liquid purification system incorporating the porous grog of the present invention. 
         FIG. 12  is a cross-sectional side view of a further exemplary liquid purification system incorporating the porous grog of the present invention. 
         FIG. 13  is a micrograph of the fired purifier medium at 5×. 
         FIG. 14  is a micrograph of the un-fired purifier medium at magnification 20×. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates to a composition for a porous grog (i.e., a very porous, pre-fired clay material). The body composition of the porous grog is a mixture of water, clay and combustible material. The body is fired and the firing causes the combustible material to burn off resulting in a porous earthenware. The porous earthenware may then be crushed to form the porous grog. 
     Clay, as used in this invention, means any fine-grained, firm earth material that is plastic when wet and hardens when heated. The clay utilized by the present invention is plastic and moldable when mixed with water, retains its shape on drying, and becomes permanently hard on heating or firing. Non-limiting examples include white clay, clays that fire reddish, yellow clay, black clay and combinations thereof. Clays that fire reddish can be found almost anywhere in the world, thus making them a convenient and practical source of clay. Therefore, in an embodiment of the present invention, clays that fire reddish are utilized as the clay in the body composition. Preferably, the clay has a mesh size (i.e., number of holes per linear inch of a sieve screen) of at least about 10 mesh. More preferably, the clay has a mesh size of at least about 30 mesh. 
     The combustible material may be any material which burns off during firing to create voids in the earthenware and provide the earthenware with its porosity. Organic materials of plant or animal origin have been found to have properties which provide suitable burn off during firing. Examples of combustible material include, but are not limited to, grain flour, sawdust, sorghum, rice flour, rice husk, millet husk, milled corn cobs, or a combination thereof. In particular, grain flour is a preferred combustible material. Wheat flour is widely prevalent as an inexpensive resource. Thus, in an embodiment of the present invention, wheat flour is used as the combustible material. Preferably, the combustible material has a mesh size from about 100 mesh to about 650 mesh. More preferably, the combustible material has a mesh size from about 250 mesh to about 450 mesh. Most preferably, the combustible material has a mesh size of about 350 mesh. 
     The amount of water, clay and combustible material utilized in the mixture will vary depending upon the amount of porous grog sought and the desired permeability of the porous grog. Generally, in a preferred embodiment, the amount of clay added to the mixture is about 40% to about 80% by weight and the amount of combustible material utilized is about 20% to about 60% by weight. In a more preferred embodiment, the amount of clay added to the mixture is about 50% to about 70% by weight and the amount of combustible material utilized is about 30% to about 50% by weight. In a further preferred embodiment, the amount of clay is about 60% by weight and the amount of combustible material is about 40% by weight. In a most preferred embodiment, the amount of clay is about 63% by weight and the amount of combustible material is about 37% by weight. The amount of water utilized is at least the amount necessary to sufficiently allow a uniform mixing of the clay and combustible material. However, not so much water should be added that the mixture must be allowed to have an unreasonable drying time before it can be pressed. 
     In a preferred method of mixing together the clay and combustible material, water is first mixed with the clay. In an embodiment of the present invention, the clay and water combination is then allowed to stand for about zero to about 24 hours to permit the combination to become sufficiently plastic. In another embodiment of the present invention, the clay and water composition is then allowed to stand for about zero to about six hours to permit the combination to become sufficiently plastic. In a preferred embodiment, the clay and water combination is allowed to stand for about 1.5 hours to about 4.5 hours. In a more preferred embodiment, the clay and water combination is allowed to stand for about three hours. In another embodiment, the amount of time the clay and water composition is allowed to stand depends on the water content of the combination. In this embodiment, the higher the water content the less time is required before the combination is sufficiently plastic. When the clay and water combination is considered to be sufficiently plastic, the combustible material is mixed into the clay and water combination. Mixing alternated with size reduction by breaking the larger particles is helpful to ensure uniform distribution of the combustible material throughout the clay and water mixture. Following mixing, the mixture may be spread out to dry until it has the correct moisture content for pressing. In a preferred embodiment of the present invention, the mixture may be pressed into a form or forms conducive to efficient firing. For example, in one preferred method, the mixture is spread out and allowed to dry until the moisture content of the mixture is less than about 15% by weight. In a more preferred method, the mixture is spread out and allowed to dry until the moisture content of the mixture is about 8-10% by weight. The mixture is then dry pressed into forms or shapes which are conducive to efficient firing. In a preferred embodiment, the dried mixture is pressed into a cylindrical mold, released from the mold and then fired. It has been found through experimentation that disk shapes facilitate stacking in a kiln and allow uniform exposure to heat. 
     After the body composition of water, clay and combustible material has been properly mixed but prior to firing of the composition or disks, it may be necessary for the composition or disks to be allowed to dry to a moisture content appropriate for firing. Preferably, the composition or disks are allowed to dry for about zero to about four days. More preferably, the composition disks are allowed to dry for about two days. 
     Firing is a technique and procedure well known to those skilled in the art. For example, the disks may be fired in a kiln or other similar pottery oven. Kilns and firing technology are well known to those of skill in the art and are well described in literature such as  The Kiln Book, Materials, Specifications and Construction , by Frederick Olsen (Chilton Book Co., second edition, 1983). 
     Firing begins slowly at a preliminary firing temperature. The preliminary firing temperature is a temperature at least great enough to burn off the combustible material but not so great as to cause the or disks to bloat and/or break. The bloating or breakage which occurs at firing temperatures above the preliminary firing temperature inhibits the unique porosity characteristics exhibited in the resultant fired porous grog of the present invention and is in contrast to the objects of the present invention. After the combustible material has burned off, the firing may continue at a temperature higher than the preliminary firing temperature. 
     Firing continues until the body matures into earthenware or until the disks or compositions can no longer be broken down by water. Maturing temperatures and times typically depend upon the properties of the specific kiln, pottery oven or firing device used. However, such properties are usually easily ascertainable by a user and determining the maturing temperature and time particular to a specific firing device does not require undue experimentation by one skilled in the art. Generally, a sufficient temperature is at least about 500° C. and the composition or disks will be fired for at least about three hours. For example, a standard cylindrical red brick kiln is described in  An Improved Bonfire Kiln , by the Organization Intermediate Technology of Kenya. Using such a kiln, the mixture should mature into earthenware after about four to six hours of firing at temperatures up to about 700° C. Following firing, the earthenware is crushed to create granules of porous grog. As the combustible material has been burned off during the firing, the granules of porous grog will contain voids, spaces or air pockets. Maturing temperatures and times also typically depend upon properties of the particular clay material. For example, in an embodiment of the present invention, the maturing temperature and times for the clay material depend upon the amount of iron contained in the clay material. In this embodiment, a higher amount of iron results in a lower maturing temperature and vice versa. 
     The present invention further relates to a water purification filter that can be made using the porous grog. The unique permeability characteristics of the porous grog provide the filter with a greater flow rate than other known earthenware filters while still maintaining a pore size small enough to remove about 99% of particles of all sizes down to about 1.0 micron. One reason that the porous grog improves the permeability is that the clay material of the present invention is generally “damp pressed” (i.e., pressed with a relatively low water content). Because the clay material has a low water content, the particles are pushed apart by a kind of friction. By contrast, the clays that are popularly used for throwing and handbuilding ceramics are moist clays of around 30% water content. For these moist clays, the particles are pulled together more tightly and the water flow rate through the fired clay material is thereby inhibited. 
     To produce the water purification filter, porous grog is mixed with water, clay and combustible material. This mixture is pressed in a set of dies, removed and fired to create an earthenware water purification filter. In a preferred embodiment, upon removal from the mold, the water purification filter is cleaned of any seams resulting from the set of dies and may also be burnished (i.e., the surface of the filter may be smoothed by rubbing with a hard object to give a finish with a smooth effect). It has been found through experimentation that burnishing the filter improves the strength of the filter. 
     As with the body composition of the porous grog, the clay of the water purification filter may be any fine-grained, firm earth material that is plastic when wet and hardens when heated. Additionally, as in the clay of the body composition of the porous grog, the clay utilized in the filter is plastic and moldable when mixed with water, retains its shape on drying, and becomes permanently hard on heating or firing. The clay utilized to make the water purification filter may be of the same type and size as that used in the porous grog. However, the clay utilized in the body composition of the water purification filter does not necessarily have to be of the same type and size as that used in the porous grog. In a preferred embodiment, clays that fire reddish are utilized in the body composition of the water purification filter. 
     As with the body composition of the porous grog, the combustible material may be any material which burns off during the firing of the filter leaving a plurality of spaces, voids or air pockets. The combustible material utilized to make the water purification filter may be of the same type and size as that used in the porous grog. However, the combustible material utilized in the body composition of the water purification filter does not necessarily have to be of the same type and size as that used in the porous grog. In a preferred embodiment, the combustible material is of plant or animal origin. In a further preferred embodiment, the combustible material is grain flour. Wheat flour is available almost everywhere in the world. In addition, wheat flour has proven effective in achieving a good flow rate. Thus, in an even further preferred embodiment, the combustible material is wheat flour. 
     The composition ratios of the clay, porous grog and combustible material will vary depending upon the resultant filter permeability desired. In a preferred embodiment, the composition contains between about 30% and about 60% by weight of clay, between about 30% and about 60% by weight of porous grog and between about 5% and about 20% by weight of combustible material. In a more preferred embodiment, the composition contains about 45% by weight of clay, about 45% by weight of porous grog and about 10% by weight of combustible material. 
     The mesh size of the composition components may be varied depending on the pore sizes of the clay, porous grog and combustible material. Further, the mesh size utilized will be dependent upon the desired resultant permeability of the water purification filter. In a preferred embodiment, the mesh size of the clay is at least about 20 mesh. In a more preferred embodiment, the mesh size of the clay is at least about 30 mesh. 
     Preferably, the combustible material should be of a very fine grain so that the combustible material will burn off during firing and leave a plurality of voids which improve the permeability of the filter. In a preferred embodiment, the combustible material is from about 100 mesh to about 650 mesh. In a more preferred embodiment, the combustible material is from about 250 mesh to about 450 mesh. In an even more preferred embodiment, the mesh size of the combustible material is about 350 mesh. 
     Preferably, the percentage by weight of water added is that amount sufficient to facilitate the uniform mixing of the clay, porous grog and combustible material. In a preferred method, the mixture, following mixing, should be allowed to dry to a water content of about 25% or less by weight before the mixture is pressed. In a more preferred method, the mixture, following mixing, should be allowed to dry to a water content of about 8-10% by weight before the mixture is pressed. This “dry press” material of a body containing a relatively low water content by weight is in contrast to the conventional moist clay of a body containing about 30% water content by weight and is a factor in the increased permeability of the water purification filter. Preferably, following removal from the set of dies and any optional cleaning or burnishing, the filter is allowed to dry before firing. More preferably, the amount of water added to the mixture prior to pressing is such that, following removal from the set of dies, the filter requires not more than about four days to dry before it is ready for firing. 
     Firing of earthenware is a process and technique that is well known to those skilled in the art. Though not required, the filter may be fired using the same procedures, temperatures, firing devices, and time periods as those previously described for the firing of the porous grog. In a preferred method of firing, the temperature is sufficiently high to cause the combustible material to burn off and mature the filter body into earthenware or until the material can no longer be readily broken down by water. Preferably, the firing is at a temperature of at least about 500° C. More preferably, the firing is at a temperature of about 600° C. Even more preferably, the firing is at a temperature of about 700° C. Most preferably, the firing is at a temperature of about 950° C. to about 1100° C. Generally, in a preferred embodiment, the firing will last for at least about three hours to about 24 hours, depending in large part on the size of the kiln. 
     In another embodiment, flour was used as the combustible material. Following mixing, the water was dried off over a two to four hour period for a final water content of about 15%. When mixing the ingredients, it is preferred that the 63 parts of clay powder is first mixed with the 30 parts water and stored in a closed bag over night, helping to restore some of the plasticity which is lost in drying. Preferably, the clay, flour and water are not mixed together at the same time, to prevent the flour from adsorbing all the water prior to its wetting of the clay. 
     Following overnight storage in the plastic bag, the 93 parts clay/water was mixed with the 37 parts of flour. The mixture will initially appear white due to the flour adhering to lumps of clay, however as the lumps are worked out the mixture darkens. After working out the lumps the mixture was pushed through a 10 mesh screen, to assist with the removal of the bigger lumps of clay. The mixture is then spread out on a plastic to dry back to approximately 15% water content. 
     Following the drying, the material is then ready for pressing into grog. Alternatively the material may be stored in a closed bag until needed, however, it is preferably used within 24 hours. A car jack, screw press, or the like, is used to press 1.0 cm. thick disks, appropriate for stacking in the kiln, although any similar device could be used provide it will provide the appropriate amount of pressure. The grog, was then ready for drying in an oven. The temperature is raised slowly to prevent bloating and uneven firing which causes the disks to crumble into powder, from about 100C. to about 500C., the ignition temperature of flour. The burnout of all the flour, is typically indicated by a lot of smoke, and then the kiln may be turned up quickly. The grog disks are then crushed to 10 mesh. While all the strength of a fired earthenware is present, there is less ‘spot welding’ (the bonding of adjacent clay particles, brought about by firing) so crushing the grog disks is difficult. 
     The final composition for the purifier depends to some extent on the clay used. Black clays require less flour than those that naturally occur as red, yellow, and white etc. This is because many black clays already contain between three and five percent organic material (combustible material). In another embodiment where the clay is not black clay the final composition could be 50% grog, 40% clay and 10% flour. In an embodiment where black clay is used the composition may be 50% grog and 50% clay. 
     The purifiers are pressed then fired, colloidal silver applied thereafter. 
     It should be noted that for black clays by comparison with clays that are not black there is a substantial increase in the rate of flow for only a small additional amount of flour. For example, 37% flour to 63% black clay gives double the rate of flow of the non black clay of the same composition. This means that to get the same rate of flow, as per the composition of the grog, the black clay should contain 33% flour to 67% clay. 
     Poor permeability in conventionally formed earthenwares is primarily due to high water content, of about 30 to 35%. On a micro-scale the clay particles are pulled together. By contrast, for ‘dry pressed’ clay compositions on the present invention, where water content is very low, there is a kind of friction on a micro-scale, which pushes clay particles apart providing improved permeability. 
     In the last step of the forming process for appropriate technology filter candles, to insure the green strength necessary to forming at this stage, it is important to increase minimum water content to about 8%. 
     As shown in  FIGS. 13 and 14 , for permeable grog purifiers, looking under the microscope it is clear that with respect to permeability the filter medium is not homogeneous. The micrographs indicate that permeability varies from clump to clump, or particle to particle within the purifier. The most permeable material is the porous grog, the least permeable the plastic clay necessary in facilitating forming. Control over final permeability comes in formulating a mix of materials, an averaging that ends up giving the desired flow, the 1.0 to 1.5 liters per hour necessary to the needs of a small family. The micrographs indicate in one embodiment the thickness of the pores is about 100 microns, although one will appreciate that the thickness may be varied depending on the combustible material utilized and fabrication of the grog. 
     As shown in  FIG. 13 , the micrograph indicates a lot of elongated pores, those primarily involved in bringing about control over the amount of flow. Note that larger white areas indicate pores caused by burnout of a number of combined, grains of flour. Larger dark areas indicate some of the bigger particles of the 10 mesh grog. 
     As shown in  FIG. 14 , the red particles indicate the pre-fired grog, the yellow ones, the un-fired clay composition. Larger white particles show pores, where the composition was not fully compacted during. 
     In large part the control over the rate of flow is aided by the proper mixing of particles of different permeability. However, more homogeneity may be considered desirable. The mixture of a plastic clay material with a glutinous bread like material, all with water, would appear to be unlike any other process in ceramics. 
     In another embodiment, the addition of combustible material would not always be necessary for achieving good flow allowing for simplified fabrication. In this simplified fabrication the grog itself comprises particles that are somewhat separated by their jaggedness. Without being held to the current theory, the applicant hypothesizes that the size and shape of the pores result from the shrinking away that happens between the previously fired and not previously fired particles. This appears to bring about a network of pores that is of primary importance to the permeability. 
     In another embodiment, 60 mesh sawdust can be used instead of the wheat flour. In another embodiment, brick dust, of approximately 30 mesh, is used in place of grog. In this embodiment the brick dust may be combined with flour, sawdust or similar combustible material in order to get the candle composition. 
     In another embodiment, the flow rate, permeability, may be varied by varying the combination of the following criteria, for example: (a) the ratio of flour to clay in the grog composition; (b) the addition of a bit of combustible material (i.e. flour, sawdust, brick dust) in the candle composition (eg. 50% grog, 40% clay, and 10% flour) and/or, (c) the amount of water used in either the grog or the candle compositions. This could normally be 13% to 20% water, but could be as low as 5% and as high as 35 or even 40%. 
     Non-limiting examples of combustible material that may be added to the present invention include: grain flour, sawdust, sorghum, rice flour, rice husk, millet husks, milled corn cobs, powdered earthenware which was previously fired for example brick dust, broken earthenware, and bisque earthenware. It should be understood that these combustible material may be used alone or in combination with other combustible materials. 
     A small amount of silver material may be applied to the earthenware following firing. This silver material causes an oligodynamic action whereby micro-organisms are starved of oxygen and are disabled when they make contact with silver particles. The silver material also has an electric charge which can cause the internal protoplasts of pathogens to collapse. Further, colloidal silver can render pathogens unable to reproduce and can kill parasites while in their egg stage. Thus, silver material, when applied to the water purification filter, acts as a disinfectant in addition to preventing regrowth of bacteria within the purifier wall. The silver material may be applied in its colloidal form or as silver nitrate. When silver nitrate is applied, the filter should be fired for a second time and a combustible should be closed into the kiln with the filter. This results in a reduction atmosphere, which causes the nitrates to burn off. When colloidal silver is applied, there is not a need for a second firing. Through experimentation it has been found that amounts as low as 0.32% silver solution aid effectiveness in providing potable water. Membrane filtration testing for bacteria has shown that the earthenware filter of the present invention when combined with silver material yields purified water with no visible petri dish bacteria. By contrast, the earthenware filter of the present invention without silver material yields purified water with 20 petri dish bacterial colonies. Membrane filtration testing of the unpurified water used in the earthenware filter tests indicate an uncountable number of petri dish bacterial colonies. 
     Referring to the drawings,  FIG. 1  shows a perspective view of a preferred shape for the water purification filter  5 .  FIG. 2  illustrates a cross-sectional side view of the preferred shape for the filter  5 . Methods of creating a mold and die set which can press the body into the preferred shape illustrated in FIG.  1  and  FIG. 2  are well known in the art. 
       FIG. 3  illustrates a cross-sectional side view of a preferred embodiment in which the water purification filter  5 , illustrated in FIG.  1  and  FIG. 2 , may be utilized in a water purifier  10 . The filter  5  is attached to a cap  15 . The filter  5  may be attached to the cap  15  using any suitable connection means known in the art. In a preferred embodiment, the filter  5  is attached to the cap  15  using a small amount of silicone sealant. In another preferred embodiment, the filter  5  is attached to the cap  15  using a wax sealant. In another preferred embodiment, the filter  5  is attached to the cap  15  using a gum sealant. In a further embodiment, the filter  5  is attached to the cap  15  using attachment straps or bolts which secure the filter  5  to the cap  15 . The perimeter of the cap  15  should be sealed so that nonpurified water cannot circumvent the filter  5  and enter at the perimeter of the cap  15 . The cap  15  may be made of any non-toxic material. In a preferred embodiment, the cap  15  is made of non-toxic plastic. In another preferred embodiment, the cap  15  is earthenware. In a preferred embodiment, the interior cavity formed by the filter  5  and the cap  15  may be filled with powdered porous grog. In this embodiment, the powdered porous grog may be coated with silver material. This silver material may be applied in its colloidal form or as silver nitrate. 
     The cap  15  has a hole of sufficient diameter for the insertion of a tube  30 . The tube  30  may be sealed and attached to the cap  15  by any appropriate means known in the art. The tube  30  may be composed of any material which is non-toxic. In an embodiment of the present invention, the tube  30  is composed of iron, brass, or plastic, which include external threads in one fixture. As illustrated in  FIG. 3 , the tube  30  is sealed to the cap  15  with washer  25   a  on the interior side of the cap  15  and washer  25   b  on the exterior side of the cap  15 . Washer  25   a  and washer  25   b  are secured against the interior and exterior sides of the cap  15  by nut  20   a  and nut  20   b . In an embodiment of the present invention, nut  20   a  and nut  20   b  fit on the external threads of tube  30  and tighten washer  25   a  and washer  25   b  against the cap  15 . 
       FIG. 4  illustrates a cross-sectional bottom view of the water purification filter  5  being utilized in the water purifier  10  of FIG.  3 . The cap  15  is shown attached to the filter  5 . The tube  30  is inserted through the cap  15 . The tube  30  is sealed to the exterior side of the cap  15  by washer  25   b . Washer  25   b  is tightened against the exterior of the cap  15  by nut  20   b.    
       FIG. 5  illustrates a perspective view, with portions in section, of a water purifier system  70  utilizing the water purifier  10  of FIG.  3  and FIG.  4 . The purifier  10  is contained in an upper reservoir  40 . The upper reservoir  40  may be covered with an upper lid  35  to protect against evaporation, the elements and debris. The upper reservoir  40  has a hole of sufficient diameter to allow the insertion of the tube  30 . The tube  30  is inserted through a hole in a lower lid  46  and passes into a lower reservoir  50 . In this embodiment, the lower reservoir  50  has a pour spout  65 . 
     Nonpurified water  45  is placed in the upper reservoir  40 . The nonpurified water permeates through the filter  5  of the purifier  10  and exits the tube  30  as exit liquid  55 . The exit liquid  55  falls into the purified liquid  60  which is contained by the lower reservoir  50 . The pour spout  65  may be used to release the purified liquid  60 . 
     In a preferred embodiment, the purifier system  70  is designed to have a flow rate through the purifier  10  of at least about 0.4 liter per hour. In a preferred embodiment, it may be necessary to periodically replenish the amount of nonpurified water  45  in the upper reservoir  40  to maintain a rate of flow of at least about 0.4 liter per hour. 
     While the water purifier system  70  illustrated in  FIG. 5  is shown with one filter  5  and one purifier  10 , the invention is not so limited and may utilize as few as one filter  5  or one purifier  10  up to as many filters  5  or purifiers  10  as will fit in the bottom of the upper reservoir  40 . 
       FIG. 6  illustrates a cross-sectional side view of the water purification filter  5 , illustrated in FIG.  1  and  FIG. 2 , utilized in a further exemplary water purifier system  70 . The water purifier system comprises an upper container  84  which may be removably placed on a lower container  83 . The bottom of the upper container  84  has a hole  88  into which fits the water purification filter  5 . The filter  5  may be sealed against the bottom of the upper container  84  by any suitable sealing means known in the art. In a preferred embodiment, the filter  5  is sealed against the bottom of the upper container  84  using a small amount of silicone sealant. In another preferred embodiment, the filter  5  is sealed against the bottom of the upper container  84  using a wax sealant. In another preferred embodiment, the filter  5  is sealed against the bottom of the upper container  84  using a gum sealant. The perimeter of the edge of the filter  5  that is in contact with the bottom of the upper container  84  should be sealed so that nonpurified water cannot circumvent the filter  5  and enter at the perimeter of the edge of the filter  5 . 
     Nonpurified water is poured into the upper reservoir  80  of the upper container  84 . The nonpurified water permeates through the filter  5  and exits as purified water where it is collected in the lower reservoir  75  of the lower container  83 . The purified water may be obtained from the lower reservoir  75  via a pour spout  65  which is connected through the lower container  83 . In an embodiment of the water purifier system  70  illustrated in  FIG. 6 , the upper reservoir  80  may optionally be covered by a lid to protect the nonpurified water in the upper reservoir  80  against evaporation, the elements and debris. 
     The upper container  84  and the lower container  83  are composed of non-toxic, relatively water impermeable materials. In a preferred embodiment, the upper container  84  and the lower container  83  are composed of earthenware or plastic. The upper container  84  may be composed of the same type of material as the lower container  83 . However, the upper container  84  and the lower container  83  do not necessarily have to be comprised of the same type of material. The upper container  84  and the lower container  83  may be of any shape and capacity which provide a flow rate through the filter  5  of at least about 0.4 liter per hour. In a preferred embodiment, the upper container  84  and the lower container  83  are cylindrical in shape. In a preferred embodiment, the capacity of the lower reservoir  75  of the lower container  83  is of sufficient volume to provide storage of an average daily drinking water requirements of a user or users yet not of so large of volume as to create a purified water retention time which would allow re-breeding of bacteria to occur. 
       FIG. 7  illustrates a cross-sectional side view of an alternatively shaped water purification filter  5  utilized in a further preferred embodiment of the water purifier system  70 . As illustrated, the filter  5  is removably placed on the reservoir  90 . In a preferred embodiment, the filter contains porous grog in an amount between about 40% to about 60%, by weight, of the body composition. Optionally, the filter  5  may be covered with a cap or lid to prevent water contained in the filter  5  from evaporating or becoming further contaminated. 
     Nonpurified water is poured into the filter  5 . The nonpurified water permeates through the filter  5  and exits as purified water which is collected in the reservoir  90 . The purified water may be obtained from the reservoir  90  via a pour spout  65  which is connected through the reservoir  90 . 
     The reservoir  90  is composed of non-toxic, relatively water impermeable materials. In a preferred embodiment, the reservoir  90  is composed of earthenware or plastic. 
       FIG. 8  illustrates a cross-sectional side view of several water purification filters  5 , illustrated in FIG.  1  and  FIG. 2 , utilized in a further preferred embodiment of the water purifier system  70 . The water purifier system  70  illustrated in  FIG. 8  is essentially the same as that shown in FIG.  6  and described above with the exception of the utilization of several filters  5 . Where the water flow rate through a single filter  5  is not sufficient to meet the needs of a user or users, the use of multiple filters  5  has an advantage of increasing the water flow rate through the water purifier system  70 . While the water purifier system  70  illustrated in  FIG. 8  is shown with three filters  5 , the invention is not so limited and may utilize as few as one filter  5  up to as many filters  5  as will fit in the bottom of the upper container  84 . 
       FIG. 9  illustrates a top perspective view of the water purifier system  70  of FIG.  8 . As shown in  FIG. 9 , the filters  5  are positioned in the bottom of the upper container  84 . 
       FIG. 10  illustrates a cross-sectional side view of the porous grog of the present invention utilized in a further exemplary water purifier system  70 . As illustrated in  FIG. 10 , a top layer  205 , a first intermediate layer  210 , a second intermediate layer  215  and a bottom layer  220  are bounded by a container  200  and a retention cap  225 . Optionally, the container  200  may be covered with a cap or lid to prevent the interior of the container  200  from becoming contaminated by foreign particles. Preferably, the container  200  comprises a non-toxic, relatively water impermeable material. In a preferred embodiment, this material is earthenware or plastic. 
     In a preferred embodiment, the top layer  205  comprises particles of sizes from about 4.0 mm to about 6.0 mm. In a more preferred embodiment, the top layer  205  comprises particles of sizes of about 5.0 mm. Preferably, the particles of the top layer  205  comprise stone, porous grog, or a mixture thereof. 
     In a preferred embodiment, the first intermediate layer  210  comprises particles of sizes from about 0.5 mm to about 1.5 mm. In a more preferred embodiment, the first intermediate layer  210  comprises particles of sizes of about 1.0 mm. Preferably, the particles of the first intermediate layer  210  comprise sand, porous grog, or a mixture thereof. In a preferred embodiment, the second intermediate layer  215  comprises particles of sizes of about 60 mesh to about 100 mesh. In a more preferred embodiment, the second intermediate layer  215  comprises particles of sizes of about 80 mesh. The particles of the second intermediate layer  215  comprise sand, porous grog, or a mixture thereof. In a preferred embodiment of the present invention, the bottom layer  220  comprises particles of sizes of about 100 mesh to about 140 mesh. In a more preferred embodiment of the present invention, the bottom layer  220  comprises particles of sizes of about 120 mesh. The particles of the bottom layer  220  comprise sand, porous grog, or a mixture thereof. 
     While the top layer  205 , first intermediate layer  210 , second intermediate layer  215  and bottom layer  220 , as illustrated in  FIG. 10 , are shown as each having an equal depth, the invention is not so limited. The top layer  205 , first intermediate layer  210 , second intermediate layer  215  and bottom layer  220  may each independently be of equal or differing depth. 
     The retention cap  225 , as illustrated in  FIG. 10 , prevents the top layer  205 , first intermediate layer  210 , second intermediate layer  215  and bottom layer  220  from exiting the container  200  while still allowing liquid to exit from the interior of the container  200 . In a preferred embodiment of the present invention, the retention cap  225  comprises a mesh, plastic sieve screen. In a more preferred embodiment, the mesh, plastic sieve screen is from about 100 mesh to about 150 mesh. In another preferred embodiment of the present invention, the retention cap  225  is dry pressed earthenware with a pre-fired body composition comprising clay, porous grog and combustible material. In a preferred embodiment, the body composition contains between about 30% and about 60% by weight of clay, between about 30% and about 60% by weight of porous grog, and between about 5% and about 20% by weight of combustible material. In a more preferred embodiment, the composition contains about 45% by weight of clay, about 45% by weight of porous grog and about 10% by weight of combustible material. In a preferred embodiment, silver is applied to the dry pressed earthenware following firing. 
     According to the embodiment of the present invention illustrated in  FIG. 10 , nonpurified water is poured into the top of the container  200 . The nonpurified water passes through the top layer  205 , the first intermediate layer  210 , the second intermediate layer  215 , and the bottom layer  220 . The water then permeates through the retention cap  225  and exits the water purifier system  70  as purified water. 
       FIG. 11  illustrates a cross-sectional side view of the porous grog of the present invention utilized in a further exemplary water purifier system  70 . As illustrated in  FIG. 11 , a top layer  205 , a first intermediate layer  210 , a second intermediate layer  215 , and a purifier disk  230  are bounded by a container  200  and a retention cap  225 . Optionally, the container  200  may be covered with a cap or lid to prevent the interior of the container  200  from becoming contaminated by foreign particles. Preferably, the container  200  comprises a non-toxic, relatively water impermeable material. In a preferred embodiment, the material is earthenware or plastic. 
     In a preferred embodiment, the top layer  205  comprises particles of sizes from about 4.0 mm to about 6.0 mm. In a more preferred embodiment, the top layer  205  comprises particles of sizes of about 5.0 mm. Preferably, the particles of the top layer  205  comprise stone, porous grog, or a mixture thereof. 
     In a preferred embodiment, the first intermediate layer  210  comprises particles of sizes from about 0.5 mm to about 1.5 mm. In a more preferred embodiment, the first intermediate layer  210  comprises particles of sizes of about 1.0 mm. Preferably, the particles of the first intermediate layer  210  comprise sand, porous grog, or a mixture thereof. In a preferred embodiment, the second intermediate layer  215  comprises particles of sizes of about 60 mesh to about 100 mesh. In a more preferred embodiment, the second intermediate layer  215  comprises particles of sizes of about 80 mesh. The particles of the second intermediate layer  215  comprise sand, porous grog, or a mixture thereof. 
     As illustrated in  FIG. 11 , a purifier disk  230  is located adjacent to the second intermediate layer  215 . The purifier disk  230  comprises dry pressed earthenware with a pre-fired body composition comprising clay, porous grog and combustible material. In a preferred embodiment, the body composition contains between about 30% and about 60% by weight of clay, between about 30% and about 60% by weight of porous grog, and between about 5% and about 20% by weight of combustible material. In a more preferred embodiment, the composition contains about 45% by weight of clay, about 45% by weight of porous grog and about 10% by weight of combustible material. In a preferred embodiment, silver is applied to the purifier disk following firing. 
     According to the embodiment of the present invention illustrated in  FIG. 11 , nonpurified water is poured into the top of the container  200 . The nonpurified water passes through the top layer  205 , the first intermediate layer  210 , the second intermediate layer  215 , and permeates through the purifier disk  230 . The water then permeates through the retention cap  225  and exits the water purifier system  70  as purified water. 
       FIG. 12  illustrates a cross-sectional side view of the porous grog of the present invention utilized in a further exemplary water purifier system  70 . As illustrated in  FIG. 12 , a purifier disk  230  is bounded by a container  200 . Optionally, the container  200  may be covered with a cap or lid to prevent the interior of the container  200  from becoming contaminated by foreign particles. Preferably, the container  200  comprises a non-toxic, relatively water impermeable material. In a preferred embodiment, the material is earthenware or plastic. 
     As illustrated in  FIG. 12 , a purifier disk  230  is bounded by the container  200 . The purifier disk  230  comprises dry pressed earthenware with a pre-fired body composition comprising clay, porous grog and combustible material. In a preferred embodiment, the body composition contains between about 30% and about 60% by weight of clay, between about 30% and about 60% by weight of porous grog, and between about 5% and about 20% by weight of combustible material. In a more preferred embodiment, the composition contains about 45% by weight of clay, about 45% by weight of porous grog and about 10% by weight of combustible material. In a preferred embodiment, silver is applied to the purifier disk following firing. 
     According to the embodiment of the present invention illustrated in  FIG. 12 , nonpurified water is poured into the top of the container  200 . The nonpurified water permeates through the purifier disk  230  and exits the bottom of the container  200  as purified water. 
     For the permeable grog purifiers of the present invention, looking under a microscope it is clear that the filter medium is not homogenous with respect to permeability. The micrograph in  FIG. 13  shows the fired purifier medium at 5x magnification. This micrograph shows many elongated pores  100 , those primarily involved in bringing about control over the amount of flow. It should be noted that the larger white areas  101  indicate pores caused by burnout of a number of combined grains of flour. The larger dark areas  102  indicate some of the bigger particles of the 10 mesh grog. The micrograph indicates that the permeability varies from clump to clump, or particle to particle within the purifier. 
       FIG. 14  shows the micrograph of the un-fired purifier medium at 20x magnification. The dark areas  200  indicate the pre-fired grog and the grayish area  201  indicates the un-fired clay compositions. The white areas  202  show pores where the composition was not fully compacted during mixing of the grog and the clay compositions. From these micrographs, it is evident that the most permeable material is the porous grog and the least permeable is the plastic clay necessary in facilitating forming the resultant porous grog purifier of the present invention. 
     Although the present invention has been described in terms of particularly preferred embodiments, it is not limited to these embodiments. Alternative embodiments and modifications which would still be encompassed by the invention may be made by those skilled in the art, particularly in light of the foregoing teachings. Therefore, the following claims are intended to cover any alternative embodiments, modifications or equivalents which may be within the spirit and scope of the invention as defined by the claims.