RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/507,423, filed on Jul. 13, 2011, which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     Various embodiments described herein relate to a system and a method for for water purification and desalination. A filter assembly includes a semipermeable membrane which is supported by other structural portions. 
     BACKGROUND 
     Water may contain many different kinds of contaminants including, for example, particulates, harmful chemicals, and microbiological organisms, such as bacteria, parasites, protozoa, and viruses. In a variety of circumstances, these contaminants must be removed before the water can be used. Any harmful contaminants must be removed from water before it is potable, i.e., fit for human consumption. 
     In many instances, there are deadly consequences associated with exposure to contaminated water. In many situations, such as an undeveloped country or a war zone, there are several factors that contribute to contaminated water, including: increasing population densities, increasingly scarce water resources, no water filter utilities, and often, no electricity (including batteries, which may be too expensive). Also, it is common for sources of drinking water to be in close proximity to human and animal waste, such that microbiological contamination is a major health concern. As a result of waterborne microbiological contamination, an estimated six million people die each year, half of which are children under 5 years of age. 
     In 1987, the U.S. Environmental Protection Agency (EPA) introduced the “Guide Standard and Protocol for Testing Microbiological Water Purifiers”. The protocol establishes minimum requirements regarding the performance of drinking water filter devices that are designed to reduce specific health related contaminants in public or private water supplies. The requirements are that the effluent from a water supply source exhibits 99.99% (or equivalently, 4 log) removal of viruses and 99.9999% (or equivalently, 6 log) removal of bacteria against a challenge. Under the EPA protocol, in the case of viruses, the influent concentration should be 1×10 7  viruses per liter, and in the case of bacteria, the influent concentration should be 1×10 8  bacteria per liter. Because of the prevalence of  Escherichia coli  ( E. coli , bacterium) in water supplies, and the risks associated with its consumption, this microorganism is used as the bacterium in the majority of studies. Similarly, the MS-2 bacteriophage (or simply, MS-2 phage) is typically used as the representative microorganism for virus removal because its size and shape (i.e., about 26 nm and icosahedral) are similar to many viruses. Thus, a filter&#39;s ability to remove MS-2 bacteriophage demonstrates its ability to remove other viruses. 
     In undeveloped countries, disaster areas, and in war zones, the water sources may include seawater, rivers, streams, lakes, ponds, ground water, indigenous wells, or sub-standard municipal water. Good water sources may go bad leaving inadequate sources of water or the sources of water may never have been good. 
     People in these situations may not be educated and may not have shelter, much less a home or place to store a device. Today&#39;s solutions seem to be rather large and complex to use. Most solutions purify 5-10 gallons of water and require the user to carry a large container as well as a heavy mechanism which is used to purify water. Individuals probably would not carry a filtration system with an attached 10 gallon water canister in such situations. As a result of not carrying the big solution, many times the individuals in effected areas will drink unpurified water when thirsty, thereby increasing the chances of sickness or even death from unpotable water. 
     In addition, many solutions require a power source. In a disaster situation or in a war zone, power may not be available. In addition, battery power can be used, however batteries often do not last for a long time and may discharge before the disaster is over or before a soldier or unit of soldiers leaves the area or can find power. Such solutions are heavier, since batteries are not light. This solution also requires a rescue worker, soldier, or unit of soldiers to carry additional batteries. Without batteries, these water purification devices are generally useless. This again leads to people drinking unpotable water is certain situations. 
     SUMMARY OF THE INVENTION 
     In such situations, the water treatment device needs to be simple to use and small enough for an individual to carry. Military personnel also need a similar device. One that can be carried by an individual and is simple to operate and having the capability of purifying from 1 to 10 gallons of water per hour. In either case, the capability to remove suspended solids, dissolved salts, and micro-organisms is desirable so that the unit can be used in any of a full range of water sources. 
     A water treatment device includes an inner aluminum cylinder that includes a seal and a filter on one end. The water treatment device also includes an outer canister which is filled with unpurified water. The inner aluminum cylinder is pressed into the canister. This forces the unfiltered water through the filter and into the aluminum cylinder. The aluminum cylinder can be opened to reveal drinkable, or substantially purified water. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a military person using the water treatment and desalination device disclosed herein, according to an example embodiment. 
         FIG. 2  is an exploded view of the system water purification and desalination, according to an example embodiment. 
         FIG. 3  is a perspective view of the filter end of the inner canister, with the filter assembly removed, according to an example embodiment. 
         FIG. 4  is a perspective view of a filter assembly associated with the water treatment and desalination device, according to an example embodiment. 
         FIG. 5  is a perspective view of the water treatment and desalination device with the inner canister within the outer canister, according to an example embodiment of the invention. 
         FIG. 6  is a flow chart for the method of using the water treatment and desalination device, according to an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a top view of a military person  100  using the water treatment and desalination device  200  disclosed herein, according to an example embodiment. The military person  100  has found a less than pure source of water  110 . The source of water  110  includes suspended solids, like dirt and clay, as well as viruses and bacteria. In some situations the source of water may include  Escherichia coli  ( E. coli ). In addition, the source of water may also include salt or various salts. Each of these and others will make the water of the water source  110  unpotable or unfit for human consumption. By consuming such water a human runs the risk of getting very sick or may even risk dying. The water treatment and desalination device  200  or a portion of the water treatment and desalination device  200  is placed into the water source. Specifically, the outer canister  230  (discussed in more detail in the discussion of  FIG. 2 ) is placed in the water source. The soldier or military person fills the outer canister  230  with water from the water source that will be treated using the water treatment and desalination device  200  so that the water obtained is potable or fit for human consumption. In  FIG. 1 , the outer canister  230  is shown with the inner canister  210  placed within the outer canister  230 . 
       FIG. 2  is an exploded view of the system water purification and desalination  200 , according to an example embodiment. The water treatment and desalination device  200  includes an inner canister  210  having a lid  212  on one end and a filter assembly  220  on the other end. The water treatment and desalination device  200  also includes an outer canister  230 . The inner canister  210  fits within the outer canister  230 . 
     The inner canister  210  includes a lid end  211  and a filter end  213 . The inner canister  210  also includes a lid  212 . The lid  212  securely attaches to the lid end  211  of the inner canister  210 . The lid  210  and the inner canister  210  can be made of aluminum or other lightweight material that is tough and durable yet lightweight. In one embodiment, the lid  212  includes a set of threads and the inner canister includes another set of threads. The lid  212  threadably engages the lid end  211  of the inner canister  210 . When the lid  212  is attached to the inner canister  210 , there is a volume formed within the inner canister  210  for clean or substantially purified, potable water. When the lid  212  is attached to the inner canister  210 , the canister  210  and lid  212  form a substantially leakproof volume to capture or hold the potable water. To that end, some embodiments may include may be one or more seals (not shown) between the lid  212  and the end of the inner canister  210 . The seals can be of any type including a rubber or other elastomeric material. The seal material must be hard enough to be durable yet soft enough to provide a seal. In some embodiments, there can be multiple seals between the lid  212  and the inner canister  210 . 
     The inner canister  210  also includes a seal system  214  near the filter end  213  of the inner canister  210 . The seal system  214  is positioned around the cylindrical surface of the inner canister  210 . The seal system  214  acts like a piston ring in an engine. The seal system  214  seals the gap between the outer surface of the inner canister  210  and the inner surface of the outer canister  230 . As shown in  FIG. 2 , the seal includes a single ring  214 . In one embodiment, the ring  214  is made of an elastomeric material such as rubber or a silicone material. Polymeric materials or plastics could also be used. Generally, the durometer readings associated with the material must be high enough so that the material will wear for an elected amount of time. The elastomeric material must also have a low enough reading so that the seal will actually conform to the surface of the inner canister  210  and the outer canister  230  and form a seal. The seal must substantially prevent liquid captured between the inner canister  210  and the inside of the outer canister  230  from passing the seal system  214  between the outer surface of the inner canister  210  and the inner surface of the outer canister  230 . In some embodiments, the seal system  214  includes a single seal. In other embodiments, the seal system  214  can include multiple seals. As shown in  FIG. 2 , the seal of the seal system  214  is an O-ring. In other embodiments the seal may have a different cross-sectional shape. 
       FIG. 3  is a perspective view of the filter end  213  of the inner canister  230 , with the filter assembly  400  removed, according to an example embodiment. The filter end  213  of the inner canister  230  includes a portion of an attachment mechanism  240  and a plurality of openings  242  therein. The portion of the attachment mechanism  240  is for attaching the filter assembly  400  to the end of the inner canister  230 . The attachment mechanism can be any sort of attachment mechanism that does not substantially obstruct the openings  242  in the filter end  213 . The attachment portion  240  includes a plurality of posts having upset ends which mate with another portion of the attachment mechanism associated with the filter assembly  400 . The seal system  214  also includes a seal around the periphery of the filter end  213  of the inner canister  210 . The seal system keeps filtered fluid from flowing into the volume between the inner canister  210  and the outer canister  230  (where unfiltered water is present). The seal system  214  also keeps the unfiltered water from being introduced into the filtered water stream passing from the filter assembly  400  and through the openings  242  and into the inner canister  210  (where filtered water resides). 
       FIG. 4  is a perspective view of a filter assembly  400  associated with the water treatment and desalination device  200 , according to an example embodiment. The filter assembly  400  is multilayered. The layers include a prefilter screen  410  for removing large solids from the unfiltered water. The prefilter screen  410  can be made of one screen or multiple screens. The layers also include a porous support layer  420 . The porous ceramic layer  420  further filters the water. The ceramic layer  420  also serves another purpose, namely, that of supporting a semi-permeable membrane  430  used to filter viruses, bacteria, and salt from the unfiltered water. In some instances, this layer can be very thin. For example, in some instances the layer may be only one atom in thickness. The layers also include a second a porous support layer  440 . This porous support layer  440  allows filtered water to pass and provides support for the semi-permeable membrane  430 . Essentially, the semi-permeable membrane  430  is sandwiched between porous support layers  420  and  440 . The filter assembly also includes an attachment layer  450  that includes an attachment portion  451  that can mate and securely attach to the attachment portion  240  of the filter end  213  of the inner canister  210 . The attachment portion also includes pores or openings  542  that allow fluid to pass the attachment layer  450  of the filter assembly. As shown, the attachment layer  450  is separate from the support layer  440 . It should be noted that in some embodiments, the attachment layer  450  and the support layer  440  could be integrated into a single layer. In the embodiment shown in  FIG. 4 , the first porous support layer  420  and the second porous support layer  440  are porous ceramic. The first and second support layers  420 ,  440  are made of the same material so that the support layers expand and contract substantially the same in response to different conditions being encountered. In another embodiment, the first and second support layers  420 ,  440  could be made of different materials. Generally, the water to be filtered will be in a fairly narrow range of temperatures and so any difference in the thermal coefficient of expansion will be insignificant. Of course, if materials are different, it would be wise to try and match or get thermal coefficients of expansion as close as possible to minimize the chance of such issues. 
     The semi-permeable membrane layer  430  can be any type of semi-permeable membrane material. In one embodiment, a thin film composite membrane (TFC or TFM) is used. The TFC or TFM membrane uses a process referred to as reverse osmosis to remove bacteria, viruses, salt and other contaminants from unfiltered or partially filtered liquids, such as water. These are semipermeable membranes manufactured principally for use in water purification or desalination systems. In essence, a TFC material is a molecular sieve constructed in the form of a film from two or more layered materials. Membranes used in reverse osmosis are, in general, made out of polyimide, chosen primarily for its permeability to water and relative impermeability to various dissolved impurities including salt ions and other small molecules that cannot be filtered. Other membranes can also be used including cellulose ester membrane (CEM), charge mosaic membrane (CMM), bipolar membrane (BPM), anion exchange membrane (AEM), alkali anion exchange membrane (AAEM) and proton exchange membrane (PEM). 
     As shown in  FIG. 4 , the layer  430  of membrane material includes at least one layer of graphene. Graphene is an allotrope of carbon, whose structure is one-atom-thick planar sheets of sp 2 -bonded carbon atoms that are densely packed in a honeycomb crystal lattice. Graphene is most easily visualized as an atomic-scale chicken wire made of carbon atoms and their bonds. The crystalline or “flake” form of graphite consists of many graphene sheets stacked together. The carbon-carbon bond length in graphene is about 0.142 nanometers. Graphene sheets stack to form graphite with an interplanar spacing of 0.335 nm, which means that a stack of 3 million sheets would be only one millimeter thick. As shown in  FIG. 4 , the graphene layer can be any number of layers thick, including a single layer in thickness. The graphene acts as a sieve that is small enough to let water pass but is too small to let other materials pass, such as viruses and bacteria. In one embodiment, graphene is grown to produce the semi-permeable membrane material. In another embodiment, the graphene will be perforated with 1 nm-50 nm openings. These openings gives the graphene a semi-permeable nature. Without the openings, the grapheme would be impermeable. 
       FIG. 5  is a perspective view of the water treatment and desalination device after the inner canister  210  has been inserted into the outer canister  230 , according to an example embodiment of the invention. The inner canister  210  fits within the outer canister  230 . The inner canister  210  is carefully fit into the outer canister  230  and pushed into the outer canister  230 . This can be done when the system water purification and desalination  200  is not being used. When not used, the lid  212  is also generally attached to the lid end  211  of the inner canister  210 . The inner canister  210  is also be forced into the outer canister  230  when the outer canister  230  is filled or contains unfiltered water. The lid  212  will be attached to the lid end  211  of the inner canister  210  to contain the filtered water for later use. 
       FIG. 6  is a flow diagram for the method  600  of use of the system water purification and desalination  200 , according to the example embodiment. The method  600  includes securing the lid to the inner canister and removing the inner canister from outer canister  610 . The outer canister is then filled with unfiltered water  612 . The outer canister  210  is typically not filled all the way to the top, but is filled about 80% full. Filling the outer canister  210  to the top will would be too much water. As a result, the outer er canister  210  is filled not quite to the top to accommodate all the water in the smaller inner canister  210 . After partially filing the outer canister  230 , the inner canister  210  is placed into the outer canister  614 . The inner canister is then pushed into the outer canister  616 . Pushing the inner canister by hand into the outer canister produces sufficient pressure to force the unfiltered water through the filter assembly  400 . The seal system  214  keeps the water in the outer canister as pressure is being applied. The seal system  214  also will prevent flow of unfiltered water between the filter assembly  400  and the unfiltered water surrounding the filter end  213  of the inner canister  210 . The inner canister  210  is pushed until substantially fully inserted into the outer canister  230 . The filtered water will be within the inner canister. The inner canister can be removed  618 , and the lid can be unscrewed to access the filtered water  620 . 
     In one embodiment, the inner canister includes a shut off to keep the water in. In the alternative, the inner canister includes substantially one way valves positioned near the openings in the filter end  213 . 
     A water purification and desalination device includes a flow path for water and a graphene material positioned within the flow path. The device also includes a container for containing the water after is has passed through the graphene material. The graphene material is at least one atomic layer in thickness of graphene. In some embodiments, the graphene material is one-atom-thick planar sheets of sp 2 -bonded carbon atoms that are densely packed in a honeycomb crystal lattice. In another embodiment, the graphene material includes a plurality of atomic layers of graphene material. In some embodiments, the graphene sheets having an interplanar spacing in a range of 0.300 nm to 0.3705 nm. In still other embodiments, the graphene sheets having an interplanar spacing of approximately 0.335 nm. The graphene material can be associated or part of a membrane of material. The graphene material is situated in the flow path so that the water that enters the container passes through the graphene material. In still other embodiments, the graphene material is perforated and has openings therein, the openings within the range of 1 nm-50 nm. 
     A water purification and desalination device includes a first container having a sealable end and a membrane end, and a second container having a closed end and an open end. The first container fits within the second container. The device includes a seal positioned between the exterior of the first container and the interior of the second container to force water in the second container through the membrane end of the first container. The membrane filters out impurities in the water. In one embodiment, the membrane includes at least one layer of graphene material. In another embodiment, the membrane includes a plurality of layers of graphene material. The interlayer spacing between layers of graphene material can be in the range of 300 nm to 370 nm. In some embodiments, one or more layers of graphene material can include perforations therein. 
     A method of purifying water includes placing a graphene material in a fluid flow path, and passing water from a source through the graphene material to remove contaminants from the water. Placing a graphene material in a fluid flow path includes poviding an inner canister with a closed end and a membrane end, the graphene material associated with the membrane end, and passing water from an outer canister through the membrane end of the inner container. The inner canister sealing engages and fits within the outer canister. Passing water from an outer canister to an inner canister includes pushing the inner canister into an outer canister containing at least some water. 
     It should be noted that hand pressure is one way of producing the appropriate amount of pressure in the filtering and desalinating system  200 . In other embodiments, this may be too unconcontrolled so other types of pressurization systems can be used, including hand pumps or similar pressurizing systems. These types of pressurizing systems may be needed to deliver a more even pressure to the filter assembly  400  during the filtration process. 
     The embodiments described above meet a need for energy efficient, small scale, water treatment and purification at an individual or squad level. The embodiments also are lightweight, hand carried, low power water purification devices. The embodiments described above also have the capability to purify water at a rate ranging from 1 to 10 gallons per hour. It should be noted that typical water sources encountered during expeditionary, military, or other operations include seawater, rivers, streams, lakes, ponds, ground water, indigenous wells, or sub-standard municipal water. The embodiments described are capable of removing suspended solids, dissolved salts, and micro-organisms from the full range of potential water sources mentioned previously. 
     This has been a detailed description of some exemplary embodiments of the invention(s) contained within the disclosed subject matter. Such invention(s) may be referred to, individually and/or collectively, herein by the term “invention” merely for convenience and without intending to limit the scope of this application to any single invention or inventive concept if more than one is in fact disclosed. The detailed description refers to the accompanying drawings that form a part hereof and which shows by way of illustration, but not of limitation, some specific embodiments of the invention, including a preferred embodiment. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to understand and implement the inventive subject matter. Other embodiments may be utilized and changes may be made without departing from the scope of the inventive subject matter. Thus, although specific embodiments have been illustrated and described herein, any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description.
A water treatment device includes an inner canister or cylinder that includes a seal and a filter assembly attached on one end. The water treatment device also includes an outer canister which is filled with unpurified water. The inner canister or cylinder is pressed into the outer canister to produce pressure on unpurified water that forces the unpurified water through the filter assembly. The inner canister or cylinder can be opened to reveal drinkable, or substantially purified water.