Abstract:
A slow/intermittent sand filter that purifies polluted water by flowing through sand in a manner that achieves greater purity and permits simpler and more effective maintenance than existing filters.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of co-pending (Allowed) U.S. application Ser. No. 13/159,705, filed Jun. 14, 2011, and entitled Water Filter System, incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This disclosure relates to the field of water purification devices. More particularly, this disclosure relates to a slow/intermittent sand filter that purifies polluted water by flowing through sand in a manner that achieves greater purity and permits simpler and more effective maintenance than existing filters. 
     BACKGROUND 
     A major issue that persists in underdeveloped areas is both water quality and quantity. Slow and/or intermittent sand filters are a good choice for such areas in that they are generally of simple and inexpensive construction and do not require the use of electricity, chemicals or other materials that require replacement. However, conventional slow sand filters still desire improvement in that they do not adequately eliminate many bacteria and are not user friendly by illiterate and unsophisticated peoples due to their maintenance requirements 
     The present disclosure advantageously provides improved slow and/or intermittent sand filter devices having improved construction and which offer simplified maintenance as compared to conventional slow sand filters. The filters are of low cost and easily used so that the masses in undeveloped countries may have better access to cleaner water. 
     SUMMARY 
     The above and other needs are met by a water filtration system which, in one aspect, includes a treated water container and a water treatment container located substantially within the treated water container. The water treatment container is configured to receive untreated water and to treat the untreated water to yield treated water that is passed to the treated water container for storage and/or dispensing. 
     The water filtration system includes a treated water container and a water treatment container located substantially within the treated water container. The water treatment container is configured to receive untreated water and to treat the untreated water to yield treated water that is passed to the treated water container for storage and/or dispensing. 
     The treated water container includes a container having a bottom and a sidewall extending upwardly from the bottom. The water treatment container includes an upper section configured to receive a volume of water to be treated; a first and a sand containing section within the container and below the upper section having sand that includes a bio-layer having a thickness at the uppermost portion of the sand. A sand separator is located within the sand containing section and in flow communication with the water treatment container. The sand separator is configured to separate sand in the water treatment container from treated water passing to the treated water container. 
     A flowpath extends from a location within the sand separator to a location outside of the sand separator defining a treated water output, the treated water output being located at a height above an upper surface of the sand in the sand containing section of the water treatment container. 
     In another aspect, the disclosure relates to a water treatment container configured to receive untreated water and to treat the untreated water to yield treated water. The treated water container includes a container having a bottom and a sidewall extending upwardly from the bottom. The water treatment container is configured to receive a volume of water to be treated and includes a sand containing section having a bio-layer having a thickness within the water treatment container. The water to be treated passes through the bio-layer at a flow rate of about 0.10 meters per hour or less. 
     In yet another aspect, the disclosure relates to a method for purifying water, which includes the steps of, providing a water treatment container having a sand containing section within the water treatment container having sand that includes a bio-layer having a thickness at the uppermost portion of the sand, and maintaining flow conditions so that the water passes through the bio-layer at a flow rate of about 0.10 meters per hour or less. 
     Water filtration systems according to the disclosure advantageously simplify filtration of water, achieving greater purity, and have simplified maintenance requirements and reduced maintenance frequency as compared to conventional filtration systems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages of the disclosure are apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein: 
         FIG. 1  is an exploded perspective view of a water treatment system according to the disclosure. 
         FIG. 2  is a cross-sectional perspective view of the water treatment system of  FIG. 1 . 
         FIG. 3  is a perspective view of the water treatments system of  FIG. 1 , with a treated water container component thereof shown in phantom. 
         FIG. 4  is a perspective view of a water treatment container of the water treatment system of  FIG. 1 . 
         FIG. 5  is a cross-sectional view of an interior water treatment component of the system of  FIG. 1 . 
         FIG. 6  is a cross-sectional view showing sand disposed in the water treatment container and having a bio-layer. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to the drawings, the disclosure relates to a slow sand filter system  10  configured for removing dirt, sticks, microorganisms, and bacteria from polluted input water so that output water from the filter system  10  is significantly cleaner and purer than the input water. 
     One of the main ways that slow sand filters perform is by passing water thorough a bio-layer, a layer of sand that is approximately two inches thick beneath the supply water interface. This layer develops over several weeks wherein bacteria lodge in the sand and feed on the pollutants and dissolved organic matter and help to improve the quality of the treated water. It is important to let this layer develop and to limit the speed of flow through the layer so that it has time to advantageously treat the water. Over time this layer becomes clogged with solids so that water cannot flow through the layer fast enough to meet the needs for treated water. At that point, the bio-layer may be acted on by (1) carefully stirring the top inch or so of the layer to mechanically dislodge the clogging solids and suspend the solids back into the layer of water over the sand, and (2) removing the water with the suspended solids. This “bio-layer cleaning” step is a delicate operation as it can damage the bio-layer causing it to be less effective than needed, and requiring an additional bacteria development time period before it works again as needed. 
     The filter system  10  of the disclosure is advantageously configured to reduce the frequency of performing, if not eliminate, the need for a bio-layer cleaning step. As will be appreciated, reducing the need for such a bio-layer cleaning step advantageously renders the filter more user friendly, more constantly functional, and accessible for use by the masses. 
     With reference to the drawings, the filter system  10  includes an exterior treated water container  12  and an interior water treatment container  14  located substantially within the exterior container  12 . The containers  12  and  14  are sized to have substantially similar volume capacities. The treated water container  12  serves as a reservoir for receiving and holding water treated by the water treatment container  14  of the filter system  10 . The water treatment container  14  receives untreated water and treats the untreated water to yield treated water that is passed to the treated water container  12  for storage and/or dispensing. 
     The treated water container  12  is an open topped container having a bottom  16  and a cylindrical sidewall  18  extending upwardly from the bottom  16 . The container  12  is made of a fluid impermeable material such as molded plastic. 
     The treated water container  12  is wrapped around the water treatment container  14  or otherwise nested with the water treatment container  14  such that the treated water is part of the overall filter system  10 . The wrapped or nested construction is believed to significantly reduce the possibility of recontamination of the treated water as compared to conventional filter systems which typically route the treated water to a separate collection container externally remote from the portion of the filter in which the water is treated. In this regard, it has been observed that recontamination has been found to be a significant problem in furnishing clean water to the user, and the described configuration is believed to substantially eliminate one of the most common sources of recontamination. 
     Treated water obtained by the treated water container  12  from the water treatment container  14  is dispensed from the treated water container  12  by gravity through a tap  22  located on a lower portion of the sidewall  18  of the treated water container  12 . The tap  22  includes a valve fed by a conduit structure configured as a tube within a tube at the outlet such that if the outer tube is compromised, the inner tube remains out of reach and untouched. The treated water is dispensed via the tap  22  into the end user&#39;s container, typically a drinking cup or a cooking vessel. A removable mouthpiece  23  may be attached to the tap  22  to permit a person to place their mouth adjacent the tap  22  without contaminating the tap  22 , with the mouthpiece  23  being personal to a user and removed after their use. 
     Matching the volume capacity of the treated water container  12  to the volume capacity of the water treatment container  14  according to the disclosure is advantageous to provide a stored volume of treated water so that the low flow speed of water through the system  10  is not detrimental to the typical needs of a home user using the system  10  to provide drinking and cooking water. 
     For example, the containers  12  and  14  may be configured to each have a capacity of 5 gallons. A user needing 5 gallons of treated water for the morning would then put five gallons of water to be treated into the water treatment container  14  at bedtime, and five gallons will be available by morning, since the system according to the disclosure which travels water through the bio-layer thickness at a desired average rate of about 0.03 meters per hour yields treated water at a rate of about one half (½) gallon per hour. That is, in one hour the water will flow, on average, through about 0.03 meters of the thickness of the bio-layer. To achieve this, as explained more fully below, the filter system is configured so that water passes through the bio-layer at a flow rate of about 0.10 meters per hour or less. 
     Conventional filters typically have no output container and are designed for quick treatment, such that if a user wants a glass of water, the needed volume is introduced and the treated water is dispensed within a minute or two, with such high production speed compromising both quality of the treated water and immediately available volumes. Thus, conventional filters typically pass water through the bio-layer at a high rate about 10 times higher and produce about 16 gallons of treated water per hour. Contrary to conventional filter structures, the filter system according to the disclosure passes water very slowly through the bio-layer, as explained more fully below. 
     The relevant volume of the treated water container  12  corresponds to the volume provided with the water treatment container  14  installed onto the treated water container  12  below a treated water output port  24  of the treatment container  14 , generally corresponding to a water level L as shown in  FIG. 2 . Thus, if the treatment container  14  is configured to receive in batch 5 gallons of water for treatment, the treated water container  12  is sized so that the water level L corresponds to 5 gallons. 
     The water treatment container  14  is configured to have an upper section  30  configured to receive a volume of water to be treated. For example, if the system  10  is designed to treat 5 gallons of water as in the example set forth above, the upper section  30  is sized to hold 5 gallons of water. The upper section  30  includes a circumferential lip  32  configured to engage a corresponding upper peripheral edge of the treated water container  12 . A removable upper debris screen or filter  34  is set into a filter tray  35  located within the upper section  30  to remove larger sized debris that would tend to quickly clog the sand containing portion of the filter system  10 . The filter tray is a bowl-shaped plastic part having a slotted or aperture bottom. The upper debris filter  34  is held in place by a retainer  34   a  and the upper filter  34  may be easily removed regularly for cleaning, as by rinsing or shaking, and then replaced. 
     A lower debris screen or filter  36  (held in place by a retainer  36   a ) is preferably located in the upper section  30  and spaced below the filter tray  35 , but above an intermediate section  37  located between the upper section  30  and a lower section  38 . The intermediate section  37  and the lower section  38  are both filled with sand. 
     The retainers  34   a  and  36   a  are each provided as by sections of flexible, preferably plastic, tubing that are positioned within annular grooves  34   b  and  36   b , respectively, on the interior sidewall of the container  14 . The opposite ends of the plastic tubes butt against one another resulting in outward forces to retain the filters in place. Thus, each debris filter is placed adjacent one of the grooves and the plastic tubing is installed in the groove and the plastic tubing provides an outward force to retain the debris filter in place. 
     The outlet port  24  is preferably located at a height that corresponds to a height of about 2 inches above the upper surface of the sand in the intermediate section  37  (dashed line S in  FIG. 3 ). This positioning of the outlet port  24  relative to the bio-layer (designated B in  FIG. 6 ) provided by the uppermost portion of the sand S is desirable both to assure that with intermittent flow the water is maintained at that level so that even with evaporation that might take place in hot climates over days or weeks, the bio-layer is protected from drying out. 
     This lower filter  36  can easily be changed or cleaned, again to protect the bio-layer represented by the top layer of sand in the intermediate section  37  from disturbance or the need for it to be delicately cleaned later on. In this regard, the combination of the upper and lower removable filters advantageously enable improved ease of maintenance and with more effective results of the filter system  10 . 
     Another significant aspect of the disclosure relates to the configuration of the intermediate section  37  and the lower section  38 . As seen in the drawings, the intermediate section  37  has a tapered sidewall so that the intermediate section  37  decreases or tapers in cross-section as it approaches the lower section  38 . The lower section  38  decreases or tapers in cross-section as it approaches a bottom  40  thereof. 
     For the purpose of example, for the system  10  configured to treat about 5 gallons of water, the upper section  30  has a diameter of about 13 inches and is round in cross-section. The intermediate section  37  has a diameter of about 11 inches which tapers to a diameter of about 7 inches at the bottom of the intermediate section  37 . The lower section  38  has a diameter of about 7 inches, which tapers to a diameter of about 4 inches at the bottom of the lower section  38 . A sand separator  42  is located on and extends upwardly from the bottom  40  of the lower section  38 . 
     As will also be appreciated, the drawings of the described embodiment show that the containers  12  and  14  extend to substantially the same height. This is advantageous to prevent overflowing of the treated water container  12  without overflowing the water treatment container  14 . 
     The sand separator  42  functions to separate the sand from water leaving the water treatment container  14  and provides a vertical chamber configured as an inverted cone having an open bottom  44  located around an upward bulge  46  ( FIG. 5 ) centrally defined on the bottom  40  of the lower section  38  of the container  14 . In this regard, it has been discovered that the sand separator  42  may be provided as by a plastic drinking cup, such as a disposable plastic drinking cup of a volume of about 16 ounces. This enables reductions in costs and ease of finding replacement components. 
     The bottom  44  of the sand separator  42  (e.g., corresponding to the top rim of a plastic drinking cup if such is used) has a diameter of about 75% of the bottom  40  of the lower section  38 , or about 3 inches for the described example system  10 . A lower opening  48  is centrally located on an uppermost portion of the bulge  46 . A generally J-shaped tube or conduit  50  is located within the separator  42 . The tube  50  begins at a location spaced below the top of the sand separator  42  and extends downward through the opening  48  of the bulge  46  and then turns to run upwardly along the outer surface of the water treatment container  14  until terminating to provide the output port  24 . 
     The filter system  10  is configured so as to not require a specific sand particle size or composition. However, a significant aspect of the disclosure is providing a structure that has a relatively slow flow rate F of water through the bio-layer B, which, as shown in  FIG. 6  typically has a thickness of about 2 inches. The volumetric flow rate of water will depend upon the volume of the sand S, and hence the size of the treatment container. However, it has been discovered that a key aspect, regardless of the total volume of the water treatment container, is to have a flow rate through the bio-layer B of about 0.10 meters per hour or less. That is, in one hour the water will flow, at most, through about 0.10 meters of the thickness of the bio-layer B. 
     The maximum flow rate is usually achieved at the beginning of the process, when the water to be treated is provided to the treatment container. Over time, as the hydrostatic head decreases, the flow rate will decrease. Thus, it has been observed that if the maximum flow rate through the bio-layer B is about 0.10 meters per hour, the average flow rate through the bio-layer B will be about 0.03 meters per hour. 
     This low flow rate may be achieved by having, in combination with the described reduced cross-section of the lower portion of the container  14 , a sand composition that provides such a flow rate, with finer sand compositions providing slower flow rates than coarse compositions. However, in the event the available sand composition does not achieve this slow a rate or slower, then a flow restrictor, such as a clamp or other valve structure may be provided on the tube  50  to decrease the flow rate. 
     The sand separator  42  preferably occupies space to effectively decrease the cross-sectional area to about 25% (about 25 square inches) of the greatest cross-sectional area of the sand in the system  10  (about 100 square inches), which occurs at the top of the intermediate section  37 . This decrease in cross-sectional area of the sand advantageously slows down the flow rate of water (flow per square inch) in the lower section  38  where the sand remains predominantly clean and isolated from solids in the water at higher locations in the sand, especially the uppermost layer of sand that provides a bio layer, as previously described. 
     The described reduction in the area of the sand separator  42  that is occupied by sand, that is the rapid reduction of the cross-sectional area occupied by sand from the top to the bottom, also offers significant reduction in the volume and weight of sand required. This is particularly advantageous when the availability of suitable sand is limited in a geographic location in which the filter system is used. 
     It is desirable to slow the water flow through this region of the system  10  to configure the system  10  to filter slower but require less frequent maintenance, since as the upper portions of the sand become clogged with solids, such clogging will not affect the filtration rate or other operation of the filter system until such time as the upper sand becomes about 75% clogged, which is severely clogged. Thus, the filter system  10  advantageously may be operated for long periods of time without maintenance to clean the upper portion of the sand. In this regard, the sand separator  42  should decrease the cross-sectional area of the sand as described by at least about 50 percent, but most preferably from about 70 percent to about 80 percent. 
     The water treatment container  14  further includes a lid  60  to help keep dust and other contaminants out of the system  10  and the treated water in the treated water container  12 . As will be appreciated, the water filtration system  10  advantageously simplifies filtration of water by simplifying the maintenance requirements. In addition, the construction of the filter system that enables operation despite having substantial clogging of the sand reduces the maintenance frequency as compared to conventional filtration systems. Another significant advantage is that by configuring the system for producing output water very slowly in the background on a continuing basis, the slow flow yields a far better quality of output, up to ten times more pure than conventional slow/intermittent but faster-flowing filters. 
     The foregoing description of preferred embodiments for this disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide the best illustrations of the principles of the disclosure and its practical application, and to thereby enable one of ordinary skill in the art to utilize the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the disclosure as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.