|Title of Invention||
WATER PURIFICATION DEVICE
|Abstract||The invention concerns a gravity fed water purification device comprising a top and bottom chamber wherein the base of the top chamber is provided on either side with a filter block, both having an inlet surface and an outlet surface whereby the entire volume the inlet surface o the block in the bottom chamber.|
|Full Text||FORM - 2
THE PATENTS ACT, 1970 (39 of 1970)
The Patents Rules, 2003
(See Section 10 and Rule 13)
WATER PURIFICATION DEVICE
HINDUSTAN UNILEVER LIMITED, a company incorporated under the Indian Companies Act 1913 and having its registered office at Hindustan Lever House, 165/166, Backbay Reclamation, Mumbai - 400 020, Maharashtra, India
The following specification particularly describes the nature of the invention and the manner in which it is to be performed.
FIELD OF INVENTION
The present invention relates to a gravity-fed water purification device for filtering particulate contaminants including microorganisms like cysts, apart from removal of chemical contaminants, while at the same time providing for relatively high flow rates. The device particularly provides for enhanced filtration capability while minimizing the amount of filtration media used.
BACKGROUND AND PRIOR ART
In drinking water, it is essential to remove microorganisms and chemical contaminants from the water to make it suitable and safe for drinking and maintenance of good health.
Several different methods are known for filtration of water based on which various devices and apparatus have been designed and are also commercially available. These methods and devices vary depending on whether the application is for industrial or household use and also critically depend upon the pressure at which the water to be purified is available.
Water treatment for household use is basically directed to provide safe drinking water. The point of use (POU) devices typically used in households for water treatment can be classified based on whether input water is available under pressure, like water from an overhead reservoir where input pressures are generally greater than 10 psig, or whether water is available in small quantities like a few litres, in which case the pressure available is close to the pressure due to gravity, generally less than 0.5 psig.
Filtration of water in the former case is categorized under online systems which have advantage of the pressure of the water mains to drive the flow through the filtration device and therefore do not usually face problems of achieving desired flow rate in combination with effective filtration.
The latter are classified as gravity filters or self-contained systems, which process water in batches under low pressure. It is a challenge to ensure the necessary removal of contaminants like particulate matter, including biological moieties like protozoan cysts e.g. Cryptosporidium and even smaller organisms like bacteria and virus, in addition to dissolved chemicals like chlorine, organic compounds and pesticide residues, by filtration under low pressure, while ensuring the high flow rate desired. Thus, when filters designed for online systems are applied to gravity fed systems they have failed to consistently produce the desired flow rates over time and often choke after a few litres are passed through, leading to the need for replacement or cleaning.
Typically, a self-contained gravity based system for domestic application has an upper and a lower chamber separated by a filter cartridge. The water to be treated is poured in the upper chamber and allowed to flow under gravity through the cartridge to the lower chamber. The treated water in the lower chamber can be dispensed for consumption as and when desired.
Such filter cartridges are usually of the "depth type" in which particles and impurities in the water are removed by adsorption on the particles of the filter medium. Hence, removal efficiency depends on the path length of the water through the filter and therefore increased efficiency can only be obtained by increasing the path length. In such filter cartridges it is known to use activated carbon or similar absorption materials. The activated carbon is suitably made into a block by use of suitable binders that cause the particles to adhere to each other, usually by the action of heat and pressure. Use of ion exchange resin for removing metal and other ions from water is also known.
Filter blocks or catridges should preferably be shaped such that the path length of the water throughout the block is uniform, i.e. the shortest distance between the entry surface of the block and the exit surface is uniform over the block.
Gravity flow systems suffer from the inherent disadvantage of low pressure and it has always been a challenge to provide gravity-fed filters that have effective flow rates and at the same time provide desired filterability and acceptable adsorption kinetics. Also the materials used as the filtration media often tend to be expensive and it is desirable to minimize the amount of such materials while ensuring the high filtration efficiency as well as flow rate.
US5164085 (NRG Enterprises, 1992) describes a filter cartridge for water purification consisting of several layers of filter material with successively smaller pore size. The outer layer is a pre-filtration material with a pore size of approximately 10 microns, the central layer is extruded carbon filter with a pore size of approximately 5 microns and the inner layer is a ceramic filter with a pore size of approximately 0.9 microns. Although this type of filter ensures water to flow in series from one filter to the other, it is evident from the description that it is effective only when inlet water is available under pressure and it will function poorly or not at all in a gravity based system.
US4753728 (Amway, 1988) describes a cylindrical carbon particle filter comprising an inner shell of bonded 80-400 mesh carbon particles bonded and an outer shell of 20-80 mesh carbon particles bonded to each other and to said inner shell, whereby a unitized integral double shell carbon filter is obtained which will allow water to pass more fully than a comparably sized single shell bonded filter of 80-400 mesh carbon particles without adversely affecting the removal qualities of the filter. The two shells are so configured that one shell is inner to the other, thereby requiring the outer shell to have a much higher volume as compared to the inner shell for the same path length of the water. This configuration is not economical the amount of filter media used.
US 5151180 (Cuno, 1992) describes a filter device for use in a residential water supply system which includes a container having an enclosed cavity, and includes a filter unit disposed in the cavity which is two-stage, the first filter having a radial flow filter subassembly and a second axial flow filter
subassembly. Although, the water traverses the filters in a sequential fashion, such a filter device works only under in-line water pressure and will perform very poorly under gravity head conditions.
GB 2234967 (Associated Mills, 1991) describes a gravity feed batch making water filter comprising a first chamber for receiving raw water and a second chamber for receiving filtered water, a filter housing containing multi-bed water filter means disposed between said chambers for filtering said raw water. The water flows under gravity from the first chamber through the filter means to the second chamber. The filtration media are loose granular filter media that are not capable of filtering microorganisms like cyst, bacteria and virus.
US5328609 (Magnusson, 1994) describes a liquid filtration apparatus comprising: (a) a liquid impermeable housing comprising an inlet port and an outlet port; (b) a first annular cast carbonaceous filter element having a porosity of 1-25 microns and a longitudinal first bore and including a fiber filter element concentrically mounted on said first annular cast carbonaceous filter element; (c) first means for directing flow from inlet port to first filter element through a first annular cavity; (d) a second annular cast carbonaceous filter element having porosity in the range of 0.1 to 10 microns and (e) a second means for longitudinally displacing said first filter element from said second filter element, for defining a second annular cavity such that the water passes from said second cavity to the outlet port. This patent publication describes the use of two cast carbonaceous filter elements for filtration of water but it functions only under high pressure of water and would not give the desired flow rate under gravity head of water.
Given the state of the art with respect to water purification devices and the present day need for filtered and purified water, in urban areas with sufficient water, as well as remote places and water-scarce urban centers without a functional water mains, there is a need for optimized and hence cost-effective gravity-fed systems. Such systems should be simple to manufacture and most
importantly achieve good flow rate and at the same time effective removal of particulate and dissolved contaminants.
Increasing the efficiency of filtersystems by increasing the path way and thus the distance between the inlet and outlet surface requires an excessively large increase in filter material. For cylindrical filter systems the volume, and therefore the amount of filter material, is proportional to the square of the radius and for hemispherical filters it is even proportional to the third power of the radius.
The present inventors have now developed a novel gravity fed water purification device wherein water is fed into a top chamber and collected in a bottom chamber after passing through two filter blocks uniquely configured to maximize the filtration efficiency while minimizing the amount of filter media material to be used to achieve these ends.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide a gravity fed water purification device which would provide the desired particulate removal, including micro-organisms like cysts and bacteria, while giving the desired high flow rate over an extended period of time.
A further object of the present invention is to provide a gravity fed water purification device which provides a high flow rate with desired removal of chemicals including pesticides and removal of bad odour.
Yet further object is to provide a gravity fed water purification device which ensures utilization of minimum amount of material as the filtration media, which are often expensive, while at the same time ensuring the desired filtration efficiency, thereby making the device significantly more cost effective and ensuring a wider usage by the consumers in the rural areas who often tend to have the least purchasing power.
SUMMARY OF THE INVENTION
Thus, the invention provides a gravity fed water purification device comprising a top and a bottom chamber wherein the base of the said top chamber is provided on either side with a filter block, the said blocks having an inlet surface and an outlet surface whereby the entire volume of water exiting the outlet surface of the block above the base (the upper block) enters the inlet surface of the block below the base (the lower block).
It is preferred that the shortest distance between the inlet surface and the outlet surface of each of the blocks is substantially constant. Simple configurations that combine a large entry surface area with a limited volume and give a uniform pathway over the entire filter generally have in common that they have a circular horizontal cross section and such configurations are therefore preferred. Particularly preferred configurations are cylindrical or hemispherical as they most efficiently combine a large outer surface area with a small internal volume.
The present invention will be explained further with reference to non-limiting embodiments of the invention outlined in the accompanying drawings.
DESCRIPTION OF DRAWINGS
Figure 1 is a schematic elevational view of one of the embodiments of the gravity fed water purification device which has the inlet surface of the upper block in the top chamber and the outlet surface of the lower block in the bottom chamber, each block defining a hemispherical shape.
The water is filled in the top chamber (1). The base (2) of the top chamber separates the top chamber from the bottom chamber (3) and is provided on either side with a filter block. Filter block (4) is provided on the upper side of the base while filter block (5) is provided on the lower side of the base. The block (4)
is defined by an inlet surface (6) and an outlet surface (7) with filter material contained in the space between the surfaces (6) and (7). Similarly, block (5) on the lower side of the base is defined by the inlet surface (9) and an outlet surface (10) with the filter material of the block contained in the space between the surfaces (9) and (10).
The two filter blocks (4) and (5) are so configured to have a combined cavity (8) which is defined by the outlet surface (7) of the block (4) and the inlet surface (9) of the block (5) and the connecting hole in the base (2).
A base plate (11) of the block (4) and a base plate (12) of the block (5) are adhered to the respective blocks. The two blocks (4) and (5) are detachably secured to the base of the top chamber by screwable threaded joints.
When water is filled in the top chamber (1), the gravity head of the water provides sufficient pressure for the water to traverse through the block (4) from the inlet surface (6) to the outlet surface (7), into the cavity (8). The water thereafter enters the block (5) through the inlet surface (9), traverses through the block (5) and exits the blocks through the outlet surface (10) and collects in the bottom chamber. The water can then be further dispensed as desired.
Figure 2 is a schematic elevational view of another embodiment of a gravity fed water purification device which has the inlet surface of the upper block in the top chamber and the outlet surface of the lower block in the bottom chamber each defining a cylindrical shape.
Both the filter blocks in the embodiment of Figure-2 are adhered to a plate, impervious to water, on one flat end thereof while it is adhered to another plate provided with an orifice for the flow of water at the other end. Thus, a water-impervious plate (13) is adhered to the top of the block (4) while a base plate (11), provided with an orifice, is adhered to the bottom of the block (4). Similarly,
a water-impervious plate (14) is adhered to one end of the block (5), while a plate (12), provided with an orifice, is adhered to the other end of the block (5). The orifices in plates (11) and (12) are connected by a short stretch of tubing extending through a hole in the base plate (2).
Figure 3 and 4 are the top view and bottom view respectively of the embodiment of the gravity fed water purification device of Figure - 2 with plates 13 and 14 removed respectively.
Figure 5 is a schematic view of another embodiment of the gravity fed water purification device as per the invention which has the shape of the top chamber so constructed to ensure maximizing the head available for ensuring high flow rates of water. In this embodiment of the invention, the top chamber has outwardly diverging sidewalls. The upper filter block has the cylindrical shape also depicted in Figure 2 and the lower block has the hemispherical shape also depicted in Figure 1.
The first aspect of the invention provides a gravity fed water purification device comprising a top and a bottom chamber wherein the base of said top chamber is provided on either side with a filter block, said blocks each having an inlet surface and an outlet surface whereby the outlet surface of the upper block and the inlet surface of the lower block are so connected that the water exiting the outlet surface of the upper block is led straight to the inlet surface of the lower block.
Thus, the device of the invention comprises a top chamber and a bottom chamber. A filter block is provided on either side of the base of the top chamber.
In a first preferred embodiment the base of the top chamber is at the same time the top cover of the bottom chamber and consequently the filter block attached to the lower side of the base of the top chamber is located in the upper part of the bottom chamber.
In another embodiment two sets of two filter blocks may be used in combination with an intermediate chamber. The first set is fitted on either side of the base of the top chamber with the intermediate chamber functioning as the bottom chamber for this set. The second set is fitted on either side of the base of the intermediate chamber, with this chamber functioning as the top chamber for the second set of filter blocks and the bottom chamber of the whole filtration device functioning as the bottom chamber for the second set. It will be apparent to the person skilled in the art that this configuration may be repeated with more sets of filter blocks in combination with more intermediate chambers. In this way the total pathway of the water through the filter material may be increased at will while maintaining only a modest total volume of required filter material and a modest total height of the filtration device.
The filter blocks used for this invention are distinct from filters containing loose granular or powder material and are defined as a mass comprising either granular or powder material which has been compacted into an integral solid mass, preferably with the use of a binder. The block is preferably made into a solid mass by the application of heat. The materials that preferably comprise the block include granular activated carbon, powder activated carbon, clay or ceramic, more preferably powder activated carbon (PAC). Any binder which helps the granular or the powder material to bind into an integral mass may be used, but it is preferred that when the block comprises activated carbon, the binder used is a polymeric binder. Preferred binders include polymers made of one or more of the monomers: olefins, bisphenol. The olefins may be ethylene, propylene, butene. Other polymers such as polyester, cellulose, resins etc may also be used.
The filter material may comprise a biocide that may be an organic biocide such as trichloro-carbanilide or trichloro-2-hydroxy diphenyl ether, or a metallic biocide such as silver or its salts, polyaluminium chlorides, or aluminium hydroxides.
The blocks are preferably adhered to a base plate provided with an orifice for the flow of water. The base plate is suitably made of polypropylene, polyethylene, acrylonitrile butadiene styrene copolymer, or styrene-acrylonitrile copolymer or polymers with similar mechanical properties.
The two blocks are preferably detachably secured to the base of the top chamber e.g. by screwable threaded joints or by snap-fit arrangement.
The shape of the carbon block does not limit the scope of this invention and it is possible to have carbon blocks of the same or different shapes in the top and the bottom chamber, without departing from the scope and spirit of the invention.
As outlined above, it is desirable that the distance over which the water traverses through each of the blocks when it enters at any point on the inlet surface of the block is substantially the same. This may be achieved by configuring the blocks such that the shortest distance between the inlet surface and the outlet surface is substantially constant over the entire block. For that purpose blocks with a circular horizontal cross section are preferred and particularly filter blocks of which the outer surface defines a cylindrical or hemispherical surface.
Preferably, the blocks are so configured that they each have a cavity, the cavity of the upper block being defined by the inner or outlet surface of that block and the cavity of the lower block being defined by the inner or inlet surface of that block. The cavities of both blocks are so connected that the water exiting the upper block flows straight into the cavity defining the inlet surface of the lower block.
More particularly the block are so configured that the inner and outer surface define two concentrical cylinders or hemispheres, whereby the space between the cylinders or hemispheres is occupied by the carbon block. In these embodiments the blocks are preferably so mounted that the inner surface of the upper block is the outlet surface of that block whereas for the lower block the inner surface is the inlet surface.
The shape of the top chamber is preferably so constructed that the percentage of the volume of water up to the height of the carbon block with respect to the total volume of water in the top chamber is significantly lower as compared to a corresponding percentage for any other section of the same height of the top chamber. Such a shape of the top chamber ensures that a larger amount of the water in the top chamber is subjected to a higher gravitational head as compared to shapes of top chambers in known water purification devices, thereby ensuring high flow rate over an entire batch of water to be purified.
The bottom chamber could be of any shape capable of storing water flowing from the top chamber.
Thus according to a preferred aspect of the invention, there is provided a gravity fed water purification device comprising a top chamber and bottom chamber wherein
the base of the said top chamber is provided on either side with a filter
said blocks having an inlet surface and an outlet surface whereby the
entire volume of water existing the outlet surface of the block in the top
chamber enters the inlet surface of the block in the bottom chamber and
wherein the top chamber has upwardly diverging sidewalls.
The details of the invention its objects and advantages are explained hereunder in greater detail in examples:
A gravity fed water purification device as per figure-1 with the radius of the hemisphere defining the inlet surface of the block in the top chamber and the outlet surface of the block in the bottom chamber being 40 mm was constructed. The radius of the hemisphere defining the outlet surface of the block in the top chamber and the inlet surface of the block in the bottom chamber was 15 mm.
The blocks were constructed by the following method. 70 wt% of powder activated carbon (PAC), of particle size distribution such that 92% is retained on 200 mesh and 99% passes 60 mesh, and 30 wt% of a binder (Ultra High molecular weight polyethylene) were mixed. The mix was placed in a mould and heated to 250°C for 2 hours. The block was cooled and demoulded and a base plate provided with a threaded joint was glued to the base using a hot melt adhesive. The two blocks were screwed to threaded joints provided in the base of the top chamber.
A known gravity fed water purification device was constructed in which a single carbon block was prepared with the radius of the inlet surface of the hemispherical block of 60 mm and the radius of the hemisphere defining the outlet surface was 10 mm. The block was prepared using the same materials and the same process as in Example-1.
Eight liters of test water containing 60,000 polystyrene latex microspheres per
liter was prepared. The polystyrene latex beads were 3 urn in diameter and
impregnated with a UV fluorescent dye and are electrically neutral particles. This water was poured to a height of 20 cm in the top chamber. The flow rate and the filtration efficiency when this test water was filtered using device of Example-1 and Comparative Example-A were determined as described below and are summarized in Table 1.
Determination of filtration efficiency:
The filtrate was collected as four, two-liter batches in different beakers. A representative sample of 20 ml of the filtrate from each of the beakers was collected while stirring and passed through a membrane filter of 0.4u pore size such that the microspheres were retained on the surface of the membrane filter. The membrane filters were mounted on glass slides for microscopic counting.
The UV fluorescent dye in the microspheres has excitation maximum of 441.53 nm and emission maximum of 485.56 nm, which falls in the UV light range. Counting of the microspheres trapped in the membrane filter is done under a microscope with UV illumination facility and the results are averaged over the four readings. Log reduction is computed in the following manner.
Log Reduction = log [(Initial Count per ml) / (final count per ml)]
Path length is defined as the shortest distance between the inlet and the outlet surface of each block.
Total Path length (cm) Total Block
(ml) Log reduction of microspheres
Example 1 5 112.5 2.8
Comparative Example A 5 450 2.6
The data in Table 1 indicate that the removal efficiency of particulate matter in both the cases is comparable. However in the case of the Comparative Example-A, four times as much material (viz. PAC and binder) had to be used to prepare the block as compared to the blocks of Example-1, thereby providing highly improved purification efficiency per unit mass of the filter material used.
Example-2: A gravity fed water purification device as per figure-2 with the radius of the cylinder defining the inlet surface of the block in the top chamber and the outlet surface of the block in the bottom chamber being 50 mm with a height of 40 mm was constructed. The radius of the cylinder defining the outlet surface of the block in the top chamber and the inlet surface of the block in the bottom chamber was 10 mm. The blocks were constructed using the same composition and process as per Example-1.
A gravity fed water purification device was constructed in which the two annular cylindrical carbon blocks prepared for Example-2 were glued end on end such that an effective cylindrical carbon block with a height of 80 mm was prepared. In this case the two blocks used were identical to those in example 2 except that they were on the same side of the dividing surface. The blocks were prepared using the same materials and the same process as per Example-2.
Tests were carried out with the devices of Example-2 and Comparative Example-B, using the same procedure as described for Example-1 and these are summarized in Table 2.
Total Block Volume (ml) Log reduction microspheres
Example 2 754 4.8
Comparative example B 754 3.2
The same amount of material was used in both the water purification devices of Example-2 and the comparative Example-B. The data in Table-2 indicates that the removal efficiency of particulate matter is superior in Example-2 compared to Comparative Example-B.
Filter blocks were prepared by the technique described in Example 1. However prior to forming the powdered activated carbon into a block, the material was modified by treating it with a solution of Silver Nitrate followed by treatment with a solution of Potassium Bromide. These treatment steps result in the precipitation of Silver Bromide on the PAC at a level such that the silver bromide is 2% of the weight of the total material. This modified material was formed into blocks, after repeated water washing and drying. Two filters were assembled in the configuration shown in figure 1.
A conventional filter having the same concentration of silver bromide as
Example-3 was prepared as comparative example-C.
The gravity filtration devices of Example-3 and Comparative Example-C were tested for filtration of E Coli and bacteriophage MS2 by the following tests.
Tests carried out:
Filtered water samples contaminated with E Coli were tested under the following two conditions:
E Coli (initial):
An eight-liter sample of test water contaminated with E-coli was passed through
freshly prepared filters and the filtered water tested for presence of E-Coli.
E Coli (after 300 liters):
Three hundred liters of tap water was first passed through a filter. Eight liters of input water after this was seeded with e-Coli and the filtrate was tested for the presence of E-Coli.
An eight-liter sample of test water contaminated with bacteriophage MS2 was passed through freshly prepared filters and the filtered water tested for presence of MS2.
The method used to measure the amount of E-Coli and MS2 is given below. The results of the tests are summarized in Table 3.
Test Method: (For E Coli)
The input water was contaminated with E-Coli with a resulting count of 107 E-Coli/I. This water was passed through the filtration system described in example 3 and the comparative example C. The filtrate was plated to determine the number of colony forming units that survived.
Test Method (for bacteriophage MS2)
Input water was seeded with bacteriophage MS2 to a level of 107 /ml. The filtrate
was again cultured to obtain the counts of surviving MS2.
Log R E Coli (initial) Log R E Coli (after 3001) Log reduction
Example 3 7 7 7
Comparative example C 7 4.9 4.9
Example-3 shows that the purification device of this invention leads to an increased performance for bacteria and virus removal when compared to a conventional filtration system. It also shows that the lifetime of the filter system, defined by the number of liters over which complete removal of E Coli can be obtained, is significantly enhanced by the use of the purification device as per this invention.
Importantly, the present invention provides for significantly reduced usage of filter material for obtaining the same filtration performance. This is especially significant when the filter material is coated with expensive biocide like silver or its salts, in which cases the cost can be significantly reduced.
WE CLAIM :
1. A gravity fed water purification device comprising a top and a bottom chamber wherein either side of the base of said top chamber is provided with filter blocks each having an inlet surface and an outlet surface whereby the outlet surface of the upper block and inlet surface of the lower block are so connected that the water exiting the outlet surface of the upper block is laid straight to the inlet surface of the lower block and both blocks being configured such that shortest distance between the inlet surface and outlet surface is substantially constant for each block.
2. A water purification device as claimed in claim 1 wherein the blocks have a circular horizontal cross section.
3. A water purification device as claimed in claim 2 wherein the inlet surface of the block in the top chamber and outlet surface of the block in the bottom chamber define a cylindrical surface.
4. A water purification device as claimed in any of claims 1-3 wherein said filter blocks are configured to have a cavity that defines the outlet surface of the block in the top chamber and the inlet surface of the block in the bottom chamber.
5. A water purification device as claimed in any one of the preceding claims wherein the filter block comprises activated carbon or ceramic.
6. A water purification device as claimed in claim 5 wherein the activated carbon is powdered activated carbon.
7. A water purification device as claimed in claim 5 or claim 6 wherein the filter block include a binder.
8. A water purification device as claimed in claim 7 wherein the binder is a polymeric binder.
9. A water purification device as claimed in any one of claims 5 to 8 wherein the activated carbon comprises a biocide.
10. A water purification device as claimed in claim 9 wherein the biocide is a metallic biocide.
11. A water purification device as claimed in claim 9 wherein the biocide is an organic biocide.
12. A water purification device as claimed in any one of the preceding claims wherein the volume of the water capable of being contained up to the height of the block in the top chamber is less than the volume of water capable of being contained over any other section of the top chamber corresponding to the same said height.
Dated this 22nd day of September 2005.
Of S. MAJUMDAR & CO.
|Indian Patent Application Number||1043/MUM/2004|
|PG Journal Number||06/2009|
|Date of Filing||30-Sep-2004|
|Name of Patentee||HINDUSTAN UNILEVER LIMITED|
|Applicant Address||HINDUSTAN LEVER HOUSE, 1 65/166, BACKBAY RECLAMATION, MUMBAI-400 020.|
|PCT International Classification Number||C02F1/26 C02F9/00|
|PCT International Application Number||N/A|
|PCT International Filing date|