MXPA00003340A - Apparatus and method for the purification of water - Google Patents

Abstract

A domestic apparatus for purifying drinking water, comprising a feed water inlet and a purified water outlet, a filter device comprising prefilter means (52) and microporous membrane filter means (53) interposed between said inlet and said outlet, and means for driving the water through said filter at a constant flow rate (51). A method of purifying drinking water, which comprises causing the water to flow at a constant flow rate through a purification filter device comprising prefilter means and microporous membrane filter means.

Description

APPARATUS AND METHOD FOR WATER PURIFICATION Field of the Invention The present invention relates to an apparatus for the purification of rinsing, which may be or be infected by microorganisms, and converted into potable water, and a method for operating it.

Background of the Invention In many locations, a reliable and safe co-water supply is not available. A water distribution system may be lacking or frequently, such a system may exist, but it supplies water that is not, fi may not be safe and suitable for drinking because it is contaminated particularly by microorganisms. The problem of water supply; Safe drinking in these locations, has received ample attention and found a variety of solutions in the art. One of the means that can be used is filtration. In most cases, the filters used in the water purification apparatus operate in a constant pressure mode, that is, the filter is placed in a constant pressure source and is allowed to filter the water until its range of iltration is less than an unacceptable predetermined value. In some cases, some control of the flow range is provided. For example, in U.S. Patent 5,503,735 a lipid purification system is described which provides a reverse osmosis filter membrane in a filter cartridge. Not all water passes through the membrane, and the water that does not pass through the membrane passes through a pressure release valve, which can be adjusted for water pressure and flow in the system. They employ apparatus ^^ i® maintain a range of constant flow and variable pressures in the systems where water flows, for example, in irrigation systems. The processes for controlling the flow rate through the filter of infiltration filter apparatuses are also known. One of said apparatuses is described in the US Patent USP 5,238,559. JP 05185070 (Kokai No. 5-185070) notes that in household water purifiers, the filter module must be replaced when the water flowing through it has exceeded the absorption capacity of the absorbent interior of the module , and that water purifiers are known with the capacity to show on screen the moment of replacement of the filter module. However, it is said that known devices are not reliable because they only measure the time of the water flow and do not provide a reliable indication due to fluctuations in the water flow range. Therefore, said request proposes a domestic water purifier which comprises a valve of constant flow range, a sensor to detect the start and stop of the water flow and generate the corresponding signals, and means to measure an operating time integrated based on said signals and that show a signal when said integrated time has reached a previously established value. The application shows several valve structures of constant flow range, but as far as the filter module is concerned, it does not show the structure and states that the invention can utilize various structures of the prior art. The water purification systems of the prior art, in particular those which are not intended to remove only solid substances, but which remove microorganisms and supply completely potable water, are not completely satisfactory, due to various points of view. Its production output is generally low, so filters must be changed frequently, must have a large surface area and are very expensive. One purpose of the present invention is to provide an apparatus for the purification of drinking water, and which is free from defects of existing apparatuses. Another purpose of the present invention is to provide a method for the purification of water, which is free from defects of prior art methods. It is a further purpose of the present invention to provide a method for optimizing the operation of an apparatus for the purification of drinking water. Other purposes and advantages of the present invention may be appreciated as the description is read.

Summary of the Invention The present invention provides an apparatus for water purification, which comprises a water feed inlet and a purified water outlet, a filter having deep filter layers and microporous filter membrane layers interposed between said inlet and said outlet, means for conducting the water through the filter in a constant flow range, means for monitoring the time since the installation of the filter, means for monitoring the aggregate time during which the water has flowed through the filter, and means for preventing the flow of water through the filter when any of said times has reached a predetermined threshold value. The means for conducting the water through the filter in a constant flow range can comprise means for applying pressure to the filter and means for controlling the flow range, independently of the changes in pressure drop in all the filter layers, such as a flow limiter of a known type. In a preferred embodiment of the apparatus, the depth filter and the microporous membrane mean that they are structured and assembled as will be described below, to constitute a filter apparatus, but said filter apparatus, is not, by itself, a part of the filter apparatus. of the invention and is not claimed herein as such; and the apparatus of the invention could be supplied with filters of different structure, provided that they comprise members of depth filter and microporous membrane filter, through which water flows successively to be purified. The filter apparatus of the preferred embodiment is composed of a number of filter element components, although said filter element itself would be capable of a filtering action. Said filter element comprises: a) A deep inner drainage layer, preferably a substantially open plastic net. b) Two layers of microporous membrane, each preferably supported on a layer of support material placed between them and said drainage layer, and more preferably, having a retention capacity greater than 95% for microorganisms, said two layers being symmetrically placed adjacent to the two sides of said drainage layer; c) Two layers of a depth filter or prefilter (these two terms being used as synonyms in this description), preferably a glass fiber filter, placed symmetrically adjacent to the two outer sides of said microporous membrane layers. d) - said microporous membrane layers and said depth filter layers being sealed together along an upper end, preferably extending above the top of said drainage layer and said layers of support material, if present; e) - said drainage layer and said microporous membrane layers, as well as said layers of support material, if present, extending below the bottom of said layers of the depth filter, said microporous membrane layers being sealed to said depth filter layers at the bottom of the latter; and f) - said microporous membrane layers and said depth filter layers being wider than said drainage layer, and said layers of the support material, if any, and being sealed together along their lateral ends. The terms "upper" and "bottom" refer to the position that the filter element will have in the complete filter apparatus. Said filter apparatus comprises a base plate having a central opening and an upper surface, and a plurality of elements that were previously defined, distributed parallel to each other and perpendicular to said base plate, and passing through said central opening thereof. with the bottom of its depth filter layers at the level of said top surface of said base plate, said filter elements being inserted in said base plate by filling with adhesive the space between them and the inner end of the central opening of said base plate. Said filter further comprises a sealed cover, in which the base plate is tightly enclosed with the filter elements inserted therein. In a variant of said filter, the microporous membrane layers and the depth filter or the prefilter layers of the filter element mentioned above are sealed together by means of an adhesive. In another variant of said filter, the layers of the depth filter are laminated, each comprising a layer of porous thermoplastic material, and the microporous membrane layers and their support layers are thermoplastic. If the melting temperature of the microporous membrane layer is at least 50% higher than the temperature of at least one of the remaining thermoplastic layers, the layers can be sealed together by means of the application of pressure and heat as explained better later. In a typical embodiment of the present invention, the apparatus comprises: A pre-filter; A membrane filter, which can be separated from or combined with the prefilter in a single structural unit; A pressure regulator; A fluidometer; A chronometer; A purified water outlet; and Valves and pressure gauges, which may be required. The present invention also provides a water purification method for drinking, which comprises, causing the water to flow in a constant flow to purification range, which comprises a depth filter or prefilter and microporous membrane filter means, monitoring the time to installation of the filter, monitoring the time added during which water is flowing through the filter, and preventing the flow of water through the filter when any of these times has reached a predetermined threshold value. The means for conducting the water through the apparatus in a constant flow range may comprise means for feeding the water to be purified by the application of pressure and means for controlling the flow range, such as a flow limiter of a known guy. The depth filter means and the microporous membrane means are preferably structured and assembled in the same manner as the filter element defined below, so that the filter as a whole is the filter apparatus defined above, but the The method of the invention would be carried out with an apparatus comprising filters of different structure, as long as they comprise depth filter and microporous membrane filter means, through which the water to be purified flows. The method of the present invention is focused on the purification of water for drinking, and the purification of water that is not for drinking, is discarded in this description. The expression "water purification for drinking", as used in the present description and the claims, includes both the drinking water supply which is adapted to drink, and to increase the purity of the water which is already for drinking, in the extent possible. It would be desirable for the purified water to be substantially sterile.

Brief Description of the Drawings Figure 1 is a view ei? cross section of the filter element according to a mode of the presemf®; Invention. Figure 2 is a front view of the same element; Figure 3 is a perspective view of a filter apparatus, according to an embodiment of the present invention, in an intermediate stage of its manufacture; Figure 4 is a cross-sectional view of a filter apparatus according to an embodiment of the present invention, taken in a plane passing through the center lines of the filter elements; Figure 5 is a cross-sectional view of the filter apparatus of Figure 4, taken in a plane parallel to the filter element and passing through the center line of the filter element; Figure 6 is a cross-sectional view similar to Figure 1, of a filter element according to a different embodiment of the invention. Figure 7 is a diagram in which a graph of the Total Production Output is made to reach a Pressure Drop of 2.5 atm (2.5 x 101325 Pa), in thousands of liters, against the Flow Rate in cm / min; and Figure 8 is a schematic block diagram illustration of an apparatus according to an embodiment of the present invention.

Detailed Description of the Invention As illustrated in Figure 8, an apparatus according to the present invention comprises an inlet 50, preferably including a pressure gauge and a pressure regulator, of any known type. The pressure to conduct the water through the being provided by the water source itself, such as by a tap or a water tap or, if it is not available, or is insufficient, by a pump 51 of any suitable type. 52 and 53 indicate, respectively, a prefilter and a filter membrane, which may be integrated with a single filter apparatus 54, as indicated by the dotted lines of Figure 8. The filter is preferably followed by a pressure gauge of outlet 55 and by a constant pressure regulator 56. A needle valve 57 can be provided after said regulator. From this, water flows through the unit 58, which is preferably an integrated component comprising a fluidometer, a stopwatch and a shut-off valve, and reaches the outlet. Figures 1 to 5 illustrate a filter apparatus used in a preferred embodiment of the apparatus of the present invention. As stated earlier in this description, said filter apparatus, by itself, is not a part of the present invention and is the subject matter of another application, also pending. In said figures, a filter element 10 comprises two outer layers of depth filter or pre-filter 11 and 11 ', which is preferably made of glass fiber. Inside the layers 11 and 11 ', the filter element comprises the layers 12 and 12' of the microporous membrane, preferably having a retention capacity of 95% microorganisms, which are respectively supported on the support materials. and 13 '. All the aforementioned layers are arranged symmetrically around a substantially open plastic net 14, which constitutes a drainage layer for removing the liquid that passes through the layers 11-11 ', 12-12' and 13-13 ' previously mentioned. Layers 11-11 'and 12-12' are congruent and sealed together by means of an adhesive, particularly a hot melt adhesive, or by welding. The plies 1 il 'of the depth filter and the microporous membrane layers 12-12' are also sealed together at the ends 22. The drainage layer 14 and the support material layers 13-13 'do not extend to the upper part of the element, but to the seal 15, although, in one embodiment of the present invention in which welding was used, the layers 13 and 13 'may reach the end seal and be sealed together in a thermoplastic manner. In Figures 1 and 2, both layers of the prefilter 11-11 ', do not reach the bottom of the element, but the microporous membrane layers, the layers of support material and the drainage layers protrude beyond them towards the bottom. The depth filter layers 11-11 'are sealed at 20-20' to the layers 12-12 'of the microporous membrane. The support layers 13-13 'and the drainage layer 14 are narrower than the other layers and do not take part in the seals 22. A number of filter elements 10 are connected to provide a filter apparatus, as is shown in FIG. illustrated in Figures 4 and 5. Figure 3 indicating an intermediate step of manufacturing the filter apparatus. The latter is indicated generally with the 30, comprises a base plate 31 having a central opening 32, whose peripheral end is indicated with the 33. The filter elements 10 are passed through said central opening 32 and placed in a such that their ends 20 are at the same level as the upper end of the base plate 41. In Figure 3, the central opening 32 has not been filled with filter elements 10, but a space was left therein at the same time. front of the appliance as shown in the drawing.

In Figures 4 and 5, the filter and the central opening 32 have been filled with the elements 10. The filter elements are in place, inserted into the base plate filling the vacuum space and the inner end 33 of the filter. the opening 32 with a suitable adhesive, so that there is no path for the flow of liquids between the elements 10 and the base plate 31. The base plate 31 is subsequently mechanically sealed inside a suitable filter cover 35. The cover is open at the top, as indicated by 36, to provide an entry for the water to be filtered. The water passes through the several layers of each element 10, entering from the outer depth layers 11-11 'and coming out through the drainage layer 14 and reaches an opening of the cover 35, indicated with the 37, which is the leakage of the filtered water. In a variant of the filter element, illustrated in Figure 6, the prefilter layers are replaced by laminated glass fiber filter layers 40-40 'and the porous synthetic layers 41-41' of melting temperature T1, the microporous membrane layers 42-42 'of thermoplastic material having the melting temperature T2 are prepared, and the support layers 43-43' are also made of porous synthetic material of melting temperature T3 and are congruent with the preceding layers along the ends 15 and 22 (the latter are not shown in this figure, but in Figure 2). Provided that T2 is at least 50 ° C higher than Ti or T3, then the seams of element 15 and 22 mentioned above can be created in a single step by means of pressure welding with a hot die whose temperature is higher than any of Ti and T3.

The drinking water is purified according to the present invention by passing it through a filter element or a plurality of filter elements in a constant flow range. Including said filters, a depth filter and a microporous membrane, it has been found that the operation of the filter in a constant flow range is highly advantageous with respect to the operation at constant pressure, since a filter apparatus operated at a range of Constant flow requires a much smaller surface area of the membrane, up to ten times smaller, to achieve the same overall output as a device operated at constant pressure. A filter apparatus comprising an apparatus according to an embodiment of the present invention, having a filter area of 0.05 square meters, can produce 3,000 liters of filtered water in a constant flow rate of 2 liters / minute, when it operates with tap water with an average filtration rate value of 10, and does not need to be changed, before producing said volume of filtered water, more than once every three months. When a filter comprising a prefilter and a meproporous membrane is operated at constant pressure, the following phenomenon occurs. At the beginning of the process, the hydraulic resistance of the filter is the lowest, the flow range is at a maximum and the efficiency of the prefilter is lower, because it decreases as the speed of the particles increases. As a consequence, the particles pass through the prefilter and are captured on the surface of the microporous membrane, blocking the pores and reducing the flow range. As filtration continues, the velocity of the fluid continues to decrease, and as a result, the capture efficiency of the prefilter finally improves. The resistance of the pre-filter and the membrane increases until the combined resistance is such that the filter no longer provides a useful flow range. When operating at a constant flow rate, it is possible to choose the flow rate so that a maximum number of particles are captured by the prefilter from the beginning of the filtration process, so that the total production output of the filter is increased considerably. The general method of optimizing the operation of an apparatus according to the aforementioned preferred embodiment, comprising a filter as described above, and more generally of a filter comprising a depth filter and a microporous membrane filter, consists of the following steps. 1. A filter element that is initially operating in some convenient constant flow range is tested until a predetermined total pressure drop has been reached throughout the filter. 2. The results are plotted in a graph as in Figure 7, in which the Total Production Output has been plotted against the Flow Rate (obtained by dividing the flow range between the surface area of the filter element). 3. The test continues, either changing the constant flow range or changing the surface area of the elements, until Figure 7 has been generated in its entirety. 4. The desired total output output is chosen and then a convenient combination of constant flow rate and surface area of the membrane element is selected.

. The filter is operated in the wof? D constant flow with the number 4 above. Figure 7 shows the data for the Total Production Output (for a pressure drop of 2.5 bar - 1 bara = 101325 Pa) for a flat sheet membrane filter element that contains a glass fiber depth filter and a microporous membrane with a nominal pore size of 0.2 microns. Anyone can clearly notice that when operated at constant flow, below the critical speed, the Total Production Output of the membrane filter can be increased several times. The pre-filter or depth filter layer 12 is preferably any pre-filter material known in the art and could include, but is not limited to, organic or inorganic, porous or particulate material, such as glass fiber, carbon, cellulose, polyolefins and others. polymeric synthetic materials. The prefilter can also be in the form of a block of highly porous and compressed fibers, microfibers or particles, containing pores of at least 5 times the diameter of the pores of the membrane, or in the form of a woven material or not. woven, all of them known in the art. A non-woven glass fiber material, which does not contain binding agents, with a thickness of approximately 450 x 10 ~ 6 and a nominal particle removal rate of 1 miera, is especially preferred for use in water filtration of the key. The microporous membrane layer 14 is preferably a microporous filter with pores between 0.05 x 10"6 m and 0.45 x 10" 6 m, and which is generally manufactured from high temperature thermoplastic polymers, such as polysulfone, nylon, polyvinylidene fluoride, or inorganic materials, such as ceramic materials, or metals and has a water permeability of between 0.50 - 30 cc / cm2 / sec / atm, coST SO? generally known in the art, and those described in chapters 2 to 4 of "Filtration in the Pharmaceutical Industry", by Theodore H. Melzer, Marcel Dekker Inc., N: Y :, Registered Rights in 1987, ISBN 0-8247 -7519-8. The support layers of the membrane 13-13 'are preferably made of a synthetic, woven or non-woven material, which does not swell or deform in the water. The nonwoven materials prepared from polyolefins are particularly useful for this purpose, because their melting temperature range is well below the range of many of the polymers used to make the membrane layer 14. Ideally, this layer would have an maximum permeability, but in any case, not less than ten times the permeability of the supported membrane layer. The plastic net 14 for separating the layers of the filter material, in order to create a liquid path, can be achieved in a large number of thermoplastic materials, prepared by extrusion or by other processes, such as continuous weave of plastic filaments, and they are well known in the art. Examples of such material are polypropylene networks manufactured by Nalle Plastics, Austin, Texas, under the trademark Naltex.

The following example illustrates the operation of an apparatus according to the aforementioned preferred embodiment of the present invention.

A membrane filter element with a filter surface area of approximately 24 cm 2 was prepared from a glass fiber pre-filter material A / E (Gelman Sciences, Ann Arbor, MI, USA), a non-woven polypropylene material as the support layer of jppe brana and a network (Nalle Plastics, Texas, i "USA) to create a drainage path, epoxy adhesive was used to create the glued seams A number of filter elements were glued with the epoxy adhesive in a plastic base plate with a thickness of 4 mm to form a filter assembly, in order to create the filter assemblies with effective surface areas of filtration of between 50 and 500 cm2. By direct contact with approved liquid food, they can be obtained in the market, for example from the companies Bostík, HB Fuller and Callano.Each filter assembly was secured in an appropriate cover and its integrity was tested first medium It is a bubbling point technique. After a small wash with water, the inlet of the cover was connected to a source of gas pressure, and the outlet pipe that carries the filtered water from the cover was placed in a water container. The gas pressure was slowly increased until it was seen that the first stable bubble current was emitted from the outlet tube of the cover. It was found that this pressure, 3.2 atm. (3.2 x 101325 Pa), which we refer to as the bubble point, was within 0.1 atm (0.1 x 101325 Pa) of what was specified by the manufacturer of the Supor 200 membrane, thus confirming that the cover and the Filter assembly were integral, and that the membrane was of the designated nominal pore size. A water purification apparatus according to an embodiment of the present invention, which comprises said filter assembly, was tested in a constant flow range of 2 liters per minute. The pressure gauges that were before and after the device measured the pressure drop and the test was concluded when the pressure drop exceeded 1.6 bar 1 bara = 101425 Pa). An integrated water meter measured the cumulative pressure output. The test data of these assemblies are shown in Figure 7. Water quality was monitored periodically by sediment density and filtration rate technique, and it was found that the index varies between 8 and 15 during the day , with an average value of 10-12. With reference to Figure 7, a filter can be designed that uses a minimum amount of prefilter and membrane filter in order to achieve an output production goal and filter flow range previously determined: for example, a filter like the one described here, which is required to provide a total production output of 10,000 liters at a maximum pressure drop of 2.5 atm. (25 x 101325 Pa) and a flow rate of 2 liters per minute. As illustrated in Figure 7, the maximum flow velocity of said production output should not exceed 8 cm / min. Since the required flow range is 2000 cc / min, the required surface area of the filter (both the prefilter and the membrane filter) is the total flow range divided by the speed, or 250 cm2. Of course, it is possible to provide a larger area in order to ensure the operation of the filter and take into account possible variations in water quality (which, in the case of the data of Figure 7, was found to be fairly constant). As a specific embodiment of the present invention, with reference to the schematic drawing of Figure 8, a standard centrifugal pump with a capacity of 10-20 liters per minute at a pressure of up to 10 atm was attached. (10 x 101325 Pa), to a 50-liter tank which was constantly refilled from a source of water from the Mam, the valve outlet was followed by a standard water regulator of 0-6 atmospheres equipped with a pressure gauge (Braukmann GbH, Ger.) And adjusted to Li ||? "Pressure of 4 atmospheres, this was connected to a filter cover containing a manufactured filter element, following the procedure described in the present invention. the output was followed by a second regulator set at 5 atmospheres, the lowest setting at which the regulator would operate effectively, followed by an integrated water meter (Arad Ltd., Israel) and a ball-operated fluidometer with a integral needle valve (Fisher Porter, USA) A separate electronic controller controlled a standard solenoid valve for closure in accordance with time Although the embodiments of the invention have been described for purposes of illustration, it should be understood by those skilled in the art. in the art, that the invention can be carried out with many modifications, variations and adaptations without departing from the scope of the appended claims.

Claims (10)

Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property.

1. An apparatus for the purification of drinking water, comprising a water supply inlet and a purified water supply outlet and a filter apparatus interposed between said inlet and said outlet, characterized in that the filter apparatus comprises pre-filter means and a microporous membrane and in that the apparatus additionally comprises means for regulating the flow of water through said outlet in a constant flow range for the useful life of said filter apparatus.

2. The apparatus as described in Claim 1, further characterized in that it additionally comprises means for monitoring the time from the installation of the filter apparatus, means for monitoring the aggregate time during which the water has flowed through the filter apparatus , and means for preventing the flow of water through the filter apparatus when any of said times has reached a predetermined threshold value.

3. The apparatus as described in Claim 1, further characterized in that the means for causing the water to flow through the filter in a constant flow range comprise means for applying pressure to the filter and means for controlling the range of f fó regardless of changes in pressure.

4. The apparatus as described in Claim 1, further characterized in that the means for controlling the flow range comprises a flow limiter.

5. A domestic appliance for the purification of drinking water, as described in Claim 1, further characterized in that the filter apparatus comprises at least one filter element comprising: 1) A deep inner drainage layer; 2) Two layers of microporous membrane, symmetrically placed adjacent to both sides of said drainage layer; 3) - Two layers of a prefilter, placed symmetrically adjacent to the two outer sides of said microporous membrane layers. 4) - said microporous membrane layers and said prefilter layers being sealed together along an upper end, 5) - said microporous membrane layers being sealed to said depth filter layers at the bottom of the latter; and 6) - said microporous membrane layers and said prefilter layers being sealed together along a lateral end. and said filter apparatus further comprising a) one or more said filter elements arranged parallel to each other and perpendicular to the base plate which has a central opening and an upper surface, and traversing said central opening thereof with the bottom of its prefilter layers at the level cte the upper surface of said base plate; b) said filter elements being integrally adhered to the base plate by filling with adhesive the space between them and said inner end of said central opening of the base plate. c) said filter elements and said base plate being integrally sealed in a cover for liquids that can be pressurized so that the entrance of the unfiltered water is forced to pass through the filter elements in order to exit of the cover in a filtered state.

6. A method for purifying water, which comprises causing the water to flow in a constant flow range through the purification filter apparatus comprising prefilter means and microporous membrane filter media.

7. The method as described in Claim 6, further characterized by comprising time monitoring from the installation of the filter apparatus, monitoring the aggregate time during which water is flowing through the filter apparatus, and avoiding the flow of water through the filter apparatus when any of those times has reached a predetermined threshold value.

8. The method of operation of a filter as described in Claim 5, further characterized by comprising the following steps: I. Operation of a member of o * e? a range of initial constant flow until it has been reached? 'the entire filter a previously determined total pressure drop. II. The monitoring and plotting of the output graph of total production against the flow velocity, obtained by dividing the flow range between the surface area of the filter element, during said operation. III. Repeat the previous operations at different flow rates, determined by the change in the flow range or the surface area of the filter, and make the graph of the total production output as a function of the flow velocity. IV. Select the desired production output, and read from the aforementioned chart, the corresponding flow velocity. V. Select a combination of flow range and the surface areas of the filter element corresponding to the selected production output.

9. The water purification method for drinking, substantially as described and illustrated.

10. An apparatus for water purification, substantially as described and illustrated. A household appliance for the purification of drinking water, which comprises a water supply inlet »| ^ |? ' purified water outlet, a filter apparatus comprising prefilter means (52) and microporous membrane filter means (53) interposed between said inlet and said outlet, and means for conducting the water through said filter in a range of constant flow (51). A method for the purification of drinking water, which comprises causing the water to flow in a constant flow rate through the purification filter apparatus which comprises prefilter means and microporous membrane filter media.