WO2007003383A1 - A filter assembly and a method of filtering liquids - Google Patents

A filter assembly and a method of filtering liquids Download PDF

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Publication number
WO2007003383A1
WO2007003383A1 PCT/EP2006/006406 EP2006006406W WO2007003383A1 WO 2007003383 A1 WO2007003383 A1 WO 2007003383A1 EP 2006006406 W EP2006006406 W EP 2006006406W WO 2007003383 A1 WO2007003383 A1 WO 2007003383A1
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WO
WIPO (PCT)
Prior art keywords
filter
filter assembly
block
liquid
assembly
Prior art date
Application number
PCT/EP2006/006406
Other languages
French (fr)
Inventor
Jaideep Chatterjee
Velayudhan Nair Gopa Kumar
Original Assignee
Unilever N.V.
Unilever Plc
Hindustan Unilever Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Unilever N.V., Unilever Plc, Hindustan Unilever Limited filed Critical Unilever N.V.
Publication of WO2007003383A1 publication Critical patent/WO2007003383A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
    • A61L2/02—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor using physical phenomena
    • A61L2/022—Filtration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D25/00—Filters formed by clamping together several filtering elements or parts of such elements
    • B01D25/02—Filters formed by clamping together several filtering elements or parts of such elements in which the elements are pre-formed independent filtering units, e.g. modular systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/01—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements
    • B01D29/03—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements self-supporting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/50—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with multiple filtering elements, characterised by their mutual disposition
    • B01D29/56—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with multiple filtering elements, characterised by their mutual disposition in series connection
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D35/00—Filtering devices having features not specifically covered by groups B01D24/00 - B01D33/00, or for applications not specifically covered by groups B01D24/00 - B01D33/00; Auxiliary devices for filtration; Filter housing constructions
    • B01D35/30—Filter housing constructions
    • B01D35/301—Constructions of two or more housings
    • B01D35/303—Constructions of two or more housings the housings being modular, e.g. standardised
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B01D39/2055—Carbonaceous material
    • B01D39/2058—Carbonaceous material the material being particulate
    • B01D39/2062—Bonded, e.g. activated carbon blocks
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C02F1/004—Processes for the treatment of water whereby the filtration technique is of importance using large scale industrial sized filters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
    • B01D2239/0604—Arrangement of the fibres in the filtering material
    • B01D2239/0618—Non-woven
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/08—Special characteristics of binders
    • B01D2239/086—Binders between particles or fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/12—Special parameters characterising the filtering material
    • B01D2239/125—Size distribution
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/04—Disinfection

Definitions

  • the present invention relates to a filter assembly for filtration of liquids and more particularly to a cost-effective gravity fed filter assembly that provides water substantially free of particulate contaminants including microorganisms like cysts while maintaining high flow rates.
  • Liquids like water typically contain contaminants, which includes particulate matter, chemicals and microorganisms. In water, especially drinking water, it is desirable to remove the harmful contaminants before consuming them for maintenance of good health.
  • US 5,164,085 (NRG Enterprises, 1992) describes a filter cartridge for water purification consisting of several layers of filter material with successively smaller pore size, with the outer layer being a pre-filtration material with a pore size of approximately 10 microns, a central layer is an extruded carbon filter with a pore size of about 5 microns, preferably with a chemical agent for removal of heavy metals and an inner layer is a ceramic filter with a pore size of about 0.9 microns preferably with impregnated silver for biostatic efficacy.
  • this publication teaches the use of different materials over the various parts, thereby having the problem of manufacturing complexity.
  • US 5,328,609 (Magnusson, 1994) describes a manifold mounted liquid filtration system including a disposable filter cartridge having first and second radial flow filtration stages containing filtration media of uniform porosity.
  • a first stage includes a pair of annular concentrically mounted, fibrous sediment and cast carbonaceous filter media and the second stage includes an annular cast carbonaceous filter medium. While the first stage is used to remove suspended sediments, lead and other heavy metals, the second stage removes suspended bacteria and other organic impurities.
  • the filtration system described in this publication requires the entire filter cartridge to be disposed when completely choked and replaced with a new cartridge that would prove cost-extensive.
  • US 5,151 ,180 (Cuno, 1992) relates to a filter device for use in a residential water supply system which includes a container having an enclosed cavity, and includes a filter unit having a two-stage filter with a first radial flow filter subassembly and a second axial flow filter subassembly.
  • This specific configuration is adapted to minimize the loss in pressure head due to an excessive number of turns usually present in filter devices, thereby providing high flow rates.
  • this filter device minimizes frictional losses with the help of a suitable filter configuration, it is not adapted to filter small microorganisms like bacteria and viruses.
  • US 2003/0213750 (Koslow, 2003) describes a filter medium for enhanced removal of bacteria and virus comprising a microporous structure having a mean flow path of less than or equal to about 1 micron; and a microbiological interception enhancing agent comprising a cationic metal complex capable of imparting positive charge on at least a portion of the microporous structure.
  • the process to make these filters is cost-extensive, complex and requires a high degree of quality control in manufacture which would be difficult to implement in simple household gravity fed water filter systems.
  • JP11104623 (Tokyo Yogyo, 1999) describes an activated carbon block filter water purifier.
  • It comprises an outer cylinder block filter, composed of crushed granular carbon with a low capacity for adsorption but long durability, and an inner cylinder block filter of pitch type fibrous activated carbon with a high capacity for adsorption but low durability.
  • the inner block which exhausts faster, is replaced more often than the outer block, thereby maintaining enhanced adsorption of the impurities.
  • a novel filter assembly comprising a series of detachably connectable filter blocks which is capable of not only filtering particulate matter like dust but also the harmful microorganisms. It is configured to maximize filtration efficiency and throughput of the liquid while minimizing the amount of filter medium being consumed to achieve these ends.
  • Yet another object is to provide a gravity fed filtration system which is simple to manufacture and cost effective. It is a further object of the invention to provide a method of filtering liquids which maintains a high flow rate.
  • the invention provides a filter assembly for filtration of liquids comprising a series of at least two detachably connectable filter blocks having substantially identical composition.
  • the invention provides a combined filter for filtration of liquids comprising: a) a washable or replaceable sediment filter for removing particulates generally above 3 microns and, b) said filter assembly, such that the liquid to be filtered passes through said washable or replaceable sediment filter before passing through said filter assembly.
  • the present invention provides a method of filtering liquids comprising:
  • a water purification device comprising a top chamber for holding the unpurified water and a bottom chamber for receiving the filtered water and a filter assembly or a combined filter as described above wherein the top chamber the filter assembly or the combined filter and the bottom chamber are arranged such that the water passes from the top chamber through the filters to the bottom chamber.
  • the number of detachably connected filters in series could be any number with a minimum of 2.
  • the maximum is preferably up to 20, more preferably 2 to 8 filter blocks.
  • the filter blocks may be made of any material, preferably carbon, ceramic, clay, polyester or polypropylene, more preferably carbon. When carbon is the material used to make the filter block, it is preferred to use activated carbon, more preferred powder activated carbon.
  • the filter blocks for use in the filter assembly of the invention preferably comprise powder activated carbon (PAC) and are preferably made into a block with a binder material which binds the powder into a block under the application of heat.
  • Suitable binder materials preferably have a Melt Flow Rate (MFR) of less than five, preferably less than one.
  • MFR Melt Flow Rate
  • the melt-flow rate (MFR) is measured using ASTM D 1238 (ISO 1133) test. The test measures the flow of a molten polymer through an extrusion plastometer under specific temperature and load conditions.
  • the extrusion plastometer consists of a vertical cylinder with a small die of 2 mm at the bottom and a removable piston at the top. A charge of material is placed in the cylinder and preheated for several minutes.
  • the piston is placed on top of the molten polymer and its weight forces the polymer through the die and on to a collecting plate.
  • the time interval for the test ranges from 15 seconds to 6 minutes in order to accommodate the different viscosities of plastics. Temperatures used are 220, 250 and 300 0 C (428, 482 and 572 0 F). Loads used are 1.2, 5 and 10 kg. The amount of polymer collected after a specific interval is weighed and normalized to the number of grams that would have been extruded in 10 minutes: melt flow rate is expressed in grams per reference time.
  • the binder material is preferably a thermoplastic polymer having a MFR value above described. Suitable examples include ultra high molecular weight polymers, preferably polyethylene or polypropylene. The molecular weight is preferably in the range of 10 6 to 10 9 D. Binders of this class are commercially available under the trade names HOSTALENTM from Tycona GMBH, GUR, SunfineTM (from Asahi, Japan), HizexTM (from Mitsubishi) and from Brasken Corp (Brazil). Other suitable binders include LDPE sold as LupolenTM (from Basel Polyolefins) and LLDPE from Qunos (Australia).
  • the bulk density of the binder material is preferably less than or equal to ( ⁇ ) 0.6 g/cm 3 , more ⁇ 0.5 g.cm 3 , and further more preferably ⁇ 0.25 g/cm 3 .
  • the binder material preferably has a particle size distribution substantially the same as that of the PAC but the amount of particles passing 200 mesh is preferably less than 40 wt%, more preferably less than 30 wt%.
  • the carbon block preferably comprises powder activated carbon (PAC) having a particle size such that 95 wt % of the particles pass through 50 mesh and not more than 13%, preferably not more than 12%, more preferably not more than 10%, passes through 200 mesh.
  • the PAC starting material is preferably selected from bituminous coal, coconut shell, wood, or petroleum tar.
  • the surface area of the PAC is preferably selected such that it exceeds 500 m 2 /g, more preferably exceeds 1000 m 2 /g.
  • the PAC has a size uniformity co-efficient of less than 2, or more preferably less than 1.5, a carbon tetrachloride number exceeding 50%, more preferably exceeding 60%.
  • the PAC preferably has an Iodine number greater than 800, more preferably greater than 1000.
  • the filter medium preferably has a particle size distribution profile across its height. It is preferred that the PAC particles are distributed across the height of the carbon block such that 55 to 80 wt %, preferably 55 to 70 wt% of the PAC particles in the particle size range of 100 to 200 mesh are present in the lower 50 volume% of the carbon block. Also, preferably 55 to 95 %, more preferably 60 to 95 % of the PAC particles in the particle size range smaller than 200 mesh are present in the lower 50 vol% of the carbon block.
  • the weight ratio of binder material to PAC is preferably between 1:1 and 1 :10, more preferably between 1 : 2 and 1 :6.
  • filtration media of the invention it is possible to attain an average flow rate of water, from a starting height (water level) of 200 mm down to 50 mm, under gravity of 100-300 ml/min., preferably 120-200 ml/min., without compromising on the requirements of removal of particulate including microorganisms, and chemical contaminants.
  • the carbon block filter can be of any desired shape and size, depending on the end application and the construction in which the filter block is fitted. Suitable shapes include flat circular disc of low thickness, square disc of low thickness, low height tapered flat disc, cylinder, solid cone, hollow cone.
  • a desirable construction of the filter assembly is such that each carbon block filter is fixedly housed in a collar/bracket, said collar/bracket capable of being detachably connectable to each other with screw-threaded joints or snap-fit joints.
  • the invention is especially suitable for gravity filtration of water that is contaminated with particles including dust and harmful microorganisms e.g. protozoan cyst like Cryptosporidium and Giardia.
  • the filter blocks can be adapted to remove three log removal of cyst. Log removal is defined as the logio (logarithmic to the base 10) of the number of particles fed to the filter divided by the number of particles exiting the filter.
  • the combined filters according to the invention comprise a washable or replaceable sediment filter and a filter assembly according to the invention.
  • the sediment filter is preferably a woven or non-woven fabric, more preferably a non-woven fabric having micropores. This sediment filter ensures filtration of particles generally above 3 microns.
  • the sediment filter can be washed and rinsed under flowing tap water or by using a small amount (0.1-10 g/L) of fabric wash detergent in water.
  • the sediment filter prevents premature clogging of the upper filter block in the filter assembly of the invention. Over time the reduction in flow rate of the liquid through the filter assembly is principally due to choking of the pores in the first filter block. On replacement of the first filter block in the assembly with a new filter block a high flow rate of the liquid through the filter is restored without the need to replace the whole filter assembly.
  • the method of filtering liquid according to the invention simply comprises the steps of passing the input liquid through the filter assembly and removing the first filter block from the assembly and attaching a new filter block to the assembly whenever there is substantial reduction in the output flow rate. This may be done by replacing the first filter block of the assembly with a new filter block. Alternatively, the first filter block may be removed and a new filter block be attached to the bottom of the remaining assembly, thus effectively making what previously was the second filter block now become the first filter block.
  • the first filter block is replaced with a new filter block since according to this method filter assembly need only be detached from the top chamber of the water purification device and the remainder of the assembly may be left attached to the bottom chamber.
  • Fig. 1 is a schematic of a filter assembly with the various carbon block filters assembled.
  • the filter assembly (FA) comprises a series of four carbon block filters (F1 , F2, F3, and F4) each having substantially identical composition and detachably connected to each other.
  • the carbon block filters are fixedly housed in brackets (B1 , B2, B3, B4) which are provided with threaded joints (T) such that said brackets are detachably connectable to each other.
  • the view of Fig. 2 shows the filter assembly disassembled such that the carbon block filter F1 is detached from the filter assembly.
  • the filter assembly (FA) of the invention When in use, the filter assembly (FA) of the invention is attached to the bottom of a reservoir of contaminated water (WT).
  • the water flows in the direction indicated by the arrow (IN) and is filtered after passing through a series of carbon block filters of the filter assembly to exit the filter assembly in the direction marked by the arrow (O).
  • the filter assembly is disassembled, as shown in Fig.2.
  • the filter block (F1) that accounts for the maximum amount of choking is removed and a new filter block attached, either in place of F1 or below F4. Very high flow rates are thereafter obtained.
  • the filter assembly of the invention comprising the detachably connectable carbon block filters in series thus necessitates replacement of only a part of the filter assembly for continuously obtaining high flow rates, as opposed to filters of the prior art where the entire filter would have to be replaced, thereby enabling high cost-effectiveness.

Abstract

The invention concerns a filter assembly (FA) for filtration of liquids comprising a series of at least two detachably connectable filter blocks (Fl, F2) comprising substantially identical composition. The invention further concerns a method of filtering liquids comprising passing the input liquid through the filter assembly and removing the first filter block from the filter assembly and attaching a new filter block to the filter assembly whenever there is substantial reduction in the flow rate of the liquid.

Description

A filter assembly and a method of filtering liquids
Field of invention
The present invention relates to a filter assembly for filtration of liquids and more particularly to a cost-effective gravity fed filter assembly that provides water substantially free of particulate contaminants including microorganisms like cysts while maintaining high flow rates.
Background and prior art
Liquids like water typically contain contaminants, which includes particulate matter, chemicals and microorganisms. In water, especially drinking water, it is desirable to remove the harmful contaminants before consuming them for maintenance of good health.
Several different methods are known for purification of water based on which many devices and apparatus have been designed and are also commercially available. These methods and devices vary depending on the type of impurities present in water. Particulate matter generally larger than 3 microns is filtered out using either a cloth filter or a depth filter, e.g. a bed of activated carbon or clay which has been moulded into a block. Carbon and clay additionally have the advantage of being highly porous materials which also facilitates the removal of soluble impurities by adsorption e.g. dissolved organic compounds, malodorous and bad tasting compounds, pesticides and pesticide residues etc.
It is desirable to also remove or kill the harmful microorganisms like protozoan cysts and bacteria present in potable water. Several methods are employed towards this end. Water may be boiled to kill the microorganisms, but this method is cost-intensive and makes the water have a poor taste. Biocides like chlorine and iodine are sometimes used to kill the microorganisms. These are very effective, but additional precautions have to be provided to ensure that the remaining biocide is removed from the water before it is consumed. Remaining chlorine in water provides a bad odour, while intake of excess chlorine or iodine can be harmful. Ultra-violet radiation is used in many water-purification devices, but ultraviolet radiation requires continuous availability of electric power that is sometimes not available in remote areas. Finally, filters may be used.
US 4,753,728 (Amway, 1988) describes a double shell filter comprising an inner shell of 80 to 400 U.S. mesh screen carbon particles and an outer shell of bonded 20 to 80 mesh screen carbon particles wherein the inner and outer particles are bonded internally to each other and the two shells are bonded together with the help of a specific high molecular polymer binder. This publication teaches the use of a gradation of particle sizes of carbon particles in a composite carbon block, wherein the outer shell functions to filter larger particles and the inner shell functions to filter smaller particles, thereby improving the overall filtration capability of the filter. The carbon block is moulded as a composite and therefore complicated to manufacture. Also, the entire filter will have to be discarded once the flow rate through the filter reduces, which is a costly proposition.
US 5,164,085 (NRG Enterprises, 1992) describes a filter cartridge for water purification consisting of several layers of filter material with successively smaller pore size, with the outer layer being a pre-filtration material with a pore size of approximately 10 microns, a central layer is an extruded carbon filter with a pore size of about 5 microns, preferably with a chemical agent for removal of heavy metals and an inner layer is a ceramic filter with a pore size of about 0.9 microns preferably with impregnated silver for biostatic efficacy. In addition to teaching a gradation of particle sizes to selectively remove particles of different sizes, this publication teaches the use of different materials over the various parts, thereby having the problem of manufacturing complexity.
US 5,328,609 (Magnusson, 1994) describes a manifold mounted liquid filtration system including a disposable filter cartridge having first and second radial flow filtration stages containing filtration media of uniform porosity. A first stage includes a pair of annular concentrically mounted, fibrous sediment and cast carbonaceous filter media and the second stage includes an annular cast carbonaceous filter medium. While the first stage is used to remove suspended sediments, lead and other heavy metals, the second stage removes suspended bacteria and other organic impurities. The filtration system described in this publication requires the entire filter cartridge to be disposed when completely choked and replaced with a new cartridge that would prove cost-extensive.
US 5,151 ,180 (Cuno, 1992) relates to a filter device for use in a residential water supply system which includes a container having an enclosed cavity, and includes a filter unit having a two-stage filter with a first radial flow filter subassembly and a second axial flow filter subassembly. This specific configuration is adapted to minimize the loss in pressure head due to an excessive number of turns usually present in filter devices, thereby providing high flow rates. Although this filter device minimizes frictional losses with the help of a suitable filter configuration, it is not adapted to filter small microorganisms like bacteria and viruses.
US 2003/0213750 (Koslow, 2003) describes a filter medium for enhanced removal of bacteria and virus comprising a microporous structure having a mean flow path of less than or equal to about 1 micron; and a microbiological interception enhancing agent comprising a cationic metal complex capable of imparting positive charge on at least a portion of the microporous structure. The process to make these filters is cost-extensive, complex and requires a high degree of quality control in manufacture which would be difficult to implement in simple household gravity fed water filter systems. JP11104623 (Tokyo Yogyo, 1999) describes an activated carbon block filter water purifier. It comprises an outer cylinder block filter, composed of crushed granular carbon with a low capacity for adsorption but long durability, and an inner cylinder block filter of pitch type fibrous activated carbon with a high capacity for adsorption but low durability. The inner block, which exhausts faster, is replaced more often than the outer block, thereby maintaining enhanced adsorption of the impurities. This publication describes the use of two carbon blocks of different compositions for trapping/ adsorbing different types of impurities. Importantly it does not teach filtration of water to remove microorganisms like cysts.
Thus, there exists a need to have a simple, easy-to-manufacture, cost effective gravity-fed water filter that can be used over a long period of time while providing consistently high flow rates and also ensuring the removal of harmful microorganisms like cysts.
Summary of the invention
A novel filter assembly has now been developed, comprising a series of detachably connectable filter blocks which is capable of not only filtering particulate matter like dust but also the harmful microorganisms. It is configured to maximize filtration efficiency and throughput of the liquid while minimizing the amount of filter medium being consumed to achieve these ends.
It is thus the basic object of the present invention to provide a filtration unit which would provide for the desired particulate removal including microorganisms like cysts, even chlorine resistant cysts such as Cryptosporidium parvum and Giardia Lamblia which are in the size range of 3 to 6 μm.
Yet another object is to provide a gravity fed filtration system which is simple to manufacture and cost effective. It is a further object of the invention to provide a method of filtering liquids which maintains a high flow rate.
Detailed description of the invention
According to one aspect the invention provides a filter assembly for filtration of liquids comprising a series of at least two detachably connectable filter blocks having substantially identical composition.
According to another aspect the invention provides a combined filter for filtration of liquids comprising: a) a washable or replaceable sediment filter for removing particulates generally above 3 microns and, b) said filter assembly, such that the liquid to be filtered passes through said washable or replaceable sediment filter before passing through said filter assembly.
According to yet another aspect the present invention provides a method of filtering liquids comprising:
(a) passing the input liquid through said filter assembly and,
(b) removing the first filter block from the filter assembly and attaching a new filter block to the filter assembly whenever there is substantial reduction in the flow rate of the output liquid.
According to a further aspect of the invention there is provided a water purification device comprising a top chamber for holding the unpurified water and a bottom chamber for receiving the filtered water and a filter assembly or a combined filter as described above wherein the top chamber the filter assembly or the combined filter and the bottom chamber are arranged such that the water passes from the top chamber through the filters to the bottom chamber.
The number of detachably connected filters in series could be any number with a minimum of 2. The maximum is preferably up to 20, more preferably 2 to 8 filter blocks. The filter blocks may be made of any material, preferably carbon, ceramic, clay, polyester or polypropylene, more preferably carbon. When carbon is the material used to make the filter block, it is preferred to use activated carbon, more preferred powder activated carbon.
The filter blocks for use in the filter assembly of the invention preferably comprise powder activated carbon (PAC) and are preferably made into a block with a binder material which binds the powder into a block under the application of heat. Suitable binder materials preferably have a Melt Flow Rate (MFR) of less than five, preferably less than one. The melt-flow rate (MFR) is measured using ASTM D 1238 (ISO 1133) test. The test measures the flow of a molten polymer through an extrusion plastometer under specific temperature and load conditions. The extrusion plastometer consists of a vertical cylinder with a small die of 2 mm at the bottom and a removable piston at the top. A charge of material is placed in the cylinder and preheated for several minutes. The piston is placed on top of the molten polymer and its weight forces the polymer through the die and on to a collecting plate. The time interval for the test ranges from 15 seconds to 6 minutes in order to accommodate the different viscosities of plastics. Temperatures used are 220, 250 and 300 0C (428, 482 and 5720F). Loads used are 1.2, 5 and 10 kg. The amount of polymer collected after a specific interval is weighed and normalized to the number of grams that would have been extruded in 10 minutes: melt flow rate is expressed in grams per reference time.
The binder material is preferably a thermoplastic polymer having a MFR value above described. Suitable examples include ultra high molecular weight polymers, preferably polyethylene or polypropylene. The molecular weight is preferably in the range of 106 to 109 D. Binders of this class are commercially available under the trade names HOSTALEN™ from Tycona GMBH, GUR, Sunfine™ (from Asahi, Japan), Hizex™ (from Mitsubishi) and from Brasken Corp (Brazil). Other suitable binders include LDPE sold as Lupolen™ (from Basel Polyolefins) and LLDPE from Qunos (Australia). The bulk density of the binder material is preferably less than or equal to (≤) 0.6 g/cm3, more < 0.5 g.cm3, and further more preferably ≤ 0.25 g/cm3. The binder material preferably has a particle size distribution substantially the same as that of the PAC but the amount of particles passing 200 mesh is preferably less than 40 wt%, more preferably less than 30 wt%.
The carbon block preferably comprises powder activated carbon (PAC) having a particle size such that 95 wt % of the particles pass through 50 mesh and not more than 13%, preferably not more than 12%, more preferably not more than 10%, passes through 200 mesh. The PAC starting material is preferably selected from bituminous coal, coconut shell, wood, or petroleum tar. The surface area of the PAC is preferably selected such that it exceeds 500 m2/g, more preferably exceeds 1000 m2/g.
Preferably, the PAC has a size uniformity co-efficient of less than 2, or more preferably less than 1.5, a carbon tetrachloride number exceeding 50%, more preferably exceeding 60%. The PAC preferably has an Iodine number greater than 800, more preferably greater than 1000.
The filter medium preferably has a particle size distribution profile across its height. It is preferred that the PAC particles are distributed across the height of the carbon block such that 55 to 80 wt %, preferably 55 to 70 wt% of the PAC particles in the particle size range of 100 to 200 mesh are present in the lower 50 volume% of the carbon block. Also, preferably 55 to 95 %, more preferably 60 to 95 % of the PAC particles in the particle size range smaller than 200 mesh are present in the lower 50 vol% of the carbon block.
The weight ratio of binder material to PAC is preferably between 1:1 and 1 :10, more preferably between 1 : 2 and 1 :6.
By way of the above filtration media of the invention it is possible to attain an average flow rate of water, from a starting height (water level) of 200 mm down to 50 mm, under gravity of 100-300 ml/min., preferably 120-200 ml/min., without compromising on the requirements of removal of particulate including microorganisms, and chemical contaminants.
The carbon block filter can be of any desired shape and size, depending on the end application and the construction in which the filter block is fitted. Suitable shapes include flat circular disc of low thickness, square disc of low thickness, low height tapered flat disc, cylinder, solid cone, hollow cone.
A suitable process of preparation of carbon block filters for use in the filter assembly of the invention has been disclosed in our co-pending application 320/MUM/2004.
A desirable construction of the filter assembly is such that each carbon block filter is fixedly housed in a collar/bracket, said collar/bracket capable of being detachably connectable to each other with screw-threaded joints or snap-fit joints.
The invention is especially suitable for gravity filtration of water that is contaminated with particles including dust and harmful microorganisms e.g. protozoan cyst like Cryptosporidium and Giardia. The filter blocks can be adapted to remove three log removal of cyst. Log removal is defined as the logio (logarithmic to the base 10) of the number of particles fed to the filter divided by the number of particles exiting the filter.
As outlined above, the combined filters according to the invention comprise a washable or replaceable sediment filter and a filter assembly according to the invention.
The sediment filter is preferably a woven or non-woven fabric, more preferably a non-woven fabric having micropores. This sediment filter ensures filtration of particles generally above 3 microns. The sediment filter can be washed and rinsed under flowing tap water or by using a small amount (0.1-10 g/L) of fabric wash detergent in water. The sediment filter prevents premature clogging of the upper filter block in the filter assembly of the invention. Over time the reduction in flow rate of the liquid through the filter assembly is principally due to choking of the pores in the first filter block. On replacement of the first filter block in the assembly with a new filter block a high flow rate of the liquid through the filter is restored without the need to replace the whole filter assembly.
Thus, the method of filtering liquid according to the invention simply comprises the steps of passing the input liquid through the filter assembly and removing the first filter block from the assembly and attaching a new filter block to the assembly whenever there is substantial reduction in the output flow rate. This may be done by replacing the first filter block of the assembly with a new filter block. Alternatively, the first filter block may be removed and a new filter block be attached to the bottom of the remaining assembly, thus effectively making what previously was the second filter block now become the first filter block.
In a preferred embodiment the first filter block is replaced with a new filter block since according to this method filter assembly need only be detached from the top chamber of the water purification device and the remainder of the assembly may be left attached to the bottom chamber.
Description of the drawings
The details of the invention, its objects and advantages are explained hereunder in greater detail by way of the following non-limiting exemplary embodiments of the invention as outlined in the drawings.
Fig. 1 is a schematic of a filter assembly with the various carbon block filters assembled. In Fig.1 , the filter assembly (FA) comprises a series of four carbon block filters (F1 , F2, F3, and F4) each having substantially identical composition and detachably connected to each other. The carbon block filters are fixedly housed in brackets (B1 , B2, B3, B4) which are provided with threaded joints (T) such that said brackets are detachably connectable to each other. The view of Fig. 2 shows the filter assembly disassembled such that the carbon block filter F1 is detached from the filter assembly.
When in use, the filter assembly (FA) of the invention is attached to the bottom of a reservoir of contaminated water (WT). The water flows in the direction indicated by the arrow (IN) and is filtered after passing through a series of carbon block filters of the filter assembly to exit the filter assembly in the direction marked by the arrow (O). After a large amount of water has been filtered and there is substantial reduction in the flow rate of the water, the filter assembly is disassembled, as shown in Fig.2. The filter block (F1) that accounts for the maximum amount of choking is removed and a new filter block attached, either in place of F1 or below F4. Very high flow rates are thereafter obtained. The filter assembly of the invention comprising the detachably connectable carbon block filters in series thus necessitates replacement of only a part of the filter assembly for continuously obtaining high flow rates, as opposed to filters of the prior art where the entire filter would have to be replaced, thereby enabling high cost-effectiveness.

Claims

Claims:
A filter assembly for filtration of liquids comprising a series of at least two detachably connectable filter blocks comprising substantially identical composition, wherein: a) the filter blocks are fixedly housed in a collar or bracket; b) said collars or brackets are detachably connectable with each other; and c) the individual filter blocks are discs, annular cylinders or hollow domes.
A filter assembly as claimed in any one of the preceding claims wherein the liquid is filtered under gravity.
A filter assembly as claimed in any one of the preceding claims comprising 2 to 20 filter blocks.
A filter assembly as claimed in any one of the preceding claims wherein the filter blocks comprise powder activated carbon (PAC) having a particle size such that 95 wt% of the particles pass through 50 mesh and not more than 13% passes through 200 mesh.
A filter assembly as claimed in claim 4 wherein PAC is bond using a binder material binder material having a Melt Flow Rate (MFR) of less than i. A filter assembly as claimed in claim 5 wherein the binder material is high molecular weight polyethylene or polypropylene having a molecular weight of 106 to 109 D.
A combined filter for filtration of liquids comprising: a) a washable or replaceable sediment filter for removing particulates generally above 3 microns and, b) a filter assembly according to any one of the preceding claims, such that the liquid to be filtered passes through said washable or replaceable sediment filter before passing through said filter assembly.
A filter as claimed in claim 7 wherein the sediment filter is a non-woven fabric having micropores.
A method of filtering liquids comprising: a) passing the input liquid through a filter assembly according to any one of claims 1-6 and, b) removing the first filter block from the filter assembly and attaching a new filter block to the filter assembly whenever there is substantial reduction in the flow rate of the output liquid.
A method of filtering water and achieving a three log removal of cysts from said water comprising the step of: a) passing the input liquid through a filter assembly according to any one of claims 1-6.
PCT/EP2006/006406 2005-07-06 2006-06-28 A filter assembly and a method of filtering liquids WO2007003383A1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
IN800/MUM/2005 2005-07-06
IN800MU2005 2005-07-06
EP05077092 2005-09-14
EP05077092.4 2005-09-14

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CN108439526A (en) * 2018-04-25 2018-08-24 郑州嘉晨化工科技有限公司 A kind of wastewater from chemical industry chlorine residue emission reduction device
KR102177733B1 (en) * 2019-11-11 2020-11-11 (주)동아엔지니어링 Apparatus for water treatment using multistage carbon filter

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US20130105385A1 (en) * 2011-10-26 2013-05-02 Altwelltech Inc. Carbon block filter formed from divided particles of binder and activated carbon and method therefor
CN102671440A (en) * 2012-05-14 2012-09-19 宜兴市诺唯环保设备有限公司 Square-module-type fiber fixed-disc filtering machine
CN102671440B (en) * 2012-05-14 2014-06-11 宜兴市诺唯环保设备有限公司 Square-module-type fiber fixed-disc filtering machine
JP2014124564A (en) * 2012-12-26 2014-07-07 Nishimatsu Constr Co Ltd Filtration unit, and turbid water treatment device
CN103100252A (en) * 2013-01-24 2013-05-15 潘征峰 Double-stage or multi-stage filter realizing automatic slag removal
CN103193334B (en) * 2013-04-08 2014-11-05 岑冠颖 Powerful filtering water purifying cylinder
CN103193334A (en) * 2013-04-08 2013-07-10 岑冠颖 Powerful filtering water purifying cylinder
WO2014167152A1 (en) * 2013-04-10 2014-10-16 Empresa Municipal De Aguas Y Saneamiento De Murcia, S.A. Open filtration device for a water treatment station
US10183241B2 (en) 2013-04-10 2019-01-22 Empresa Municipal De Aguas Y Saneamiento De Murcia, S.A. Open filtration device for a water treatment station
CN105251258A (en) * 2015-11-20 2016-01-20 天津美士邦涂料化工有限公司 Coating filter
CN108439526A (en) * 2018-04-25 2018-08-24 郑州嘉晨化工科技有限公司 A kind of wastewater from chemical industry chlorine residue emission reduction device
CN108439526B (en) * 2018-04-25 2020-02-18 中原工学院 Chemical wastewater residual chlorine emission reduction device
KR102177733B1 (en) * 2019-11-11 2020-11-11 (주)동아엔지니어링 Apparatus for water treatment using multistage carbon filter

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