JP2008296103A - Water purifier and water purification method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend the life of a membrane cartridge by inhibiting biofouling during membrane treatment with a reverse osmosis membrane or a nanofiltration membrane and preventing deterioration of a membrane functioning layer due to residual chlorine in tap water, realize long life, power saving, and high safety, and prevent contamination in a water storage tank storing membrane filtrate for a long period of time in a water purifier where water is treated with activated carbon and then filtered with a reverse osmosis membrane or a nanofiltration membrane, and the membrane filtrate is stored in the water storage tank. <P>SOLUTION: The water purifier comprises a pretreatment cartridge having an activated carbon treatment part 2b filtering water with silver-impregnated activated carbon, a membrane filter cartridge 4 filtering the water treated by the pretreatment cartridge with a reverse osmosis membrane or a nanofiltration membrane, and the water storage tank 5 storing the water filtered with the membrane filter cartridge, wherein a sterilization unit 6 incorporating an ultraviolet light-emitting diode and a photocatalytic filter is arranged between the membrane filter cartridge and the water storage tank, and a pump 7 and a reflux duct 14 for refluxing the membrane filtrate in the water storage tank into the sterilization unit 6 are installed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water purifier and a water purification method for treating activated carbon, treating with a reverse osmosis membrane or a nanofiltration membrane, and storing the obtained membrane filtrate in a tank. More specifically, the present invention relates to a water purifier and a water purifying method effective for preventing contamination of membrane filtration water in a water storage tank for a long period of time.

  In recent years, due to deterioration of water source water quality due to environmental pollution, various impurities have remained in tap water treated at a water supply station, causing off-flavor damage such as odor and mold odor. In particular, trihalomethane, which is a carcinogenic substance generated due to chlorine, is a problem even with a small amount of residue, and there are methods and equipment for purifying tap water before use in order to obtain safe and delicious drinking water and cooking water. It has been improved.

  For example, as one of the methods for purifying tap water, after filtration with activated carbon, filtration is performed using a reverse osmosis membrane (hereinafter referred to as “RO membrane”) or a nanofiltration membrane (hereinafter referred to as “NF membrane”). There is a way.

  Since RO membranes and NF membranes can remove many impurities such as organic substances, inorganic ions, bacteria, and viruses in water, it is possible to obtain fresh water with almost no impurities remaining. However, since these membranes have a lower amount of membrane filtration water per unit pressure per unit membrane area than microfiltration membranes and ultrafiltration membranes, many membrane areas and booster pumps are required to increase the amount of membrane filtration water. is required. Therefore, in a relatively small membrane filtration device in which it is difficult to increase the membrane area, the membrane filtration treatment is continued even when the membrane filtration treated water is not used, and the membrane filtration treated water is stored in a water storage tank. A method of using treated water in a water storage tank is used.

  However, since the chlorine in the tap water does not remain in the membrane filtered water that has been membrane filtered and stored in the water storage tank, the membrane filtered water in the water tank is likely to be contaminated by germs and the like.

  Therefore, it is recommended that the water storage tank be cleaned regularly and the purified water staying in the water storage tank for a certain period be discarded. However, it is difficult to fully implement these in reality, and the effect is unknown and has not yet led to a fundamental solution.

  As a means for solving the problem of contamination of membrane filtration water in the water storage tank, there is a method in which a silver zeolite cartridge is immersed in the water storage tank (see Patent Document 1). However, in this method, since the water temperature, electrical conductivity, and amount used of the membrane filtrate in the water storage tank are different in each household, it is necessary to replace the silver zeolite cartridge before the silver ion concentration becomes less than 10 μg / l. There is a problem that it is difficult for each to judge, and it is difficult to sufficiently prevent bacterial contamination of membrane filtration water in the water storage tank. If the silver zeolite cartridge is frequently replaced before the silver ion concentration is less than 10 μg / l, the cost becomes high.

  In addition, as a means for solving the problem of contamination of membrane filtration water in the water storage tank, a method of storing after sterilization with a photocatalyst device that irradiates titanium dioxide with ultraviolet rays to cause catalytic action is applied (see Patent Document 2). It is possible to do. When the photocatalyst is irradiated with light having a certain energy or more, electrons are excited to the conductor from the valence band where electrons are clogged. Holes with high oxidizing power are formed in the valence band after the electrons have escaped, and these holes oxidize hydroxyl groups in water to form OH radicals (hydroxyl radicals). OH radicals have higher oxidizing power than oxygen, chlorine, ozone, hydrogen peroxide, permanganic acid, etc., and can destroy and decompose bacteria such as DNA and cell walls.

  In this case, the membrane filtrate is temporarily sterilized, but the sterilization effect is not sustained in the water storage tank. If the water storage tank is not completely sealed, the problem that bacteria will grow over time can be solved if the water in the water storage tank is not used for a long time and the water in the water storage tank is not replaced. Have difficulty.

  In order to solve such a problem, it is conceivable to apply a method (see Patent Document 3) in which a water purification tank and a UV lamp are provided in the water storage tank to sterilize the water in the water storage tank.

  However, in this case, membrane filtration water flowing out of the storage tank can be sterilized, but the entire membrane filtration water in the storage tank is not sterilized, so the membrane filtration water in the storage tank is not used for a long time. Moreover, if the state in which the water in the water storage tank is not replaced is continued, there is a problem that water accumulates on the inner wall of the tank over time, black mold and the like propagate, and turbidity and a strange odor are emitted.

  In order to solve such a problem, a method of immersing and installing an ultraviolet lamp in the water storage tank can be considered. When the bacteria are irradiated with ultraviolet rays having a wavelength of around 260 nm, they act on the DNA in the bacterial cells to form thymine dimers and cause inactivation of the bacteria.

  However, in this case, since many ultraviolet lamps use highly toxic mercury, when the lamp is damaged, mercury is mixed into the membrane filtrate and is very dangerous. Further, since ultraviolet rays having a wavelength of around 260 nm are absorbed by ordinary glass, quartz glass that is more expensive than ordinary glass must be used as the material of the protective tube for protecting the ultraviolet lamp. Further, the inside of the water storage tank must be made of a durable material such as stainless steel so as not to be deteriorated by ultraviolet rays, which is expensive.

JP 2006-281023 A JP 2002-18429 A JP 2004-125360 A

  The present invention solves the above-mentioned problems in the prior art, suppresses biofouling during membrane treatment with RO membranes and NF membranes, and prevents deterioration of the membrane functional layer due to residual chlorine in tap water. Water purifier and water purifier that can extend the life of membrane cartridges, and can prevent contamination of germs in the water storage tank that stores membrane filtered water for a long period of time with high life, power saving and high safety It is intended to provide a method.

  In order to achieve the above object, the present invention adopts the following configuration.

  That is, a pretreatment cartridge having an activated carbon treatment section for filtering water with silver-impregnated activated carbon, a membrane filtration cartridge for membrane-filtering water treated with the pretreatment cartridge with a reverse osmosis membrane or a nanofiltration membrane, and the membrane filtration A water purifier having a water storage tank for storing water membrane-filtered by a cartridge, and disposing a sterilization unit containing an ultraviolet light emitting diode and a photocatalytic filter between the membrane filtration cartridge and the water storage tank, It is a water purifier provided with a pump and a reflux line for refluxing the membrane filtrate in the water storage tank to the sterilization unit.

  At this time, in order to constantly control the membrane filtrate in the storage tank with bacteria, a branch valve is provided in the reflux line for returning the membrane filtrate in the storage tank to the sterilization unit. It is preferable to provide a pipeline. Moreover, it is preferable that the peak wavelength of the light source of the ultraviolet light-emitting diode is 390 nm or less so that the photocatalyst is in an excited state and has a strong oxidizing power on the surface.

  Further, the water purification method of the present invention is characterized in that tap water supplied at tap water pressure or at a pressure increased by a pump is passed through a pretreatment cartridge loaded with silver-impregnated activated carbon and subjected to activated carbon filtration, and then reverse osmosis membrane Alternatively, a water purification method in which a membrane filtration cartridge having a nanofiltration membrane is passed through a membrane filtration treatment and then sterilized by passing through a sterilization unit containing an ultraviolet light emitting diode and a photocatalyst filter, and stored in a water storage tank. The membrane filtration water inside is intermittently or continuously passed through the sterilization unit again and returned to the storage tank.

  The present invention prevents the functional layer from being deteriorated due to biofouling of RO membrane or NF membrane and residual chlorine by extending the life of the membrane cartridge by performing the pretreatment with the pretreatment cartridge having silver-impregnated activated carbon. can do. Furthermore, when the membrane filtrate filtered through the RO membrane or NF membrane is transferred to the storage tank, the membrane filtration water in the storage tank is passed to the sterilization unit by passing it through a sterilization unit containing an ultraviolet light emitting diode and a photocatalytic filter. By letting it pass through, it has a longer life, power saving and higher safety than the prior art, and can prevent contamination of germs in the water storage tank over a long period of time.

  That is, according to the present invention, in the water purifier or the water purification method for storing the membrane filtration treated water in the water storage tank after the tap water is treated with activated carbon and then membrane filtered with a membrane cartridge having an RO membrane or NF membrane, Biofouling at the time of membrane treatment with NF membrane or NF membrane can be suppressed, deterioration of the functional layer due to residual chlorine can be prevented, and the life of the membrane filtration cartridge can be extended. Furthermore, high life, power saving, and high safety can be prevented over a long period of contamination of germs in the water storage tank that stores membrane filtrate.

  Hereinafter, the present invention will be described in more detail based on embodiments shown in the drawings. In addition, this invention is not limited to the following embodiments.

  Drawing 1 is an outline flow figure showing one embodiment of a water treatment process performed in a water purifier concerning the present invention.

  The water purifier of the present invention is used by being directly connected to a water pipe, for example, as shown in FIG. In FIG. 1, along tap water passing route, tap water supply valve 1, filter filtration unit 2 a for removing turbidity such as iron rust in tap water, and residual chlorine in tap water are removed into tap water. A pretreatment cartridge 2 which is arranged in series and integrated with a silver impregnated activated carbon filtration unit 2b for eluting silver, upstream of the membrane cartridge 4 to ensure a predetermined amount of membrane filtration water even when the tap water pressure is too low There are provided a booster pump 3 disposed on the side, a membrane filtration cartridge 4 having an RO membrane or NF membrane for membrane filtration of water treated by the pretreatment cartridge 2, and a water storage tank 5 for storing the membrane filtration water. Further, a sterilization unit 6 including an ultraviolet light emitting diode and a photocatalytic filter for sterilizing the membrane filtrate in the water storage tank 5 is provided, and the membrane filtrate in the water storage tank 5 is passed through the sterilization unit 6 by reflux. A water supply pump 7 for discharging to the outside is provided, and a reflux line 14 for supplying the membrane filtered water in the water storage tank 5 to the sterilization unit 6 by the water pump 7 is provided to the reflux circuit. A switchable branch valve (three-way valve) 8 is provided. Further, a concentrated water valve 9 for controlling the amount of concentrated water from the membrane filtration cartridge 4 to a predetermined level in order to control the water recovery rate is provided in the concentrated water discharge path. A water level sensor 10 for controlling the water level is provided. And the tap water supply valve 1 for supplying tap water to the water purifier is opened and closed by the signal from the water level sensor 10.

  Here, as the pretreatment cartridge 2 in which the filter filtration unit 2a and the silver impregnated activated carbon filtration unit 2b are integrally configured, for example, as shown in FIG. A 10 μm cylindrical filter is arranged, and an activated carbon filtration unit 2b in which a silver impregnated activated carbon is filled in a cylindrical container is arranged at the lower part (downstream side) of the cartridge. Here, the water filtered from the outside to the inside of the cylindrical filter has a structure that passes through the layer 2b of the silver-impregnated activated carbon, but the passing order of the filter and the silver-impregnated activated carbon may be reversed. .

  The filter layer used is not particularly limited as long as the average pore size is 0.1 to 10 μm, and may be any of a pleated type, a wind type, a depth type, etc., and the material is not particularly limited. However, any of polypropylene, polyester and the like may be used.

  The silver-impregnated activated carbon to be used is not particularly limited as long as the silver ion concentration in the water after passing through the layer 2b of the silver-impregnated activated carbon can be 5 μg / L or more and the chlorine concentration can be 0.1 mg / L or less. For example, silver impregnated activated carbon obtained by dissolving silver nitrate and magnesium nitrate in distilled water, spraying it uniformly on the activated carbon, and drying the resultant is mentioned. Further, the shape of the silver-impregnated activated carbon may be any of powder, granule, fiber, etc., but the water inflow portion and the water outflow portion are mesh structure so that the silver-impregnated activated carbon does not leak out of the pretreatment cartridge 2. It is preferable to cover with a nonwoven fabric filter or the like. The raw material of the activated carbon forming the silver-impregnated activated carbon may be coconut shell, wood, coal, petroleum coke or the like.

  The separation membrane used in the membrane cartridge 4 having the RO membrane or NF membrane used in the present invention has a desalination rate of 93% or more (evaluation conditions NaCl concentration: 500 mg / L, operating pressure: 0.1 MPa). Alternatively, an NF membrane having a desalination rate of 5% or more and less than 93% (evaluation conditions NaCl concentration: 500 mg / L, operating pressure: 0.1 MPa) can be selected and used.

  As the material of the separation membrane having such performance, in the case of RO membrane, polymer materials such as cellulose acetate, cellulose-based polymer, polyamide, and vinyl polymer can be used. In the case of NF membrane, polyamide-based, polypiperazine An amide type, a polyester amide type, or a crosslinked water-soluble vinyl polymer can be used. Typical RO membranes include cellulose acetate-based or polyamide-based asymmetric membranes and composite membranes having a polyamide-based active layer. Among them, polyvinyl alcohol is used as the surface layer of the polyamide-based active layer. The coated composite membrane is preferable because it has high exclusion performance, high water permeability, and high stain resistance.

  As the shape of the separation membrane, both the RO membrane and the NF membrane are preferably flat membranes or hollow fiber membranes. For example, the separation membrane has a thickness of 10 μm to 1 mm, and in the case of a hollow fiber membrane, the outer diameter is 50 μm to 4 mm. It is preferable to be in the range.

  The RO membrane filtration cartridge or NF membrane filtration cartridge 4 has a disk type in which spiral, pleated, plate-and-frame, and disk-shaped discs are stacked when the separation membrane is a flat membrane. In the case of a membrane, there is a cylindrical shape in which hollow fiber membranes are bundled in a U shape or an I shape and stored in a container, but any cartridge shape may be used in the present invention. These membrane filtration cartridges 4 are preferably operable at a low pressure from the viewpoint of reducing running costs.

  In the sterilization unit 6 used in the present invention, for example, as shown in FIG. 3, ultraviolet light having a peak wavelength of 390 nm or less emitted from the ultraviolet light-emitting diode 13 passes through the light-transmitting plastic plate 12 and then can be irradiated on the surface of the photocatalytic filter 11. An ultraviolet light-emitting diode 13 is disposed on the inflow side so as to face the photocatalytic filter 11. The ultraviolet light emitting diode 13 is preferably covered with a light-transmitting plastic plate 12 and waterproofed so as not to come into contact with the membrane-filtered water. The light transmissive plastic plate 12 may be replaced with a glass plate.

  The photocatalyst material of the photocatalyst filter 11 includes metal oxide particles made of titanium dioxide, tin dioxide, zinc oxide, tungsten trioxide and the like, and metal sulfide particles made of cadmium sulfide, zinc sulfide, etc., but are relatively inexpensive. Therefore, it is preferable to use titanium dioxide particles which are not harmful to human bodies. Titanium oxide, which is a typical photocatalyst, is classified into three types, anatase type, rutile type, and brookite type, depending on the crystal structure. The anatase type band cap energy is 3.2 eV, and it reacts by absorbing a wavelength shorter than 388 nm, that is, ultraviolet rays. The rutile type band cap energy is 3.06 eV, and it reacts by absorbing from a wavelength shorter than 410 nm, that is, blue visible light. The Brookite type is a metastable phase.

  The material of the photocatalytic filter 11 is a porous ceramic with a three-dimensional network structure that is insoluble in water, does not deteriorate over time due to ultraviolet rays such as resin, has a large surface area, high contact efficiency with water, and low pressure loss. Is preferred. A filter made of this material is coated with, for example, titanium dioxide coated with apatite to obtain a photocatalytic filter. Bacteria in the membrane filtered water are adsorbed and captured by the apatite when the membrane filtered water passes through the photocatalytic filter 11, and are destroyed and decomposed by OH radicals generated from the titanium dioxide surface that is excited by ultraviolet irradiation in the vicinity of the apatite. .

  Since the tap water pressure is usually different in each household and fluctuates, a concentrated water valve 9 for controlling the amount of concentrated water discharged from the membrane filtration cartridge to a predetermined level is arranged in the concentrated water discharge path. . In order to control the water recovery rate to a constant level even if the tap water pressure varies or fluctuates, the amount of membrane filtration water in the membrane cartridge 4 is proportional to the tap water pressure, and is thus discharged from the concentrated water valve 9. It is preferable to use one whose concentrated water amount varies in proportion to the tap water pressure. For example, when it is desired to set the predetermined water recovery rate to 40%, the amount of concentrated water varies depending on the tap water pressure so that (water filtration treatment water amount) :( concentrated water amount) = 40: 60 at any tap water pressure It is preferable to select a concentrated water valve 9 that can be made to operate. If the amount of concentrated water controlled and discharged by the concentrated water valve 9 is constant regardless of fluctuations in the tap water pressure, when the tap water pressure is low, the water recovery rate decreases, and tap water is wasted. On the contrary, when the tap water pressure is high, the water recovery rate is increased, and there arises a problem that the scale of silica or calcium is easily deposited.

  What is necessary is just to set a water recovery rate suitably according to the tap water quality of each area so that a scale of silica, calcium, etc. may not precipitate. The concentrated water valve 9 is not particularly limited as long as it has a structure capable of controlling the amount of water passing therethrough, and an ordinary throttle valve may be used.

  In the water purifier of the present invention described above, the water purification treatment is performed as follows.

  First, when it is detected that the water level sensor 10 in the water storage tank 5 has become the predetermined lower limit water level L or less, a signal is sent, the tap water supply valve 1 is automatically opened, and the tap water is filtered. The part 2a and the silver impregnated activated carbon filtration part 2b are supplied to a pretreatment cartridge 2 in which they are integrally arranged. By passing the tap water through the filter filtration unit 2a, turbidity such as iron rust in the tap water is removed, and by passing through the silver impregnated activated carbon filtration unit 2b, residual chlorine in the tap water is removed, Silver elutes.

  Next, the water treated by the pretreatment cartridge 2 is supplied to the RO membrane filtration cartridge or the NF membrane filtration cartridge 4. Since the residual chlorine of tap water is removed, the functional layer of the RO membrane or the NF membrane is prevented from being deteriorated over time, and the quality of the membrane filtration treated water is prevented from being deteriorated over time. Further, since silver is eluted at 5 μg / L or more, the growth of miscellaneous bacteria such as general bacteria is suppressed, and the occurrence of biofouling is suppressed. However, since silver ions in water are almost removed by filtration through the RO membrane or NF membrane, almost no silver ions remain in the water filtered through the RO membrane or NF membrane.

  Therefore, the membrane filtrate filtered through the RO membrane or NF membrane flows into the sterilization unit 6. The sterilization unit 6 includes an ultraviolet light emitting diode 13 and a photocatalyst filter 11. When the membrane filtrate passes through the photocatalyst filter 11, bacteria in the membrane filtrate are captured on the surface of the photocatalyst filter 11 and are excited by irradiation with ultraviolet rays. It is destroyed and decomposed by OH radicals generated from the titanium dioxide surface.

  Membrane filtrate that has flowed out of the sterilization unit 6 is temporarily stored in the water storage tank 5, but periodically passes through the sterilization unit 6 again via the water pump 7 and returns to the water storage tank to suppress bacterial growth. To do. The reflux time and the reflux frequency are not particularly limited, but are appropriately set according to the capacity of the water storage tank, the discharge amount of the pump 7, the water temperature of the membrane filtration water, the water quality, and the like.

  Membrane filtrate that has been sterilized by periodically passing through the sterilization unit 6 can be taken in by switching the three-way valve 8 from the sterilization unit 6 side to the discharge side via the pump 7.

  On the other hand, water that has not been membrane-filtered by the RO membrane or NF membrane is discharged out of the system as concentrated water through the concentrated water valve 9.

  When the tap water supply valve 1 is opened and the water purification process is continued, the water level of the water storage tank 5 gradually rises, and when it is detected that the water level sensor 10 in the water storage tank 5 has reached the predetermined upper limit water level H, A signal is sent, the tap water supply valve 1 is automatically closed, and the supply of tap water to the cartridge 2 is automatically stopped. When the membrane filtered water is taken and the water level falls below the predetermined lower limit water level L, a signal is sent, the tap water supply valve 1 is automatically opened, and the tap water is automatically supplied to the pretreatment cartridge 2. Return.

  In addition, when the tap water pressure is too low to secure a predetermined amount of membrane filtration water, it is preferable to provide the booster pump 3 in the previous stage of the membrane filtration cartridge 4 to increase the pressure before the membrane filtration cartridge. At this time, the booster pump 3 is interlocked with the tap water supply valve 1, and when the tap water supply valve 1 is opened, the booster pump 3 is operated, and when the tap water supply valve 1 is closed, the booster pump 3 is stopped. It is preferable to do so.

Example 1
Using a water purifier equipped with the water treatment process shown in FIG. 1, tap water having a tap water pressure of 250 kPa, chromaticity of 3 degrees, electrical conductivity of 230 μS / cm, and residual chlorine of 0.8 mg / L is obtained from Monday to Friday. 3 L of water was treated.

The pretreatment cartridge 2 in the water purifier used here is a cartridge having the structure shown in FIG. 2, a wind filter having an average pore diameter of 1 μm is used for the filter 2a, and the silver-impregnated activated carbon 2b is made by Kuraray Chemical. 100 g of silver impregnated granular activated carbon was used. As the membrane in the membrane cartridge 4, 1 m ² of NF membrane (Toray, UTC-60) was used. The pressurizing pump 3 was not used.

  As the sterilization unit 6, a structure shown in FIG. 3 is used, a photocatalytic ceramic filter (diameter 30 mm, thickness 10 mm) is used as the photocatalytic filter 11, and a transparent acrylic plate is used as the light transmissive plastic plate 12. As the ultraviolet light emitting diode 13, 16 diodes having a peak wavelength of 365 nm and an optical output of 2 mW were used. The water storage tank 5 was 3 L in volume and made of an ABS resin tank. The water supply pump 7 was a DC12V electric pump, and the concentrated water valve 9 was a throttle valve.

  The sterilization unit 6 was controlled so that the ultraviolet light emitting diode 13 was energized while the tap water supply valve 1 was open, and the energization was stopped when the tap water supply valve 1 was closed. Further, every 6 hours, the membrane filtrate in the water storage tank 5 was refluxed through the sterilization unit for 30 minutes by the water pump 7, and the ultraviolet light-emitting diode 13 was also energized when passing through this reflux.

  As a result of continuing the water purification treatment for 5 days a week, the general bacteria of the collected membrane filtration water maintained 10 cfu / mL or less for a long period of 6 months from the start of operation.

(Comparative Example 1)
In the control of the sterilization unit 6, the water purification treatment was performed under exactly the same conditions as in Example 1 except that the membrane filtrate in the water storage tank 5 was not returned to the sterilization unit by the pump 7. As a result, the general bacteria of water collected from Tuesday to Friday was as high as 200 to 1,000 cfu / mL, and in particular, the general bacteria of water collected on Monday at the beginning of the week was extremely high as 10,000 cfu / mL or more. .

(Comparative Example 2)
Except that the sterilization unit 6 was not installed, the same water purifier as in Example 1 was used, and water purification treatment was performed under the same conditions as in Example 1. As a result, the general bacteria of water collected from Tuesday to Friday is as high as 1,000 to 5,000 cfu / mL, and in particular, the general bacteria of water sampled on Monday at the beginning of the week is significantly higher than 50,000 cfu / mL. it was high.

  The water purifier and the water purifying method according to the present invention are useful as a small water purifier for improving the water quality and obtaining safe and high-quality water when tap water is used for beverages and cooking.

It is a schematic flowchart which shows one embodiment of the water treatment process performed in the water purifier which concerns on this invention. It is a structure schematic (front sectional drawing) which shows one implementation structure of the pre-processing cartridge integrated in the water purifier which concerns on this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is the structure schematic which shows one implementation structure of the sterilization unit integrated in the water purifier concerning this invention, Comprising: A front cross section and a plane cross section are each shown.

Explanation of symbols

1: Tap water supply valve 2: Pretreatment cartridge 2a: Filter filtration unit 2b: Silver impregnated activated carbon filtration unit 3: Booster pump 4: Membrane filtration cartridge 5: Water storage tank 6: Sterilization unit 7: Water pump 8: Branch valve (three-way) valve)
9: Concentrated water valve 10: Water level sensor 11: Photocatalytic filter 12: Light transmissive plastic plate 13: Ultraviolet light emitting diode 14: Reflux line 15: Discharge line

Claims (4)

A pretreatment cartridge having an activated carbon treatment section for filtering water with silver-impregnated activated carbon, a membrane filtration cartridge for membrane filtration of water treated with the pretreatment cartridge with a reverse osmosis membrane or a nanofiltration membrane, and the membrane filtration cartridge. A water purifier having a water storage tank for storing membrane-filtered water, wherein a sterilization unit containing an ultraviolet light emitting diode and a photocatalytic filter is disposed between the membrane filtration cartridge and the water storage tank, and the water storage A water purifier comprising a pump and a reflux line for refluxing the membrane filtrate in the tank to the sterilization unit. 2. A water purifier according to claim 1, wherein a branch valve is provided in a reflux line for refluxing the membrane filtrate in the water storage tank to the sterilization unit, and an external discharge pipe is provided in the branch valve. . The water purifier according to claim 1 or 2, wherein a peak wavelength of a light source of the ultraviolet light emitting diode is 390 nm or less. Membrane filtration cartridge having a reverse osmosis membrane or a nanofiltration membrane after passing tap water supplied at a tap water pressure or with a water pressure increased by a pump through a pretreatment cartridge loaded with silver-impregnated activated carbon Is passed through a sterilization unit containing an ultraviolet light-emitting diode and a photocatalyst filter, and is sterilized and stored in a water storage tank. The membrane filtration water in the water storage tank is intermittently used. Alternatively, the water purification method is characterized by continuously passing the sterilization unit again and returning to the storage tank.

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