JP2008246376A - Water purifier and water purification method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress biofouling during membrane treatment by a reverse osmosis membrane or a nano filter membrane, to prevent the degradation of a membrane functional layer due to residual chlorine in tap water, to prolong the service life of a membrane cartridge, and to prevent bacteria contamination inside a water storage tank for storing membrane filtered water over a long period of time, in a water purifier for performing activated carbon treatment, then performing membrane filtration treatment by the reverse osmosis membrane or the nano filter membrane and storing the membrane filtered water in the water storage tank. <P>SOLUTION: The water purifier comprises a pretreatment cartridge 2 with an activated carbon treatment part 2b for filtering water by silver attached activated carbon, a membrane filter cartridge 4 for membrane-filtering the water treated in the pretreatment cartridge by the reverse osmosis membrane or the nano filter membrane, and a water storage tank 8 for storing the water membrane-filtered in the membrane filter cartridge. A sterilization unit 7 capable of generating chloride from an electrode to which a voltage is applied and controlling the chlorine concentration of the water inside the water storage tank to 0.1 to 0.4 mg/L is disposed between the membrane filter cartridge and the water storage tank. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water purifier and a water purification method for treating with activated carbon and then treating with a reverse osmosis membrane or a nanofiltration membrane.

  More specifically, by performing pretreatment with a pretreatment cartridge having silver-impregnated activated carbon, biofouling in reverse osmosis membranes and nanofiltration membranes is prevented and membrane functional layer deterioration due to residual chlorine is prevented, Membrane filtration cartridges that extend the life of membrane cartridges that use reverse osmosis membranes and nanofiltration membranes, and then generate voltage with sufficient sterilization effect without applying a voltage to the electrodes to produce a chlorine odor It is related with the water purifier and the water purifying method which are installed in the downstream side of this, and prevent germs contamination in a water storage tank by this sterilization unit.

  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 where it is difficult to increase the membrane area, the membrane filtration treatment is continued even when the membrane filtration treatment water is not consumed, and the membrane filtration treatment water is stored in the water storage tank. A method of using the treated water in the water storage tank for consumption 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 inside of the water tank be cleaned regularly and that the clean water staying in the water tank for a certain period should be discarded. However, it is difficult to actually carry out these operations sufficiently, and the effects are unknown and have not led to a fundamental solution.

  In addition, as a means of sterilizing the inside of the electrolytic cell in order to solve the problem of contamination of bacteria in the electrolytic cell disposed on the downstream side of the water purifier, hypochlorous acid is electrolyzed in the water supply line before the electrolytic cell. There has been proposed a method of disposing an electrolytic sterilizing water generating device for generating water and sterilizing the inside of an electrolytic cell and a water circuit (see Patent Document 1). In the case of this sterilization treatment method, since it is sterilized by generating and holding sufficient hypochlorous acid for the purified water in the electrolytic cell and the water circuit, the purified water when hypochlorous acid was produced is It is not used for consumption of beverages. That is, since hypochlorous acid sufficient for sterilization is generated, there is an unpleasant chlorine odor and the water is not suitable for beverage use. It is necessary to rinse with clean water without chloric acid.

  A method has been proposed in which water subjected to membrane filtration is treated with silver-impregnated activated carbon or silver zeolite and then stored in a water storage tank. However, in the silver-impregnated activated carbon treatment, organic matter that can be a nutrient source for microorganisms is adsorbed and increased on the activated carbon surface where silver is not impregnated with the passage of water passing time. When the water is stagnant, there is a problem that bacteria are likely to grow on the activated carbon surface to which silver is not attached. In addition, in the silver zeolite treatment, the sustained release amount of silver ions is generally small and the life is short, so that it is difficult to impart sufficient silver ion concentration to water only by passing water. Here, in order to increase the amount of silver ions sustainedly released from the silver zeolite, it is sufficient to increase the filling amount of the silver zeolite. However, as the filling amount increases, the cartridge needs to be enlarged. It is difficult to adopt. Another problem is that the cartridge needs to be frequently replaced in order to maintain a predetermined silver ion concentration.

  In order to solve such a problem, a method of immersing and installing silver zeolite in a water storage tank for storing membrane filtration treated water is conceivable. However, in this case, in order to make the silver ion concentration in the water tank uniform, it is necessary to constantly agitate the purified water in the water tank. Further, the purified water in the water tank is not used for a long time and the purified water in the water tank is not used. If the state is not replaced, silver ions continue to elute in the water storage tank, and there is a problem that the silver ion concentration exceeds the specified amount. Furthermore, since the sustained release amount of silver ions varies greatly depending on the quality and temperature of the purified water in the water storage tank, it is necessary to always finely adjust the silver zeolite filling amount in order to maintain a predetermined silver ion concentration.

  Furthermore, when the chlorine ion concentration in purified water is high, silver reacts with the chlorine ion to produce silver chloride and cannot maintain an ionic state effective for antibacterial activity. As described above, the conventional technique in which antibacterial treatment is performed using silver-impregnated activated carbon or silver zeolite is unsatisfactory as a measure against contamination of purified water in the water storage tank.

  In addition, since a polyamide-based resin is generally used as a material constituting the functional layer of the RO membrane or NF membrane, in order to prevent the functional layer from deteriorating with time due to residual chlorine in tap water, Before filtration with a membrane or NF membrane, tap water is pretreated with activated carbon or the like to remove residual chlorine.

  However, when water that has lost residual chlorine and has lost its antibacterial properties is subjected to membrane filtration, microorganisms are likely to grow on the membrane surface, so a slime substance (biofilm) mainly consisting of microorganisms and their metabolites on the membrane surface Adheres, that is, biofouling occurs, and there is a problem that the water permeability of the RO membrane and the NF membrane decreases.

In order to solve such a problem, as disclosed in Patent Document 2, for example, there is a method in which a membrane treatment is performed after the pretreatment is performed with silver-impregnated activated carbon to obtain water containing silver ions. However, in this case, it is possible to suppress biofouling of the RO membrane and NF membrane, but most of the silver ions in the water are removed by the RO membrane and NF membrane, so in the purified water after membrane treatment Silver ions hardly remain and it is difficult to prevent bacterial contamination of the purified water in the storage tank after membrane treatment.
JP-A-6-91268 JP-A 61-54278

  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. An object of the present invention is to provide a water purifier and a water purifying method that can extend the life of the membrane cartridge and can prevent contamination of germs in the water storage tank for storing the membrane-treated water over a long period of time. It is.

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, generating chlorine from an electrode to which voltage is applied, and the chlorine concentration of water in the water storage tank is high in sterilizing ability, Purified water in which a sterilizing unit that has an action of killing bacteria and can be controlled to 0.1 to 0.4 mg / L so as not to feel a chlorine odor is disposed between the membrane filtration cartridge and the water storage tank Container.

  At this time, even when the flow rate of the membrane filtrate varies, in order to control the chlorine concentration to a predetermined concentration, a flow meter for measuring the flow rate of the membrane filtrate is disposed in the membrane filtrate pipe, and the flow meter It is preferable to provide an electric circuit that proportionally controls the current of the electrode of the sterilization unit in accordance with the flow rate of the membrane filtrate measured in (1). Alternatively, a flow meter for measuring the flow rate of the supplied water supplied to the membrane filtration cartridge is arranged in the supply water pipe, and the flow meter for measuring the flow rate of the concentrated water discharged from the membrane filtration cartridge without being subjected to membrane filtration is used as the concentrated water. It is preferable to provide an electric circuit that is disposed in the pipe and proportionally controls the current of the electrode of the sterilization unit according to the membrane filtration flow rate calculated from the difference between the supply water flow rate and the concentrated water flow rate. Alternatively, when a flow meter for measuring the flow rate of the membrane filtrate is disposed in the membrane filtrate pipe, and when a constant voltage is applied to the flow rate of the membrane filtrate measured by the flow meter and the electrode of the sterilization unit It is preferable to provide an electric circuit for controlling the voltage application time and the voltage application pause time of the electrode of the sterilization unit from the current value of the electrode. Alternatively, a flow meter for measuring the flow rate of the supplied water supplied to the membrane filtration cartridge is arranged in the supply water pipe, and the flow meter for measuring the flow rate of the concentrated water discharged from the membrane filtration cartridge without being subjected to membrane filtration is used as the concentrated water. The electrode of the sterilization unit is arranged in a pipe, from the flow rate of membrane filtration water calculated from the difference between the flow rate of the supply water and the flow rate of concentrated water and the current value of the electrode when a constant voltage is applied to the electrode of the sterilization unit. It is preferable to provide an electric circuit for controlling the voltage application time and the voltage application pause time.

  Here, in order to prevent the formation of calcium carbonate on the cathode surface of the sterilization unit, it is preferable to provide an electric circuit that reverses the polarity of the voltage applied to the electrode of the sterilization unit every predetermined time. In addition, when turbidity such as iron rust is mixed in the tap water of the raw water, the membrane filtration process is performed by clogging the flow path on the primary side of the membrane filtration cartridge or thickening the cake layer on the membrane surface. Since the amount of water tends to decrease, it is preferable to dispose a filter unit cartridge having a filter with an average pore diameter of 0.1 to 10 μm on the upstream side of the membrane cartridge.

  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 Or after passing through a membrane filtration cartridge having a nanofiltration membrane and passing through a membrane filtration treatment, it passes through a sterilization unit that generates chlorine from an electrode to which a voltage is applied, and stores it in a water storage tank, which is then stored in the water storage tank The chlorine concentration of water is 0.1 to 0.4 mg / L.

  At this time, it is preferable that the flow rate of the membrane filtration water after the membrane filtration treatment is measured with a flow meter, and the current of the electrode of the sterilization unit is proportionally controlled according to the flow rate of the membrane filtration water. Alternatively, the flow rate of the supply water supplied to the membrane filtration treatment and the flow rate of the concentrated water discharged from the membrane filtration treatment are measured with a flow meter, and the membrane is calculated from the difference between the supply water flow rate and the concentrated water flow rate It is preferable to proportionally control the current of the electrode of the sterilization unit according to the flow rate of the filtrate water. Alternatively, the flow rate of the membrane filtration water is measured with a flow meter, and the voltage application time of the sterilization unit electrode according to the flow rate of the membrane filtration water and the current value of the sterilization unit electrode when a constant voltage is applied It is preferable to control the voltage application pause time. Alternatively, the flow rate of the supply water supplied to the membrane filtration treatment and the flow rate of the concentrated water discharged from the membrane filtration treatment are measured with a flow meter, and the membrane is calculated from the difference between the supply water flow rate and the concentrated water flow rate It is preferable to control the voltage application time and voltage application pause time of the sterilization unit electrode according to the flow rate of filtered water and the current value of the sterilization unit electrode when a constant voltage is applied.

  Moreover, it is preferable to reverse the polarity of the voltage applied to the electrode of the sterilization unit every predetermined time.

  According to the present invention, after treating tap water with silver-impregnated activated carbon and then membrane-filtering with a membrane cartridge having an RO membrane or NF membrane, in a water purifier and a water purification method for storing membrane filtration treated water in a water storage tank, Biofouling during membrane treatment with a membrane or NF membrane can be suppressed, deterioration of the membrane functional layer due to residual chlorine can be prevented, and the life of the membrane filtration cartridge can be extended. Furthermore, contamination with germs in the water storage tank for storing the membrane filtrate can be prevented over a long period of time.

  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 passage route, tap water open / close valve 1, filter filtration unit 2a for removing turbidity such as iron rust in tap water, and residual chlorine in tap water are removed. A pretreatment cartridge 2 which is arranged in series with a silver-impregnated activated carbon filtration unit 2b for eluting silver into water, and a membrane cartridge in order to ensure a predetermined amount of membrane filtration treatment water even when the tap water pressure is too low 4, a pressure pump 3 disposed upstream of the membrane 4, 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 flow rate of membrane filtration treated water of the membrane filtration cartridge 4 A flow meter 6 for measuring the pressure, a sterilization unit 7 for eluting antibacterial metal ions into the membrane filtration treated water, and a water storage tank 8 for storing the membrane filtration treated water after passing through the sterilization unit 7 ,this Faucet 10 for taking out the purified water from the water tank. Further, a water level sensor for controlling the water level of the water storage tank 8 is provided in the concentrated water discharge path, and a concentrated water valve 5 for controlling the amount of concentrated water from the membrane cartridge 4 to a predetermined level in order to control the water recovery rate. 9 is provided. And the supply valve 1 of the raw | natural water (tap water) supplied to a water purifier is opened and closed by the signal from this water level sensor 9. FIG.

  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 2 a is arranged, and an activated carbon filtration part 2 b 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 2a is structured to pass 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. Absent.

  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 7 used in the present invention, for example, as shown in FIG. 4, two plate-like electrodes 11 are arranged facing each other along the flow of the membrane filtration treated water from the inlet to the outlet. Yes. The electrode is composed of an electrode that can withstand both cathode and anode, for example, a platinum electrode or an electrode obtained by plating the surface of titanium with platinum. Chlorine Cl ₂ is generated from the anode side and reacts with water H ₂ O to produce hypochlorous acid (HOCl) having a high sterilizing ability and chlorine ions (Cl ⁻ ) having no sterilizing ability. (Cl ₂ + H ₂ O → HOCl + H ⁺ + Cl ⁻ ). The chlorine concentration in this patent is a value obtained by converting effective chlorine, that is, hypochlorous acid (HOCl), into Cl ₂ concentration without containing chlorine ions (Cl ⁻ ).

  On the other hand, since calcium scale is deposited on the surface of the cathode, in order to prevent this phenomenon, it is preferable to reverse the polarity of the voltage applied to the electrode every predetermined time. It is preferable that the metal composition of both electrodes is the same in order to always stabilize the generation amount. In FIG. 4, the electrodes 11 are fixed by an insulator 13, and electric wires 12 are connected to the electrodes 11. It is preferable to cover the outer periphery of the electric wire 12 and the outer periphery of the joint portion between the electrode 11 and the electric wire 12 with an insulator 13 such as a resin so that no electrical contact is caused by contact with the membrane filtration treated water.

  Since the water pressure of tap water usually varies from one household to another and fluctuates, in order to control the amount of concentrated water coming out of the membrane filtration cartridge to a predetermined level, the concentrated water valve 5 is arranged in the concentrated water discharge path. Is done. In order to control the water recovery rate to a constant level even if the tap water pressure is different or fluctuates, the amount of membrane filtration treated water of the membrane cartridge 4 is proportional to the tap water pressure and is discharged from the concentrated water valve 5. 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 the concentrated water valve 5 that can be made to operate. On the other hand, when the amount of concentrated water controlled and discharged by the concentrated water valve 5 is constant regardless of fluctuations in the tap water pressure, when the tap water pressure is low, the water recovery rate decreases, and the tap water is reduced. When the tap water pressure is high, the water recovery rate increases, and there arises a problem that silica and calcium scales are likely to precipitate.

  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 5 is not particularly limited as long as it has a structure capable of controlling the passing water amount, and a normal throttle valve may be used. The flow meter 6 may be an impeller type, an area type, or the like as long as it can measure the flow rate of membrane filtration treated water.

  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 9 in the water storage tank 8 has fallen below the predetermined lower limit water level, a signal is sent, the raw water supply valve 1 is automatically opened, and the tap water is supplied to the filter filtration unit 2a. And the silver impregnated activated carbon filtration part 2b are supplied to the 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, most of the residual chlorine in the tap water is removed. Silver elutes in water.

  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 most of the residual chlorine is removed, the functional layer of the RO membrane or NF membrane is prevented from deterioration over time, and the water quality of the membrane filtration treated water is prevented from deterioration 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 filtration treated water filtered through the RO membrane or NF membrane flows into the sterilization unit 7. The sterilization unit 7 has a pair of electrodes whose surfaces are platinum or titanium plated with platinum, and a current is applied to the electrodes by applying a voltage to the electrodes while the electrodes are immersed in the membrane filtration treated water. Produces chlorine. Theoretically, according to Faraday's law, the amount of chlorine produced in water increases in proportion to the amount of current.

  As a method for controlling to a predetermined chlorine concentration, the flow rate of the membrane filtrate is measured with the flow meter 6, and the current of the electrode of the sterilization unit 7 is proportionally controlled according to the flow rate output from the flow meter 6. In other words, when the flow rate of membrane filtration water is large, the current is increased, and when the flow rate is small, the current is decreased, so that the flow rate of the membrane filtration amount can be controlled to a predetermined chlorine concentration. Become.

  As another method for controlling the chlorine concentration, the voltage application time and voltage application pause time of the sterilization unit electrode are determined from the flow rate of membrane filtrate and the current value of the electrode when a constant voltage is applied to the electrode of the sterilization unit. To control. That is, the membrane filtrate containing chlorine at the time of voltage application and the membrane filtrate not containing chlorine at the time of voltage application suspension are mixed in a water storage tank to control to a predetermined chlorine concentration. If the flow rate of membrane filtration water is small or the current value (membrane filtration water quality) is high, increase the voltage application pause time. If the flow rate of membrane filtration water is large or the current value (membrane filtration water quality) is low, Reduce the voltage application pause time. The formula for calculating the chlorine concentration is as follows.

  While chlorine is generated at the anode when a voltage is applied, scales of calcium, magnesium, and the like are deposited on the surface of the cathode, so the chlorine generation efficiency gradually decreases. Therefore, it is possible to prevent scale deposition by providing an electric circuit that reverses the polarity of the voltage applied to the electrode every predetermined time and performing polarity reversal. The predetermined time is not particularly limited, but is preferably reversed within a range of 1 sec to 1 min in order to constantly stabilize the chlorine generation amount.

  Further, as a method for measuring the flow rate of membrane filtrate, as shown in FIG. 2, a membrane meter is installed by arranging a flow meter 6 'in the supply water pipe and a flow meter 6 "in the concentrated water pipe. There is also a method for measuring the flow rate of the feed water supplied to the cartridge 4 and the flow rate of the concentrated water discharged from the membrane filtration cartridge 4 without membrane filtration, and calculating the flow rate of the membrane filtrate from the difference between the flow rate of the feed water and the flow rate of the concentrated water. is there.

  The reason why the lower limit of the chlorine concentration of water stored in the water storage tank is preferably 0.1 mg / L is that the suppression of the growth of general bacteria can be expected greatly, and the upper limit is 0.4 mg / L or less. This is based on the delicious water requirement announced by the Ministry of Health and Welfare's Tasty Water Research Association on April 25, 1985. In addition, the chlorine density | concentration prescribed | regulated by this invention is the numerical value measured by the diethyl-p-phenylenediamine (DPD) method of the drinking water test method (2001).

  Membrane filtrate flowing out from the sterilization unit 7 is stored in the water storage tank 8. Since the water in the water storage tank 8 contains a predetermined amount of chlorine, the proliferation of germs such as general bacteria is suppressed even if left for a long time. On the other hand, water that has not been filtered through the RO membrane or NF membrane is discharged out of the system as concentrated water through the concentrated water valve 5.

  When the raw water supply valve 1 is opened and water purification is continued, the water level of the water storage tank 8 gradually rises, and when it is detected that the water level sensor 8 in the water storage tank 8 has exceeded the predetermined upper limit water level, Is automatically closed, and the supply of tap water to the pretreatment cartridge 2 and the application of voltage to the electrodes of the sterilization unit 7 are automatically stopped. When water is taken from the faucet 10 provided in the water storage tank, and the water level falls below a predetermined lower limit water level, a signal is sent, the raw water supply valve 1 is automatically opened, and the tap water pretreatment cartridge 2 And the voltage application to the electrodes of the sterilization unit 7 is automatically restored.

  When the tap water pressure is too low to secure a predetermined amount of membrane filtration treatment water, it is preferable to provide the pressurization pump 3 in the previous stage of the membrane filtration cartridge 4 to pressurize the water before the membrane filtration cartridge. At this time, the pressure pump 3 is interlocked with the raw water supply valve 1, and the pressure pump 3 operates when the raw water supply valve 1 is open, and the pressure pump 3 stops when the raw water supply valve 1 is closed. It is preferable to do so. In FIG. 1, the faucet 10 is attached to the lower part of the water storage tank 8, and water is discharged by its own weight when the faucet 10 is opened. When the faucet 10 is attached to the upper part of the water storage tank 8, a pump (not shown) may be provided at the lower part of the water storage tank 8 so that the water can be pumped.

Example 1
Using a water purifier equipped with the water treatment process shown in FIG. 1, tap water with a tap water pressure of 300 kPa, chromaticity of 4 degrees, electrical conductivity of 200 μS / cm, and residual chlorine of 0.7 mg / L is obtained from Monday to Friday. Was treated with 5 L of water every day and discharged out of the system.

The pretreatment cartridge 2 in the water purifier used here is a cartridge having the structure shown in FIG. 3, and the filter 2a is a wind filter having an average pore diameter of 1 μm (manufactured by Advantech Toyo Co., Ltd., TCW-1N-PPS). 100 g of granular activated carbon (Kuraray Chemical Co., Ltd., Kuraray Coal T-SB 24/42 mesh) was used for the silver-impregnated activated carbon 2b. As the membrane in the membrane cartridge 4, 1 m ² of NF membrane (manufactured by Toray Industries, Inc., UTC-60) was used. The pressurizing pump 3 was not used.

  As the sterilizing unit 7, a structure shown in FIG. 4 is used, and as the electrode 11, a plate made of titanium plated with platinum having a thickness of 1 μm for both electrodes (size: 10 mm × 30 mm, thickness 1 mm) is arranged face to face. . As the water storage tank 8, a 6L capacity ABS resin tank was used. A throttle valve was used as the concentrated water valve 5, and an impeller type micro flow meter was used as the flow meter 6.

  In the control of the sterilization unit 7, the polarity of the voltage applied to the electrode is reversed every 10 s, the relationship between the current X (mA) and the flow rate Y (mL / min) of the membrane filtrate is Y = 200X, Was proportional to the flow rate.

  As a result of continuous water purification treatment for 5 days a week, the flow rate of membrane filtrate immediately after the start of operation was 200 mL / min, whereas the flow rate of membrane filtrate after 6 months from the start of operation was reduced to 70 mL / min. Nevertheless, the chlorine concentration of the water sampled from the tap 10 for discharging the purified water can be maintained within a good range of 0.2 to 0.3 mg / L over a long period of 6 months from the start of operation. The general bacteria during that period were always 10 cfu / mL or less.

(Example 2)
Using a water purifier equipped with a water treatment process shown in FIG. 2, tap water having a tap water pressure of 400 kPa, a chromaticity of 5 degrees, an electrical conductivity of 450 μS / cm, and a residual chlorine of 0.9 mg / L is obtained on weekdays from Monday to Friday. Was treated with 5 L of water every day and discharged out of the system.

  The pretreatment cartridge 2, membrane cartridge 4, sterilization unit 7, water storage tank 8, and concentrated water valve 5 in the water purifier used here were the same as those in Example 1. The pressurizing pump 3 was not used. As the flowmeters 6 ′ and 6 ″, the same one as the flowmeter 6 of Example 1 was used.

  In the control of the sterilization unit 7, the voltage applied to the electrode is set to 4 V, the polarity of the voltage applied to the electrode is reversed every 10 s, and the current X (mA) and the membrane filtered water when the continuous voltage of 20 s is applied at this time Voltage application pause time (s) = 4000X / Y-20 was calculated from the flow rate Y (mL / min), and voltage application was paused. After the end of the rest, a continuous voltage was applied again for 20 s and the same control was repeated.

  As a result of continuous water purification treatment for 5 days a week, the flow rate of membrane filtrate immediately after the start of operation was 250 mL / min, whereas the flow rate of membrane filtrate after 6 months from the start of operation was reduced to 80 mL / min. Nevertheless, the chlorine concentration of the water sampled from the tap 10 for discharging the purified water can be maintained within a good range of 0.2 to 0.3 mg / L over a long period of 6 months from the start of operation. The general bacteria during that period were always 10 cfu / mL or less.

(Comparative Example 1)
Except that the flow meter 6 was not installed, the same water purifier as in Example 1 was used, and the water purification treatment was performed under the same conditions as in Example 1 except that the current value between the electrodes was controlled to be constant at 1 mA. As a result, the chlorine concentration of water sampled from the faucet 10 for discharging purified water immediately after the start of operation was 0.2 to 0.3 mg / L, but the chlorine concentration gradually increased and six months after the start of operation. The chlorine concentration of the sample was very high at 0.7 to 0.9 mg / L, and the unpleasant odor of chlorine was strongly felt. The number of general bacteria during that period was always 10 cfu / mL or less.

(Comparative Example 2)
Except that the sterilization unit 7 was not installed, the same water purifier as in Example 1 was used, and a water purification treatment experiment 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 2,000 cfu / mL, and in particular, the general bacteria of water sampled on Monday at the beginning of the week is significantly over 10,000 cfu / mL. it was high.

(Comparative Example 3)
Instead of installing the sterilizing unit 7, instead, a column packed with 10 g of granular activated carbon (Kuraray Chemical T-SB 24/42 mesh, manufactured by Kuraray Chemical Co., Ltd.) was used. Except for flowing into the water storage tank 8, 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 silver ion concentration of water sampled from the tap 10 was always 100 cfu / mL or less for general bacteria for 7 days from the start of operation. However, the general bacteria of water collected from Tuesday to Friday after the passage of 7 days is as high as 100 to 1,000 cfu / mL, and in particular, the general bacteria of water sampled on Monday at the beginning of the week is 10,000 cfu / mL or more. It was remarkably high.

  According to the water purifier and water purification method of the present invention, tap water can be highly purified by the RO membrane or NF membrane, so it is suitable for use in beverages and cooking, and is safe and high-quality by a small water purifier. You can get water.

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 schematic flowchart which shows another 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 structural schematic which shows one implementation structure of the sterilization unit integrated in the water purifier which concerns on this invention, Comprising: A front cross section, a left side cross section, and a plane cross section are shown, respectively.

Explanation of symbols

1: On-off valve for supplying tap water 2: Pretreatment cartridge 2a: Filter filtration unit 2b: Silver impregnated activated carbon filtration unit 3: Pressurization pump 4: Membrane filtration cartridge 5: Concentrated water valves 6, 6 ', 6 ": Flow meter 7: Sterilization unit 8: Reservoir tank 9: Water level sensor 10: Faucet for water purification 11: Electrode 12: Electric wire 13: Insulator

Claims (13)

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, generating chlorine from an electrode to which a voltage is applied, and setting the chlorine concentration of the water in the water storage tank to 0.1 to 0.4 mg / L The water purifier is characterized in that a sterilizing unit that can be controlled to a minimum is disposed between the membrane filtration cartridge and the water storage tank. An electric circuit that arranges a flow meter for measuring the flow rate of the membrane filtrate in the membrane filtrate pipe and proportionally controls the current of the electrode of the sterilization unit according to the flow rate of the membrane filtrate measured by the flow meter. The water purifier according to claim 1, wherein the water purifier is provided. A flow meter for measuring the flow rate of the supplied water supplied to the membrane filtration cartridge is disposed in the supply water piping, and a flow meter for measuring the flow rate of the concentrated water discharged from the membrane filtration cartridge without being subjected to membrane filtration is disposed in the concentrated water piping. The electric circuit which carries out proportional control of the electric current of the electrode of the said sterilization unit according to the membrane filtration flow computed from the difference of the supply water flow and the concentration water flow is arranged in Claim 1 characterized by the above-mentioned. Water purifier. A flow meter for measuring the flow rate of the membrane filtrate is disposed in the membrane filtrate pipe, and the flow rate of the membrane filtrate measured by the flow meter and the electrode when a constant voltage is applied to the electrode of the sterilization unit. The water purifier according to claim 1, further comprising an electric circuit that controls a voltage application time and a voltage application pause time of the electrode of the sterilization unit based on a current value. A flow meter for measuring the flow rate of the supplied water supplied to the membrane filtration cartridge is disposed in the supply water piping, and a flow meter for measuring the flow rate of the concentrated water discharged from the membrane filtration cartridge without being subjected to membrane filtration is disposed in the concentrated water piping. The voltage of the electrode of the sterilization unit is calculated from the flow rate of the membrane filtrate calculated from the difference between the supply water flow rate and the concentrated water flow rate and the current value of the electrode when a constant voltage is applied to the electrode of the sterilization unit. The water purifier according to claim 1, further comprising an electric circuit for controlling the application time and the voltage application pause time. The water purifier according to any one of claims 1 to 5, wherein the sterilizing unit includes an electric circuit that reverses the polarity of a voltage applied to the electrode every predetermined time. The water purifier according to any one of claims 1 to 6, wherein a filter filtration cartridge including a filter having an average pore diameter of 0.1 to 10 µm is disposed on the upstream side of the membrane filtration cartridge. 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 that generates chlorine from an electrode to which a voltage is applied, and is stored in a water storage tank. The chlorine concentration of water stored in the water storage tank is 0.1 to A water purification method characterized in that the concentration is 0.4 mg / L. The flow rate of the membrane filtration water after the membrane filtration treatment is measured by a flow meter, and the current of the electrode of the sterilization unit is proportionally controlled according to the flow rate of the membrane filtration water. Water purification method. The flow rate of the feed water supplied to the membrane filtration treatment and the flow rate of the concentrated water discharged from the membrane filtration treatment were measured with a flow meter, and the membrane filtrate calculated from the difference between the supply water flow rate and the concentrated water flow rate The water purification method according to claim 8, wherein the current of the electrode of the sterilization unit is proportionally controlled according to the flow rate of the sterilization unit. The flow rate of the membrane filtration water is measured with a flow meter, and the voltage application time and voltage of the sterilization unit electrode according to the flow rate of the membrane filtration water and the current value of the sterilization unit electrode when a constant voltage is applied The water purification method according to claim 8, wherein the application pause time is controlled. The flow rate of the feed water supplied to the membrane filtration treatment and the flow rate of the concentrated water discharged from the membrane filtration treatment were measured with a flow meter, and the membrane filtrate calculated from the difference between the supply water flow rate and the concentrated water flow rate 9. The purified water according to claim 8, wherein the voltage application time and the voltage application pause time of the sterilization unit electrode are controlled according to the flow rate of the sterilization unit and the current value of the sterilization unit electrode when a constant voltage is applied. Method. The water purification method according to any one of claims 8 to 12, wherein the polarity of the voltage applied to the electrode of the sterilizing unit is reversed every predetermined time.

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