JP2008100175A - Daily life water feed method and arrangement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a daily life water production method which enables a yield of soft water, hard water and pure water without carrying out pH adjustment and flow rate adjustment by a simple apparatus containing an electric softening apparatus, and an arrangement. <P>SOLUTION: The daily life feed method and the arrangement comprise a desalinization process of treating raw water by a reverse osmosis membrane system 10 to yield thickened water and permeated water, and a hardness adjustment process of passing raw water through a softening chamber of an electric softening apparatus 20, introducing the thickened water yielded from the reverse osmosis membrane system 10 into a substitution chamber to obtain soft water from the softening chamber and hard water from the substitution chamber, wherein at least raw water, soft water and permeated water are fed to a use point as daily life water. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a domestic water supply method and apparatus for processing raw water such as tap water and supplying at least raw water, soft water and pure water as domestic water.

  With the recent health boom or improvement in living standards, soft water, pure water, acidic water, or alkaline water is actively used as domestic water in addition to tap water. In particular, since soft water enhances the cleaning effect of detergents and soaps, there is a demand for a system that is suitable for use in baths, bathrooms, laundry, and the like and can be supplied in abundance. In addition, pure water is suitable for use in washing, dishwashing, cooking, and the like, and there is a demand for a system that can supply abundantly like soft water.

  Japanese Patent Application Laid-Open No. 9-151503 has a purifying unit that purifies tap water and a water quality adjusting unit that adjusts the quality of the purified water according to the purpose of use. A supply purification system is disclosed. According to this purification system, it is possible to supply tap water with a water quality adjusted to the purpose of use to an appropriate place.

  Japanese Patent Application Laid-Open No. 2002-143854 discloses a first electrode and a second electrode that are provided opposite to each other in an electrolytic cell and are capable of electrochemically treating raw water, a positive potential on the first electrode, In order to form a plurality of cells between the power supply unit for applying a negative potential to the second electrode and between the first electrode and the second electrode, there is an interval between the first electrode and the second electrode. A plurality of ion exchange membranes arranged in a predetermined order, an introduction path that is provided with a flow rate adjustment valve and can pass water to each of the plurality of cells, and a discharge path that discharges treated water from each of the plurality of cells A plurality of ion exchange membranes comprising a monovalent anion selective anion exchange membrane, a non-ion selective anion exchange membrane, a non-ion selective cation exchange membrane, Consists of monovalent cation selective cation exchange membranes It is, and electrochemical water treatment device are arranged in this order between the said first electrode to said second electrode is disclosed. According to this electrochemical water treatment apparatus, deionized water, Na-type soft water, mineral water rich in divalent ions, alkaline water, acidic water and various types of water can be easily generated with one apparatus.

Japanese Patent Application Laid-Open No. 8-108184 discloses that raw water mixed with monovalent cations and divalent cations is supplied to an electrodialysis cell, and a monovalent ion selective permeable cation exchange membrane and a non-selective permeable cation exchange membrane are used. A water treatment system that simultaneously obtains treated water rich in valence ions and less divalent ions and treated water rich in divalent ions and less monovalent ions is disclosed. According to this water treatment system, hydrogen-type soft water, alkaline water, and acidic water can be efficiently generated as deionized water.
JP-A-9-151503 (Claim 1) JP 2002-143854 A (Claim 1, FIG. 1) JP-A-8-108184 (Claim 1, FIG. 1)

  However, the purification system disclosed in Japanese Patent Application Laid-Open No. 9-151503 has various means such as foreign matter removing means, odor removing means, harmful substance removing means, suitable temperature adjusting means, ion removing means, mineral adding means, pH adjusting means, and gas adding means. There is a problem that the installation cost increases and the piping becomes complicated.

  In addition, the electrochemical water treatment apparatus disclosed in JP-A-2002-143854 can easily obtain pure water, acidic water and alkaline water, but in order to produce soft water and hard water, the obtained acidic water and alkaline water are used. Therefore, there is a problem that the pH is carefully adjusted or the amount of water passing through the weak acid water generation cell and the weak alkaline water generation cell is inevitably adjusted. In addition, the electrochemical water treatment apparatus needs to be operated at a high voltage because tap water is raw water and the distance between the electrodes is large.

  Further, in the electrodialysis cell disclosed in JP-A-8-108184, cations of water to be treated that have flowed into the concentration chamber permeate the non-selective cation exchange membrane by DC voltage and are carried to the desalting chamber. On the other hand, the anion in the water to be treated cannot permeate through the non-selective cation exchange membrane or the stainless partition, and remains in the concentration chamber. As a result, the concentration chamber becomes anion-rich and the pH is lowered. When pH decreases, the proportion of hydrogen ions in the cations that move through the non-selective cation exchange membrane increases, so the rate of movement of calcium ions and magnesium ions decreases, so-called current efficiency decreases. There is a problem of inviting a phenomenon.

  Accordingly, an object of the present invention is to obtain soft water, hard water and pure water without adjusting pH with a simple device including an electrosoftening device, and the electrosoftening device has low voltage and current efficiency. An object of the present invention is to provide a domestic water supply method and apparatus that does not cause a decrease phenomenon.

  Under such circumstances, the present inventor has conducted intensive studies, and as a result, processed the raw water with a reverse osmosis membrane device to obtain concentrated water and permeate, and monovalent cation selective permeation between the anode chamber and the cathode chamber. Membranes and cation exchange membranes are placed alternately to form a water passage between them, DC voltage is applied, and raw water is passed through the water passage chamber (softening chamber) located on the cathode side of the monovalent cation selective permeation membrane, Concentrated water obtained from the reverse osmosis membrane device flows into a water flow chamber (replacement chamber) located on the anode side of the monovalent cation selective permeation membrane to adjust the hardness to obtain soft water from the softening chamber and hard water from the replacement chamber And at least raw water, soft water, and permeated water to be used as water for daily life as a daily use water, a simple device including an electrosoftening device, soft water, hard water without pH adjustment or flow rate adjustment In addition, it is possible to obtain pure water. It has been found that the hardness component in hard water can be freely removed from a desired softening rate to a remarkably high softening rate depending on the purpose without causing a phenomenon of lowering current efficiency with pressure, and the present invention has been completed. It was.

  That is, the present invention alternately arranges a monovalent cation selective permeable membrane and a cation exchange membrane between the anode chamber and the cathode chamber, and a desalting step in which the raw water is treated with a reverse osmosis membrane device to obtain concentrated water and permeated water. Then, a water passage is made between them, DC voltage is applied, raw water is passed through the water passage (softening chamber) located on the cathode side of the monovalent cation selective permeable membrane, and the anode side of the monovalent cation selective permeable membrane And a hardness adjusting step of flowing concentrated water obtained from the reverse osmosis membrane device into a water flow chamber (replacement chamber) located in the water chamber, obtaining soft water from the softening chamber, and hard water from the replacement chamber, and at least raw water Further, the present invention provides a domestic water supply method for supplying soft water and permeated water to a point of use as domestic water.

  The present invention also provides a reverse osmosis membrane device, a monovalent cation selective permeable membrane and a cation exchange membrane alternately arranged between an anode chamber and a cathode chamber, and a water passage between them. A water supply device for domestic use comprising an electric softening device having a water flow chamber located on the cathode side as a softening chamber and a water flow chamber located on the anode side of the monovalent cation selective permeation membrane as a replacement chamber, the reverse osmosis membrane A raw water introduction pipe is arranged on the raw water side of the apparatus, a concentrated water outflow pipe is arranged on the concentrated water side, a permeate outflow pipe is arranged on the permeate side, and the raw water introduction pipe is connected to the softening chamber of the electric softener. A branch pipe for branching and a soft water outflow pipe are connected to the replacement chamber, and a concentrated water introduction pipe and a hardness component concentrated water outflow pipe connected to the concentrated water outflow pipe of the reverse osmosis membrane device are provided in the anode chamber and the cathode chamber, respectively. The electrode water introduction pipe and the outflow pipe are arranged respectively, and the raw water introduction pipe and the raw water Life that distributes raw water supply pipes that connect use points, soft water supply pipes that connect soft water outflow pipes and soft water use points, and permeate water supply pipes that connect permeate outflow pipes and permeate use points A water supply apparatus is provided.

  According to the domestic water supply method of the present invention, soft water, hard water and pure water can be obtained using a simple device including an electrosoftening device without adjusting pH. In addition, since the raw water is passed through the softening chamber of the electrosoftening device used in the present invention and the concentrated water of the reverse osmosis membrane device is passed through the replacement chamber and energized, the softening chamber contains monovalent cations and divalent cations in the raw water. It passes through the cation exchange membrane and moves to the substitution chamber. At the same time, in the substitution chamber, mainly monovalent cations in the substitution water permeate the monovalent cation selective permeation membrane and move to the softening chamber. For this reason, soft water can be obtained by substituting the monovalent cation for the hardness component in the water to be treated. Further, in the electrosoftening device, the cation transport rate is the same in any of the softening chambers and the replacement chambers, and the pH does not decrease, so that the current efficiency does not decrease. Further, since the concentrated water of the reverse osmosis membrane device is passed through the replacement chamber of the electrosoftening device, it can be operated at a low voltage.

  In the domestic water supply method and apparatus of the present invention (hereinafter referred to as “in the present invention” when referring to two inventions), the raw water is water such as tap water used as domestic water, Usually, it contains a hardness component of about 1 to 2 equivalents relative to alkali metal ions. Tap water usually contains divalent cations such as calcium ion and magnesium ion, strong electrolyte such as sodium ion, potassium ion, chloride ion, nitrate ion and sulfate ion, weak electrolyte such as carbonate ion and silica, etc. Impurities are included in various ratios.

  In the present invention, the water for daily use is various types of water that is necessary for a human being used in a dining room, a washroom, a bathroom, etc. to live a life, and includes drinking water. For this reason, people living in water such as single-family houses, apartment houses, and temporary houses, as well as company offices, factories, laboratories, research laboratories, hospitals, and lodging facilities are active. The place to do is also included.

  Next, a domestic water supply method and a domestic water supply apparatus according to an embodiment of the present invention will be described with reference to FIGS. The domestic water supply device 50 of this example includes the reverse osmosis membrane device 10 and the electrosoftening device 20. In the reverse osmosis membrane device 10, a raw water supply pipe j is arranged on the raw water side, a concentrated water outflow pipe c is arranged on the concentrating side, and a permeated water outflow pipe i is arranged on the permeating side. Is a branch pipe a and a soft water outflow pipe b branching from the raw water introduction pipe j, a replacement chamber 2 is provided with a concentrated water introduction pipe c and a hardness component concentrated water outflow pipe d of the reverse osmosis membrane device 10, an anode chamber 6 and a cathode chamber. 5, the electrode water introduction pipes e and g and the outflow pipes f and h are respectively arranged, the raw water supply pipe K connecting the raw water supply first pipe j and the raw water use point, the soft water outflow pipe b and the soft water use point. Soft water supply pipe B connecting permeate water outflow pipe i and permeate water supply pipe I connecting permeate use point, acid water supply pipe F connecting acid water outflow pipe f and acid water use point, alkaline Alkaline water supply distribution that connects water outlet pipe h and alkaline water use point To distribution H, respectively. In the present invention, the acidic water supply pipe F that connects the acidic water outflow pipe f and the acidic water use point, and the alkaline water supply pipe H that connects the alkaline water outflow pipe h and the alkaline water use point are optional components. is there. In addition, when not supplying acidic water and alkaline water, these should just flow to a drain outlet.

  The reverse osmosis membrane device (RO) 10 is not particularly limited, and a known reverse osmosis membrane device can be used. Various types of RO membranes can be used, from high pressure membranes of 3.9 MPa or higher to ultralow pressure membranes of 0.98 MPa or lower. Further, as the RO membrane, a membrane of cellulose acetate and its derivatives or a synthetic polymer membrane can be used. The reverse osmosis membrane device is usually used as a device (module) in which the membrane is housed in a type that can be industrially used. Examples of the module form include a hollow fiber type, a spiral type, a flat plate type, a tube type, and a hollow fiber type.

  As shown in FIG. 2, the electrosoftening device 20 includes a monovalent cation selective permeable membrane 4 and a cation exchange membrane 3 alternately between an anode chamber 6 adjacent to the anode 7 and a cathode chamber 5 adjacent to the cathode 8. The water passage located between the monovalent cation selective permeation membrane 4 and the water flow chamber located on the cathode 8 side is referred to as the softening chamber 1 and the monovalent cation selective permeation membrane 4 is located on the anode 7 side. The chamber is a replacement chamber 2. The ion exchange membrane adjacent to the anode chamber 6 is a monovalent cation selective permeable membrane 4 as in this example, so that the hardness component from entering the electrosoftening device from the water flowing through the anode chamber 6 can be prevented. It is preferable in that it can be performed.

  Although the monovalent cation selective permeable membrane 4 is not particularly limited, a cation exchange membrane in which a thin layer of polycation is completely fixed on the membrane surface can be used. Since the electrostatic repulsion between the polycation, which is a positively charged barrier existing on the membrane surface, and the ion to be permeated is larger for the divalent cation than for the monovalent cation, Permeation of the membrane is hindered. As such a monovalent cation selective permeable membrane, a commercially available one can be used.

  The cation exchange membrane is obtained by forming a three-dimensional cross-linked polymer such as a styrene-divinylbenzene copolymer into a matrix and introducing an anionic dissociating group such as a sulfo group as a cation exchange group. . In order to compensate for the mechanical weakness when styrene-divinylbenzene is molded into a film, a plasticizer such as dioctyl phthalate is generally added to give flexibility, and a reinforcing material net made of polyvinyl chloride is the core. It is used as a material. Cation exchange membranes are classified into homogeneous membranes and heterogeneous membranes, depending on how they are made. Homogeneous membrane is obtained by impregnating or applying a monomer to the reinforcing material net and polymerizing and molding, and heterogeneous membrane is obtained by pulverizing particulate cation exchange resin formed by suspension polymerization or the like. A fine powdered ion exchange resin is combined with a binder for fixing the resin and applied to a reinforcing material net to form a film. As the cation exchange membrane 3, a cation exchange membrane which is the above-described cation exchange membrane and which is not subjected to immobilization of the polycation thin film for imparting the monovalent cation selective permeability is used.

  Next, a method for supplying domestic water using the domestic water supply apparatus 50 of this example will be described. In order to supply domestic water using the domestic water supply apparatus 50, the raw water is processed by the reverse osmosis membrane apparatus 10 to obtain concentrated water and permeated water (pure water), the anode chamber 6 and the cathode chamber 5. The monovalent cation selective permeable membrane 4 and the cation exchange membrane 3 are alternately arranged between them to serve as a water passage, and a direct current voltage is applied to the water passage chamber (on the cathode side of the monovalent cation selective permeable membrane 4) ( Condensed water obtained from the reverse osmosis membrane device 10 flows into the water flow chamber (substitution chamber) 2 located on the anode side of the monovalent cation selective permeable membrane 4. To obtain hard water from the replacement chamber 2 and supply at least raw water, soft water and permeated water, preferably raw water, soft water, permeated water, acidic water and alkaline water to the point of use as domestic water .

  The RO permeated water obtained in step I is supplied to the point of use as pure water after removing impurity ions and the like in the raw water. Pure water is suitable for washing, dishwashing and cooking. The RO concentrated water obtained in step I is sent to the replacement chamber 2 of the electrosoftening device 20. In RO concentrated water, impurities in the raw water are concentrated, and by passing this water through the replacement chamber of the electrosoftening device, it becomes possible to supply high-concentration monovalent cations to the softening chamber and soften it. Is preferably achieved.

  In step II, raw water containing hardness components is passed through the raw water introduction pipe a into the softening chamber 1 located on the cathode 8 side of the monovalent cation selective permeable membrane, and the monovalent cation selective permeable membrane 4 is located on the anode 7 side. Into the replacement chamber 2, replacement water containing monovalent cations, that is, RO concentrated water is passed through the replacement water introduction pipe c, and a DC potential is applied to the cathode 8 and the anode 7.

  When water is passed through the electrosoftening device 20 and energized, monovalent cations and divalent cations (hardness components) in the raw water pass through the cation exchange membrane 3 and move to the substitution chamber 2 in the softening chamber 1. At the same time, in the substitution chamber 2, mainly monovalent cations in the substitution water permeate the monovalent cation selective permeable membrane 4 and move to the softening chamber 1. Thus, in the softening chamber 1, soft water is obtained continuously by sequentially substituting divalent cations in the raw water with monovalent cations, and in the substitution chamber 2, the monovalent cations in the substitution water are converted into divalent cations. Concentrated water in which the hardness component is continuously concentrated can be obtained by successive substitution. Further, in the electrosoftening device 20, the cation transport rate is the same in any of the softening chamber 1 and the replacement chamber 2, and the pH does not decrease, so that the current efficiency is not reduced.

  In the electrosoftening device 20, the flow direction of the raw water in the softening chamber 1 and the flow direction of the replacement water in the replacement chamber 2 are not particularly limited, but it is preferable that the flow directions are countercurrent as shown in FIG. 2. If the flow direction of the raw water in the softening chamber 1 and the flow direction of the replacement water in the replacement chamber 2 are opposite to each other, the hardness component in the raw water introduced into the softening chamber 1 has a higher charge than a monovalent cation. Since it is easy to move and permeates the cation exchange membrane 3 on the discharge side of the substitution chamber 2, it is quickly discharged out of the system from the softening chamber 1. This makes it difficult for scale to occur on the membrane surface of the monovalent cation selective permeable membrane 4 on the substitution chamber 2 side.

  In the electric softening device 20, the replacement chamber outlet water discharged from the replacement chamber 2 is passed through the pipes d and e to the anode chamber 6 and through the pipes d and g to the cathode chamber 5, respectively. In the electrosoftening device 20, the anode outlet water can be used as acidic water because cations are reduced to lower the pH, and hypochlorous acid is generated by the anodic reaction and has oxidizing power and sterilizing power. Further, the cathode outlet water discharged from the cathode water outflow pipe h can be used as alkaline water having reducibility because cations increase and pH rises and hydrogen gas is generated by the cathode reaction. In order to further increase the pH of the alkaline water, an anion exchange membrane is provided between the cathode 8 and the monovalent cation selective permeable membrane 3 in the immediate vicinity of the cathode in FIG. 2, and the anion exchange membrane and the monovalent cation selective permeation are arranged. A space sandwiched between the membranes 3 can be used as an anion exclusion chamber, and an anion in the cathode water can be excluded to the anion exclusion chamber. The anion exclusion chamber is preferably filled with a cation exchange resin in order to prevent a voltage increase due to the installation of the chamber. The replacement chamber discharge water is branched from the pipe g and supplied to the anion exclusion chamber. The discharged water from the anion exclusion chamber is drained or joined to the pipe f and used as acidic water.

  The soft water obtained in step II is suitably used in bathrooms, toilets, etc. without adjusting the pH. Soft water, like pure water, increases the amount used per day so that it can be supplied in abundance. In order to supply abundant soft water to the point of use, a method of increasing the throughput of the electrosoftening device, a method of increasing the size of the softening storage tank, and the like can be mentioned. Alkaline water is preferably used for cooking and washing foods. Acidic water is suitably used for toilets and food sterilization. If the hard water discharge pipe d in FIG. 2 is further branched so that hard water can be supplied, the hard water can be used for cooking water or the like. Moreover, raw water can be used as domestic water as before, and can be used as emergency water when pure water or soft water cannot be collected. Specifically, the raw water supply pipe K is preferably separately piped so as to be supplied to all domestic water use points.

  Next, a domestic water production method and a domestic water supply apparatus according to another embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. 3 differs from FIG. 1 in that the acidic water storage tank 21 and the acidic water supply pump 22 are placed in the middle of the soft water supply pipe B in the middle of the acidic water supply pipe F from the upstream side toward the downstream side. The soft water storage tank 31 and the soft water supply pump 32, the alkaline water storage tank 41 and the alkaline water supply pump 42 in the middle of the alkaline water supply pipe H, and the permeate water storage tank 51 and the permeated water supply pump in the middle of the permeate water supply pipe I. 52, the acidic water supply pipe on the downstream side of the acidic water storage tank 21 and the acidic water storage tank 21 are connected by the acidic water return pipe 23, and the soft water supply pipe on the downstream side of the soft water storage tank 31 and the soft water storage tank 31. Are connected by the soft water return pipe 33, the alkaline water supply pipe downstream of the alkaline water storage tank 41 and the alkaline water storage tank 41 are connected by the alkaline water return pipe 43, and the permeate water storage tank 51. Permeate water supply pipe and the permeate storage tank 51 on the downstream side is in that it is connected with the permeate return line 53.

  That is, the acid water, soft water, alkaline water and permeated water obtained in each step flow into the respective storage tanks and are supplied from the storage tanks to the use points by the respective supply pumps. The feed water that exceeds the amount used in is returned to the reservoir. For this reason, each domestic water can be stably supplied to a use point. Further, in each of the storage tanks 21 to 51, convenience is provided by adding a means for automatically stopping the apparatus by detecting a high water level and a means for automatically operating the apparatus by detecting a low water level. Increased further.

  In the present invention, the reverse osmosis membrane device 10 is provided with a pretreatment device for removing organic components such as residual chlorine and trihalomethane from the raw water, and fine particles such as iron oxide and silica, from the raw water. It is preferable in that the film surface can be prevented. Specific examples of the pretreatment device include activated carbon and a membrane separation device.

  If domestic water is manufactured using the domestic water supply devices 50 and 50a of this example, soft water, hard water and pure water can be obtained without adjusting pH or flow rate in the electrosoftening device. In particular, it is possible to produce approximately the same amount of soft water and pure water that are used in large amounts. Further, since the replacement water introduced into the replacement chamber 2 of the electrosoftening device 20 is RO concentrated water, the ion concentration is usually about twice that of the raw water, and low voltage operation is possible. Moreover, acidic water and alkaline water having a predetermined pH can be obtained from the electrode chamber.

  In the present invention, at least the softening chamber, preferably the softening chamber and the replacement chamber, more preferably all of the softening chamber, the substitution chamber, the anode chamber, and the cathode chamber of the electrosoftening device may be filled with a cation exchanger. it can. By filling the softening chamber 1 with a cation exchanger, divalent cations with high ion exchange selectivity can be more selectively excluded into the substitution chamber 2. In addition, since the cation exchanger itself has conductivity, filling the softening chamber, the replacement chamber, the cathode chamber, or the anode chamber can lower the energization resistance value of the device stack and reduce the power consumption. In the present invention, the cation exchanger is not particularly limited, and examples thereof include cation exchange resins, cation exchange fibers, and organic porous cation exchangers.

  In the present invention, it is preferable that the alkaline water storage tank 41 and the permeated water storage tank 51 are provided with a sterilization facility from the viewpoint of preventing microbial growth in the alkaline water and the permeated water in the storage tank. Examples of the sterilization facility include an ultraviolet irradiation method or a method of installing a filter with silver in a storage tank and a storage tank outlet pipe.

  In the present invention, the reverse osmosis membrane device 10 may be a multistage of a front stage and a rear stage. That is, recovery of RO permeated water (pure water) can be enhanced by using the concentrated water obtained from the upstream reverse osmosis membrane device as the treated water of the downstream reverse osmosis membrane device. Moreover, when installing a pressure | voltage rise pump in the front | former stage of a reverse osmosis membrane, collection | recovery of RO permeated water (pure water) can be improved also by circulating a part of concentrated water upstream of this pump.

  Next, the present invention will be described more specifically with reference to examples. However, this is merely an example and does not limit the present invention.

  According to the flow chart of the domestic water supply device shown in FIG. 3, 1280 L / day of tap water is supplied to the softening chamber of the electric softening device of FIG. 2, and the concentrated water of the reverse osmosis membrane device is supplied to the replacement chamber. The acidic water, soft water, alkaline water and permeated water were obtained by treatment under the following operating conditions. The results are shown in Table 1. In addition, the tap water used what passed the activated carbon + microfiltration filter (D-4 form + FU cartridge, the organo company make).

<Reverse osmosis membrane device>
・ RO membrane module (RE2012-LP x 2; manufactured by Sehan)
・ Tap water supply amount: 871 L / day ・ RO concentrated water amount: 442 L / day, RO permeated water amount: 429 L / day ・ RO recovery rate: 49%

<Electro softening device>
・ RO concentrated water volume: 442 L / day ・ Tap water supply volume: 409 L / day ・ Acidic water volume: 390 L / day ・ Soft water volume: 409 L / day ・ Alkaline water volume: 52 L / day

<Reservoir>
・ Capacity of acidic water storage tank and alkaline water storage tank; 50L each
・ Capacity of soft water storage tank: 150L
・ Capacity of permeate storage tank: 100L
Table 1 shows the operation results.

As is apparent from Table 1, in the examples, pure water and soft water could be supplied in abundant amounts at substantially the same amount. Carried out in the example, the hardness load tap water is _{755mgCaCO 3 /h(44.4mgCaCO 3 / l × 17L} / h), RO permeate (substituted water) or more equivalents of monovalent cations amount 893MgCaCO ₃ of the hardness components / h (49.6 mg CaCO ₃ / l × 18 L / h), and a good softening treatment was performed. The hardness of the soft water was 2.6 mg CaCO ₃ / L, and the hardness removal rate was 94%.

It is a flowchart of the domestic water supply apparatus in this Embodiment. It is a flowchart of the electric water softener used with the domestic water supply apparatus of FIG. It is a flowchart of the domestic water supply apparatus in other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Softening chamber 2 Displacement chamber 3 Cation exchange membrane 4 Monovalent cation selective permeable membrane 5 Cathode chamber 6 Anode chamber 7 Anode 8 Cathode 10 Reverse osmosis membrane apparatus aj, B, F, H, I Piping 20 Electrosoftening apparatus 21 Acidity Water storage tank 31 Soft water storage tank 41 Alkaline water storage tank 51 Permeated water storage tank 22, 32, 42, 52 Pump 23, 33, 43, 53 Return pipe 50, 50a Domestic water supply device

Claims (8)

A desalting step of treating the raw water with a reverse osmosis membrane device to obtain concentrated water and permeated water;
A monovalent cation selective permeable membrane and a cation exchange membrane are alternately arranged between the anode chamber and the cathode chamber, and a water passage is formed between them. A DC voltage is applied, and a monovalent cation selective permeable membrane located on the cathode side of the monovalent cation selective permeable membrane is placed. The raw water is passed through the water chamber (softening chamber), the concentrated water obtained from the reverse osmosis membrane device is introduced into the water passage chamber (substitution chamber) located on the anode side of the monovalent cation selective permeable membrane, and the softening chamber And a hardness adjusting step of obtaining hard water from the replacement chamber, and supplying at least raw water, soft water, and permeated water to the point of use as domestic water.   The soft water obtained in the hardness adjustment step and the permeated water obtained in the desalting step flow into the respective storage tanks and are supplied from the storage tanks to the point of use and used at the point of use. The supply water for domestic use according to claim 1, wherein the supply water exceeding 1 is returned to the storage tank.   The method of supplying water for daily use according to claim 1 or 2, wherein acidic water obtained from the anode chamber and alkaline water obtained from the cathode chamber are respectively supplied to the point of use as domestic water.   The acidic water and alkaline water flow into the respective storage tanks and are supplied from the storage tanks to the use points, and water exceeding the amount used at the use points is returned to the storage tanks. The domestic water supply method according to claim 3. A reverse osmosis membrane device;
A monovalent cation selective permeation membrane and a cation exchange membrane are alternately arranged between the anode chamber and the cathode chamber to serve as a water passage chamber, and a water passage chamber located on the cathode side of the monovalent cation selective permeation membrane as a softening chamber. A water supply device for domestic use comprising an electrosoftening device having a water passage located on the anode side of the monovalent cation selective permeable membrane as a replacement chamber
The reverse osmosis membrane device is provided with a raw water introduction pipe on the raw water side, a concentrated water outflow pipe on the concentrated water side, and a permeate outflow pipe on the permeate side,
A branch pipe and a soft water outflow pipe branching from the raw water introduction pipe are provided in the softening chamber of the electric softening device, and a concentrated water introduction pipe and a hardness component concentrated water connected to the concentrated water outflow pipe of the reverse osmosis membrane device are provided in the replacement chamber. An outflow pipe is arranged in each of the anode chamber and the cathode chamber with an electrode water introduction pipe and an outflow pipe,
Raw water supply pipe connecting the raw water introduction pipe and the raw water use point;
A soft water supply pipe connecting the soft water outflow pipe and the soft water use point;
A domestic water supply device characterized by comprising a permeate outflow pipe and a permeate supply pipe connecting permeate use points.   A soft water storage tank is provided in the middle of the soft water supply pipe, and a permeate water storage tank is provided in the middle of the permeate water supply pipe, and the soft water supply pipe on the downstream side of the soft water storage tank and the soft water storage tank are connected by a soft water return pipe. 6. The domestic water supply device according to claim 5, wherein the permeate water supply pipe downstream of the permeate water storage tank and the permeate water storage tank are connected by a permeate return pipe.   An acidic water supply pipe connecting the anode water outflow pipe of the electric softening device and the acidic water use point, and an alkaline water supply pipe connecting the cathode water outflow pipe of the electric softening device and the alkaline water use point are arranged, An acidic water storage tank is provided in the middle of the acidic water supply pipe, an alkaline water storage tank is provided in the middle of the alkaline water supply pipe, and the acidic water supply pipe on the downstream side of the acidic water storage tank and the acidic water storage tank are acidic. The water for domestic use according to claim 5 or 6, wherein the water is connected by a water return pipe, and the alkaline water supply pipe on the downstream side of the alkaline water storage tank and the alkaline water storage tank are respectively connected by an alkaline water return pipe. Feeding device.   The water supply device for domestic use according to any one of claims 5 to 7, wherein a pretreatment device for removing an organic component from the raw water is installed in a front stage of the reverse osmosis membrane device.

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