JP2004261798A - Desalting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for desalting raw water containing at least a water soluble salt industrially and economically. <P>SOLUTION: The method for desalting raw water includes at least a first process for removing moisture of raw water containing at least a water soluble salt to concentrate the raw water and a second process for removing at least a part of the water soluble salt from the concentrated raw water. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a desalination method, desalinated water obtained by the method, and a desalination apparatus. More specifically, water containing at least a water-soluble salt (hereinafter simply referred to as "raw water" or "brine") is used in the raw water. The present invention relates to a method for efficiently desalting organic valuables (hereinafter, simply referred to as "valuables") contained in the water, and desalinated water and a desalination apparatus obtained by the method.

  Conventionally, various methods have been proposed for collecting only water from various raw waters and for removing salts contained in the raw water. By these methods, drinking water, water used in the chemical industry and the electronics industry, water used in medicine and medicine, water containing valuables, and the like are produced. For example, as a device for extracting fresh water from seawater, a normal pressure or vacuum distillation device, a separation membrane device such as a reverse osmosis membrane, or an electrodialysis device has been put to practical use.

  The above-mentioned distillation apparatus, reverse osmosis membrane apparatus, ultrafiltration membrane apparatus and the like are used for concentrating and purifying raw water containing valuable materials such as pharmaceutical raw materials, pigments and silica sol. In addition, an ion exchange resin device and an electrodialysis device are used to desalinate raw water. In the production of pure water or ultrapure water, a desalination device using an ion exchange resin or an electrodialysis device is used in combination with a purification or purification device using a reverse osmosis membrane.

  Examples of raw water to be desalted include raw water containing organic or inorganic valuables having physiological activity, such as seawater or deep sea water.

  Many of the valuables in raw water containing substances having biological activity (valuables) such as the deep ocean water are sensitive to temperature, and when exposed to high temperatures during the treatment of raw water, the valuables are May be deteriorated, and the function of the valuable material may be reduced or disappear.

  In the above desalination method, when desalinating raw water by electrodialysis, electric power corresponding to the amount of salt contained in the raw water is required. In addition, as the salt concentration of the raw water decreases as the desalination progresses, the temperature of the raw water increases due to the electric resistance of the raw water, and in many cases, valuable resources (organic substances) contained in the raw water to be desalinated are reduced. It often causes deterioration or deterioration. Also, in the method of desalinating raw water using an ion exchange resin apparatus, it is naturally impossible to desalinate beyond the ion exchange capacity of the ion exchange resin. It requires frequent regeneration of the resin and is not economical for industrial use.

  As a specific desalting method that can be used industrially, a method using a mosaic charged membrane having anionic and cationic ion channels has been proposed (Patent Document 1). As described later, the desalination method using the mosaic charged membrane does not require heat energy as in the distillation method, nor does it require electric energy corresponding to the ion amount of the salt as in electrodialysis, and Regeneration treatment such as ion exchange resin is unnecessary. Further, the mosaic charging membrane to be used has a simple structure, can be manufactured at a low cost, is low in initial investment and running cost of various facilities when configuring a desalination apparatus, and is very economical. In addition, the use of the mosaic charged membrane does not increase the liquid temperature of the raw water during desalination, and thus does not cause deterioration or deterioration of valuables in the raw water due to the increase of the liquid temperature during desalination.

Further, since the mosaic charged membrane is essentially a nonporous membrane, the fractionated molecular weight of the substance separated by the membrane is very small, and valuable substances having a molecular weight larger than the molecular weight of the salt in raw water are separated together with the salt. It has excellent features that are not found in other separation devices and methods, such as not being separated (not leaking from the membrane).
JP 2000-309654 A

  However, the desalination mechanism of the mosaic charged membrane is such that the desalination tank is divided into two parts by the mosaic charged membrane, one of which is used as a raw water tank for supplying raw water, the other is used for dialysis water, and fresh water is supplied. Through a mosaic charged membrane to fresh water in a dialysis tank (hereinafter referred to as “dialysis tank water”). The driving force for desalination at this time is the difference between the salt concentration of the raw water and the salt concentration of the dialysis tank water.When desalinating the raw water at normal pressure using a mosaic charged membrane, the mosaic charged membrane is In the desalination apparatus used, the dialysis tank water had to always keep the salt concentration lower than the raw water in the raw water tank.

  Originally, the mosaic charged membrane is capable of desalting salt in the raw water even if the salt concentration difference between the raw water and the dialysis tank water is small, but the salt concentration difference between the raw water and the dialysis tank water is small. As the rate of desalination decreases. Therefore, even in a desalination method using a mosaic charged membrane, it is necessary to supply a large amount of fresh water such as ion-exchanged water or clean water to a dialysis water tank, which is a problem when industrially performing desalination. Is not economically favorable. Regarding the desalination time, as the salt concentration of the raw water in the raw water tank decreases, the permeation flux of the mosaic charged membrane (the speed at which the salt permeates the membrane) becomes extremely low, and the desalination time becomes extremely long. Therefore, it is a problem in industrialization.

  Accordingly, a first object of the present invention is to provide a desalination method that can industrially and economically desalinate raw water. Further, a second object of the present invention is to provide a desalination method using a mosaic charged membrane, in which the amount of dialysis tank water used is small and the desalination time can be shortened. Further, a third object of the present invention is to provide a method of desalinating raw water without deteriorating the valuables in the raw water in the method for desalinating raw water containing valuables.

  The above object is achieved by the following method of the present invention. That is, the present invention provides a first step of removing water from raw water containing at least a water-soluble salt and concentrating the raw water, and a second step of removing at least a part of the water-soluble salt from the concentrated raw water. And a method for desalting the raw water.

  In the present invention, the first step and the second step can be performed simultaneously. Further, the first step and the second step can be performed only once, respectively, and the first step and the second step can be performed multiple times intermittently or continuously. In addition, a pretreatment step may be placed as needed before the first step, or an intermediate step may be placed between the first step and the second step, and further after the second step. A post-processing step may be provided. The raw water needs to contain at least one kind of alkali metal ion or alkaline earth metal ion. Further, it is preferable that the salt concentration of the raw water is concentrated in the range of 10% by mass to the saturated solubility of the salt.

  In the present invention, the first step can be performed using a distillation and / or reverse osmosis membrane, and the second step can be performed using a mosaic charged membrane. Further, the first step and the second step can be performed simultaneously using a nanofiltration film.

  The raw water desalted in the present invention preferably contains valuable resources. The raw water containing the valuable resource includes seawater or deep sea water. The present invention also provides desalted water obtained by the method of the present invention.

  Further, the present invention is characterized in that at least one concentration device selected from a vacuum distillation device, a normal pressure distillation device, a reverse osmosis membrane device, and a nanofiltration membrane device is combined with a mosaic charged membrane desalination device. And a desalination apparatus. The vacuum distillation apparatus is preferably selected from a centrifugal thin-film vacuum distillation apparatus, a rotary heat transfer surface vacuum distillation apparatus, a high-speed swirling vacuum distillation apparatus, a falling film vacuum distillation apparatus, and a scratch surface vacuum distillation apparatus.

According to the method of the present invention, the following effects can be obtained.
(1) Desalination of raw water can be performed industrially and economically.
(2) In a desalination method using a mosaic charged membrane, the amount of dialysis tank water used is small and the desalination time can be shortened. Further, water obtained at the time of concentration can be used as dialysis tank water.
(3) In the desalination of raw water containing valuables, the raw water can be desalted without damaging the valuables in the raw water.

Next, the present invention will be described in more detail with reference to the best mode for carrying out the invention.
Examples of the raw water to be subjected to the desalting method of the present invention include water containing ions of various salts. Here, at least one kind of salt ion is an ion of sodium, potassium, magnesium, calcium, or the like. A typical example of raw water is seawater. Conventionally, when producing freshwater or salt from seawater, mainly surface seawater (seawater in a shallow portion of the sea) is used.

  The seawater contains ions of lithium, zinc, iron, copper, aluminum, manganese, molybdenum, nickel, uranium and the like in addition to the ions of the salt. On the other hand, in recent years, seawater in the deep sea having a depth of 200 m or more (referred to as deep seawater) has attracted attention, and since the deep seawater contains useful valuables (organic substances) and useful minerals, cosmetics, It is a raw material for physiologically active water and beverages, and is a useful raw water in the present invention.

  The mosaic charged membrane used in the present invention is a membrane composed of a cationic polymer component and an anionic polymer component, and penetrates the front and back of the membrane and forms an ion channel present adjacent to each other. It is a film having. Through the ion channel, ions having a small molecular weight (atomic weight) (for example, alkali metal ions such as sodium and potassium) in the raw water move from the raw water tank side to the dialysis tank water side, and the raw water is desalted. The driving force for desalination of the membrane is the difference in salt concentration between the raw water and the dialysis tank water partitioned by the membrane, and the pressure difference applied to the raw water and the dialysis tank water. The membrane allows relatively low molecular weight salt ions in the raw water to be easily transferred into the dialysis tank water through the ion channels of the membrane. However, non-ionic substances in the raw water and high molecular weight molecules (for example, organic substances) ) Does not permeate, and the membrane can be used to easily separate salt ions and valuables in raw water. The mosaic charged membrane has been conventionally used for salt dialysis under normal pressure and salt dialysis under pressure (piezo salt dialysis) (desalting).

  In the present invention, as a large-sized mosaic charged film that can be used industrially, in particular, Japanese Patent No. 2868152, Japanese Patent No. 2895705, Japanese Patent No. 30112153, Japanese Patent No. 3234426, Japanese Patent No. 3236754, and Patent As disclosed in Japanese Patent No. 3156955, a mosaic charged membrane constituted by using a crosslinked granular polymer as at least one component of the charged polymer component is preferable.

In the description of the above publication, the evaluation of the salt dialysis characteristics of the mosaic charged membrane is performed as follows. First, a desalination apparatus using a mosaic charged membrane is configured. In the raw water tank, potassium chloride is adjusted to a concentration of 0.05 mol / l as an electrolyte, and glucose (molecular weight: 180) is concentrated to a concentration of 0.05 mol as a non-electrolyte. / L adjusted aqueous solution (corresponding to raw water). The dialysis water tank of the above device is filled with deionized water. In this state, the dialysis performance of the mosaic charged membrane is evaluated by allowing potassium chloride to move to the dialysis water tank by leaving it at normal pressure. The mosaic charged membrane exhibited excellent separation performance with respect to raw water containing potassium chloride and glucose, but the permeation flux of potassium chloride was 45 g / m ² h at the start of dialysis for 1 hour.

Therefore, in the present invention, when the dialysis characteristics of the mosaic charged membrane when the potassium chloride concentration in the raw water was increased 60 times (3 mol / l (about 20 mass%)), the permeation flux of potassium chloride was determined. , in start of dialysis 1 hour was 959g / m ² h, showed 714 g / m ² h at 4-5 hours. The relationship between the difference (mol / l) between the salt concentration of the raw water and the salt concentration of the dialysis tank water and the permeation flux (g / m ² h), which is a measure of the dialysis amount of the salt, was measured over time, When plotted with a log-log graph, the permeation flux and the salt concentration difference were almost aligned, indicating that a proportional relationship was established between the two. This indicates that the higher the salt concentration of the raw water and the greater the difference in salt concentration between the raw water and the dialysis tank water, the higher the dialysis speed.

  Therefore, the problems when the mosaic charged membrane is used in an industrial desalination method, that is, the problem that a large amount of fresh water is required as the dialysis tank water and the problem that the salt dialysis (desalination) takes a long time. It was found that the problem could be solved by increasing the salt concentration of the raw water. When increasing the salt concentration of the raw water, it is preferable to concentrate the raw water without altering solutes (for example, organic substances), which are valuables in the raw water. By concentrating the raw water, the volume of the raw water naturally decreases, the salt concentration of the raw water increases, and at the time of desalination, the permeation flux of the salt increases as described above. be able to.

  In addition, during desalination, during the intake of raw water, during transportation or storage, or during desalination, concentration or subsequent treatment, microorganisms such as bacteria are mixed into the raw water from the atmosphere or from manufacturing equipment, and the raw water is contaminated. In some cases, the microorganisms propagate in raw water. Normal raw water can be sterilized by chlorine sterilization, oxygen sterilization, or the addition of a germicide. However, when the raw water contains valuables (for example, organic substances) and the valuables are used, it is desirable that the raw water does not contain a germicide or the like that may alter the valuables.

  In the present invention, by increasing the salt concentration of the raw water by concentrating the raw water, it is possible to sterilize microorganisms such as bacteria mixed in the raw water without the sterilization treatment of the raw water or adding a bactericide or the like to the raw water as described above. Was found.

  In general, microorganisms such as bacteria have an environment suitable for growth and survival, and particularly at a salt concentration, there is a limit at which the microorganisms can survive or proliferate. If the salt concentration is increased, the growth of microorganisms such as bacteria is suppressed, and if the salt concentration is further increased, the microorganisms cannot survive. The limit of the salt concentration at which microorganisms can survive or proliferate depends on the type of microorganism such as bacteria and cannot be unconditionally specified, but in the case of salt water (raw water), the salt concentration of the salt water should be 10% by mass or more. Thus, the microorganisms that have invaded the salt water can be sufficiently killed. That is, in salt water having a high salt concentration, it is considered that the microorganisms such as bacteria are killed by extracting the water in the cells into the high concentration raw water due to the osmotic pressure difference between the outside of the cells and the microorganisms.

  When the raw water is seawater, particularly deep ocean water, microorganisms such as bacteria originally existing in the deep ocean water are present in a bacteriostatic state in the deep ocean water collected as raw water, and the microorganisms are in a saltwater environment. It is thought that it has acclimated to the saltwater, deep ocean water. Therefore, microorganisms can survive in the deep sea water having the above-mentioned salt concentration (10% by mass). Therefore, by increasing the salt concentration of the deep sea water to 15% by mass or 20% by mass, It has been found that microorganisms such as bacteria in deep water can be substantially killed. The salt concentration of the raw water on the premise of killing microorganisms such as bacteria is from 10% by mass to the saturated solubility of the salt, preferably from 15% by mass to the saturated solubility of the salt, more preferably from 20% by mass to the saturated solubility of the salt. Range. Thus, in the present invention, as described above, the deep sea water can be desalinated under aseptic conditions without using chlorine sterilization, disinfectants, bacteriostats and the like, and demineralized water containing valuables can be obtained. Further, if necessary, ultraviolet irradiation may be performed to thoroughly sterilize microorganisms.

Next, specific embodiments of the desalting method of the present invention will be described.
(A) The first step of concentrating the raw water by removing water from the raw water containing at least a water-soluble salt, and then removing the raw water concentrated in the first step under normal pressure or pressure using a mosaic charged membrane. Desalted water is obtained by performing the second step of salting. The first step and the second step may be performed only one cycle, or may be repeatedly performed many times. The concentration of the raw water can be performed using, for example, a reduced-pressure distillation apparatus such as a reverse osmosis membrane concentrator or a centrifugal thin-film vacuum distillation apparatus. In addition, water (eg, distilled water) obtained by concentrating raw water in the above method can be used as dialysis tank water during desalination, or adjustment of the salt concentration of valuable demineralized water or the concentration of valuables. Can be used for

  (B) As a pre-treatment for carrying out the method of the present invention, the salt concentration is reduced by desalinating raw water, particularly raw water containing 1% or more salt under normal pressure or pressure using a mosaic charged membrane. A step of preparing demineralized water, followed by removing water from the demineralized water using the demineralized water as raw water, performing a first step of concentrating the demineralized water, and then performing a second step to obtain demineralized water. Can be For example, when the deep sea water is used as raw water, the deep sea water is directly desalted using a mosaic charged membrane, and the obtained demineralized water is then concentrated using a reverse osmosis membrane or a vacuum distillation apparatus. Is carried out. By repeating this, it is possible to obtain demineralized water containing the valuables originally contained in the deep ocean water.

(C) "When the purpose is to concentrate valuables in raw water"
A step of extracting salt and water in the raw water out of the system by using a nanofiltration membrane from the raw water containing valuables to increase the concentration of the valuables in the raw water, and then mosaicing the raw water with the increased concentration of the valuables. By performing the step of desalination using a charged membrane, desalinated water having a low salt concentration and a high concentration of valuables can be obtained. For example, salt and water are separated from deep sea water by a nanofiltration membrane to obtain deep sea water with a high concentration of valuable substances, which is then desalinated with a mosaic charged membrane to have a high concentration of valuable substances and desalination. Deep sea water is obtained.

(D) "For the purpose of concentrating valuable resources in raw water"
A step of taking out salts and moisture in the raw water from the raw water (for example, deep sea water) containing the valuables with a nanofiltration membrane to increase the concentration of the valuables in the raw water, and then the concentration of the valuables Water and salt are taken out of the system while adding pure water to the raw water using a nanofiltration membrane using a nanofiltration membrane to obtain demineralized water having a high concentration of valuable substances and a low salt concentration.

(E) The demineralized water obtained by the above method or the demineralized water containing valuables is concentrated or diluted with fresh water to adjust the concentration of valuables, and the demineralized water containing valuables is removed. Obtainable.
Each of the above-mentioned methods A to E may be performed only in one cycle, or may be repeatedly performed a plurality of times.

  In the concentration step as the first step, a method of removing water by distillation or a method of separating water using a reverse osmosis membrane is used. As the distillation method, in addition to the atmospheric distillation method, the vacuum distillation method is preferable when the raw water to be distilled contains a substance sensitive to temperature. For example, rotary transfer such as a fixed-surface heat transfer type vacuum distillation apparatus such as a high-speed swirling type, a falling film type, a pumping and spraying type, and a scraping type, and a centrifugal-flow thin-film vacuum evaporator. A hot surface type vacuum distillation apparatus or the like is used. Known devices can be used for these, but as will be described later, when heating and concentrating raw water, the material of the device is selected in consideration of rust generation and corrosion of the device due to high-concentration raw water. It is necessary.

  As a desalting method using a mosaic charged membrane, a desalting dialysis method under normal pressure and a piezo desalting dialysis method using pressure are used. Various methods such as a batch (batch) method, a continuous method, a circulation method or a transient method, a counter flow method or a parallel flow method can be used as a method of contacting raw water and dialysis tank water in these methods. In these systems, when desalting raw water having a high salt concentration, instead of using fresh water (fresh water) as the dialysis tank water, fresh water used as the dialysis tank water is used by using salt water having a low salt concentration. Can be reduced.

  According to a desired design, the apparatus for producing demineralized water or demineralized water containing valuables according to the present invention includes a raw water storage tank, a pretreatment apparatus, a vacuum concentrator, a reverse osmosis membrane concentrator, a nanofiltration membrane concentrator, a mosaic charge It is selected from a membrane desalination device, an electrodialysis device, a dialysis salt water receiving tank, a dialysis fresh water receiving tank, a deionized water receiving tank, etc., and a group of equipment attached thereto, and is configured in combination.

  The material used for each device is a device or a member that comes into contact with high-concentration salt water in the evaporative concentration process such as a centrifugal thin-film vacuum distillation device, for example, a heat exchanger for heating salt water, and a surface of a salt water evaporator. It is necessary to pay attention to rust and corrosion due to salt water, as in the case of pipes and piping. Preferred as these materials are SUS316L, NAS354N (high nickel austenitic stainless steel), Hastelloy C-22 (nickel-chromium-molybdenum alloy), titanium and glass (glass lining).

  The desalination method and desalination apparatus of the present invention can be used, for example, in drinking water, pure water, ultrapure water, desalination of various types of salt water in the water treatment industry such as industrial water, biochemical related industries such as fermentation industry and food industry. It is useful for desalination of various kinds of salt water generated, desalination of pharmaceutical raw materials containing salts, desalination of industrial wastewater containing salts in the chemical industry, metal industry, etc., and desalination of dyes and pigments containing salts in the pigment manufacturing industry. is there.

  In particular, the desalination method using a mosaic charged membrane used in the present invention does not heat the raw water and does not generate heat at the time of desalination. It is useful for desalination of various types of salt water in the food and fermentation industries, which are easily affected. When such salt water is desalted by using a conventional electrodialysis method, valuable resources (target substances) are decomposed or deteriorate due to heat generated during the treatment. In addition, in desalination using an ion exchange membrane, there is a problem that the ion exchange membrane is contaminated by ionic adsorption. According to the present invention, the above-mentioned problems of the prior art are solved.

  Deep sea water containing valuables and valuable minerals is said to be effective against eosinophils that increase during atopic dermatitis and allergic reactions, and also has a physiological activity on fibroblasts and It is said that the moisturizing and antibacterial functions are also effective. Such effectiveness is described in the 1998 Kochi Prefectural Industrial Promotion Center's Science and Technology Comprehensive Research Outsourcing Area Leading Research Research Results Report, "Characterization and Function Elucidation of Muroto Deep Ocean Water" (March 1999) ), And the 1998-2012 Science and Technology Comprehensive Research Outsourcing Regional Leadership Research Results Report, "Grading the Characteristics and Functions of Muroto Deep Sea Water for the Three Years" (March 2001) The desalinated water containing valuables derived from deep sea water obtained by the method of the present invention, particularly the concentrated water thereof, is particularly suitable for moist water, poultice for healing damaged skin cells such as skin diseases, skin defects, and skin defects. It is effective as a liquid, an impregnating liquid for a gel patch, and a culture liquid component of a culture skin medium.

The most specific embodiments of the present invention are as follows, but the present invention is not limited to the following embodiments.
(1) a step of concentrating the deep sea water by distillation under reduced pressure until the salt concentration becomes 10% by mass to the saturated solubility of the salt, and the concentrated deep sea water is concentrated until the salt concentration becomes 0.5 to 12% by mass. A step of desalting with a mosaic charged membrane, a step of reconcentrating the demineralized water by distillation under reduced pressure until the salt concentration reaches 10% by mass to a saturated solubility of salt, and a step of concentrating the concentrated deep sea water with a salt concentration of 0.1%. A method for desalinating deep ocean water, comprising the step of desalinating again with a mosaic charged membrane until the water content reaches 1.0% by mass.

(2) a step of concentrating the deep sea water with a reverse osmosis membrane until the salt concentration becomes 5 to 7% by mass, and reducing the concentrated deep sea water until the salt concentration becomes 10% by mass to the saturated solubility of salt. A method for desalinating deep sea water comprising the steps of further concentrating by distillation and desalting the concentrated water with a mosaic charged membrane until the salt concentration becomes 0.1 to 1.0% by mass. (3) a step of concentrating the deep ocean water by a nanofiltration membrane until the volume becomes 1/5 to 1/50, and a step wherein the concentrated deep ocean water has a salt concentration of 0.1 to 1.0. A method for desalinating deep sea water, comprising the step of desalting with a mosaic charged membrane until the amount of the salt reaches mass%.
In addition, each process in each of the above-described exemplary embodiments can be repeated twice or more as necessary.

Next, the present invention will be described more specifically with reference to examples. Note that “parts” and “%” in the text are based on mass unless otherwise specified.
Example 1
(1) Structure of desalination equipment for raw water containing valuables Water for raw water storage tanks, pretreatment equipment, vacuum distillation concentrators, distilled fresh water receiving tanks, salt water receiving tanks, mosaic charged membrane desalination equipment, desalinated water receiving tanks, dialysis water tanks A desalination device was constructed by installing a storage tank, a dialysis water receiving tank, and equipment attached to them.

(2) Concentration of Deep Ocean Water by Vacuum Distillation A centrifugal thin-film vacuum distillation apparatus was used as a vacuum distillation apparatus. This apparatus has a rotary evaporating face plate using SUS316L as an evaporator, and by rotating the evaporating face plate at high speed, the deep sea water discharged from the central pipe is thinned by centrifugal force and evaporated. . 2,000 kg of deep sea water (salt concentration: about 3.5%) as raw water was charged into the above-mentioned vacuum distillation apparatus, the pressure inside the apparatus was reduced to about 4 kPa, and vacuum distillation was performed at about 30 ° C to 40 ° C. The distillation was carried out until the liquid volume was reduced to approximately one third, 700 kg. The salt concentration of the obtained concentrated raw water (concentrated liquid) was approximately 10%. The amount of distilled water (fresh water) collected was about 1,300 kg. The total organic carbon (TOC) value in the concentrate was measured. The TOC value of the concentrated water was 2.9 ppm, while the TOC value of the raw water before concentration was 1 ppm.

(3) Desalination of concentrated deep seawater (concentrated raw water) using a mosaic charged membrane A flat membrane type mosaic charged membrane desalination apparatus was prepared. A raw water tank containing raw water and a dialysis water tank containing dialysis water are alternately arranged, and a total of 100 flat membrane mosaic charged membranes each having an effective desalination area of 0.1 m ² are provided between each raw water tank and each dialysis water tank. It was fixed by packing. Each raw water tank and each dialysis water tank are connected in parallel, and the raw water pumped from the raw water storage tank and the dialysis water pumped from the dialysis water storage tank are respectively connected to the plurality of raw water tanks and the plural The piping was circulated between the dialysis water tanks. The raw water tank was charged with 700 kg of the 10% salt concentration concentrate obtained in (2) above as raw water. The above-mentioned dialysis water tank was filled with deionized water and circulated to carry out desalination. The change in the salt concentration of the raw water was monitored by measuring the change in the electric conductivity of the raw water. Desalting was performed until the salt concentration of the raw water became approximately 2%. At this time, the TOC value in the dialysis bath water was 0 ppm, and organic valuables in the raw water were hardly dialyzed.

  In addition, the preparation of the mosaic charged film used above was performed as follows based on the description of JP-A-2000-309654. 4-vinylpyridine: divinylbenzene (molar ratio: 10: 1) cross-linked copolymer (average particle diameter: about 350 nm) as a cationic microgel, and styrene: acrylonitrile: hydroxyethyl methacrylate: divinylbenzene (molar ratio: 41) as an anionic microgel. .6: 7.1: 8.1: 8.7) A soda salt of a sulfonated cross-linked copolymer (average particle size: about 240 nm) was prepared. A coating liquid containing the above-mentioned cationic microgel, the above-mentioned anionic microgel, and a separately prepared hydrogenated acrylonitrile-butadiene resin composition (mass ratio 3: 7: 10) was coated so that the dry film thickness became about 30 μm. The polyester non-woven fabric is uniformly coated and dried on a polyester non-woven fabric, and then left in a methyl iodide atmosphere, and the pyridine unit of 4-vinylpyridine is converted to a quaternary pyridinium salt unit. To obtain a mosaic charged membrane reinforced with.

(4) Secondary concentration by vacuum distillation and secondary desalination by mosaic charged membrane 700 kg of the salt water having a salt concentration of 2% obtained in the above (3) is charged into a vacuum distillation apparatus, and vacuum distillation is performed in the same manner as in the above (2). To perform secondary concentration. The distillation was performed until the liquid volume was reduced to approximately 1/5, that is, 140 kg. The obtained concentrate had a salt concentration of about 10%. Next, secondary desalination was performed using a mosaic charged membrane desalination apparatus in the same manner as in (3) above. The secondary desalting was performed until the salt concentration of the raw water became 0.28%. The TOC value of the demineralized water showed a value of approximately 14 ppm. The TOC value in the dialysis tank water at the time of desalting showed a value of 1 to 0 ppm. The amount of demineralized water finally obtained was 14.3 times less than the original deep sea water, which is raw water.

(5) Adjustment of concentration ratio by water dilution To 140 kg of demineralized water having a salt concentration of 0.28% obtained in (4) above, 60 kg of distilled water derived from deep sea water obtained in (2) above was added for dilution. did. The diluent has a salt concentration of 0.2%, and contains about 10 ppm of TOC value of a soluble valuable material exhibiting effective physiological activity.

(6) Concentration of dialysis tank water Further, the dialysis tank water used in the mosaic charged membrane desalination apparatus of (3) (the dialysis tank water contains salts desalted from raw water) is further electrodialyzed. Concentration was performed using an apparatus or a concentrator to obtain salt water and salt derived from deep sea water.

Example 2
(1) Structure of desalination equipment for raw water containing valuables Water for raw water storage tanks, pretreatment equipment, vacuum distillation concentrators, distilled fresh water receiving tanks, salt water receiving tanks, mosaic charged membrane desalination equipment, desalinated water receiving tanks, dialysis water tanks A storage tank, a dialysis water receiving tank, an ultraviolet irradiation sterilizer and equipment attached thereto were installed and configured.

(2) Concentration by vacuum distillation of deep sea water The same apparatus as in Example 1 was used as a vacuum distillation apparatus. As a raw water, 2,000 kg of deep-sea water was charged into a vacuum distillation apparatus, the pressure in the apparatus was reduced to about 4 kPa, and vacuum distillation was performed at about 30 ° C to 40 ° C. Distillation was performed until the liquid amount was reduced to about ８ of 269 kg. The salt concentration of the liquid concentrated by distillation was approximately 26%. The amount of distilled water (fresh water) collected was about 1,731 kg. The TOC value of the concentrated water was 7.4 ppm. The viable cell count in the concentrated water was measured to be substantially zero.

(3) Desalination of Concentrated Deep Ocean Water by Mosaic Charged Membrane The same flat membrane type mosaic charged membrane desalination apparatus as in Example 1 was used. The raw water tank was charged with 269 kg of deep sea water having a salt concentration of 26% obtained in (2) above as raw water to be desalted. Distilled water sterilized by irradiation with ultraviolet light was put into the dialysis water tank, and the distilled water was continuously flowed to desalinate. Desalination was performed until the salt concentration of the raw water became approximately 12%.

(4) Secondary Concentration by Vacuum Distillation and Secondary Desalination by Mosaic Charged Membrane 269 kg of the salt water having a salt concentration of 12% obtained in the above (3) is charged into a vacuum distillation apparatus, and the pressure is reduced in the same manner as in the above (2). A second concentration was performed by distillation. The distillation was carried out until the liquid volume was almost halved to 124 kg. The salt concentration of the obtained concentrate was approximately 26%. The viable cell count in the secondary concentrated water was measured to be substantially zero. Next, secondary desalination was performed using a mosaic charged membrane desalination apparatus in the same manner as in (3) above. Secondary desalting was performed until the salt concentration of the liquid reached 0.80%. The TOC value of the demineralized water showed a value of approximately 16 ppm. In addition, the liquid volume after the desalination was reduced to 16.1 times the depth of the deep sea water as raw water.

(5) Adjustment of Concentration Ratio by Water Dilution 76 kg of distilled water derived from deep sea water obtained in the above (2) is irradiated with ultraviolet rays to 124 kg of the demineralized water having a salt concentration of 0.80% obtained in the above (4). After sterilization, the desalted water was diluted. The diluent contains about 10 ppm of TOC value of valuable substances exhibiting effective physiological activity at a salt concentration of 0.5%. The viable cell count in the deionized water containing this valuable material was substantially zero when measured.

Example 3
(1) Configuration of the desalination device for raw water containing valuables Raw water storage tank, pretreatment device, reverse osmosis membrane device, reverse osmosis salt water receiver, reverse osmosis dialysis fresh water receiver, vacuum distillation concentrator, distilled fresh water receiver, salt water receiver, A mosaic charged membrane desalination apparatus, a desalinated water receiving tank, a water storage tank for a dialysis water tank, a dialysis water receiving tank, and equipment attached thereto were installed.

(2) Concentration of Deep Ocean Water by Reverse Osmosis Membrane A reverse osmosis membrane device was used as a concentration device, and 4,000 kg of deep sea water was concentrated at a pressure of 60 kg / cm ² . Concentration was performed until the liquid volume was almost halved to 2,000 kg. The salt concentration of the concentrate was approximately 7%. The amount of fresh water collected during this concentration was about 2,000 kg.

(3) Secondary concentration by distillation under reduced pressure The secondary concentration of the concentrated solution obtained in the above (2) was performed using a centrifugal thin-film vacuum distillation apparatus as in Example 1 (2). The secondary concentration was performed until the liquid volume was reduced to approximately one third, that is, 700 kg. The salt concentration of the concentrate was approximately 20%. The amount of distilled water collected was about 1,300 kg.

(4) Desalination of Concentrated Deep Ocean Water by Mosaic Charged Membrane Desalination of the concentrated solution obtained in the above (3) was performed using a mosaic charged membrane desalination apparatus in the same manner as in Example 1 (3).

(5) Secondary concentration by vacuum distillation and secondary desalination by mosaic charged membrane The secondary concentration of the demineralized water obtained in the above (4) was performed by using a centrifugal thin-film vacuum distillation apparatus as in Example 1 (2). The secondary desalination was performed using a mosaic charged membrane desalination apparatus in the same manner as in Example 1 (3).

(6) Adjustment of Concentration Ratio by Dilution with Water The desalinated water obtained in the above (5) was prepared in the same manner as in Example 1 (5) in accordance with the desired concentration ratio, salt concentration, or valuables concentration. Distilled water derived from deep sea water obtained in 2) or 3) was added for dilution.

Example 4
(1) Configuration of desalination equipment for raw water containing valuables Raw water storage tank, pretreatment equipment, nanofiltration membrane equipment, nanofiltration permeated water receiving tank, mosaic charged membrane desalination equipment, desalinated water receiving tank, dialysis water tank A water storage tank for dialysis, a dialysis water receiving tank, and equipment attached to them are installed and configured.

(2) Desalination and concentration of deep ocean water by nanofiltration membrane Using a nanofiltration membrane device, 2,000 kg of deep ocean water as raw water is desalted and concentrated at a pressure of 20 kg / cm ² . Was. Desalting and concentration were performed until the liquid volume of the raw water reached 100 kg, which was approximately 1/20. The salt concentration of the concentrate was approximately 4%.

(3) Desalination of concentrated deep seawater by mosaic charged membrane Desalination of the concentrated solution obtained in the above (2) is performed by a mosaic charged membrane desalination apparatus in the same manner as in Example 1 (3), and demineralized water is removed. Obtained.

(4) Adjustment of Concentration Ratio by Water Dilution The desalinated water obtained in the above (3) was treated with marine water in the same manner as in Example 1 (5) so that the desired concentration ratio, salt concentration, or valuable substance concentration was obtained. It was diluted by adding fresh water derived from deep water. Instead of the fresh water, the nanofiltration permeated salt water obtained in the above (2), the centrifugal thin-film vacuum distillation apparatus of Example 1 (4) or the reverse osmosis membrane apparatus of Example 3 (2) was used. Freshwater derived from deep seawater obtained by permeation can also be used.

The industrial applicability of the present invention is as follows.
(1) Desalination of raw water can be performed industrially and economically.
(2) In a desalination method using a mosaic charged membrane, the amount of dialysis tank water used is small and the desalination time can be shortened. Further, water obtained at the time of concentration can be used as dialysis tank water.
(3) In the desalination of raw water containing valuables, it is possible to desalinate the valuables in the raw water without spoiling them.

Claims (15)

  At least comprising a first step of removing water from raw water containing at least a water-soluble salt and concentrating the raw water, and a second step of removing at least a part of a water-soluble salt from the concentrated raw water. A method for desalting raw water as described above.   The desalination method according to claim 1, wherein the first step and the second step are performed simultaneously.   The desalination method according to claim 1, wherein the raw water contains at least one kind of alkali metal ion or alkaline earth metal ion.   The desalination method according to claim 1, wherein a salt concentration of the concentrated raw water ranges from 10% by mass to a saturated solubility of the salt.   The desalination method according to claim 1, wherein the first step is performed using a distillation and / or reverse osmosis membrane.   The desalination method according to claim 1, wherein the second step is performed using a mosaic charged membrane.   The desalination method according to claim 2, wherein the first step and the second step are simultaneously performed using a nanofiltration membrane.   The desalination method according to claim 1, wherein the raw water contains a valuable resource.   The desalination method according to claim 1, wherein the raw water is seawater or deep sea water.   A step of concentrating the deep ocean water by distillation under reduced pressure until the salt concentration becomes 10% by mass to the saturated solubility of the salt, and a mosaic charged membrane until the concentrated deep ocean water has a salt concentration of 0.5 to 12% by mass. , The step of concentrating the demineralized water by vacuum distillation until the salt concentration reaches 10% by mass to the saturated solubility of the salt, and the step of concentrating the concentrated deep sea water with a salt concentration of 0.1 to 1.0. A method for desalinating deep ocean water, comprising the step of desalinating to a mass% by a mosaic charged membrane.   A step of concentrating the deep ocean water by a reverse osmosis membrane until the salt concentration becomes 5 to 7% by mass; further, the concentrated deep sea water is subjected to vacuum distillation until the salt concentration becomes 10% by mass to the saturated solubility of the salt. A method for desalinating deep sea water, comprising a step of concentrating and a step of desalinating the concentrated water with a mosaic charged membrane until the salt concentration becomes 0.1 to 1.0% by mass.   A step of concentrating the deep sea water by a nanofiltration membrane until the volume becomes 1/5 to 1/50, and reducing the concentrated deep sea water to a salt concentration of 0.1 to 1.0% by mass. A method for desalination of deep ocean water, comprising a step of desalination by using a mosaic charged membrane until the time comes.   13. Demineralized water obtained by the method according to any one of claims 1 to 12.   A desalination apparatus comprising a combination of at least one concentration apparatus selected from a vacuum distillation apparatus, an atmospheric distillation apparatus, a reverse osmosis membrane apparatus, and a nanofiltration membrane apparatus, and a mosaic charged membrane desalination apparatus.   15. The vacuum distillation apparatus according to claim 14, wherein the vacuum distillation apparatus is selected from a centrifugal thin film vacuum distillation apparatus, a rotary heat transfer surface vacuum distillation apparatus, a high-speed rotary vacuum distillation apparatus, a falling film vacuum distillation apparatus, and a scratch surface vacuum distillation apparatus. Desalination equipment.