Water treatment system

Abstract

We provide a water treatment system that can reduce running costs. [Solution] The water treatment system comprises an electrodialysis apparatus that generates treated water by performing electrodialysis on water to be treated, and a recovery unit that recovers the target material from the treated water, wherein the electrodialysis apparatus comprises an anode and a cathode provided opposite each other, and a plurality of membranes disposed between the anode and the cathode, and a portion of the plurality of membranes includes a first layer having separation performance and a second layer that supports the first layer and does not have separation performance.

Description

Technical Field

[0001] The present disclosure relates to a water treatment system.

Background Art

[0002] As a method for recovering valuable substances such as metals from seawater and the like, a water treatment system using electrodialysis (ED) as shown in Patent Document 1 and Patent Document 2 is known. Patent Document 2 discloses a water treatment system including an electrodialysis device having a stack structure in which either a cation exchange membrane or an anion exchange membrane is replaced with a nanofiltration membrane, that is, an electrodialysis device incorporating a nanofiltration membrane (EDNF).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the electrodialysis device incorporating a nanofiltration membrane, although the initial cost is reduced, there is a problem that the running cost cannot be reduced as expected. Therefore, a technology that enables the recovery of valuable substances at a lower cost has been demanded.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a water treatment system capable of reducing the running cost.

Means for Solving the Problems

[0006] When the inventor investigated the reason why the running costs were not decreasing, he found that although the support layer of the nanofiltration membrane does not contribute to the separation performance, the high resistance of this support layer was causing the electricity costs to be high. To solve the above problems, the water treatment system according to the present disclosure comprises an electrodialysis apparatus that generates treated water by performing electrodialysis on water to be treated, and a recovery unit that recovers the target material from the treated water, wherein the electrodialysis apparatus comprises an anode and a cathode provided opposite each other, and a plurality of membranes disposed between the anode and the cathode, and a portion of the plurality of membranes includes a first layer having separation performance and a second layer that supports the first layer and does not have separation performance. [Effects of the Invention]

[0007] The electrodialysis apparatus and water treatment system disclosed herein can reduce running costs. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram representing the entire water treatment system according to the present disclosure. [Figure 2] This is an enlarged schematic diagram of a part of the water treatment system according to the embodiment of this disclosure. [Figure 3] This is a schematic diagram of a second film according to the first embodiment of the present disclosure. [Figure 4] This is a schematic diagram of a second film according to the second embodiment of the present disclosure. [Figure 5] This is a schematic diagram of the second layer according to the third embodiment of this disclosure. [Modes for carrying out the invention]

[0009] <First Embodiment> Hereinafter, the water treatment system 1 according to the first embodiment of this disclosure will be described in detail with reference to Figures 1 to 3.

[0010] <Water Treatment System> In this embodiment, the water treatment system 1 is described as a system that separates seawater (introduced water) into concentrated water (water to be treated) and fresh water using a reverse osmosis membrane (RO membrane) to produce fresh water, and further separates the concentrated water into highly concentrated water and desalinated water by electrodialysis (ED), and recovers valuable metals by evaporating the highly concentrated water and precipitating it.

[0011] As shown in Figure 1, the water treatment system 1 of this embodiment includes a water treatment introduction section 10, a reverse osmosis membrane device 20, an electrodialysis device 30, a recovery section 70, and a flow pipe 80. The flow pipe 80 is a channel through which various fluids can flow. The fluids that flow are not limited in form, but examples include concentrated water and fresh water. The flow pipe 80 includes a water supply pipe 81, a concentrated water pipe 82, a permeate water pipe 83, a highly concentrated water pipe 84, a desalination water pipe 85, a return water pipe 86, a discharge pipe 87, and an evaporation water pipe 88. Further explanations of the flow pipe 80 will be provided below as appropriate.

[0012] <Water to be treated introduction section> The water to be treated introduction section 10 is provided to allow the introduction water to be treated by the water treatment system 1 to flow through it. The water to be treated introduction section 10 in this embodiment may include a pretreatment device (not shown). The pretreatment device is provided to suppress deterioration of the water permeability performance of the reverse osmosis membrane device 20. The pretreatment device can remove suspended matter such as fine particles and colloids, and microorganisms such as algae and shellfish from seawater. The pretreatment device may be configured to perform other types of pretreatment. The water to be treated introduction section 10 is connected to a water supply pipe 81 through which the introduction water can flow to the reverse osmosis membrane device 20.

[0013] <Reverse osmosis membrane device> The reverse osmosis membrane device 20 is configured to include, for example, a plurality of reverse osmosis membrane elements (reverse osmosis membrane modules) in a container. The reverse osmosis membrane device 20 can treat the introduced water by reverse osmosis. The reverse osmosis membrane device 20 can separate the introduced water into concentrated water (water to be treated) and fresh water. The reverse osmosis membrane device 20 is connected to a concentrated water pipe 82 and a permeated water pipe 83. The concentrated water pipe 82 is configured to allow the concentrated water to flow into the electrodialysis device 30. The permeated water pipe 83 is configured to allow the fresh water to flow. The permeated water pipe 83 is configured to be able to discharge, for example, the fresh water to the outside of the water treatment system 1.

[0014] <Electrodialysis device> The electrodialysis device 30 is capable of separating ions in the concentrated water. As shown in FIG. 2, the electrodialysis device 30 includes an electrodialysis cell 31, an anode 32, a cathode 33, and a plurality of membranes 40. In the electrodialysis cell 31, the anode 32, the cathode 33, and a plurality of membranes 40 are arranged inside. The anode 32 and the cathode 33 are arranged opposite to each other. The anode 32 and the cathode 33 can apply a DC voltage inside the electrodialysis cell 31.

[0015] <Membrane> The membrane 40 is arranged between the anode 32 and the cathode 33. The membrane 40 is a membrane having ion separation performance. The membrane 40 of the present embodiment has a first membrane 41 and a second membrane 42. The first membrane 41 and the second membrane 42 are arranged at intervals from each other. Further, the first membrane 41 and the second membrane 42 are alternately arranged between the anode 32 and the cathode 33. In other words, the second membrane 42 is alternately arranged at intervals from the first membrane 41.

[0016] <First membrane> The first membrane 41 of the present embodiment is a cation exchange membrane. That is, the first membrane 41 allows cations to permeate regardless of valence and does not allow anions to permeate. Note that the first membrane 41 may have valence selectivity. Also, the term "permeable (impermeable)" as related to the present disclosure is not necessarily limited to that all objects must be permeable (impermeable). That is, in the present disclosure, it is expressed as "permeable" when a specific object is likely to be permeable, and "impermeable" when it is difficult for the object to be permeable. For example, the first film 41 according to the present embodiment is likely to permeate cations and difficult to permeate anions, but in some cases, a part of the anions may permeate.

[0017] <Second film> The second film 42 of the present embodiment is a nanofiltration membrane (NF membrane). That is, the second film 42 is only permeable to monovalent ions. Also, the second film 42 has no selectivity between cations and anions. In this way, the second film 42 is capable of separating monovalent ions from polyvalent ions. Note that the second film 42 may have selectivity between cations and anions. As shown in FIG. 3, the second film 42 of the present embodiment has a first layer 43 and a second layer 44.

[0018] <First layer> The first layer 43 has ion separation performance. The first layer 43 is capable of separating monovalent ions from polyvalent ions. That is, the first layer 43 is configured to permeate monovalent ions and not permeate polyvalent ions. The first layer 43 is connected to the second layer 44 and integrated. In the state of being disposed inside the electrodialysis cell 31, the position of the second layer 44 with respect to the first layer 43 is not limited to one side. Also, the first layer 43 is, for example, made of polyamide, but is not limited thereto.

[0019] <Second layer> The second layer 44 is provided to support the first layer 43. The second layer 44 has no ion separation performance. The second layer 44 of the present embodiment has a support layer 50 and a base material layer 51. The support layer 50 is provided to support the first layer 43. The support layer 50 does not have ion separation capabilities. The support layer 50 is provided to allow ions and the like that selected and permeated through the first layer 43 to pass through. The support layer 50 is provided so as to be sandwiched between the first layer 43 and the substrate layer 51. The support layer 50 is made of, for example, polysulfone, but is not limited thereto.

[0020] The base layer 51 is provided to improve the pressure resistance performance of the second film 42. The base layer 51 does not have ion separation properties. The base layer 51 is provided to allow ions selected and permeated through the first layer 43 to pass through. The base layer 51 is provided together with the first layer 43 to sandwich the support layer 50. The base layer 51 is, for example, a nonwoven fabric made of polyester, but is not limited thereto.

[0021] The second layer 44 is preferably 75 micrometers or less in thickness. That is, the combined thickness of the support layer 50 and the base layer 51 is preferably 75 micrometers or less. In other words, the second layer 44 is preferably 0 to 75 micrometers in thickness. More preferably 6 to 45 micrometers, and even more preferably 6 to 15 micrometers. The thicknesses of the support layer 50 and the base layer 51 are not limited. For example, when the thickness of the support layer 50 is 45 micrometers, the thickness of the base layer 51 is preferably 30 micrometers or less. Furthermore, the second membrane 42 preferably has an electrical resistance of 7 Ω·cm² or less in a 0.5 mol / L aqueous sodium chloride solution.

[0022] <Detailed Configuration of Electrodialysis Machine> As shown in Figure 2, the electrodialysis apparatus 30 has a concentration chamber 34 and a dilution chamber 35 formed by alternatingly arranged first membranes 41 and second membranes 42. The concentration chamber 34 and the dilution chamber 35 are adjacent to each other via either the first membrane 41 or the second membrane 42.

[0023] In the concentration chamber 34, cations that have permeated through the first membrane 41, which is a cation exchange membrane, can flow in from the adjacent dilution chamber 35. Examples of cations include sodium ions, potassium ions, calcium ions, and magnesium ions. Furthermore, ions that have permeated through the second membrane 42, which is a nanofiltration membrane, can flow into the concentration chamber 34 from the adjacent dilution chamber 35 on the opposite side. An example of an ion that flows into the concentration chamber 34 after permeating through the second membrane 42 is the monovalent ion, chloride ion.

[0024] A highly concentrated water pipe 84 is connected to the concentration chamber 34. The highly concentrated water produced by concentration in the concentration chamber 34 can be circulated to the recovery unit 70 via the highly concentrated water pipe 84. The highly concentrated water pipe 84 may also be branched to allow highly concentrated water to flow into the concentration chamber 34.

[0025] A concentrated water pipe 82 is connected to the dilution chamber 35. That is, concentrated water produced by the reverse osmosis membrane device 20 can flow into the dilution chamber 35. Various ions are permeated from the concentrated water flowing into the dilution chamber 35 to the adjacent concentration chamber 34, where it is desalinated. In other words, the concentrated water is desalinated to produce desalinated water. At this time, sulfate ions contained in the concentrated water remain in the desalinated water because they cannot permeate the second membrane 42. In addition, some ions that can permeate membrane 40 also remain in the desalinated water.

[0026] The desalination water can be discharged through the desalination water pipe 85. The desalination water pipe 85 is capable of circulating to the recovery unit 70. However, the desalination water pipe 85 may not be connected to the recovery unit 70. For example, the desalination water pipe 85 may be capable of discharging the desalination water to the outside of the water treatment system 1. In this embodiment, an example is given in which the desalination water pipe 85 is connected to the valuable material recovery unit 72, which is the recovery unit 70.

[0027] Hereinafter, the highly concentrated water and desalinated water supplied to the recovery unit 70 will be referred to as treated water. That is, the treated water generated in the electrodialysis unit 30 is distributed to the recovery unit 70.

[0028] <Collection Department> The recovery unit 70 is configured to recover the target substance (desired solute) from the treated water. That is, the recovery unit 70 can recover the target substance from the supplied highly concentrated water and desalinated water. The recovery unit 70 in this embodiment has a metal recovery unit 71 and a valuable substance recovery unit 72.

[0029] <Metal Recycling Department> The metal recovery unit 71 is connected to a highly concentrated water pipe 84. That is, highly concentrated water can flow into the metal recovery unit 71. The metal recovery unit 71 can process the highly concentrated water and recover the target material. The metal recovery unit 71 of this embodiment exemplifies a case where the target material is obtained by evaporating the highly concentrated water. However, the method of processing the highly concentrated water is not limited to this. The metal recovery unit 71 of this embodiment evaporates the water from the highly concentrated water. The metal recovery unit 71 also includes a part that recovers the target material from the highly concentrated water from which the water has been evaporated. The metal recovery unit 71 of this embodiment can recover, for example, magnesium, sodium, calcium, potassium, and the like.

[0030] The metal recovery section 71 is connected to an evaporation pipe 88 and a discharge pipe 87. The evaporation pipe 88 is capable of carrying water evaporated in the metal recovery section 71. The evaporation pipe 88 is connected to a permeate pipe 83. That is, the evaporation pipe 88 is capable of carrying evaporated water to the permeate pipe 83. The evaporation pipe 88 is capable of discharging the liquid from which the target material has been recovered in the metal recovery section 71 to the outside of the water treatment system 1.

[0031] <Recyclable Materials Collection Department> The valuable materials recovery unit 72 is connected to the demineralized water pipe 85. That is, the valuable materials recovery unit 72 is capable of receiving the demineralized water pipe 85. The valuable materials recovery unit 72 can process the demineralized water and recover the target materials. The valuable materials recovery unit 72 is configured to recover the target materials by means of adsorption, ion exchange, etc. In this embodiment, the valuable materials recovery unit 72 can recover sulfur as sulfate ions, etc.

[0032] A return water pipe 86 is connected to the valuable materials recovery unit 72. The return water pipe 86 can circulate the liquid from which the valuable materials have been recovered in the valuable materials recovery unit 72. The return water pipe 86 is connected to the water supply pipe 81. In other words, the return water pipe 86 can circulate the liquid from which the valuable materials have been recovered to the water supply pipe 81.

[0033] <Effects and Effects> In the water treatment system 1 described above, the concentrated water to be treated is treated by the electrodialysis unit 30. The electrodialysis unit 30 discharges highly concentrated water in which cations and monovalent anions are concentrated. The electrodialysis unit 30 also discharges desalinated water in which divalent or greater anions remain and cations and monovalent anions are reduced. The treated water (highly concentrated water and desalinated water) is recovered by the recovery unit 70 to recover the target material.

[0034] The electrodialysis apparatus 30 of this embodiment has a first membrane 41 which is a cation exchange membrane and a second membrane 42 which is a nanofiltration membrane. The second membrane 42 of this embodiment does not have selectivity for cations and anions, but is configured to substantially allow monovalent anions to pass through due to the balance of ions in the concentration chamber 34 and the dilution chamber 35, respectively. Since nanofiltration membranes are generally less expensive than cation exchange membranes and anion exchange membranes, this configuration can reduce the manufacturing cost of the electrodialysis apparatus 30. Therefore, the manufacturing cost of the water treatment system 1 can be reduced.

[0035] Furthermore, the second membrane 42 of this embodiment has a first layer 43 that has ion separation performance and a second layer 44 that does not have ion separation performance. The second layer 44 has a support layer 50 and a base layer 51. The second layer 44 can improve the pressure resistance performance of the second membrane 42, which is a nanofiltration membrane, and facilitate handling in the manufacture and maintenance of the electrodialysis machine 30. On the other hand, the second layer 44 increases the electrical resistance of the second membrane 42. According to this embodiment, the electrical resistance of the second membrane 42 can be reduced by making the second layer 44 thin (for example, 75 nanometers or less). Therefore, the power consumption of the electrodialysis machine 30 can be reduced. Therefore, the running cost of the water treatment system 1 can be reduced.

[0036] Furthermore, the base layer 51 in this embodiment is a nonwoven fabric made of polyester. The base layer 51 supports the first layer 43 and improves the pressure resistance performance of the second membrane 42. On the other hand, because the base layer 51 is made of a nonwoven fabric, it leaks the treated water to the outside of the electrodialysis apparatus 30. In this embodiment, by making the thickness of the second layer 44 thin (for example, 75 nanometers or less), it is possible to reduce leakage of the treated water to the outside while ensuring ease of handling of the second membrane 42. Therefore, it is possible to reduce the amount of treated water processed per unit amount of valuable material recovered. Accordingly, according to this embodiment, it is possible to reduce the processing amount per unit amount of valuable material recovered while reducing running costs.

[0037] Furthermore, the first layer 43 of this embodiment has the ability to separate monovalent ions selectively. As a result, polyvalent anions remain in the desalinated water of this embodiment. In this embodiment, for example, sulfate ions remain in the desalinated water. By treating this desalinated water, sulfate ions can be separated from other ions contained in seawater and recovered.

[0038] <Second Embodiment> Next, a second embodiment will be described with reference to Figure 4. In the second embodiment, components similar to those in the first embodiment are denoted by the same reference numerals, and detailed descriptions are omitted.

[0039] The water treatment system 1A and electrodialysis apparatus 30A of the second embodiment differ from the first embodiment in the configuration of the second membrane 42A. As shown in Figure 4, the second membrane 42A of the second embodiment does not include a base layer 51 in the second layer 44A. That is, the second layer 44A of the second embodiment does not have a base layer 51, but has a support layer 50. The support layer 50 of the second embodiment is the same as that of the first embodiment. The second layer 44A, i.e., the support layer 50 of the second embodiment, preferably has a thickness of 75 micrometers or less. The support layer 50 preferably has a thickness of 0 to 75 micrometers, more preferably 6 to 45 micrometers, and even more preferably 6 to 15 micrometers. Furthermore, the second membrane 42A preferably has an electrical resistance of 7 Ω·cm² or less in a 0.5 mol / L aqueous sodium chloride solution.

[0040] <Effects and Effects> In the water treatment system 1A and electrodialysis apparatus 30A according to the second embodiment, the second layer 44A does not have the base material layer 51 according to the first embodiment. That is, the second layer 44A does not have a structure such as a nonwoven fabric made of polyester. Therefore, leakage of treated water to the outside can be further reduced. In addition, the electrical resistance value of the second membrane 42A can be further reduced. Therefore, the water treatment system 1A can further reduce the processing amount per unit of recovered valuable material while further reducing running costs.

[0041] <Third Embodiment> Next, a third embodiment will be described with reference to Figure 5. In the third embodiment, the same reference numerals are used for components similar to those in the first embodiment, and detailed descriptions are omitted.

[0042] The water treatment system 1B and electrodialysis apparatus 30B of the third embodiment differ from the first and second embodiments in the configuration of the second membrane 42B. In the second membrane 42B of the third embodiment, the second layer 44B has a porous body 60. Figure 5 shows the porous body 60. When the second membrane 42B is placed in the electrodialysis apparatus 30B, the porous body 60 has micropores 61 formed in the direction in which the anode 32 and cathode 33 face each other. Multiple micropores 61 are formed in the porous body 60, spaced apart in the direction in which the membrane expands.

[0043] The micropores 61 are formed to a diameter that allows a desired substance, such as an ion, to pass through. In this embodiment, monovalent ions that are separated and permeated in the first layer 43 can pass through the micropores 61. The diameter of the micropores 61 is, for example, 10 nanometers to 400 nanometers, but is not limited thereto. Furthermore, the second layer 44B according to the third embodiment is preferably 75 micrometers or less in thickness. The second layer 44B is preferably 0 to 75 micrometers in thickness, more preferably 6 to 45 micrometers, and even more preferably 6 to 15 micrometers. Furthermore, the second membrane 42B preferably has an electrical resistance of 7 Ω·cm² or less in a 0.5 mol / L aqueous sodium chloride solution.

[0044] <Effects and Effects> In the water treatment system 1B and electrodialysis apparatus 30B according to the third embodiment, the second layer 44B has a porous body 60. The porous body 60 has a plurality of micropores 61 formed in the direction in which the anode 32 and cathode 33 face each other. This allows substances that can permeate the first layer 43 to pass through while restricting their direction of movement. Therefore, leakage of treated water to the outside can be greatly reduced without hindering the passage of ions that permeate the first layer 43. In addition, by setting the thickness of the second layer 44B to, for example, 75 nanometers or less, the electrical resistance value of the second membrane 42B can be reduced. As described above, the water treatment system 1B of the third embodiment can further reduce the amount of treatment per unit of recovered valuable material while further reducing running costs.

[0045] <Other Embodiments> Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the gist of this disclosure.

[0046] For example, the water treatment systems 1, 1A, and 1B according to one embodiment may be configured without a water treatment introduction section 10 or a reverse osmosis membrane device 20. That is, the water treatment systems 1, 1A, and 1B may be configured such that the water to be treated, such as seawater, can be directly introduced into the electrodialysis machines 30, 30A, and 30B. Alternatively, the water treatment systems 1, 1A, and 1B may be configured with either the water treatment introduction section 10 or the reverse osmosis membrane device 20.

[0047] Furthermore, the membranes 40 according to one embodiment may be in different combinations. For example, in the electrodialysis apparatus 30 according to the first embodiment, the first membrane 41 may be an NF membrane and the second membrane 42 may be an anion exchange membrane. In this configuration, sodium ions, potassium ions, chloride ions, sulfate ions, etc. are concentrated in the concentration chamber 34, and in the dilution chamber 35, the above ions are reduced by permeation, and desalinated water is produced in which magnesium ions, calcium ions, etc. mainly remain. In this way, the ions that are selected may be changed as appropriate.

[0048] Furthermore, the flow pipes 80 according to one embodiment may each have separate branches.

[0049] Furthermore, the recovery unit 70 according to one embodiment may be configured without a mechanism for recovering valuable materials. That is, the recovery unit 70 may be configured such that it can recover treated water (both or either highly concentrated water and desalinated water), and the recovered treated water is processed outside of the water treatment systems 1, 1A, and 1B.

[0050] Furthermore, the membrane 40 according to one embodiment may have selectivity for different valencies, or selectivity for cations and anions. For example, the first layer 43 according to the first embodiment may be permeable to ions up to divalent, or may have further selectivity for cations and anions. By changing the selectivity of the membrane 40 to match the water to be treated in the water treatment systems 1, 1A, and 1B, the target of recovery can be appropriately changed.

[0051] Furthermore, the second layer 44B according to the third embodiment may consist only of the porous body 60. This would further reduce leakage from the second layer 44B to the outside of the electrodialysis apparatus 30B. However, the embodiment is not limited to this, and may further include a layer through which material that has permeated the first layer 43 can pass, such as the support layer 50 according to the first and second embodiments.

[0052] <Note> The water treatment systems 1, 1A, and 1B described in each embodiment can be understood, for example, as follows.

[0053] (1) The water treatment systems 1, 1A, and 1B according to the first embodiment include electrodialysis devices 30, 30A, and 30B that perform electrodialysis on water to be treated to produce treated water, and a recovery unit 70 that recovers the target recovery material from the treated water, wherein the electrodialysis devices 30, 30A, and 30B include an anode 32 and a cathode 33 provided opposite to each other, and a plurality of membranes 40 disposed between the anode 32 and the cathode 33, and a portion of the plurality of membranes 40 includes a first layer 43 having separation performance and a second layer 44, 44A, and 44B that support the first layer 43 and do not have separation performance.

[0054] According to the above configuration, water treatment systems 1, 1A, and 1B are equipped with electrodialysis machines 30, 30A, and 30B having multiple membranes 40. Part of the multiple membranes 40 includes a first layer 43 having ion separation capabilities and a second layer 44, 44A, and 44B that does not have ion separation capabilities. For example, by making the second layer 44, 44A, and 44B thinner, the electrical resistance of the membrane 40 can be reduced. This reduces the power consumption of the electrodialysis machines 30, 30A, and 30B. In addition, leakage of the treated water from the second layer 44, 44A, and 44B to the outside of the electrodialysis machines 30, 30A, and 30B can be suppressed. Furthermore, the recovery unit 70 makes it possible to recover desired substances. Therefore, according to this configuration of water treatment systems 1, 1A, and 1B, it is possible to reduce the processing volume per unit of recovered valuable material while reducing running costs.

[0055] (2) The water treatment systems 1, 1A, and 1B relating to the second embodiment are the water treatment systems 1, 1A, and 1B of (1), wherein the first layer 43 has monovalent selective ion separation performance.

[0056] According to the above configuration, the first layer 43 has the ability to separate monovalent ions selectively. For example, the first layer 43 is a nanofiltration membrane. Since nanofiltration membranes are less expensive than cation exchange membranes and anion exchange membranes, the manufacturing cost of the electrodialysis machines 30, 30A, and 30B can be reduced. Therefore, the water treatment systems 1, 1A, and 1B of this type can reduce the processing volume per unit of recovered valuable material while keeping initial costs down and reducing running costs.

[0057] (3) The water treatment systems 1, 1A, and 1B relating to the third embodiment are the water treatment systems 1, 1A, and 1B of (1) or (2), wherein the second layers 44, 44A, and 44B have a porous body 60 in which micropores 61 are formed that extend in the direction in which the anode 32 and the cathode 33 face each other.

[0058] According to the above configuration, the second layers 44, 44A, and 44B have a porous body 60 in which fine pores 61 are formed that extend in the direction in which the anode 32 and cathode 33 face each other. Therefore, substances that can permeate the first layer 43 can pass through while restricting their direction of movement. Consequently, it is possible to significantly reduce the leakage of treated water from the second layers 44, 44A, and 44B to the outside of the electrodialysis machines 30, 30A, and 30B without hindering the passage of ions that permeate the first layer 43. In this way, according to this configuration, it is possible to further reduce the processing amount per unit of recovered valuable material while further reducing running costs.

[0059] (4) The water treatment systems 1, 1A, and 1B relating to the fourth aspect are any of the water treatment systems 1, 1A, and 1B described in (1) to (3), wherein the second layers 44, 44A, and 44B have a thickness of 75 micrometers or less.

[0060] According to the above configuration, the membrane 40 can be made thinner. Therefore, the electrical resistance of the membrane 40 can be reduced, and leakage of treated water from the membrane 40 to the outside of the electrodialysis machines 30, 30A, and 30B can be suppressed. Accordingly, with the water treatment systems 1, 1A, and 1B of this type, the processing volume per unit of recovered valuable material can be reduced while reducing running costs.

[0061] (5) The water treatment systems 1, 1A, and 1B relating to the fifth aspect are any of the water treatment systems 1, 1A, and 1B described in (1) to (4), further comprising a reverse osmosis membrane device 20 that separates the water to be treated and fresh water introduced from an external source by reverse osmosis. [Explanation of Symbols]

[0062] 1, 1A, 1B Water Treatment System 10. Water to be treated introduction section 20 Reverse osmosis membrane equipment 30, 30A, 30B Electrodialysis Machines 31 Electrodialysis tank 32 Anode 33 Cathode 34 Concentration chamber 35 Dilution Chamber 40 membrane 41 The first membrane 42, 42A, 42B Second membrane 43. The First Layer 44, 44A, 44B Second layer 50 support layer 51 Base material layer 60 Porous material 61 Micropore 70 Recovery Section 71 Metal Recycling Department 72. Valuable Materials Recovery Department 80 Flow pipe 81 Water supply pipe 82 Concentrated water pipe 83 Permeate water pipe 84 Highly concentrated water pipe 85 Desalination water pipe 86 Return pipe 87 Outlet pipe 88 Evaporator tube

Claims

1. An electrodialysis apparatus that produces treated water by performing electrodialysis on the water to be treated, A recovery unit for recovering the target material from the treated water, Equipped with, The electrodialysis apparatus is A positive electrode and a negative electrode are provided opposite each other, A plurality of films disposed between the anode and the cathode, Equipped with, A portion of the aforementioned plurality of membranes is A first layer having separation capabilities, A second layer that supports the first layer and does not have separation capabilities, A water treatment system including a water treatment system.

2. The water treatment system according to claim 1, wherein the first layer has the ability to separate monovalent ions selectively.

3. The water treatment system according to claim 1, wherein the second layer is a porous body having micropores formed in a direction in which the anode and the cathode face each other.

4. The water treatment system according to claim 1, wherein the second layer has a thickness of 75 micrometers or less.

5. A water treatment system according to any one of claims 1 to 4, further comprising a reverse osmosis membrane device for separating water introduced from an external source into the water to be treated and fresh water by reverse osmosis.

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