Wastewater treatment system

Abstract

To provide a wastewater treatment system capable of reducing a cost of regeneration treatment of a desalination apparatus.SOLUTION: A wastewater treatment system for treating regenerated wastewater generated by regenerating a desalination apparatus which performs desalination of water containing ammonia using an acidic aqueous solution is provided with a bipolar membrane electrodialysis device which separates, as the acidic aqueous solution, a solution containing the same acidic solute as the acidic aqueous solution from regenerated wastewater containing ammonium salt generated by the reaction between ammonia captured in the desalination apparatus and an acidic aqueous solution or a liquid derived from the regenerated wastewater. The regenerated acidic aqueous solution is used as at least part of the acidic aqueous solution for regeneration of the desalination apparatus.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 describes an apparatus that recovers ammonia from condensate in a plant such as a thermal power plant and reuses the wastewater after ammonia recovery within the plant. This apparatus removes ammonia from the condensate by passing the condensate through a desalination apparatus equipped with an anion exchanger and a cation exchanger. Although the desalination apparatus needs to be periodically regenerated, regeneration wastewater is generated during the regeneration process. For example, when an aqueous sodium hydroxide solution is used for regenerating the anion exchanger and an aqueous sulfuric acid solution is used for regenerating the cation exchanger, anion exchanger regeneration wastewater containing various anions and sodium hydroxide and cation exchanger regeneration wastewater containing ammonia are generated as regeneration wastewater. In this apparatus, ammonia gas is recovered by distilling the ammonia concentrated water obtained by concentrating the cation exchanger regeneration wastewater, but by supplying the alkaline water obtained by separating the alkaline components by electrodialyzing the anion exchanger regeneration wastewater during distillation, the transfer of ammonia from the ammonia concentrated water to the gas phase can be promoted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the cost of chemicals such as the aqueous sulfuric acid solution and the aqueous sodium hydroxide solution used in the regeneration process of the desalination apparatus is increasing, and the cost of the regeneration process of the desalination apparatus is becoming a problem in an increasing number of cases.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a wastewater treatment system capable of reducing the cost of the regeneration treatment of a desalination device.

Means for Solving the Problems

[0006] To achieve the above object, a wastewater treatment system according to the present disclosure is a wastewater treatment system for treating regenerated wastewater generated by subjecting a desalination device that desalinates water containing ammonia to a regeneration treatment using an acidic aqueous solution, and separating an aqueous solution containing the same acidic solute as the acidic aqueous solution as a regenerated acidic aqueous solution from the regenerated wastewater containing an ammonium salt generated by the reaction of the ammonia captured by the desalination device and the acidic aqueous solution or a liquid derived from the regenerated wastewater, a bipolar membrane electrodialyzer an acidic aqueous solution tank for storing the acidic aqueous solution, an acidic aqueous solution supply line communicating the acidic aqueous solution tank and the desalting device, a regenerated drainage outflow line communicating the desalting device and the bipolar membrane electrodialyzer, and a regenerated acidic aqueous solution supply line communicating the bipolar membrane electrodialyzer and the acidic aqueous solution tank comprising, wherein the regenerated acidic aqueous solution [[ID=×1]]which is supplied to the acidic aqueous solution tank via the regenerated acidic aqueous solution supply line and is configured to be used as at least a part of the acidic aqueous solution [[ID=×2]]is supplied to the desalting device via the acidic aqueous solution supply line, whereby for regenerating the desalination device.

Advantages of the Invention

[0007] According to the wastewater treatment system of the present disclosure, by separating the regenerated acidic aqueous solution from the regenerated wastewater generated by subjecting the desalination device to a regeneration treatment using an acidic aqueous solution or a liquid derived from the regenerated wastewater, and reusing the regenerated acidic aqueous solution as at least a part of the acidic aqueous solution for regenerating the desalination device, the consumption amount of the acidic aqueous solution can be suppressed, so that the cost of the regeneration treatment of the desalination device can be reduced.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Embodiments for Carrying Out the Invention

[0009] Hereinafter, a wastewater treatment system according to an embodiment of the present disclosure will be described with reference to the drawings. Such an embodiment shows one aspect of the present disclosure, does not limit this disclosure, and can be arbitrarily changed within the scope of the technical idea of the present disclosure.

[0010] (Embodiment 1) <Configuration of the Wastewater Treatment System According to Embodiment 1 of the Present Disclosure> As shown in FIG. 1, the wastewater treatment system 1 according to Embodiment 1 of the present disclosure is for treating the regenerated wastewater generated by regenerating a desalination device 2 that removes ammonia from water containing ammonia, for example, the condensate of a boiler in a thermal power plant, that is, desalinating the condensate. In Embodiment 1, the desalination device 2 will be described as having a configuration including a cation exchange resin 2a, but it is not limited to this form. Any desalination device can be used as long as it has a configuration that can temporarily capture ammonia, such as a medium like an adsorbent capable of adsorbing ammonia, and can remove ammonia from the medium capturing ammonia by a regeneration process.

[0011] Connected to the desalination device 2 are a condensate inflow line 3 for supplying water containing ammonia (hereinafter referred to as "condensate") into the desalination device 2, and a condensate outflow line 4 through which the desalinated condensate flows out of the desalination device 2.

[0012] The desalination device 2 communicates with an acidic aqueous solution tank 5 that stores an acidic aqueous solution used for the regeneration process of the desalination device 2 via an acidic aqueous solution supply line 6. In Embodiment 1, the acidic aqueous solution is a sulfuric acid aqueous solution having sulfuric acid as an acidic solute, but it is not limited to the sulfuric acid aqueous solution, and any acidic aqueous solution such as hydrochloric acid or nitric acid aqueous solution can be used. The pH of the acidic aqueous solution is preferably 2 or less.

[0013] Further, one end of a regenerated drainage outflow line 7 through which regenerated drainage generated by subjecting the desalting device 2 to a regeneration treatment flows out is connected to the desalting device 2, and the other end of the regenerated drainage outflow line 7 is connected to a two-chamber bipolar membrane electrodialyzer 8. Although the specific configuration and operation of the bipolar membrane electrodialyzer 8 will be described later, when the regenerated drainage is electrodialyzed in the bipolar membrane electrodialyzer 8, the regenerated drainage is separated into a regenerated acidic aqueous solution (regenerated sulfuric acid aqueous solution) containing the same acidic solute (sulfuric acid) as the acidic aqueous solution and an aqueous ammonia solution. The bipolar membrane electrodialyzer 8 communicates with the acidic aqueous solution tank 5 via a regenerated acidic aqueous solution supply line 11 so as to be able to supply the regenerated sulfuric acid aqueous solution to the acidic aqueous solution tank 5, and communicates with the aqueous ammonia storage tank 12 via an aqueous ammonia supply line 13 so as to be able to supply the aqueous ammonia to the aqueous ammonia storage tank 12.

[0014] Although not an essential component of the wastewater treatment system 1, a concentrator 14 for concentrating an ammonium salt (ammonium sulfate) formed by the reaction of sulfuric acid and ammonia with respect to the regenerated drainage before flowing into the bipolar membrane electrodialyzer 8 may be provided in the regenerated drainage outflow line 7. The configuration of the concentrator 14 is not particularly limited, and for example, a device equipped with a reverse osmosis membrane or a nanofiltration membrane can be used. Further, in the regenerated drainage outflow line 7, a device 15 equipped with a filter for removing suspended substances and a device 16 equipped with a chelating resin for removing iron, calcium, magnesium, etc. may be provided upstream of the concentrator 14.

[0015] As shown in FIG. 2, the bipolar membrane electrodialyzer 8 includes an anode 21, a cathode 29, and a cell 30 provided between the anode 21 and the cathode 29. The cell 30 includes a first bipolar membrane 24 including a first anion exchange membrane 22 facing the anode 21 and a first cation exchange membrane 23 located on the side opposite to the anode 21 with respect to the first anion exchange membrane 22, a second cation exchange membrane 25 facing the first cation exchange membrane 23, a second anion exchange membrane 26 facing the second cation exchange membrane 25, and a second bipolar membrane 28 including a third cation exchange membrane 27 located on the side opposite to the second cation exchange membrane 25 with respect to the second anion exchange membrane 26. A first chamber 31 is formed between the first bipolar membrane 24 and the second cation exchange membrane 25, and a second chamber 32 is formed between the second cation exchange membrane 25 and the second bipolar membrane 28. The second chamber 32 is initially filled with aqueous ammonia. Each of the chamber 33 formed between the anode 21 and the first bipolar membrane 24 and the chamber 34 formed between the second bipolar membrane 28 and the cathode 29 is filled with an arbitrary electrode solution. As long as it is limited to the membranes facing the anode 21 and the cathode 29 respectively, depending on the type of the electrode solution, instead of each of the first bipolar membrane 24 and the second bipolar membrane 28, either the first anion exchange membrane 22 or the first cation exchange membrane 23, and either the second anion exchange membrane 26 or the third cation exchange membrane 27 can be used.

[0016] The first chamber 31 communicates with each of the recycled drainage outflow line 7 and the recycled acidic aqueous solution supply line 11. That is, the first chamber 31 is configured such that recycled drainage is supplied to the first chamber 31 via the recycled drainage outflow line 7 and the recycled acidic aqueous solution flows out from the first chamber 31 via the recycled acidic aqueous solution supply line 11. The second chamber 32 communicates with the aqueous ammonia supply line 13. That is, the second chamber 32 is configured such that aqueous ammonia flows out from the second chamber 32 via the aqueous ammonia supply line 13. In FIG. 2, it is depicted that the recycled acidic aqueous solution and the aqueous ammonia each directly flow out from the first chamber 31 and the second chamber 32, respectively, but the present invention is not limited to this form. A recycle line may be provided to allow a part of the liquid to flow out from each of the first chamber 31 and the second chamber 32 and return to each of the first chamber 31 and the second chamber 32 again, and the recycled acidic aqueous solution supply line 11 and the aqueous ammonia supply line 13 may be connected to each recycle line. Further, an aqueous ammonia return line 17 branches from the aqueous ammonia supply line 13, and the aqueous ammonia return line 17 is connected to the second chamber 32. That is, a part of the aqueous ammonia flowing through the aqueous ammonia supply line 13 is configured to be supplied to the second chamber 32 via the aqueous ammonia return line 17.

[0017] As shown in FIG. 3, the cell 30 may include a repeating unit 200 including a fourth cation exchange membrane 201 facing the third cation exchange membrane 27, a third anion exchange membrane 202 facing the fourth cation exchange membrane 201, and a third bipolar membrane 204 including a fifth cation exchange membrane 203 between the second bipolar membrane 28 and the cathode 29. However, although FIG. 3 shows a configuration in which the cell 30 includes two repeating units 200, the present invention is not limited to this form. The cell 30 may include one repeating unit 200, or may include any number of three or more repeating units 200.

[0018] When the cell 30 includes one repeating unit 200, the first chamber 31 is formed by the second bipolar membrane 28 and the fourth cation exchange membrane 201, and the second chamber 32 is formed by the fourth cation exchange membrane 201 and the third bipolar membrane 204. When the cell 30 includes two or more repeating units 200, the first chamber 31 is also formed by one third bipolar membrane 204 of two adjacent repeating units 200, 200 and the fourth cation exchange membrane 201 of the other of the two adjacent repeating units 200, 200. In each repeating unit 200, the second chamber 32 is formed by the fourth cation exchange membrane 201 and the third bipolar membrane 204.

[0019] <Operation of the wastewater treatment system according to Embodiment 1 of the present disclosure> Next, the operation of the wastewater treatment system 1 according to Embodiment 1 of the present disclosure will be described. As shown in FIG. 1, when the treated water flowing through the treated water inflow line 3 flows into the desalting device 2, the cations of the cation exchange resin 2a are exchanged with ammonium ions, and ammonia in the treated water is captured by the desalting device 2. By removing ammonia from the treated water in this way, the treated water with a reduced ammonia concentration flows out of the desalting device 2 through the treated water outflow line 4.

[0020] When the desalting of the treated water by the desalting device 2 continues, the amount of ammonia captured by the desalting device 2 increases, so there is a need to regenerate the desalting device 2. To regenerate the desalting device 2, an aqueous sulfuric acid solution is supplied from the aqueous acid solution tank 5 to the desalting device 2 through the aqueous acid solution supply line 6. When the aqueous sulfuric acid solution is supplied to the desalting device 2, the ammonium ions captured by the cation exchange resin are exchanged with hydrogen ions. As a result, ammonium sulfate (actually, sulfate ions and ammonium ions) is generated. The regenerated wastewater flowing out of the desalting device 2 through the regenerated wastewater outflow line 7 contains sulfuric acid and ammonium sulfate. The regenerated wastewater flowing through the regenerated wastewater outflow line 7 is supplied to the bipolar membrane electrodialyzer 8.

[0021] As shown in FIG. 2, the regenerated drainage water flows into the first chamber 31 of the bipolar membrane electrodialyzer 8. By applying an electric current between the anode 21 and the cathode 29, the regenerated drainage water is electrodialyzed. The ammonium ions in the regenerated drainage water that has flowed into the first chamber 31 are attracted to the cathode 29 and permeate through the second cation exchange membrane 25 to flow into the second chamber 32. In the first bipolar membrane 24, water is absorbed into the membrane by the absorption action and dissociates into hydrogen ions and hydroxide ions at the interface between the first anion exchange membrane 22 and the first cation exchange membrane 23. The hydrogen ions thus generated flow into the first chamber 31 through the first cation exchange membrane 23, and the hydroxide ions flow into the chamber 33 through the first anion exchange membrane 22. Similarly, in the second bipolar membrane 28, at the interface between the second anion exchange membrane 26 and the third cation exchange membrane 27, water dissociates into hydrogen ions and hydroxide ions, and the generated hydroxide ions flow into the second chamber 32 through the second anion exchange membrane 26, and the hydrogen ions flow into the chamber 34 through the third cation exchange membrane 27.

[0022] The ammonium ions in the first chamber 31 move to the second chamber 32, and hydrogen ions flow into the first chamber 31 from the first bipolar membrane 24. Therefore, the concentration of ammonium sulfate in the regenerated drainage water that has flowed into the first chamber 31 decreases, and the concentration of sulfuric acid increases. As a result, a regenerated sulfuric acid aqueous solution with a higher sulfuric acid concentration than the regenerated drainage water flowing into the first chamber 31 flows out of the first chamber 31. In the second chamber 32, as ammonium ions move from the first chamber 31, the concentration of ammonium ions in the water in the second chamber 32 increases. As a result, aqueous ammonia flows out of the second chamber 32. A part of the aqueous ammonia flowing out of the second chamber 32 continues to be supplied to the second chamber 32 through the aqueous ammonia return line 17. Therefore, the second chamber 32 continues to be filled with an ionic aqueous solution (specifically, an aqueous solution containing ammonium ions and hydroxide ions), so that when an electric current is applied between the anode 21 and the cathode 29, an electric current continues to flow through the second chamber 32, and the above operation continues.

[0023] As shown in FIG. 1, the regenerated sulfuric acid aqueous solution flowing out from the first chamber 31 is supplied to the acidic aqueous solution tank 5 via the regenerated acidic aqueous solution supply line 11, and is reused for the regeneration treatment of the desalting device 2 as at least a part of the acidic aqueous solution. The aqueous ammonia flowing out from the second chamber 32 is supplied to the aqueous ammonia storage tank 12 via the aqueous ammonia supply line 13 and is used for a boiler or a denitration device (not shown).

[0024] In this way, by separating the regenerated acidic aqueous solution from the regenerated drainage water generated by regenerating the desalting device 2 using the acidic aqueous solution and reusing the regenerated acidic aqueous solution for the regeneration of the desalting device 2 as at least a part of the acidic aqueous solution, the consumption amount of the acidic aqueous solution can be suppressed, so that the cost of the regeneration treatment of the desalting device 2 can be reduced.

[0025] In Embodiment 1, when the concentrator 14 is provided in the regenerated drainage water outflow line 7, the regenerated drainage water is concentrated with ammonium sulfate in the concentrator 14 before flowing into the bipolar membrane electrodialyzer 8. The regenerated drainage water in which ammonium sulfate is concentrated flows into the bipolar membrane electrodialyzer 8, and the components separated from the regenerated drainage water in the concentrator 14, mainly water, are reused in the plant where the drainage treatment system 1 is provided. This component may be reused as an acidic aqueous solution when the pH is low.

[0026] When the concentration of the ammonium salt in the regenerated drainage water is low, the separation efficiency of the regenerated acidic aqueous solution by electrodialysis decreases. On the other hand, by providing the concentrator 14 in the regenerated drainage water outflow line 7, electrodialysis can be performed on the regenerated drainage water with an increased concentration of the ammonium salt, so that the separation efficiency of the regenerated acidic aqueous solution by electrodialysis can be increased.

[0027] By further providing devices 15 and 16 in the regenerated drainage outflow line 7, the concentration of suspended substances and the concentration of polyvalent cations such as iron ions, calcium ions, and magnesium ions in the regenerated drainage can be reduced. As a result, in the regenerated drainage flowing into the bipolar membrane electrodialyzer 8, the concentration of components other than ammonium sulfate can be further reduced, so that the separation efficiency of the regenerated acidic aqueous solution by electrodialysis can be further enhanced.

[0028] (Embodiment 2) Next, the drainage treatment system according to Embodiment 2 will be described. The drainage treatment system according to Embodiment 2 is obtained by adding an ammonia stripper for removing ammonia from the regenerated drainage to Embodiment 1. In addition, in Embodiment 2, the same components as those in Embodiment 1 are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0029] <Configuration of the drainage treatment system according to Embodiment 2 of the present disclosure> As shown in FIG. 4, the drainage treatment system 1 according to Embodiment 1 of the present disclosure includes a supply device 40 for supplying an aqueous sodium hydroxide solution as an alkaline aqueous solution to the regenerated drainage flowing through the regenerated drainage outflow line 7, and an ammonia stripper 50 for separating ammonia from the regenerated drainage to which the aqueous sodium hydroxide solution has been supplied. Different from Embodiment 1, a three-chamber bipolar membrane electrodialyzer 18 is connected to the downstream end of the regenerated drainage outflow line 7. In Embodiment 2, an aqueous sodium hydroxide solution is used as the alkaline aqueous solution, but the present invention is not limited to the aqueous sodium hydroxide solution, and an aqueous solution containing an arbitrary alkali metal hydroxide as a solute can be used. The pH of the alkaline aqueous solution is preferably 11 or more.

[0030] The supply device 40 includes an alkaline aqueous solution tank 41 for storing the aqueous sodium hydroxide solution, and an alkaline aqueous solution supply line 42 having one end connected to the alkaline aqueous solution tank 41 and the other end connected to the regenerated drainage outflow line 7 upstream of the ammonia stripper 50.

[0031] The ammonia stripper 50 has a housing 51 extending vertically. Inside the housing 51, a discharge section 52 for discharging the regenerated drainage downward in the vertical direction is provided in the regenerated drainage outflow line 7. Further, one end of a high-temperature gas supply line 53 for supplying high-temperature gas containing steam into the housing 51 is connected to the housing 51 at a position below the discharge section 52. Although the operation of the ammonia stripper 50 will be described later, in the housing 51, the regenerated drainage falling downward from the discharge section 52 comes into contact with the high-temperature gas supplied into the housing 51 through the high-temperature gas supply line 53 and rising. One end of an outflow line 63 through which the high-temperature gas that has risen inside the housing 51 flows out of the housing 51 is connected to the top of the housing 51. The regenerated drainage outflow line 7 is composed of an upstream-side regenerated drainage outflow line 7a extending from the desalination device 2 to the discharge section 52 and a downstream-side regenerated drainage outflow line 7b extending from the bottom of the housing 51 to the bipolar membrane electrodialyzer 18, and the downstream-side regenerated drainage outflow line 7b is connected to the bottom of the housing 51. In the housing 51, a packing 65 such as Raschig rings may be accommodated at a position where the regenerated drainage and the high-temperature air come into contact, or one or more plates may be provided.

[0032] A heat exchanger 66 for heat-exchanging the regenerated drainage flowing through the upstream-side regenerated drainage outflow line 7a and the drainage liquid of the ammonia stripper 50 flowing through the downstream-side regenerated drainage outflow line 7b can be provided in the regenerated drainage outflow line 7. Similar to Embodiment 1, in Embodiment 2, a concentrator 14 and devices 15 and 16 can be provided in the downstream-side regenerated drainage outflow line 7b.

[0033] At the other end of the outflow line 63, a catalyst tower 54 filled with a catalyst for burning ammonia in a reducing atmosphere is connected. Between the housing 51 and the catalyst tower 54, a blower 55, a heat exchanger 56, and a heater 57 are provided in the outflow line 63. At the top of the catalyst tower 54, a reaction gas outflow line 58 through which a reaction gas containing nitrogen and water generated by burning ammonia in a reducing atmosphere flows out is connected. The heat exchanger 56 is configured such that the high-temperature gas flowing through the outflow line 63 and the reaction gas flowing through the reaction gas outflow line 58 exchange heat. At the other end of the high-temperature gas supply line 53 is connected to the reaction gas outflow line 58 downstream of the heat exchanger 56. With this configuration, a part of the reaction gas that has passed through the heat exchanger 56 can flow into the high-temperature gas supply line 53. Connected to the high-temperature gas supply line 53 are an air supply line 59 for supplying air to the reaction gas flowing through the high-temperature gas supply line 53 and a steam supply line 60 for supplying steam to the reaction gas flowing through the high-temperature gas supply line 53.

[0034] Although the specific configuration and operation of the bipolar membrane electrodialyzer 18 will be described later, in the bipolar membrane electrodialyzer 18, when the drainage of the ammonia stripper 50, which is a liquid derived from the regenerated drainage, is electrodialyzed, the drainage is separated into a regenerated sulfuric acid aqueous solution, a regenerated alkaline aqueous solution having sodium hydroxide as a solute, and a diluent. The bipolar membrane electrodialyzer 18 communicates with the acidic aqueous solution tank 5 via a regenerated acidic aqueous solution supply line 11 so as to be able to supply the regenerated sulfuric acid aqueous solution to the acidic aqueous solution tank 5, communicates with the alkaline aqueous solution tank 41 via a regenerated alkaline aqueous solution supply line 61 so as to be able to supply the regenerated alkaline aqueous solution to the alkaline aqueous solution tank 41, and communicates with the downstream regenerated drainage outflow line 7b between the apparatus 16 and the concentrator 14 via a diluent return line 62 so as to be able to supply the diluent to the drainage before it flows into the concentrator 14. Other configurations are the same as those in the first embodiment except for the configuration of the bipolar membrane electrodialyzer 18 described below.

[0035] As shown in Fig. 5, the bipolar membrane electrodialyzer 18 includes an anode 71, a cathode 80, and a cell 90 provided between the anode 71 and the cathode 80. The cell 90 includes a first bipolar membrane 74 including a first anion exchange membrane 72 facing the anode 71 and a first cation exchange membrane 73 located on the side opposite to the anode 71 with respect to the first anion exchange membrane 72, a second anion exchange membrane 75 facing the first cation exchange membrane 73, a second cation exchange membrane 76 facing the second anion exchange membrane 75, a third anion exchange membrane 77 facing the second cation exchange membrane 76, and a second bipolar membrane 79 including a third cation exchange membrane 78 located on the side opposite to the second cation exchange membrane 76 with respect to the third anion exchange membrane 77. A first chamber 81 is formed between the second anion exchange membrane 75 and the second cation exchange membrane 76, a second chamber 82 is formed between the first bipolar membrane 74 and the second anion exchange membrane 75, and a third chamber 83 is formed between the second cation exchange membrane 76 and the second bipolar membrane 79. The second chamber 82 is initially filled with an aqueous sulfuric acid solution, and the third chamber 83 is initially filled with an aqueous sodium hydroxide solution. Each of the chamber 84 formed between the anode 71 and the first bipolar membrane 74 and the chamber 85 formed between the second bipolar membrane 79 and the cathode 80 is filled with an arbitrary electrode solution. As long as it is limited to the membranes facing the anode 71 and the cathode 80 respectively, depending on the type of the electrode solution, instead of each of the first bipolar membrane 74 and the second bipolar membrane 79, either the first anion exchange membrane 72 or the first cation exchange membrane 73, and either the third anion exchange membrane 77 or the third cation exchange membrane 78 can be used.

[0036] The first chamber 81 communicates with each of the downstream-side regenerated drainage outflow line 7b and the diluent return line 62. That is, the first chamber 81 is configured such that the drainage of the ammonia stripper 50 (see FIG. 4) is supplied to the first chamber 81 via the downstream-side regenerated drainage outflow line 7b and the diluent flows out from the first chamber 81 via the diluent return line 62. The second chamber 82 communicates with the regenerated acidic aqueous solution supply line 11. That is, the second chamber 82 is configured such that the regenerated acidic aqueous solution flows out from the second chamber 82 via the regenerated acidic aqueous solution supply line 11. The third chamber 83 communicates with the regenerated alkaline aqueous solution supply line 61. That is, the third chamber 83 is configured such that the regenerated alkaline aqueous solution flows out from the third chamber 83 via the regenerated alkaline aqueous solution supply line 61. Further, a regenerated acidic aqueous solution return line 19 branches from the regenerated acidic aqueous solution supply line 11, and the regenerated acidic aqueous solution return line 19 is connected to the second chamber 82. That is, a part of the regenerated acidic aqueous solution flowing through the regenerated acidic aqueous solution supply line 11 is configured to be supplied to the second chamber 82 via the regenerated acidic aqueous solution return line 19. A regenerated alkaline aqueous solution return line 20 branches from the regenerated alkaline aqueous solution supply line 61, and the regenerated alkaline aqueous solution return line 20 is connected to the third chamber 83. That is, a part of the regenerated alkaline aqueous solution flowing through the regenerated alkaline aqueous solution supply line 61 is configured to be supplied to the third chamber 83 via the regenerated alkaline aqueous solution return line 20.

[0037] As shown in FIG. 6, the cell 90 may include a repeating unit 300 including a fourth anion exchange membrane 301 facing the third cation exchange membrane 78, a fourth cation exchange membrane 302 facing the fourth anion exchange membrane 301, and a third bipolar membrane 305 including a fifth anion exchange membrane 303 and a fifth cation exchange membrane 304 facing the fourth cation exchange membrane 302, between the second bipolar membrane 79 and the cathode 80. However, although FIG. 6 shows a configuration in which the cell 90 includes two repeating units 300, the present invention is not limited to this form. The cell 90 may include one repeating unit 300, or may include any number of three or more repeating units 300.

[0038] When the cell 90 includes one repeating unit 300, a first chamber 81 is formed by a fourth anion exchange membrane 301 and a fourth cation exchange membrane 302, a second chamber 82 is formed by a second bipolar membrane 79 and the fourth anion exchange membrane 301, and a third chamber 83 is formed by the fourth cation exchange membrane 302 and a third bipolar membrane 305. When the cell 90 includes two or more repeating units 300, a first chamber 81 is formed by the fourth anion exchange membrane 301 and the fourth cation exchange membrane 302 in each of the repeating units 300, a second chamber 82 is also formed by one third bipolar membrane 305 of two adjacent repeating units 300, 300 and the fourth anion exchange membrane 301 of the other of the two adjacent repeating units 300, 300, and a third chamber 83 is formed by the fourth cation exchange membrane 302 and the third bipolar membrane 305 in each of the repeating units 300.

[0039] <Operation of the wastewater treatment system according to Embodiment 2 of the present disclosure> Next, the operation of the wastewater treatment system 1 according to Embodiment 2 of the present disclosure will be described. Since the operation of Embodiment 2 is different from that of Embodiment 1 in terms of the treatment operation of the regeneration wastewater of the desalination device 2, only the treatment operation of the regeneration wastewater of the desalination device 2 will be described below. As shown in FIG. 4, an aqueous sodium hydroxide solution is supplied from an alkaline aqueous solution tank 41 to the regeneration wastewater flowing out of the desalination device 2 through an alkaline aqueous solution supply line 42. When the aqueous sodium hydroxide solution is supplied to the regeneration wastewater, the pH of the regeneration wastewater rises. However, as the pH rises, the proportion of ammonia in the regeneration wastewater existing in the form of free ammonia rather than in the form of ammonium ions increases. This can be described by the following reaction formula. (NH4)2SO4 + 2NaOH → Na2SO4 + 2H2O + 2NH3 Free ammonia has a tendency to be more easily released from water when the aqueous solution is heated than ammonium ions.

[0040] The regenerated wastewater supplied with an aqueous sodium hydroxide solution is heated in the heat exchanger 66 by heat-exchanging with the drainage liquid of the ammonia stripper 50 described later, and then discharged into the housing 51 from the discharge part 52 and falls within the housing 51. High-temperature gas is also supplied to the housing 51 through the high-temperature gas supply line 53, and the high-temperature gas rises within the housing 51. In the housing 51, the falling regenerated wastewater and the rising high-temperature gas come into contact with each other, so that the regenerated wastewater is heated, and mainly free ammonia is dissipated from the regenerated wastewater. The ammonia dissipated from the regenerated wastewater is mixed with the high-temperature gas as ammonia gas and flows out from the top of the housing 51, and flows through the outflow line 63.

[0041] The high-temperature gas flowing through the outflow line 63 is blown by the blower 55, heated by sequentially passing through the heat exchanger 56 and the heater 57, and then flows into the catalyst tower 54. In the catalyst tower 54, ammonia is combusted in a reducing atmosphere to generate a reaction gas mainly containing nitrogen and water. The reaction gas flowing out from the catalyst tower 54 flows through the reaction gas outflow line 58 and is cooled by heat-exchanging with the high-temperature gas in the heat exchanger 56. A part of the cooled reaction gas flows into the high-temperature gas supply line 53, and the rest is exhausted into the atmosphere. Air and steam are supplied to the reaction gas flowing into the high-temperature gas supply line 53 through the air supply line 59 and the steam supply line 60 respectively, and become high-temperature gas and are supplied into the housing 51.

[0042] Since ammonia is dissipated from the regenerated wastewater falling within the housing 51 by the above-described operation, the regenerated wastewater accumulated at the bottom within the housing 51 has a lower ammonia concentration than the regenerated wastewater discharged from the discharge part 52, and is mainly an aqueous solution in which sodium sulfate is dissolved. This aqueous solution is discharged from the bottom of the housing 51 as the drainage liquid of the ammonia stripper 50 and flows through the downstream regenerated wastewater outflow line 7b. This drainage liquid is cooled by heat-exchanging with the regenerated wastewater in the heat exchanger 66 when flowing through the downstream regenerated wastewater outflow line 7b, and is supplied to the bipolar membrane electrodialyzer 18.

[0043] As shown in FIG. 5, the drainage liquid flows into the first chamber 81 of the bipolar membrane electrodialyzer 18. By applying an electric current between the anode 71 and the cathode 80, the drainage liquid is electrodialyzed. Sulfate ions in the drainage liquid that has flowed into the first chamber 81 are attracted to the anode 71 and permeate through the second anion exchange membrane 75 and flow into the second chamber 82. In the first bipolar membrane 74, water is absorbed into the membrane by the absorption action and dissociates into hydrogen ions and hydroxide ions at the interface between the first anion exchange membrane 72 and the first cation exchange membrane 73. The hydrogen ions thus generated flow into the second chamber 82 through the first cation exchange membrane 73, and the hydroxide ions flow into the chamber 84 through the first anion exchange membrane 72. Sodium ions in the drainage liquid that has flowed into the first chamber 81 are attracted to the cathode 80 and permeate through the second cation exchange membrane 76 and flow into the third chamber 83. In the second bipolar membrane 79, water is absorbed into the membrane by the absorption action and dissociates into hydrogen ions and hydroxide ions at the interface between the third anion exchange membrane 77 and the third cation exchange membrane 78. The hydroxide ions thus generated flow into the third chamber 83 through the third anion exchange membrane 77, and the hydrogen ions flow into the chamber 85 through the third cation exchange membrane 78.

[0044] Since the sulfate ions in the first chamber 81 move to the second chamber 82 and the sodium ions move to the third chamber 83, the concentration of sodium sulfate in the drainage liquid that has flowed into the first chamber 81 decreases. For this reason, a diluted liquid with a lower concentration of sodium sulfate than the drainage liquid flowing into the first chamber 81 flows out from the first chamber 81, and the diluted liquid is returned to the downstream-side regenerated drainage outflow line 7b via the diluted liquid return line 62.

[0045] The sulfate ions that have moved from the first chamber 81 to the second chamber 82 react with the hydrogen ions that have moved from the first bipolar membrane 74 to the second chamber 82 to form sulfuric acid. As a result, the aqueous solution in the second chamber 82 becomes a sulfuric acid aqueous solution. From the second chamber 82, this sulfuric acid aqueous solution flows out as a regenerated acidic aqueous solution, and the regenerated acidic aqueous solution is supplied to the acidic aqueous solution tank 5 via the regenerated acidic aqueous solution supply line 11 and reused for the regeneration process of the desalination device 2. A part of the regenerated acidic aqueous solution flowing out from the second chamber 82 is continuously supplied to the second chamber 82 via the regenerated acidic aqueous solution return line 19. As a result, the second chamber 82 continues to be filled with an ionic aqueous solution (specifically, an aqueous solution containing sulfate ions and hydrogen ions). Therefore, when an electric current is passed between the anode 71 and the cathode 80, a current continues to flow through the second chamber 82, and the above operation continues.

[0046] The sodium ions that have moved from the first chamber 81 to the third chamber 83 react with the hydroxide ions that have moved from the second bipolar membrane 79 to the third chamber 83 to form sodium hydroxide. As a result, the aqueous solution in the third chamber 83 becomes a sodium hydroxide aqueous solution. From the third chamber 83, this sodium hydroxide aqueous solution flows out as a regenerated alkaline aqueous solution, and the regenerated alkaline aqueous solution is supplied to the alkaline aqueous solution tank 41 via the regenerated alkaline aqueous solution supply line 61 and reused for the treatment of the regenerated wastewater generated by the regeneration process of the desalination device 2. A part of the regenerated alkaline aqueous solution flowing out from the third chamber 83 is continuously supplied to the third chamber 83 via the regenerated alkaline aqueous solution return line 20. As a result, the third chamber 83 continues to be filled with an ionic aqueous solution (specifically, an aqueous solution containing sodium ions and hydroxide ions). Therefore, when an electric current is passed between the anode 71 and the cathode 80, a current continues to flow through the third chamber 83, and the above operation continues.

[0047] When the concentrator 14 is provided in the upstream and downstream regenerated drainage outflow line 7b, the operation when the devices 15 and 16 are further provided and the resulting effects are basically the same as those in the first embodiment. However, in the second embodiment, when the concentrator 14 is not provided, if the diluted solution separated by the bipolar membrane electrodialyzer 18 is returned to the downstream regenerated drainage outflow line 7b, the drainage flowing into the bipolar membrane electrodialyzer 18 will be diluted, reducing the efficiency of electrodialysis. Therefore, the diluted solution has to be treated as drainage. On the other hand, by providing the concentrator 14, the diluted solution can be concentrated together with the drainage and then electrodialyzed again. Thus, compared with the case where the concentrator 14 is not provided, the separation amount of the regenerated acidic aqueous solution and the regenerated alkaline aqueous solution can be increased.

[0048] In this way, after supplying an alkaline aqueous solution to the regenerated drainage generated by regenerating the desalting device 2 using an acidic aqueous solution and separating ammonia with the ammonia stripper 50, the regenerated acidic aqueous solution and the regenerated alkaline aqueous solution are separated from the drainage of the ammonia stripper 50. The regenerated acidic aqueous solution is reused as at least a part of the acidic aqueous solution for regenerating the desalting device 2, and the regenerated alkaline aqueous solution is supplied to the regenerated drainage as at least a part of the alkaline aqueous solution. As a result, the consumption amounts of the acidic aqueous solution and the alkaline aqueous solution can be suppressed, and thus the cost of the regeneration treatment of the desalting device 2 can be reduced.

[0049] <Modification example of the drainage treatment system of the present disclosure> In the first embodiment, the two-chamber bipolar membrane electrodialyzer 8 was used, but the three-chamber bipolar membrane electrodialyzer 18 used in the drainage treatment system 1 according to the second embodiment can also be used. Hereinafter, a modification example in which the three-chamber bipolar membrane electrodialyzer 18 is used in the first embodiment will be described.

[0050] As shown in Fig. 7, the bipolar membrane electrodialyzer 18 communicates with the acidic aqueous solution tank 5 and the ammonia water storage tank 12 via the regenerated acidic aqueous solution supply line 11 and the ammonia water supply line 13, respectively. Further, the bipolar membrane electrodialyzer 18 communicates with the device 16 and the concentrator 14 via the dilution liquid return line 62 so that a dilution liquid can be supplied to the regenerated drainage before flowing into the concentrator 14 in the regenerated drainage outflow line 7.

[0051] As shown in Fig. 8, the first chamber 81 communicates with each of the regenerated drainage outflow line 7 and the dilution liquid return line 62. That is, the first chamber 81 is configured such that the regenerated drainage is supplied to the first chamber 81 via the regenerated drainage outflow line 7 and the dilution liquid flows out from the first chamber 81 via the dilution liquid return line 62. The second chamber 82 communicates with the regenerated acidic aqueous solution supply line 11. That is, the second chamber 82 is configured such that the regenerated acidic aqueous solution flows out from the second chamber 82 via the regenerated acidic aqueous solution supply line 11. The third chamber 83 communicates with the ammonia water supply line 13. That is, the third chamber 83 is configured such that the ammonia water flows out from the third chamber 83 via the ammonia water supply line 13. The second chamber 82 is initially filled with a sulfuric acid aqueous solution, and the third chamber 83 is initially filled with ammonia water. Further, a regenerated acidic aqueous solution return line 19 branches from the regenerated acidic aqueous solution supply line 11, and the regenerated acidic aqueous solution return line 19 is connected to the second chamber 82. That is, a part of the regenerated acidic aqueous solution flowing through the regenerated acidic aqueous solution supply line 11 is configured to be supplied to the second chamber 82 via the regenerated acidic aqueous solution return line 19. An ammonia water return line 17 branches from the ammonia water supply line 13, and the ammonia water return line 17 is connected to the third chamber 83. That is, a part of the ammonia water flowing through the ammonia water supply line 13 is configured to be supplied to the third chamber 83 via the ammonia water return line 17.

[0052] The regenerated wastewater flows into the first chamber 81 of the bipolar membrane electrodialyzer 18. By applying an electric current between the anode 71 and the cathode 80, the regenerated wastewater is electrodialyzed. The sulfate ions in the regenerated wastewater flowing into the first chamber 81 are attracted to the anode 71, permeate through the second anion exchange membrane 75, and flow into the second chamber 82. In the first bipolar membrane 74, water is absorbed into the membrane by the absorption action and dissociates into hydrogen ions and hydroxide ions at the interface between the first anion exchange membrane 72 and the first cation exchange membrane 73. The hydrogen ions thus generated flow into the second chamber 82 through the first cation exchange membrane 73, and the hydroxide ions flow into the chamber 84 through the first anion exchange membrane 72. The ammonium ions in the regenerated wastewater flowing into the first chamber 81 are attracted to the cathode 80, permeate through the second cation exchange membrane 76, and flow into the third chamber 83. In the second bipolar membrane 79, water is absorbed into the membrane by the absorption action and dissociates into hydrogen ions and hydroxide ions at the interface between the third anion exchange membrane 77 and the third cation exchange membrane 78. The hydroxide ions thus generated flow into the third chamber 83 through the third anion exchange membrane 77, and the hydrogen ions flow into the chamber 85 through the third cation exchange membrane 78.

[0053] Since the sulfate ions in the first chamber 81 move to the second chamber 82 and the ammonium ions move to the third chamber 83, the concentration of ammonium sulfate in the regenerated wastewater flowing into the first chamber 81 decreases. Therefore, from the first chamber 81, a diluted solution with a lower concentration of ammonium sulfate than the regenerated wastewater flowing into the first chamber 81 flows out, and the diluted solution is returned to the regenerated wastewater outflow line 7 via the diluted solution return line 62.

[0054] The operation of generating a regenerated acidic aqueous solution in the second chamber 82 is the same as that in Embodiment 2. In the third chamber 83, when ammonium ions move from the first chamber 81, the concentration of ammonium ions in the water in the third chamber 83 increases. As a result, aqueous ammonia flows out of the third chamber 83. A part of the aqueous ammonia flowing out of the third chamber 83 and flowing through the aqueous ammonia supply line 13 is supplied to the third chamber 83 via the aqueous ammonia return line 17.

[0055] Also in this modification, similar to Embodiment 1, by separating the regenerated acidic aqueous solution from the regeneration drainage of the desalting device 2 and reusing the regenerated acidic aqueous solution as at least a part of the acidic aqueous solution for the regeneration of the desalting device 2, the consumption amount of the acidic aqueous solution can be suppressed, so that the cost of the regeneration treatment of the desalting device 2 can be reduced. Further, since the diluent can be concentrated together with the regeneration drainage and then subjected to electrodialysis again, the separation amount of the regenerated acidic aqueous solution and ammonia water can be increased.

[0056] Also for this modification, as shown in FIG. 9, the cell 90 may include at least one repeating unit 300 between the second bipolar membrane 79 and the cathode 80. The configuration of the repeating unit 300 and the positions where the first chamber 81, the second chamber 82, and the third chamber 83 are respectively formed when the cell 90 includes the repeating unit 300 are the same as the configuration shown in FIG. 6.

[0057] In Embodiment 1, further, in the configuration of the drainage treatment system 1 shown in FIG. 1, instead of the bipolar membrane electrodialyzer 8, a different type of two-chamber bipolar membrane electrodialyzer described below can also be provided.

[0058] As shown in FIG. 10, this alternative two-chamber bipolar membrane electrodialyzer 100 includes an anode 101, a cathode 113, and a cell 110 provided between the anode 101 and the cathode 109. The cell 110 includes a first bipolar membrane 104 including a first anion exchange membrane 102 and a first cation exchange membrane 103 facing the anode 101, a second anion exchange membrane 105 facing the first cation exchange membrane 103, and a second bipolar membrane 108 including a third anion exchange membrane 106 and a second cation exchange membrane 107 facing the second anion exchange membrane 105. A first chamber 120 is formed by the second anion exchange membrane 105 and the third anion exchange membrane 106, and a second chamber 122 is formed by the first cation exchange membrane 103 and the second anion exchange membrane 105. The second chamber 122 is initially filled with an aqueous sulfuric acid solution. Each of the chamber 124 formed between the anode 101 and the first bipolar membrane 104 and the chamber 125 formed between the second bipolar membrane 108 and the cathode 109 is filled with an arbitrary electrode solution. As long as it is a membrane facing each of the anode 101 and the cathode 109, depending on the type of the electrode solution, instead of each of the first bipolar membrane 104 and the second bipolar membrane 108, either the first anion exchange membrane 102 or the first cation exchange membrane 103, and either the third anion exchange membrane 106 or the second cation exchange membrane 107 can be used.

[0059] The first chamber 120 communicates with both a regenerated drainage outflow line 7 and an aqueous ammonia supply line 13. That is, the first chamber 120 is configured such that regenerated drainage is supplied to the first chamber 120 via the regenerated drainage outflow line 7 and aqueous ammonia flows out of the first chamber 120 via the aqueous ammonia supply line 13. The second chamber 122 communicates with a regenerated acidic aqueous solution supply line 11. That is, the second chamber 122 is configured such that a regenerated acidic aqueous solution flows out of the second chamber 122 via the regenerated acidic aqueous solution supply line 11. Further, a regenerated acidic aqueous solution return line 19 branches from the regenerated acidic aqueous solution supply line 11, and the regenerated acidic aqueous solution return line 19 is connected to the second chamber 122. That is, a part of the regenerated acidic aqueous solution flowing through the regenerated acidic aqueous solution supply line 11 is configured to be supplied to the second chamber 122 via the regenerated acidic aqueous solution return line 19.

[0060] As shown in FIG. 11, the cell 110 may include a repeating unit 400 including a fourth anion exchange membrane 401 facing the second cation exchange membrane 107, and a third bipolar membrane 404 including a fifth anion exchange membrane 402 facing the fourth anion exchange membrane 401 and a third cation exchange membrane 403, between the second bipolar membrane 108 and the cathode 109. However, although FIG. 11 shows a configuration in which the cell 110 includes two repeating units 400, the present invention is not limited to this form. The cell 110 may include one repeating unit 400, or may include any number of three or more repeating units 400.

[0061] When the cell 110 includes one repeating unit 400, the first chamber 120 is formed by the fourth anion exchange membrane 401 and the third bipolar membrane 404, and the second chamber 122 is formed by the second bipolar membrane 108 and the fourth anion exchange membrane 401. When the cell 110 includes two or more repeating units 400, in each repeating unit 400, the first chamber 120 is formed by the fourth anion exchange membrane 401 and the third bipolar membrane 404, and the second chamber 122 is also formed by one of the third bipolar membranes 404 of two adjacent repeating units 400, 400 and the fourth anion exchange membrane 401 of the other of the two adjacent repeating units 400, 400.

[0062] As shown in Fig. 10, the regenerated drainage water flows into the first chamber 120 of the bipolar membrane electrodialyzer 100. By applying an electric current between the anode 101 and the cathode 109, the regenerated drainage water is electrodialyzed. The sulfate ions in the regenerated drainage water flowing into the first chamber 120 are attracted to the anode 101 and permeate through the second anion exchange membrane 105 to flow into the second chamber 122. Water is absorbed into the membranes by the absorption action in each of the first bipolar membrane 104 and the second bipolar membrane 108, and dissociates into hydrogen ions and hydroxide ions at the interfaces between the first anion exchange membrane 102 and the first cation exchange membrane 103, and between the third anion exchange membrane 106 and the second cation exchange membrane 107, respectively. The hydrogen ions thus generated flow into the second chamber 122 and the chamber 125 respectively through the first cation exchange membrane 103 and the second cation exchange membrane 107, and the hydroxide ions flow into the chamber 124 and the first chamber 120 respectively through the first anion exchange membrane 102 and the third anion exchange membrane 106.

[0063] The sulfate ions in the regenerated drainage water flowing into the first chamber 120 are attracted to the anode 101 and permeate through the second anion exchange membrane 105 to flow into the second chamber 122. The sulfate ions in the first chamber 120 move to the second chamber 122, and hydrogen ions flow into the second chamber 122 from the first bipolar membrane 104, so the concentration of sulfuric acid in the second chamber 122 increases. On the other hand, the ammonium ions in the regenerated drainage water flowing into the first chamber 120 remain in the first chamber 120, and hydroxide ions flow into the first chamber 120 from the second bipolar membrane 108, so the concentration of ammonia in the first chamber 120 increases. As a result, the concentration of ammonium sulfate decreases compared to the regenerated drainage water flowing into the first chamber 120, and an aqueous solution with an increased ammonia concentration, that is, ammonia water that may contain ammonium sulfate, flows out of the first chamber 120. From the second chamber 122, an aqueous sulfuric acid solution, that is, a regenerated acidic aqueous solution, flows out. A part of the regenerated acidic aqueous solution flowing out of the second chamber 122 is supplied to the second chamber 122 through the regenerated acidic aqueous solution return line 19.

[0064] However, in this modification, the aqueous ammonia flowing out from the first chamber 120 may have a low purity as aqueous ammonia due to the remaining ammonium sulfate in the regenerated drainage. Therefore, as shown in FIG. 12, instead of the aqueous ammonia storage tank 12 connected to the aqueous ammonia supply line 13, an ammonia stripper having the same configuration as the ammonia stripper 50 (see FIG. 3) provided in the wastewater treatment system 1 of Embodiment 2 may be connected to the aqueous ammonia supply line 13 to remove ammonia from the aqueous ammonia with low purity. In Embodiment 2, in order to enable the removal of ammonia by the ammonia stripper 50, an alkaline aqueous solution was supplied to the regenerated drainage for the purpose of adjusting the pH. However, in this modification, since the pH of the aqueous ammonia flowing out from the first chamber 120 is at least 11 or more, it is not necessary to supply an alkaline aqueous solution to the aqueous ammonia flowing out from the first chamber 120 for the purpose of adjusting the pH.

[0065] The content described in each of the above embodiments is understood as follows, for example.

[0066] [1] A wastewater treatment system according to one aspect is a wastewater treatment system (1) for treating regenerated wastewater generated by subjecting a desalting device (2) that desalts water containing ammonia to a regeneration treatment using an acidic aqueous solution, comprising a bipolar membrane electrodialyzer (8 / 18) that separates an aqueous solution containing the same acidic solute as the acidic aqueous solution as a regenerated acidic aqueous solution from the regenerated wastewater containing an ammonium salt generated by the reaction between the ammonia captured by the desalting device (2) and the acidic aqueous solution or a liquid derived from the regenerated wastewater, wherein the regenerated acidic aqueous solution is configured to be used for the regeneration of the desalting device (2) as at least a part of the acidic aqueous solution.

[0067] According to the wastewater treatment system of the present disclosure, by separating the regenerated acidic aqueous solution from the regenerated wastewater generated by regenerating the desalination device using the acidic aqueous solution or the liquid derived from the regenerated wastewater, and reusing the regenerated acidic aqueous solution as at least a part of the acidic aqueous solution for regenerating the desalination device, the consumption amount of the acidic aqueous solution can be suppressed, so that the cost of the regeneration treatment of the desalination device can be reduced.

[0068] [2] The wastewater treatment system according to another aspect is the wastewater treatment system of [1], and the bipolar membrane electrodialyzer (8) is an anode (21), a cathode (29), and a cell (30) provided between the anode (21) and the cathode (29). It is provided with The cell (30) is a first bipolar membrane (24) including a first anion exchange membrane (22) and a first cation exchange membrane (23), a second cation exchange membrane (25) facing the first cation exchange membrane (23), and a second bipolar membrane (28) including a second anion exchange membrane (26) and a third cation exchange membrane (27) facing the second cation exchange membrane (25). It is provided with The regenerated wastewater is supplied to a first chamber (31) defined by the first bipolar membrane (24) and the second cation exchange membrane (25), and the regenerated acidic aqueous solution is configured to flow out of the first chamber (31).

[0069] According to such a configuration, by separating the regenerated acidic aqueous solution from the regenerated wastewater generated by regenerating the desalination device using the acidic aqueous solution, and reusing the regenerated acidic aqueous solution as at least a part of the acidic aqueous solution for regenerating the desalination device, the consumption amount of the acidic aqueous solution can be suppressed, so that the cost of the regeneration treatment of the desalination device can be reduced.

[0070] [3] The wastewater treatment system according to still another aspect is the wastewater treatment system of [2], and The cell (30) includes at least one repeating unit (200) including a fourth cation exchange membrane (201) facing the third cation exchange membrane (27), a third anion exchange membrane (202) facing the fourth cation exchange membrane (201), and a fifth cation exchange membrane (203) between the second bipolar membrane (28) and the cathode (29). The first chamber (31) is defined by the second bipolar membrane (28) and the fourth cation exchange membrane (201).

[0071] According to such a configuration, since the capacity of the cell of the bipolar membrane electrodialyzer increases, the efficiency of electrodialysis increases, so that the cost of the regeneration treatment of the desalination device can be reduced.

[0072] [4] A wastewater treatment system according to still another aspect is the wastewater treatment system of [3], including at least two repeating units (200), and the first chamber (31) is defined by one of the third bipolar membranes (204) of two adjacent repeating units (200, 200) and the fourth cation exchange membrane (201) of the other of the two adjacent repeating units (200, 200).

[0073] According to such a configuration, since the capacity of the cell of the bipolar membrane electrodialyzer increases, the efficiency of electrodialysis increases, so that the cost of the regeneration treatment of the desalination device can be reduced.

[0074] [5] A wastewater treatment system according to still another aspect is the wastewater treatment system of [1], wherein the bipolar membrane electrodialyzer (100) includes an anode (101), a cathode (109), and a cell (110) provided between the anode (101) and the cathode (109), and the cell (110) A first bipolar membrane (104) including a first anion exchange membrane (102) and a first cation exchange membrane (103); a second anion exchange membrane (105) facing the first cation exchange membrane (103); a second bipolar membrane (108) including a third anion exchange membrane (106) and a second cation exchange membrane (107) facing the second anion exchange membrane (105); and is provided with; the regenerated drainage water is supplied to a first chamber (120) defined by the second anion exchange membrane (105) and the third anion exchange membrane (106), and the regenerated acidic aqueous solution flows out from a second chamber (122) defined by the first cation exchange membrane (103) and the second anion exchange membrane (105).

[0075] According to such a configuration, the regenerated acidic aqueous solution is separated from the regenerated drainage water generated by regenerating the desalination device using the acidic aqueous solution, and the regenerated acidic aqueous solution is reused as at least a part of the acidic aqueous solution for regenerating the desalination device, so that the consumption amount of the acidic aqueous solution can be suppressed, and thus the cost of the regeneration treatment of the desalination device can be reduced.

[0076] [6] A drainage treatment system according to still another aspect is the drainage treatment system of [5], wherein the cell (110) includes at least one repeating unit (400) including a fourth anion exchange membrane (401) facing the second cation exchange membrane (107) and a third bipolar membrane (404) including a fifth anion exchange membrane (402) and a third cation exchange membrane (403) facing the fourth anion exchange membrane (401) between the second bipolar membrane (108) and the cathode (109); the first chamber (120) is defined by the fourth anion exchange membrane (401) and the third bipolar membrane (404), and the second chamber (122) is defined by the second bipolar membrane (108) and the fourth anion exchange membrane (401).

[0077] According to such a configuration, since the capacity of the cell of the bipolar membrane electrodialyzer increases, the efficiency of electrodialysis increases, so that the cost of the regeneration treatment of the desalting device can be reduced.

[0078] [7] A wastewater treatment system according to still another aspect is the wastewater treatment system of [6], wherein at least two of the repeating units (400) are provided, and the first chamber (120) is defined by the fourth anion exchange membrane (401) and the third bipolar membrane (404) in each of the repeating units (400), and one of the third bipolar membranes (404) of two adjacent repeating units (400, 400) and the fourth anion exchange membrane (401) of the other of the two adjacent repeating units (400, 400) define the second chamber (122).

[0079] According to such a configuration, since the capacity of the cell of the bipolar membrane electrodialyzer increases, the efficiency of electrodialysis increases, so that the cost of the regeneration treatment of the desalting device can be reduced.

[0080] [8] A wastewater treatment system according to still another aspect is the wastewater treatment system according to any one of [5] to [7], wherein the bipolar membrane electrodialyzer (100) is configured such that aqueous ammonia flows out from the first chamber (120), the wastewater treatment system (1) further includes an ammonia stripper (50) that separates ammonia from the aqueous ammonia flowing out from the first chamber (120).

[0081] According to such a configuration, when the purity of the aqueous ammonia flowing out from each of the first chamber and the second chamber is low, it can be treated as waste liquid without being used in a boiler, a denitration device, or the like.

[0082] [9] A wastewater treatment system according to still another aspect is the wastewater treatment system of [1], wherein the bipolar membrane electrodialyzer (18) has an anode (71), a cathode (80), a cell (90) provided between the anode (71) and the cathode (80), and is provided with the cell (90) includes a first bipolar membrane (74) including a first anion exchange membrane (72) and a first cation exchange membrane (73); a second anion exchange membrane (75) facing the first cation exchange membrane (73); a second cation exchange membrane (76) facing the second anion exchange membrane (75); a second bipolar membrane (79) including a third anion exchange membrane (77) and a third cation exchange membrane (78) facing the second cation exchange membrane (76), and is provided with the regenerated drainage water is supplied to a first chamber (81) defined by the second anion exchange membrane (75) and the second cation exchange membrane (76), and the regenerated acidic aqueous solution flows out from a second chamber (82) defined by the first bipolar membrane (74) and the second anion exchange membrane (75).

[0083] According to such a configuration, the regenerated acidic aqueous solution is separated from the regenerated drainage water generated by regenerating the desalination device using the acidic aqueous solution, and the regenerated acidic aqueous solution is reused as at least a part of the acidic aqueous solution for regenerating the desalination device, so that the consumption amount of the acidic aqueous solution can be suppressed, and the cost of the regeneration treatment of the desalination device can be reduced.

[0084]

[10] A wastewater treatment system according to still another aspect is the wastewater treatment system of [9], wherein the cell (90) includes at least one repeating unit (300) between the second bipolar membrane (79) and the cathode (80), the repeating unit (300) including a fourth anion exchange membrane (301) facing the third cation exchange membrane (78), a fourth cation exchange membrane (302) facing the fourth anion exchange membrane (301), and a third bipolar membrane (305) including a fifth anion exchange membrane (303) and a fifth cation exchange membrane (304) facing the fourth cation exchange membrane (302). The first chamber (81) is defined by the fourth anion exchange membrane (301) and the fourth cation exchange membrane (302), and the second chamber (82) is defined by the second bipolar membrane (79) and the fourth anion exchange membrane (301).

[0085] According to such a configuration, since the capacity of the cell of the bipolar membrane electrodialyzer increases, the efficiency of electrodialysis increases, so that the cost of the regeneration treatment of the desalting device can be reduced.

[0086]

[11] A wastewater treatment system according to still another aspect is the wastewater treatment system of

[10] , including at least two of the repeating units (300). In each of the repeating units (300), the first chamber (81) is defined by the fourth anion exchange membrane (301) and the fourth cation exchange membrane (302). The second chamber (82) is defined by one of the third bipolar membranes (305) of two adjacent repeating units (300, 300) and the fourth anion exchange membrane (301) of the other of the two adjacent repeating units (300, 300).

[0087] According to such a configuration, since the capacity of the cell of the bipolar membrane electrodialyzer increases, the efficiency of electrodialysis increases, so that the cost of the regeneration treatment of the desalting device can be reduced.

[0088]

[12] A wastewater treatment system according to still another aspect is the wastewater treatment system of any one of [1] to [8], further comprising a concentrator (14) for concentrating the ammonium salt with respect to the regenerated wastewater before flowing into the bipolar membrane electrodialyzer (8).

[0089] When the concentration of the ammonium salt in the regenerated wastewater is low, the separation efficiency of the regenerated acidic aqueous solution by electrodialysis decreases. However, according to the configuration of [6] above, since electrodialysis can be performed on the regenerated wastewater with an increased concentration of the ammonium salt, the separation efficiency of the regenerated acidic aqueous solution by electrodialysis can be increased.

[0090]

[13] A wastewater treatment system according to still another aspect is any one of the wastewater treatment systems of [9] to

[11] , and the bipolar membrane electrodialyzer (18) is configured such that aqueous ammonia flows out from a third chamber (83) defined by the second cation exchange membrane (76) and the second bipolar membrane (79), and a diluent, which is the remaining component from which the regenerated acidic aqueous solution and the aqueous ammonia are separated from the regenerated wastewater, flows out from the first chamber (81), the wastewater treatment system (1) includes a concentrator (14) that concentrates the ammonium salt in the regenerated wastewater before it flows into the bipolar membrane electrodialyzer (18), and a diluent return line (62) that supplies the diluent flowing out from the first chamber (81) to the regenerated wastewater before it flows into the concentrator (14). The wastewater treatment system further includes the above components.

[0091] According to such a configuration, since the diluent can be concentrated together with the regenerated wastewater and then subjected to electrodialysis again, the separation amount of the regenerated acidic aqueous solution and the regenerated alkaline aqueous solution can be increased compared to the case where the diluent is not supplied to the regenerated wastewater before it flows into the concentrator.

[0092]

[14] A wastewater treatment system according to still another aspect is the wastewater treatment system of [1], and includes a supply device (40) that supplies an alkaline aqueous solution containing an alkali metal hydroxide to the regenerated wastewater, and an ammonia stripper (50) that separates ammonia from the regenerated wastewater to which the alkaline aqueous solution has been supplied. The wastewater treatment system includes the above components. The liquid derived from the regenerated wastewater is the drain liquid of the ammonia stripper, and the bipolar membrane electrodialyzer (18) separates, from the drain liquid, a regenerated acidic aqueous solution and a regenerated alkaline aqueous solution as an aqueous solution containing the same solute as the alkaline aqueous solution, and the regenerated alkaline aqueous solution is configured to be supplied to the regenerated wastewater as at least a part of the alkaline aqueous solution.

[0093] According to such a configuration, after supplying an alkaline aqueous solution to the regeneration drainage water generated by regenerating the desalination device using an acidic aqueous solution and separating ammonia with an ammonia stripper, the regenerated acidic aqueous solution and the regenerated alkaline aqueous solution are separated from the drainage liquid of the ammonia stripper, and the regenerated acidic aqueous solution is reused as at least a part of the acidic aqueous solution for regenerating the desalination device, and the regenerated alkaline aqueous solution is supplied to the regeneration drainage water as at least a part of the alkaline aqueous solution, so that the consumption amounts of the acidic aqueous solution and the alkaline aqueous solution can be suppressed, and thus the cost of the regeneration treatment of the desalination device can be reduced.

[0094]

[15] A wastewater treatment system according to still another aspect is the wastewater treatment system of

[14] , wherein the bipolar membrane electrodialyzer (18) is provided with an anode (71), a cathode (80), and a cell (90) provided between the anode (71) and the cathode (80). The cell (90) includes a first bipolar membrane (74) including a first anion exchange membrane (72) and a first cation exchange membrane (73), a second anion exchange membrane (75) facing the first cation exchange membrane (73), a second cation exchange membrane (76) facing the second anion exchange membrane (75), a third anion exchange membrane (77) and a third cation exchange membrane (78) facing the second cation exchange membrane (76) and including a second bipolar membrane (79). The drainage liquid is supplied to a first chamber (81) defined by the second anion exchange membrane (75) and the second cation exchange membrane (76), the regenerated acidic aqueous solution flows out from a second chamber (82) defined by the first bipolar membrane (74) and the second anion exchange membrane (75), and the regenerated alkaline aqueous solution flows out from a third chamber (83) defined by the second cation exchange membrane (76) and the second bipolar membrane (79). The wastewater treatment system is configured as described above. ​

[0095] According to such a configuration, after supplying an alkaline aqueous solution to the regeneration drainage water generated by regenerating the desalination device using an acidic aqueous solution and separating ammonia with an ammonia stripper, a regenerated acidic aqueous solution and a regenerated alkaline aqueous solution are separated from the drainage liquid of the ammonia stripper. Then, the regenerated acidic aqueous solution is reused as at least a part of the acidic aqueous solution for regenerating the desalination device, and the regenerated alkaline aqueous solution is supplied to the regeneration drainage water as at least a part of the alkaline aqueous solution. As a result, the consumption amounts of the acidic aqueous solution and the alkaline aqueous solution can be suppressed, so that the cost of the regeneration treatment of the desalination device can be reduced.

[0096]

[16] A wastewater treatment system according to still another aspect is the wastewater treatment system of

[15] , wherein the cell (90) includes at least one repeating unit (300) including a fourth anion exchange membrane (301) facing the third cation exchange membrane (78), a fourth cation exchange membrane (302) facing the fourth anion exchange membrane (301), and a third bipolar membrane (305) including a fifth anion exchange membrane (303) and a fifth cation exchange membrane (304) facing the fourth cation exchange membrane (302) between the second bipolar membrane (79) and the cathode (80). The first chamber (81) is defined by the fourth anion exchange membrane (301) and the fourth cation exchange membrane (302), the second chamber (82) is defined by the second bipolar membrane (79) and the fourth anion exchange membrane (301), and the third chamber (83) is defined by the fourth cation exchange membrane (302) and the third bipolar membrane (305).

[0097] According to such a configuration, since the capacity of the cell of the bipolar membrane electrodialyzer increases, the efficiency of electrodialysis increases, so that the cost of the regeneration treatment of the desalination device can be reduced.

[0098]

[17] A wastewater treatment system according to still another aspect is the wastewater treatment system of

[16] , wherein comprising at least two of the repeating units (300), wherein the first chamber (81) is defined by the fourth anion exchange membrane (301) and the fourth cation exchange membrane (302) in each of the repeating units (300), and the second chamber (82) is defined by one of the third bipolar membranes (305) of two adjacent repeating units (300, 300) and the fourth anion exchange membrane (301) of the other of the two adjacent repeating units (300, 300), and the third chamber (83) is defined by the fourth cation exchange membrane (302) and the third bipolar membrane (305) in each of the repeating units (300).

[0099] According to such a configuration, since the capacity of the cell of the bipolar membrane electrodialyzer increases, the efficiency of electrodialysis increases, so that the cost of the regeneration treatment of the desalting device can be reduced.

[0100]

[18] A wastewater treatment system according to still another aspect is the wastewater treatment system according to any one of

[14] to

[17] , further comprising a concentrator (14) for concentrating the salt of the alkali metal generated by the reaction between the ammonium salt contained in the regenerated wastewater and the hydroxide of the alkali metal contained in the alkaline aqueous solution with respect to the wastewater before flowing into the bipolar membrane electrodialyzer (18).

[0101] When the concentration of the salt of the alkali metal in the drainage of the ammonia stripper is low, the separation efficiency of the regenerated acidic aqueous solution and the regenerated alkaline aqueous solution by electrodialysis decreases. However, according to the configuration of

[18] above, since electrodialysis can be performed on the drainage with an increased concentration of the salt of the alkali metal, the separation efficiency of the regenerated acidic aqueous solution and the alkaline aqueous solution by electrodialysis can be increased.

[0102]

[19] A wastewater treatment system according to still another aspect is the wastewater treatment system according to

[18] , A dilution liquid return line (62) is further provided, which supplies a dilution liquid, which is the remaining component after separating the acidic aqueous solution and the alkaline aqueous solution from the drainage liquid, to the drainage liquid before flowing into the concentrator (14).

[0103] According to such a configuration, since the dilution liquid can be concentrated together with the drainage liquid and then electrodialyzed again, the separation amount of the regenerated acidic aqueous solution and the regenerated alkaline aqueous solution can be increased as compared with the case where the dilution liquid is not supplied to the drainage liquid before flowing into the concentrator.

[0104]

[20] A wastewater treatment system according to still another aspect is any one of the wastewater treatment systems of [1] to

[19] , The water containing ammonia is the condensate of the boiler.

[0105] According to the wastewater treatment system of the present disclosure, the regenerated acidic aqueous solution is separated from the regenerated wastewater generated by subjecting a desalination device for desalinating the condensate of a boiler containing ammonia to a regeneration treatment using an acidic aqueous solution or a liquid derived from the regenerated wastewater, and the regenerated acidic aqueous solution is reused as at least a part of the acidic aqueous solution for the regeneration of the desalination device, so that the consumption amount of the acidic aqueous solution can be suppressed, and thus the cost of the regeneration treatment of the desalination device can be reduced.

Explanation of symbols

[0106] 1 Wastewater treatment system 2 Desalination device 8 Bipolar membrane electrodialyzer 14 Concentrator 18 Bipolar membrane electrodialyzer 21 Anode 22 First anion exchange membrane 23 First cation exchange membrane 24 First bipolar membrane 25 Second cation exchange membrane 26 Second anion exchange membrane 27 Third cation exchange membrane 28 Second bipolar membrane 29 Cathode 30 Cell 31 Chamber 1 40 Supply device 50 Ammonia stripper 62 Diluent return line 71 Anode 72 First anion exchange membrane 73 First cation exchange membrane 74 First bipolar membrane 75 Second anion exchange membrane 76 Second cation exchange membrane 77 Third anion exchange membrane 78 Third cation exchange membrane 79 Second bipolar membrane 80 Cathode 81 Chamber 1 82 Chamber 2 83 Chamber 3 90 Cell 100 Bipolar membrane electrodialyzer 101 Anode 102 First anion exchange membrane 103 First cation exchange membrane 104 First bipolar membrane 105 Second anion exchange membrane 106 Third anion exchange membrane 107 Second cation exchange membrane 108 Second bipolar membrane 109 Cathode 110 Cell 120 Chamber 1 122 Chamber 2 200 Repeating unit 201 Fourth cation exchange membrane 202 Third anion exchange membrane 203 Fifth cation exchange membrane 204 Third bipolar membrane 300 Repeating unit 301 Fourth anion exchange membrane 302 Fourth cation exchange membrane 303 Fifth anion exchange membrane 304 Fifth cation exchange membrane 305 Third bipolar membrane 400 Repeating unit 401 Fourth anion exchange membrane 402 Fifth anion exchange membrane 403 Third cation exchange membrane 404 Third bipolar membrane

Claims

1. A wastewater treatment system for treating the regenerated wastewater generated by subjecting a desalination device that desalinates water containing ammonia to a regeneration treatment using an acidic aqueous solution, comprising: a bipolar membrane electrodialyzer that separates an aqueous solution containing the same acidic solute as the acidic aqueous solution as a regenerated acidic aqueous solution from the regenerated wastewater containing an ammonium salt generated by the reaction between the ammonia captured by the desalination device and the acidic aqueous solution, or a liquid derived from the regenerated wastewater; an acidic aqueous solution tank for storing the acidic aqueous solution; an acidic aqueous solution supply line that communicates the acidic aqueous solution tank and the desalination device; a regenerated wastewater outflow line that communicates the desalination device and the bipolar membrane electrodialyzer; a regenerated acidic aqueous solution supply line that communicates the bipolar membrane electrodialyzer and the acidic aqueous solution tank; and the regenerated acidic aqueous solution is configured to be used for regenerating the desalination device by being supplied to the acidic aqueous solution tank via the regenerated acidic aqueous solution supply line and supplied to the desalination device via the acidic aqueous solution supply line as at least a part of the acidic aqueous solution.

2. The bipolar membrane electrodialyzer comprises: an anode; a cathode; and a cell provided between the anode and the cathode. The cell comprises: a first bipolar membrane including a first anion exchange membrane and a first cation exchange membrane; a second cation exchange membrane facing the first cation exchange membrane; and a second bipolar membrane including a second anion exchange membrane and a third cation exchange membrane facing the second cation exchange membrane. At least one first chamber is defined within the cell for supplying the regenerated wastewater and discharging the regenerated acidic aqueous solution, and one of the at least one first chambers is defined by the first bipolar membrane and the second cation exchange membrane. The wastewater treatment system according to claim 1.

3. The cell further comprises at least one repeating unit including a fourth cation exchange membrane facing the third cation exchange membrane and a third bipolar membrane including a third anion exchange membrane and a fifth cation exchange membrane facing the fourth cation exchange membrane between the second bipolar membrane and the cathode, and one of the at least one first chambers is further defined by the second bipolar membrane and the fourth cation exchange membrane. The wastewater treatment system according to claim 2.

4. ​ ​ The wastewater treatment system according to claim 3, comprising at least two of the repeating units, wherein one of the at least one first chamber is further defined by the third bipolar membrane of two adjacent repeating units and the fourth cation exchange membrane of the other of the two adjacent repeating units.

5. The bipolar membrane electrodialyzer includes an anode, a cathode, and a cell provided between the anode and the cathode, wherein the cell includes a first bipolar membrane including a first anion exchange membrane and a first cation exchange membrane, a second anion exchange membrane facing the first cation exchange membrane, and a second bipolar membrane including a third anion exchange membrane facing the second anion exchange membrane and a second cation exchange membrane. One or more first chambers into which the regenerated wastewater is supplied and one or more second chambers from which the regenerated acidic aqueous solution flows out are defined within the cell. One of the at least one first chambers is defined by the second anion exchange membrane and the third anion exchange membrane, and one of the at least one second chambers is defined by the first cation exchange membrane and the second anion exchange membrane. The wastewater treatment system according to claim 1.

6. The cell includes at least one repeating unit including a fourth anion exchange membrane facing the second cation exchange membrane and a third bipolar membrane including a fifth anion exchange membrane facing the fourth anion exchange membrane and a third cation exchange membrane between the second bipolar membrane and the cathode. One of the at least one first chambers is further defined by the fourth anion exchange membrane and the third bipolar membrane, and one of the at least one second chambers is further defined by the second bipolar membrane and the fourth anion exchange membrane. The wastewater treatment system according to claim 5.

7. The wastewater treatment system according to claim 6, comprising at least two of the repeating units, wherein one of the at least one first chambers is further defined by the fourth anion exchange membrane and the third bipolar membrane in each of the repeating units, and one of the at least one second chambers is further defined by the third bipolar membrane of one of two adjacent repeating units and the fourth anion exchange membrane of the other of the two adjacent repeating units.

8. ​ ​ The bipolar membrane electrodialyzer is configured such that aqueous ammonia flows out from the at least one first chamber. The wastewater treatment system according to any one of claims 5 to 7, further comprising an ammonia stripper that separates ammonia from the aqueous ammonia flowing out from the at least one first chamber.

9. The bipolar membrane electrodialyzer comprises an anode, a cathode, and a cell provided between the anode and the cathode. The cell comprises a first bipolar membrane including a first anion exchange membrane and a first cation exchange membrane, a second anion exchange membrane facing the first cation exchange membrane, a second cation exchange membrane facing the second anion exchange membrane, and a second bipolar membrane including a third anion exchange membrane and a third cation exchange membrane facing the second cation exchange membrane. In the cell, at least one first chamber into which the regenerated wastewater is supplied and at least one second chamber from which the regenerated acidic aqueous solution flows out are defined. The wastewater treatment system according to claim 1, wherein one of the at least one first chambers is defined by the second anion exchange membrane and the second cation exchange membrane, and one of the at least one second chambers is defined by the first bipolar membrane and the second anion exchange membrane.

10. The cell includes at least one repeating unit including a fourth anion exchange membrane facing the third cation exchange membrane, a fourth cation exchange membrane facing the fourth anion exchange membrane, and a third bipolar membrane including a fifth anion exchange membrane and a fifth cation exchange membrane facing the fourth cation exchange membrane, between the second bipolar membrane and the cathode. The wastewater treatment system according to claim 9, wherein one of the at least one first chambers is further defined by the fourth anion exchange membrane and the fourth cation exchange membrane, and one of the at least one second chambers is further defined by the second bipolar membrane and the fourth anion exchange membrane.

11. Comprising at least two of the repeating units, one of the at least one first chamber is further defined by the fourth anion exchange membrane and the fourth cation exchange membrane in each of the repeating units, and one of the third bipolar membranes of two adjacent repeating units and the fourth anion exchange membrane of the other of the two adjacent repeating units further define one of the at least one second chamber. The wastewater treatment system according to claim 10.

12. The wastewater treatment system according to any one of claims 1 to 8, further comprising a concentrator for concentrating the ammonium salt in the regenerated wastewater before flowing into the bipolar membrane electrodialyzer.

13. The bipolar membrane electrodialyzer is configured such that ammonia water flows out from a third chamber defined by the second cation exchange membrane and the second bipolar membrane, and a diluent, which is the remaining component from which the regenerated acidic aqueous solution and the ammonia water are separated from the regenerated wastewater, flows out from the at least one first chamber. The wastewater treatment system a concentrator for concentrating the ammonium salt in the regenerated wastewater before flowing into the bipolar membrane electrodialyzer, and a diluent return line for supplying the diluent flowing out from the at least one first chamber to the regenerated wastewater before flowing into the concentrator The wastewater treatment system according to any one of claims 9 to 11, further comprising.

14. a supply device for supplying an alkaline aqueous solution containing an alkali metal hydroxide to the regenerated wastewater, and an ammonia stripper for separating ammonia from the regenerated wastewater to which the alkaline aqueous solution has been supplied comprising the liquid derived from the regenerated wastewater is the drain liquid of the ammonia stripper, and the bipolar membrane electrodialyzer separates, from the drain liquid, a regenerated acidic aqueous solution and a regenerated alkaline aqueous solution as an aqueous solution containing the same solute as the alkaline aqueous solution, and the regenerated alkaline aqueous solution is configured to be supplied to the regenerated wastewater as at least a part of the alkaline aqueous solution. The wastewater treatment system according to claim 1.

15. The bipolar membrane electrodialyzer an anode, a cathode, and a cell provided between the anode and the cathode comprising The cell a first bipolar membrane including a first anion exchange membrane and a first cation exchange membrane, a second anion exchange membrane facing the first cation exchange membrane; a second cation exchange membrane facing the second anion exchange membrane; a second bipolar membrane including a third anion exchange membrane and a third cation exchange membrane facing the second cation exchange membrane; and comprising; in the cell, at least one first chamber into which the regenerated drainage water is supplied, at least one second chamber from which the regenerated acidic aqueous solution flows out, and at least one third chamber from which the regenerated alkaline aqueous solution flows out are defined; one of the at least one first chambers is defined by the second anion exchange membrane and the second cation exchange membrane, one of the at least one second chambers is defined by the first bipolar membrane and the second anion exchange membrane, and one of the at least one third chambers is defined by the second cation exchange membrane and the second bipolar membrane. The wastewater treatment system according to claim 14.

16. The cell includes at least one repeating unit between the second bipolar membrane and the cathode, the repeating unit including a fourth anion exchange membrane facing the third cation exchange membrane, a fourth cation exchange membrane facing the fourth anion exchange membrane, and a third bipolar membrane including a fifth anion exchange membrane and a fifth cation exchange membrane facing the fourth cation exchange membrane; one of the at least one first chambers is further defined by the fourth anion exchange membrane and the fourth cation exchange membrane, one of the at least one second chambers is further defined by the second bipolar membrane and the fourth anion exchange membrane, and one of the at least one third chambers is further defined by the fourth cation exchange membrane and the third bipolar membrane. The wastewater treatment system according to claim 15.

17. The cell includes at least two repeating units. In each of the repeating units, one of the at least one first chambers is further defined by the fourth anion exchange membrane and the fourth cation exchange membrane. One of the at least one second chambers is further defined by one of the third bipolar membranes of two adjacent repeating units and the fourth anion exchange membrane of the other of the two adjacent repeating units. In each of the repeating units, one of the at least one third chambers is further defined by the fourth cation exchange membrane and the third bipolar membrane. The wastewater treatment system according to claim 16.

18. A drainage treatment system according to any one of claims 14 to 17, further comprising a concentrator configured to concentrate a salt of an alkali metal produced by a reaction between the ammonium salt contained in the regeneration drainage water and the hydroxide of the alkali metal contained in the alkaline aqueous solution, with respect to the drainage water before flowing into the bipolar membrane electrodialyzer.

19. The drainage treatment system according to claim 18, further comprising a dilution liquid return line configured to supply a dilution liquid, which is a remaining component from which the acidic aqueous solution and the alkaline aqueous solution have been separated from the drainage water, to the drainage water before flowing into the concentrator.

20. The drainage treatment system according to any one of claims 1 to 19, wherein the water containing ammonia is condensate water of a boiler.

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