JP2019135054A - Water treatment device and water treatment method - Google Patents

Abstract

To provide a water treatment device capable of suppressing a deterioration of quality of treated water while suppressing a decrease in the amount of treated water and generation of scale.SOLUTION: A plurality of electric deionized water production apparatuses each have include, between an anode and a cathode: a demineralized chamber which is partitioned by a first anion exchange membrane located on the anode side and a cation exchange membrane located on the cathode side and filled with an ion exchanger; a first concentration chamber adjacent to the demineralized chamber via the cation exchange membrane and having a cathode side partitioned by a second anion exchange membrane; and a second concentration chamber adjacent to the demineralized chamber via the first anion exchange membrane. The demineralization chambers of the respective electric deionized water production apparatuses communicate in series, and treating target water is passed therethrough and flowed out as treated water. The anion exchanger is charged into the first concentration chamber adjacent to the first-stage demineralizing chamber through which the treating target water is first passed, and in the first concentration chamber adjacent to the last stage demineralizing chamber through which the treated water flows out via the cation exchange membrane, the cation exchanger is charged alone into the cathode side of the cation exchange membrane, and the anion exchanger is charged alone into the other regions.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a water treatment apparatus and a water treatment method, and more particularly to a water treatment apparatus and a water treatment method using an electric deionized water production apparatus.

2. Description of the Related Art A deionized water production apparatus is known in which water to be treated is passed through an ion exchanger such as an ion exchange resin and deionized by an ion exchange reaction. Such an apparatus needs to perform a process (regeneration process) of regenerating the ion exchanger with a chemical such as acid or alkali when the ion exchange group of the ion exchanger is saturated and the desalting performance is lowered. In the regeneration process, cations (cations) and anions (anions) adsorbed on the ion exchanger are replaced with hydrogen ions (H ⁺ ) or hydroxide ions (OH ⁻ ) derived from acids or alkalis. This process restores the desalination performance of the exchanger. A deionized water production apparatus that requires a regeneration process with a drug cannot perform continuous operation, and has a problem that it takes time to replenish the drug for the regeneration process.

  In recent years, as a solution to these problems, an electric deionized water production apparatus (also referred to as an EDI (Electro DeIonization) apparatus) that does not require regeneration treatment with a drug has been developed and put into practical use.

  The EDI device is a device that combines electrophoresis and electrodialysis. The EDI apparatus includes a desalting chamber filled with an ion exchanger (anion exchanger and / or cation exchanger) between an anion exchange membrane that allows only anions to pass therethrough and a cation exchange membrane that allows only cations to pass through. In the EDI apparatus, a concentration chamber is disposed outside each of the anion exchange membrane and the cation exchange membrane as viewed from the desalting chamber. And a desalination chamber and each concentration chamber are arrange | positioned between the anode chamber provided with an anode, and the cathode chamber provided with the cathode. In the desalting chamber, an anion exchange membrane is disposed on the side close to the anode, and a cation exchange membrane is disposed on the side close to the cathode. The concentration chamber adjacent to the desalting chamber via the anion exchange membrane is adjacent to the anode chamber via the cation exchange membrane. The concentration chamber adjacent to the desalting chamber via the cation exchange membrane is adjacent to the cathode chamber via the anion exchange membrane.

In order to produce deionized water (treated water) from the treated water by the EDI apparatus, the treated water is passed through the desalting chamber in a state where a DC voltage is applied between the anode and the cathode. Then, the ionic component in the for-treatment water is adsorbed by the ion exchanger in the demineralization chamber and subjected to deionization (demineralization) treatment, and deionized water flows out from the demineralization chamber. At this time, in the desalination chamber, an interface between different ion exchange materials, for example, an anion exchanger and a cation exchanger, an anion exchanger and a cation exchange membrane, an anion exchange membrane, At the interface with the cation exchanger, a water dissociation reaction occurs as shown in the following formula, and hydrogen ions and hydroxide ions are generated.
H ₂ O → H ⁺ + OH ⁻
By this hydrogen ion and hydroxide ion, the ion component previously adsorbed on the ion exchanger in the desalting chamber is ion-exchanged and released from the ion exchanger. Of the released ionic components, the anion is electrophoresed to the anion exchange membrane, electrodialyzed on the anion exchange membrane, and discharged to the concentrated water flowing through the concentration chamber on the anode side as viewed from the desalting chamber. Similarly, cations out of the free ionic components are electrophoresed to the cation exchange membrane, electrodialyzed on the cation exchange membrane, and discharged to the concentrated water flowing through the cathode-side concentration chamber as viewed from the desalting chamber. Eventually, the ion component in the for-treatment water supplied to the desalting chamber is transferred to the concentration chamber and discharged, and at the same time, the ion exchanger in the desalting chamber is also regenerated.
In this way, in the EDI apparatus, hydrogen ions and hydroxide ions generated by application of a DC voltage continuously act as acid and alkali regenerants for regenerating the ion exchanger. For this reason, in the EDI apparatus, the regeneration process using the medicine supplied from the outside is basically unnecessary, and the continuous operation can be performed without the regeneration of the ion exchanger by the medicine.

However, when the EDI apparatus is continuously operated, hardness components in the water to be treated are deposited, and scales such as calcium hydroxide and magnesium hydroxide are generated. The reason is as follows.
When hydroxide ions generated by electrolysis in the cathode chamber pass through the anion exchange membrane in the cathode-side concentration chamber, the surface on the concentration chamber side of the anion exchange membrane becomes alkaline. Then, the hardness component ions (magnesium ions Mg ²⁺ and calcium ions Ca ²⁺ ) that have passed through the cation exchange membrane from the desalting chamber and moved to the concentrating chamber on the cathode side are converted to alkaline at the surface of the anion exchange membrane. Reacts to produce scales such as magnesium hydroxide and calcium hydroxide.
When the scale is generated, the electrical resistance in the scale generating portion increases, and it becomes difficult for the current to flow to the EDI device. Therefore, in order to obtain the same current value as when no scale is generated, it is necessary to increase the applied voltage, resulting in an increase in power consumption. In addition, the current density in the concentration chamber may be non-uniform. As the amount of scale further increases, the water flow differential pressure increases and the electrical resistance further increases. In this case, an amount of current necessary for ion removal cannot flow, and the quality of the treated water is deteriorated.

As one of the methods for suppressing the generation of scale, Patent Document 1 describes a method of filling an anion exchanger in a concentration chamber.
When the anion exchanger is filled in the concentration chamber, diffusion dilution of hydroxide ions present on the surface of the anion exchange membrane in the concentration chamber on the cathode side into the concentrated water is promoted by the anion exchanger in the concentration chamber, The hydroxide ion concentration on the anion exchange membrane surface is rapidly reduced. On the other hand, hardness component ions are difficult to reach the anion exchange membrane surface due to the presence of the anion exchanger in the concentration chamber. As a result, the opportunity for the hydroxide ions and the hardness component ions to contact and react with each other is reduced, and the generation of scale is suppressed.

  However, when the anion exchanger is filled in the concentration chamber, the weak acid anion component typified by carbonic acid or silica contained in the concentrated water diffuses into the treated water through the cation exchange membrane that separates the concentration chamber and the desalting chamber. Causes the problem of reducing the purity of the treated water. Hereinafter, this problem will be described by taking carbon dioxide and silica as an example.

Generally, a cation exchange membrane is an ion exchange membrane that selectively permeates only cations. The principle is that the cation exchange membrane itself has a negative charge, and a repulsive force acts on the negatively charged anion to block the permeation.
On the other hand, carbonic acid (carbon dioxide) and silica take the form of the following ionic species in an aqueous solution, and they are in an equilibrium state.
CO ₂ ⇔HCO ₃ ^- ⇔CO ₃ ^2-
SiO ₂ ⇔Si (OH) ₄ ⇔Si (OH) ₃ O ⁻
The proportion of each ionic species in the entire equilibrium state as described above varies greatly depending on the pH. In the region where the pH is low, most of carbonic acid and silica are not ionized, that is, exist as CO ₂ and SiO _{2 in a} state having no charge.
The cation exchange membrane that divides the desalting chamber and the concentration chamber allows a large amount of hydrogen ions (H ⁺ ) generated by the water dissociation reaction together with the cation component in the water to be treated to pass from the desalting chamber to the concentration chamber. For this reason, the concentration chamber side surface of the cation exchange membrane is in a state in which there are many hydrogen ions (H ⁺ ) (= a state in which pH is low).
On the other hand, carbonic acid and silica contained in the concentrated water are captured as anions by the anion exchanger in the concentration chamber, and are transmitted through the anion exchanger to the cation exchange membrane on the concentration chamber side (cations that partition the desalination chamber and the concentration chamber). Exchange membrane) Move to the surface. As described above, the pH of the cation exchange membrane surface on the concentration chamber side is low. For this reason, carbonic acid and silica that are not ionized under low pH conditions lose their charge after being released from the anion exchanger, and permeate through the cation exchange membrane from the concentration chamber and diffuse into the water to be treated in the desalting chamber. Therefore, the purity of treated water will fall.

  Patent Document 2 describes a technique capable of suppressing anion components such as silica contained in concentrated water from passing through a cation exchange membrane and diffusing into treated water. In the technique described in Patent Document 2, a part of the treated water having a silica concentration lower than that of the treated water is passed through the concentration chamber. Thereby, the diffusion of silica from the concentration chamber to the desalting chamber is suppressed.

International Publication No. 2011/152226 JP 2004-33977 A

  When an anion exchanger is filled in the concentration chamber as described in Patent Document 1, a weak acid anion component such as carbonic acid or silica contained in the concentrated water passes through the cation exchange membrane even if the generation of scale can be suppressed. It will diffuse into the water. Moreover, in order to suppress this spreading | diffusion, when a part of treated water is passed through the concentration chamber as described in Patent Document 2, the amount of treated water is reduced.

  The objective of this invention is providing the water treatment apparatus and the water treatment method which can suppress the fall of the quality of treated water, suppressing the reduction | decrease of the amount of treated water, and the production | generation of a scale.

The water treatment apparatus according to the present invention is a water treatment apparatus having a plurality of electric deionized water production apparatuses, wherein each of the plurality of electric deionized water production apparatuses is disposed between the anode and the cathode, on the anode side. A demineralization chamber which is partitioned by a first anion exchange membrane located and a cation exchange membrane located on the cathode side and is filled with an ion exchanger; and the cathode side adjacent to the desalination chamber via the cation exchange membrane A first concentration chamber partitioned by a second anion exchange membrane; and a second concentration chamber adjacent to the desalination chamber via the first anion exchange membrane, wherein the plurality of desalination chambers are in series. A plurality of desalting chambers communicating in series with each other, the treated water flows through the treated water, and the treated water flows out first. The first concentration chamber adjacent to the chamber is filled with an anion exchanger and the treated water flows out. In the first concentration chamber adjacent to the final stage of the desalting chamber via the cation exchange membrane, the cathode side of the cation exchange membrane is filled with the cation exchanger alone, and the anion exchanger is filled in the other region. Filled alone.
The water treatment method according to the present invention is a desalting method in which an ion exchanger is packed between an anode and a cathode, which is partitioned by a first anion exchange membrane located on the anode side and a cation exchange membrane located on the cathode side. A first concentrating chamber adjacent to the desalting chamber via the cation exchange membrane and having the cathode side partitioned by a second anion exchange membrane, and adjacent to the desalting chamber via the first anion exchange membrane A plurality of electric deionized water production devices having a second concentrating chamber, wherein each of the demineralization chambers of the plurality of electric deionized water production devices communicates in series, The plurality of desalting chambers communicating with each other pass the treated water and flow out the treated water, and the first concentration chamber adjacent to the first-stage desalting chamber through which the treated water is first passed. The anion exchanger is packed in the final stage of the desalting chamber and the cap In the first concentrating chamber adjacent via the on-exchange membrane, a water treatment device in which the cation exchanger is filled alone on the cathode side of the cation exchange membrane and the anion exchanger is filled alone in other regions A water treatment method using the water, wherein the water to be treated is passed through the plurality of desalting chambers communicating in series while applying a DC voltage between the anode and the cathode. Treat and discharge the treated water.

  According to the present invention, each of the demineralization chambers of the plurality of electric deionized water production apparatuses is connected in series, and the first concentration adjacent to the first-stage demineralization chamber through which the water to be treated is first fed. The chamber is filled with an anion exchanger, and in the first concentration chamber adjacent to the final desalting chamber through which the treated water flows out via the cation exchange membrane, the cation exchanger is filled on the cathode side of the cation exchange membrane. Yes. For this reason, it becomes possible to suppress the fall of the quality of treated water, suppressing the reduction | decrease of the amount of treated water, and the production | generation of a scale so that it may become clear also from the Example etc. which are mentioned later.

It is the figure which showed the water treatment apparatus 101 of the 1st Embodiment of this invention. It is the figure which showed the water treatment apparatus 201 of the 2nd Embodiment of this invention. It is the figure which showed the measurement result of the quality of the treated water in Examples 1-5 and Comparative Examples 1-2. It is the figure which showed the measurement result of the quality of the treated water in Example 6.

<First Embodiment>
FIG. 1 is a diagram showing a water treatment apparatus 101 according to the first embodiment of the present invention.
The water treatment apparatus 101 includes an EDI apparatus (electric deionized water production apparatus) 101a and an EDI apparatus 101b.

In the EDI apparatus 101a, a concentrating chamber 22a, a desalting chamber 23a, and a concentrating chamber 24a are provided in this order from the anode chamber 21a side between an anode chamber 21a including the anode 11a and a cathode chamber 25a including the cathode 12a. ing. The concentration chamber 24a is an example of a first concentration chamber, and the concentration chamber 22a is an example of a second concentration chamber.
The anode chamber 21a and the concentration chamber 22a are adjacent to each other with a cation exchange membrane 31a therebetween, the concentration chamber 22a and the desalting chamber 23a are adjacent to each other with an anion exchange membrane 32a therebetween, and the desalting chamber 23a and the concentration chamber 24a are cation exchange membranes. The concentration chamber 24a and the cathode chamber 25a are adjacent to each other across the anion exchange membrane 34a. The desalting chamber 23a is partitioned by an anion exchange membrane 32a and a cation exchange membrane 33a. The anion exchange membrane 32a is an example of a first anion exchange membrane, and the anion exchange membrane 34a is an example of a second anion exchange membrane.
The desalting chamber 23a is filled with an ion exchanger. In this embodiment, the anion exchanger AER and the cation exchanger CER are filled in the desalting chamber 23a in a mixed bed form. As the anion exchanger AER, for example, an anion exchange resin is used, and as the cation exchanger CER, for example, a cation exchange resin is used.
The concentration chambers 22a and 24a are filled with an anion exchanger AER in a single bed form.
The water to be treated is passed through the desalting chamber 23a. The supply water is passed through the concentration chambers 22a and 24a, the anode chamber 21a, and the cathode chamber 25a. The direction of water supply can be changed as appropriate.

In the EDI apparatus 101b, a concentrating chamber 22b, a desalting chamber 23b, and a concentrating chamber 24b are provided in this order from the anode chamber 21b side between an anode chamber 21b including the anode 11b and a cathode chamber 25b including the cathode 12b. ing. The concentration chamber 24b is an example of a first concentration chamber, and the concentration chamber 22b is an example of a second concentration chamber.
The anode chamber 21b and the concentration chamber 22b are adjacent to each other with a cation exchange membrane 31b therebetween, the concentration chamber 22b and the desalting chamber 23b are adjacent to each other with an anion exchange membrane 32b, and the desalting chamber 23b and the concentration chamber 24b are cation exchange membranes. The concentrating chamber 24b and the cathode chamber 25b are adjacent to each other across the anion exchange membrane 34b. The desalting chamber 23b is partitioned by an anion exchange membrane 32b and a cation exchange membrane 33b. The anion exchange membrane 32b is an example of a first anion exchange membrane, and the anion exchange membrane 34b is an example of a second anion exchange membrane.
The desalting chamber 23b is filled with an ion exchanger. In this embodiment, the anion exchanger AER and the cation exchanger CER are filled in the desalting chamber 23b in a mixed bed form. In addition, as a filling form of the ion exchanger to the desalting chamber 23b, the mixed bed form (MB) of the anion exchanger AER and the cation exchanger CER, the single bed form of the anion exchanger AER (A), the cation exchanger CER A multiple floor form combining a single floor form (K) may be employed. The desalting chamber 23b communicates with the desalting chamber 23a of the EDI apparatus 101a in series.
The concentration chambers 22b and 24b are filled with a cation exchanger CER in a single bed form.
The treated water treated in the desalting chamber 23a is passed through the desalting chamber 23b. Supply water is passed through the concentration chambers 22b and 24b, the anode chamber 21b, and the cathode chamber 25b, respectively. The direction of water supply can be changed as appropriate.

Next, water treatment performed in the water treatment apparatus 101 will be described.
In the EDI devices 101a and 101b, water is supplied to the anode chambers 21a and 21b, the concentration chambers 22a, 24a, 22b and 24b, and the cathode chambers 25a and 25b, and between the anode 11a and the cathode 12a and between the anode 11b and the cathode 12b. In a state where a DC voltage is applied between the two, the water to be treated is passed through the desalting chamber 23a of the EDI apparatus 101a.

In the EDI apparatus 101a, it is estimated that the following processing is performed on the water to be treated.
The ion component in the for-treatment water is adsorbed by the ion exchanger in the demineralization chamber 23a and subjected to deionization (demineralization) treatment. The treated water that has been deionized (desalted) in the desalting chamber 23a is passed through the desalting chamber 23b.
At this time, in the desalting chamber 23a, the dissociation reaction of water mentioned above occurs by the applied voltage between the anode 11a and the cathode 12a, and hydrogen ions and hydroxide ions are generated. By this hydrogen ion and hydroxide ion, the ion component adsorbed on the ion exchanger in the desalting chamber 23a is ion-exchanged and released from the ion exchanger. Among the released ion components, the anion moves to the concentration chamber 22a through the anion exchange membrane 32a and is discharged as concentrated water from the concentration chamber 22a, and the cation moves to the concentration chamber 24a through the cation exchange membrane 33a and concentrates. It is discharged as concentrated water from the chamber 24a. Electrode water is discharged from the anode chamber 21a and the cathode chamber 25a.
At this time, hardness component ions (magnesium ions Mg ²⁺ and calcium ions Ca ²⁺ ) in the water to be treated permeate the cation exchange membrane 33a and move to the concentration chamber 24a, and the concentration chamber 24a has an anion exchanger AER. Therefore, generation of scale due to hardness component ions is suppressed in the anion exchange membrane 34a. Moreover, since the concentration chamber 22a is also filled with the anion exchanger AER, generation of scale due to hardness component ions is suppressed.
However, since the concentration chamber 24a is filled with the anion exchanger AER, the weak acid anion component of carbonic acid or silica contained in the concentrated water passes through the cation exchange membrane 33a from the concentration chamber 24a and enters the desalting chamber 23a. To spread. For this reason, the to-be-processed water which flows into the desalting chamber 23b from the desalting chamber 23a will contain the weak acid anion component of the carbonic acid and silica which were contained in the concentrated water.

In the EDI apparatus 101b, it is estimated that the following processing is performed.
Ionic components (including weak acid anion components of carbonic acid and silica transferred from the concentrated water) flowing into the EDI apparatus 101b are adsorbed to the ion exchanger in the desalting chamber 23b and subjected to deionization processing. The treated water that has been deionized in the desalting chamber 23b is discharged as treated water. In the EDI apparatus 101b, as in the EDI apparatus 101a, ion exchange is performed in the ion exchanger of the desalting chamber 23b, and the ionic components in the water to be treated supplied to the desalting chamber 23b move to the concentration chambers 22b and 24b. At the same time, the ion exchanger in the desalting chamber 23b is also regenerated.
Since the treated water flowing into the EDI apparatus 101b has already been treated by the EDI apparatus 101a, the concentration of hardness component ions in the treated water is lower than the concentration before flowing into the EDI apparatus 101a. For this reason, generation | occurrence | production of the scale in the concentration chamber 24b is suppressed.
In addition, since the concentration chamber 24b is filled with the cation exchanger CER, diffusion dilution of hydrogen ions existing on the surface of the cation exchange membrane 33b on the concentration chamber 24b side into the concentrated water causes cation exchange in the concentration chamber 24b. Promoted by the body CER, the hydrogen ion concentration on the surface of the cation exchange membrane 33b on the concentration chamber 24b side is rapidly reduced (the pH is no longer low). Also, weak acid anion components such as carbonic acid and silica contained in the concentrated water are difficult to reach the surface of the cation exchange membrane 33b on the side of the concentration chamber 24b due to the presence of the cation exchanger CER in the concentration chamber 24b. Further, even if weak acid anion components such as carbonic acid and silica reach the surface of the cation exchange membrane 33b on the concentration chamber 24b side, the pH of the surface is not low, so that it is maintained as an anion component and passes through the cation exchange membrane 33b. It becomes difficult to do. Therefore, it is possible to suppress the weak acid anion components such as carbonic acid and silica contained in the concentrated water from diffusing into the desalting chamber 23b. Further, in order to suppress the diffusion of the weak acid anion component into the desalting chamber 23b, it is not necessary to use a part of the treated water as the supply water for supplying the concentration chamber. Therefore, it is possible to suppress a decrease in the quality of the treated water while suppressing a decrease in the amount of treated water and generation of scale.

<Second Embodiment>
FIG. 2 is a view showing a water treatment apparatus 201 according to the second embodiment of the present invention.
The water treatment apparatus 201 includes an EDI apparatus 101c and an EDI apparatus 101d.

In the EDI apparatus 101c, a concentrating chamber 22c, a desalting chamber 23c, and a concentrating chamber 24c are provided in this order from the anode chamber 21c side between an anode chamber 21c including the anode 11c and a cathode chamber 25c including the cathode 12c. ing. The concentration chamber 24c is an example of a first concentration chamber, and the concentration chamber 22c is an example of a second concentration chamber.
The anode chamber 21c and the concentration chamber 22c are adjacent to each other with a cation exchange membrane 31c therebetween, the concentration chamber 22c and the desalting chamber 23c are adjacent to each other with an anion exchange membrane 32c therebetween, and the desalting chamber 23c and the concentration chamber 24c are cation exchange membranes. The concentration chamber 24c and the cathode chamber 25c are adjacent to each other across the anion exchange membrane 34c. The desalting chamber 23c is partitioned by an anion exchange membrane 32c and a cation exchange membrane 33c. The anion exchange membrane 32c is an example of a first anion exchange membrane, and the anion exchange membrane 34c is an example of a second anion exchange membrane.
In the desalting chamber 23c, an intermediate ion exchange membrane 36c is provided between the anion exchange membrane 32c and the cation exchange membrane 33c. The desalting chamber 23c is divided into a small desalting chamber 23c-1 and a small desalting chamber 23c-2 by an intermediate ion exchange membrane 36c. Any of an anion exchange membrane, a cation exchange membrane, and a bipolar membrane can be used as the intermediate ion exchange membrane 36c. In the present embodiment, an anion exchange membrane is used as the intermediate ion exchange membrane 36c. The cathode side small desalting chamber 23c-1 is an example of a first small desalting chamber, and the anode side small desalting chamber 23c-2 is an example of a second small desalting chamber.
The small desalting chamber 23c-1 is filled with a cation exchanger CER in a single bed form, and the small desalting chamber 23c-2 is filled with an anion exchanger AER in a single bed form. The treated water is passed through the small desalting chamber 23c-1, and the water flowing out from the small desalting chamber 23c-1 flows into the small desalting chamber 23c-2 (see arrows 104a, 104b, and 104c). ), The small desalting chamber 23c-1 and the small desalting chamber 23c-2 are connected in series.
Supply water is passed through the concentration chambers 22c and 24c, the anode chamber 21c, and the cathode chamber 25c, respectively. In addition, the direction of water supply can be changed as appropriate.

In the EDI apparatus 101d, a concentrating chamber 22d, a desalting chamber 23d, and a concentrating chamber 24d are provided in this order from the anode chamber 21d side between the anode chamber 21d including the anode 11d and the cathode chamber 25d including the cathode 12d. ing. The concentration chamber 24d is an example of a first concentration chamber, and the concentration chamber 22d is an example of a second concentration chamber.
The anode chamber 21d and the concentration chamber 22d are adjacent to each other with a cation exchange membrane 31d therebetween, the concentration chamber 22d and the desalting chamber 23d are adjacent to each other with an anion exchange membrane 32d therebetween, and the desalting chamber 23d and the concentration chamber 24d are cation exchange membranes. The concentrating chamber 24d and the cathode chamber 25d are adjacent to each other across the anion exchange membrane 34d. The desalting chamber 23d is partitioned by an anion exchange membrane 32d and a cation exchange membrane 33d. The anion exchange membrane 32d is an example of a first anion exchange membrane, and the anion exchange membrane 34d is an example of a second anion exchange membrane.
In the desalting chamber 23d, an intermediate ion exchange membrane 36d is provided between the anion exchange membrane 32d and the cation exchange membrane 33d. The desalting chamber 23d is divided into a small desalting chamber 23d-1 and a small desalting chamber 23d-2 by an intermediate ion exchange membrane 36d. An anion exchange membrane is used as the intermediate ion exchange membrane 36d. The small desalination chamber 23d-1 on the anode side is an example of a second small desalination chamber, and the small desalination chamber 23d-2 on the cathode side is an example of a first small desalination chamber.
The small desalting chamber 23d-1 is filled with the anion exchanger AER in a single bed form, and the small desalting chamber 23d-2 is filled with the cation exchanger CER alone in the region of the inlet side 23d-21 and the outlet side 23d. The region of −22 is filled with the anion exchanger AER alone. The treated water is passed through the small desalting chamber 23d-1, and the water flowing out from the small desalting chamber 23d-1 flows into the small desalting chamber 23d-2 from the inlet side 23d-21 (arrow 104c, The small desalting chamber 23d-1 and the small desalting chamber 23d-2 are connected in series.
Supply water is passed through the concentration chambers 22d and 24d, the anode chamber 21d, and the cathode chamber 25d, respectively. In addition, the direction of water supply can be changed as appropriate.

Next, water treatment performed in the water treatment apparatus 201 will be described.
In the EDI devices 101c and 101d, supply water is passed through the anode chambers 21c and 21d, the concentration chambers 22c, 24c, 22d and 24d, and the cathode chambers 25c and 25d, and between the anode 11c and the cathode 12c and the anode 11d. In a state where a DC voltage is applied to the cathode 12d, water to be treated is passed through the small desalting chamber 23c-1 of the EDI apparatus 101c.

In the EDI apparatus 101c, it is estimated that the following processing is performed on the water to be treated.
The cations in the water to be treated are adsorbed by the cation exchanger CER in the desalting chamber 23c-1, and a deionization process is performed. The treated water that has been deionized in the desalting chamber 23c-1 is passed through the desalting chamber 23c-2.
At this time, in the desalting chamber 23c, a dissociation reaction of water occurs by an applied voltage between the anode 11c and the cathode 12c, and hydrogen ions and hydroxide ions are generated. By this hydrogen ion, the cation adsorbed on the cation exchanger CER in the desalting chamber 23c-1 is ion-exchanged and released from the cation exchanger CER. The liberated cations move to the concentration chamber 24c through the cation exchange membrane 33c and are discharged from the concentration chamber 24c as concentrated water.
At this time, hardness component ions (magnesium ions Mg ²⁺ and calcium ions Ca ²⁺ ) in the water to be treated permeate the cation exchange membrane 33c and move to the concentration chamber 24c, and the concentration chamber 24c has an anion exchanger AER. Therefore, generation of scale due to hardness component ions in the anion exchange membrane 34c is suppressed.
However, weak acid anion components such as carbonic acid and silica contained in the concentrated water diffuse from the concentration chamber 24c through the cation exchange membrane 33c and diffuse into the desalting chamber 23c-1. For this reason, the to-be-processed water which flows into the desalting chamber 23c-2 from the desalting chamber 23c-1 will contain the carbonic acid and the silica which were contained in the concentrated water.

In the desalting chamber 23c-2, the anion in the water to be treated is adsorbed to the anion exchanger AER in the desalting chamber 23c-2, and a deionization process is performed. The treated water that has been deionized in the desalting chamber 23c-2 is passed through the desalting chamber 23d-1.
At this time, the anion adsorbed on the anion exchanger AER in the desalting chamber 23c-2 is ion-exchanged by the hydroxide ions generated by the water dissociation reaction and is released from the anion exchanger AER. The liberated anion moves to the concentration chamber 22c through the anion exchange membrane 32c, and is discharged from the concentration chamber 22c as concentrated water. Further, the weak acid anion component of carbonic acid or silica that has moved from the concentrated water in the concentrating chamber 24c to the water to be treated in the small desalting chamber 23c-1 also moves to the concentrating chamber 22c through the anion exchange membrane 32c, and is concentrated. It is discharged as concentrated water from the chamber 22c.

In the desalting chamber 23d-1, the anion in the water to be treated is adsorbed to the anion exchanger AER in the desalting chamber 23d-1, and a deionization process is performed. The treated water that has been deionized in the desalting chamber 23d-1 is passed through the desalting chamber 23d-2 from the inlet side 23d-21.
At this time, in the desalting chamber 23d-1, the anion adsorbed on the anion exchanger AER in the desalting chamber 23d-1 is ion-exchanged by hydroxide ions generated by the water dissociation reaction, and the anion Released from the exchanger AER. The liberated anion moves to the concentration chamber 22d through the anion exchange membrane 32d and is discharged from the concentration chamber 22d as concentrated water.

In the desalting chamber 23d-2, cations in the water to be treated are adsorbed by the cation exchanger CER in the region on the inlet side 23d-21, and deionization processing is performed. Thereafter, the water to be treated is passed through the region on the outlet side 23d-22 of the desalting chamber 23d-2.
At this time, in the cation exchanger CER in the region on the inlet side 23d-21, the cations adsorbed on the cation exchanger CER in the region on the inlet side 23d-21 are ion-exchanged by hydrogen ions generated by the water dissociation reaction. And released from the cation exchanger CER. The liberated cations move to the concentration chamber 24d through the cation exchange membrane 33d and are discharged as concentrated water from the concentration chamber 24d.
Since the water to be treated flowing into the cation exchanger CER in the region on the inlet side 23d-21 has already been treated by the EDI device 101c, the concentration of hardness component ions in the water to be treated flows into the EDI device 101c. It is lower than the previous concentration. For this reason, generation | occurrence | production of the scale in the concentration chamber 24d is suppressed.
Further, since the concentration chamber 24d is filled with the cation exchanger CER, diffusion of weak acid anion components such as carbonic acid and silica contained in the concentrated water to the desalting chamber 23d-2 can be suppressed. Further, in order to suppress the diffusion of the weak acid anion component to the desalting chamber 23d-2, it is not necessary to use a part of the treated water as the supply water for supplying the concentration chamber. Therefore, it is possible to suppress a decrease in the quality of the treated water while suppressing a decrease in the amount of treated water and generation of scale.
And the anion in to-be-processed water passed through the area | region of the exit side 23d-22 of the desalination chamber 23d-2 is adsorbed by the anion exchanger AER of the area | region of the exit side 23d-22, and a deionization process is performed. . Thereafter, the water that has passed through the anion exchanger AER in the region of the outlet side 23d-22 is discharged as treated water.
At this time, in the anion exchanger AER in the region of the outlet side 23d-22, the adsorbed anion is ion-exchanged by the hydroxide ion generated by the water dissociation reaction and is released from the anion exchanger AER. The liberated anion moves to the desalting chamber 23d-1 through the intermediate ion membrane 36d, then moves to the concentration chamber 22d, and is discharged from the concentration chamber 22d as concentrated water.

  In each embodiment described above, the illustrated configuration is merely an example, and the present invention is not limited to the configuration.

  For example, in the concentration chamber 24b and the concentration chamber 24d, the cation exchanger CER may be filled alone on the cathode side of the cation exchange membrane 33b or the cation exchange membrane 33d, and the anion exchanger AER may be filled in other regions.

  In each embodiment mentioned above, the water treatment apparatus using two EDI apparatuses was shown. However, the first and second concentrating chambers adjacent to the first-stage desalting chamber through which the water to be treated is first passed are filled with anion exchangers, and the final-stage desalting chamber and the cation are discharged from the treated water. In the first concentrating chambers adjacent via the exchange membrane, the number of EDI devices is not limited to two but may be three or more as long as the cation exchanger is filled on the cathode side of the cation exchange membrane. Moreover, it is good also as a structure which arrange | positions each demineralization chamber in series inside a single EDI apparatus (one housing | casing), and arrange | positions each demineralization chamber block in two or more steps.

In the above, the basic configuration (cell set) consisting of [concentration chamber (C) | anion exchange membrane (AEM) | desalination chamber (D) | cation exchange membrane (CEM) | concentration chamber (C)] is an anode and a cathode. Between the two. However, even if a plurality of such cell sets are juxtaposed between the electrodes, and the plurality of cell sets are electrically connected in series with one end as an anode and the other end as a cathode, the processing capacity can be increased. Good.
In this case, adjacent concentrating chambers can be shared between adjacent cell sets. Therefore, as the configuration of the EDI apparatus, the configuration of [anode chamber | C | AEM | D | CEM | C | AEM | D | CEM | C | AEM | D | CEM | ... | C | cathode chamber] is used. Also good. The number of desalting chambers in such a series-structured EDI apparatus is also referred to as “number of desalting chamber cell pairs”.
Further, in such a series structure, for the desalination chamber closest to the anode chamber, the anode chamber itself can function as a concentration chamber without interposing an independent concentration chamber between the anode chamber and the cathode chamber. For the desalting chamber closest to the chamber, the cathode chamber itself can also function as a concentrating chamber without interposing a concentrating chamber between it and the cathode chamber. In order to suppress the power consumed by the application of the DC voltage, the anode chamber and the cathode chamber may be filled with an ion exchanger to lower the electric resistance.

<Examples 1-5>
The water treatment apparatus 101 of 1st Embodiment was used as a water treatment apparatus of Examples 1-4. The difference between each of Examples 1 to 4 is that the direction of water supply to the concentrating chamber (hereinafter referred to as “concentrating chamber water passing direction”) and the direction of water to be treated to the desalting chamber (hereinafter “dewatering”). (Referred to as “salt chamber water flow direction”).
In Example 1, in the first-stage EDI apparatus 101a and the second-stage EDI apparatus 101b, the concentration chamber water flow direction and the desalination chamber water flow direction were in a parallel flow relationship.
In Example 2, in the first-stage EDI apparatus 101a, the flow direction of the concentrating chamber and the flow direction of the desalting chamber are in a co-current relationship, and in the second-stage EDI apparatus 101b, the flow direction of the concentrating chamber and the dewatering direction are removed. The flow direction of the salt room was considered as a countercurrent relationship. In this case, the inlet of the second stage enrichment chamber and the outlet of the second stage desalination chamber are adjacent.
In Example 3, in the first stage EDI apparatus 101a, the flow direction of the concentrating chamber and the direction of flow of the desalting chamber are countercurrently related, and in the second stage EDI apparatus 101b, the flow direction of the concentrating chamber and the direction of dewatering. The flow direction of the salt room was in a parallel flow relationship. In this case, the inlet of the first stage concentration chamber and the outlet of the first stage desalination chamber are adjacent.
In Example 4, in the first-stage EDI apparatus 101a and the second-stage EDI apparatus 101b, the water flow direction in the concentrating chamber and the water flow direction in the desalination chamber were in a countercurrent relationship. In this case, the inlet of the first-stage concentrating chamber and the outlet of the first-stage desalting chamber are adjacent, and the inlet of the second-stage concentrating chamber and the outlet of the second-stage desalting chamber are adjacent.
Moreover, the water treatment apparatus 201 of 2nd Embodiment was used as a water treatment apparatus of Example 5. FIG. In Example 5, the first-stage EDI device 101c has a countercurrent relationship between the flow direction of the concentrating chamber and the flow direction of the desalination chamber, and the second-stage EDI device 101d has a flow direction of the concentrating chamber and the dewatering direction. The water flow direction in the salt chamber 23d-2 was defined as a countercurrent relationship.

<Comparative Examples 1-2>
As a water treatment apparatus of Comparative Example 1, in the water treatment apparatus 101 of the first embodiment, a cation exchanger CER is used instead of the anion exchanger AER in the concentration chambers 22a and 24a of the first stage EDI apparatus 101a. The water treatment apparatus was used in which the concentration chambers 22b and 24b of the second stage EDI apparatus 101b were filled with an anion exchanger AER in a single bed form instead of the cation exchanger CER. In Comparative Example 1, the flow direction of the concentrating chamber and the direction of passing water of the desalting chamber were set to have a countercurrent relationship in the first stage EDI apparatus 101a and the second stage EDI apparatus 101b.
As the water treatment apparatus of Comparative Example 2, in the water treatment apparatus 101 of the first embodiment, an anion exchanger and a cation exchanger CER are used instead of the anion exchanger AER in the concentration chambers 22a and 24a of the first stage EDI apparatus 101a. Is used in a mixed bed form, and a water treatment apparatus is used in which the concentration chambers 22b and 24b of the second stage EDI apparatus 101b are filled with an anion exchanger AER and a cation exchanger CER in a mixed bed form instead of the cation exchanger CER. It was. In Comparative Example 2, the concentrating chamber water passing direction and the desalting chamber water passing direction were counterflowed in the first stage EDI apparatus 101a and the second stage EDI apparatus 101b.

The operating conditions such as the specifications of the EDI apparatus, the water flow rate, the applied current, the quality of the water to be treated in Examples 1 to 5 and Comparative Examples 1 and 2 are as follows.
An anion exchange resin [trade name: Amberjet 4002 (strongly basic anion exchange resin 4002), manufactured by Dow Chemical Co., Ltd.] was used as the anion exchanger, and a cation exchange resin [trade name: Amberjet] 1020 (strongly acidic cation exchange resin 1020), manufactured by Dow Chemical Company].
In the desalting chamber 23d-2 filled with both the anion exchange resin and the cation exchange resin, the volume ratio of the anion exchange resin and the cation exchange resin was set to 1: 1.
-RO (reverse osmosis membrane) treated water (conductivity: 3-4 μS / cm, carbonic acid concentration: 5-6 mg CO ₂ / L, hardness concentration: 500-600 μg CaCO as treated water to be passed through the first stage EDI apparatus ₃ / L) was used.
The volume of the cell (desalting chamber, concentration chamber, anode chamber, cathode chamber) was 100 mm × 100 mm × 10 mm.
-The number of cell pairs in the desalination chamber was 5 cell pairs.
-The flow rate of water to be treated was 100 L / h.
The value of the current flowing between the anode and the cathode was 0.4A.
・ Pure water from another system was used as the supply water to be supplied to the concentrating chamber.
-The flow rate of water supplied to the concentrating chamber was 25 L / h.
-Pure water from another system was used as the supply water supplied to the anode chamber and the supply water supplied to the cathode chamber.
The flow rate of water supplied to the anode chamber and the flow rate of water supplied to the cathode chamber were set to 5 L / h.
-The direction of water supply to the anode and cathode chambers is all directed from the bottom to the top of the device in order to discharge the gas generated by the electrode reaction in the electrode chamber (from bottom to top in Figs. 1 and 2). Direction).

  FIG. 3 is a diagram showing a scale generation state in the first-stage EDI apparatus in Examples 1 to 5 and Comparative Examples 1 and 2 and a measurement result of the quality of the treated water discharged from the second-stage EDI apparatus. It is. In FIG. 3, the mixed bed form of anion exchanger AER and cation exchanger CER is (MB), the single bed form of anion exchanger AER is (A), and the single bed form of cation exchanger CER is (K). Show.

  As can be seen from the comparison between Example 1 and Example 2, the flow direction of the concentrating chamber of the second-stage EDI device is made to have a countercurrent relationship with the water flow direction of the desalination chamber of the second-stage EDI device. The quality of treated water has been improved. This is presumed that the back diffusion amount of the weak acid anion component from the concentrating chamber to the desalting chamber decreases in the case of counterflow.

  As can be seen from the comparison between Example 1 and Example 3, the flow direction of the concentrating chamber of the first-stage EDI device is made to have a countercurrent relationship with the direction of water flow of the desalination chamber of the first-stage EDI device. The generation of scale in the first stage EDI apparatus was suppressed.

  As can be seen from the comparison between Example 4 and Comparative Example 1, in both the first stage and the second stage EDI devices, the concentration chamber water flow direction is in a relationship between the desalination chamber water flow direction and the countercurrent flow. When the first-stage concentration chamber was filled with the cation exchanger CER as in Comparative Example 1, the generation of scale in the concentration chamber was not suppressed. Moreover, when the anion exchanger is filled in the concentration chamber of the second-stage EDI apparatus as in Comparative Example 1, the anion component adsorbed on the anion exchanger AER in the concentration chamber diffuses to the desalting chamber side, and the treated water The water quality declined.

  Moreover, the following points are understood from the comparison between Comparative Example 1 and Comparative Example 2. In Comparative Example 2, since the anion exchanger AER and the cation exchanger CER are filled in the concentration chamber of the first-stage EDI apparatus in a mixed bed form, the continuity of the cation exchanger CER in the concentration chamber is higher than in Comparative Example 1. Becomes worse. For this reason, the hardness component which moves to an anion exchange membrane decreases, and the generation | occurrence | production condition of a scale improves, but generation | occurrence | production of a scale is still many. For the same reason, when the anion exchanger AER and the cation exchanger CER are filled in the mixed chamber in the concentration chamber of the second-stage EDI apparatus, compared to Comparative Example 1, the concentration chamber is further desalted. Since the anion component diffusing in the water decreases, the water quality is improved, but high water quality cannot be obtained.

  As can be seen from the comparison between Example 4 and Example 5, it was possible to obtain higher scale resistance and quality of the treated water by using an EDI apparatus having a two-salt desalination chamber.

<Example 6>
Example 6 is an example in which the carbonic acid concentration was changed in the range of 1 to 25 mg CO ₂ / L in the state where the hardness concentration of the water to be treated was fixed at 2000 μg CaCO ₃ / L in Example 5.
FIG. 4 shows the carbon dioxide concentration of the water to be treated at the inlet of the desalination chamber 23d-1 of the second stage EDI apparatus in Example 6, the state of occurrence of scale in the first stage EDI apparatus, and the second stage. It is the figure which showed the measurement result of the quality of the treated water which flows out of the EDI apparatus of eyes. In FIG. 4, the single bed form of the anion exchanger AER is shown by (A), and the single bed form of the cation exchanger CER is shown by (K).
As can be seen from Example 6, in the situation where the carbon dioxide concentration of the water to be treated in the first stage EDI apparatus is 3 to ₂₀ mg CO ₂ / L, high treated water quality can be obtained, and further, the second stage EDI apparatus If the carbon dioxide concentration of the water to be treated at the inlet of the desalting chamber 23d-1 was 1 mg CO ₂ / L or less, the quality of the treated water was maintained. In addition, under a high concentration condition of a hardness concentration of 2000 μg CaCO ₃ / L, a very large scale was generated unless the carbonate concentration of the water to be treated to the first stage EDI apparatus was 3 mg CO ₂ / L or more. Incidentally, carbonate concentration of the water to be treated to the EDI apparatus of the first stage is because when the 1mgCO ₂ / L could not be stable operation, in FIG. 4, data relating to processing water is not.

11a, 11b, 11c, 11d Anode 12a, 12b, 12c, 12d Cathode 21a, 21b, 21c, 21d Anode chamber 22a, 24a, 22b, 24b, 22c, 24c, 22d, 24d Concentration chamber 23a, 23b, 23c, 23d Salt chamber 23c-1, 23d-1 First desalting chamber 23c-2, 23d-2 Second desalting chamber 25a, 25b, 25c, 25d Cathode chamber 31a, 33a, 31b, 33b, 31c, 33c, 31d, 33d Cation Exchange Membrane 32a, 34a, 32b, 34b, 32c, 34c, 32d, 34d Anion Exchange Membrane 36a, 36b Intermediate Ion Exchange Membrane CER Cation Exchanger AER Anion Exchanger 101, 201 Water Treatment Equipment 101a, 101b, 101c, 101d EDI apparatus

Claims (11)

In a water treatment apparatus having a plurality of electric deionized water production apparatuses,
Each of the plurality of electric deionized water production apparatuses is partitioned between an anode and a cathode by a first anion exchange membrane located on the anode side and a cation exchange membrane located on the cathode side. A first concentration chamber adjacent to the desalting chamber through the cation exchange membrane and having the cathode side partitioned by a second anion exchange membrane, and through the first anion exchange membrane A second concentrating chamber adjacent to the desalting chamber,
The plurality of desalting chambers communicate with each other in series.
The plurality of desalting chambers communicating in series with each other, the treated water is passed and the treated water flows out,
The first concentration chamber adjacent to the first-stage desalting chamber through which the water to be treated is first passed is filled with an anion exchanger,
In the first concentration chamber adjacent via the cation exchange membrane and the demineralization chamber in the final stage for flowing out the treated water, a cation exchanger is filled alone on the cathode side of the cation exchange membrane, A water treatment apparatus, wherein the region is filled with an anion exchanger.   The water treatment apparatus according to claim 1, wherein an inlet of the first concentration chamber adjacent to the first-stage desalting chamber and an outlet of the first-stage desalting chamber are adjacent to each other.   The water treatment apparatus according to claim 1 or 2, wherein an inlet of the first concentration chamber adjacent to the final-stage desalting chamber and an outlet of the final-stage desalting chamber are adjacent to each other. At least one desalting chamber of the plurality of desalting chambers is
An intermediate ion exchange membrane located between the anion exchange membrane and the cation exchange membrane;
A first small desalting chamber partitioned by the cation exchange membrane and the intermediate ion exchange membrane;
A second small desalting chamber partitioned by the anion exchange membrane and the intermediate ion exchange membrane,
The water treatment device according to claim 1, wherein the first small desalting chamber and the second small desalting chamber communicate with each other in series.   5. The water treatment according to claim 4, wherein an outlet of a small desalting chamber partitioned by an intermediate ion exchange membrane and a cation exchange membrane of the first stage desalting chamber is adjacent to an inlet of the first concentration chamber. apparatus.   The water according to claim 4 or 5, wherein an outlet of a small desalting chamber partitioned by an intermediate ion exchange membrane and a cation exchange membrane of the final-stage desalting chamber and an inlet of the first concentration chamber are adjacent to each other. Processing equipment. A demineralization chamber partitioned between a first anion exchange membrane located on the anode side and a cation exchange membrane located on the cathode side and filled with an ion exchanger between the anode and the cathode, and the cation exchange membrane A first concentrating chamber adjacent to the desalting chamber via the cathode side and partitioned by a second anion exchange membrane, and a second concentrating chamber adjacent to the desalting chamber via the first anion exchange membrane. Each of the plurality of electric deionized water production apparatuses, the demineralization chambers of each of the plurality of electric deionized water production apparatuses are connected in series, and the plurality of demineralization chambers connected in series are The first concentration chamber adjacent to the first-stage desalting chamber through which the treated water flows and the treated water flows out, and the treated water is first passed is filled with an anion exchanger, Adjacent to the final stage of the desalting chamber through which the treated water flows out through the cation exchange membrane The first concentrating chamber is a water treatment method using a water treatment apparatus in which the cation exchanger is filled with the cation exchanger alone on the cathode side of the cation exchange membrane and the anion exchanger is filled alone in other regions. And
Passing the treated water through the plurality of desalting chambers communicating in series while applying a DC voltage between the anode and the cathode, treating the treated water and discharging the treated water A water treatment method characterized by. The water treatment method according to claim 7, wherein the carbon dioxide concentration of the water to be treated supplied to the first-stage desalting chamber is 3 to 20 mg CO ₂ / L. The water treatment method according to claim 7 or 8, wherein the carbon dioxide concentration of the water to be treated supplied to the final-stage desalting chamber is less than 1 mg CO ₂ / L. The water treatment method according to any one of claims 7 to 9, wherein a hardness concentration of the water to be treated supplied to the first-stage desalting chamber is 2000 µg CaCO ₃ / L or less. The water treatment method according to any one of claims 7 to 10, wherein the hardness concentration of the water to be treated supplied to the final-stage desalting chamber is 20 µg CaCO ₃ / L or less.

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