JP2018122274A - Water treatment system, operation method thereof and protection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely protect an EDI apparatus against an oxidizing agent such as chlorine which may deteriorate an ion exchange membrane or an ion exchanger in an electric deionized water production apparatus (EDI apparatus). SOLUTION: Water to be treated is passed through a filler for removing an oxidant in water to be treated, and the water to be treated after passing through the filler is supplied to an EDI device. As the filler, for example, a material containing a weakly basic anion exchange resin is used, and the space velocity of the water to be treated in the filler is set to, for example, 500 h-1 or more. [Selection diagram] Fig. 1

Description

  The present invention relates to a water treatment system including an electric deionized water production apparatus (EDI (Electro Deionization) apparatus), an operating method thereof, and a protection device used in the water treatment system.

As an apparatus that can generate deionized water without separately regenerating the ion exchange resin, an electric deionized water production apparatus is known. In an electrical deionized water production system, an ion exchanger (anion exchange) made of an ion exchange resin between a cation exchange membrane that allows only cations (cations) to pass through and an anion exchange membrane that allows only anions (anions) to pass through. Body and / or cation exchanger) to form a desalination chamber, and a concentration chamber is arranged outside the cation exchange membrane and anion exchange membrane, and consists of a desalination chamber and concentration chambers on both sides thereof. As a configuration, this is disposed between the anode and the cathode. At this time, as viewed from the desalting chamber, an anion exchange membrane is disposed between the desalting chamber and the anode, and a cation exchange membrane is disposed between the desalting chamber and the cathode. When the treated water is passed through the desalting chamber with a DC voltage applied between the anode and the cathode, the ionic components in the treated water are trapped by the ion exchanger in the desalting chamber and the desalted water is desalted. Processing is performed. At the same time, a water dissociation reaction proceeds at the interface between the ion exchange membrane and the ion exchanger or between the ion exchanger and the ion exchanger, and hydrogen ions (H ⁺ ) and hydroxide ions (OH ⁻ ) are generated. The regeneration treatment of the ion exchanger by the generated hydrogen ions and hydroxide ions proceeds. The ion component previously captured by the ion exchanger is released by the regeneration process, but the released ion component moves to the concentration chamber through the ion exchange membrane, so it is discharged outside the apparatus by passing water through the concentration chamber. can do. An example of an electric deionized water production apparatus is disclosed in Patent Document 1.

  The electric deionized water production apparatus is one of water treatment apparatuses used for producing pure water and is used by being incorporated in a water treatment system to which treated water or raw water is supplied. In water treatment systems, oxidants are often used for sterilization and cleaning in systems that contain them. When using an oxidizer in cleaning applications, the oxidizer is used only during the actual cleaning process, but in sterilization applications, the oxidizer is constantly injected into the system, so it is built into the system. The equipment that is used is always exposed to oxidants. When tap water is used as the water to be treated, chlorine is added to the tap water for sterilization. However, since chlorine is also an oxidizing agent, an oxidizing agent is brought into the apparatus.

  Although main components constituting the electric deionized water production apparatus include an ion exchange membrane and an ion exchanger, the ion exchanger and the ion exchange membrane may be deteriorated by contact with an oxidizing agent. Specifically, an ion exchange membrane or ion exchange resin having a styrene-divinylbenzene crosslinked structure as a base structure is deteriorated because the crosslinked structure is cut by contact with an oxidizing agent. In particular, according to the knowledge of the present inventors, the ion exchange membrane or ion exchanger provided in the electric deionized water production apparatus is an oxidant in a state where a DC voltage is applied between the anode and the cathode described above. When it touches, it shows the tendency which deteriorates more notably. Moreover, in the water treatment system, a reverse osmosis membrane device having a reverse osmosis membrane is provided in the front stage of the electric deionized water production device, and water that has permeated the reverse osmosis membrane is supplied to the electric deionized water production device. However, polyamide-based membranes used as reverse osmosis membranes also tend to deteriorate due to the oxidizing agent.

  Patent Document 2 discloses a device for injecting a reducing agent such as sodium bisulfite into water to be treated in a water treatment system in which an electrical deionized water production device is provided at the latter stage of a reverse osmosis membrane device, and an injecting reducing agent. It is disclosed that an activated carbon filtration device to which the treated water is supplied is provided, and the treated water flowing out from the activated carbon filtration device is supplied to the reverse osmosis membrane device. Although it relates to an ordinary ion exchange device rather than an electric deionized water production device, Patent Document 3 performs filtration with activated carbon to remove free chlorine in the water to be treated, and ionizes the water to be treated after filtration. The supply to the exchange device is disclosed. Patent Document 4 discloses that, as a pretreatment, desalination of seawater by a reverse osmosis membrane device is performed by adding chlorine and then performing a reduction treatment with sodium hydrogen sulfite to prevent residual chlorine.

JP 2011-251266 A JP 2012-206008 A Japanese Patent Laid-Open No. 10-337563 JP-A-7-308671

  As a method for removing the oxidant, addition of a reducing agent to the water to be treated and activated carbon filtration treatment to the water to be treated are known. However, addition failure due to malfunction of a pump used for the addition of the reducing agent or oxidation with activated carbon. It is difficult to predict a decrease in the agent removal ability. As a result, when these methods are employed, an oxidant may flow into the electric deionized water production apparatus, which causes many problems in the electric deionized water production apparatus. If an oxidant flows into an electrical deionized water production system and the ion exchange membrane or ion exchanger deteriorates, there is no other way to deal with them than to replace them, and the cost required to replace the ion exchange membrane or ion exchanger. In addition, problems such as having to stop the operation of the entire water treatment system occur with the replacement. Since the electrical deionized water production apparatus is an expensive device among the devices constituting the water treatment system, the inflow of the oxidizing agent must be particularly prevented.

  As a measure to prevent the deterioration of ion exchange membranes and ion exchangers due to oxidants, it is also possible to measure and manage the oxidant concentration in the treated water on a daily basis, but to constantly monitor the oxidant concentration In order to do so, it is necessary to monitor with online instruments and measure the sampled water every day, and the labor and cost of management cannot be ignored.

  An object of the present invention is to provide a water treatment that can prevent the inflow of an oxidant into an electric deionized water production apparatus over a certain period with a simple configuration, and can reliably protect the electric deionized water production apparatus from the oxidant. It is to provide a system, a method of operating the system, and a protective device used there.

  The water treatment system of the present invention is a water treatment system including a reverse osmosis membrane and an electric deionized water production apparatus, in which water to be treated that has passed through the reverse osmosis membrane is supplied to remove oxidant in the water to be treated. It has a protective device provided with a material, The to-be-processed water which passed the filler is supplied to the said electrical deionized water manufacturing apparatus.

  The operation method of the water treatment system of the present invention includes an electric deionized water production apparatus, and in the operation method of the water treatment system for treating the treated water containing chlorine, the filler for removing the oxidant in the treated water is used. On the other hand, the water to be treated is passed, and the water to be treated after passing through the filler is supplied to the electric deionized water production apparatus.

In this invention, before supplying the to-be-processed water which may contain oxidizing agents, such as chlorine, to an electrical deionized water manufacturing apparatus, to-be-processed water is made to flow into the filler which removes an oxidizing agent. At this time, a space velocity SV (Space Velocity) represented by Q / V when the volume of the filler is V [L] and the flow rate of the water to be treated in the filler is Q [L / h] is 500 h ^−. is preferably ¹ or more, more preferably to 500h ^-1 or more 4000h ^-1 or less, and more preferably to 1000h ^-1 or more 4000h ^-1 or less. A space velocity of 500 h ⁻¹ means that water to be treated is flowed to the filler 500 times the volume of the filler per hour. Conventionally, the space velocity in a filler (for example, ion exchange resin layer) in a general water treatment apparatus (for example, ion exchange apparatus) is about 50 h ⁻¹ at most, but the present inventors usually do not use it. The present inventors have found that an oxidizing agent such as chlorine can be removed from the water to be treated even when the water to be treated is passed through the filler at such a large space velocity. Use at such a large space velocity also has the advantage that the size of the protective device provided with the filler can be reduced.

  In the present invention, it is preferable to use a filler containing at least a weakly basic anion exchange resin. The weakly basic anion exchange resin is a gel type having only a swelling pore (referred to as micropore) generated by a three-dimensional cross-linking structure with styrene-divinylbenzene and generated in the resin layer by water absorption, There is a macroporous type (also called a giant network structure or MR type) that also has physical pores (called macropores) that do not disappear. In the present invention, it is more preferable to use a macroporous type as the weakly basic anion exchange resin.

The protection device of the present invention is a protection device that is detachably provided at the front stage of an electrical deionized water production device, and includes a filler for removing oxidant in the water to be treated, and a cartridge-type container for storing the filler The space velocity when the treated water is passed through the filler is 500 h ⁻¹ or more, and the treated water that has passed through the filler is supplied to the electrical deionized water production apparatus. ing.

  ADVANTAGE OF THE INVENTION According to this invention, the inflow of the oxidizing agent to an electrical deionized water manufacturing apparatus can be reliably prevented over a certain period with a simple configuration.

It is a figure which shows the structure of the water treatment system in one Embodiment of this invention. It is a figure which shows an example of a structure of a protection apparatus. It is a figure which shows the structure of the water treatment system in another embodiment of this invention. It is a figure which shows another example of a structure of a protection apparatus. 3 is a graph showing the results of Example 1. 10 is a graph showing the results of Example 2.

  Next, a preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a water treatment system to which an operation method according to the present invention is applied. The illustrated water treatment system performs demineralization treatment on water to be treated that may contain an oxidant to generate deionized water. A representative example of the oxidizing agent is chlorine, and examples of water to be treated that may contain the oxidizing agent include those derived from tap water to which chlorine has been added for sterilization.

  The water treatment system shown in FIG. 1 includes an electric deionized water production apparatus (EDI) 10, and an oxidant is placed in the electric deionized water production apparatus 10 at the front stage of the electric deionized water production apparatus 10. A protection device 20 having a filler for removing the oxidant in the water to be treated is provided so as not to flow in. The protection device 20 assumes that the oxidant concentration in the water to be treated is reduced due to problems in this treatment, etc., assuming that the treatment water is subjected to a constant treatment for removing the oxidant, such as addition of a reducing agent and activated carbon filtration, in advance. This prevents the oxidant from flowing into the electric deionized water production apparatus 10 when it rises suddenly. In this example, the protective device 20 is provided so that the outlet of the protective device 20 is connected to the inlet of the electrical deionized water production apparatus 10. Furthermore, a pump 15 that supplies the water to be treated to the protection device 20 is provided in the previous stage of the protection device 20 so that the space velocity when the water to be treated is passed through the filler becomes a predetermined value. The treated water that has passed through the filler in the protection device 20 is supplied to the electrical deionized water production device 10.

  FIG. 2A shows the configuration of the protection device 20. The protection device 20 is detachably provided, for example, at the front stage of the electrical deionized water production device 10, and includes a filler 21 that removes an oxidizing agent in the water to be treated, and a container 22 that stores the filler 21. And. Since the protective device 20 has a function of protecting the electrical deionized water production device 10 against a sudden increase in oxidant concentration in the water to be treated, it is used in a maintenance-free state for a certain period of time. However, it is preferable that the battery can be easily replaced after the period. Therefore, it is preferable to use a cartridge type container 22. Any filler can be used as long as it can remove an oxidizing agent such as chlorine in the water to be treated. However, from the viewpoint of downsizing of the protective device 20, it is preferable to use as the filler a material having higher oxidant removal efficiency than activated carbon conventionally used for removing chlorine and the like. As is clear from the examples described later, it is preferable to use a weakly basic anion exchange resin.

The space velocity SV of the water to be treated in the filler can also be set in an arbitrary range as long as a desired oxidant removal efficiency can be obtained, but the space velocity SV is reduced from the viewpoint of downsizing the protective device 20 or the like. It is preferable to make it high, for example, it is preferable to be 500 h ⁻¹ or more. As shown in the Examples, when a weakly basic anion exchange resin is used as the filler 21, there is a noticeable decrease in the oxidizing agent removal efficiency in the space velocity range from 500 h ⁻¹ to 4000 h ^−1. In this respect as well, it is preferable to use a weakly basic anion exchange resin as the filler 21.

  In this embodiment, by providing such a protective device 20, even if a problem occurs in the addition of the reducing agent and the activated carbon filtration and the oxidant is contained in the water to be treated, electric deionization is performed for several weeks. It is possible to prevent the oxidant from flowing into the water production apparatus. This makes it possible to measure the oxidant concentration, which had been required to be performed on a daily basis, once a few weeks, and to greatly reduce the labor and cost required to manage the oxidant concentration. Is possible.

  By the way, when water to be treated containing an oxidizing agent such as chlorine is passed through the filler 21, if the filler 21 is, for example, a weakly basic anion exchange resin, the weakly basic anion exchange resin can be obtained by touching the oxidizing agent. It gradually deteriorates, and the weakly basic anion exchange resin, which should be granular, is transformed into a jelly. As a result, there is a tendency that the difference in pressure between both sides of the filler 21 increases when the water to be treated is passed. Therefore, as shown in FIG. 2B, a pressure gauge 23 for measuring the pressure between the inlet and the outlet of the protective device 20 is further provided to monitor the water flow differential pressure of the protective device 20, and the water flow differential pressure. By managing this, for example, the replacement time of the protection device 20 that is of a cartridge type may be determined.

  In the present embodiment, the position where the protection device 20 is provided in the water treatment system may be any position as long as it is a front stage of the electrical deionized water production apparatus 10. A reverse osmosis device (RO) is often provided upstream of the electric deionized water production device, but as shown in FIG. The protective device 20 is arranged in the pipe between the inlet of the ionic water production device 10 and the pump 15, the reverse osmosis membrane device 30, the protective device 20, and the electric deionized water production device 10 are arranged in this order. Good. In this specification, the outlet of the reverse osmosis membrane device 30 refers to the outlet of water that has permeated through the reverse osmosis membrane. The water treatment system shown to Fig.3 (a) becomes an example of the water treatment system based on this invention. Alternatively, as shown in FIG. 3 (b), a protection device 20 is provided in the front stage of the reverse osmosis membrane device 30, and the pump 15, the protection device 20, the reverse osmosis membrane device 30 and the electric deionized water production device 10 are arranged in this order. You may make it do. The reverse osmosis membrane included in the reverse osmosis membrane device 30 has low resistance to the oxidant as in the case of the ion exchange membrane and the ion exchanger, but the reverse osmosis membrane device is also protected from the oxidant as shown in FIG. can do. In the reverse osmosis membrane device 30, part of the water supplied to the reverse osmosis membrane device permeates the reverse osmosis membrane and the rest is discharged as concentrated water, so the amount of water supplied to the electrical deionized water production device 10 is small. If it is constant, the amount of water supplied to the protection device 20 is larger in the configuration shown in FIG. 3B than in the configuration shown in FIG. Therefore, from the viewpoint of miniaturization of the protection device 20, the configuration shown in FIG. 3A is preferable to the configuration shown in FIG.

  In each of the water treatment systems shown in FIGS. 1, 3 (a) and 3 (b), the pump 15 for passing the treated water through the protection device 20 is clearly shown, but the pump 15 is essential. Is not. If the protection device 20 is configured to allow the water to be treated to pass through the filler 21 at a predetermined space velocity, the pump 15 is not necessarily provided. Alternatively, when a flow of water to be treated has already been formed, a protective device that can insert into the flow a filler 21 having a volume that has a predetermined space velocity according to the flow rate of the water to be treated. It can also be 20.

Next, another example of the protection device 20 will be described. According to the experiments by the present inventors, when a weakly basic anion exchange resin is used as the filler, the TOC (total organic carbon) in the outlet water of the filler after the oxidant is injected when the oxidant flows into the filler. ) A tendency to slightly increase the concentration was observed. This is probably because the oxidizing agent deteriorates the weakly basic anion exchange resin, and as a result, a part of the weakly basic anion exchange resin (including positively charged anion exchange groups) flows out. Therefore, in the protection device 20, a cation exchange resin (CER) may be disposed downstream of the weakly basic anion exchange resin to reduce the TOC concentration. The cation exchange resin is preferably a strongly acidic cation exchange resin. FIG. 4 shows a protective device 20 in which a strongly acidic cation exchange resin 21c is disposed in the subsequent stage of the weakly basic anion exchange resin 21a. In the protection device 20 shown in FIG. 4 (a), the weakly basic anion exchange resin 21a and the strongly acidic cation exchange resin 21c are stored in separate containers 22, respectively, and the substrate that has passed through the weakly basic anion exchange resin 21a. The treated water then passes through the strongly acidic cation exchange resin 21c. In the protection device 20 shown in FIG. 4B, a single container 22 is used, and the container 22 is filled with weakly basic anion exchange resin 21a on the inlet side (inflow side) and on the outlet side (outflow side). The strongly acidic cation exchange resin 21c is filled. In any case, the volume of the weakly basic anion exchange resin is V _A and the volume of the strongly acidic cation exchange resin is V _C , so that V _A : V _C is in the range of 5: 2 to 5: 5. It is preferable to make it. In order to minimize the size of the protection device 20 as a whole, V _A : V _C may be set to 5: 2.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1]
With respect to the filler 21 provided in the protection device 20, the oxidant removal ability was compared with respect to the space velocity SV for various fillers. In the water treatment system shown in FIG. 1, the electric deionized water production apparatus 10 is removed, and the water to be treated is supplied to the protection device 20 via the pump 15. As the water to be treated, water having a free chlorine concentration of 0.5 to 0.6 mg / L is used, and the water discharged from the protective device 20 is changed while changing the type and space velocity of the filler 21 in the protective device 20. The chlorine concentration of the treated water was measured, and the oxidant removal rate was determined from the degree of reduction of the chlorine concentration in the treated water. As a filler,
[1-1] Gel-type strongly basic anion exchange resin (AER), trade name: Amberlite (registered trademark) IRA402BL,
[1-2] Gel-type strongly acidic cation exchange resin (CER), trade name: Amberlite (registered trademark) IR120B,
[1-3] As a mixed bed ion exchange resin, a gel-type strongly basic anion exchange resin, trade name: Amberlite (registered trademark) IRA402BL and a gel-type strongly acidic cation exchange resin, trade name: Amberlite (registered) (Trademark) IR120B mixed at a volume ratio of 1: 1,
[1-4] MR type strongly basic anion exchange resin, trade name: Amberlite (registered trademark) IRA904,
[1-5] MR type weakly basic anion exchange resin, trade name: Amberlite (registered trademark) XE583,
[1-6] Gel-type weakly basic anion exchange resin, trade name: Amberlite (registered trademark) IRA67, and
[1-7] Activated carbon using coconut shell as a raw material was used. The ion exchange resins shown in [1-1] to [1-6] are all manufactured by Dow Chemical Company. The results are shown in FIG. In the figure, the gel type is expressed as “(GEL)”, and the macroporous type is expressed as “(MR)”. From the figure, it can be seen that the weakly basic anion exchange resin has a higher oxidant removal efficiency than activated carbon, and also maintains the high oxidant removal ability even in a region where the space velocity is large.

[Example 2]
Using the same apparatus as Example 1, the time change of the oxidizing agent removal capability when the treated water was passed for a long time was examined. As filler
[2-1] MR type weakly basic anion exchange resin used in [1-5] of Example 1,
[2-2] Using the gel-type weakly basic anion exchange resin used in [1-6] of Example 1 and [2-3] activated carbon made from coconut shell as a raw material, with a space velocity of 1000 h ⁻¹ The treated water was passed through each filler for about 10 days. As water to be treated, water having a free chlorine concentration of 0.5 to 0.6 mg / L was used, and the oxidant removal rate was determined in the same manner as in Example 1. The results are shown in FIG. It has been found that the weakly basic anion exchange resin exhibits an oxidant removal rate of 50% or more even after 10 days (ie, 240 hours). Although the oxidant removal rate at the initial stage of water flow is higher in the gel type weakly basic anion exchange resin, the MR type weakly basic anion exchange resin having macropores may show a higher oxidant removal rate over a long period of time. I understood. Since it is preferable that the protective device 20 has a high oxidant removal rate over a long period of time, it can be seen that the MR type having macropores is more preferable as the weakly basic anion exchange resin used for the protective device 20.

[Example 3]
The protection device 20 shown in FIG. 4 (a) having a weakly basic anion exchange resin 21a in the front stage and a strong acid cation exchange resin 21c in the rear stage is prepared, and the total volume as the ion exchange resin is constant in water flow under, changing the ratio between the volume V _C of the volume V _a and a strongly acidic cation exchange resin 21c of the weakly basic anion exchange resin 21a, while flowing water to be treated, an inlet of the protection device 20, weakly basic anion exchange The TOC concentration at each of the outlet of the resin 21a and the outlet of the strongly acidic cation exchange resin 21c (that is, the outlet of the protective device 20) was measured. From the measured value of the TOC concentration, the increase / decrease ratio of the TOC at each outlet was determined with the TOC concentration at the inlet of the protective device 20 being 100%. As the water to be treated, water having a free chlorine concentration of 0.5 to 0.6 mg / L is used, and the flow rate of the water to be treated is 1000 h based on the volume of the weakly basic anion exchange resin 21a. ^{It was set to -1} . The weakly basic anion exchange resin 21a was the same as [1-6] in Example 1, and the strongly acidic cation exchange resin 21c was the same as [1-2] in Example 1. . The results are shown in Table 1.

When water to be treated containing an oxidizing agent is passed through a weakly basic anion exchange resin, the TOC concentration increases by about 20%. However, by placing a strongly acidic cation exchange resin in the subsequent stage, V _A : V _C is 5: It was found that when the ratio of the strongly acidic cation exchange resin is 2 or higher than that, the TOC concentration is lower at the outlet than at the inlet of the protective device 20.

10 Electric deionized water production equipment (EDI)
15 Pump 20 Protection device 21 Filler 21a Weakly basic anion exchange resin (AER)
21c Strongly acidic cation exchange resin (CER)
22 Container 23 Pressure gauge 30 Reverse osmosis membrane device (RO)

Claims (14)

In a water treatment system including a reverse osmosis membrane and an electric deionized water production device,
A protection device comprising a filler that is supplied with the treated water that has passed through the reverse osmosis membrane and removes the oxidant in the treated water;
The water to be treated that has passed through the filler is supplied to the electric deionized water production apparatus. 2. The supply device according to claim 1, further comprising a supply unit that supplies the water to be treated to the protection device so that a space velocity when the water to be treated is passed through the filler is 500 h ⁻¹ or more. Water treatment system.   The water treatment system according to claim 1 or 2, wherein the filler contains at least a weakly basic anion exchange resin.   The water treatment system according to claim 3, wherein the weakly basic anion exchange resin is a macroporous weakly basic anion exchange resin having macropores.   The said protection apparatus is equipped with the said weak basic anion exchange resin arrange | positioned at the inflow side of the said to-be-processed water, and the cation exchange resin arrange | positioned at the outflow side of the to-be-processed water as the said filler. Or the water treatment system of 3. The volume of the weakly basic anion exchange resin is V _A and the volume of the strongly acidic cation exchange resin is V _C , and V _A : V _C is in the range of 5: 2 to 5: 5. Water treatment system.   The water treatment system according to any one of claims 1 to 6, further comprising a pressure gauge that measures a pressure between an inlet and an outlet of the protection device. In an operation method of a water treatment system that includes an electric deionized water production apparatus and treats water to be treated containing chlorine,
The treated water is passed through the filler for removing the oxidizing agent in the treated water, and the treated water after passing through the filler is supplied to the electric deionized water production apparatus. The operation method of a water treatment system. The operation method according to claim 8, wherein a space velocity when the water to be treated is passed through the filler is 500 h ⁻¹ or more.   The operating method according to claim 8 or 9, wherein water to be treated that has passed through the filler is supplied to a reverse osmosis membrane, and water to be treated that has passed through the reverse osmosis membrane is supplied to the deionized water production apparatus.   The operation method according to claim 8, wherein the filler contains at least a weakly basic anion exchange resin.   The operating method according to claim 8, further comprising measuring a pressure difference between both sides of the filler to determine a degree of deterioration of the filler. A protective device that is detachably provided at the front stage of the electrical deionized water production device,
A filler for removing the oxidizing agent in the water to be treated;
A cartridge type container for storing the filler,
The space velocity when water to be treated is passed through the filler is 500 h ⁻¹ or more, and the water to be treated that has passed through the filler is supplied to the electric deionized water production apparatus. Protective device. The protection device according to claim 13, wherein the filler includes at least a weakly basic anion exchange resin.