TWI727046B - Water treatment method and apparatus, and method of regenerating ion exchange resin - Google Patents

Abstract

In a water treatment method that uses an ion exchange resin and a reverse osmosis membrane, the ion exchange resin can be regenerated more easily and at lower cost, even when the water being treated contains SO₄ ^2- or CO₃ ^2- . The invention provides a water treatment method including: a softening step of softening a water to be treated, containing SO₄ ^2- and/or CO₃ ^2- , a hardness component, and Na⁺ and Cl^- , using an ion exchange resin; a nanofiltration step of separating the water softened in the softening step into a nanofiltration membrane permeate and concentrate using a nanofiltration membrane; a reverse osmosis step of separating the permeate from the nanofiltration membrane into a reverse osmosis membrane permeate and concentrate using a reverse osmosis membrane; and an ion exchange resin regeneration step of regenerating the ion exchange resin using the concentrate from the reverse osmosis membrane. Also provided is a water treatment apparatus suitable for carrying out this method. The invention also provides a method of regenerating an ion exchange resin containing the above softening step, the above nanofiltration step, the above reverse osmosis step, and a step of regenerating the ion exchange resin using the concentrate from the reverse osmosis membrane.

Description

Water treatment method, water treatment device and regeneration method of ion exchange resin

The present invention relates to a water treatment method and device suitable for treating, for example, drainage from the electronics industry. Furthermore, the present invention relates to a regeneration method of ion exchange resin.

A water treatment method using ion exchange resin and reverse osmosis membrane is known. Patent Document 1 discloses that waste water containing free acid in the copper drawing industry, the plating industry, the steel industry, or the food industry is passed through an ion exchange resin and then separated into a concentrated liquid and a membrane permeate by a reverse osmotic pressure method.

In addition, Patent Document 2 discloses a steam plant and its operation method that can reduce water consumption. This document states that the water softened by a softening vessel equipped with resin is passed through a reverse osmosis device equipped with a semipermeable membrane, the permeated water of the reverse osmosis device is supplied to a boiler, and the concentrated liquid of the reverse osmosis device is used in the softening vessel. regeneration. [Prior Technical Document] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 50-105546 [Patent Document 2] Japanese Patent Laid-Open No. 2013-212504

[Problem to be Solved by the Invention] According to the technology described in Patent Document 2, by using the concentrated liquid of the reverse osmosis device for the regeneration of the softening vessel (resin), the use of raw water usually used for washing the softening vessel can be reduced.

However, for water treatment methods using ion exchange resins and reverse osmosis membranes, when the water to be treated contains sulfuric acid ions SO ₄ ^2- and carbonate ions CO ₃ ^2- , these divalent anions will be concentrated by the ion exchange resin In the concentrated water of the reverse osmosis membrane. If this concentrated water is used for the regeneration of ion exchange resins, there are _{concerns about the precipitation of CaSO 4} and CaCO _3. Therefore, at this time, avoid using the concentrated water of the reverse osmosis membrane for the regeneration of ion exchange resins.

On the other hand, the regenerating agent used to regenerate the ion exchange resin used for softening treatment generally uses high-concentration NaCl aqueous solution, but the cost of the regenerating agent is expensive, and the operation becomes complicated due to the step of dissolving the solid NaCl.

The purpose of the present invention is to provide: a water treatment method using ion exchange resins and reverse osmosis membranes, even when the water to be treated contains sulfuric acid ions SO ₄ ^2- and carbonate ions CO ₃ ^2- The regeneration of ion exchange resin can be carried out at a lower cost and easier.

Another object of the present invention is to provide a water treatment device suitable for implementing the above method.

Yet another object of the present invention is to provide an ion exchange resin regeneration method that can regenerate ion exchange resins at a lower cost and more easily, especially the reverse osmosis obtained from a water treatment method using ion exchange resins and reverse osmosis membranes. Membrane concentrated water can be used for the regeneration of ion exchange resin even if the water to be treated contains sulfuric acid ions SO ₄ ^2- and carbonate ions CO ₃ ^2-. [Means to solve the problem]

According to one aspect of the present invention, there is provided: a water treatment method, including the following steps: a softening step, using an ion exchange resin to include one selected from the group consisting of SO ₄ ^2- and CO ₃ ^2- or Two kinds of divalent anions, hardness components, Na ⁺ , and Cl ^- are softened by the treated water; in the nanofiltration step, the water softened by the softening step is separated into the permeate water of the nanofiltration membrane using a nanofiltration membrane. And concentrated liquid; the reverse osmosis step, using a reverse osmosis membrane to separate the permeated water of the nanofiltration membrane into permeated water and concentrated water of the reverse osmosis membrane; and the ion exchange resin regeneration step, using the concentrated water of the reverse osmosis membrane The ion exchange resin is regenerated.

According to another aspect of the present invention, there is provided: a water treatment device, comprising: a softening device with ion exchange resin; a nanofiltration device with a nanofiltration membrane; a reverse osmosis device with a reverse osmosis membrane; and the softening device The outlet of the softened water is connected to the pipeline of the inlet of the nanofiltration device; the outlet of the permeate water of the nanofiltration device is connected to the inlet of the reverse osmosis device; and the outlet of the concentrated liquid of the reverse osmosis device is connected to the softening The pipeline of the regenerant inlet of the device.

According to yet another aspect of the present invention, there is provided: a method for regenerating an ion exchange resin, comprising the following steps: a softening step, using an ion exchange resin to include a resin selected from the group consisting of SO ₄ ^2- and CO ₃ ^2- One or two of the divalent anions, hardness components, Na ⁺ , and Cl ^- are softened by the treated water; in the nanofiltration step, the water softened by the softening step is separated into nanometers using a nanofiltration membrane. Permeate water and concentrated liquid of the membrane; reverse osmosis step, use a reverse osmosis membrane to separate the permeated water of the nanofiltration membrane into permeated water and concentrated water of the reverse osmosis membrane; ion exchange resin regeneration step, use the reverse osmosis membrane The concentrated water regenerates the ion exchange resin (the ion exchange resin used in the softening step, or the ion exchange resin different from the ion exchange resin used in the softening step). [Effects of Invention]

According to the present invention, there is provided: a water treatment method using ion exchange resin and reverse osmosis membrane, even when the treated water contains sulfuric acid ions SO ₄ ² and carbonate ions CO ₃ ^2- Low-cost and simpler regeneration of ion exchange resin.

Furthermore, according to the present invention, a water treatment device suitable for implementing the above method is provided.

Furthermore, according to the present invention, there is provided an ion exchange resin regeneration method that can regenerate ion exchange resins at a lower cost and more easily, in particular, a reverse osmosis membrane concentration obtained from a water treatment method using ion exchange resins and reverse osmosis membranes Water, even if the water to be treated contains sulfuric acid ions SO ₄ ^2- and carbonate ions CO ₃ ^2- , it can still be used for the regeneration of ion exchange resins.

The water treatment method or ion exchange resin regeneration method of the present invention includes: a softening step, a nanofiltration step, a reverse osmosis step, and an ion exchange resin regeneration step.

[Nanofiltration membrane, reverse osmosis membrane] Regarding the present invention, the NaCl barrier rate will be greater than 5% and less than 93% under the conditions of NaCl concentration of 500 mg/L, pH 6.5, temperature of 25°C, and operating pressure of 1.5 MPa. The membrane is called a nanofiltration membrane (NF), and the membrane with a NaCl barrier rate of over 93% under the same conditions is called a reverse osmosis (RO) membrane.

The blocking rate can be obtained by the following formula.

【Number 1】

[Softening step] In the softening step, an ion exchange resin is used to soften the water to be treated. Treated water contains divalent anion, hardness components, a sodium ion Na ^+, chloride ions and Cl ^-. The divalent anion is one or two selected from the group consisting of sulfuric acid ion SO ₄ ^2- and carbonate ion CO ₃ ^2- . The divalent anion is especially SO ₄ ^2- .

Hardness components are well-known in the field of water treatment, and are generally divalent cations represented by ^{Ca 2+} and Mg ^2+. In the softening step, the concentration of the hardness component will be reduced.

As the ion exchange resin, known ion exchange resins used in softening treatment can be suitably used, especially Na-type strong acid cation exchange resins can be suitably used. There are gel type, porous type, and MR type, any of which can be used. . As the ion exchange resin, for example, Amberjet 1020 (trade name, the same hereinafter) manufactured by Olugano Co., Ltd., Amberjet 1024, Amberlite IR124, Amberlite IR120B, etc. can be used.

[Nanofiltration step] In this step, the water softened by the softening step (softened water) is passed through the NF membrane to obtain permeated water and concentrated water of the NF membrane. That is, the NF membrane is used to separate the demineralized water into permeated water of the NF membrane (liquid that has passed through the NF membrane) and concentrated water of the NF membrane (liquid that has not passed through the NF membrane).

The permeated water of the NF membrane is supplied to the reverse osmosis step. Depending on the concentration of divalent anions, the concentrated water of the NF membrane can be appropriately discharged to the outside or treated as industrial waste.

The NF membrane is used to reduce the concentration of _{divalent anions (SO 4} ^2- and/or CO ₃ ^2- ) in the liquid supplied to the RO membrane in advance. _{This prevents CaSO 4} and CaCO _{3 from} separating out when the concentrated water of the RO membrane is used for the regeneration of ion exchange resins. Therefore, it is advisable to concentrate the divalent anions in the concentrated water of the NF membrane as much as possible. On the other hand, desirable that the monovalent ions (Na ⁺ and Cl ^-) NF membrane permeable as possible, and a large amount as it present in the membrane of the RO water and concentrated, using as regenerant an ion exchange resin.

From this point of view, the NaCl barrier rate of the NF film is preferably 70% or less, and more preferably 50% or less. In addition, the blocking rate of the divalent anions (SO ₄ ^2- and/or CO ₃ ^2- ) of the NF membrane is preferably 90% or more, and more preferably 98% or more.

As the NF membrane, for example, NF-245 (trade name) manufactured by The Dow Chemical Company can be used.

[Reverse Osmosis Step] In this step, the permeated water of the NF membrane is passed through the RO membrane to obtain the permeated water and concentrated water of the RO membrane. That is, the RO membrane is used to separate the permeated water of the NF membrane into the permeated water of the RO membrane (liquid that has passed through the RO membrane) and the concentrated water of the RO membrane (liquid that has not passed through the RO membrane).

The permeate water of RO membrane is high purity water. Therefore, it can also be discharged to the outside, but it is better to reuse it as recycled water.

^{Na +} and Cl ^- are concentrated in the concentrated water of the RO membrane. On the other hand, SO ₄ ^2- and CO ₃ ^2- are blocked by the NF membrane, and the concentration of SO ₄ ^2- and CO ₃ ^{2- in} the concentrated water of the RO membrane can be reduced to a very low level. Therefore, this concentrated water is suitable as a regeneration agent for ion exchange resin and can be supplied to the regeneration step of ion exchange resin.

From the point of view that the RO membrane concentrate water contains more Na ⁺ and Cl ^- , the RO membrane is suitable for users under higher pressure.

For the RO membrane, for example, SW-30HR (trade name) manufactured by The Dow Chemical Company can be used.

[Ion exchange resin regeneration step] In this step, the ion exchange resin is regenerated using RO membrane concentrated water. The concentrated water of RO membrane can be used as a regeneration agent of ion exchange resin used in softening treatment. That is, when the water to be treated is treated in a softening step, a nanofiltration step, and then a reverse osmosis step, the concentrated water of the RO membrane obtained from the reverse osmosis step can be used as the ion exchange resin used in the softening step. regeneration. Water treatment methods or water treatment devices usually adopt this form.

However, it is not limited to this, and the concentrated water of the RO membrane can also be used to regenerate an ion exchange resin different from the ion exchange resin used in the softening step. The regeneration method of the ion exchange resin can adopt the aforementioned form (regenerate the ion exchange resin used in the softening treatment), and this form can also be adopted.

It is also possible to increase the concentration of NaCl by adding NaCl to the concentrated water of the RO membrane as needed before the regeneration of the ion exchange resin. In addition, the concentrated water of the RO membrane can also be used as a regenerating agent after being further concentrated by other methods such as evaporation.

It is also possible to perform other treatments on the concentrated water of the RO membrane as needed before the regeneration of the ion exchange resin. For example, in order to remove SO ₄ ^2- and CO ₃ ^2-, or to remove fluoride ions (F ^-), may utilize an ion exchange resin, a fluorine adsorbent way to handle the concentrated water RO membranes. Alternatively, decarbonation method can be used to treat the concentrated water of the RO membrane.

[Water Treatment Apparatus] Hereinafter, the present invention will be described with reference to the drawings, but the present invention is not limited to this. The method of the present invention can be implemented using a water treatment device having the process shown in FIG. 1.

This water treatment device includes a softening device 3 equipped with ion exchange resin, a nanofiltration device (NF device) 4 equipped with a nanofiltration membrane, and a reverse osmosis device (RO device) 5 equipped with a reverse osmosis membrane. The structure of each device of the softening device, the nanofiltration device, and the reverse osmosis device may suitably adopt a well-known structure. The softened water outlet of the softening device 3 and the inlet of the NF device 4 are connected by a pipeline L2 and can be communicated. The permeated water outlet of the NF device 4 and the inlet of the RO device 5 are connected by a pipeline L3 and can be communicated. The outlet of the concentrated liquid of the RO device 5 and the inlet of the regenerant of the softening device 3 are connected by lines L6 and L7 (the RO membrane concentrated water tank 6 is provided between these lines) and can be communicated.

In addition, this water treatment device has a water tank 1 to be treated, and a pump 2 is provided in a pipeline (L1) connecting the water tank 1 to be treated and the softening device 3. The treated water tank 1, pump 2, and RO membrane concentration water tank 6 are not necessarily required, and can be appropriately installed. When the RO membrane concentrated water tank 6 is not installed, connect the concentrated liquid outlet of the RO device and the regenerant inlet of the softening device with a pipeline. In this case, for example, multiple systems of softening devices can be installed, and while one system is performing water treatment, the ion exchange resins of other systems can be regenerated.

Each pipeline can be appropriately constituted by piping. For the purpose of switching between water treatment operation and ion exchange resin regeneration operation, valves and instrument control units can be appropriately installed in each pipeline.

When the water treatment is performed, the water to be treated is supplied from the water tank 1 to be treated to the softening device 3 through the line L1. At this time, the pressure of the water to be treated is boosted by pump 2. The softened water is supplied from the softening device 3 to the NF device 4 through the line L2. The permeate of the NF membrane is supplied to the RO device through the line L3. The concentrated water of the NF membrane is discharged from the water treatment device through the line L4, and is appropriately discharged to the outside or treated as industrial waste. The permeate of the RO membrane is discharged to the outside of the device through the line L5, and can be suitably used as recycled water or discharged to the outside. The concentrated liquid of the RO membrane is supplied to the RO membrane concentrated water tank 6 through the line L6.

When the ion exchange resin provided in the softening device 3 is regenerated, the RO membrane concentrated water is supplied to the softening device from the RO membrane concentrated water tank 6 through the line L7, and the ion exchange resin is regenerated by the RO membrane concentrated water. The regeneration waste liquid is discharged from the pipeline L8 to the outside of the water treatment device, and is appropriately discharged to the outside or treated as industrial waste.

[Treatment conditions] In Tables 1 and 2, representative examples of processing conditions are shown for the softening step supply liquid (water to be treated), the NF step supply liquid (softened water), and the RO step supply liquid (NF membrane permeated water).

From the viewpoint of efficiently regenerating the ion exchange resin, the NaCl concentration in the concentrated water obtained from the RO step is preferably 2% by mass or more, and more preferably 4% by mass or more. Moreover, from the viewpoint of an appropriate osmotic pressure, it is preferably 10% by mass or less. If the representative treatment conditions shown in Tables 1 and 2 are used, the result is that the NaCl concentration in the RO membrane concentrated water is easily within the aforementioned preferable range.

The NaCl concentration in the RO membrane permeate water is preferably 150 mg/L or less from the viewpoint of recycling.

【Table 1】Typical processing conditions (Part 1)

【Table 2】Typical processing conditions (Part 2)

According to the present invention, even when the water to be treated contains SO ₄ ^2- and CO ₃ ^2- , the RO membrane concentrate can still be used for the regeneration of ion exchange resins. Therefore, the cost of the regenerant of the ion exchange resin can be reduced, and the step of dissolving solid NaCl can be omitted, so the operation management becomes easy.

According to the present invention, the softened water is treated with NF membrane before it is treated with RO membrane. Compared with the case where the RO membrane is directly used to treat the softened water, the present invention can reduce the salt concentration in the RO membrane to be treated liquid, which can also reduce the osmotic pressure. Therefore, it is easy to increase the concentration ratio of the RO membrane to increase the NaCl concentration in the RO membrane concentrate, or to further reduce the operating pressure of the RO membrane.

In addition, if aluminum ions and ionic silica coexist, sometimes the formation of silica scale will be promoted. However, according to the present invention, even when aluminum ions coexist in the water to be treated, the aluminum ions can be removed by the ion exchange resin, thereby preventing the aluminum ions from flowing into the NF membrane and the RO membrane in the subsequent stage. [Example]

Hereinafter, the present invention will be explained in more detail based on examples, but the present invention is not limited to this.

[Example 1] ･Softening step The discharged water from a semiconductor factory whose properties are shown in Table 3 was used as the liquid to be treated. The discharged water is softened using a softening device equipped with ion exchange resin to remove Ca ions. The properties of the softened water are also shown in Table 3.

The softening device (ion exchange device) and operating conditions used are as follows: Ion exchange resin: Amberjet1020 (trade name) manufactured by Olugano Co., Ltd., resin volume: 1L, column used: Φ (diameter) 45mm×H( Height) 600mm, water flow: 40L, SV (space velocity): 20 (1/h), operating temperature and pressure: normal temperature, normal pressure (25°C, 0.10MPa).

[Table 3] Discharge water state

･NF step Use the NF flat membrane to concentrate the demineralized water shown in Table 3 to obtain the concentrated water and permeate water shown in Table 4. The softened water (40L) was concentrated twice to obtain 20L concentrated water and 20L permeated water.

The used NF membrane and operating conditions are as follows: NF membrane: NF-245 (trade name) Φ75mm flat membrane manufactured by The Dow Chemical Company, operating pressure: 0.75 MPa, water temperature: 25°C.

･RO step Next, use RO flat membrane to further concentrate the permeated water of the NF membrane to obtain the concentrated water and permeated water shown in Table 4. NF membrane permeate water (20L) was concentrated about 12 times to obtain 1.7L of concentrated water and 18.3L of permeated water.

The RO membrane used and the operating conditions are as follows: RO membrane: SW30-HR (trade name) Φ75mm flat membrane manufactured by The Dow Chemical Company, operating pressure: 4.5 MPa, water temperature: 25°C.

[Table 4] Test results of Example 1

This RO membrane concentrated water ^{contains high concentrations of Na +} and Cl ^- and can be directly used as a regenerant for ion exchange resins. In addition, the NF membrane concentrated water and RO membrane permeate water are discarded.

[Comparative Example 1] The demineralized water (40L) shown in Table 3 was not treated with NF membrane, but was directly concentrated using RO flat membrane. The RO membrane used at this time is the same as the operating pressure and water temperature of the RO step as in Example 1. The demineralized water was concentrated about 8 times to obtain the concentrated water (5L) and permeated water (35L) shown in Table 5.

[Table 5] Test results of Comparative Example 1

Under the same operating pressure (4.5 MPa) as in Example 1, the concentration can only reach about 8 times due to the influence of osmotic pressure. Compared with the RO membrane concentrated water of Example 1, the RO membrane concentrated water of Comparative Example 1 has a slightly lower ^{concentration of Na +} and Cl ^-. This RO membrane concentrated water contains a high concentration of SO ₄ ² , so it is not suitable as a regeneration agent for ion exchange resins ( _{the possibility of CaSO 4} precipitation during ion exchange resin regeneration is high). [Industrial Utilization]

The invention is helpful for processing wastewater from factories such as semiconductor factories, sugar refineries, etc., and recovering high-purity water.

1‧‧‧The treated water tank 2‧‧‧Pump 3‧‧‧Softening device 4‧‧‧Nano filter device (NF device) 5‧‧‧Reverse Osmosis Device (RO Device) 6‧‧‧RO membrane concentrating water tank L1~L8‧‧‧Pipeline

[Figure 1] is a processing flow chart showing an example of the water treatment device of the present invention.

1‧‧‧The treated water tank

2‧‧‧Pump

3‧‧‧Softening device

4‧‧‧Nano filter device (NF device)

5‧‧‧Reverse Osmosis Device (RO Device)

6‧‧‧RO membrane concentrating water tank

L1~L8‧‧‧Pipeline

Claims (6)

A water treatment method includes the following steps: a softening step, using an ion exchange resin to contain one or two divalent anions _{selected from the group consisting of SO 4} ^2- and CO ₃ ^{2-, hardness components,} The drainage of Na ⁺ and Cl ^- is softened; in the nanofiltration step, the water softened by the softening step is separated into the permeate and concentrated liquid of the nanofiltration membrane by the nanofiltration membrane; in the reverse osmosis step, the reverse osmosis membrane is used Separating the permeated water of the nanofiltration membrane into permeated water and concentrated water of the reverse osmosis membrane; and the ion exchange resin regeneration step, using the concentrated water of the reverse osmosis membrane to regenerate the ion exchange resin; The NaCl barrier rate is below 70%, and the barrier rate of the divalent anion of the nanofiltration membrane is above 90%. For example, the water treatment method of item 1 in the scope of patent application, wherein the SO ₄ ^2- concentration in the water softened by the softening step is 10 mg/L or more and 10,000 mg/L or less, and the CO ₃ ^2- content is 10 mg/L in terms of CaCO ₃ Below L. For example, the water treatment method of item 1 or 2 in the scope of patent application, wherein the _{concentration of SO 4} ^{2- in} the permeated water of the nanofiltration membrane does not reach 10 mg/L. For example, the water treatment method of item 1 or 2 in the scope of patent application, wherein the divalent anion is SO ₄ ^2- . A water treatment device comprising: a softening device provided with an ion exchange resin, which is supplied with one or two divalent anions _{selected from the group consisting of SO 4} ^2- and CO ₃ ^{2-, and a hardness component} , Na ⁺ , and Cl ^- drainage; nanofiltration device with nanofiltration membrane; reverse osmosis device with reverse osmosis membrane; pipeline connecting the softened water outlet of the softening device to the inlet of the nanofiltration device; The pipeline connecting the permeate outlet of the nanofiltration device to the inlet of the reverse osmosis device; and the pipeline connecting the concentrate outlet of the reverse osmosis device to the regenerant inlet of the softening device; the NaCl barrier of the nanofiltration membrane The rate is less than 70%, and the barrier rate of the divalent anion of the nanofiltration membrane is more than 90%. An ion exchange resin regeneration method, comprising the following steps: a softening step, using ion exchange resin to contain one or two divalent anions _{selected from the group consisting of SO 4} ^2- and CO ₃ ^2-, Hardness components, Na ⁺ , and Cl ^- drainage softening; nanofiltration step, use nanofiltration membrane to separate the water softened by this softening step into permeate water and concentrated liquid of nanofiltration membrane; reverse osmosis step, use The reverse osmosis membrane separates the permeated water of the nanofiltration membrane into permeated water and concentrated water of the reverse osmosis membrane; and the ion exchange resin regeneration step uses the concentrated water of the reverse osmosis membrane to regenerate the ion exchange resin; the nanofiltration The NaCl barrier rate of the membrane is below 70%, and the barrier rate of the divalent anion of the nanofiltration membrane is above 90%.

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