TW201806875A - 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<SP>2-</SP>or CO3<SP>2-</SP>. The invention provides a water treatment method including: a softening step of softening a water to be treated, containing SO4<SP>2-</SP>and/or CO3<SP>2-</SP>, a hardness component, and Na<SP>+</SP>and Cl<SP>-</SP>, 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 apparatus suitable for treating, for example, drainage from the electronics industry. The present invention also relates to a method for regenerating an ion exchange resin.

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

In addition, Patent Document 2 discloses a steam plant and a method for operating the same that can reduce water consumption. This document describes that water softened in a softening container provided with a resin is passed through a reverse osmosis device provided with a semi-permeable membrane, the permeated water of the reverse osmosis device is supplied to a boiler, and the concentrate of the reverse osmosis device is used in the softened container. regeneration. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 50-105546 [Patent Document 2] Japanese Patent Application Publication No. 2013-212504

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

However, in the water treatment method using an ion exchange resin and a reverse osmosis membrane, when the water to be treated contains sulfate ion SO ₄ ^2- and carbonate ion CO ₃ ^2- , these divalent anions are concentrated by the ion exchange resin. In concentrated water of reverse osmosis membrane. If this concentrated water is used for the regeneration of ion exchange resin, there is a concern about the precipitation of CaSO ₄ and CaCO _3. Therefore, at this time, the concentrated water of the reverse osmosis membrane should be avoided for the regeneration of ion exchange resin.

On the other hand, the regeneration agent used for the regeneration of the ion exchange resin used for softening treatment generally uses high-concentration NaCl aqueous solution, but the cost of the regeneration agent is expensive, and the operation becomes complicated because of the need to dissolve solid NaCl.

The object of the present invention is to provide a water treatment method, which is a water treatment method using an ion exchange resin and a reverse osmosis membrane, even when the water to be treated contains sulfate ion SO ₄ ^2- and carbonate ion CO ₃ ^2- . Regeneration of ion exchange resin can be performed at a lower cost and more easily.

Another object of the present invention is to provide a water treatment apparatus suitable for carrying out the method.

Still another object of the present invention is to provide an ion exchange resin regeneration method capable of regenerating ion exchange resin at a lower cost and easier, and in particular, to make reverse osmosis obtained from a water treatment method using an ion exchange resin and a reverse osmosis membrane. The membrane concentrated water can be used for regeneration of ion exchange resin even when the water to be treated in the water treatment contains sulfate ion SO ₄ ^2- and carbonate ion CO ₃ ^2- . [Means for solving problems]

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

According to another aspect of the present invention, there is provided: a water treatment device including: a softening device provided with an ion exchange resin; a nanofiltration device provided with a nanofiltration membrane; a reverse osmosis device provided with a reverse osmosis membrane; and the softening device A line connecting the softened water outlet to the inlet of the nanofiltration device; a line connecting the permeate water outlet of the nanofiltration device to the inlet of the reverse osmosis device; and a concentrated liquid outlet of the reverse osmosis device to the softening Piping to the regenerant inlet of the unit.

According to still another aspect of the present invention, there is provided: a method for regenerating an ion exchange resin, including the following steps: a softening step, using the ion exchange resin to include a group 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 ^- treated water are softened; the nanofiltration step uses a nanofiltration membrane to separate the water softened by the softening step into nanometers. The permeated water and concentrated solution of the filter membrane; the reverse osmosis step, which uses the reverse osmosis membrane to separate the permeated water of the nanofiltration membrane into the permeate water and concentrated water of the reverse osmosis membrane; The concentrated water regenerates an ion exchange resin (either an ion exchange resin used in the softening step, or an ion exchange resin different from the ion exchange resin used in the softening step). [Effect of the invention]

According to the present invention, there is provided a water treatment method, which is a water treatment method using an ion exchange resin and a reverse osmosis membrane. Even when the water to be treated contains sulfate ion SO ₄ ² and carbonate ion CO ₃ ^2- , Low cost and easier regeneration of ion exchange resin.

Furthermore, according to the present invention, there is provided a water treatment apparatus suitable for carrying out the method.

Furthermore, according to the present invention, there is provided an ion exchange resin regeneration method capable of regenerating ion exchange resin at a lower cost and easier, and in particular, a reverse osmosis membrane concentrate obtained from a water treatment method using an ion exchange resin and a reverse osmosis membrane. Water can be used for regeneration of ion exchange resin even when the water to be treated in the water treatment contains sulfate ion SO ₄ ^2- and carbonate ion CO ₃ ^2- .

The water treatment method or the regeneration method of the ion exchange resin 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] In the present invention, the NaCl blocking rate is at least 5% and less than 93% under the conditions of NaCl concentration of 500mg / L, pH6.5, temperature of 25 ° C, and operating pressure of 1.5MPa. The membrane is called a nanofiltration membrane (NF), and a membrane having a NaCl blocking rate of 93% or more 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, the treated water is softened using an ion exchange resin. 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 a sulfate ion SO ₄ ^2- and a carbonate ion CO ₃ ^2- . The divalent anion is especially SO ₄ ^2- .

It is well-known in the field of water treatment of a hardness component, and is generally a divalent cation represented by Ca ²⁺ and Mg ²⁺ . In the softening step, the concentration of the hardness component is reduced.

As the ion exchange resin, a well-known ion exchange resin used in softening treatment can be suitably used. Particularly, a strongly acidic cation exchange resin of Na type can be suitably used. There are gel type, porous type, and MR type. . As the ion exchange resin, for example, Amberjet 1020 (trade name, the same applies hereinafter), Amberjet 1024, Amberlite IR124, Amberlite IR120B, etc., manufactured by Olgaonau Corporation.

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

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

The NF membrane is used to reduce the divalent anion (SO ₄ ^2- and / or CO ₃ ^2- ) concentration of the liquid supplied to the RO membrane in advance. Therefore, when the concentrated water of the RO membrane is used for the regeneration of the ion exchange resin, the precipitation of CaSO ₄ and CaCO ₃ can be prevented. Therefore, the divalent anion should be concentrated in the concentrated water of the NF membrane as much as possible. On the other hand, it is desirable to make monovalent ions (Na ⁺ and Cl ⁻ ) pass through the NF membrane as much as possible, and make it exist in the concentrated water of the RO membrane as much as possible, and use it as a regeneration agent for the ion exchange resin.

From this viewpoint, the blocking rate of NaCl of the NF film is preferably 70% or less, and more preferably 50% or less. The blocking ratio of the divalent anion (SO ₄ ^2- and / or CO ₃ ^2- ) of the NF film is preferably 90% or more, and more preferably 98% or more.

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

[Reverse osmosis step] In this step, permeate water of the NF membrane is passed through the RO membrane to obtain permeate 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 RO membrane (the liquid that has passed through the RO membrane) and the RO membrane concentrated water (the liquid that has not penetrated the RO membrane).

The permeated water of the RO membrane is high-purity water. Therefore, it can be discharged to the outside world, but it is preferably reused 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 concentrations of SO ₄ ^2- and CO ₃ ^{2- in} the concentrated water of the RO membrane can be reduced to very low. Therefore, this concentrated water is suitable as a regeneration agent for ion exchange resin and can be supplied to the ion exchange resin regeneration step.

From the viewpoint of making the RO membrane concentrated water contain more Na ⁺ and Cl ⁻ , the RO membrane should be suitable for users at higher pressures.

As the RO film, 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 concentrated water of the RO membrane. The concentrated water of RO membrane can be used as a regenerant of ion exchange resin used in softening treatment. That is, when the treated water is treated in the softening step, the nanofiltration step, and the reverse osmosis step, the concentrated water of the RO membrane obtained from the reverse osmosis step can be used for the ion exchange resin used in the softening step. regeneration. A water treatment method or a water treatment apparatus usually adopts this form.

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

Before the regeneration of the ion exchange resin, NaCl may be added to the concentrated water of the RO membrane as needed to increase the NaCl concentration. In addition, the concentrated water of the RO membrane may be further concentrated by other methods such as evaporation, and then used as a regenerant.

It is also possible to perform other treatments on the concentrated water of the RO membrane before performing 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, the concentrated water of the RO membrane can be treated by a decarbonation method or the like.

[Water Treatment Device] Hereinafter, the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The method of the present invention can be carried out by using a water treatment apparatus having the flow shown in FIG. 1.

This water treatment device includes a softening device 3 including an ion exchange resin, a nanofiltration device (NF device) 4 including a nanofiltration membrane, and a reverse osmosis device (RO device) 5 including a reverse osmosis membrane. The structure of each of the softening device, the nanofiltration device, and the reverse osmosis device may be a known structure as appropriate. The softened water outlet of the softening device 3 and the inlet of the NF device 4 are connected by a line L2 and can communicate. The permeate water outlet of the NF device 4 and the inlet of the RO device 5 are connected by a line L3 so as to communicate. The concentrated liquid outlet of the RO device 5 and the regenerant inlet of the softening device 3 are connected and connected by lines L6 and L7 (the RO membrane concentrated water tank 6 is provided between these lines).

Moreover, this water treatment apparatus has the to-be-processed water tank 1, and the pump 2 is provided in the pipeline (L1) which connects the to-be-processed water tank 1 and the softening apparatus 3. The treated water tank 1, the pump 2, and the RO membrane concentrated water tank 6 are not necessarily required, and may be appropriately installed. When the RO membrane concentrated water tank 6 is not provided, the concentrated liquid outlet of the RO device and the regeneration agent inlet of the softening device are connected by a pipeline. In this case, for example, a softening device of a plurality of systems may be provided, and the ion exchange resin in the other systems may be regenerated while the water treatment is performed in one system.

Each line can be suitably constituted by a piping. For the purpose of switching between the water treatment operation and the ion exchange resin regeneration operation, a valve and an instrument control unit can be appropriately installed in each pipeline.

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

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

[Processing Conditions] In Tables 1 and 2, representative examples of the 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 from the NaCl concentration in the concentrated water obtained in the RO step, it is preferably 2% by mass or more, and more preferably 4% by mass or more. From the viewpoint of proper osmotic pressure, it is preferably 10% by mass or less. When the representative processing conditions shown in Tables 1 and 2 are used, the result is likely to make the NaCl concentration in the RO membrane concentrated water within the aforementioned preferred range.

The NaCl concentration in the RO membrane permeating 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 (No. 2)

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

According to the present invention, the softened water is treated with an NF film before being treated with an RO film. Compared with the case where the RO membrane is used to treat the softened water directly, according to the present invention, the salt concentration in the RO membrane to-be-treated liquid can be reduced, and the osmotic pressure can be reduced. Therefore, it is easy to increase the concentration ratio of the RO membrane and increase the NaCl concentration in the RO membrane concentrated solution, or it can further reduce the operating pressure of the RO membrane.

If aluminum ions and ionic silica coexist, it will sometimes promote the formation of silica scale. 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 aluminum ions from flowing into the NF membrane and the RO membrane in the subsequent stage. [Example]

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

[Example 1] Softening step The semiconductor factory discharged water whose properties are shown in Table 3 was used as the liquid to be treated. The discharged water was subjected to a softening treatment using a softening device including an 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) used and the operating conditions are as follows: Ion exchange resin: Amberjet 1020 (trade name) manufactured by Olgaonau Co., Ltd., resin amount: 1L, used column: Φ (diameter) 45mm × H ( Height) 600mm, water flow: 40L, SV (space velocity): 20 (1 / h), operating temperature, pressure: normal temperature, normal pressure (25 ° C, 0.10MPa).

[Table 3] Discharge water

･ NF step The demineralized water shown in Table 3 was concentrated using a NF flat film to obtain the concentrated water and permeated water shown in Table 4. The softened water (40L) was concentrated twice to obtain 20L of concentrated water and 20L of permeated water.

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

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

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

[Table 4] Test results of Example 1

The RO membrane concentrated water has high Na ⁺ and Cl ^- concentrations and can be directly used as a regeneration agent for ion exchange resins. In addition, NF membrane concentrated water and RO membrane permeated water were discarded.

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

[Table 5] Test results of Comparative Example 1

At the same operating pressure (4.5 MPa) as in Example 1, only about 8-fold concentration due to the influence of osmotic pressure was achieved. RO membrane of Example 1 and the concentrated water Comparative Embodiment, Comparative Example 1 of the RO concentrate the membrane Na ^+, Cl ^- concentration slightly lower. Since this RO membrane concentrated water contains high concentration of SO ₄ ² , it is not suitable as a regenerant for ion exchange resin (the possibility of CaSO ₄ precipitation during ion exchange resin regeneration is high). [Industrial availability]

The present invention is useful for treating wastewater from factories such as semiconductor factories and sugar refineries and recovering high-purity water.

1‧‧‧ treated sink
2‧‧‧ pump
3‧‧‧softening device
4‧‧‧nano filter device (NF device)
5‧‧‧ reverse osmosis device (RO device)
6‧‧‧RO membrane concentrated water tank
L1 ~ L8‧‧‧ pipeline

[Fig. 1] A processing flowchart showing an example of a water treatment device of the present invention.

1‧‧‧ treated sink

2‧‧‧ pump

3‧‧‧softening device

4‧‧‧nano filter device (NF device)

5‧‧‧ reverse osmosis device (RO device)

6‧‧‧RO membrane concentrated water tank

L1 ~ L8‧‧‧ pipeline

Claims (6)

A water treatment method includes the following steps: a softening step, using an ion exchange resin, containing one or two types of divalent anions, hardness components, selected from the group consisting of SO ₄ ^2- and CO ₃ ^2- , The treated water of Na ⁺ and Cl ^- is softened; the nanofiltration step uses a nanofiltration membrane to separate the water softened by the softening step into the permeated water and concentrated solution of the nanofiltration membrane; the reverse osmosis step uses reverse The osmosis membrane separates the permeated water of the nanofiltration membrane into permeated water and concentrated water of the reverse osmosis membrane; and an ion exchange resin regeneration step, using the concentrated water of the reverse osmosis membrane to regenerate the ion exchange resin. The patentable scope of application of the treatment method of item 1, wherein, after the step of softened water and softened, SO ₄ ^2- concentration of 10mg / L or more 10000mg / L or less, CO ₃ ^2- in terms of CaCO ₃ content of 10mg / L or less. For example, the water treatment method of item 1 or 2 of the patent application scope, wherein the permeation water of the nanofiltration membrane has a SO ₄ ^2- concentration of less than 10 mg / L. For example, the water treatment method according to item 1 or 2 of the patent application scope, wherein the divalent anion is SO ₄ ^2- . A water treatment device comprising: a softening device provided with an ion exchange resin; a nanofiltration device provided with a nanofiltration membrane; a reverse osmosis device provided with a reverse osmosis membrane; and a softened water outlet of the softening device connected to the nanofiltration device Inlet pipeline; a pipeline connecting the permeate water outlet of the nanofiltration device to the inlet of the reverse osmosis device; and a pipeline connecting the concentrated liquid outlet of the reverse osmosis device to the regenerant inlet of the softening device. A method for regenerating an ion exchange resin includes the following steps: a softening step, using the ion exchange resin to contain one or two divalent anions selected from the group consisting of SO ₄ ^2- and CO ₃ ^2- , The treated water of hardness components, Na ⁺ , and Cl ^- is softened; the nanofiltration step uses a nanofiltration membrane to separate the water softened by the softening step into permeated water and a concentrated solution of the nanofiltration membrane; a reverse osmosis step Using a reverse osmosis membrane to separate the permeate water of the nanofiltration membrane into permeate water and concentrated water of the reverse osmosis membrane; and an ion exchange resin regeneration step, using the concentrated water of the reverse osmosis membrane to regenerate the ion exchange resin.