JP2021007927A - Regeneration process of water softener, and manufacturing apparatus of desalted water - Google Patents

Abstract

To enable regeneration of a water softener without enhancing an apparatus capacity and adjusting an operation in a manufacturing system of desalted water having a RO membrane device installed at the latter stage of the water softener.SOLUTION: Concentrated wastewater of a RO membrane device is used as regeneration water for a water softener. A means for switching flow channels of raw water and the regeneration water is installed so that one water softener of two water softeners installed parallel is regenerated while the other water softener processes raw water. The water softener to be regenerated is supplied with the concentrated wastewater of the RO membrane device by the flow channel switching means.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for regenerating a water softener, and in particular, in a desalination water production system in which a reverse osmosis (RO) membrane device is arranged after the water softener, the concentrated drainage (RO membrane concentrated drainage) of the RO membrane device is softened. The present invention relates to a method for regenerating a water softener that is effectively used for regenerating a vessel and a demineralized water production device for that purpose.

Conventionally, as a desalination water production system, a desalination water production system is known in which raw water such as river water or industrial water is treated with a softener and then the treated water softened by this softener is treated with an RO membrane device. (For example, Patent Document 1), a pure water production apparatus incorporating this desalination water production system has also been put into practical use. By treating raw water with an ion exchange resin (cation exchange resin) -filled water softener in the first stage of the RO membrane device and adsorbing and removing hardness components such as calcium and magnesium with the ion exchange resin, the RO membrane device in the latter stage It is possible to prevent scale failure. The adsorption and removal of the hardness component in the water softener is specifically carried out by ion-exchange of calcium ions and the like with sodium ions of an ion exchange resin.

The ion exchange resin in the water softener that has adsorbed the hardness component by the water flow treatment of raw water needs to be regenerated by desorbing the hardness component on a regular basis or as necessary. For regeneration of the water softener, raw water of the water softener, soft water which is the treated water of the water softener, or a saline solution obtained by dissolving salt (sodium chloride) in the treated water of the RO membrane device (RO membrane permeated water) is usually used. ing.

Two water softeners are installed in parallel so that demineralized water can be continuously obtained even during the regeneration period of the water softener, and during the period when raw water is passed through one of the water softeners for treatment, the other. A desalination water production system has also been proposed in which the water softener is regenerated (regeneration and standby) so that water flow and regeneration can be switched alternately.

Japanese Unexamined Patent Publication No. 6-63549

The conventional method using raw water of a water softener, treated water of a water softener, or RO membrane permeated water as salt-dissolved water for regeneration of a water softener has the following problems.

That is, the amount of raw water supplied (water supply pump capacity) in a desalted water production system equipped with a water softener and an RO membrane device is the amount of water flowing through the water softener or the amount of water supplied to the subsequent RO membrane device (water softener and RO membrane device). It is designed in consideration of the capacity of the soft water tank installed between the two, but for example, two water softeners are installed in parallel to allow raw water to pass through one water softener and the other water softener is raw water. When regenerating by passing salt water using the above, two towers of raw water are temporarily required, so a water supply pump capacity commensurate with that is required. Normally, at the time of regeneration, the reclaimed water is passed at the same pressure and flow rate as at the time of passing the raw water, so that the water supply pump needs twice the capacity required for passing the raw water.
In addition, when soft water is used as the salt-dissolved water, the amount of water supplied to the RO membrane device may not be secured temporarily. Therefore, in this case as well, the water supply of the water softener is used to secure the amount of water supplied to the RO membrane device. It is necessary to increase the pump capacity or the capacity of the soft water tank.

In this way, when raw water, treated water (soft water), or RO membrane permeated water from the water softener is used as the water for regeneration of the water softener, the water supply capacity and tank capacity of the desalination water production system should be increased in anticipation of that amount. It is necessary and the initial cost is high. In addition, if the concentration of hardness components increases due to fluctuations in raw water quality and the frequency of water softener regeneration increases, a large amount of water for regeneration will be required, and it will be necessary to adjust the operation of the desalination water production system during regeneration. Become.

The present invention solves the above-mentioned problems of the prior art, and in a desalination water production system in which an RO membrane device is provided after the water softener, the water softener can be regenerated without requiring the enhancement of the device capacity or the operation adjustment. It is an object of the present invention to provide a method for regenerating a water softener and an apparatus for producing demineralized water.

As a result of repeated studies to solve the above problems, the present inventor has used RO membrane concentrated drainage to regenerate the water softener in a desalted water production system in which an RO membrane device is provided after the water softener. It was found that the water softener can be regenerated without the need to increase the equipment capacity of the water production system or adjust the operation, and the water cost can be reduced by effectively using the RO membrane concentrated wastewater.
That is, the gist of the present invention is as follows.

[1] A method for regenerating a water softener, which comprises using concentrated wastewater of the reverse osmosis membrane device as water for regeneration of the water softener in a desalted water production system in which a reverse osmosis membrane device is provided after the water softener. ..

[2] In a desalted water production system provided with a reverse osmosis membrane device after the water softener, the concentrated drainage of the reverse osmosis membrane device is used as the dissolved water of salt used for regeneration of the water softener. How to regenerate a water softener.

[3] In a desalted water production system in which a reverse osmosis membrane device is provided after the water softener, the concentrated drainage of the reverse osmosis membrane device is used as water for regeneration in a water softener of a water treatment system different from the desalted water production system. A method of regenerating a water softener, which is characterized by being used in a water softener.

[4] The method for regenerating a water softener according to [3], wherein the water treatment system is a water treatment system for boiler water supply.

[5] A water softener, a reverse osmosis membrane device for treating the treated water of the water softener, and a concentrated wastewater return means for passing the concentrated wastewater of the reverse osmosis membrane device to the water softener when the water softener is regenerated. Demineralized water production equipment equipped with.

[6] As the water softener, two towers of water softeners are provided in parallel, and the flow path of the raw water and the reclaimed water so that the raw water is reclaimed by the other water softener while the raw water is being treated by the one water softener. It is characterized in that it has a flow path switching means for switching between the above, and the flow path switching means is configured to allow the concentrated drainage to pass through the water softener for regeneration via the concentrated drainage return means [5]. ] The demineralized water production apparatus described in.

According to the present invention, it is necessary to enhance the device capacity of the desalted water production system and adjust the operation by effectively utilizing the concentrated wastewater of the RO membrane device provided at the subsequent stage of the water softener for the regeneration of the water softener. In addition to being able to regenerate the water softener, it is also possible to reduce water costs by effectively using RO membrane concentrated wastewater.

It is a system diagram which shows an example of embodiment of the demineralized water production apparatus of this invention.

Embodiments of the present invention will be described in detail below.

The method for regenerating a water softener of the present invention is characterized in that, in a desalted water production system in which an RO membrane device is provided after the water softener, concentrated wastewater of the RO membrane device is used as water for regeneration of the water softener.

The concentrated effluent of the RO membrane device is one in which salts and the like in the raw water are concentrated by the RO membrane device, but since it was treated with a water softener in the previous stage of the RO membrane device, it contains almost no hardness component and is used in the water softener. Since sodium ions are concentrated by ion exchange, it is suitable as water for regeneration in water softeners.
This RO membrane concentrated effluent is not only a water softener in the desalted water production system, that is, a water softener in the previous stage of the RO membrane device, but also a water softener in another water treatment system, for example, a water treatment system for boiler water supply. It can also be used as water for regeneration.

Normally, RO membrane concentrated wastewater is discharged to the outside of the system and treated as wastewater. Therefore, by effectively using RO membrane concentrated wastewater as water for regeneration in a water softener, not only the water cost for regeneration can be reduced. , The load of wastewater treatment can also be reduced.

In particular, when two water softeners are installed in parallel, one water softener is used to pass raw water, and the other water softener is used for regeneration (regeneration and standby), the raw water and water softener are treated as recycled water. When water or RO membrane permeated water is used, as described above, it is necessary to enhance the water supply capacity of the desalted water production system, increase the tank capacity, and further adjust the operation. However, by adopting the present invention, RO membrane concentrated drainage is required. By using the water for regeneration, such capital investment and operation adjustment can be eliminated.

The method for regenerating a water softener of the present invention is a switching method in which a demineralized water production system in which an RO membrane device is provided after the water softener can supply water for regeneration using concentrated drainage of the RO membrane device to the water softener instead of raw water. A valve, a means for supplying this regeneration water to the water softener at a pressure and flow rate equivalent to that of raw water, a concentrated drainage tank capable of storing the RO membrane concentrated drainage amount required for preparing the regeneration water for the regeneration of the water softener, and further. It can be easily carried out by incorporating an automatic control system that supplies raw water in the water flow process of the water softener and supplies water for regeneration using RO membrane concentrated wastewater in the regeneration process.

Generally, high-concentration saline solution (sodium chloride aqueous solution) is required for regeneration of the water softener, so at least a part of the RO membrane concentrated wastewater is used as salt-dissolved water for preparing saline solution for regeneration. It is preferable that the mixed water of the saline solution prepared by using the RO membrane concentrated drainage and the rest of the RO membrane concentrated drainage (when a part of the RO membrane concentrated drainage is a saline solution) is used as the regeneration water. In this case, the high-pressure RO membrane concentrated drainage functions as pressure water for passing the saline solution.

Hereinafter, the present invention will be described in more detail with reference to FIG.
FIG. 1 is a system diagram showing an example of an embodiment of a desalinated water production apparatus adopting the method for regenerating a water softener of the present invention.

In the demineralized water production apparatus of FIG. 1, when raw water is separated into demineralized water and concentrated effluent by the RO membrane apparatus 4, if the water supplied to the RO membrane apparatus 4 contains a large amount of hardness components such as calcium, this is the RO membrane apparatus. Since the RO membrane is blocked by the concentrated drainage in No. 4 and the calcium scale is generated, the water softeners 2A and 2B are configured to ion-exchange calcium with sodium to prevent the calcium scale in the RO membrane device 4. ..

When the raw water 1 is city water or the like, it contains chlorine and deteriorates the ion exchange resin and RO membrane in the water softener. Therefore, after removing chlorine with the activated carbon filter 1 in the previous stage of the water softeners 2A and 2B, the soft water Supply to vessels 2A and 2B. The water treated by the water softeners 2A and 2B is supplied to the RO membrane device 4 via the water softening tank 3.

The reason why the two water softeners 2A and 2B are provided in parallel is that the soft water in the water softening tank 3 is not constantly reduced, and the raw water is passed through one of the water softeners 2A and 2B for treatment, and the other Reproduction (regeneration and standby) processing.

A part of the RO membrane concentrated drainage separated by the RO membrane device 4 is sent to the salt water tank 6 as salt-dissolved water, and the rest is stored in the concentrated drainage tank 5. The amount exceeding the capacity of the concentrated drainage tank 5 is discharged to the outside of the system as overflow drainage.

The saline solution used for regeneration is prepared by mixing sodium chloride (concentrated saline solution) from the pipe 25 and RO membrane concentrated wastewater supplied as salt-dissolved water from the pipe 19B in the salt water tank 6. Saline prepared with brine tank 6, from line 27 with a check valve V _3, is injected from the ejector 7 disposed RO membrane concentration waste water takeout pipe 21 from concentrate sump 5. The NaCl concentration of the saline solution prepared in the salt water tank 6 is about 20 to 26% by weight (saturation concentration), and such a saline solution is injected into the RO membrane concentrated drainage with an ejector to regenerate the NaCl concentration of about 5 to 10% by weight. It is preferable to supply water to the water softeners 2A and 2B as water.

The effective capacity of the concentrated drainage tank 5 is the capacity for injecting salt-dissolved water and using it as water for regeneration of the water softeners 2A and 2B, and it is set to one dose or a plurality of doses depending on the operation. When the concentrated drainage in the concentrated drainage tank 5 is also used for regeneration of a water softener of a water treatment system other than the water softeners 2A and 2B, for example, a water softener of a water treatment system for boiler water supply, the required amount is used. The capacity should be commensurate.

The operation method of this demineralized water production apparatus will be described below.
First, the raw water valve V _1A is opened, the raw water valve V _1B is closed, the water supply pump P ₁ is operated, and the raw water is introduced into the water softener 2A via the pipe 11, the activated charcoal filter 1, the pipes 12, 13A and 14A. The softened water obtained after the softening treatment is introduced into the RO membrane device 4 via the pipes 15A and 16, the water softening tank 3 and the pipe 17, and the RO membrane is treated. The demineralized water which is the RO membrane permeated water is used as the treated water from the pipe 18. Take it out. A part of the RO membrane concentrated drainage is supplied to the salt water tank 6 via the pipes 19 and 19B, and the rest is supplied to the concentrated drainage tank 5 from the pipe 19A.

After the treatment by the water softener 2A is continued for a predetermined time, the raw water valve V _1A is closed, the raw water valve V _1B is opened, the raw water supply destination is switched to the water softener 2B, and the raw water is piped 11, the activated charcoal filter 1, and the pipe. It was introduced into the water softener 2B via 12, 13B and 14B for softening treatment, and the obtained soft water was introduced into the RO membrane device 4 via the pipes 15B and 16 and the water softening tank 3 and the pipe 17 for RO membrane treatment and RO. Demineralized water, which is permeated water, is taken out from the pipe 18 as treated water. A part of the RO membrane concentrated drainage is supplied to the salt water tank 6 from the pipes 19 and 19B, and the rest is supplied to the concentrated drainage tank 5 from the pipe 19A.

At the same time as switching the raw water valves V _1A and V _1B , the regeneration pump P ₂ is operated and the regeneration valve V _2A is opened (if the regeneration valve V _2B is open, the regeneration valve V _2B is closed) to concentrate. The RO membrane concentrated drainage in the drainage tank 5 is sent to the water softener 2A via the pipes 21, 22A and 14A to regenerate the water softener 2A. The saline solution prepared in the salt water tank 6 is injected from the ejector 7 into the supply pipe 21 of the RO membrane concentrated drainage, and the soft water 2A is regenerated with the mixed water of the RO membrane concentrated drainage and the saline solution.
In this way, the water softener 2A is regenerated during the period in which the raw water is passed through the water softener 2B. The regenerated wastewater is discharged to the outside of the system via pipes 23A and 24.
After regeneration of the water softener 2A is completed by passing water a mixed water of a predetermined time RO membrane concentration waste water and brine, waiting the playback valve V _2A stops the regenerative pump P ₂ is closed, until the water flow of the following raw water To do.

After the treatment by the water softener 2B is continued for a predetermined time, the raw water valve V _1B is closed, the raw water valve V _1A is opened, the raw water supply destination is switched to the water softener 2A, and as described above, the raw water is softened by the water softener 2A. while passing water in the order of water tank 3, RO membrane device 4 actuates the regenerative pump _{P 2,} playing a valve _{V 2B} is opened (when the playback valve _{V 2A} was opened is closed regeneration valve _{V 2A),} The mixed water of the RO membrane concentrated drainage in the concentrated drainage tank 5 and the salt solution from the salt water tank 6 is supplied to the water softener 2B via the pipes 21, 22B and 14B to regenerate the water softener 2B. That is, the water softener 2B is regenerated during the period in which the raw water is passed through the water softener 2A. Regenerated wastewater is discharged to the outside of the system via pipes 23B and 24.
After regeneration of the water softener 2B is finished by passing water a mixed water of a predetermined time RO membrane concentration waste water and brine, waiting the playback valve V _2B stops the regenerative pump P ₂ is closed, until the water flow of the following raw water To do.

By switching between water flow and regeneration of the water softeners 2A and 2B in this way, desalinated water can be continuously produced.

The above valve switching and pump operation can be performed by automatic control by the automatic control system.

FIG. 1 shows an example of an embodiment of the desalinated water production apparatus of the present invention, and the desalted water producing apparatus of the present invention is not limited to that of FIG.
For example, if there is no restriction on the regeneration time of the water softener, the concentrated drainage tank 5 is omitted, and the mixed water of the RO membrane concentrated drainage and the saline solution, which is the pressure water, is directly supplied to the regeneration valves V _2A and V _2B. You may.
When the raw water does not contain chlorine, the activated carbon filter 1 can be omitted, and an ion exchange pure water device, an electroregenerative pure water device, or the like may be provided after the RO membrane device 4.

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

[Example 1]
The demineralized water production apparatus shown in FIG. 1 was used to produce demineralized water using city water as raw water and to regenerate a water softener using RO membrane concentrated wastewater.
As the water softener and RO membrane device, those having the following specifications were used.

<Water softener>
"KS-SA-20D" manufactured by Kurita Water Industries, Ltd. 2 towers <RO membrane device>
"KN-400R" manufactured by Kurita Water Industries, Ltd.

The water softener should regenerate the mixed water (NaCl concentration 5-10% by weight) of RO membrane concentrated drainage and saline (NaCl concentration 20-26% by weight) every 24 hours of raw water flow for 2 hours. The flow path of the two water softeners was switched, and demineralized water was produced by continuous water flow.
The water quality of raw water (city water), treated water of water softener (soft water), RO membrane concentrated wastewater, and RO membrane permeated water is as follows.

<Raw water>
Conductivity: 175 μS / m
pH: 7.8
Ca: 20 mg / L
Mg: 4 mg / L
M-Alkaline: 49 mg CaCO ₃ / L
<Soft water>
Conductivity: 166 μS / m
pH: 7.9
Ca: <1.0 mg / L
Mg: <1.0 mg / L
M-Alkaliity: 48 mg CaCO ₃ / L
<RO membrane concentrated wastewater>
Conductivity: 498 μS / m
pH: 8.1
Ca: 1.0 mg / L
Mg: <1.0 mg / L
M-Alkaliity: 145 mg CaCO ₃ / L
<RO membrane permeated water>
Conductivity: 3 μS / m

As a result, it was confirmed that the water softener, the RO membrane concentrated drainage, and the permeated water quality did not change even after continuous operation for 30 days, and the water softener could be sufficiently regenerated using the RO membrane concentrated drainage.

1 Activated carbon filter 2A, 2B water softener 3 Soft water tank 4 RO membrane device 5 Concentrated drainage tank 6 Salt water tank

Claims (6)

A method for regenerating a water softener, which comprises using concentrated wastewater of the reverse osmosis membrane device as water for regeneration of the water softener in a desalted water production system provided with a reverse osmosis membrane device after the water softener. In a desalted water production system in which a reverse osmosis membrane device is provided after the water softener, the water softener is characterized in that the concentrated drainage of the reverse osmosis membrane device is used as the dissolved water of salt used for regeneration of the water softener. Playback method. In a desalted water production system in which a reverse osmosis membrane device is provided after the water softener, the concentrated wastewater of the reverse osmosis membrane device is used as water for regeneration of a water softener of a water treatment system different from the desalted water production system. A method of regenerating a water softener, which is characterized in that. The method for regenerating a water softener according to claim 3, wherein the water treatment system is a water treatment system for boiler water supply. A water softener, a reverse osmosis membrane device for treating the treated water of the water softener, and a concentrated wastewater return means for passing the concentrated wastewater of the reverse osmosis membrane device to the water softener when the water softener is regenerated. Salt water production equipment. As the water softener, two towers of water softeners are provided in parallel, and a flow that switches the flow path of the raw water and the reclaimed water so that the raw water is reclaimed by the other water softener while the raw water is being treated by the one water softener. The fifth aspect of claim 5, wherein the concentrated drainage is configured to have a path switching means, and the concentrated drainage is passed through the water softener for regeneration via the concentrated wastewater return means. Demineralized water production equipment.

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