JP2013096701A - Water treatment method and water treatment facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment method for treatment target water containing radioactive materials, which realizes easy management.SOLUTION: In a water treatment method, treatment target water containing radioactive materials is separated into concentrated water in which concentration of the radioactive materials is increased and permeated water in which the concentration is decreased by using a reverse osmotic membrane, and then an adsorption treatment of adsorbing the radioactive materials to an adsorbent which can adsorb the radioactive materials is performed by bringing the concentrated water into contact with the adsorbent. At least part of the adsorption-treated water after the adsorption treatment is returned to processes before membrane separation.

Description

  The present invention relates to a water treatment method and a water treatment facility for treating water to be treated containing a radioactive substance, and more particularly, to a water treatment method and a water treatment facility using an adsorbent capable of adsorbing a radioactive substance. .

In recent years, peaceful use of radioactivity has been actively performed, and radioactive waste generated by peaceful use has been vitrified and buried.
In facilities using such radioactivity, waste storage facilities contaminated with radioactive materials, and landfill sites (final disposal sites), radioactive materials may be leaked unexpectedly, There is a risk of radioactive contamination of groundwater and surrounding soil.
In addition, in the landfill site for waste contaminated with radioactive material, when rain occurs, leachate containing radioactive material is generated, and if the leachate is not properly treated, the contaminated area is further expanded. There is a risk of letting you.

As a water treatment method for treating water containing a radioactive substance such as leachate, a method using an adsorbent is known.
That is, water containing radioactive material is treated water, the treated water is brought into contact with an adsorbent capable of adsorbing the radioactive material, and the radioactive material is adsorbed on the adsorbent to adsorb the treated water after the adsorption treatment. Conventionally known is a water treatment method in which the concentration of the radioactive substance is lower than that of the water to be treated before the adsorption treatment.

  With regard to such a water treatment method, for example, Patent Document 1 below describes that a water treatment facility in which an adsorption treatment unit for carrying out an adsorption treatment is constituted by an adsorbent packed tower is used, and a radioactive substance is used. It describes that the concentration of radioactive substances in the water to be treated is lowered by bringing the water to be treated into contact with the adsorbent in the adsorbent packed tower.

JP 2000-206291 A

In addition, this kind of water to be treated may contain organic substances that are required to be removed separately from radioactive substances.
However, if a biological treatment using activated sludge or the like is performed separately from the radioactive substance adsorption treatment for the decomposition and removal of the organic matter, a new treatment object such as excess sludge may be generated.
Moreover, if the surplus sludge contains a radioactive substance, dehydration of the surplus sludge may increase the concentration of the radioactive substance.

  By the way, in the “Ionizing Radiation Hazard Prevention Regulation” (hereinafter also referred to as “ionization law”) established by the Ministry of Health, Labor and Welfare, for example, cesium with a radioactive concentration exceeding 10,000 Bq / kg is particularly strict as a radioactive substance. In the radiation hazard prevention guidelines established in Tokyo, special management is required for fly ash exceeding 8,000 Bq / kg.

  Therefore, when dewatering excess sludge as described above to produce a dehydrated cake or the like, the dehydrated cake may need to be managed based on the ionization law or the like.

  Such a problem is not limited to water to be treated containing organic substances. For example, when a metal ion to be removed is contained, an attempt is made to remove the chelate resin by using a chelate resin. At this time, it is necessary to pay attention to the radioactivity concentration. If the radioactivity concentration of the chelate resin exceeds the above-described concentration, it may be necessary to manage based on the ionization law.

  This invention makes it a subject to solve the above problems, and makes it a subject to provide the water treatment method with easy management in the water treatment method of the to-be-processed water containing a radioactive substance.

  The present invention according to the water treatment method for solving the above-described problems is directed to a reverse osmosis membrane in which water to be treated containing a radioactive substance is converted into a concentrated water having an increased concentration of the radioactive substance and a permeated water having a reduced concentration. At least after adsorbing the adsorbed water after adsorbing the adsorbent by adsorbing the radioactive material to the adsorbent by contacting the concentrated water with an adsorbent capable of adsorbing the radioactive substance after membrane separation using A part is returned to the process before the membrane separation.

  In addition, the present invention relating to a water treatment facility for solving the above-described problems is that the water to be treated containing a radioactive substance is formed into a membrane having concentrated water with an increased concentration of the radioactive substance and permeated water with a reduced concentration. A membrane separation unit having a reverse osmosis membrane separation device for separation, and a concentrated water obtained by the reverse osmosis membrane separation device of the membrane separation unit and an adsorbent capable of adsorbing a radioactive substance are brought into contact with the adsorbent. And a return means for returning at least a part of the adsorption treated water adsorbed by the adsorption treatment unit before the membrane separation unit. It is characterized by being provided.

According to the present invention, since membrane separation is performed using a reverse osmosis membrane, not only radioactive substances but also organic substances can be contained on the concentrated water side.
Therefore, it is possible to reduce the necessity of performing a biological treatment or the like separately from the radioactive substance adsorption treatment so that the permeated water does not contain organic substances or the like.
That is, the possibility that a dehydrated cake having a high concentration of radioactive substance is formed can be suppressed, and a situation where special management is required for the dehydrated cake can be avoided.
Therefore, according to the present invention, a water treatment method that can be easily managed can be provided.

It is a block diagram showing a schematic structure of water treatment equipment concerning one embodiment of the present invention. It is a fragmentary sectional view showing a schematic structure of a membrane separation module of a reverse osmosis membrane separation device used in water treatment equipment concerning one embodiment of the present invention. It is a block diagram which shows schematic structure of the water treatment equipment which concerns on other embodiment of this invention.

In the following, the embodiment of the water treatment method of the present invention is illustrated with an example in which leachate from a landfill site (final disposal site) where radioactive pollutants are buried is treated water. This will be described with reference to FIG.
FIG. 1 is a block diagram showing a schematic configuration of a water treatment facility used in the present embodiment, and reference numeral 1 in the figure represents a landfill disposal that may leach out treated water (raw water) introduced into the water treatment facility. Reference numeral 2 represents a receiving tank for storing leachate discharged from the landfill disposal site 1.
Reference numeral 200 represents a membrane separation unit for membrane-separating water to be treated containing a radioactive substance into concentrated water with an increased concentration of the radioactive substance and permeated water with a reduced concentration.
Further, reference numerals 10 and 20 in the figure are adsorption treatment units each containing an adsorbent capable of adsorbing a radioactive substance, and 10 is a first to the treated water on the upstream side of the membrane separation unit 200. A first adsorption processing unit (hereinafter also referred to as “first adsorption processing unit”) for carrying out the adsorption treatment, and 20 performs the second adsorption treatment on the concentrated water obtained by the membrane separation unit 200. A second adsorption processing unit (hereinafter also referred to as “second adsorption processing unit”).
Furthermore, the broken line A represents the management area which performs management based on the radioactive concentration and quantity in the water treatment facility of the present embodiment.
As shown in this figure, in the present embodiment, the first adsorption processing unit 10 is installed in the management area, and other components such as the second adsorption processing unit 20 and the membrane separation unit 200 are It is located outside the management area.

In the water treatment facility of the present embodiment, as shown in FIG. 1, the first adsorption treatment unit 10, the primary treated water storage unit 30, and the security filter unit in the order in which leachate leached from the landfill disposal site 1 is processed. 130, the membrane separation unit 200, and the second adsorption processing unit 20 are provided.
Further, in the water treatment facility of the present embodiment, an evaporating and concentrating unit in which salts and radioactive substances contained in the adsorbed water after being adsorbed in the second adsorption processing unit 20 are concentrated by evaporating water. 160 and a condensed water storage unit 170 for storing condensed water obtained by condensing water evaporated by the evaporation and concentration unit 160 is further provided.
Further, the water treatment facility of the present embodiment has a return means 50 for returning the condensed water to the first adsorption processing unit 10.

The water treatment facility of the present embodiment includes a first membrane separation that separates the water to be treated into concentrated water and permeated water, and the permeated water obtained by the first membrane separation into concentrated water and permeated water. The membrane separation unit 200 is provided with two reverse osmosis membrane separation devices 140 and 150 so that the membrane separation can be carried out in at least two stages of the second membrane separation to be separated, and the first Permeated water of a second reverse osmosis membrane separation device 150 (hereinafter also referred to as “second reverse osmosis membrane separation device”) that performs the second membrane separation is configured to be discharged out of the system as treated water.
Further, the water treatment facility of the present embodiment includes concentrated water obtained by a first reverse osmosis membrane separation device 140 (hereinafter also referred to as “first reverse osmosis membrane separation device”) that performs the first membrane separation, Each of the concentrated water and the concentrated water obtained by the second reverse osmosis membrane separation device 150 can be supplied to the second adsorption processing unit 20 as treated water to be adsorbed by the second adsorption processing unit 20. It is configured.

  The first membrane separation device 140 is a reverse osmosis membrane separation device having a planar membrane type module, and turbulent flow is formed on the surface of the planar reverse osmosis membrane by the water to be subjected to membrane separation. The second membrane separation device 150 is preferably a reverse osmosis membrane separation device having a spiral type reverse osmosis membrane module, a hollow fiber type reverse osmosis membrane module or a pleated type reverse osmosis membrane module.

  As the reverse osmosis membrane separation device having this flat membrane type module, a plurality of spacers 7 as shown in FIG. 2 are arranged, and a reverse osmosis membrane (plane membrane 6) is interposed between the spacers 7. What is provided with the planar membrane type module 4 made.

The planar membrane type module 4 shown in FIG. 2 has a structure in which disk type planar membranes and spacers with dimples are alternately laminated.
Specifically, in the planar membrane type module 4, a disk-like planar membrane (reverse osmosis membrane) 6 is provided between the disc-like spacers 7 in a cylindrical reverse osmosis membrane module body 5. A plurality of reverse osmosis membrane portions 8 are laminated.
The reverse osmosis membrane separation device is provided with a treated water channel 9 for introducing treated water on the inner peripheral surface of the reverse osmosis membrane module main body 5, and is treated from the treated water channel 9 around the reverse osmosis membrane. Water is introduced, and the turbulent flow due to the water to be treated is formed on the surface of the planar film 6 by the introduction of the water to be treated.
In addition, an end plate 3 is provided on the reverse osmosis membrane portion 8 so as to withstand a pressure higher than the osmotic pressure.
In the planar membrane type module 4 shown in FIG. 2, the permeated water pipe 11 is passed through the central portion of the reverse osmosis membrane portion 8.
In the flat membrane type module 4, the permeated water separated by the reverse osmosis membrane is discharged by the permeate pipe 11, and the concentrated water concentrated by each reverse osmosis membrane is discharged to the outside of the module body 5 by the concentrated water pipe 12. It is configured to be discharged.

It is preferable to provide the reverse osmosis membrane separation device having such a planar membrane type module on the front stage side of the two-stage membrane separation apparatus, the latter side spiral type reverse osmosis membrane module, hollow fiber type reverse osmosis This is because the formation of deposits on the membrane surface is suppressed as compared with a reverse osmosis membrane separation device having a membrane module or a pleated reverse osmosis membrane module.
On the other hand, since the permeated water of the reverse osmosis membrane separation device having a flat membrane type module is introduced on the rear stage side, there is a low possibility that deposits are formed on the membrane surface, and the membrane area with respect to the size of the device It is preferable to use a reverse osmosis membrane separation apparatus having a spiral type reverse osmosis membrane module, a hollow fiber type reverse osmosis membrane module, or a pleated type reverse osmosis membrane module that can easily secure a large amount of water.

In the present embodiment, the concentrated water obtained by the membrane separation unit 200 configured by these reverse osmosis membrane separation devices is returned to the first adsorption processing unit 10 through the second adsorption processing unit 20, for example. The
In addition, from the second adsorption processing unit 20 to the first adsorption processing unit 10, all or only a part of the adsorption treated water adsorbed by the second adsorption processing unit 20 may be returned. .
In addition, even when organic matter or metal ions are contained in the liquid to be treated, the permeated water of the second membrane separation device 150 contains organic matter or metal ions exceeding the discharge standard value outside the system. Can be suppressed.
Therefore, it is possible to reduce the necessity of performing a process such as biological treatment or chelate treatment, and for example, it is also possible to reduce the necessity of a process such as pH adjustment or coagulation precipitation that is performed accompanying the biological treatment. .

  On the other hand, since the radioactive substance is adsorbed through the second adsorption processing unit 20 and the first adsorption processing unit 10, the concentration thereof is sufficiently reduced, and the radioactive substance in the permeated water of the second membrane separation device 150 is reduced. The concentration can be suitable for discharging out of the system.

In the present embodiment, the second adsorption processing unit 20 is constituted by an adsorption tower having a container for accommodating an adsorbent and an adsorbent accommodated in the container, and one of the containers It is comprised by the adsorption tower comprised so that the to-be-processed water introduce | transduced from might be moved to the other side of a container and discharged | emitted, contacting the adsorption material inside this container.
That is, the adsorption tower has an adsorption treatment in which the radioactive substance contained in the treated water is adsorbed by the adsorbent due to the contact between the treated water and the adsorbent, and the concentration of the radioactive substance is lower than the treated water. Configured to get water.

In the second adsorption processing unit 20, when the radioactive substance to be adsorbed is radioactive cesium, radioactive iodine, radioactive strontium, or the like, the adsorbent to be contained in the container is an aluminosilicate such as zeolite. Minerals; phyllosilicate minerals such as mica and sericite; ferrocyan compounds such as potassium ferrocyanide, cobalt ferrocyanide, and ferrocyanide can be suitably used.
In addition, when using these substances as an adsorbent, they may be used alone or in combination.
In that case, these can be used in the form of a powder or a porous material obtained by sintering the powder.
On the other hand, the material of the container is not particularly limited as long as it does not cause a significant decrease in physical properties due to radiation.

When the second adsorption processing unit 20 is configured by such an adsorption tower, the first adsorption processing unit 10 is several times as large as the container containing the adsorbent in the adsorption tower of the second adsorption processing unit 20. It is preferable to use a concrete tank (hereinafter also referred to as “concrete tank”) having a volume of several tens or more times.
In addition, the concrete tank of the 1st adsorption | suction processing part 10 in this embodiment is provided in the form by which a surrounding wall and a bottom face wall are formed with the concrete which has fixed thickness in a part of said landfill disposal site, and the inside and outside are provided. It is provided to be completely isolated.
In addition, the first adsorption processing unit 10 accommodates the adsorbent in the concrete tank so as to have a constant deposition thickness, and forms an adsorbent layer of the adsorbent therein, and the adsorbent from the ground portion. It has a suction tube that extends through the layers toward the bottom of the concrete tank.
As the adsorbent for forming the adsorbent layer in the first adsorption processing unit 10, the same material as that described for the second adsorption processing unit 20 can be adopted.
However, the adsorbent used in the first adsorption processing unit 10 is not necessarily the same as the adsorbent used in the second adsorption processing unit 20, and the shape, material, etc. are different from those used in the second adsorption processing unit 20. It may be.
Conversely, the adsorbent used with the second adsorption processing unit 20 may be used in common, and the adsorbent layer may be formed of the same adsorbent as the second adsorption processing unit 20.

In the present embodiment, the first adsorption treatment unit 10 uses leachate leached from the landfill site due to rain or the like as treated water, and the treated water passes through the receiving tank 2 to be treated water. As the primary treated water, the primary treated water storage part is pumped up from the bottom of the concrete tank to the ground through the suction pipe and the treated water that has been introduced from the top of the concrete tank and passed through the adsorbent layer as a downward flow. 30 so that it can flow down to 30.
That is, the first adsorption treatment unit 10 is configured to be able to reduce the concentration of radioactive material in the treated water by adsorbing the radioactive material in the treated water that passes through the adsorbent layer to the adsorbent. .

  Moreover, the concrete tank which comprises the said 1st adsorption process part 10 has sufficient storage space above the said adsorbent layer, and replaces the adsorbent of said 2nd adsorption process part 20 with a new thing so that it may mention later. It is preferable that the adsorbent that has been used in the second adsorption processing unit 20 until then is newly deposited on the adsorbent layer and used for the adsorption treatment in the concrete tank.

In the present embodiment, the first adsorption processing unit 10 has a mode in which the adsorption treatment water after adsorbing the radioactive substance on the adsorbent is pumped from the concrete tank through the suction pipe provided in the concrete tank. Although illustrated as a specific method of the adsorption treatment, a water discharge port may be provided at the bottom of the concrete tank to discharge the water subjected to the adsorption treatment from the bottom of the concrete tank.
However, it is preferable that the first adsorption processing unit is configured so as to be a closed space that is finally completely cut off from the outside, and it is preferable not to provide a discharge port or the like at the bottom. It is preferable to employ a concrete tank having an opening only on the upper side.

The primary treated water storage unit 30 provided on the rear stage side of the first adsorption treatment unit has a flow rate when the adsorption treated water subjected to the adsorption treatment by the first adsorption treatment unit 10 is used for the subsequent treatment. And an adjustment tank for stabilizing the water quality.
Further, the return means 50 for returning the adsorption treated water from the second adsorption treatment section 20 to the first adsorption treatment section 10 is not particularly limited as long as it is a means for transporting a liquid. And using a pump or the like.

In the water treatment method of treating leachate using such a water treatment facility, the adsorbent of the second adsorption treatment unit 20 has a radioactivity concentration of 10,000 Bq / kg or less, preferably 8,000 Bq. In order to simplify the water treatment method, it is preferable to perform an adsorbent replacement step of replacing the adsorbent with a new adsorbent in a state of less than / kg.
That is, by handling the adsorbent of the second adsorption processing unit 20 in a state showing the radioactive concentration as described above, it is possible to reduce the necessity of performing strict management prescribed in the ionization law or the like for handling of the adsorbent. be able to.
In addition, if the adsorbent replacement process is performed in a state where the adsorbent of the second adsorption processing unit 20 has an excessively low radioactivity concentration, the adsorbent replacement process must be frequently performed, and water treatment is performed. This is not preferable from the viewpoint of efficiency.
Therefore, the adsorbent replacement step is preferably performed in a state where the radioactive concentration of the adsorbent in the second adsorption processing unit 20 is 6,400 Bq / kg or more.

In addition, about what radioactivity concentration the adsorbent of the second adsorption processing unit 20 has, the radioactive substance content of the concentrated water introduced into the second adsorption processing unit 20 and the second adsorption The radioactive substance content of the adsorbed treated water flowing down from the processing unit 20 can be compared and predicted from the treated water amount.
Normally, the permeated water discharged out of the system from the second reverse osmosis membrane separation device 150 contains only a trace amount so that its influence can be ignored even if it contains a radioactive substance. Even if the radioactive material content of the water stored in the adjustment tank in the treated water storage unit 30 is measured instead of the radioactive material content of the concentrated water, the amount of the adsorbent in the second adsorption processing unit 20 is the same. It can be predicted whether the concentration is radioactive

However, since it usually takes time to measure water quality, another method is to measure the air dose in the vicinity of the second adsorption processing unit and compare it with the data on the relationship between the adsorption amount and the air dose prepared in advance. Thus, a method for estimating the radioactivity concentration inside the adsorption tower can also be adopted.
According to this method, since the air dose can be measured immediately, the amount of adsorption at the time of the measurement can be reflected, and the replacement timing can be managed accurately.
In addition, since the relationship between the amount of adsorption and the air dose may be different for each adsorbent, it is preferable to measure data for each adsorbent.

Moreover, in the water treatment method of this embodiment, it is adsorbed that the adsorbent of the second adsorption processing unit 20 replaced in the adsorbent replacement step is used for the adsorption processing in the first adsorption processing unit 10. This is suitable for suppressing the consumption of the material.
That is, the adsorbent used for the second adsorption treatment is preferably replaced with a new one at a radioactivity concentration of 10,000 Bq / kg or less, and in some cases 8,000 Bq / kg or less. Usually, if the radioactivity concentration is about this level, it still has sufficient adsorption performance, so it is preferable to effectively use this in the first adsorption treatment.

In the preferable water treatment facility of the present embodiment, the adsorbent accommodation space in the first adsorption treatment unit 10 is significantly larger than the adsorbent accommodation space in the second adsorption treatment unit 20. Thus, even if the adsorbent replacement process is carried out several times or several tens of times, the old adsorbent that was accommodated in the adsorption tower before the adsorbent replacement process is put into the concrete tank of the first adsorption processing unit 10. Can be accommodated.
Here, by adding the adsorbent used so far in the second adsorption processing unit 20 to the adsorbent of the first adsorption processing unit 10 and increasing the thickness of the adsorbent layer of the first adsorption processing unit, The amount of radioactive material adsorbed in the first adsorption processing unit 10 can be increased as compared with that before, and even when leachate having the same concentration of radioactive material is generated, after the adsorbent replacement process (replacement) The concentration of radioactive material in the adsorbed treated water that flows down toward the primary treated water storage unit 30 after the adsorbent is accommodated in the first adsorbing treatment unit) can be reduced.

  In other words, the adsorption performance of the radioactive material decreases with the passage of time used for the adsorption process after the adsorbent replacement process, but the adsorbent is added in the adsorbent replacement process thereafter. The adsorption performance of the entire first adsorption processing unit is improved at the time of the adsorbent replacement process.

In addition, when it becomes impossible to bring an adsorbent into the concrete tank of the first adsorption processing section 10 from the second adsorption processing section 20, the concrete is introduced into the concrete tank, and the adsorbent and the concrete are mixed and insolubilized. In addition, the upper part of the concrete tank may be covered with concrete to form a closed space completely cut off from the outside.
Then, a new first adsorption treatment unit may be provided in the landfill site (for example, in a section adjacent to the closed first adsorption treatment unit) to continue the water treatment.
Thus, in this embodiment, water treatment can be performed basically using only the first adsorption treatment unit as a management area, and the second adsorption treatment unit is in a state where the radioactivity concentration exceeds 10,000 Bq / kg. Management can be facilitated as compared with the case of replacing the adsorbent.

In the present embodiment, organic substances, salts, radioactive substances and the like are concentrated on the concentrated water side by membrane separation.
Therefore, in this embodiment, in order to prevent salt circulation in the system due to the provision of the return means 50, the evaporation concentration process for the water after passing through the second adsorption processing unit 20 in the evaporation concentration unit 160 is performed. This is done to prevent salt circulation in the system by solidifying salt and the like.
However, if the component to be solidified contains a radioactive substance at a concentration exceeding 10,000 Bq / kg, special management may be required, so that the solid obtained by the evaporation concentration process is 10,000 Bq. / Kg or less, preferably 8,000 Bq / kg or less.
When performing such a process, the evaporated water may be discharged through the condensed water storage unit 170, the first adsorption processing unit 10, the primary treated water storage unit 30, or the like, or these It may be returned to a plurality of places including and circulated.
Moreover, a part of the water after passing through the second adsorption processing unit 20 may be circulated as it is, and the remaining part may be subjected to an evaporation concentration process.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and conventionally well-known technical matters are appropriately added to the above-described exemplary embodiments, or the essential part of the present invention is the configuration illustrated above. For those that do not, this can be deleted as appropriate.
Furthermore, it is possible to change the above-described configuration to one having the same type of function, or to change the order of each configuration in the processing flow.

For example, when there is a possibility that the reverse osmosis membrane may be deteriorated by the radioactive substance and the service life may be excessively shortened than usual, another adsorption process is performed immediately before the membrane separation unit 200 as shown in FIG. A portion 21 can be provided.
Furthermore, since the concentrated water of the second membrane separation device 150 normally contains very little radioactive material, the first adsorption treatment unit is not introduced into the second adsorption treatment unit 20 without introducing this concentrated water. Alternatively, the suction process may be performed only by the first suction processing unit 10.
Further, when the radioactive substance can be sufficiently removed by the first membrane separation device 140, the second membrane separation device 150 may not be provided.
On the other hand, in actual use, the permeated water discharged may be treated by providing a third adsorption treatment unit as a safety net in the subsequent stage of the membrane separation unit for safety.
That is, a safety net may be configured by the third adsorption processing unit on the assumption that the reverse osmosis membrane is unexpectedly damaged and the radioactive material leaks to the permeate side.
Furthermore, although it is set as the structure which performs an evaporative concentration process with respect to concentrated water, this structure is not essential. In other words, when the salt concentration in the concentrated water is not a problem, it may be returned without performing the evaporation concentration process.

  Further, although no further detailed description will be given here, it goes without saying that it is possible to make changes beyond the above examples.

4 Flat Membrane Type Module 6 Flat Membrane 7 Spacer 9 To-be-treated Water Channel 10 First Adsorption Processing Unit 20 Second Adsorption Processing Unit 30 Primary Treated Water Storage Unit 50 Returning Means 140 First Reverse Osmosis Membrane Separator 150 Second Reverse Osmosis Membrane Separation device 200 Membrane separation unit

Claims (14)

  An adsorbent capable of adsorbing a radioactive substance after membrane separation of the water to be treated containing the radioactive substance into a concentrated water with an increased concentration of the radioactive substance and a permeated water with a reduced concentration using a reverse osmosis membrane Performing an adsorption treatment for bringing the concentrated water into contact with the adsorbent to adsorb the radioactive substance, and returning at least part of the adsorption-treated water after the adsorption treatment to the step before the membrane separation. Water treatment method.   The membrane separation is performed using a plurality of reverse osmosis membrane separation devices, and a first membrane separation that separates water to be treated into concentrated water and permeated water, and permeated water obtained by the first membrane separation. The membrane separation is performed in at least two stages of the second membrane separation that separates the concentrated water and the permeated water, and the concentrated water obtained by each membrane separation is subjected to the adsorption treatment and returned. The water treatment method according to 1.   The first membrane separation is performed by a reverse osmosis membrane separation device having a planar membrane type module configured to form a turbulent flow due to the water to be treated on the surface of the reverse osmosis membrane, and the second membrane The water treatment method according to claim 2, wherein the separation is performed by a reverse osmosis membrane separation apparatus having any one of a spiral type reverse osmosis membrane module, a hollow fiber type reverse osmosis membrane module, and a pleated type reverse osmosis membrane module.   Before the membrane separation, the first adsorption treatment is performed by adsorbing radioactive material by bringing the treated water into contact with the adsorbent prepared separately from the adsorbent used for the concentrated water adsorption treatment. The water treatment according to any one of claims 1 to 3, wherein the adsorption-treated water obtained by the above-described method is subjected to membrane separation, and the adsorption treatment for the concentrated water obtained by the membrane separation is performed as a second adsorption treatment. Method.   The adsorbent replaced by performing an adsorbent replacement step of replacing the adsorbent with a new adsorbent before the radioactive concentration of the adsorbent used in the second adsorption treatment exceeds 10,000 Bq / kg. The water treatment method according to claim 4, wherein the water is used for the first adsorption treatment.   The water treatment method according to claim 5, wherein the adsorbent replacement step is performed at a radioactivity concentration of the adsorbent of 8,000 Bq / kg or less.   7. The treated water to be treated contains leachate that is leached from a landfill site where a radioactive substance or a waste contaminated with a radioactive substance is buried. Water treatment method.   A membrane separation unit comprising a reverse osmosis membrane separation device for membrane-separating treated water containing a radioactive substance into concentrated water with an increased concentration of the radioactive substance and permeated water with a reduced concentration; and the membrane separation An adsorbing treatment unit in which the concentrated water obtained by the reverse osmosis membrane separation device and the adsorbent capable of adsorbing the radioactive substance are brought into contact with each other and the radioactive substance contained in the concentrated water is adsorbed to the adsorbent A water treatment facility, further comprising a return means for returning at least a part of the adsorption treated water adsorbed by the adsorption treatment unit before the membrane separation unit.   The membrane separation unit is obtained by a first reverse osmosis membrane separation device that separates water to be treated introduced into the membrane separation unit into concentrated water and permeated water, and the first reverse osmosis membrane separation device. At least two reverse osmosis membrane separation devices, a second reverse osmosis membrane separation device for separating the permeated water into concentrated water and permeated water, and the concentrated water obtained by each reverse osmosis membrane separation device The water treatment facility according to claim 8, wherein the adsorption treatment unit is configured to cause adsorption treatment.   The first reverse osmosis membrane separation device is a reverse osmosis membrane separation device having a planar membrane module configured to form a turbulent flow due to the treated water on the surface of the reverse osmosis membrane, and the second The water treatment according to claim 9, wherein the reverse osmosis membrane separation device is a reverse osmosis membrane separation device having any one of a spiral type reverse osmosis membrane module, a hollow fiber type reverse osmosis membrane module, and a pleated type reverse osmosis membrane module. Facility.   A first adsorption treatment unit that contacts the adsorbent to adsorb the radioactive substance contained in the water to be treated is further provided on the front side of the membrane separation unit, and the concentration is performed on the rear side of the membrane separation unit. The water treatment facility according to any one of claims 8 to 10, wherein the adsorption treatment unit that performs adsorption treatment on water is provided as a second adsorption treatment unit.   Before the radioactive concentration of the adsorbent in the second adsorption processing unit exceeds 10,000 Bq / kg, the adsorbent is replaced with a new adsorbent, and the replaced adsorbent is used as the first adsorbent. The water treatment facility according to claim 11, wherein the water treatment facility is used for the adsorption treatment in the first adsorption treatment unit in addition to the adsorbent in the adsorption treatment unit.   The water treatment facility according to claim 12, wherein the adsorbent of the second adsorption treatment unit is replaced with a new adsorbent at a radioactivity concentration of 8,000 Bq / kg or less.   The water according to any one of claims 8 to 13, which is used for treatment of the treated water including leachate leached from a landfill site where a radioactive substance or a waste contaminated with a radioactive substance is buried. Processing equipment.

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