JP5732511B2 - Water treatment method and water treatment equipment - Google Patents

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 radioactive substances such as leachate, a method using an adsorbent is known. Water containing radioactive substances is treated water and adsorbs radioactive substances. Conventionally known is a water treatment method in which the water to be treated is brought into contact with a possible adsorbent to reduce the concentration of radioactive substances in the water to be treated.

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.
In addition to the adsorbent packed tower for carrying out the adsorbing treatment of the water to be treated, the following Patent Document 1 performs an adsorbing process on the regenerated liquid generated when the adsorbent in the adsorbent packed tower is regenerated. A water treatment facility with an adsorbent packed tower is described.
In addition, as described in Patent Document 1 below, in this type of water treatment method, it has been desired to reduce the amount of adsorbent used.

JP 2000-206291 A

  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, in the water treatment facility as described above, it is preferable to dispose the used adsorbent in a state having a radioactivity concentration or less as described above in that the facility can be easily managed.
On the other hand, if the adsorbent is disposed of by disposal in a state where the radioactive concentration is lower than this, the adsorbent that still has sufficient adsorption performance of radioactive substances will be consumed in large quantities. There is a problem that it becomes difficult to satisfy the above-mentioned demand.

  This invention makes it a subject to solve the above problems, and makes it a subject to control mass consumption of an adsorbent easily 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 problem is a method for reducing the concentration of radioactive material in the water to be treated by bringing the water to be treated into contact with the adsorbent capable of adsorbing the radioactive material. A processing method,
After performing a first adsorption process for reducing the concentration of radioactive substances by bringing the water to be treated into contact with the adsorbent in an adsorption treatment unit having an adsorbent layer on which an adsorbent is deposited , A second adsorbing process for further reducing the concentration by bringing the water to be treated that has been adsorbed into contact with another adsorbent is performed, and the radioactive concentration of the adsorbent used in the second adsorbing process is 10, An adsorbent replacement step is performed in which the adsorbent is replaced with a new adsorbent before exceeding 000 Bq / kg, and the replaced adsorbent is added to the adsorbent in the adsorbent layer and thereafter the adsorbent replacement step In the first adsorption process.

Further, the present invention relating to a water treatment facility for solving the above-described problems is that an adsorbent capable of adsorbing a radioactive substance is accommodated, water to be treated containing the radioactive substance is introduced, and the radioactive substance is applied to the adsorbent. A water treatment facility provided with at least two adsorption treatment units that are adsorbed to reduce the concentration of radioactive substances in the water to be treated,
The first adsorption processing unit of the adsorption processing unit includes an adsorbent layer formed by the deposited adsorbent, and the first adsorption processing unit performs an adsorption process for adsorbing a radioactive substance on the adsorbent. The used water to be treated is introduced into the second adsorption treatment unit to be used for further adsorption treatment, and the radioactive concentration of the adsorbent in the second adsorption treatment unit is 10,000 Bq / kg. The adsorbent is replaced with a new adsorbent before use, and the replaced adsorbent is added to the adsorbent of the first adsorption processing section and adsorbed by the first adsorption processing section. In order to be used for processing, the first adsorption processing unit is further provided with a space for accommodating the adsorbent material above the adsorbent layer .

According to the present invention, the replacement work for replacing the adsorbent used in the second adsorption process on the post-treatment side is performed before the radioactive concentration of the adsorbent exceeds 10,000 Bq / kg. It can be implemented without strict management as stipulated in the ionization law.
Further, according to the present invention, since the replaced adsorbent can be used for the first adsorbing treatment, the adsorbing performance of the adsorbent can be fully utilized.
Accordingly, it is possible to suppress the mass consumption of the adsorbent.
In addition, since the amount of the adsorbent used for the first adsorption process can be increased by using the replaced adsorbent in addition to the adsorbent of the first adsorption process, The content of radioactive material in the water to be treated flowing down to the second adsorption process after finishing the adsorption process can be reduced as compared with that before.
Therefore, it is possible to extend the period until the adsorbent used for the second adsorption treatment reaches the radioactivity concentration that requires replacement, and this can also suppress the mass consumption of the adsorbent.

It is a block diagram showing a schematic structure of 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. 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 other embodiments 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, for the first embodiment of the water treatment method of the present invention, the leachate from the landfill disposal site (final disposal site) where the radioactive material has been buried is treated water as an example, This will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing a schematic configuration of a water treatment facility used in the first embodiment. Reference numeral 1 in the figure represents a landfill disposal site where there is a risk of leaching water to be treated, and reference numeral 2 represents the landfill. The receiving tank for storing the leachate discharged | emitted from the disposal site 1 is represented.
Reference numerals 10 and 20 are adsorption treatment units each containing an adsorbent capable of adsorbing a radioactive substance, and 10 is a first adsorption treatment unit (10) for adsorbing treated water on the upstream side of the water treatment. (Hereinafter also referred to as “first adsorption treatment unit”), and 20 is a second adsorption process performed on the water to be treated that has been subjected to the first adsorption treatment by the first adsorption treatment unit on the downstream side of the water treatment. 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 are provided outside the management area. It has been.

In the water treatment facility of the present embodiment, as shown in FIG. 1, in order from the first adsorption treatment unit 10, the primary treated water storage unit 30, the pH adjustment unit 40, the nitrification unit 50, the denitrification unit 60, the coagulation sedimentation. Part 70, neutralizing part 80, sand filtering part 90, and chelate treatment part 100, and the second adsorption treatment part 20 is provided downstream of the chelate treatment part 100.
In addition, the water treatment facility of this embodiment includes an ultrafiltration unit 110 and a disinfection unit 120 in this order on the downstream side of the second adsorption treatment unit 20, and the water treatment facility of this embodiment Is configured so that water that has been treated in the disinfection unit 120 can be discharged out of the system as treated water.

The second adsorption processing unit 20 includes an adsorption tower having a container for containing an adsorbent and an adsorbent accommodated in the container, and the adsorption tower is introduced from one of the containers. The treated water is moved to the other side of the container while being in contact with the adsorbent inside the container, and is discharged.
Further, the adsorption tower is configured so that the radioactive substance contained in the water to be treated is adsorbed by the adsorbent due to the contact between the water to be treated and the adsorbent, thereby reducing the concentration of the radioactive substance in the water to be treated. It is configured.

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.

In contrast to the second adsorption processing unit 20 configured by such an adsorption tower, the first adsorption processing unit 10 is several times larger than the container containing the adsorbent in the adsorption tower of the second adsorption processing unit 20. It is constituted by a concrete tank (hereinafter also referred to as “concrete tank”) having a volume of several tens of times or more.
In addition, the concrete tank of the 1st adsorption processing part 10 is provided in the form which forms a surrounding wall and a bottom wall by the concrete which has fixed thickness in a part of said landfill disposal site, and the inside and outside are completely isolated. It is provided as such.
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.
In addition, as an adsorbent for forming the adsorbent layer, a material similar to that described with respect to the second adsorption processing unit 20 can be employed.
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 disposal site due to rain or the like as treated water, and passes the treated water via the receiving tank 2 to the concrete tank. The treated water that has been introduced from the top of the concrete tank and passed through the adsorbent layer can be pumped from the bottom of the concrete tank to the ground through the suction pipe and can flow down to the primary treated water reservoir 30 as primary treated water. ing.
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 | suction process part 10 has sufficient storage space above the said adsorbent layer, and is using the adsorbent of said 2nd adsorption | suction process part 20 so that it may mention later. When it is replaced with a new one, the adsorbent that has been used in the second adsorbing treatment unit 20 can be newly deposited on the adsorbent layer and used for the adsorbing treatment in the concrete tank. Yes.

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 includes an adjustment tank for stabilizing the flow rate and water quality when the adsorption treated water adsorbed by the first adsorption treatment unit 10 is subjected to the subsequent treatment. .
The pH adjuster 40 also includes a pH adjusting tank for temporarily storing the water to be treated introduced from the primary treated water storage part 30, and a biological nitrification dewatering of the treated water in the pH adjusting tank. A pH adjusting mechanism for adjusting to a pH suitable for performing the nitrogen treatment.
The nitrification unit 50 biologically oxidizes organic nitrogen, ammonia nitrogen, or the like contained in the water to be treated introduced from the pH adjustment unit 40 to nitrate nitrogen or nitrite nitrogen. The denitrification section 60 is provided with a denitrification section 60 for reducing nitrate nitrogen and nitrite nitrogen in the water to be treated introduced from the nitrification section 50 and converting it into nitrogen gas. It has a nitrogen tank.

The coagulation sedimentation unit 70 includes a sedimentation tank for coagulating and sedimenting suspended matter such as activated sludge used for biological treatment in the denitrification unit 60.
The neutralization unit 80 includes a treated water tank for neutralizing the treated water introduced from the coagulation sedimentation unit 70, and the sand filtering unit 90 is treated with the treated water introduced from the neutralization unit 80. It is provided to further remove suspended matter in the treated water.
The chelate treatment unit 100 is a front side of the second adsorption treatment unit 20 in order to capture a heavy metal ion or the like in the water to be treated introduced into the second adsorption treatment unit 20 with a chelating agent. Is provided.

The ultrafiltration unit 110 provided on the downstream side of the second adsorption processing unit 20 captures the adsorbent particles from the second adsorption processing unit 20 by an ultrafiltration membrane even if the adsorbent particles leak, It is provided to more reliably suppress the radioactive substance concentration of water below the reference value.
The water treatment facility according to the present embodiment disinfects the permeated water that has passed through the ultrafiltration membrane of the ultrafiltration unit 110 with the disinfection unit 120 and discharges the disinfected water out of the system as treated water. Configured to get.

Using such a water treatment facility, by treating the leachate as treated water, the first adsorption treatment is performed while the treated water flows down from the first adsorption treatment unit 10 to the disinfection unit 120 in order. The first adsorption treatment for reducing the concentration of the radioactive substance by bringing it into contact with the adsorbent forming the adsorbent layer in the unit 10 can be performed. In the adsorption tower of the second adsorption processing unit 20, a second adsorption process can be performed in which the concentration is further lowered by bringing it into contact with another adsorbent different from the first adsorption processing unit 10.
Moreover, in the present embodiment, heavy metal or organic nitrogen other than the radioactive substance contained in the leachate while the water to be treated flows down from the first adsorption treatment unit 10 to the disinfection unit 120 in order. Can be removed.

In such a water treatment method, the adsorbent of the second adsorption treatment unit 20 is replaced with a new adsorbent with a radioactivity concentration of 10,000 Bq / kg or less, preferably 8,000 Bq / kg or less. In order to simplify the water treatment method, it is important to perform the adsorbent replacement step.
That is, by handling the adsorbent of the second adsorption processing unit 20 in the state showing the radioactive concentration as described above, it is possible to reduce the necessity of performing strict management for the handling of the adsorbent.
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 density | concentration the adsorbent of the 2nd adsorption process part 20 becomes, for example, the quality of the adsorption process water currently stored in the adjustment tank in the primary treated water storage part 30 is regularly It is possible to predict the amount of water flowing down from the adjustment tank while monitoring the content of the radioactive substance by analyzing it.
That is, since the water passing through the second adsorption treatment unit 20 contains almost no radioactive substance, almost the entire amount of radioactive substance contained in the water to be treated flowing down from the adjustment tank is the second adsorption treatment. It will be adsorbed by the adsorbent of the part.
Therefore, by dividing the total amount of this radioactive substance by the total mass of the adsorbent accommodated in the adsorption tower, the radioactivity concentration of the adsorbent can be obtained, and the timing for carrying out the adsorbent replacement process can be grasped. Can do.

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 important in reducing the consumption of materials.
That is, the adsorbent used in the second adsorption treatment is 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. Since the radioactivity concentration still has sufficient adsorption performance, it is an important factor in the water treatment method of this embodiment to effectively utilize this in the first adsorption treatment.

In this embodiment, the storage space for the adsorbent in the first adsorption processing unit 10 is much larger than the storage space for the adsorbent in the second adsorption processing unit 20. Even if the adsorbent replacement process is performed once, the old adsorbent that has been stored in the adsorption tower before the adsorbent replacement process can be stored in the concrete tank of the first adsorption processing unit 10.
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) It is possible to reduce the concentration of radioactive material to be treated that flows down toward the primary treated water storage unit 30 after the adsorbent is accommodated in the first adsorption processing unit.

  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.

Next, a second embodiment according to the water treatment method of the present invention will be described with reference to FIG.
In addition, about the structure etc. which are common in 1st embodiment, description is omitted here.
(Second embodiment)
In the second embodiment, a membrane separation unit 200 including a reverse osmosis membrane separation device between the first adsorption processing unit 10 and the second adsorption processing unit 20, and the upstream side of the membrane separation unit 200 The water treatment equipment used is different from that of the first embodiment in that the safety filter section 130 provided in the first embodiment is provided.
Further, in the second embodiment, the concentrated salt 160 or the radioactive substance contained in the water is concentrated by evaporating the water, and the condensed water obtained by condensing the water evaporated in the evaporation and concentrating unit 160 is used. The water treatment facility used is different from that of the first embodiment in that a condensate storage unit 170 is further provided.
In the present embodiment, the adsorption-treated water that has been subjected to the adsorption treatment in the first adsorption treatment unit 10 is reversed to the concentrated water in which the concentration of the radioactive substance is improved and the permeated water in which the concentration is reduced. The membrane separation unit 200 is configured so that a membrane separation process for membrane separation using an osmosis membrane can be performed by a reverse osmosis membrane separation apparatus provided in two stages.
That is, in the present embodiment, the first membrane separation device 140 for separating the adsorption treated water subjected to the adsorption treatment in the first adsorption treatment unit 10 into concentrated water and permeated water, and the first membrane separation device. A membrane separation unit 200 including two reverse osmosis membrane separation devices of a second membrane separation device 150 for further membrane separation of 140 permeated water into concentrated water and permeated water using a reverse osmosis membrane is provided. .

In this second embodiment, the water treatment facility is configured so that the permeated water of the second membrane separation device 150 can be discharged out of the system as treated water. The water treatment facility is configured such that the water is subjected to an adsorption treatment in the second adsorption treatment unit 20 together with the concentrated water of the first membrane separation device 140.
In the water treatment facility of the present embodiment, the adsorption-treated water that has been subjected to the adsorption treatment in the second adsorption treatment 20 is used as the condensed water after the evaporating and concentrating unit 160 removes salts and radioactive substances. It is configured to be discharged out of the system or returned to the first adsorption processing unit 10 or the upstream side again.

  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 planar membrane type module, a plurality of spacers 7 are arranged as illustrated in FIG. 3, 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. 3 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. 3, 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 risk of deposits forming on the membrane surface, and the membrane area relative 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 this embodiment, salts and radioactive substances are concentrated on the concentrated water side by membrane separation.
Therefore, in the present embodiment, in order to prevent salt circulation in the system, the evaporation concentration unit 160 performs evaporation concentration processing on water after passing through the second adsorption processing unit 20, and solidifies the salt content. In order to prevent salt circulation in the system.
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, more 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.

  In the first embodiment, since organic nitrogen or the like contained in the leachate has been biologically treated, it needs to be treated when excess sludge or the like is generated. By providing the osmotic membrane separation devices 140 and 150 to discharge only the permeated water and condensed water in which the concentration of radioactive material has been sufficiently reduced, extra processing objects such as excess sludge are generated. Can be suppressed.

(Other embodiments)
The present invention is not limited to the first embodiment and the second embodiment described above.
Conventionally known technical matters can be appropriately added to these embodiments, or, among the configurations exemplified in these embodiments, those not essential parts of the present invention can be appropriately deleted. .
Furthermore, it is possible to change the configurations of the first embodiment and the second embodiment to those having the same type of function, or to change the order of the components in the processing flow.
For example, in the first embodiment, the chelate processing unit is arranged in the front stage of the second adsorption processing unit, but the chelating agent is likely to adsorb and contaminate the radioactive material, and the chelating agent is contaminated. May not be preferable, the chelate treatment unit may be installed at a stage subsequent to the second adsorption treatment unit.

  Further, for example, in the second embodiment, the concentrated water of the second membrane separation device 150 is introduced into the second adsorption processing unit 20 together with the concentrated water of the first membrane separation device 140. Since 150 concentrated water usually contains very little radioactive substance, the concentrated water is returned to the adjustment tank of the primary treated water storage unit 30 without being introduced into the second adsorption processing unit 20. May be.

Furthermore, in the second embodiment, when there is a possibility that the reverse osmosis membrane is deteriorated by the radioactive substance and the service life is excessively shortened than usual, the second adsorption processing unit 20 is exemplified as shown in FIG. May be provided on the upstream side of the membrane separation unit 200.
In the second embodiment, when the radioactive material 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, when using a reverse osmosis membrane like embodiment of FIG.2 and FIG.4, 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.

In addition, instead of storing the water to be treated flowing down from the first adsorption treatment unit 10 in the adjustment tank, an adjustment tank is provided on the upstream side of the first adsorption treatment unit 10 and the leachate is introduced into the adjustment tank in advance. You may make it adjust the quantity and water quality of the to-be-processed water flowed down to the 1st adsorption process part 10. FIG.
Moreover, in this embodiment, although a process target object is made into the leaching water from the soil by which the radioactive substance was embedded, this invention is useful also for water treatment other than such to-be-processed water.
In addition, in the landfill site, as described above, there is an advantage that one corner of the site is managed as a management area and the first adsorption processing unit is installed in the area so that the management can be performed safely and easily.

  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 flow path 10 First adsorption treatment unit 20 Second adsorption treatment unit 30 Primary treated water storage unit 40 pH adjustment unit 50 Nitrification unit 60 Denitrification unit 70 Coagulation sedimentation unit 80 Japanese part 90 Sand filtration part 100 Chelate treatment part 110 Ultrafiltration part 120 Disinfection part 140 First membrane separator 150 Second membrane separator 200 Membrane separator

Claims (6)

A water treatment method for reducing the concentration of the radioactive substance in the water to be treated by bringing the treated water containing the radioactive substance into contact with an adsorbent capable of adsorbing the radioactive substance,
After performing a first adsorption process for reducing the concentration of radioactive substances by bringing the water to be treated into contact with the adsorbent in an adsorption treatment unit having an adsorbent layer on which an adsorbent is deposited , A second adsorbing process for further reducing the concentration by bringing the water to be treated that has been adsorbed into contact with another adsorbent is performed, and the radioactive concentration of the adsorbent used in the second adsorbing process is 10, An adsorbent replacement step is performed in which the adsorbent is replaced with a new adsorbent before exceeding 000 Bq / kg, and after the adsorbent replacement step, the replaced adsorbent is added to the adsorbent in the adsorbent layer. The water treatment method is used for the first adsorption treatment.   The water treatment method according to claim 1, wherein the adsorbent replacement step is performed at a radioactivity concentration of the adsorbent of 8,000 Bq / kg or less.   The water treatment method according to claim 1 or 2, wherein the treated water to be treated contains leachate leached from a landfill site where a radioactive substance or a waste contaminated with the radioactive substance is buried. An adsorption process in which an adsorbent capable of adsorbing a radioactive substance is accommodated, treated water containing the radioactive substance is introduced, and the radioactive substance is adsorbed on the adsorbent to reduce the concentration of the radioactive substance in the treated water A water treatment facility provided with at least two parts,
The first adsorption processing unit of the adsorption processing unit includes an adsorbent layer formed by the deposited adsorbent, and the first adsorption processing unit performs an adsorption process for adsorbing a radioactive substance on the adsorbent. The used water to be treated is introduced into the second adsorption treatment unit to be used for further adsorption treatment, and the radioactive concentration of the adsorbent in the second adsorption treatment unit is 10,000 Bq / kg. The adsorbent is replaced with a new adsorbent before use, and the replaced adsorbent is added to the adsorbent of the first adsorption processing section and adsorbed by the first adsorption processing section. The water treatment facility is characterized in that the first adsorption processing unit is further provided with a space for accommodating an adsorbent so as to be used for the treatment above the adsorbent layer .   The water treatment facility according to claim 4, 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 treatment facility according to claim 4 or 5, wherein the water treatment facility is used for treating the water to be treated containing leachate leached from a landfill site where a radioactive substance or a waste contaminated with the radioactive substance is buried.

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