Strontium removal method and removal device using spore-forming bacteria

Abstract

To develop a contaminated water processing device that can shorten the work time in a radiation controlled area and minimize the risk of exposure due to the work.SOLUTION: A method for removing strontium is developed by inducing spore formation outside a radiation controlled area, producing and preserving bacteria in a spore-forming process, carrying the spore-forming bacteria into the radiation controlled area, then introducing the spore-forming bacteria into a tank in which contaminated water is adjusted to an environment where spore-forming bacteria can survive, and forming spores. Since the work in the radiation controlled area is shorter than before, the risk of exposure due to the work can be minimized, and the state of the spore-forming bacteria can be easily controlled as well, and thereby bacteria having spore-forming ability can be stably supplied, and high contamination processing efficiency can be maintained.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a safe method and treatment device for treating contaminated water containing radioactive materials, particularly strontium, using spore-forming bacteria. [Background technology]

[0002] More than 12 years have passed since the Great East Japan Earthquake, but efforts to decommission the Fukushima Daiichi Nuclear Power Plant are still ongoing. Contaminated water has been an issue since the beginning of the accident, and although the release of treated water into the ocean using the Advanced Liquid Processing System (ALPS) began in 2023, the treatment of the contaminated water is not yet complete. According to Tokyo Electric Power Company, the inflow of groundwater and rainwater into the reactor buildings has been reduced to approximately 540m from the level before countermeasures were implemented, due to the pumping of groundwater and the construction of frozen soil walls. 3 / day (May 2014), but it has decreased by approximately 140m 3 / day (average for 2020), the amount of contaminated water being generated is still a major issue.

[0003] Not only is contaminated water generated in large quantities, but it also contains 63 types of radioactive material, including strontium and cesium, making treatment difficult. Contaminated water treatment methods can be broadly divided into two categories: using chemicals or adsorbents, and using microorganisms. The contaminated water treatment currently being carried out at the Fukushima Daiichi Nuclear Power Plant uses chemicals and adsorbents, which removes 62 types of radioactive material except for tritium. The main problems with this method include a low removal rate, poor adsorption performance, the existence of nuclides that are difficult to remove, the large number of column stages, the short service life of the absorbent material, the high cost of the absorbent material and its resulting high operating costs, and the large amount of absorbent material adsorbed with highly radioactive materials that is generated as waste, which requires treatment and storage.

[0004] In addition to methods using chemicals or adsorbents, methods for treating contaminated water using microorganisms to remove water-soluble metal ions from contaminated water or wastewater are known (Non-Patent Document 1, Patent Documents 1-5). Non-Patent Document 1 discloses a method for removing strontium contaminated from drinking water from industrial wastewater using thermophilic bacteria (Bacillus genus). Patent Document 1 discloses an apparatus and method for treating radioactive wastewater containing organic matter and radioactive materials generated at nuclear facilities using microorganisms. Patent Document 2 discloses a method for purifying contaminated water by absorbing and adsorbing radioactive materials, mainly cesium, into a biofilm formed by microorganisms. Patent Document 3 discloses a method for removing cesium and strontium from wastewater by adsorbing cesium with denitrifying bacteria and cesium-accumulating bacteria (Rhodococcus genus) and adsorbing strontium to the mycelium of microorganisms belonging to the Hebeloma genus. The present inventor has also disclosed a method for treating contaminated water containing strontium using spore-forming bacteria (Patent Documents 4 and 5). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-064732 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-104765 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-271306 [Patent Document 4] Patent No. 6280661 [Patent Document 5] Japanese Patent Application Publication No. 2019-128187 [Non-patent literature]

[0006] [Non-Patent Document 1] Chaalal, O., et al., 2015, J. Indust. Eng. Chem. Vol.21, p.822-827. [Non-patent document 2] Foerster, HF & Foster, JW, 1966, J. Bacteriol. Vol.91, p.1333-1345. Summary of the Invention [Problem to be solved by the invention]

[0007] The method described in Non-Patent Document 1 removes strontium to a level suitable for drinking water. However, the expected amount and strontium concentration of contaminated water differ from those of contaminated water generated by nuclear power plant accidents, and the method contains various contaminants, making it unlikely to be directly applicable. Furthermore, the invention described in Patent Document 1 is a method for treating washing wastewater generated when washing clothes and other items contaminated with radioactive materials at nuclear facilities. However, the expected amount and concentration of contaminated water are low, making it impossible to directly apply to contaminated water generated by nuclear power plant accidents. The invention described in Patent Document 2 involves adsorbing and removing cesium to a biofilm formed by microorganisms contained in sludge, while the invention described in Patent Document 3 involves adsorbing and removing cesium using activated sludge containing denitrifying bacteria. Treatment capacity is thought to vary depending on the microorganisms that make up the biofilm and activated sludge, but there is no mechanism for controlling the amount and type of microorganisms contained in activated sludge, making it difficult to adjust treatment capacity. The invention described in Patent Document 4 removes strontium using spore-forming bacteria, and Patent Document 5 describes a method for removing strontium and cesium using Bacillus and Rhodococcus bacteria.

[0008] However, the methods using microorganisms described in Patent Documents 2 to 4 require work in a radiation-controlled area for a certain period of time to confirm the culture conditions of the microorganisms in the treatment device, etc. Because work in a controlled area with high radiation levels carries the risk of radiation exposure, it is desirable to keep the work time as short as possible. The present invention aims to provide an apparatus and method that minimizes the time spent in a high-radiation area, while taking safety into consideration, and that can quickly and efficiently treat large amounts of contaminated water and generate little industrial waste after treatment. In particular, the present invention aims to provide a method for efficiently and inexpensively reducing the concentrations of strontium and cesium, which are contained in large amounts in water to be treated and have a significant impact on living organisms. [Means for solving the problem]

[0009] The present invention relates to a method for safely treating contaminated water containing metal ions, particularly water containing radioactive strontium, and a treatment device used therefor. (1) A method for treating contaminated water contaminated with radiation, comprising an adjustment step of adjusting the contaminated water to an environment in which spore-forming bacteria can survive, an absorption step of introducing bacteria in the spore-forming process, which have been induced to form spores in advance, into the adjusted contaminated water to absorb strontium, and a solid-liquid separation step of separating the water into strontium-purified water and a solid containing strontium. Bacteria in the spore-forming process, which have been induced to form spores in advance, are added to contaminated water and allowed to absorb strontium, thereby enabling stable and efficient absorption of strontium.

[0010] (2) The contaminated water treatment method described in (1) is characterized in that the bacteria in the spore-forming process are cultured outside a radiation-controlled area to induce spore-forming ability, and then washed, concentrated, and stored in a spore-forming state. Since the process of inducing the spore-forming ability of spore-forming bacteria is carried out outside the radiation-controlled area, it is possible to reduce the time spent working in the controlled area and minimize the risk of exposure.

[0011] (3) A method for treating contaminated water according to (2), characterized in that the bacteria in the spore-forming process are stored at a temperature of 4°C or below. It was found that bacteria in the spore-forming process can be stored for long periods of time while maintaining their spore-forming ability if stored at temperatures below 4°C.

[0012] (4) A water treatment device using spore-forming bacteria, characterized by comprising a contaminated water adjustment tank that adjusts contaminated water to an environment in which spore-forming bacteria can survive, an absorption tank into which bacteria in the spore-forming process are introduced to absorb strontium, and a solid-liquid separation tank that separates Sr-purified water from a solid in which Sr is concentrated. Conventionally, a culture tank was required to grow spore-forming bacteria, but in this embodiment, the culture tank is installed outside the radiation controlled area, resulting in a simpler configuration and reducing costs such as construction costs.

[0013] (5) The water treatment device according to (4), wherein the solid-liquid separation tank is provided with a separation membrane for performing solid-liquid separation. By performing solid-liquid separation using a separation membrane, water treatment can be carried out more efficiently. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a flow diagram showing a water treatment method according to an embodiment of the present invention. [Figure 2] Figure showing the strontium (Sr) absorption capacity of spore-forming bacteria. (A) shows the Sr concentration in the supernatant, and (B) shows the percentage of Sr absorbed by the bacterial cells. [Figure 3] FIG. 1 shows the rate of Sr absorption into bacterial cells as a function of culture time. [Figure 4] This figure shows the results of culturing spore-forming bacteria stored for different periods and temperatures in a strontium-containing medium and confirming spore formation under a microscope. [Figure 5] 1 is a diagram schematically illustrating a water treatment device according to an embodiment. [Figure 6] FIG. 1 is a diagram schematically illustrating a conventional water treatment device. DETAILED DESCRIPTION OF THE INVENTION

[0015] The contaminated water treatment method according to this embodiment uses spore-forming bacteria that incorporate water-soluble metals into spores, forms spores, collects them, and performs water treatment. Spores consist of a spore coat, cortex, and core. The core contains polymers such as DNA, RNA, and proteins, and contains large amounts of dipicolinic acid and calcium ions as low-molecular-weight compounds. Dipicolinic acid accounts for 5 to 15% of the dry weight of the spore. Calcium ions, which are cations, are thought to exist as chelated to dipicolinic acid containing a carboxylic acid residue. During spore formation, large amounts of dipicolinic acid are synthesized within the cells, and large amounts of calcium ions are absorbed from outside the cells. Strontium belongs to the same group as calcium on the periodic table and exhibits similar properties to calcium. Therefore, it is known that strontium ions are absorbed during core formation (Non-Patent Document 2). The mechanism by which strontium is absorbed into spore-forming cells is by incorporation into the core during spore formation. By utilizing this property, strontium can be concentrated and removed from the treated water by causing spore-forming bacteria to form spores and collecting the spores together with the sludge. Spore-forming bacteria grow by repeated cell division as vegetative cells under conditions suitable for growth. However, when placed under conditions unsuitable for growth, they have the property of forming spores within the cells and entering a dormant phase. Spores have a strong structure and are extremely resistant to heat, physical pressure, chemicals, etc. As a result, once strontium is taken up, it can be retained within the spores. Furthermore, in the spore-forming tank, not only spore-forming bacteria but also other microorganisms grow and form biofilms, making it possible to remove a certain amount of other radioactive materials by adsorption to the biofilm.

[0016] The conventional water treatment method involves installing a culture tank in a radiation controlled area to culture spore-forming bacteria in the vegetative cell state, mixing the cultured vegetative cells with contaminated water in a mixing tank, creating conditions for spore formation in a spore formation tank, causing the strontium to be absorbed into the spores, and separating and treating treated water from which strontium has been removed and sludge containing large amounts of strontium-absorbed spores (Figure 6, Patent Document 4).

[0017] Although this method allows for automatic monitoring of the temperature, pH, and other parameters of each tank, certain processes, such as inoculating the culture tank and checking the status of vegetative cells and spore formation, require sampling and monitoring the culture conditions, which requires working within a radiation-controlled area for a certain period of time. This increased workload increases the worker's exposure time and radiation dose. Furthermore, the treated water from which strontium has been removed after solid-liquid separation still contains residual medium components and their metabolites. Since treated water typically contains other radionuclides, it is sent to other nuclide purification processes after strontium removal. In this case, substances derived from the medium components may adversely affect the subsequent processes. Furthermore, if the strontium removal process is the final decontamination process, it is necessary to ensure that substances derived from the medium components do not exceed environmental standard concentrations.

[0018] Although radiation protection clothing and the like can reduce the effects of radiation exposure on the human body, it is desirable to limit work in radiation-controlled areas as short as possible, considering the effects on the human body. The present inventor developed a method for preserving spore-forming bacteria while maintaining their spore-forming ability by culturing spore-forming bacteria, inducing spore formation, stopping the culture during spore formation, and storing them at low temperatures, thereby completing the present invention. This method enables long-term storage of spore-forming bacteria outside of radiation-controlled areas while maintaining their spore-forming ability. Furthermore, spore-forming bacteria can be transported to a radiation-controlled area and directly introduced into a water treatment device to form spores and remove strontium. As a result, work in radiation-controlled areas can be completed in an extremely short time, minimizing the risk of radiation exposure. Furthermore, preserving bacteria in a spore-forming state allows spore formation to be performed using bacteria with a consistent ability, enabling stable processing.

[0019] The present invention will be described below with reference to data. The method described below is one embodiment, and other methods can also be applied to the culture method and spore formation method. Figure 1 shows the water treatment method of the present invention. Outside of a radiation-controlled area, spore-forming bacteria are pre-cultured and then cultured in a spore-forming medium. The bacteria are washed and concentrated during the spore formation process, and stored in a spore-forming state. In addition to the Bacillus thuringiensis and B. weihenstehanensis used here, any bacteria, such as B. megaterium, B. mycoides, or B. pseudomycoides, can be used as long as conditions for good spore formation can be established. In the following experiments, B. thuringiensis NBRC101235, B. thuringiensis NBRC110358, and B. weihenstehanensis NBRC101238 obtained from the NITE Biotechnology Center (NBRC) were used (hereinafter, each bacterium will be referred to by its NBRC number, such as #101235).

[0020] [Example 1] Setting the main culture time to obtain a main culture solution with high Sr absorption capacity For the preculture of each strain, 50 mL of trypto-soya broth medium (Nissui Pharmaceutical) was placed in a 300 mL baffled Erlenmeyer flask. A colony from trypto-soya agar was inoculated into the flask and cultured at 30°C and 110 rpm for 18 hours with rotary shaking. The main culture to induce strontium (Sr) absorption and the Sr absorption test were performed for each of the three strains as follows. 300 mL of Sr absorption expression medium (composition shown in Table 1) was placed in a 1000 mL Erlenmeyer flask, and 1 / 100 of the preculture solution was inoculated. The culture was cultured at 30°C and 110 rpm with rotary shaking. The bacterial solution was sampled at predetermined intervals, and the turbidity was measured. Before and after the turbidity plateaued (after 15, 18, 21, and 24 hours of culture), Sr absorption was measured using the following method. 30 mL of the main culture was sampled and centrifuged at 1500 rpm for 10 minutes. The resulting precipitate was suspended in 10 mL of purified water and centrifuged again under the same conditions to obtain bacterial cells with induced Sr absorption capacity as a precipitate (operations corresponding to washing and concentration in Figure 1). Bacteria collected before and after the turbidity plateau are thought to be in the process of vegetative cells ceasing proliferation and forming spores. Therefore, they are thought to have a high Sr absorption capacity. Bacteria induced to form spores are hereafter referred to as Sr absorption capacity-induced bacteria. Sr absorption capacity and Sr absorption conditions were examined.

[0021] [Table 1] NaH2PO4 and glucose were each prepared as 100-fold concentrated solutions and sterilized in an autoclave at 121°C for 20 minutes. After cooling, the required amount was added to the sterilized medium containing the remaining ingredients to create a medium for expressing Sr absorption ability.

[0022] [Example 2] Study on induction of Sr absorption ability (1) To measure the Sr uptake by the collected bacteria, 30 mL of the main culture solution was collected 15, 18, 21, and 24 hours after the start of the main culture, and the Sr uptake capacity-inducing bacteria were prepared from these. Each bacterial cell was suspended in 30 mL of an aqueous Sr solution containing 20 mg / L Sr. The suspension was transferred to a 300 mL baffled Erlenmeyer flask and cultured at 30°C and 110 rpm for a predetermined period (24 hours or more). The Sr concentration in the supernatant obtained after centrifugation was measured by inductively coupled plasma mass spectrometry (ICP-MS), and the bacterial uptake capacity was measured (Fig. 2A).

[0023] As shown in Figure 2(B), #110358 and #101238 absorbed approximately 60% of the Sr content 15 and 18 hours after the start of incubation in the Sr solution. These strains appear to absorb Sr relatively quickly under these conditions and then release Sr into the supernatant after a certain period of time. On the other hand, #101235 took longer to absorb Sr than #110358 and #101238, at 21 to 24 hours. However, under these conditions, #101235 maintained its Sr content without releasing it after a certain period of time. Therefore, #101235 was used for further analysis.

[0024] [Example 3] Examination of Sr absorption capacity When the Sr uptake-inducing bacteria were cultured in a Sr-containing solution, the time required for Sr uptake and whether the absorbed Sr would be released with longer culture times were examined. Specifically, the Sr uptake-inducing bacteria #101235 were cultured with shaking in an Sr solution, and the Sr concentration in the culture supernatant was measured in the same manner as in Example 2 to determine the Sr concentration absorbed by the bacteria.

[0025] Three 1000-mL Erlenmeyer flasks containing 300 mL of Sr uptake induction medium were inoculated with 3 mL of the preculture solution, and Sr uptake induction culture was performed at 30°C and 110 rpm for 24 hours. After 24 hours, the three cultures were mixed and homogenized to prepare 900 mL of Sr uptake induction culture. 30 mL of this culture was dispensed into 50-mL tubes and centrifuged at 1500 rpm for 10 minutes. The resulting precipitate was suspended in 10 mL of water and centrifuged again to obtain the precipitate. This precipitate constituted the Sr uptake induction bacterial cell (washed bacterial pellet) for 30 mL of Sr uptake induction culture. 30 mL of 20 mg / L Sr aqueous solution was added and suspended, and the suspension was transferred to a 300-mL baffled Erlenmeyer flask and cultured at 30°C and 110 rpm for the specified time. The culture was centrifuged, and the Sr concentration in the supernatant was measured. For #101235, measurements were taken at seven time points over a long period of time, ranging from 3 to 60 hours of culture.

[0026] The results are shown in Figure 3. The absorption rate increased almost linearly up to 12 hours after the start of incubation in the Sr solution. The increase then slowed, and after 23 hours, almost no change was observed for up to 60 hours of continued analysis. This data allowed us to determine the Sr absorption incubation time that provided the highest absorption capacity and the time period during which the amount of absorption decreased, allowing us to set an effective Sr absorption incubation time. Since approximately 85% of the Sr was absorbed 12 hours after the start of incubation, Sr can be concentrated and removed by culturing Sr-inducible bacteria for 12 hours or more and then recovering the bacterial cells. Although the data are not shown here, when the bacterial cells were collected and washed twice with pure water, approximately 10% of the Sr was eluted, but the remainder remained in the bacterial pellet, indicating that it was stably retained by the bacteria.

[0027] The dry weight of the solid portion of one washed bacterial pellet was 31 mg. If 90% of the 20 mg / L of Sr is absorbed, the amount of Sr absorbed in 30 mL would be 0.54 mg, which is treated by 31 mg of solids. In other words, the amount of treatment per weight is very high.

[0028] [Example 4] Examination of methods for preserving bacterial cells Since the efficient absorption of Sr by the bacterial cells was demonstrated, we investigated whether long-term storage while maintaining Sr absorption capacity was possible. Bacteria were cultured using washed bacterial pellets (Sr-absorption-induced bacterial cells) prepared by the method described in Example 3, and Sr absorption capacity was induced. The bacteria were collected by centrifugation, washed with pure water, and then centrifuged again to collect the bacteria (washed bacterial pellets). The washed bacterial pellets were stored at 25°C, 4°C, and -80°C, and then their Sr absorption capacity was measured to analyze whether Sr absorption capacity had been maintained. Sr absorption capacity was measured by suspending the bacteria in an aqueous Sr solution, culturing them for 24 hours, measuring the Sr concentration in the supernatant, and calculating the absorption rate. The results are shown in Table 2.

[0029] [Table 2]

[0030] Immediately after induction of Sr uptake, the Sr uptake rate was 72.2%, but when stored at 4°C or -80°C, Sr uptake rates remained above 60% even after 34 days. Storage at 4°C tended to result in slightly lower Sr uptake rates compared to storage at -80°C, but the difference was not significant. When stored at 25°C, spoilage was observed on the 17th day, so measurements were not performed thereafter. Even when stored at 4°C, spoilage is still possible with longer storage periods. Therefore, frozen storage, e.g., at -20°C to -80°C or below, is preferred for storage of more than one month. Similar to common bacterial storage methods, for example, freezing in liquid nitrogen (-196°C) followed by storage at 0°C or below is thought to maintain Sr uptake rates. Considering that the Sr absorption capacity varies between 70 and 90% for each culture lot, Sr can be absorbed and removed more efficiently by measuring Sr absorption capacity, storing lots with high absorption capacity at low temperatures, and using them in a controlled area.

[0031] [Example 5] Microscopic observation of spore-forming ability of spore-forming bacteria with different storage periods and temperatures As in Example 4, the washed bacterial pellets were stored under different temperature and time conditions, then suspended in an aqueous Sr solution and subjected to Sr absorption culture for 24 hours. The bacterial suspension immediately after the Sr absorption culture (before centrifugation) and the bacterial suspension at the end of the main culture were stained for spores and observed under a microscope to confirm spore formation (Figure 4). Spore staining was performed using the Meller staining method. While stained red in color, the light-colored, spherical white triangles in the figure represent spores. Spore formation was observed at the end of the main culture, and morphological observation confirmed that numerous spores were formed after Sr absorption culture at all storage temperatures.

[0032] [Water treatment equipment using bacteria with Sr absorption ability] This paper describes a water treatment system that uses bacteria capable of strontium absorption to treat contaminated water. As shown in Figure 5, contaminated water is first adjusted in a contaminated water adjustment tank to conditions that allow bacterial survival, such as pH and ion concentration. If the contaminated water's pH is too acidic or alkaline, a pH adjuster is added to adjust it to a pH suitable for spore formation. Furthermore, electrical conductivity is measured to estimate the concentration of ions important for spore formation, such as calcium ions, and to confirm that spore formation is not hindered. Furthermore, to allow spore formation to continue in the absorption tank, conditions that do not hinder spore formation, i.e., a nutrient-poor state, are monitored. In the case of contaminated water treatment at the Fukushima Daiichi Nuclear Power Plant, the water quality is relatively consistent and does not contain high concentrations of organic matter or calcium. However, if a certain value is exceeded, water can be added to adjust the water quality. Organic matter can be measured by measuring COD (chemical oxygen demand), BOD (biochemical oxygen demand), and TOC (total organic carbon), or the amount of glucose in the contaminated water can be measured using a glucose sensor. In the contaminated water adjustment tank, the water in the tank may be sampled as needed to measure pH, ion concentration, organic matter, etc., but in order to reduce the risk of exposure, it is preferable to install automatic pH sensors, conductivity measuring devices, COD, BOD, and TOD measuring devices in the contaminated water adjustment tank to monitor and automatically adjust the temperature. It is also preferable to measure the water temperature and adjust it to a temperature suitable for the habitat of microorganisms (approximately 25°C). The contaminated water adjustment tank is equipped with an agitator to stir the water when pH adjusters, etc. are added, and to maintain a constant water quality.

[0033] After the contaminated water has been adjusted to a certain quality in the contaminated water adjustment tank, it is sent to the absorption tank. In the absorption tank, the contaminated water is mixed with bacteria in the spore-forming process that have been cultivated and stored outside the radiation control area. The absorption tank is aerated for at least 24 hours to absorb Sr. The absorption tank is equipped with an aeration device for aeration, a heating and cooling device to maintain a constant temperature, and an agitator to cultivate the bacteria and efficiently expose them to Sr. Spores that have formed and absorbed sufficient Sr are transferred to the solid-liquid separation tank. Because it is thought that some bacteria will not fully spore within 24 hours, the solid-liquid separation tank is also equipped with a heating and cooling device and an aeration device to allow continued spore formation. Here, a separation membrane is used to separate the solid and liquid into Sr-purified water and Sr-absorbed spore-forming bacteria, but any separation method can be used. For example, spore-forming bacteria may be precipitated and separated into a supernatant and a precipitate, and the precipitate may be further centrifuged, compressed, or the like to remove water, thereby separating the Sr-purified water and Sr-containing bacterial cells.

[0034] Compared to the conventional water treatment device shown in Figure 6, the water treatment device of this embodiment not only does not require a culture tank for culturing vegetative cells, but also requires only an absorption tank and a solid-liquid separation tank in addition to a wastewater adjustment tank, making it a very compact water treatment device. Furthermore, because bacteria in the spore-forming process can be directly added, Sr can be absorbed in about 24 hours, shortening the time required for Sr purification. As shown above, water treatment according to this embodiment not only minimizes the risk of exposure during work, but also significantly reduces time and costs. [Industrial Applicability]

[0035] Since the work time in the radiation controlled area is short, the risk of exposure during work can be minimized. In addition, since the bacteria are preserved in a spore-forming state, the state of the bacteria is easy to control, and bacteria with high spore-forming ability can be stably supplied, maintaining high contamination treatment efficiency. As with conventional methods, metal ions are concentrated using microorganisms, so compared to methods using adsorbents for removal, contaminated water can be treated quickly and at low cost, and the amount of industrial waste generated is extremely small, while still maintaining the advantages of safe and efficient contaminated water treatment.

Claims

1. A method for treating radioactive contaminated water, comprising: an adjusting step of adjusting the contaminated water to an environment in which spore-forming bacteria can survive; an absorption process in which bacteria in the spore-forming process, which have been induced to form spores in advance, are introduced into the conditioned contaminated water to absorb strontium; A contaminated water treatment method comprising a solid-liquid separation step for separating strontium-purified water from a solid containing strontium.

2. The bacteria undergoing the spore-forming process are cultured outside of a radiation-controlled area to induce spore-forming ability, Washing and concentration are carried out while the bacteria are capable of forming spores.

2. The method for treating contaminated water according to claim 1, further comprising storing the contaminated water.

3. 3. The method for treating contaminated water according to claim 2, wherein the bacteria in the spore-forming process are stored at a temperature of 4°C or less.

4. 4. The method for treating contaminated water according to claim 3, wherein the bacteria in the spore-forming process are stored at freezing temperatures.

5. A water treatment device using spore-forming bacteria, a contaminated water adjustment tank for adjusting the contaminated water to an environment in which spore-forming bacteria can survive; An absorption tank into which bacteria in the spore-forming process are introduced to absorb strontium; A water treatment device comprising a solid-liquid separation tank for separating Sr-purified water from a solid containing concentrated Sr.

6. The contaminated water adjustment tank is a tank that adjusts the water quality so that microorganisms can grow. Equipped with a pH adjusting device and / or a diluting device, 6. The water treatment device according to claim 5, wherein the absorption tank is provided with at least one of an aeration device, a heating / cooling device, and an agitator to allow the bacteria in the spore-forming process to efficiently form spores.

7. 7. The water treatment device according to claim 5, wherein the solid-liquid separation tank is provided with a separation membrane for performing solid-liquid separation.

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