In-situ remediation method

Abstract

Provided is an in-situ remediation method comprising spraying a specific dechlorination microorganism classified into the genus Dehalogenimonas on a soil or an aquifer contaminated with a chlorine compound, and dechlorinating the chlorine compound.

Description

In-situ purification method

[0001] The present invention relates to an in-situ purification method using dechlorinating microorganisms. This application claims priority based on Japanese Patent Application No. 2024-047751 filed in Japan on March 25, 2024, Japanese Patent Application No. 2024-082077 filed in Japan on May 20, 2024, and Japanese Patent Application No. 2024-205553 filed in Japan on November 26, 2024, the contents of which are incorporated herein by reference.

[0002] One known method for purifying contaminated soil with volatile organic compounds (VOCs) is to excavate and remove the contaminated soil (excavation and removal method). However, this method requires the removal and transportation of large amounts of contaminated soil, which is extremely costly.

[0003] To address these problems, for example, Patent Document 1 proposes a soil purification method that utilizes bioremediation (biological environmental restoration) to activate microorganisms to decompose pollutants such as VOCs. The invention of Patent Document 1 aims to efficiently purify groundwater in the soil.

[0004] Japanese Patent Application Laid-Open No. 2021-90927

[0005] Conventional techniques have the problem that bioremediation of contaminants such as chlorinated ethylenes cannot be applied when the salinity (sodium chloride concentration) of groundwater in contaminated soil is high (e.g., 0.5% by mass or more). However, Patent Document 1 does not take into consideration the salinity of groundwater in contaminated soil.

[0006] The present invention has been made in view of the above circumstances, and aims to provide an in-situ remediation method using dechlorinating microorganisms that can be applied even when the salt concentration of groundwater in contaminated soil is high.

[0007] In order to solve the above problems, the present invention has the following aspects. [1] An in-situ remediation method comprising spraying a dechlorinating microorganism classified into the genus Dehalogenimonas, having the accession number NITE BP-04066, onto soil or an aquifer contaminated with chlorinated compounds to dechlorinate the chlorinated compounds. [2] The in-situ remediation method according to [1], wherein the sodium chloride concentration contained in the water of the soil or the aquifer is 0.5% by mass or more and 10.0% by mass or less. [3] The in-situ remediation method according to [1] or [2], wherein the chlorinated compounds are chlorinated ethylenes.

[0008] According to the in-situ remediation method of the present invention, even if the groundwater in the contaminated soil has a high salt concentration, it can be purified.

[0009] 1 is a graph showing the results of Test Example 1, in which VOC concentrations were measured in a laboratory test using a dechlorinating microorganism according to one embodiment of the present invention. FIG. 2 is an electron microscope image of a bacterium (dechlorinating microorganism) classified in the genus Dehalogenimonas isolated in the Examples. FIG. 3 is a graph showing the results of Test Example 2, in which VOC concentrations were measured in a laboratory test using a dechlorinating microorganism according to one embodiment of the present invention. FIG. 4 is a graph showing the results of Test Example 3, in which VOC concentrations were measured in a laboratory test using a dechlorinating microorganism according to one embodiment of the present invention. FIG. 5 is a graph showing the results of Test Example 4, in which the dechlorinating activity of a dechlorinating microorganism according to one embodiment of the present invention was compared with that of a known bacterium belonging to the genus Dehalococcoides.

[0010] <Dechlorinating Microorganism> The dechlorinating microorganism used in the present invention is a bacterium classified in the genus Dehalogenimonas. The inventors isolated a bacterium classified in the genus Dehalogenimonas using the method described in the Examples below and deposited it at the Patent Microorganisms Depositary of the National Institute of Technology and Evaluation. Surprisingly, the isolated bacterium of the present invention (hereinafter referred to as the "isolated bacterium") can dechlorinate chlorinated ethylenes such as trichloroethylene and decompose them into ethylene even in an aqueous solution containing a salt content of 0.5 wt% or more. Analysis of the 16S rRNA gene using conventional methods clearly revealed that the bacterium is classified in the genus Dehalogenimonas, but species identification has not been completed. It is believed that the species to which the isolated bacterium belongs can dechlorinate organic chlorine compounds (hereinafter referred to as "chlorine compounds") even in a high-salt environment, similar to the isolated bacterium.

[0011] Conventional bacteria of the genus Dehalococcoides are known as dechlorinating bacteria capable of dechlorinating chlorinated ethylenes, but their dechlorination activity is significantly reduced when the salinity is high (e.g., 0.5% by mass or higher). Therefore, they cannot be used in sites where high-salinity groundwater, such as brackish water areas, exists. In contrast, the present isolated bacteria maintain their dechlorination activity even at high salinity levels. Therefore, they can be used in sites where high-salinity groundwater, such as brackish water areas, exists.

[0012] The isolated bacterium is capable of dechlorinating chlorinated ethylenes by itself, but can also exhibit dechlorination function when mixed with bacteria other than the isolated bacterium (a so-called consortium) to form a microbial community. In this embodiment of the microbial community, the proportion of Dehalogenimonas bacteria in the dechlorinating microbial consortium, as identified by amplicon sequencing analysis, is preferably 60% or more, more preferably 70% or more, and even more preferably 75% or more, relative to the total number of bacteria in the dechlorinating microbial consortium. When the proportion of Dehalogenimonas bacteria is equal to or greater than the above-mentioned lower limit, dechlorination of chlorinated compounds can be further promoted. Here, "amplicon sequencing analysis" is a known analytical method that clarifies the types and proportions of bacteria contained in a sample microbial community. Specifically, this method involves directly extracting the DNA of a bacterial population from a collected sample without culturing, and analyzing the sequence data of the 16S rRNA gene.

[0013] When the isolated bacterium or dechlorinating microbial consortium is applied to soil or an aquifer contaminated with chlorine compounds, the sodium chloride concentration in the contaminated soil (hereinafter also referred to as "salt concentration") is, for example, preferably 0.5% by mass to 10.0% by mass, more preferably 1.0% by mass to 7.5% by mass, even more preferably 1.0% by mass to 6.0% by mass, and particularly preferably 1.0% by mass to 5.0% by mass. Within these preferred ranges, the sodium chloride concentration may be 1.0% by mass to 4.0% by mass, 1.5% by mass to 3.5% by mass, or 2.0% by mass to 3.0% by mass. When the salt concentration is within the above range, the Dehalogenimonas bacteria can be suitably applied to brackish water areas such as coastal areas where freshwater and seawater coexist. Here, the salt concentration can be determined by collecting groundwater from the contaminated soil and measuring the electrical conductivity using a known method. In this specification, the term "aquifer" refers to a stratum (saturated zone) in which the pores of the soil are filled with groundwater.

[0014] When the present isolated bacterium or dechlorinating microbial consortium is applied to soil or an aquifer contaminated with chlorinated compounds, the pH of the contaminated soil is preferably, for example, 6.5 to 9.4, more preferably 6.8 to 9.0, and even more preferably 7.2 to 8.8. Furthermore, pH ranges of 7.6 to 8.6, 7.8 to 8.5, 8.0 to 8.5, and 8.1 to 8.4 are also particularly preferred. When the pH of the contaminated soil is within the above preferred range, the efficiency of dechlorination of chlorinated compounds by Dehalogenimonas bacteria is further enhanced. The pH of the contaminated soil can be determined by collecting groundwater (water contained in the aquifer) in the contaminated soil and measuring the pH using a known method. The temperature of the groundwater used to measure the pH is preferably 20 to 35°C.

[0015] <<In-situ remediation method>> In the in-situ remediation method according to the present invention, the isolated bacterium (the present isolated bacterium) can be applied alone or as a consortium to purify soil or water contaminated with organic chlorine compounds (particularly chlorinated ethylenes). One embodiment thereof is exemplified below. Below, the case where the isolated bacterium is used alone will be described, but it can also be used as a consortium in the same manner. The in-situ remediation method of this embodiment is a method in which the present isolated bacterium is sprayed on soil or an aquifer contaminated with chlorine compounds to dechlorinate the chlorine compounds and purify the soil or aquifer. When applying the present isolated bacterium to the soil or aquifer, the in-situ remediation method for contaminated soil of this embodiment preferably includes the following steps:

[0016] <Culturing step> The culturing step is a step of culturing the present isolated bacterium. The method for culturing the present isolated bacterium is not particularly limited, and for example, any known method that can be used to culture conventional Dehalogenimonas bacteria can be applied. Large-scale culture can be performed by increasing the size of the culture vessel for each passage.

[0017] In the culture process, first, a sterilized culture medium is prepared and placed in a sterilized culture vessel. Examples of the culture medium include the culture medium described in the Examples. Methods for sterilizing the culture medium include high-pressure steam sterilization (autoclave), dry heat sterilization, and filtration sterilization. Examples of the culture vessel include flasks, culture medium bottles, vials, petri dishes, and dishes. The size of the culture vessel is not particularly limited and can be adjusted appropriately depending on, for example, the size of the target treatment area, the contamination state, and the like.

[0018] To shorten the doubling time of the bacteria to be cultured, it is preferable to ventilate the culture vessel with an inert gas such as nitrogen gas or argon gas to expel oxygen and create anaerobic conditions. The anaerobic conditions can be achieved, for example, by managing them in a glove box or the like.

[0019] The culture temperature is, for example, preferably 20 to 50°C, more preferably 20 to 35°C. When the culture temperature is equal to or higher than the lower limit, the doubling time of the cultured bacteria can be shortened. When the culture temperature is equal to or lower than the upper limit, a decrease in the number of bacteria can be suppressed.

[0020] From the viewpoint of shortening the doubling time of the cultured bacteria, the culture step is preferably carried out in a dark place. The culture step is preferably static culture, but may also be cultured using, for example, a jar fermenter.

[0021] The culture period is not particularly limited, but is preferably, for example, 7 to 30 days. When the culture period is equal to or greater than the above-mentioned lower limit, a sufficient number of bacteria can be cultured. When the culture period is equal to or less than the above-mentioned upper limit, the time required for purifying the aquifer can be shortened, and the efficiency of culturing the bacteria can be further improved.

[0022] To confirm the efficiency of dechlorination, the medium may be sampled, for example, once every 7 to 10 days during the culture step, and the decomposition ability of chlorine compounds may be measured. It is preferable to preliminarily add chlorine compounds to the medium and quantify the decomposition products. The quantification of chlorine compounds can be performed, for example, by gas chromatography-mass spectrometry (GC / MS).

[0023] To further increase the number of bacteria, the culture step may involve large-scale culture. Here, "large-scale culture" refers to increasing the number (volume) of bacteria (culture product) through two or more stages. In large-scale culture, for example, a medium on a scale of 100 to 1000 mL is prepared, bacteria are cultured, and then the culture liquid is inoculated into 1 L to 100 L of culture medium to increase the number of bacteria. By performing large-scale culture, the isolated bacteria can be applied to a wider range of treatment target areas.

[0024] <Injection Step> The injection step is a step of injecting the present isolated bacterium into soil or an aquifer contaminated with chlorine compounds. In the injection step, the present isolated bacterium is first prepared in the area to be treated. From the viewpoint of easily maintaining the dechlorination activity of the present isolated bacterium, it is preferable to transport the present isolated bacterium to the area to be treated in a manner that prevents air from entering.

[0025] The method for injecting the isolated bacteria into the aquifer is not particularly limited, and any conventionally known injection method can be used. A method in which the isolated bacteria are injected together with a culture solution is preferred. The injection method may be gravity injection (gravity injection) or pressure injection (pressure injection).

[0026] Gravity injection is a method in which the isolated bacteria are injected into the treatment area using only the hydraulic head pressure, which is the difference between the liquid level of the culture medium being injected and the groundwater level, without pressurization. In gravity injection, the hydraulic head pressure is preferably, for example, 1 to 10 m, and more preferably 2 to 8 m. When the hydraulic head pressure is equal to or greater than the lower limit, the culture medium can be more reliably injected into the treatment area. When the hydraulic head pressure is equal to or less than the upper limit, the equipment for injecting the culture medium can be made smaller. The hydraulic head pressure is expressed as the difference between the liquid level of the culture medium at the time of injection and the liquid level of the groundwater level.

[0027] Pressurized injection is a method in which the culture solution to be injected is pressurized to inject the isolated bacteria into the area to be treated. In pressurized injection, the pressure to be applied is, for example, preferably more than 0 MPa and not more than 2.0 MPa, and more preferably more than 0 MPa and not more than 1.5 MPa. If the pressure to be applied is above the lower limit, the culture solution can be more reliably injected into the area to be treated. If the pressure to be applied is not more than the upper limit, the equipment for injecting the culture solution can be made smaller. The pressure to be applied is represented by the gauge pressure of the piping when injecting the culture solution.

[0028] Examples of pressurized injection include a method in which the culture solution is placed in a pipe and pressure-fed using a pump or the like, a method using a double-pipe strainer method, and a method using a double packer method. When pressure-fed the culture solution using a pump or the like, it is preferable that the culture solution does not come into contact with air, from the viewpoint of easily maintaining the dechlorination activity. Therefore, it is preferable not to use compressed air during pressure-fed. Examples of gases used during pressure-fed include oxygen-free gases such as nitrogen gas and argon gas.

[0029] The double-pipe strainer method is a method in which two different types of liquid are injected into the treatment area using a double pipe with an inner pipe and an outer pipe. Examples of the two different types of liquid include a culture medium containing the present isolated bacterium, a culture medium with a different concentration of the present isolated bacterium, and a nutrient that promotes the activity of the present isolated bacterium. The double-packer method is a method in which the depth to which the culture medium is injected is limited by using a double-pipe packer with an inner pipe and an outer pipe.

[0030] In the injection step, when injecting the culture solution into the treatment target area, a reducing agent or the like having an oxygen-removing effect may be further applied in order to remove oxygen from the ground in the treatment target area. Examples of such reducing agents include reduced iron powder and sodium sulfide. When compressed air is used for pressure feeding, the reducing agent may be applied to the treatment target area after the culture solution is injected into the treatment target area. Methods for applying the reducing agent to the treatment target area include spraying the reducing agent on the treatment target area and injecting a liquid in which the reducing agent has been dispersed into the treatment target area.

[0031] <Agitation step> The agitation step is a step of uniformly dispersing the isolated bacteria injected into the treatment area by agitation. For example, heavy machinery used for ground improvement at deep depths (e.g., 5 m or less underground), such as a columnar improvement machine, can be used in the agitation step. Examples of such heavy machinery include heavy machinery equipped with a shaft and agitator blades. The shaft may be a single shaft or multiple shafts.

[0032] Examples of mixing methods include the Power Blender (registered trademark) method, which uses a trencher-type mixing blade, and the TRD method (soil cement underground continuous wall method), which uses a chainsaw-type cutter post.

[0033] In addition to the culturing, injection, and agitation steps described above, the in-situ remediation method for contaminated soil using the isolated bacteria may also include physical or chemical diffusion prevention measures to prevent the applied microorganisms from diffusing outside the treatment area. Examples of physical diffusion prevention measures include the installation of impermeable walls. Examples of impermeable walls include steel sheet piles, grout injection walls, water glass injection walls, and impermeable walls formed by agitating soil cement, bentonite, or the like within the treatment area.

[0034] When a water impermeable wall is installed, the area around the wall may become alkaline. Therefore, when installing a water impermeable wall, it is preferable to separately inject a neutralizing agent or the like around the wall and stir it. Examples of neutralizing agents include aqueous solutions of strong alkalis such as sodium hydroxide and calcium hydroxide, and bases with buffering properties such as phosphates and organic acid salts.

[0035] Other physical measures to prevent diffusion include installing pumping wells in the area to be treated and pumping up groundwater to prevent groundwater within the area to be treated from leaking outside the area.

[0036] Chemical prevention measures include, for example, introducing air or oxygen-containing gases from wells within the treatment area to increase the dissolved oxygen concentration in the groundwater. More specifically, methods include installing wells or trenches within the treatment area and blowing air or compressed air into them.

[0037] The containment measures may be a combination of physical and chemical containment measures, for example, a physical containment measure may be implemented upstream of the groundwater flow and a chemical containment measure may be implemented downstream of the groundwater flow.

[0038] <Dechlorination process> The dechlorination process involves spraying the isolated bacterium on soil or an aquifer, and then dechlorinating the chlorine compounds contained therein. In the dechlorination process, harmful chlorine compounds are converted into harmless compounds, thereby purifying the aquifer.

[0039] Examples of chlorinated compounds include chlorinated ethylenes such as tetrachloroethylene (PCE), trichloroethylene (TCE), cis-1,2-dichloroethylene (cis-DCE), chloroethylenes (CE, VE), etc. These chlorinated compounds are dechlorinated by the isolated bacterium to produce harmless ethylene (ETH).

[0040] The dechlorination step can also be considered as a step of culturing the isolated bacterium while purifying it. The period of the dechlorination step is preferably 20 days or more, more preferably 25 days or more, and even more preferably 30 days or more. When the period of this step is equal to or greater than the above-mentioned lower limit, the effect of dechlorinating chlorine compounds can be further enhanced. The upper limit of the period of this step is not particularly limited, but a guideline is, for example, 100 days. The starting point of the period of this step refers to the time when the isolated bacterium is first injected into the soil or aquifer.

[0041] In the dechlorination process, the isolated bacteria may be further injected into the soil or aquifer, which will further enhance the effect of dechlorinating chlorinated compounds.

[0042] The culture temperature in the dechlorination step is, for example, preferably 20 to 40°C, more preferably 20 to 35°C. When the culture temperature is equal to or higher than the lower limit, the doubling time of the cultured bacteria can be shortened. When the culture temperature is equal to or lower than the upper limit, the decrease in the number of bacteria can be suppressed. Note that the "culture temperature in the dechlorination step" refers to the underground temperature at a depth of 2 m from the surface of the area to be treated.

[0043] The sodium chloride concentration (salt concentration) of the water contained in the soil or aquifer in the dechlorination process is, for example, preferably 0.5% by mass to 10.0% by mass, more preferably 1.0% by mass to 7.5% by mass, even more preferably 1.0% by mass to 6.0% by mass, and particularly preferably 1.0% by mass to 5.0% by mass. Within these preferred ranges, it may be 1.0% by mass to 4.0% by mass, 1.5% by mass to 3.5% by mass, or 2.0% by mass to 3.0% by mass. When the salt concentration is above the above lower limit, the isolated bacterium can be suitably applied to brackish water areas such as coastal areas where freshwater and seawater coexist. When the salt concentration is below the above upper limit, the activity of the isolated bacterium can be better maintained. The salt concentration can be determined by collecting groundwater from the contaminated soil and measuring its electrical conductivity using a known method.

[0044] The pH of the water contained in the soil or aquifer in the dechlorination step is preferably 6.5 to 9.4, more preferably 6.8 to 9.0, and even more preferably 7.2 to 8.8. Furthermore, pH ranges of 7.6 to 8.6, 7.8 to 8.5, 8.0 to 8.5, and 8.1 to 8.4 are particularly preferred. When the pH of the water contained in the soil or aquifer is within the above preferred range, the efficiency of dechlorination of chlorine compounds by Dehalogenimonas bacteria is further enhanced. Here, the pH can be determined by collecting water contained in the soil or aquifer and measuring the pH using a known method. The temperature of the water used to measure the pH is preferably 20 to 35°C. In the in-situ remediation method described above, an acid, alkali, or a known pH adjuster may be sprayed or injected into the soil or aquifer to be treated in order to adjust the pH of the water contained in the soil or aquifer.

[0045] The in-situ remediation method of the present invention uses the isolated bacteria described above, so it can be applied even when the groundwater in the contaminated soil has a high salt concentration. Therefore, in brackish water areas such as coastal areas where fresh water and seawater coexist, harmful chlorine compounds can be converted into harmless compounds, and contaminated aquifers can be purified.

[0046] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0047] Test Example 1 Liquid medium A, trace element group SL-10, selenium-tungsten solution, and resazurin solution were prepared by adding the medium components with the compositions shown in Table 1 to 1 L of pure water. The NaCl concentration of the prepared liquid medium A was 20 g / L (2.0% by mass). Vitamin solution B with the composition shown in Table 2 was also prepared in 200 mL of pure water.

[0048]

[0049]

[0050] In a 50 mL vial sterilized by autoclaving, 20 mL of liquid medium A, 200 μL of vitamin solution B, and 15 mM sodium sulfide (Na ２ 200 μL of a 150 mM nitrilotriacetic acid (S) aqueous solution, 200 μL of a 150 mM nitrilotriacetic acid (NIT) aqueous solution, 0.5 M formic acid (SO4) aqueous solution, and 1 μL of trichloroethylene (TCE) were added, and the mixture was purged with nitrogen or argon gas for 1 to 2 minutes. After purging, 1 mL of a culture solution containing the isolated bacteria of the present invention was inoculated, and static culture was performed in a dark room at 23°C. Similar static culture was performed on five vials, including spares. During static culture, the vials were sealed with butyl caps and aluminum stoppers to prevent gas ingress and egress. These static cultures were performed in a glove box. During static culture, 0.1 mL of the medium in the vials was sampled with a needle every 7 or 10 days, and chlorinated ethylenes and ethylene were quantified by gas chromatography / mass spectrometry (GC / MS). The results are shown in Figure 1.

[0051] The isolated bacteria used in this example were obtained by the inventors by repeatedly diluting and subculturing a strain capable of degrading dechlorinated compounds from saline soil. Conventional 16S rRNA gene analysis revealed that the bacteria belonged to the genus Dehalogenimonas. The isolated bacteria obtained here were deposited by the inventors at the Patent Microorganism Depositary Center, National Institute of Technology and Evaluation (Room 122, 2-5-8 Kazusa Kamatari, Kisarazu City, Chiba Prefecture, Japan 292-0818) and received under the accession number NITE AP-04066 (received on January 16, 2024). Subsequently, they were deposited on June 3, 2024 under the accession number P-04066. Furthermore, they have now been transferred to an international depository, and their accession number is NITE BP-04066.

[0052] As shown in Figure 1, among the VOCs collected from the culture medium to which the isolated bacteria were applied, the concentrations of TCE and cis-DCE were confirmed to be 0 μM after 36 days of static culture. The VC concentration reached its highest level after 36 days of static culture but decreased as static culture continued, confirming that VC, which is normally difficult to dechlorinate, was also reliably dechlorinated. Furthermore, it was confirmed that harmless ethylene (ETH) was obtained as the dechlorination of chlorinated ethylenes progressed. This dechlorination proceeded in an environment with a sodium chloride concentration of 2% by mass, confirming that the present invention can also be applied to contaminated soil in brackish water areas with high sodium chloride concentrations.

[0053] Test Example 2: A trichloroethylene (TCE) degradation test using the isolated bacterium was conducted in the same manner as in Test Example 1, except that the NaCl concentration in liquid medium A was changed to 1.0 mass%, 2.0 mass% (repeat experiment), 3.0 mass%, 3.6 mass%, and 4.0 mass%. The results are shown in Figure 3. In the figure, the horizontal axis represents the culture period, and the vertical axis represents the amount of each chlorine compound. As shown in Figure 3, it was confirmed that TCE was sufficiently decomposed into harmless ethylene (ETH) at all sodium chloride concentrations. Within the above NaCl concentration range, it was found that concentrations lower than 4.0 mass% improved the decomposition rate of vinyl chloride (VC), which is normally difficult to dechlorinate.

[0054] Test Example 3 A trichloroethylene (TCE) degradation test was conducted using the isolated bacterium described above in the same manner as in Test Example 1, except that the NaCl concentration of liquid medium A was set to 2.0% by mass and the pH was changed to 5.9, 6.5, 7.0, 8.1, 8.4, 9.4, or 10.1 by varying the nitrogen bubbling time and the amount of sodium bicarbonate added. The results are shown in Figures 4 and 5. In each figure, the horizontal axis represents the culture period, and the vertical axis represents the amount of each chlorine compound.

[0055] The results of dechlorination and bacterial count measurements in long-term culture at pH 8.4 and pH 9.4, performed in Test Example 3, are shown in Figure 6. In each figure, the horizontal axis represents the culture period, and the vertical axis represents the amount of each chlorine compound and the density of isolated bacteria in the medium (bacterial density). The bacterial density was determined by measuring the number of bacteria contained in 1 mL of medium according to a standard method using a cell counter.

[0056] In Test Example 3, TCE was dechlorinated at pH 6.5 to 9.4. The dechlorination effect was particularly high at pH 8.1 to 8.4, and harmless ethylene (ETH) was obtained.

[0057] Test Example 4: Dehalococcoides bacteria, known dechlorinating bacteria used in bioaugmentation, are known to have dechlorination activity only within a limited range of pH and NaCl concentrations (see References 1 and 2). The dechlorination activity of representative Dehalococcoides bacteria is shown in Figure 7. The vertical axis of the figure shows the specific dechlorination activity (calculated as a relative value, with the number of moles of decomposition products after cultivation set at 1.0 for the test system with the highest concentration). 7 shows that the NIT-SK1 strain, an isolated Dehalogenimonas bacterium (accession number: P-04066) according to the present invention, has dechlorination activity over a wider pH range than Dehalococcoides bacteria (Dehalococcoides bacteria: pH 6-8, NIT-SK1 strain: pH 6.5-9.4), and also over a wider NaCl concentration range (Dehalococcoides bacteria: 0-1%, NIT-SK1 strain: 0-4%). ​​This suggests that bioaugmentation using the NIT-SK1 strain can accommodate a wider range of environmental conditions and has a wider range of application. The test method for Test Example 4 was the same as that for Test Examples 1-3 described above.

[0058] Reference 1: International Journal of Systematic and Evolutionary Microbiology (2013), 63, 625-635 Reference 2: Environmental Research 207 (2022) 112150

[0059] The Sustainable Development Goals (SDGs) are 17 international goals adopted at the United Nations Summit in September 2015. The method for in-situ remediation of contaminated soil using the isolated bacterium of the present invention can contribute to the achievement of one of the 17 SDGs, for example, goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation."

Claims

1. An in-situ remediation method in which a dechlorinating microorganism classified into the genus Dehalogenimonas, having the accession number NITE BP-04066, is sprayed onto soil or an aquifer contaminated with chlorine compounds to dechlorinate the chlorine compounds.

2. The in-situ remediation method according to claim 1, wherein the concentration of sodium chloride contained in the soil or the water in the aquifer is 0.5 mass % or more and 10.0 mass % or less.

3. The in-situ purification method according to claim 1 or 2, wherein the chlorine compound is a chlorinated ethylene.

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