Temperature control system, soil purification system, temperature control method, and soil purification method

Abstract

To provide a temperature control system, a soil purification system, a temperature control method, and a soil purification method which can achieve efficient soil purification in soil purification using heating means.SOLUTION: A temperature control system is used in soil purification using heating means, and includes: temperature measurement means 11 for measuring a temperature around a boundary between an aquifer W and an aquitard A; a pumping well 12 for pumping up underground water from around the boundary; a cooler 14 for cooling the underground water pumped up by the pumping well 12; and a water injection well 15 for injecting the underground water cooled by the cooler 14 into the area around the boundary.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a temperature adjustment system, a soil remediation system, a temperature adjustment method, and a soil remediation method. [Background technology]

[0002] Generally, volatile organic compounds (VOCs) such as tetrachloroethylene (PCE) are heavier and less viscous than water, so when they leak into the ground, they seep underground and move downward within the aquifer, remaining underground in low-permeability layers (clay or silt layers, etc.), thereby contaminating not only the aquifer but also the low-permeability layers. A known method for purifying soil contaminated by VOCs is a combination of soil heating and biological purification. This purification method heats the low-permeability layer to leach the VOCs into the aquifer, and then purifies the migrated VOCs with microorganisms. Conventionally, a technique disclosed in Patent Document 1 is known as a method for purifying soil and groundwater contaminated with volatile organic compounds using microorganisms. The purification method of Patent Document 1 is configured such that a first water injection well is disposed on one side of a contaminated area contaminated with volatile organic compounds, and a second water injection well is disposed on the other side of the contaminated area, with a pumping well disposed between them. Then, an anaerobic decomposition area is formed in one contaminated area by anaerobic microorganisms by a first circulation in which water supplied from the first water injection well is circulated to one contaminated area and pumped up by the pumping well, and an aerobic decomposition area is formed in the other contaminated area by aerobic microorganisms by a second circulation in which water supplied from the second water injection well is circulated to the other contaminated area and pumped up by the pumping well. Then, the second circulation is configured to cool the water supplied from the second water injection well to increase the amount of dissolved oxygen. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-160175 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the purification method of Patent Document 1, when the aquifer is heated, there is a risk that the temperature of the aquifer will become high and unsuitable for microbial purification. On the other hand, when the temperature of the aquifer is raised to a temperature suitable for microbial purification, the temperature of the aquifer cannot be raised sufficiently, which is a problem in that it becomes difficult to leach volatile organic compounds into the aquifer. An object of the present invention is to solve the above-mentioned problems and to propose a temperature adjustment system, a soil remediation system, a temperature adjustment method, and a soil remediation method that can realize efficient soil remediation in soil remediation using a heating means. [Means for solving the problem]

[0005] In order to solve the above problems, the temperature control system of the present invention is a temperature control system for soil purification using a heating means. The temperature control system includes a temperature measurement means for measuring the temperature near the boundary between an aquifer and a low-permeability layer, a pumping well for pumping groundwater from near the boundary, a cooling device for cooling the groundwater pumped by the pumping well, and an injection well for injecting the groundwater cooled by the cooling device into the boundary. The temperature adjustment system of the present invention can promote the leaching of volatile organic compounds, which are the target of purification, from the aquifer while maintaining the temperature of the aquifer at an appropriate temperature for microbial activity, thereby achieving efficient soil purification. The temperature adjustment system preferably includes a purification device that purifies contaminants in the pumped groundwater, and a purification agent storage tank for adding a purification agent to the groundwater injected near the boundary. The purification agent supplied from the purification agent storage tank can proliferate and activate microorganisms that promote the decomposition of the volatile organic compounds to be purified, thereby facilitating soil purification. In order to solve the above problems, the soil remediation system of the present invention is a soil remediation system equipped with the above temperature adjustment system, and further equipped with an electrode tube as the heating means. In the soil purification system of the present invention, the soil is heated by the passage of electricity from the electrode tubes. When the passage of electricity is stopped, the soil temperature stops rising, making it easy to control the soil temperature. This makes it easier to control soil temperature. In order to solve the above problems, the temperature control method of the present invention is a temperature control method for soil remediation using a heating means. The temperature control method includes a temperature measurement step of measuring the temperature near the boundary between an aquifer and a low-permeability layer, a pumping step of pumping groundwater from the boundary, a purification step of purifying contaminants in the pumped groundwater, a purification agent supplying step of adding a purification agent to the groundwater from which the contaminants have been purified, and a water injection step of injecting the groundwater to which the purification agent has been added near the boundary. The soil remediation method also includes a cooling step of cooling the groundwater that has been subjected to the purification step or the groundwater that has been subjected to the purification agent supplying step. The cooling step cools the groundwater when the temperature measured by the temperature measurement step is equal to or higher than a predetermined threshold value. In the temperature adjustment method of the present invention, the aquifer temperature can be maintained at an appropriate temperature for microbial activity while promoting the leaching of the volatile organic compounds to be purified from the aquifer by continuing to heat the aquifer as long as possible, thereby achieving efficient soil purification. In order to solve the above problems, the soil remediation method of the present invention includes a heating step of heating soil with an electrode tube, a temperature measurement step of measuring the temperature near the boundary between an aquifer and a low-permeability layer, a pumping step of pumping groundwater from the boundary, a purification step of purifying contaminants in the pumped groundwater, a purification agent supplying step of adding a purification agent to the groundwater from which the contaminants have been purified, a water injection step of injecting the groundwater to which the purification agent has been added near the boundary, and a cooling step of cooling the groundwater from which the contaminants have been purified by the purification step or the groundwater to which the purification agent has been added by the purification agent supplying step. The cooling step cools the groundwater when the temperature measured by the temperature measurement step is equal to or higher than a predetermined threshold value. In the soil remediation method of the present invention, contaminants in the soil and groundwater can be efficiently purified by heating with the electrode tubes, and the temperature of the aquifer can be kept at an appropriate temperature for microbial activity, thereby realizing efficient soil remediation. Effect of the Invention

[0006] According to the temperature adjustment system, soil remediation system, temperature adjustment method, and soil remediation method of the present invention, efficient soil remediation can be achieved in soil remediation using a heating means. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic vertical cross-sectional view showing the state of soil and the system configuration to which a temperature adjustment system, a soil remediation system, a temperature adjustment method, and a soil remediation method according to a first embodiment of the present invention are applied. [Diagram 2] 1 is a schematic plan view showing the arrangement of electrode pipes, temperature measurement wells, pumping wells, and water injection wells in a soil purification system according to a first embodiment of the present invention. [Diagram 3] FIG. 5 is a schematic vertical cross-sectional view showing the state of soil to which a soil purification system according to a second embodiment of the present invention is applied, and the system configuration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The temperature control system, the soil purification system, the temperature control method, and the soil purification method of the present invention will be described in detail below with reference to the drawings as appropriate. In each embodiment, common parts are given common reference numerals, and duplicated descriptions will be omitted. (First embodiment) Fig. 1 is a schematic vertical cross-sectional view showing the state of soil and the system configuration to which the temperature adjustment system, soil purification system, temperature adjustment method, and soil purification method according to the first embodiment are applied. Fig. 2 is a schematic plan view showing the arrangement of electrode pipes, temperature measurement wells, pumping wells, and water injection wells in the soil purification system. As shown in Figure 1, the soil to which the soil purification system 1 of this embodiment is applied includes an unsaturated zone V that is continuous below the soil surface (ground surface) GL, an aquifer W that is continuous below the unsaturated zone V, and an aquifer A that is continuous below the aquifer W.

[0009] The soil remediation system 1 is a system for remediating soil, and includes an electrode tube 2 as a heating means. The soil remediation system 1 further includes a temperature adjustment system 10 that can adjust the temperature of the soil heated by the electrode tube 2. The electrode tube 2 is installed in the soil within the area to be purified, and includes a power supply unit 2a installed above ground. The electrode tube 2 is a device that heats the soil by passing an electric current through it, and is made of a steel pipe. Note that the electrode tube 2 can be made of various materials as long as they are conductive. A three-phase AC voltage is applied to the electrode tube 2 from the power supply unit 2a. As shown in FIG. 2, it is preferable to place a plurality of electrode tubes 2 in the soil so as to be located at the vertices of a plurality of triangles in a plan view. That is, three or more electrode tubes 2 must be installed. When a three-phase AC voltage is applied to each of the electrode tubes 2 thus placed, a current flows between the adjacent electrode tubes 2, 2, and as a result, Joule heat is generated in the soil between the electrode tubes 2, 2, and the soil is heated. The four triangles shown in FIG. 2 are approximately equilateral triangles with a side length of approximately 3.5 m, and an electrode tube 2 is placed at each vertex of the triangle. The arrangement of the electrode tubes 2 is not limited to the arrangement of an approximately equilateral triangle. A detailed explanation of FIG. 2 will be given later.

[0010] As shown in FIG. 1, the electrode pipe 2 is arranged from the soil surface GL to the aquifer W and the aquifer A. The resistivity of the aquifer A, which contains a lot of clay and silt, is smaller than that of the aquifer W, which contains a lot of sand and gravel, so that a large amount of current tends to flow through the aquifer A. Therefore, the aquifer A, which is particularly prone to retaining volatile organic compounds, can be heated to a higher temperature than the aquifer W, and the volatile organic compounds can be actively leached from the aquifer A. In order to heat only the aquifer A, it is desirable to insulate the electrodes between the soil surface GL and the aquifer W. It is desirable to raise the temperature of the aquifer A as high as possible so that it approaches the ideal temperature of about 80°C by the electrode pipe 2. The high temperature of the aquifer A allows volatile organic compounds with a high boiling point, such as trichloroethylene (TCE), to be suitably leached. It has been confirmed that a high leaching effect can be obtained even if the temperature of the aquifer A is about 45°C.

[0011] The temperature adjustment system 10 comprises a temperature measurement well 11 as a temperature measurement means, a pumping well 12, a pump 13, a purification device 13a, a cooling device 14, and a water injection well 15. These wells are arranged from the soil surface GL to both the aquifer W and the aquifer-impermeable layer A. In this way, the pumping well 12 and the water injection well 15 are located at the depth of the aquifer A and have openings (screen section 12a and screen section 15a), making it possible to efficiently leach from the soil by heating. In other words, even at a great depth, pollutants can be efficiently leached out over a short distance. In Fig. 1, the white arrows indicate the circulation path of groundwater. In this embodiment, a water conveyance pipe 16 is installed from the bottom of the pumping well 12 to the bottom of the water injection well 15 via the ground. A pump 13 and a cooling device 14 are installed in the aboveground part of the water conveyance pipe 16. The temperature measurement well 11 is a well that measures the temperature of the aquifer W, and is equipped with a temperature sensor (not shown) that is placed near the boundary between the aquifer W and the impermeable layer A as a temperature measurement means. The reason for placing the temperature sensor near the boundary between the aquifer W and the impermeable layer A is that the temperature is highest near the boundary, and the temperature of the aquifer W above that gradually decreases. The depth of the temperature sensor must be in the aquifer W near the impermeable layer A. The temperature measurement well 11 may be configured to measure the temperature of the impermeable layer A as well. The pumping well 12 is a well that pumps groundwater mainly from near the boundary between the aquifer W and the impermeable layer A. The pumping well 12 has a screen portion 12a for taking groundwater into the pumping well 12. The screen portion 12a is provided from the lower part of the pumping well 12 to near the boundary between the aquifer W and the impermeable layer A. This enables the pumping well 12 to efficiently leach volatile organic compounds from the impermeable layer A by heating through the screen portion 12a.

[0012] The pump 13 is a suction pump that draws groundwater from the pumping well 12 and discharges it to the downstream purification device 13a. Since the pump 13 is disposed above ground, it is not easily affected by the three-phase AC voltage of the electrode tube 2. The type of pump 13 is not particularly limited, but it is preferable that the pump 13 is one that can prevent air from being mixed in during the pumping process. This is because it is preferable that as little oxygen as possible be dissolved in the groundwater when it is returned to the ground through the water injection well 15 after pumping. An example of a pump 13 that can prevent air from being mixed in during the pumping process is a tube pump. The purification device 13a is a device that purifies contaminants in groundwater pumped from the pumping well 12. The purification device 13a is configured to gasify and separate the volatile organic compounds to be purified from the pumped groundwater using an aeration tank or a gas-liquid separator, and then adsorb the volatile organic compounds with activated carbon or decompose them by combustion. The purification device 13a is preferably configured to treat the aerated groundwater using a packed tower, activated carbon adsorption device, or the like. Note that purification is generally performed using an "aeration process" in which air is aerated and the gasified VOCs are captured with activated carbon, but since oxygen dissolves in the pumped groundwater during aeration, it is also possible to aerate with nitrogen gas. The cooling device 14 is a device that cools the groundwater from which contaminants have been purified by the purification device 13a to a predetermined temperature, and is disposed downstream of the purification device 13a. The cooling device 14 is activated when the temperature near the boundary between the aquifer W and the aquifer-impermeable layer A measured by the temperature measurement well 11 exceeds a predetermined threshold, and cools the groundwater pumped by the pumping well 12 to a predetermined temperature. The predetermined threshold is an appropriate temperature at which microorganisms in the aquifer W are active, and for example, when the volatile organic compounds to be purified are tetrachloroethylene (PCE) or trichloroethylene (TCE), it is preferable to set the predetermined threshold to less than 35°C at which Dehalococcoides bacteria are active. The predetermined temperature set in the cooling device 14 is set to a temperature lower than the above-mentioned predetermined threshold. This is because the groundwater cooled by the cooling device 14 needs to be at a temperature suitable for microbial activity when it is injected into the aquifer W through the water injection well 15 and then mixed with the groundwater in the aquifer W. Therefore, on the assumption that it will mix with the groundwater in the aquifer W, the temperature is set lower than the above-mentioned specified threshold value. The cooling device 14 may be a chiller, an air-cooled heat exchanger, a water-cooled heat exchanger, or the like.

[0013] The water injection well 15 is a well that injects groundwater near the boundary between the aquifer W and the impermeable layer A. The water injection well 15 has a screen portion 15a for injecting groundwater. The screen portion 15a is provided from the bottom of the water injection well 15 to the boundary between the aquifer W and the impermeable layer A. The water in the water injection well 15 is mainly supplied to the aquifer W near the boundary through the upper screen portion 15a, so that the temperature of the aquifer W can be prevented from rising above a threshold. This allows the activity of microorganisms to be maintained. The screen portion 15a that opens in the impermeable layer A functions as an intake port for taking in volatile organic compounds to be purified in the impermeable layer A when the water injection well 15 is used as the pumping well 12, as described later. This allows the leaching of volatile organic compounds from the impermeable layer A by heating to be efficiently performed through the screen portion 15a when the water injection well 15 is used as the pumping well 12.

[0014] Next, a soil remediation method using the soil remediation system 1 will be described with reference to Fig. 2. In Fig. 2, the arrow indicated by the symbol G indicates the flow direction of groundwater. Furthermore, the hatched circle (the apex of the triangle) indicates the electrode tube 2, the single circle indicates the temperature measurement well 11, and the double circle indicates the pumping well 12 or the water injection well 15. The temperature measurement well 11 is provided in each of the triangular regions T1 to T4 defined by the electrode tube 2. In the regions T1 to T4, the temperature measurement well 11 is located at or near the center of the triangle, and is disposed at the position where the temperature effect of the electrode tube 2 appears latest. Similarly, the pumping well 12 and the water injection well 15 are also disposed at or near the center of the triangle for the same reason. FIG. 3 shows an example in which groundwater is pumped from the pumping well 12 in region T4 and injected into the water injection well 15 in region T1, and also groundwater is pumped from the pumping well 12 in region T2 and injected into the water injection well 15 in region T3.

[0015] Since the pumping wells 12 and the water injection wells 15 have the same structure, they are adapted to change the roles of pumping and water injection after installation. In this case, the wells can be freely combined, for example, by setting three pumping wells 12 and one water injection well 15. It is also possible to change the pumping wells 12 and water injection wells 15 during soil purification. In this case, it can be easily accommodated by changing the suction and discharge directions of the pump 13.

[0016] The soil purification method includes a heating step, a temperature measurement step, a water pumping step, a purification step, a cooling step, and a water injection step. Among these steps, the temperature measurement step, the water pumping step, the cooling step, and the water injection step correspond to the temperature adjustment method in soil purification using a heating means. The heating process is a process of heating the soil with the electrode tube 2. The temperature measurement process is a process of measuring the temperature of the aquifer W. The pumping process is a process of pumping groundwater from the aquifer W when the measured temperature is equal to or higher than a predetermined threshold. The cooling process is a process of cooling the pumped groundwater. The water injection process is a process of injecting the cooled groundwater into the aquifer W. In the heating process, a three-phase AC voltage is applied to each electrode tube 2 to heat each of the regions T1 to T4. Since the resistivity of the aquifer A is smaller than that of the aquifer W, the aquifer A is mainly heated, and the leaching of volatile organic compounds contained in the aquifer A in each of the regions T1 to T4 is promoted. In the temperature measurement step, the heating state of the regions T1 to T4 is measured. The heating state is determined by measuring the temperature near the boundary between the aquifer W and the aquifer impermeable layer A in each of the regions T1 to T4 using a temperature measurement well 11. In the pumping step, groundwater near the boundary between the aquifer W and the aquifer impermeable layer A is pumped by a pumping well 12. In this case, the screen portion 12a of the pumping well 12 is provided up to the position of the aquifer impermeable layer A, so that contaminants in the aquifer A can be directly taken in horizontally. In the purification process, the purification device 13a purifies contaminants in the groundwater pumped by the pumping well 12. In the cooling process, the groundwater purified in the purification process is cooled by the cooling device 14. In the cooling process, the groundwater is cooled when the measured temperature is equal to or higher than a predetermined threshold (e.g., 35°C or higher). For example, when either or both of the regions T4 and T1 are equal to or higher than a predetermined threshold, the cooling device 14 of this system is driven to cool the groundwater. In the water injection process, groundwater or cooled groundwater is injected into the aquifer W, for example, through the water injection well 15 in area T1. Injecting cooled groundwater can eliminate the temperature gradient in the aquifer W and equalize the temperature of the aquifer W. In particular, the aquifer W (near the boundary) where the temperature is relatively high in the portion in contact with the aquifer A can be suitably cooled. In addition, because the screen portion 15a of the water injection well 15 is provided up to the position of the aquifer A, some of the groundwater can also be injected into the aquifer A.

[0017] The temperature adjustment system of this embodiment described above can maintain the temperature of the aquifer W at an appropriate temperature at which microorganisms are active while promoting the leaching of volatile organic compounds from the low-permeability layer A. Therefore, efficient soil purification can be achieved. Furthermore, in the soil purification system 1 of this embodiment, the soil is heated by the passage of electricity from the electrode tubes 2. When the passage of electricity is stopped, the soil temperature stops rising, making it easy to control the soil temperature. In addition, in the temperature adjustment method of this embodiment, the temperature of the aquifer W can be maintained at an appropriate temperature at which microorganisms are active, while promoting the leaching of volatile organic compounds from the aquifer A by continuing to heat the aquifer A as long as possible. Therefore, efficient soil purification can be achieved. Furthermore, in the soil remediation method of this embodiment, contaminants in the soil and groundwater can be efficiently purified by heating with the electrode tube 2, and the temperature of the aquifer W can be kept at an appropriate temperature at which microorganisms are active, thereby realizing efficient soil remediation.

[0018] Second embodiment A soil purification system 1A according to a second embodiment will be described with reference to Fig. 3. Fig. 3 is a schematic vertical cross-sectional view showing the state of soil to which the soil purification system is applied and the system configuration. This embodiment differs from the first embodiment in that a soil purification system 1A includes a purification agent storage tank 20, and other configurations are similar to those of the first embodiment. A purification agent is stored in the purification agent storage tank 20. The purification agent contains components that grow and activate microorganisms that promote the decomposition of volatile organic compounds, which are the targets of purification. The purification agent storage tank 20 is connected to the water conveyance pipe 16 via a water injection pipe 22. A delivery pump 21 is installed in the water injection pipe 22 to deliver the purification agent from the purification agent storage tank 20 to the water conveyance pipe 16. The purification agent delivered to the water conveyance pipe 16 via the delivery pump 21 is supplied to the aquifer W via the water injection well 15.

[0019] The purifying agent is not particularly limited as long as it can promote the decomposition of volatile organic compounds to be purified by microorganisms, and examples of the purifying agent include nutrients such as nitrogen and phosphorus necessary for the proliferation and activity of microorganisms, various organic substances that serve as hydrogen donors (sugars, organic acids (fatty acids), proteins, amino acids, etc.), decomposing microorganisms themselves, and mixtures thereof. When treating volatile organic compounds (benzene, oils (hydrocarbon compounds), etc.) that are biodegraded under aerobic conditions, it is preferable to supply inorganic nutrients such as nitrogen and phosphorus as a purifying agent and also supply air (oxygen) in order to promote the activity of aerobic microorganisms. When treating volatile organic chlorine compounds (chlorinated ethylenes), it is preferable to use a purifying agent that can promote the activity of anaerobic dechlorinating bacteria. Furthermore, when anaerobic dechlorinating bacteria are contained in the purification agent, bacteria of the genus Dehalococcoides are preferred, and either or both of Dehalococcoides sp. UCH007 strain (NITEAP-1471, hereinafter referred to as UCH007 strain), Sulfurospirillum sp. UCH001 strain (NITEAP-1469, hereinafter referred to as UCH001 strain), and Sulfurospirillum sp. UCH003 strain (NITEAP-1470) can be suitably used.

[0020] The soil purification method includes a heating step, a temperature measurement step, a water pumping step, a purification step, a cooling step, a purification agent supplying step, and a water injection step. Among these steps, the temperature measurement step, the water pumping step, the purification step, the cooling step, the purification agent supplying step, and the water injection step correspond to the temperature adjustment method in soil purification using a heating means. Each step except for the purification agent supplying step is the same as in the first embodiment, so detailed explanations will be omitted. The purification agent supplying step is a step for adding a purification agent to the groundwater from which contaminants have been purified. In the purification agent supplying step, as described above, a purification agent capable of promoting the decomposition by microorganisms of the volatile organic compounds to be purified is added to the groundwater from which contaminants have been purified.

[0021] According to the soil purification system 1A of the present embodiment described above, in addition to the effects described in the first embodiment, by supplying a purification agent from the purification agent storage tank 20, microorganisms that promote the decomposition of the volatile organic compounds to be purified can be multiplied and activated, thereby realizing a purification method that combines the leaching of the volatile organic compounds to be purified by heating with the decomposition by microorganisms, thereby facilitating soil purification. In addition, by continuing to heat the aquifer A as long as possible, it is possible to promote the leaching of the volatile organic compounds to be purified from the aquifer A, while maintaining the temperature of the aquifer W at an appropriate temperature for the microorganisms to become active. Therefore, efficient soil purification can be achieved. Furthermore, in the soil purification method, contaminants in the soil and groundwater can be purified efficiently by heating with the electrode tube 2, and the temperature of the aquifer W can be maintained at an appropriate temperature at which microorganisms are active. Therefore, efficient soil purification can be achieved.

[0022] Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and each of the above-described components can be appropriately modified without departing from the spirit of the present invention. For example, in the temperature measurement well 11, a temperature sensor is installed near the boundary between the aquifer W and the impermeable layer A, but this is not limited to this, and a temperature sensor may also be installed near the boundary between the aquifer W and the impermeable layer A in the pumping well 12 or the water injection well 15. In addition, in the second embodiment, an example is shown in which the cooling device 14 is arranged downstream of the purification device 13a, but this is not limited to this, and the cooling device 14 may be arranged downstream of the portion to which the water injection pipe 22 of the purification agent storage tank 20 is connected. [Explanation of symbols]

[0023] 1. Soil purification system 2 electrode tube 12 Pumping well 13. Pump 14 Cooling device 15 Water injection well 20 Purification agent storage tank A Impermeable layer W aquifer

Claims

1. A temperature control system for soil remediation using a heating means, comprising: a temperature measuring means for measuring a temperature near the boundary between the aquifer and the impermeable layer; A pumping well that pumps groundwater from near the boundary; A cooling device for cooling the groundwater pumped by the pumping well; A temperature adjustment system comprising: an injection well that injects groundwater cooled by the cooling device into the vicinity of the boundary.

2. A purification device for purifying contaminants in the pumped groundwater; 2. The temperature adjustment system according to claim 1, further comprising a purification agent storage tank for adding a purification agent to the groundwater injected near the boundary.

3. A soil remediation system comprising the temperature adjustment system according to claim 1 or 2, The soil remediation system is characterized in that the heating means comprises an electrode tube.

4. A temperature control method for soil remediation using a heating means, comprising: a temperature measuring step of measuring a temperature near the boundary between the aquifer and the impermeable layer; A pumping step of pumping groundwater from near the boundary; a purification process for purifying contaminants in the pumped groundwater; a purification agent supply step for adding a purification agent to the groundwater from which the contaminants have been purified; and a water injection step of injecting groundwater containing a purification agent into the vicinity of the boundary, A cooling step of cooling the groundwater that has been subjected to the purification step or the purification agent supply step, The temperature adjustment method, wherein the cooling step cools groundwater when the temperature measured in the temperature measurement step is equal to or higher than a predetermined threshold value.

5. a heating step of heating the soil with an electrode tube; a temperature measuring step of measuring a temperature near the boundary between the aquifer and the impermeable layer; A pumping step of pumping groundwater from near the boundary; a purification process for purifying contaminants in the pumped groundwater; a purification agent supply step for adding a purification agent to the groundwater from which the contaminants have been purified; and a water injection step of injecting groundwater containing a purification agent into the vicinity of the boundary, A cooling step of cooling the groundwater that has been subjected to the purification step or the purification agent supply step, The soil remediation method, wherein the cooling step comprises cooling the groundwater when the temperature measured in the temperature measuring step is equal to or higher than a predetermined threshold value.

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