JP2022125865A - In-situ purification system for contaminated soil and in-situ purification method for contaminated soil - Google Patents

Abstract

A contaminated soil in-situ cleaning system and a contaminated soil in-situ cleaning method capable of increasing heating efficiency.
One or more heating wells (10) for heat-treating at least a part of a treatment target area (A1) where contaminated soil contaminated with a contaminant exists, one or more suction wells 20 for suctioning at least a portion of the contaminant-laden fluid produced by One or more water injection wells 30 for injecting water into the treatment target area A1.
[Selection drawing] Fig. 1

Description

The present invention relates to an in-situ cleaning system for contaminated soil and an in-situ cleaning method for contaminated soil.

As a method for remediation of contaminated soil contaminated with volatile organic compounds (VOC) and the like, a method of excavating and removing (excavation removal method) is known.
However, in the excavation removal method, a large amount of contaminated soil had to be carried out and transported, resulting in enormous costs.

In order to address such problems, for example, Patent Document 1 discloses a source of contaminated soil in which heat is applied to an area to be treated that contains pollutants, part of the pollutants is vaporized and sucked in, and removed from the area to be treated. Location cleansing methods have been proposed. According to the invention of Patent Document 1, in situ heating and steam extraction are intended to increase the efficiency of contaminant removal.

Japanese Patent No. 4509558

However, in the technique of Patent Literature 1, groundwater and heated steam are sucked when vaporized contaminants are sucked, so the water head in the treatment target region is lowered, and groundwater and the like flow in from the outside. As a result, the underground temperature of the area to be treated is significantly lowered, and the heating efficiency is lowered.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an in-situ cleaning system for contaminated soil and an in-situ cleaning method for contaminated soil that can improve heating efficiency.

In order to solve the above problems, the present invention has the following aspects.
[1] one or more heating wells that heat-treat at least part of a treatment target area where contaminated soil contaminated with a contaminant exists;
one or more suction wells located within the region to be treated for suctioning at least a portion of the contaminant-laden fluid resulting from the heat treatment;
one or more water injection wells located in or around the area to be treated and having a higher temperature than groundwater flowing into the area to be treated and injecting water into the area to be treated. Position purification system.
[2] The in-situ remediation system for contaminated soil according to [1], which has a gas-liquid separator connected to the suction well.
[3] The in-situ remediation system for contaminated soil according to [1] or [2], which has a heat exchanger connected to the suction well.
[4] The in-situ purification system for contaminated soil according to [3], wherein the heat obtained by the heat exchanger is used as a heat source for the water injected from the water injection well.

[5] a heating step of heat-treating at least part of a treatment target area where contaminated soil contaminated with a contaminant exists;
a suction step of sucking at least part of the fluid containing the contaminants generated by the heat treatment;
and a water injection step of injecting water having a higher temperature than groundwater flowing into the treatment target area into or around the treatment target area.
[6] The method for in-situ remediation of contaminated soil according to [5], wherein the heating temperature in the heating step is 60°C or higher.
[7] The method for in-situ remediation of contaminated soil according to [5] or [6], wherein the contaminant is one or more selected from volatile organic compounds, oil, mercury, polychlorinated biphenyls and dioxins.
[8] The method for in-situ remediation of contaminated soil according to any one of [5] to [7], further comprising a heat exchange step of obtaining heat from the fluid after the suction step.
[9] The in-situ purification method for contaminated soil according to [8], wherein the heat obtained in the heat exchange step is used as a heat source for the water injected in the water pouring step.

According to the contaminated soil in-situ remediation system and the contaminated soil in-situ remediation method of the present invention, the heating efficiency can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view schematically showing the configuration of an in-situ purification system for contaminated soil according to a first embodiment of the present invention; 1 is a plan view schematically showing the arrangement of wells in the in-situ purification system for contaminated soil according to the first embodiment of the present invention; FIG. FIG. 2 is a cross-sectional view schematically showing the configuration of an in-situ purification system for contaminated soil according to a second embodiment of the present invention;

An in-situ purification system for contaminated soil of the present invention (hereinafter also referred to as an "in-situ purification system") has a heating well, a suction well, and an injection well. An in situ remediation system is a system that heats a treatment target area where contaminated soil exists to volatilize contaminants and remediate the soil. Volatilized contaminants are sucked by suction wells. At this time, the water level of groundwater is lowered in a part of the treatment target area. For this reason, groundwater with a low water temperature (for example, 10° C.) flows in from the outside of the area to be treated. The in-situ purification system injects hot water (eg, 25° C.) to replace the incoming groundwater to increase the heating efficiency of the heating well.
A first embodiment of the in-situ purification system of the present invention will be described below with reference to the drawings.

[First embodiment]
This embodiment is an in-situ purification system when there is a large difference between the depth of the area to be treated and the depth of the impermeable layer (stratum into which groundwater does not easily permeate). In the present embodiment, groundwater flows in from below the processing target area in the depth direction and from the horizontal outer periphery of the processing target area. For this reason, in the in-situ purification system of the present embodiment, hot water is injected in the depth direction downward of the processing target region and the horizontal outer peripheral portion of the processing target region.

≪In-situ purification system for contaminated soil≫
The in-situ purification system 1 of FIG. , has The suction well 20 and the heat exchanger 40 are connected by a pipe L1. The heat exchanger 40 and the gas-liquid separator 50 are connected by a pipe L2. The gas-liquid separation device 50 and the exhaust gas treatment device 60 are connected by a pipe L3. A pipe L4 is connected to the exhaust gas treatment device 60 . The gas-liquid separation device 50 and the waste liquid treatment device 70 are connected by a pipe L5. A pipe L<b>6 is connected to the waste liquid treatment device 70 .
The arrows in the figure indicate the direction of movement of fluid such as thermal energy and water.

In this embodiment, as shown in FIG. 1, a processing target area A1 that requires soil purification is partitioned by impermeable walls W in the ground. Therefore, it is possible to prevent the inflow of groundwater from the horizontal peripheral portion of the processing target area A1. Examples of the impermeable wall W include a continuous wall made of steel sheet piles, a concrete wall, and a water impermeable wall made of water glass. The impermeable wall W is, for example, driven into the ground in the depth direction, with its upper end reaching the ground surface and its lower end reaching a position deeper than the lower end of the water injection well 30 . A groundwater level surface L is formed in the processing target area A1.

The heating well 10 is for heating contaminated soil contaminated with contaminants. A plurality of heating wells 10 are provided in the processing target area A1. The heating well 10 is arranged to extend in the depth direction downward from the ground surface.
The heating well 10 may be, for example, a cylindrical body having a heating tool. Examples of the heating tool include a heater that generates heat by itself, an electrode that heats the surrounding soil when energized, and high-temperature steam. The tube may be provided with a plurality of small holes through which hot water vapor can be injected.

Suction well 20 is for sucking at least a portion of the contaminant-laden fluid produced by heat treatment by heating well 10 to remove contaminants from the soil. A plurality of suction wells 20 are provided in the processing target area A1. The suction wells 20 are arranged to extend depthwise downward from the ground surface.
The suction well 20 may be, for example, a tubular body having a suction tool. Suction devices include, for example, devices that enable negative pressure, such as vacuum pumps. A vacuum pump, a blower, and a submersible pump may be combined to create a negative pressure and be used as a suction tool.

The water injection well 30 is for injecting water (hot water) having a higher temperature than the groundwater flowing into the treatment target area A1 into the treatment target area A1. A plurality of water injection wells 30 are provided within the treatment target area A1. The water injection well 30 is arranged so as to extend downward from the ground surface in the depth direction.
As the water injection well 30, for example, a tubular body or the like that can inject hot water into the processing target area A1 can be used. It is preferable that the tubular body has a heat insulating property. The tubular body may be provided with a plurality of small holes through which hot water can pass. The tubular body may be provided with a heating tool capable of heating the water flowing therein.

As shown in FIG. 2, a plurality of heating wells 10 are provided. The plurality of heating wells 10 are arranged in a straight line in a plan view, and form a horizontal peripheral portion of the processing target area A1. In a plan view, a plurality of heating wells 10 are provided in a zigzag arrangement in the horizontal inner region of the processing target region A1. By staggering the plurality of heating wells 10, the contaminated soil inside the processing target area A1 can be uniformly heated. The distance d1 between the heating wells 10 in plan view is preferably 1 to 6 m, more preferably 2 to 4 m, for example. If the interval d1 is equal to or greater than the lower limit, the number of heating wells 10 can be reduced. When the interval d1 is equal to or less than the above upper limit value, the efficiency of the heat treatment can be enhanced, and the removal efficiency of contaminants can be further enhanced.

A plurality of suction wells 20 are provided. In plan view, a plurality of suction wells 20 are provided in a zigzag arrangement in the horizontal inner region of the processing target region A1. By staggering the plurality of suction wells 20, the fluid containing contaminants inside the processing target area A1 can be uniformly sucked. The distance d2 between the suction wells 20 in plan view is preferably 2 to 12 m, more preferably 3 to 8 m, for example. If the interval d2 is equal to or greater than the lower limit, the number of suction wells 20 can be reduced. When the interval d2 is equal to or less than the above upper limit value, the contaminants can be sufficiently sucked, and the removal efficiency of the contaminants can be further enhanced.

A plurality of water injection wells 30 are provided. A plurality of water injection wells 30 are arranged along the horizontal periphery of the processing target area A1 so as to line up in a straight line in a plan view. In this embodiment, the multiple water injection wells 30 are arranged on the same straight line as the multiple heating wells 10 lined up. In a plan view, a plurality of water injection wells 30 are provided in a zigzag arrangement in the horizontal inner region of the processing target region A1. By staggering the plurality of water injection wells 30, hot water can be uniformly injected into the treatment target area A1. The distance d3 between the water injection wells 30 in plan view is preferably 1 to 6 m, more preferably 2 to 4 m, for example. When the interval d3 is equal to or greater than the above lower limit, the number of water injection wells 30 can be reduced. Heating efficiency is improved more as the space|interval d3 is below the said upper limit.

The distance d4 in plan view between the water injection well 30 and the heating well 10 adjacent to the water injection well 30 is preferably 0.5 to 3 m, more preferably 1 to 2 m, for example. If the interval d4 is equal to or greater than the above lower limit, the number of water injection wells 30 can be reduced. Heating efficiency is improved more as the space|interval d4 is below the said upper limit.
The distance d5 between the injection well 30 and the suction well 20 adjacent to the injection well 30 in plan view is, for example, preferably 0.5 to 3 m, more preferably 1 to 2 m. When the interval d5 is equal to or greater than the above lower limit, the number of water injection wells 30 can be reduced. Heating efficiency is improved more as the space|interval d5 is below the said upper limit.

Heat exchanger 40 is a device that cools the hot fluid drawn by suction well 20 .
The heat exchanger 40 can cool the high-temperature fluid sucked by the suction well 20. Examples of the heat exchanger 40 include a plate heat exchanger, a coil heat exchanger, a shell and tube heat exchanger, and the like. is mentioned.

The gas-liquid separator 50 is a device that separates the fluid containing contaminants sucked by the suction well 20 into gas and liquid.
As the gas-liquid separation device 50, it is sufficient to separate a fluid containing contaminants into a gas and a liquid, and examples thereof include a condenser having a cooling function.

The exhaust gas treatment device 60 is a device that removes pollutants from the pollutant-containing gas separated by the gas-liquid separation device 50 .
Examples of the exhaust gas treatment device 60 include a pressure vessel having an adsorption tank filled with an adsorbent, and a thermal decomposition device capable of thermally decomposing an internal gas by heating at a high temperature. The exhaust gas treatment device 60 may be used singly or in combination of two or more.

The waste liquid treatment device 70 is a device for removing contaminants from the contaminant-containing liquid separated by the gas-liquid separation device 50 .
A known water treatment device can be applied as the drainage treatment device 70 . Water treatment equipment includes, for example, a filtration device having an adsorption tank filled with an adsorbent, an adsorption device having an adsorption tank filled with an adsorbent, a membrane separation device, a pressure flotation device, a coagulation sedimentation device, an aeration device, and the like. is mentioned. The waste liquid treatment device 70 may be used singly or in combination of two or more.

As the piping L1, for example, piping made of metal or resin can be used.
The pipes L2 to L6 include pipes similar to the pipe L1. The materials of the pipes L1 to L6 may be different from each other or may be the same.

≪In-situ purification method for contaminated soil≫
The in-situ purification method for contaminated soil of the present invention (hereinafter also referred to simply as the "in-situ purification method") has a heating step, a suction step, and a water injection step.
The in-situ cleaning method of the present embodiment will be described with an in-situ cleaning method using the in-situ cleaning system 1 as an example.

First, in the heating well 10, at least part of the processing target area A1 is subjected to heat treatment (heating step).
Since the in-situ purification method includes the heating step, it is possible to desorb the contaminants in the processing target area A1 from the contaminated soil or vaporize and recover the contaminants from the contaminated groundwater.
In the heating step, at least a part of the processing target area A1 may be heat-treated, but from the viewpoint of increasing the efficiency of removing contaminants, it is preferable to heat-treat as wide a range of the processing target area A1 as possible. It is more preferable to heat-treat the entire region A1.

Contaminants include, for example, volatile organic compounds (VOC), oil, mercury, polychlorinated biphenyls (PCB), dioxins, and the like.
VOCs include, for example, benzene, toluene, halogenated hydrocarbons (eg, trichlorethylene, etc.), and the like.
Examples of the oil include hydrocarbons having 5 to 44 carbon atoms. Hydrocarbons having 5 to 18 carbon atoms can be recovered mainly as gases. Even hydrocarbons with 19 or more carbon atoms can be recovered as liquids by reducing their viscosity. These hydrocarbons may be saturated hydrocarbons or unsaturated hydrocarbons. These hydrocarbons may be linear, branched, or cyclic. Specific examples of these hydrocarbons include n-pentane, isopentane, n-hexane, cyclohexane and the like.
Mercury includes, for example, metallic mercury, inorganic mercury, and organic mercury. Examples of inorganic mercury include mercury oxide, mercury sulfide, mercury chloride (Hg ₂ Cl ₂ , HgCl ₂ ), mercury nitrate, and the like. Organic mercury includes, for example, alkylmercury (eg, methylmercury, ethylmercury), phenylmercury (eg, phenylmercury acetate), and the like.

Examples of PCB include 3,3′,4,4′-tetrachlorobiphenyl, 3,4,4′,5-tetrachlorobiphenyl, 3,3′,4,4′,5-pentachlorobiphenyl, 3 ,3′,4,4′,5,5′-hexachlorobiphenyl, 2,3,3′,4,4′-pentachlorobiphenyl, 2,3,3′,4,4′,5-hexachlorobiphenyl, 2,3,3',4,4',5,5'-heptachlorobiphenyl and the like.
Examples of dioxins include 2,3,7,8-tetrachloroparadioxin and 2,3,4,7,8-pentachlorodibenzofuran.

The in-situ purification method of this embodiment is a so-called in-situ thermal desorption method. Examples of the heating method of the in-situ thermal desorption method include an electric heating heater method, an electric resistance method, and a steam method. As a heating method for the in-situ thermal desorption method, an electric heater type is preferable because the heating temperature is high, the soil can be heated uniformly, and many types of contaminants can be treated.

The heating temperature for heat treatment is preferably 60° C. or higher, more preferably 80° C. or higher, and even more preferably 100° C. or higher. If the heating temperature is equal to or higher than the above lower limit, vaporization and decomposition of contaminants are accelerated, and more contaminants can be removed. Although the upper limit of the heating temperature is preferably as high as possible, it is practically about 350°C.
The heating temperature during the heat treatment can be measured by a monitoring well (not shown) equipped with a thermocouple, a temperature sensor, or the like.

The above-described electric heater type is a method of heating the processing target area A1 at a heating temperature of 100° C. or higher.
By heating the processing target area A1 at a heating temperature of 100 ° C. or higher, the water contained in the soil interstices can be evaporated, the interstices between the soil particles can be expanded, and the desorbed contaminants can be entrained with water vapor. Contaminants can be removed from the soil more efficiently.

Activate suction well 20 . For example, a vacuum pump (not shown) connected to the suction well 20 is operated to make the internal pressure of the suction well 20 negative. A blower (not shown) and a submersible pump (not shown) are then activated to suck the contaminant-laden fluid into the suction well 20 (suction step).
The in-situ purification method can remove contaminants desorbed in the processing target area A1 from the soil by including the suction step.

The internal pressure of the suction well 20 in the suction step is not particularly limited, and may be, for example, 100 kPa or less (atmospheric pressure or less). When the internal pressure of the suction well 20 in the suction step is equal to or less than the above upper limit value, the desorption of contaminants adhering to the soil is promoted, and the contaminants can be removed more efficiently. The lower limit of the internal pressure of the suction well 20 in the suction step is not particularly limited, and is set to 0.1 Pa, for example.

Before the heating process, after the heating process, or simultaneously with the heating process, water (hot water) having a higher temperature than the groundwater flowing into the treatment target area A1 is injected into the treatment target area A1 via the water injection well 30. (water pouring process).
When the fluid containing contaminants is sucked by the suction well 20, the water level L of the groundwater in the treatment target area A1 is lowered, and the groundwater flows from the outside of the impermeable wall W into the treatment target area A1. When groundwater flows into the treatment target area A1, there is concern that the temperature of the treatment target area A1 will drop and the heating efficiency of the heating well 10 will drop. The in-situ purification method can inject hot water into the treatment target area A1 by including the water injection step. Therefore, it is possible to prevent the temperature of the processing target area A1 from decreasing due to the inflow of groundwater from the outside of the impermeable wall W. As a result, the heating efficiency of the heating well 10 can be further enhanced.
In the water injection process, for example, hot water can be injected into the processing target area A1 by a water injection pump (not shown) connected to the water injection well 30 .

The temperature of the water injected in the water injection step should be higher than the temperature of the groundwater flowing into the treatment target area A1. The temperature difference between the water to be injected and the groundwater is, for example, preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher. When the temperature difference between the water to be injected and the groundwater is equal to or higher than the above lower limit, the heating efficiency of the heating well 10 can be further enhanced. The upper limit of the temperature difference between the water to be injected and the groundwater is not particularly limited, and is set to 95° C., for example.
A temperature difference between the water to be injected and the groundwater can be measured by a monitoring well (not shown) equipped with a thermocouple, a temperature sensor, or the like.

The temperature of the water injected in the water injection step is, for example, preferably 20° C. or higher, more preferably 25° C. or higher, and even more preferably 30° C. or higher. When the temperature of the water injected in the water injection step is equal to or higher than the above lower limit, the heating efficiency of the heating well 10 can be further enhanced. From the viewpoint of increasing the heating efficiency of the heating well 10, the higher the temperature of the water injected in the water injection step, the better. The upper limit of the temperature of the water to be injected in the water injection step is, for example, 99°C.

The amount of water to be injected in the water injection step is not particularly limited, and can be adjusted according to the temperature of the inflowing groundwater, the flow velocity of the groundwater, the soil quality (permeability) of the soil of the processing target area A1, and the like.

The water to be injected in the water injection step is preferably water procured from the outside, such as tap water, because the concentration of contaminants must satisfy the underground permeation standards.
It is preferable that the water injected in the water injection step is warmed using the heat obtained in the heat exchange step described later as a heat source. By using the heat obtained in the heat exchange process as a heat source for warming the water to be injected in the water injection process, energy for warming the water can be saved and the environmental load can be reduced.

The fluid containing contaminants sucked in the suction step is supplied to the heat exchanger 40 through the pipe L1 connected to the suction well 20 . In this embodiment, the fluid sucked by the plurality of suction wells 20 is supplied to the heat exchanger 40 . The heat exchanger 40 cools the fluid at a high temperature (for example, 100° C. or higher) to obtain heat (heat exchange process). Since the in-situ purification method of this embodiment includes the heat exchange step, the obtained heat can be used as a heat source for warming the water to be injected in the water injection step. It is preferable to use the heat obtained in the heat exchange process as a heat source for warming the water to be injected in the water injection process, because the energy for warming the water to be injected in the water injection process can be saved and the environmental load can be reduced.
The fluid cooled by the heat exchanger 40 is supplied to the gas-liquid separator 50 via the pipe L2.

The fluid supplied to the gas-liquid separation device 50 is further cooled and separated into gas containing contaminants and liquid containing contaminants (gas-liquid separation step). Since the in-situ purification method of the present embodiment has the gas-liquid separation step, the fluid containing contaminants can be separated into gas and liquid, and the contaminants can be separated and removed more efficiently.
In the gas-liquid separation step, it is preferable to cool the fluid containing contaminants to 40° C. or less. By cooling the fluid containing contaminants to 40° C. or less, the amount of gas to be processed by the exhaust gas treatment device 60 can be reduced, and the removal efficiency of contaminants can be further enhanced.
The gas containing contaminants obtained in the gas-liquid separation step is supplied to the exhaust gas treatment device 60 via the pipe L3.
The liquid containing contaminants obtained in the gas-liquid separation step is supplied to the waste liquid treatment device 70 via the pipe L5.

The pollutant-laden gas supplied to the exhaust gas treatment device 60 contacts the adsorbent. By contacting with the adsorbent, contaminants contained in the gas are adsorbed by the adsorbent, and clean treated gas is obtained (exhaust gas treatment process). The in-situ purification method of the present embodiment can separate and remove contaminants from gas containing contaminants by including the exhaust gas treatment step.
When a thermal decomposition device is employed as the exhaust gas processing device 60, a method (thermal decomposition method) of decomposing pollutants into harmless substances by thermal decomposition may be used as the exhaust gas processing step. When the thermal decomposition method is employed, the heat obtained by the exhaust gas treatment device 60 is used as a heat source for warming the water to be injected in the water injection process via a heat exchanger (not shown) different from the heat exchanger 40. You may

The adsorbent is not particularly limited, and examples thereof include activated carbon such as bamboo charcoal, coconut shell charcoal, powdered activated carbon and granular activated carbon, zeolite, activated alumina and the like. As the adsorbent, activated carbon is preferable from the viewpoint of its excellent ability to adsorb contaminants, and among them, granular activated carbon is more preferable from the viewpoint of easy operation management of the in-situ purification system 1 .

The concentration of contaminants in the treated gas is, for example, preferably below environmental standards, and more preferably below the lower limit of determination.
Contaminant concentrations in the treated gas can be measured, for example, by gas chromatography.

The treated gas obtained in the exhaust gas treatment step is discharged to the outside of the in-situ purification system 1 through the pipe L4.

The contaminant-laden liquid supplied to the wastewater treatment device 70 contacts the adsorbent. By contacting with the adsorbent, contaminants contained in the liquid are adsorbed by the adsorbent, and clear treated water is obtained (waste liquid treatment step). The in-situ purification method of the present embodiment can separate and remove contaminants from a liquid containing contaminants by including the waste liquid treatment step.
The adsorbent in the waste liquid treatment step is the same as the adsorbent in the first exhaust gas treatment step.

From the viewpoint of reducing the environmental load, the concentration of contaminants in the treated water is preferably, for example, below the effluent standard, more preferably below the environmental standard, and even more preferably below the lower limit of determination.
Effluent standards include, for example, 0.1 mg/L when the contaminant is trichlorethylene (TCE).
Environmental standards include, for example, 0.01 mg/L when the contaminant is TCE.
For example, when the contaminant is TCE, the lower limit of determination is preferably 0.005 mg/L, more preferably 0.002 mg/L, and even more preferably 0.001 mg/L.
The concentration of contaminants in treated water can be measured, for example, according to the method described in JIS K0125:2016 when the contaminants are VOCs.

If the contaminant is VOC, the waste liquid treatment device 70 may not be treated with an adsorbent, and the VOC in the liquid may be transferred to the gas phase by aeration, and the VOC may be discharged below the waste water standard. In this case, in the exhaust gas treatment step, it is preferable to reduce the concentration of VOCs in the treated gas to below the environmental standard before discharging it into the atmosphere.

The treated water obtained in the waste liquid treatment step is discharged to the outside of the in-situ purification system 1 through the pipe L7.

According to the in-situ purification system 1 of the present embodiment, since the water injection well 30 is provided, hot water can be injected into the treatment target area A1. Therefore, it is possible to prevent the inflow of groundwater from the outside of the impermeable wall W, and to prevent the temperature of the processing target area A1 from decreasing. As a result, the heating efficiency of the heating well 10 can be further enhanced.
According to the in-situ purification system 1 of the present embodiment, the heat obtained by the heat exchanger 40 can be used as a heat source for warming the water injected in the water injection process. Therefore, the energy for warming the water to be injected in the water injection process can be saved, and the environmental load can be reduced.

[Second embodiment]
In this embodiment, the difference between the depth of the treatment target area and the depth of the impermeable layer is small, the flow velocity of the groundwater around the treatment target area is small, and the impermeable wall is placed on the horizontal outer periphery of the treatment target area. In-situ purification system without In this embodiment, groundwater flows in from the horizontal peripheral portion of the processing target area. For this reason, in the in-situ purification system of the present embodiment, hot water is injected into the horizontal peripheral portion of the area to be treated. At this time, it is preferable to inject hot water from a location near the ground surface of the processing target area to a location near the bottom end of the processing target region in the depth direction.

≪In situ purification system≫
FIG. 3 shows a schematic diagram of an in-situ purification system according to a second embodiment of the present invention. The same reference numerals are given to the same configurations as in the first embodiment, and the description thereof is omitted.

As shown in FIG. 3, the in-situ purification system 2 of this embodiment includes a heating well 10, a suction well 20, an injection well 32, a heat exchanger 40, a gas-liquid separation device 50, and an exhaust gas treatment device 60. and a waste liquid treatment device 70 . The suction well 20 and the heat exchanger 40 are connected by a pipe L1. The heat exchanger 40 and the gas-liquid separator 50 are connected by a pipe L2. The gas-liquid separation device 50 and the exhaust gas treatment device 60 are connected by a pipe L3. A pipe L4 is connected to the exhaust gas treatment device 60 . The gas-liquid separation device 50 and the waste liquid treatment device 70 are connected by a pipe L5. A pipe L<b>6 is connected to the waste liquid treatment device 70 .
The arrows in the figure indicate the direction of movement of fluid such as thermal energy and water.
The in-situ purification system 2 of the present embodiment is different from the in-situ purification system 1 of the first embodiment in that it is applied to an area that does not have an impermeable wall W and that it has a water injection well 32 instead of the water injection well 30. different.

The in-situ purification system 2 of this embodiment does not have a water impermeable wall W around the processing target area A2. Therefore, when the fluid containing contaminants is sucked by the suction well 20, the water level L of the groundwater in the treatment target area A2 is lowered, and the groundwater flows from the periphery of the treatment target area A2. When groundwater flows into the treatment target area A2, there is concern that the temperature of the treatment target area A2 will drop and the heating efficiency of the heating well 10 will drop. Since the in-situ purification system 2 of the present embodiment has the water injection well 32, hot water can be injected into the treatment target area A2. Therefore, it is possible to prevent the temperature of the treatment target area A2 from decreasing due to the inflow of groundwater from the periphery of the treatment target area A2. As a result, the heating efficiency of the heating well 10 can be further enhanced.

The water injection well 32 is for injecting water (hot water) having a higher temperature than the groundwater flowing into the treatment target area A2 into the treatment target area A2. A plurality of water injection wells 32 are provided around the treatment target area A2. The water injection well 32 is arranged to extend downward from the ground surface in the depth direction.
The water injection well 32 may be, for example, a cylindrical body having a plurality of small holes through which warm water can pass. It is preferable that the tubular body has a heat insulating property. The tubular body may be provided with a heating tool capable of heating the water flowing therein.

The arrangement of the heating wells 10 is similar to the arrangement of the heating wells 10 of the first embodiment.
The arrangement of the suction wells 20 is similar to the arrangement of the suction wells 20 of the first embodiment.
The arrangement of the water injection wells 32 is the same as the arrangement of the water injection wells 30 of the first embodiment.

≪In-situ purification method for contaminated soil≫
The in-situ purification method of this embodiment has a heating process, a suction process, and a water injection process.
The in-situ purification method of this embodiment is the same as the in-situ purification method of the first embodiment except that the contaminated soil is purified using the in-situ purification system 2 .

According to the in-situ purification system 2 of the present embodiment, since the water injection well 32 is provided, hot water can be injected into the treatment target area A2. Therefore, it is possible to prevent the temperature of the treatment target area A2 from decreasing due to the inflow of groundwater from the outside of the treatment target area A2. As a result, the heating efficiency of the heating well 10 can be further enhanced.
According to the in-situ purification system 2 of this embodiment, the heat obtained by the heat exchanger 40 can be used as a heat source for warming the water to be injected in the water injection process. Therefore, the energy for warming the water to be injected in the water injection process can be saved, and the environmental load can be reduced.

Although the in-situ cleaning system and the in-situ cleaning method of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present invention.
For example, although the in-situ purification system 1 of the first embodiment has the heat exchanger 40, the in-situ purification system may not have a heat exchanger. However, the in-situ purification system preferably has a heat exchanger because the heat obtained by the heat exchanger can be effectively used and the environmental load can be reduced.
For example, although the in-situ purification system 1 of the first embodiment has the heat exchanger 40 , the in-situ purification system may have heat exchangers other than the heat exchanger 40 . Examples of heat exchangers other than the heat exchanger 40 include a heat exchanger connected to an exhaust gas treatment device. By having a heat exchanger other than the heat exchanger 40, the obtained heat can be used more effectively, and the environmental load can be further reduced.
For example, although the in-situ purification system 1 of the first embodiment has the gas-liquid separator 50, the in-situ purification system may not have the gas-liquid separator. However, the in-situ purification system preferably has a gas-liquid separation device because it separates the contaminant-laden fluid into gas and liquid so that the contaminants can be separated and removed more efficiently.
For example, although the in-situ purification system 1 of the first embodiment has the waste liquid treatment device 70, the in-situ purification system may not have the waste liquid treatment device. However, it is preferred that the in-situ purification system include a wastewater treatment device, as it can separate and remove the contaminants from the liquid containing the contaminants.

For example, the in-situ purification system 2 of the second embodiment has the water injection well 32 around the treatment target area A2, but the in-situ purification system may have the water injection well inside the treatment target area.
For example, in the in-situ purification system 1 of the first embodiment, a plurality of heating wells 10 are arranged so as to line up in a straight line in plan view along the horizontal outer periphery of the processing target area A1. A plurality of heating wells 10 are provided in a staggered arrangement in the horizontal interior region of the .
However, the heating wells may not be arranged in a straight line in plan view, may be arranged on the circumference of a circle or an ellipse, or may be arranged irregularly. good. In addition, in the inner region of the processing target region, the heating wells may be arranged in a grid pattern in plan view, may be arranged in a honeycomb pattern, or may be arranged irregularly.
For example, in the in-situ purification system 1 of the first embodiment, a plurality of suction wells 20 are provided in a horizontal inner region of the processing target region A1 in a zigzag arrangement in plan view.
However, the suction wells may be arranged in a grid pattern in plan view, may be arranged in a honeycomb pattern, or may be irregularly arranged.
For example, in the in-situ purification system 1 of the first embodiment, a plurality of water injection wells 30 are arranged in a straight line in a plan view along the horizontal outer periphery of the processing target area A1. A plurality of water injection wells 30 are provided in a staggered arrangement in the horizontal inner region of the .
However, the water injection wells may not be arranged in a straight line in a plan view, they may be arranged on the circumference of a circle or an ellipse, or they may be arranged irregularly. good. In addition, in the inner region of the processing target region, the water injection wells may be arranged in a grid pattern in plan view, may be arranged in a honeycomb pattern, or may be arranged irregularly.
For example, in the in-situ purification system 1 of the first embodiment, a plurality of water injection wells 30 are arranged on the same straight line as the straight line on which the plurality of heating wells 10 are arranged.
However, the plurality of water injection wells 30 may be arranged on the same straight line as the plurality of suction wells 20, or may be arranged irregularly.
The number of heating wells, suction wells, and water injection wells is not limited to the numbers exemplified in the above-described embodiments, and may be one or more for one processing target area.
The suction wells are preferably arranged to evenly cover the heating wells.
The injection wells are preferably arranged to evenly cover the heating wells.
The injection wells are preferably arranged to evenly cover the plurality of suction wells.

For example, in the in-situ purification system 1 of the first embodiment, the treated water obtained by the waste liquid treatment device 70 is discharged outside the system. may be used.
For example, although the in-situ purification system 1 of the first embodiment has the heating well 10 and the suction well 20, one well may serve as both the heating well and the suction well in the in-situ purification system.
For example, the in-situ purification system 1 of the first embodiment is arranged such that the heating well 10 extends downward from the ground surface in the depth direction.
However, the heating wells may be arranged to extend horizontally in the ground.
For example, the in-situ purification system 1 of the first embodiment is arranged such that the suction well 20 extends downward from the ground surface in the depth direction.
However, the suction wells may also be arranged to extend horizontally in the ground.
For example, the in-situ purification system 1 of the first embodiment is arranged such that the water injection well 30 extends downward from the ground surface in the depth direction.
However, the water injection well may be arranged in the ground so as to extend horizontally.

DESCRIPTION OF SYMBOLS 1, 2... In-situ purification system, 10... Heating well, 20... Suction well, 30, 32... Water injection well, 40... Heat exchanger, 50... Gas-liquid separator, 60... Exhaust gas treatment apparatus, 70... Waste liquid treatment Apparatus, A1, A2 ... processing target area, W ... impervious wall, L ... water level surface, L1 to L6 ... piping

Claims (9)

one or more heating wells that apply heat treatment to at least a portion of a treatment target area where contaminated soil contaminated with a contaminant exists;
one or more suction wells located within the region to be treated for suctioning at least a portion of the contaminant-laden fluid resulting from the heat treatment;
one or more water injection wells located in or around the area to be treated and having a higher temperature than groundwater flowing into the area to be treated and injecting water into the area to be treated. Position purification system. 2. An in-situ remediation system for contaminated soil according to claim 1, comprising a gas-liquid separator connected to said suction well. 3. An in-situ remediation system for contaminated soil according to claim 1 or 2, comprising a heat exchanger connected to said suction well. 4. The in-situ purification system for contaminated soil according to claim 3, wherein the heat obtained by said heat exchanger is used as a heat source for said water injected from said water injection well. a heating step of heat-treating at least a portion of a treatment target area in which contaminated soil contaminated with a contaminant exists;
a suction step of sucking at least part of the fluid containing the contaminants generated by the heat treatment;
and a water injection step of injecting water having a higher temperature than groundwater flowing into the treatment target area into or around the treatment target area. The method for in-situ remediation of contaminated soil according to claim 5, wherein the heating temperature in the heating step is 60°C or higher. 7. The method for in-situ remediation of contaminated soil according to claim 5 or 6, wherein said contaminant is one or more selected from volatile organic compounds, oil, mercury, polychlorinated biphenyls and dioxins. The method for in-situ remediation of contaminated soil according to any one of claims 5 to 7, further comprising a heat exchange step of obtaining heat from the fluid after the suction step. 9. The method for in-situ purification of contaminated soil according to claim 8, wherein the heat obtained in the heat exchanging step is used as a heat source for the water injected in the water pouring step.

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