JP2009006304A - Cleaning system and cleaning method for oil contaminated soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning system capable of effectively supplying a decomposition-promoting substance such as oxygen and nutrient salts at space saving, and performing soil cleaning at high efficiency, and to provide a cleaning method for oil contaminated soil. <P>SOLUTION: The cleaning system has an injection well 1 for supplying bubble-containing water to oil contaminated soil 35, and decomposes oil in situ with microorganisms. The system has a structure of inserting a tubular body in the injection well 1, forming a water permeable lower screen tube 5 in the lower part of the tubular body, forming a water permeable upper screen tube 3 above the lower screen tube and in a position corresponding to the surface of ground water, disposing a non-porous tube 4 between the lower screen tube 5 and the upper screen tube 3, and having a generation device 10 for fine bubble-containing water for supplying fine bubble-containing water 19 to the lower screen tube 5 and a supply device 20 for decomposition-promoting substance for supplying a decomposition-promoting substance 21 for promoting oil decomposition with microorganisms to the upper screen tube 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oil-contaminated soil purification system and method for purifying soil by decomposing oil existing in contaminated soil (including groundwater) by microorganisms in situ.

In recent years, pollutants that cause environmental destruction or have an adverse effect on living organisms have been detected in soil and groundwater, and environmental pollution caused by these substances has been a problem. Various methods are used to purify contaminated soil and groundwater. Conventionally, contaminated soil (hereinafter referred to as groundwater) is removed from the ground by excavation, etc., and externally washed or heat-treated with water or solvent to make it harmless. Many methods were used. However, the method of removing the contaminated soil on the ground and physicochemically purifying it requires a large-scale construction and increases the cost, and is limited to the purification of a high-concentration, narrow-area contaminated zone. Furthermore, if there is a facility in operation on contaminated soil or groundwater, methods such as excavating the soil may not be possible.
In-situ treatment at the contaminated site is desired when the contaminated area covers a relatively wide area. In recent years, it has been possible to easily and inexpensively purify soil contaminated with pollutants. A biological treatment has been proposed and put into practical use.

  The biological purification method is a purification technology that is suitable for the purification of pollutants other than heavy metals, such as oil and volatile organic compounds, and that repairs contaminated soil using the ability to decompose microorganisms. There is called bioremediation. This is a method of decomposing pollutants in soil using microorganisms originally present in contaminated soil and groundwater. When microorganisms present in the field are used (biostimulation), microorganisms are injected. There are cases (bioaugmentation). In any case, nutrients and the like necessary for the growth and survival of microorganisms are supplemented as necessary to enhance the decomposition activity of the microorganisms and promote the decomposition. In recent years, bioremediation has attracted attention as an effective technique for the purification of contaminated soil because it does not require excavation of contaminated soil and extraction of contaminants and can be used in a wide range at low cost because it can purify soil in situ.

On the other hand, contamination with oil can be cited as a cause of soil contamination. Since oil is used in various petroleum products and used in various fields, it is thought that there is a lot of potential pollution to the soil due to oil leaks and inappropriate disposal. In the purification treatment of oil-contaminated soil, it is known that the oil content in the soil is decomposed by aerobic microorganisms in an aerobic environment.
Therefore, as a method for purifying soil contaminated with oil in situ, Patent Document 1 (Japanese Patent Laid-Open No. 2005-279415) injects oxygen source into soil contaminated with oil to activate microorganisms in the soil. A method of purifying by purification is disclosed. In this method, the groundwater level is lowered below the contaminated soil by the pump, the saturated zone located below the contaminated soil is aerated by the aeration well, and the fungus is supplied from the fungus supply well 16. Like to do.

  In general, oil in soil exists at a high concentration on the groundwater surface, which is the boundary between the unsaturated zone and saturated zone of the soil, and is contaminated by diffusion in the horizontal direction due to the flow of groundwater. Therefore, according to patent document 1, oxygen can be supplied with respect to contaminated soil, and decomposition | disassembly of oil will be accelerated | stimulated. Furthermore, Patent Document 1 discloses a configuration for supplying a nutrient source together with an oxygen source from an injection well as necessary.

  Moreover, as an example of a method for supplying air, Patent Document 2 (Japanese Patent Laid-Open No. 2001-347255) discloses a method for injecting or infiltrating a liquid containing fine bubbles into the ground. Since fine bubbles have a slow ascending speed in the ground and also diffuse in the lateral direction, they are dispersed substantially uniformly in the area to be cleaned in the ground, so that it is possible to clean the ground uniformly. It will be.

JP-A-2005-279415 JP 2001-347255 A

  However, in the method described in Patent Document 1, it is necessary to install a plurality of wells such as a pumping well, an aeration well and a fungus supply well for one apparatus, so that the installation space becomes wide and installation work is required. Takes time and costs. Furthermore, Patent Document 1 proposes a configuration in which aeration is performed by a blower. However, since the supplied air becomes relatively large bubbles and has a large buoyancy and rises quickly, it is difficult to supply air in a wide range in the horizontal direction. could not.

On the other hand, in patent document 2, it is set as the structure which supplies a fine bubble, and it is possible to make the influence range of air wide. However, when supplying nutrients, a configuration is disclosed in which the nutrients are added to a liquid containing fine bubbles, that is, a configuration in which air and nutrients are supplied from a single well. While the bubbles rise, the nutrients mainly spread in the horizontal direction or in the downward direction, and since the influence ranges thereof are different, it is difficult to say that these act effectively.
Therefore, in view of the above-mentioned problems of the prior art, the present invention can effectively supply oxygen and a substance that promotes microbial activation such as nutrient salt in a space-saving manner, and performs soil purification with high efficiency. It is an object of the present invention to provide an oil-contaminated soil purification system and purification method.

Therefore, in order to solve such problems, the present invention includes an injection well for supplying bubble-containing water into soil contaminated with oil (including groundwater), and decomposes the oil in situ by the action of microorganisms. In the purification system for oil-contaminated soil that purifies the soil,
A tubular body is inserted into the injection well, and a lower screen pipe having water permeability is formed at a lower portion of the tubular body, and the above-described lower screen pipe is positioned above the lower screen pipe and at a position corresponding to the groundwater surface of the contaminated soil. An upper screen tube having water permeability is formed in a space separated from the lower screen tube, and a non-porous tube is disposed between the lower screen tube and the upper screen tube,
Fine bubble-containing water supply means for supplying fine bubble-containing water to the lower screen tube, and a decomposition promotion substance supply means for supplying a decomposition promotion substance for promoting oil decomposition by the microorganisms to the upper screen tube are provided. It is characterized by that.

In the present invention, the injection well is provided with a lower screen tube and an upper screen tube at different positions in the height direction, and a non-porous tube having a predetermined length is disposed between the lower screen tube and the upper screen tube.
Since fine bubble-containing water is supplied from the lower screen tube, the fine bubbles spread over a wide range in the horizontal direction, and the rising speed of the fine bubbles is slow and slowly diffuses toward the upper contaminated area. The fine bubble-containing water peels off the oil attached to the soil by the fine bubbles, and can continuously increase the dissolved oxygen concentration in the soil by the action of the bubbles and dissolved oxygen in the fine bubble-containing water. This dissolved oxygen is in a form that can be easily used by microorganisms.
On the other hand, a decomposition promoting substance is supplied from the upper screen tube. Since the upper screen tube is located in the vicinity of the groundwater surface where the oil is concentrated, it acts directly on the decomposition of the oil and is efficiently consumed with little loss of decomposition promoting substances such as nutrient salts. In addition, the decomposition promoting substance may be appropriately supplied as necessary and may not be supplied.

As described above, since the screen tube is provided at two depths and the water containing fine bubbles and the decomposition promoting substance are supplied from different screen tubes, each of them effectively acts on the soil purification, with high efficiency. It becomes possible to purify the contaminated soil.
In addition, since a non-porous tube having a predetermined length is disposed between the lower screen tube and the upper screen tube, water containing fine bubbles ejected from the lower screen tube enters the upper screen tube and the decomposition promoting substance flows out. Can be prevented.
Furthermore, in this invention, since it is the structure which can inject | pour a microbubble and a decomposition promoting substance from one injection well, it can apply also in a small space and can attain space saving.
In addition, this invention is applicable to both the case where the microorganisms which exist in the field are utilized (biostimulation), and the case where microorganisms are injected (bioaugmentation).

The upper screen tube has a length corresponding to a change in the groundwater surface of the contaminated soil.
In general, the water level of the groundwater surface may change depending on the situation, but by making the upper screen tube the length corresponding to the change of the groundwater surface as in the present invention, it is possible to ensure the decomposition promoting substance regardless of the change of the groundwater surface. Can be supplied to the contaminated area.

Further, the fine bubbles are microbubbles having a diameter of 50 μm or less or nanobubbles having a diameter of 1 μm or less.
Since the microbubbles or the nanobubbles also enter the fine soil voids, the oil inside the microbubbles can be efficiently peeled off, and the dissolved oxygen concentration in the contaminated soil can be increased uniformly. Furthermore, since the microbubbles or the nanobubbles have a negative potential, they easily adhere to oil having a positive potential, and as a result, the adhesion cleaning function is high.

Furthermore, the decomposition promoting substance supply means includes nutrients such as N and P that activate microorganisms in the soil, organic substances required for decomposition of microorganisms such as carbohydrates, minerals such as Fe, and activated water. Alternatively, it is a means for mixing a decomposition promoting substance composed of at least one of aerobic microorganisms or a mixture thereof with water, and supplying the generated decomposition promoting substance mixed water.
Thereby, the substance required for the decomposition | disassembly of the oil by microorganisms can be replenished, and soil purification efficiency improves.

In addition, an injection well is installed in soil contaminated with oil (including groundwater), water containing bubbles is supplied from the injection well, and the soil is purified by the action of microorganisms in situ to purify the soil. In the purification method of the oil-contaminated soil,
A tubular body is inserted into the injection well, and water containing fine bubbles is injected into the soil from a lower screen tube having water permeability formed at the bottom of the tubular body,
From the upper screen tube having water permeability formed above the lower screen tube through a non-porous tube, a decomposition promoting substance for promoting oil decomposition by the microorganism is injected near the groundwater surface of the soil as necessary. It is characterized by doing.

Further, the method for purifying oil-contaminated soil, wherein the groundwater flow after the treatment is monitored by the observation well installed downstream of the injection well,
The decomposition promoting substances are nutrients such as N and P that activate microorganisms in the soil, organic substances required for decomposition of microorganisms such as carbohydrates, minerals such as Fe, activated water, or aerobic microorganisms The decomposition promoting substance is appropriately selected based on the result of the monitoring, and the selected decomposition promoting substance is mixed with water and injected from the upper screen tube. It was made to do.

As described above, according to the present invention, a screen tube having a space partitioned at two depths of the injection well is provided, fine water-containing water is supplied from the lower screen tube, and a decomposition promoting substance is supplied from the upper screen tube. Therefore, each acts on the soil purification over a wide range and effectively, and the contaminated soil can be purified with high efficiency.
In addition, since a non-porous tube having a predetermined length is arranged between the lower screen tube and the upper screen tube, the water containing fine bubbles injected from the lower screen tube enters the upper screen tube and the decomposition promoting substance flows out. Can be prevented.
Furthermore, by making the upper screen tube have a length corresponding to the change in the groundwater surface, it becomes possible to reliably supply the decomposition promoting substance to the contaminated area regardless of the change in the groundwater surface.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.
1 is an overall configuration diagram of a purification system according to an embodiment of the present invention, FIG. 2 is a side sectional view showing an injection well according to this embodiment, FIG. 3 is a plan view showing a well arrangement according to this embodiment, and FIG. Is a schematic diagram of a fine bubble generating apparatus applied to this embodiment, and FIG. 5 is a flow of a purification method according to the embodiment of the present invention.

With reference to FIG. 1, the overall configuration of this embodiment will be described.
In the figure, the ground surface 30 is formed of an unsaturated zone 31 that does not include groundwater, and a saturated zone 33 that includes groundwater is laminated below the unsaturated zone 31. The groundwater surface 32 exists near the boundary between the unsaturated zone 31 and the saturated zone 33.
Contaminated soil contaminated with oil exists in the unsaturated zone 31 and the saturated zone 33 including the groundwater surface 32, and the oil is most concentrated in the vicinity of the groundwater surface 32.

The purification system according to the present embodiment is installed above the contaminated soil, and includes an injection well 1, a fine bubble-containing water generator 10, a decomposition promoting substance mixed water supply device 20, and an observation well 25. And
The injection well 1 is formed by excavating vertically from the ground surface 30 to a saturation zone 33 located below the contaminated soil 35. Preferably, it is installed upstream of the groundwater flow of the contaminated soil 35 to be purified.

Similarly, the observation well 25 is formed by excavating vertically from the ground surface 30 to a saturation zone 33 located below the contaminated soil 35. As shown in FIG. 3, the observation well 25 is installed at a predetermined distance L on the downstream side of the injection well 1 with respect to the groundwater flow. The distance L is a distance that is affected by the purification treatment by the injection well 1. The observation well 25 is a well equipped with a pump for monitoring the state of groundwater such as oil content, water quality, and number of microorganisms in the groundwater by pumping up groundwater.
In the present embodiment, the most preferable configuration is shown in which the injection well 1 and the observation well 25 are installed in the vertical direction. However, these wells 1 and 25 may be installed in the inclined direction or in the lateral direction. Applicable when a building or the like is located directly above the soil 35. In the figure, reference numeral 40 denotes an oil decomposition range by aerobic microorganisms in the present system.

  The injection well 1 is a well for supplying the fine bubble-containing water 19 and the decomposition promoting substance mixed water 21 into the soil. A specific configuration of the injection well 1 is shown in FIG. A tubular body is inserted into the injection well 1, a lower screen tube 5 having water permeability is formed at the lower portion of the tubular body, and a space separated from the lower screen tube 5 is provided above the lower screen tube 5. An upper screen tube 3 having water permeability is provided. A lower non-porous tube 4 having a predetermined length is provided between the lower screen tube 5 and the upper screen tube 3. An upper non-porous tube 2 is also provided between the upper screen tube 5 and the ground surface 30.

The lower screen tube 5 is located in the saturation zone 33 below the contaminated soil 35. The upper screen tube 3 has a position corresponding to the groundwater surface 32 in the contaminated soil 35, and the upper screen tube 3 has a length corresponding to the displacement of the groundwater surface 32. This makes it possible to reliably supply the decomposition promoting substance mixed water 21 to the contaminated soil 35 regardless of the water level change of the groundwater surface 32.
These screen tubes 3 and 5 have a plurality of water passage holes, and the shape of the water passage holes may be either a circular shape or a long hole shape. When making it into a long hole shape, it is preferable to form so that a long diameter (or long side) may exist in a horizontal direction. The opening ratios of the screen tubes 3 and 5 are set according to the particle size of the soil, the strength of the tubes, the pressure of the liquid to be supplied, and the like. Preferably, the opening ratio is about 3 to 10%. Good.

The lower screen tube 5 is connected to a water supply pipe 6 containing fine bubbles extending from the top of the injection well 1 via a reducer. The upper screen pipe 3 is connected to a decomposition promoting substance supply pipe 7 extending from the upper part of the injection well 1. The lower screen tube 5 and the upper screen tube 3 are spatially partitioned through a non-porous tube 4 and are configured so that fluid does not communicate with each other. The injection well 1 may have a double pipe structure, the inner pipe may be the fine bubble-containing water supply pipe 6, and the outer pipe may be the decomposition promoting substance supply pipe 7.
The lower non-porous tube 4 has such a length that the fine bubble-containing water 19 ejected from the lower screen tube 5 does not enter the upper screen tube 3.

Referring to FIG. 1, the lower screen tube 5 is connected to the fine bubble-containing water generator 10 installed on the ground surface by the fine bubble-containing water supply pipe 6. The upper screen tube 3 is connected to the decomposition promoting substance mixed water supply device 20 installed on the ground surface by the decomposition promoting substance supply pipe 7.
The fine bubble-containing water generator 10 is a device for producing water containing fine bubbles, and a known device can be used.
As an example, a specific configuration of the fine bubble-containing water generator 10 is shown in FIG. The fine bubble-containing water generator 10 supplies air 18 from the compressor 12 to the raw water 17 stored in the raw water tank 11 via a static mixer (not shown). Here, tap water, ground water, or the like is used as the raw water 17, but in the case of tap water, it is preferably used after removing chlorine. In the fine bubble-containing water generator 10, air 18 and pure oxygen can be used as the raw material for the bubbles. When using pure oxygen, it is preferable to use it after vaporizing liquid oxygen using Dewarbin (a heat insulating container in which the inside of the double wall is evacuated). The dissolved oxygen concentration in the case of air is about 7 to 8 mg / L, and in the case of pure oxygen, it is about 14 to 20 mg / L.

The static mixer is a non-driven mixer that uses a known device and mixes the flow rate of the fluid as an energy source, and enables uniform and rapid mixing, thereby generating fine bubbles in water. The fine bubbles are preferably microbubbles having a diameter of 50 μm or less, and more preferably nanobubbles having a diameter of 1 μm or less.
The raw water 17 in which the fine bubbles are generated is fed to the blender 15 by the pressure pump 13. At this time, the flow rate is adjusted by a flow rate adjustment valve (not shown) based on the pressure gauge 14. Fine bubbles are uniformly mixed with raw water in the blender 15, and the generated fine bubble-containing water is supplied to the fine bubble-containing water supply pipe 6. In the figure, 16 is a flow meter.

  Referring to FIG. 1, the decomposition promoting substance mixed water supply device 20 includes nutrients such as N and P that activate microorganisms in the soil, organic substances necessary for decomposition of microorganisms such as carbohydrates, Fe, and the like. Decomposition promoting substance consisting of mineral, activated water, or aerobic microorganisms is mixed with water to produce decomposition promoting substance mixed water, which is supplied to the injection well 1 by a pump. Device. This decomposition promoting substance mixed water is appropriately selected from the plurality of decomposition promoting substances described above according to the type and amount of oil as a pollutant or the state of contaminated soil (for example, nitrogen concentration, microbial concentration, etc.). In that case, it is preferable to set and supply the kind and quantity of decomposition | disassembly acceleration | stimulation substance required from the result monitored in the said observation well 25, and also supply timing.

Next, the processing operation in the present embodiment will be described with reference to FIG. In addition, in the Example shown below, a numerical value is an example and is not limited to these.
First, the injection well 1 and the observation well 25 are installed at the position where the contaminated soil 35 exists (S1). The diameter of the well pipe is about 100 mm and has the structure shown in FIGS. The lower screen tube 5 is installed so as to be located at a depth about 3 m deeper than the groundwater surface 32. At this time, since a range of about 3 m around the injection well can be an aerobic environment, the range of 2.5 m radius from the injection well 1 is set as the purification target range. Therefore, one observation well 25 is installed at a position of 2.5 m downstream from at least the injection well.

Moreover, the fine bubble containing water generator 10 and the decomposition promotion substance mixed water supply apparatus 20 are installed in the vicinity of the injection well 1, and the decomposition promotion substance mixed water is prepared (S2).
The fine bubble-containing water 19 generated by the fine bubble-containing water generator 10 is sent to the injection well 1 and injected into the soil from the lower screen tube 5. In principle, continuous injection is used, and the injection amount is about 15 L / min. The fine bubble-containing water 19 rises slowly while spreading over a wide area, peels off the oil adsorbed on the soil by the contaminated soil 35, and reduces the dissolved oxygen concentration of the soil by the bubbles and dissolved oxygen in the fine bubble-containing water 19. Sustainably increase, maintain good aerobic state, and activate aerobic microorganisms.
Further, since the fine bubbles enter a place where flow is difficult, such as a shield or a groove, the oil in the inside can be efficiently peeled off. Furthermore, since the fine bubbles have a negative potential, they tend to adhere to oil having a positive potential, and as a result, the adhesion cleaning function is high.

Furthermore, the decomposition promoting substance mixed water 21 generated by the decomposition promoting substance mixed water supply device 20 is poured into the soil from the upper screen tube 3 as required (S3). The decomposition promoting substance is mixed with tap water from which chlorine has been removed or groundwater at the target site, stored in a container, sent by a pump, and injected into the soil from the upper screen tube 3.
In the contaminated soil 35 in an aerobic state, oil is decomposed by the action of microorganisms while supplementing necessary substances with the decomposition promoting substance mixed water 21.
Next, the oil content, water quality, the number of microorganisms, etc. in the groundwater pumped in the observation well 25 are monitored, and the lacking nutrient salt, organic matter, mineral content, activated water or microorganisms are injected as decomposition promoting substance mixed water 1 More appropriate injection is performed (S4).
The monitoring items in the observation well 25 are as follows.
Oil film, TPH, BTEX, etc. as oil content, pH, DO, ORP, EC, water temperature, iron, manganese, color, etc. as water quality, nitrogen concentration, phosphorus concentration, and bacterial count as microorganisms are detected and measured.
Then, when the pollutant falls below the reference value in the observation well 25, the process is terminated (S5).

  According to this embodiment, the injection well 1 is provided with a lower screen tube 5 and an upper screen tube 3 at different positions in the height direction, and a non-porous tube having a predetermined length is provided between the lower screen tube 5 and the upper screen tube 3. 4 is arranged so that the fine bubble-containing water 19 is supplied from the lower screen tube 3, so that the fine bubbles spread over a wide range in the horizontal direction and slowly rise toward the upper contaminated area. Spread. In addition, the fine bubble-containing water 19 exfoliates oil adhering to the soil by the fine bubbles, and continuously increases the dissolved oxygen concentration in the soil by the action of the bubbles and dissolved oxygen, so that the microorganisms can be efficiently decomposed. On the other hand, the decomposition promoting substance mixed water 21 is supplied from the upper screen pipe 5 as necessary, and the upper screen pipe 5 is located near the ground water surface where the oil is concentrated, and is directly used for oil decomposition. Therefore, there is little loss of decomposition promoting substances such as nutrient salts, and it is consumed efficiently.

Thus, since the screen tubes 5 and 3 are provided at two depths, and the fine bubble-containing water 19 and the decomposition promoting substance mixed water 21 are supplied from different screen tubes 5 and 3, each is effective for soil purification. It becomes possible to purify the contaminated soil 35 with high efficiency.
Further, since the non-porous tube 4 having a predetermined length is disposed between the lower screen tube 5 and the upper screen tube 3, the fine bubble-containing water 19 injected from the lower screen tube 5 enters the upper screen tube 5, It is possible to prevent the decomposition promoting substance mixed water 19 from flowing out. Further, in this embodiment, since the fine bubbles and the decomposition promoting substance can be injected from one injection well, the present invention can be applied even in a small space and space saving can be achieved.

1 is an overall configuration diagram of a purification system according to an embodiment of the present invention. It is side sectional drawing which shows the injection well which concerns on a present Example. It is a top view which shows the well arrangement | positioning which concerns on a present Example. It is the schematic of the fine bubble generator applied to a present Example. It is a flow of the purification method which concerns on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection well 2 Upper non-porous tube 3 Upper screen tube 4 Lower non-porous tube 5 Lower screen tube 8 Reducer 10 Fine bubble-containing water generator 19 Fine bubble-containing water 20 Decomposition promoting substance mixed water supply device 21 Decomposition promoting substance mixed water 25 Observation well 32 Groundwater surface 35 Contaminated soil

Claims (6)

An oil-contaminated soil purification system that has an injection well that supplies bubble-containing water into soil contaminated with oil (including groundwater), and decomposes the oil by the action of microorganisms in situ to purify the soil. In
A tubular body is inserted into the injection well, and a lower screen pipe having water permeability is formed at a lower portion of the tubular body, and the above-described lower screen pipe is positioned above the lower screen pipe and at a position corresponding to the groundwater surface of the contaminated soil. An upper screen tube having water permeability is formed in a space separated from the lower screen tube, and a non-porous tube is disposed between the lower screen tube and the upper screen tube,
Fine bubble-containing water supply means for supplying fine bubble-containing water to the lower screen tube, and a decomposition promotion substance supply means for supplying a decomposition promotion substance for promoting oil decomposition by the microorganisms to the upper screen tube are provided. An oil-contaminated soil purification system.   The oil-contaminated soil purification system according to claim 1, wherein the upper screen tube has a length corresponding to a change in a groundwater surface of the contaminated soil.   The oil-contaminated soil purification system according to claim 1, wherein the fine bubbles are micro bubbles having a diameter of 50 µm or less or nano bubbles having a diameter of 1 µm or less.   The decomposition promoting substance supply means includes nutrients such as N and P that activate microorganisms in the soil, organic substances required for decomposition of microorganisms such as carbohydrates, minerals such as Fe, activated water, The oil-contaminated soil according to claim 1, wherein the decomposition-accelerating substance comprising at least one of the aerobic microorganisms or a mixture thereof is mixed with water, and the generated decomposition-accelerating substance mixed water is supplied. Purification system. Oil in which an injection well is installed in soil contaminated with oil (including groundwater), bubble-containing water is supplied from the injection well, and the soil is purified by the action of microorganisms in place to purify the soil. In the purification method of contaminated soil,
A tubular body is inserted into the injection well, and water containing fine bubbles is injected into the soil from a lower screen tube having water permeability formed at the bottom of the tubular body,
From the upper screen tube having water permeability formed above the lower screen tube through a non-porous tube, a decomposition promoting substance for promoting oil decomposition by the microorganism is injected near the groundwater surface of the soil as necessary. A method for purifying oil-contaminated soil. The method for purifying oil-contaminated soil according to claim 5, wherein the state of groundwater after treatment is monitored by an observation well installed on the downstream side of the groundwater flow with respect to the injection well,
The decomposition promoting substances are nutrients such as N and P that activate microorganisms in the soil, organic substances required for decomposition of microorganisms such as carbohydrates, minerals such as Fe, activated water, or aerobic microorganisms The decomposition promoting substance is appropriately selected based on the result of the monitoring, and the selected decomposition promoting substance is mixed with water and injected from the upper screen tube. A method for purifying oil-contaminated soil, characterized by comprising:

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