JP2012121013A - Method for remediation of polluted soil in situ - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for sufficiently remediating polluted soil in an unsaturated band at a low cost in situ without eluting a polluting substance before its decomposition even in the case the polluted area is spread in a wide range and in the case the pollutant concentration is uneven.SOLUTION: The method is for remediating polluted soil in situ by supplying water or an aqueous solution containing an activation agent for microorganism for decomposing a polluting substance to the surface layer of the soil polluted with the polluting substance in an unsaturated band, penetrating the soil with the water or the solution by spontaneous flow, and carrying out biological treatment of the polluted soil and is characterized in that the water amount in an arbitrary depth in the unsaturated band of the polluted soil is measured by a water analyzer and the water amount of the polluted soil is controlled.

Description

  The present invention relates to an in-situ purification method for contaminated soil in an unsaturated zone.

In order to purify contaminated soil and groundwater, there are a method of purifying the soil (in situ), a method of excavating the contaminated soil (on situ), and a method of purifying the soil. In particular, in-situ purification can purify soil in-situ without digging up the soil, so it is less expensive than on-situ purification and can often be constructed even when there are buildings on the ground. In-situ purification is also suitable for purification when the contamination is extensive.
As a purification method for contaminated soil, a method such as bioremediation (biological treatment) for purifying soil with microorganisms is known.

By the way, in the ground, the pollutant may not reach the aquifer (saturated zone) but may remain in the unsaturated zone located above it, and the soil in the unsaturated zone may be contaminated by the pollutant. There is also.
However, the biological treatment described above is generally a method suitable for the purification of saturated soil in a saturated zone, and a method for purifying unsaturated soil in a contaminated zone has not been established so far.

In recent years, attempts have been made to use biological treatments for the purification of unsaturated soil contaminated soil.
For example, Patent Document 1 discloses a method of in-situ purification using microorganism activity by providing a plurality of injection wells and vacuum extraction wells in an unsaturated zone contaminated region or in the surrounding unsaturated zone portion. . According to Patent Document 1, while supplying injection water containing nutrient components and the like from the injection well, operating the vacuum extraction wells installed at two or more locations within the range where pressure reduction influences the injection point, It is said that the injected solution can be diffused in the saturation zone, and as a result, the activity of microorganisms is activated.

In addition, a method other than biological treatment, that is, a method of purifying unsaturated soil contaminated soil by physical or chemical treatment has been proposed.
For example, Patent Document 2 discloses a method of spraying a solution (drug solution) containing a chemical that cleans or detoxifies soil contaminants from the ground surface at a specific supply rate. According to Patent Document 2, the soil can be efficiently purified with a small amount of neutralizing agent.

JP 2002-45841 A Japanese Patent Laid-Open No. 2008-211984

However, as described in Patent Document 1, in the method of injecting a nutrient component that activates a microorganism into a contaminated soil using a well, the microorganism is activated by the nutrient component in the vicinity of the well, and the contaminated soil is easily purified. As the distance from the well increased, the nutrients became difficult to reach and the contaminated soil was difficult to clean.
In Patent Document 1, nutrient components are diffused by providing a vacuum extraction well. However, if the contaminated area covers a wide area, the diffusion effect is not sufficient.
For this reason, in order to purify contaminated soil over a wide area, it is necessary to install a large number of wells, and there is a problem that construction costs are increased.

  Further, as described in Patent Document 2, in the method of spraying the drug solution at a specific supply rate, the drug solution may be sprayed excessively. If the chemical liquid is sprayed excessively, the contaminant before decomposition is likely to flow out of the contaminated area or the saturated zone by the chemical liquid, which may cause new contamination. In addition, even when the concentration of contamination is uneven in the contaminated area, the drug solution is uniformly sprayed. For example, in a place with a high concentration of contamination, the drug solution may be insufficient and purification may not be performed sufficiently. On the other hand, in a place where the concentration of contamination is low, the drug solution is excessively sprayed and is wasted, and can also cause the outflow of contaminants as described above.

  The present invention has been made in view of the above circumstances, and even when the contaminated area extends over a wide range or when the contamination concentration is uneven, the contaminant before the decomposition does not flow out, An object of the present invention is to provide a method that can sufficiently clean in-situ contaminated soil at low cost.

The in-situ purification method for contaminated soil according to the present invention supplies water or an aqueous solution containing an activator for pollutant-degrading microorganisms to the surface layer of unsaturated zone contaminated by contaminants, and naturally flows into the contaminated soil. Infiltration of the contaminated soil by biological treatment, the moisture content of the contaminated soil at an arbitrary depth in the unsaturated zone is measured with a moisture meter, and the moisture content of the contaminated soil is controlled. Features.
In addition, it is preferable to provide an injection well reaching the contaminated soil or the vicinity thereof and inject air from the injection well.
Furthermore, it is preferable to provide a suction well that reaches the contaminated soil or the vicinity thereof and perform suction from the suction well.

  According to the present invention, even when the contaminated area covers a wide range or when the concentration of contamination is uneven, the contaminated soil in the unsaturated zone is sufficiently produced at a low cost without causing the contaminant before the decomposition to flow out. A method capable of cleaning the position can be provided.

It is the schematic which shows an example of the supply method of water and activator aqueous solution. It is the schematic which shows the column sample used by the Example and the comparative example.

The present invention will be described below.
The soil which is the subject of the present invention is unsaturated zone soil (contaminated soil) contaminated with a pollutant.
In the present invention, the “unsaturated zone” is a layer located above an aquifer saturated with groundwater (saturated zone).
Examples of pollutants that cause contamination include cyanide compounds, oils mainly composed of all petroleum hydrocarbons, and organic chlorine compounds. The “cyanide compound” refers to a compound containing CN in its structure, such as a cyanide or a cyan complex of metal (iron, nickel, copper, etc.).

  The in-situ purification method for contaminated soil of the present invention (hereinafter simply referred to as “purification method”) includes an aqueous solution (hereinafter referred to as “active agent aqueous solution”) containing water or an activator for degrading microorganisms in the surface layer of the contaminated soil. )), Infiltrated into the contaminated soil by natural flow, and purified in situ by biological treatment. In addition, the moisture content of the contaminated soil at an arbitrary depth in the unsaturated zone is measured with a moisture meter, and the moisture content of the contaminated soil is managed.

The presence of moisture is important for the purification of contaminated soil by biological treatment. The reason for this is considered as follows.
Moisture penetrates into contaminated soil by supplying water or an aqueous solution of an activator to the surface layer. However, if the supply amount of water or an aqueous solution of the activator is small, the water in the contaminated soil is insufficient and the decomposition of the pollutants by microorganisms proceeds. Without contaminating the soil. Further, if the supply amount becomes excessive and water or an aqueous solution of the activator does not stay in the unsaturated zone but penetrates to the saturated zone, the contamination falls into the saturated zone. Therefore, a certain amount of water is required for purification of contaminated soil.

  In the purification method of the present invention, the moisture content of the contaminated soil at an arbitrary depth of the unsaturated zone is measured with a moisture meter or the like, and the moisture content of the contaminated soil is managed, so in the unsaturated zone that is not saturated with groundwater. Even if it exists, the water | moisture content important for purification | cleaning by biological treatment can be controlled in a certain range. Therefore, an appropriate amount of water is maintained in the contaminated soil, and purification proceeds sufficiently.

  Biological treatment may employ biostimulation (a method of purifying soil by utilizing microorganisms that naturally inhabit the soil) or bioaugmentation (soil) depending on the presence or absence of microorganisms that inhabit the soil. If there are few or no microorganisms inhabiting the soil, a method of purifying soil by introducing a large amount of microorganisms from outside may be employed.

  Examples of microorganisms that decompose pollutants and purify soil include Novosphingobium (Novosphingobium spp.) And Pseudomonas (Pseudomonas spp.). Moreover, the microorganisms used for soil purification may be aerobic or anaerobic. In particular, when the microorganism is aerobic, it will be described in detail later. However, it is preferable to employ biosparging that injects air into the soil and appropriately promotes the activity of the microorganism.

Examples of active agents for microorganisms include amino acids, carbohydrates, and mixtures thereof.
These active agents may be used individually by 1 type, and may use 2 or more types together.

The activator aqueous solution can be prepared by diluting the above-mentioned activator with water.
When two or more activators are used in combination, a mixture of activators may be diluted with water to prepare an activator aqueous solution, or each activator may be diluted with water to prepare a plurality of activator aqueous solutions. May be.

The concentration of the activator in the activator aqueous solution is not particularly limited. Contaminated soil is collected at any place in the contaminated area where in-situ purification is performed, and the contamination state (contamination concentration, etc.) is confirmed to check the contamination. What is necessary is just to prepare an active agent aqueous solution so that it may become a suitable density | concentration according to a state.
For example, a soil contaminated by cyanide, if free cyanide content is 10 mg / kg, the amount of active agent which is a contaminated soil 1.0 m ³ per 0.1～5.0Kg, to 10 to 100 times It is preferred to prepare an aqueous activator solution by diluting with water.
The free cyanide content in the contaminated soil is a value measured in accordance with March 2003 Notification of Ministry of the Environment No. 19 “Matters for Measuring Soil Content Survey”.

There are no particular restrictions on the method of supplying water and the aqueous activator solution, and water can be sprayed onto the surface layer of the contaminated area using, for example, a hose. When the contaminated area covers a wide area, for example, as shown in FIG.
Here, in FIG. 1, the symbol “A” is the surface layer, “B” is the unsaturated zone, “C” is the saturated zone, and “X” is the contaminated soil.

  Moreover, when supplying several activator aqueous solution, you may supply at once and may supply sequentially in intervals. The supply interval is not particularly limited, and may be appropriately determined according to the contamination state.

When water or an activator aqueous solution is supplied to the surface layer of the contaminated soil, the water or the activator aqueous solution penetrates into the contaminated soil by natural flow as shown in FIG. Then, the activity of microorganisms is activated, the pollutants are efficiently decomposed, and the contaminated soil is purified. In particular, when an activator aqueous solution is supplied, the activity of microorganisms is more easily activated.
Moreover, since this invention supplies the water and activator aqueous solution which were supplied to the surface layer of the contaminated soil even to the contaminated soil by infiltration, the water and the activator aqueous solution can be widely distributed. Therefore, it is possible to easily cope with a wide range of contaminated areas, and the cost can be reduced as compared with the injection method from the well.

In the present invention, the moisture content of the contaminated soil at an arbitrary depth in the unsaturated zone is measured with a moisture meter or the like, and the moisture content of the contaminated soil is managed.
The moisture meter is not particularly limited as long as it can measure the amount of moisture in the soil. For example, a tensiometer, a pF meter, a soil moisture sensor, or the like can be used.
Moreover, what is necessary is just to determine the measurement location of a moisture content suitably according to a contamination state (spread of a vertical direction or a horizontal direction). The “arbitrary depth of the unsaturated zone” may be one depth or a plurality of depths depending on the spread of contamination in the vertical direction (depth direction). In other words, when the vertical spread is narrow, it is sufficient to measure the depth at one location, and when the vertical spread is wide, the depth is measured at a plurality of locations. In addition, it is only necessary to measure an arbitrary location in the lateral direction. If the lateral spread is narrow, it is sufficient to measure at one depth, and if the lateral spread is wide, measure at multiple depths. To do.
Moreover, it is preferable to measure the amount of water regularly until the purification is completed, and it is sufficient to perform the measurement once a day.

The water content of the contaminated soil is managed as follows.
First, the water content of the contaminated soil and the field water volume before supplying water or an aqueous activator solution are measured in advance. Then, a management setting value of the moisture content is determined based on the value of the field water capacity, and the moisture content of the contaminated soil after the supply of the water or the aqueous activator solution is measured and managed. Specifically, if the difference in moisture content of the contaminated soil before and after the supply is within the range of the management set value, it is determined to be appropriate. Further, if the amount of water is greater than the management set value, it is determined that the amount is excessive, and conversely if it is less, it is determined that the amount is insufficient.
The management set value is preferably 0.15 to 1.00 times the field capacity.

  Here, “field water capacity” means the water content of the soil when excess water is drained down by gravity after a large amount of rainfall or irrigation, and the drainage rate becomes as low as the evaporation rate. That is. In other words, after raining, drainage is almost finished, and if the surface evaporation is prevented, the amount of water in the soil becomes constant. This constant amount of water is the field capacity.

If the moisture content of the contaminated soil is measured and determined to be appropriate or excessive, water or an aqueous activator solution will not be supplied until it is determined to be insufficient in subsequent measurements.
On the other hand, if it is determined that the amount is insufficient, water or an aqueous activator solution is supplied until the moisture content of the contaminated soil reaches an appropriate value.

In addition, when supplying an activator aqueous solution, moisture is supplied to the contaminated soil by permeation of the activator aqueous solution supplied to the surface layer. Therefore, by measuring the amount of water in the contaminated soil, the activator to the contaminated soil is measured. The degree of reach of can also be confirmed. That is, if the moisture content of the contaminated soil increases before and after supply at a certain depth, it means that the activator has reached that point, and if there is no change in the moisture content (if the moisture content difference is 0), the activator Does not reach that point.
Therefore, when the moisture content of the contaminated soil is measured and determined to be insufficient, if the difference in moisture content before and after the supply is 0, the activator aqueous solution is supplied because the activator has not reached that point. When the difference in water content is not 0, an aqueous activator solution may be supplied. However, since the active agent has reached the contaminated soil, only water may be supplied.

By controlling the amount of water in the contaminated soil in this way, the water important for purification by biological treatment can be controlled within a certain range, and the water in the contaminated soil can be maintained at an appropriate amount. Moreover, when the activator aqueous solution is supplied, the degree of reach of the activator can also be confirmed. Therefore, purification of contaminated soil can proceed smoothly.
Moreover, since the management set value is determined in advance, it becomes a standard of the supply amount of water and the aqueous solution of the activator. Accordingly, it is possible to prevent excessive supply of water and the aqueous solution of the activator, and to suppress the penetration of the water and the aqueous solution of the activator into the saturated zone without remaining in the unsaturated zone. Therefore, it is possible to prevent the contaminant before decomposition from flowing into the saturation zone.

By the way, since the activity of microorganisms is promoted from a portion where water or an aqueous solution of an activator has permeated, purification of contaminated soil proceeds from a shallow portion. Therefore, depending on the permeation speed, water and active agent aqueous solution are likely to be consumed at shallow depths in places where the concentration of contamination is high, and water and active agent aqueous solution tend not to reach as the depth increases. is there.
However, if it is this invention, the extent of arrival of water and aqueous solution of an activator can be confirmed by measuring the water content of the contaminated soil at an arbitrary depth. If the water or the aqueous activator solution has not reached or the water content is insufficient, the water or the aqueous activator solution may be supplied again, and it can be easily determined whether the supply is performed again. In addition, it is easy to determine the supply amount and the concentration of the active agent aqueous solution in the case of supplying from the second time. Therefore, according to the present invention, even if the concentration of contamination is uneven in the contaminated area, the supply of water and the aqueous solution of the activator can be adjusted according to the state of contamination at the supply location. Can be purified.

If the contamination concentration at each location is known in advance, the supply amount and the concentration of the aqueous activator solution can be adjusted according to the supply location.
If it is difficult to determine the concentration of contamination at each location because the contaminated area covers a wide area, reduce the supply amount and concentration of the active agent aqueous solution, and then measure the moisture content of the contaminated soil at an arbitrary depth. It is only necessary to supply water or the aqueous solution of the activator again only to the place judged to be insufficient.

  In the purification method of the present invention, for example, as shown in FIG. 1, it is preferable to provide an injection well 20 reaching the contaminated soil or the vicinity thereof and inject air from the injection well 20. Further, it is preferable to provide a suction well 30 reaching the contaminated soil or the vicinity thereof and perform suction from the suction well 30.

Examples of the injection well 20 and the suction well 30 include a screen well in which a portion corresponding to the position of contaminated soil is screened.
One or a plurality of the injection wells 20 and the suction wells 30 are excavated according to the spread of the contaminated soil X or the like.

A blower 21 for sending air to the contaminated soil through the injection well 20 is connected to the injection well 20.
On the other hand, the suction well 30 is connected to a blower 31 for sucking air, decomposition products of gaseous pollutants, and the like from the contaminated soil through the suction well 30.
As the blowers 21 and 31, known blowers used for bio sparging can be used.

As described above, the microorganisms used for soil purification may be aerobic or anaerobic, but when the microorganisms are aerobic, the microorganisms are more injected by injecting air from the injection well 10 into the contaminated soil. It becomes activated and the purification of the contaminated soil becomes easier to proceed.
In addition, if the surface layer of the contaminated soil is a place with good ventilation, the microorganisms are activated because air is naturally supplied to the contaminated soil without injecting air using the injection well 20. If air is actively injected from the injection well 20, microorganisms can be activated more effectively.

  By the way, when microorganisms are aerobic, when pollutants are decomposed by biological treatment and contaminated soil is purified, depending on the type of pollutants, gases that affect the human body such as hydrogen cyanide may be generated as decomposition products. is there. In such a case, it is possible to suppress the diffusion of the gas generated by the purification of the contaminated soil to the ground surface by sucking air or a gas that is a decomposition product of the contaminant from the contaminated soil through the suction well 30.

  The suction from the injection well 20 and the suction from the suction well 30 may be performed simultaneously, may be performed alternately, or only one of them may be performed. However, when a gas such as hydrogen cyanide is generated, it is preferable to perform at least suction from the suction well 30.

  The injection well 20 is provided for the purpose of air injection, and the suction well 30 is provided for the purpose of air or gas suction. Gases such as air and gas have a wider diffusion range than liquids. Therefore, since the number of wells to be installed is small as compared with the case where the aqueous activator solution is injected from the well into the contaminated soil as in the prior art, the construction cost is less likely to be required.

As described above, according to the purification method of the present invention, the water and the active agent aqueous solution supplied to the surface layer of the contaminated soil are supplied to the contaminated soil by infiltration, so that the water and the active agent aqueous solution are widely distributed. be able to. Therefore, it is possible to easily cope with a wide range of contaminated areas, and it is possible to sufficiently clean in situ the contaminated soil in the unsaturated zone at a lower cost than the injection method from the well.
In addition, by measuring and managing the amount of water in the contaminated soil, the water important for purification by biological treatment can be controlled within a certain range, and the water in the contaminated soil can be maintained at an appropriate amount. Moreover, when the activator aqueous solution is supplied, the degree of reach of the activator can also be confirmed. Accordingly, it is possible to prevent excessive supply of water or an aqueous solution of the activator, and to suppress the outflow of contaminants before decomposition. In addition, even when the concentration of contamination is uneven in the contaminated area, the water activity and the supply of the aqueous solution of the activator can be adjusted according to the state of contamination at the supply location, so that the contaminated soil can be sufficiently purified regardless of the concentration of contamination.

Moreover, in this invention, after constructing a water-permeable embankment and asphalt in the surface layer of contaminated soil, you may supply water or aqueous activator solution. If construction is carried out before supply, in-situ purification can be performed while secondary use of land such as parks, grounds, and parking lots.
Also, even if contaminated soil is confirmed after construction of asphalt, etc., if the asphalt is permeable, water or an aqueous solution of the activator is natural if water or an activator aqueous solution is supplied from above. It penetrates into contaminated soil by flowing down. Therefore, it is not necessary to excavate a well for supplying water or an activator aqueous solution, so that in-situ purification can be performed at low cost.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.

[Production of soil for evaluation]
The soil contaminated with cyanide was excavated. It was 20 mg / kg when the free cyan content (F-CN content) of the excavated contaminated soil was measured.
Subsequently, the contaminated soil was sufficiently kneaded to make the cyan concentration in the contaminated soil uniform, and this was used as evaluation soil.
In addition, F-CN content of soil was measured based on March, 2003 Ministry of the Environment Notification No. 19 “Matters for Measuring Soil Content Survey”.

[Preparation of aqueous activator solution]
Two types of aqueous activator solutions A and B shown below were prepared.
In addition, the usage-amount of the following mixture A and B used as an activator for pollutant-degrading microorganisms is the quantity which the sum corresponds to 0.8 kg with respect to 1 kg of soil for evaluation. Moreover, the usage-amount of the mixture A and B was determined so that mass ratio (mixture A: mixture B) might be set to 1: 5.

<Activator aqueous solution A>
As an activator, 0.2 g of a mixture A of amino acid and carbohydrate (manufactured by Nippon Steel Engineering Co., Ltd., “NS Bioacty-CN1”) was diluted 50 times to prepare 10 mL of an aqueous activator solution A.

<Activator aqueous solution B>
As an activator, 1.0 g of a mixture B of amino acid and carbohydrate B (manufactured by Nippon Steel Engineering Co., Ltd., “NS Bioacty-CN2”) was diluted 50 times to prepare 10 mL of an activator aqueous solution B.

[Example 1]
<Preparation of column sample>
The column 41 shown in FIG. 2 was used for preparation of the column sample.
Column 41, the diameter _{d 1} of the upper 41a is 26cm, the diameter _{d 2} of the bottom portion 41b 22.5cm, the height _{h 1} is 25.5cm, the upper 41a has a released state. Further, as shown in FIG. 2, the bottom 41b has a raised bottom mesh structure (aperture 1 mm), which allows ventilation and water flow.
This column 41 was filled with gravel from the bottom 41 b to a position where the height h ₂ was about 6 cm, and this was used as the support layer 42. On the support layer 42 filled, as the bulk specific gravity is within a range of 1.5~2.0kg / L, the evaluation soil 43 in the height _{h 3} is approximately 15cm (corresponding to the filling volume 6.7 L) Thus, a column sample 40 was produced.
The mass of the soil for evaluation 43 packed in the column 41 was measured, and the bulk specific gravity was determined from the following formula (1). The results are shown in Table 1.
Bulk specific gravity [kg / L] = mass of the soil for evaluation packed in the column / packing volume (1)

About the obtained column sample 40, the field capacity of the soil for evaluation was measured in the following procedures.
First, the mass of the column sample 40 was measured. Subsequently, the column sample 40 was immersed in a bucket filled with water for 24 hours to saturate the evaluation soil 43 with water. Thereafter, the column sample 40 was lifted from the bucket and naturally drained for 24 hours. The mass of the column sample 40 after natural drainage was measured, and the field capacity was determined from the following formula (2). The results are shown in Table 1.
Field capacity [kg] = mass of column sample 40 after natural drainage−mass of column sample 40 before saturation (2)

  Moreover, about the column sample 40 after natural drainage, the moisture content of the soil for evaluation is made into a pF meter (made by Dairika Chemical Co., Ltd., “DIKI-8343”), and a soil moisture sensor (made by Decagon Co., Ltd., “Ecotic ECH2O probe”). EC-5 "), and the correlation with the field water volume determined by mass measurement was confirmed.

<Purification test>
In conducting the purification test, the management setting value of the water content of the soil for evaluation was set to “field water volume × 1.0”, the test period was set to 1 month, and the purification test was conducted as follows.
For the purification of the soil for evaluation, biostimulation using microorganisms that originally inhabit the contaminated soil was adopted. In addition, since the bottom 41b of the column 41 has a mesh structure and can be ventilated, air is always supplied to the evaluation soil. Therefore, the purification test is considered equivalent to biosparging.

For the column sample 40, the field water volume was measured, and after curing and reaching the management set value, the aqueous activator solution A (50 mL) was supplied to the surface of the soil 43 for evaluation.
After one week from the supply of the activator aqueous solution A, the activator aqueous solution B (250 mL) was supplied to the surface of the soil 43 for evaluation.
After one month from the supply of the aqueous activator solution A, the column 41 was disassembled, and the F-CN content of the evaluation soil was measured. In addition, before filling the column 41, F-CN content of the soil for evaluation was measured beforehand, and the purification rate was calculated | required from following formula (3). The results are shown in Table 1.
Purification rate [%] = {(F-CN content before purification test) − (F-CN content before purification test)} / (F-CN content before purification test) × 100 (3 )

In addition, during the purification test (one month after supplying the activator aqueous solution A), the mass of the column sample 40 was measured once a day, and the “saturation” obtained when the field capacity was measured from the measured value. The “mass of the previous column sample 40” was subtracted and used as the moisture content of the soil for evaluation. And when the value of the water content obtained by this mass measurement is 25% or more of the deviation from the previously set management setting value, it is determined that the water content is insufficient and the surface of the soil 43 for evaluation is set to the management setting value. Water was controlled by supplying water to the water.
In addition to measuring the moisture content of the soil for evaluation, the moisture content was also measured using a pF meter and a soil moisture sensor, and the correlation with the moisture content determined by mass measurement was confirmed.

[Examples 2 and 3]
Column samples were prepared in the same manner as in Example 1, and the field water capacity was measured for each column sample. The results are shown in Table 1.
A purification test was conducted in the same manner as in Example 1 except that the management set value of the moisture content of the soil for evaluation was changed to the value shown in Table 1. The results are shown in Table 1.

[Comparative Example 1]
Column samples were prepared in the same manner as in Example 1, and the field water capacity was measured for each column sample. The results are shown in Table 1.
A purification test was conducted in the same manner as in Example 1 except that the management set value of the water content of the soil for evaluation was changed to the value shown in Table 1 and the aqueous activator solutions A and B were not supplied. The results are shown in Table 1.

[Comparative Example 2]
Column samples were prepared in the same manner as in Example 1, and the field water capacity was measured for each column sample. The results are shown in Table 1.
A purification test was performed in the same manner as in Example 1 except that the management set value of the moisture content of the soil for evaluation was changed to the value shown in Table 1 and the moisture management was not performed. The results are shown in Table 1.

As is clear from Table 1, in each example, the F-CN content in the evaluation soil after the completion of the purification test was significantly reduced compared to that before the purification test, and the contaminated soil was sufficiently purified.
Among Examples 1 to 3, the value of the purification rate was the highest and excellent in purification was Example 2 in which water in the evaluation soil was controlled at a field water volume of 75% and an activator was added. .

By the way, in the field where the contaminated soil is actually purified, the moisture content of the contaminated soil is measured using a moisture meter such as a pF meter and a soil moisture sensor.
However, in this example, the moisture content of the soil for evaluation was measured by mass measurement from the viewpoint of being able to measure more accurately. Therefore, in addition to measuring the moisture content of the soil for evaluation, the moisture content was also measured with a pF meter and a soil moisture sensor, and the correlation with the moisture content determined by mass measurement was confirmed. The relationship was confirmed. Therefore, there is no problem even if the method for obtaining the moisture content by mass measurement is used as an alternative to the method for obtaining the moisture content using a moisture meter.

On the other hand, in the case of the comparative example 1 which did not supply activator aqueous solution, the purification rate of the soil for evaluation by a purification test was as low as 52.9%. That is, in Comparative Example 1, the contaminated soil was not sufficiently purified.
In the case of Comparative Example 2 in which moisture management was not performed, the purification rate was higher than that in Comparative Example 1, but the purification rate was lower than that in Example 2 where the conditions of the purification test other than moisture management were the same.

  10: Watering wheel, 20: Injection well, 21: Blower, 30: Suction well, 31: Blower, 40: Column sample, 41: Column, 42: Support layer, 43: Soil for evaluation, A: Surface layer, B: Not used Saturated zone, C: saturated zone, X: contaminated soil.

Claims (3)

Water or an aqueous solution containing an activator for pollutant-degrading microorganisms is supplied to the surface layer of unsaturated soil contaminated with pollutants, and the soil is infiltrated into the contaminated soil by natural flow. A method for position purification,
An in-situ purification method for contaminated soil, characterized in that the moisture content of the contaminated soil at an arbitrary depth in the unsaturated zone is measured with a moisture meter and the moisture content of the contaminated soil is managed.   2. The in-situ purification method for contaminated soil according to claim 1, wherein an injection well reaching or near the contaminated soil is provided, and air is injected from the injection well.   The in-situ purification method for contaminated soil according to claim 1 or 2, wherein a suction well reaching or near the contaminated soil is provided, and suction is performed from the suction well.

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