JPH11235580A - Restoring method of contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of purifying contaminated soil raised purification effect by microorganisms and contrived to improve efficiency of the construction method and shorten a term of work. SOLUTION: In a restoring method of the soil contaminated with contamination substance, this process comprises the step of freezing the soil, and the step of charging at least one selected from the microorganisms capable of decomposing the contamination substance, the inducer for realizing performance of the microorganisms provided with performance for decomposing the contamination substance, and nutrition for proliferation of the microorganisms capable of decomposing the contamination substance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for restoring an environment (for example, soil and groundwater) contaminated by pollutants (for example, hydrocarbons and halogenated hydrocarbons) using microorganisms.

[0002]

2. Description of the Related Art In recent years, it has been pointed out that hydrocarbons such as petroleum, aromatic hydrocarbons, paraffins and naphthenes contaminate the environment such as soil and groundwater. In particular, environmental pollution due to organic chlorine compounds such as trichloroethylene, tetrachloroethylene, tetrachloroethane, and polychlorinated biphenyl has been pointed out. Therefore, it is strongly desired to establish a technique for preventing the spread of pollution and restoring the polluted environment.

[0003] For example, various methods have been known and attempted as soil remediation methods for returning soil to its original state by removing contaminants from soil contaminated with contaminants. For example, restoration is performed mainly on physical and chemical methods such as a vacuum extraction method, a solar drying method, an aeration treatment method, and an oxidation treatment method.

[0004] On the other hand, a method for remediating the environment using a microorganism capable of decomposing contaminants (bioremediation) has been studied. One of the typical methods of bioremediation is a so-called indigenous bacteria activation method that promotes the purification by promoting the growth of microorganisms capable of decomposing contaminants in contaminated soil and the development of decomposition activity [US4 , 401, 569 (Groundwate
r Technology Systems, Inc.), etc., and has already been put into practical use for petroleum-based pollution. Another typical method of bioremediation is to contaminate a microorganism capable of decomposing a contaminant alone, or together with an inducer that expresses the decomposing activity of the microorganism and / or nutrients for growing the microorganism. There is a method to put it in the environment where it was used. Compared with conventional physical and chemical methods, such a purification method can be repaired with lower energy, the equipment is simpler, and it is possible to repair low-concentration polluted environments that are difficult with physical and chemical methods It is.

[0005] In such bioremediation, it is necessary to inject microorganisms, inducers, nutrients and the like into the environment. At this time, how uniformly these substances can be injected into the contaminated environment is one of the important requirements that determine the efficiency of bioremediation.

There have been several disclosures about injection of substances and the like necessary for purification. For example, US Pat. No. 5,133,625 describes a method for controlling injection pressure by measuring injection pressure, flow rate and temperature using an expandable injection pipe. This method controls the concentration of microorganisms, nutrients, and the like by injection pressure to maintain the activity of decomposing microorganisms optimally, and is mainly intended to control the purification step by microorganisms. Also,
US Patents US 4,442,895 and US 5,033
2,042 proposes injecting a gas or a chemical solution into the soil from an injection well to crack the soil, and states that oxygen and nutrients required for microbial purification can be supplied at that time. .

On the other hand, as a method for intensively purifying a high-concentration contaminated region for the purpose of achieving efficient microorganism purification in a short time, there is known a method of limiting the injection range of microorganisms, nutrients and the like. . For example, US Pat. No. 5,111,8
No. 83 describes a method of injecting a chemical solution into a predetermined region in the horizontal and vertical directions of soil based on the relative positions of an injection well and an extraction well. This aims at injecting a chemical solution into a predetermined position in the soil by a geometric method, and is considered to be an effective method for limiting a repair area even in microbial purification.

Further, as a method of injecting a microorganism or a substance for maintaining a decomposing activity into a limited area from an injection well, an impermeable layer is formed at a soil position at a predetermined distance from the injection well, and this is used as a barrier wall. A method of limiting the implantation region has also been considered. For example, in the ground
There is known a method of laying a floor, providing an asphalt layer, or injecting a treatment agent such as cement, water glass, urethane, acrylamide, or acrylate into soil. Specifically, Japanese Patent Publication No. 2-266662 and Japanese Patent Publication No. 5
No. -27676 describes a method of forming an impermeable layer at a predetermined position in soil using a water-soluble polymer insolubilized by ions in soil. This method controls mass transfer using an impermeable layer as a barrier, and may be a technique for limiting the injection area in the step of injecting microorganisms, nutrients, and the like into soil. Attempts have been made to efficiently and uniformly inject a chemical solution into a specific region by means of limiting such a region.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above background art, and an object of the present invention is to repair soil contaminated with contaminants by bioremediation in the soil. A microorganism capable of decomposing the substance, an inducer for causing the microorganism capable of decomposing the contaminant to exhibit the resolution of the contaminant, and at least one nutrient of the microorganism capable of decomposing the contaminant is widely distributed in the soil. The purpose is to make

[0010]

One embodiment of the method for repairing soil contaminated with a contaminant according to the present invention, which can achieve the above object, comprises a step of freezing the soil and a method of contaminating the soil with the contaminant. Selected from microorganisms capable of decomposing the contaminant, inducers expressing the ability of the microorganism having the ability to decompose the contaminant, and nutrients for the growth of the microorganism capable of decomposing the contaminant in the soil obtained. The method has a step of inputting at least one.

According to the present invention, in the course of experiments in which the present inventors decompose contaminants in soil using microorganisms, microorganisms capable of decomposing contaminants after freezing contaminated soil filled in a predetermined container are used. It was made based on the finding that the injection of a liquid containing water significantly improved the decomposition efficiency of pollutants in soil. The reason why the efficiency of soil restoration is improved by this embodiment is not clear, but possible reasons include the following.

[0012] The reason why such an improvement in characteristics is obtained is that the water retained between the soil particles is temporarily frozen by freezing the ground, and then the step of gradually cooling the water is performed as a pretreatment, so that the freezing and expansion between the soil particles is performed. To expand the fine area of the soil where the infused drug solution containing degrading microorganisms, nutrients and additives is diffused, and to contact the infused drug solution by agitation of the retained water between the soil particles by freezing and thawing Is to promote. As will be described later, a freezing method is known in civil engineering work. In the ground containing fine particles, freezing and expansion occur due to freezing, and dehydration and consolidation occur during thawing. The present invention has clarified that such a change in the ground is a problem to be overcome in civil engineering work, but is a very suitable change for the distribution of microorganisms. That is, the present invention, by performing this step as a pretreatment, secures a space for decomposed microorganisms to enter, increases the frequency of contact with contaminants, and consequently increases purification efficiency and shortens the purification period. It is made possible.

[0013]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

A container 1 for a chemical solution to be injected, an injection system 2 including a pump, a flow meter, and the like, a refrigerant supply source 4 and a supply device 3 thereof are placed in a contaminated soil restoration area 7 set in advance based on information such as a boring survey. prepare. A tube 5 containing a freezing tube for supplying a refrigerant and an injection tube for injecting a chemical solution is built in each of the wells 8 excavated in the restoration area 7. If the injection tube and the freezing tube are built in the same well as shown in the figure, it is convenient to overlap the freezing region 6 and the injection region. However, if both regions overlap, it is possible to build them independently in separate wells. I do not care. In addition, as described later, by setting the injection tube to be able to select the depth of the injection port and semi-fixed so that the depth of the cryotube can be changed, the depth of the freeze and the injection site can be arbitrarily selected, Further, the present purification method can be applied while changing the position in the depth direction.

For freezing the soil, for example, a method of freezing the soil using brine or liquid nitrogen used in civil engineering works or the like is used. Specifically, an antifreeze solution (aqueous calcium chloride solution) called brine is stored at -20 to -30 ° C.
Brine method of cooling the ground and cooling the ground by sending it to a freezing tube by a circulation pump can be used. The brine whose temperature has risen due to the freezing of the ground can be continuously frozen by returning to a freezing system including a compressor, a condenser, and a cooler and cooling.

In the case of using liquid nitrogen (vaporization temperature -196 ° C.), a liquid nitrogen method is used in which a liquid nitrogen-containing cylinder or tank truck is used to prepare liquid nitrogen, and the liquid nitrogen is poured directly into a freezing tube and cooled by the heat of vaporization of nitrogen. You can also.

Each method is a freezing method employed in civil engineering works, and the same equipment can be diverted, which is convenient.

In the thawing step, either of a method of thawing by allowing it to stand naturally and bringing it to room temperature or a method of rapidly thawing in a heating step may be used. Although not shown in FIG. 1, it is also effective to similarly install a heating tube to accelerate the thawing process. Alternatively, thawing may be performed by injecting warm water or the like from an injection tube.

In this embodiment, even when the ground is frozen, it is possible to inject a drug solution containing microorganisms and the like, and it is also possible to inject while freezing at the temperature of the drug solution, so that the thawing step is not essential. If the degrading characteristics of the microorganism are in a lower temperature range than usual, it is advantageous that the microorganism is partially frozen.

Although the above-described configuration is obtained by excavating a well, the present invention is not limited to such an embodiment.
That is, it is easier to perform the freezing and thawing processes on the surface soil, and in this case, the purification efficiency can be naturally improved. In addition to the method of freezing the ground using a freezing tube or the like, the method of freezing the ground is not limited, since a refrigerant may be directly added or sprayed.

Although not shown in FIG. 1, in order to cause a crack in the contaminated ground, the ground layer causing the crack is
Cracking can be performed by installing an injection pipe for projecting water or air, and opening it after pressurization.

The method of the present invention is not particularly limited to the type of contamination, but is very effective for contaminants present in the aqueous phase between soil particles or between particles. Examples of such contaminants include trichlorethylene, tetrachloroethylene, dichloroethylene, PCBs and the like with organochlorine compounds,
Alternatively, oils, petroleum hydrocarbons, aromatic hydrocarbons and the like are included.

The chemicals to be added include decomposed microorganisms, nutrients including carbon, phosphorus, nitrogen, etc. necessary for maintaining the growth and activity of the decomposed microorganisms, inducers of decomposing enzymes, oxygen and other trace chemical substances, surfactants, and others. Consists of a part or all of the additives. In addition, since it is not required that the decomposed microorganism is aerobic or anaerobic, the type of the decomposed microorganism is not limited, and it does not depend on whether it is an indigenous microorganism or an exogenous microorganism.

The exogenous microorganism at the time of injection may be either a quiescent cell or a growing cell. The degrading microorganisms used may be any as long as they have a degrading ability, and are not limited to those isolated and identified. There is no problem at all.

As a report isolated as a specific TCE-degrading bacterium, welchia alkenophilasero 5 (USP 487773)
6, ATCC 53570), Welchia alkenophila sero 33 (USP 4
877736, ATCC 53571), Methylocystis sp.strain M (A
gric. Biol. Chemi., 53, 2903 (1998), Biosci. Biote
ch. Biochem., 56, 486 (1992), 56, 736 (1992), Meth
ylosnus trichosprium OB3b (Am. Chem. Soc. Natl. Me
et. Dev. Environ. Mictrbiol., 29, 365 (1989), App
l. Environ. Microbiol., 55, 3155 (1989), Appl. Bio
Chem. Biotechnol., 28, 877 (1991), JP-A-02-9
2274, Japanese Patent Application Laid-Open No. 03-292970),
Methylomonas sp. MM2 (Appl. Eviron. Microbiol., 5
7, 236 (1991), Alcaligenes denitrificans ssp.xylo
soxidans JE75 (Arch.Microbiol., 154, 410 (1990)),
Alcaligenes eutrophus JMP134 (Appl.Environ.Micr
obiol., 56, 1179 (1990), Mycobacterium vaccae JOB5
(J. Gen. Microbiol., 82, 163 (1974), Appl. Enviro
n. Microbiol., 54, 2960 (1989), ATCC 29678), Pseud
omonas putida BH (Sewerage Association Journal, 24, 27 (1987), Ps
eudomonas sp.strain G4 (Appl.Environ.Microbio
l., 52, 383 (1986), 53, 949 (1987), 58, 951 (19
89), 56, 279 (1990), 57, 193 (1991), USP492580
2, ATCC 53617, which was originally classified as Pseudomonas cepacia, but was changed to Pseudomonas sp.), Ps
eudomonas medocina KR-1 (Bio / Techol., 7, 282 (198
9)), Pseudomonas putida F1 (Appl.Eviron.Microbio
l., 54, 1703 (1988), 54, 2578 (1988)), Pseudomon
as fluorescens PFL12 (Appl.Environ.Microbiol., 5
4, 2578 (1988)), Pseudomonas putida KW1-9 (JP-A-06-70753), Pseudomanas cepacia KK01
(Japanese Unexamined Patent Publication No. 06-227770), Nitrosomonas e
uropaea (Appl.Environ.Microbiol., 56, 1169 (199
0)), Lactobacillus vaginalis sp.nov (Int.J. Sys
t. Bacteriol. 39, 368 (1989), ATCC 49540) and the like.

In addition, strain J1 which is a microorganism that decomposes organochlorine compounds such as trichloroethylene (an international deposit number based on the Butabest Treaty: FERM BP-5102)
A strain JM1 (FERM BP-5352) which is a strain of the strain and which does not require an inducer (inducer) required for the decomposition of an organochlorine compound can be used.

[0027] Examples of petroleum hydrocarbon and aromatic hydrocarbon degrading bacteria include Pseudomonas; Flavobacterium;
iqenes; and Achromobacter; or gram-positibe rods
And cocci eg; Brevibacterium; Corynebacterium; A
rthrobacter; Bacillus; and Micrococcus;
Others include Mycobacterium; Nocardia; Streptomyces. In addition, marine yeast Candida sp. (Candida sp.) S1EW1 strain (FERM P-13871), and commercial bacteria such as PETROBAC (POLYBA
C CORPORATION), HYDROBAG (POLYBAC CORPORATION), MI
CRO PRO “TPH” (POLYTBAC CORPORATION), BI-CHEM DC
2000GL (SYBRONCHEMICALS INC.), BI-CHEM DC 2001 LN
(SYBRON CHEMICALS INC.), ABR (SYBRONCHEMICALS IN
C.), H-10 (Bio-Rem), BioGEE (BioGEE), LRC-1 (LRC T
echnologies), ERS Formula (Environmental Bio-Remed
iation International Corp.). These microorganisms can be used in the present invention.

Further, depending on the microorganism, methane or the like may be assimilated, and it is effective to inject methane gas. For aerobic microorganisms, it is also effective to supply air and supplement oxygen.

When injecting through a well, a chemical solution can be easily fed by applying pressure from an injection tube.

FIG. 2 is a schematic diagram showing another embodiment of the implementation of the present invention.

As in the case of FIG. 1, the apparatus comprises a container 1 for a chemical solution to be injected, a pump for sending water or air and a chemical solution, a flow meter, etc., to a contaminated soil restoration area 7 set in advance based on information such as a boring survey. An injection system 2 and a pressurized injection tube 23 of air or water are prepared. Further, the coolant supply source 25
And a supply device 24 thereof, and a freezing tube 26 for supplying a refrigerant and an injection tube 23 for injecting a chemical solution are erected in the well drilled in the restoration area 7, respectively. In addition, as described below, by setting the injection tube to be able to select the depth of the injection port and semi-fixed so that the depth portion of the freezing tube can be changed, the depth of the freeze and the injection site can be arbitrarily selected, Further, the present purification method can be applied while changing the position in the depth direction. In this figure, a pressure injection tube for crack formation,
Although the chemical injection tube for activating the microorganism is shown by the same injection tube, it may be easily separated separately.

Further, as shown in FIG. 2, a packer 10 capable of setting the injection depth is provided, and the injection position can be selected by using an injection pipe capable of injecting the rubber sleeve 11 as a projecting hole from the double packer pipe. It is convenient because it also serves as a drug solution injection. The injection amount and injection pressure of the chemical solution may be set according to the soil properties of the ground to be injected and a desired injection region.

[0033]

The present invention will be described in detail with reference to the following Examples, which do not limit the present invention in any way.

Example 1 Glass vial (68 m
In l), 100 g of fine sand was placed, compacted from above with a glass rod, and trichlorethylene (TCE) saturated water was added to an initial concentration of about 10 ppm. After sealing with Teflon liner-butyl rubber stopper and aluminum cap, about 2
Saved for a week. Ten similar soil samples were prepared.
Acetone and dry ice were placed in a container, and vials of 5 out of 10 soil samples were immersed in the container until the soil was frozen. Thereafter, a soil sample was taken out from the dry ice / acetone and left at room temperature. The JM1 strain (FERM BP-5352) was transformed with an M9 medium containing 0.5% sodium glutamate (Na ₂ HPO ₄ , 6.
2 g; KH ₂ PO ₄ , 3.0 g; NaCl, 0.5
g ;: NH ₄ Cl, 1.0 g) at 15 ° C. with shaking.

To all of the 10 frozen and unfrozen soil samples, 10 ml of the cultured bacterial solution is placed in a syringe, and the same amount of syringe is inserted into the compacted soil of each vial and injected.
Gas phase TC in the headspace of each soil sample vial
E was sampled with a gas tight syringe, and the sample was subjected to gas chromatography (Shimadzu Gas Chromatograph GC-14B: FI
D detector), the TCE concentration was measured every hour immediately after the injection of the bacterial solution (headspace method). The time when the TCE remaining amount was 0.1 ppm or less for each of the five frozen and unfrozen samples was determined and averaged. The average was 9.2 hours for the frozen sample and 13.8 hours for the unfrozen sample.
The results showed that the decomposition time of the frozen soil sample was faster than that of the unfrozen sample.

[Embodiment 2] TCE was performed in the same manner as in Embodiment 1.
Soil sample 10 filled with soil contaminated with
Books were prepared, and five of them were used as frozen samples in the same manner as in Example 1.

Next, the JMC1 strain (FERM BP-5960) was cultured in the same manner as the JM1 strain used in Example 1, and the resulting bacterial solution 1
0 ml was injected into each frozen sample using a syringe when the soil was frozen. 10 ml of the bacterial solution containing the JMC1 strain was injected into each of the unfrozen samples using a syringe.

All soil samples injected with the bacterial solution were kept at 5 ° C.
And the amount of TCE in each soil sample was measured every hour using the headspace method. And the TCE concentration of each soil sample is 0.1p
The time required to reach pm or less was obtained, and the average value of the frozen sample and the unfrozen sample was calculated. The result was 19.4 hours for the frozen sample and 24.8 hours for the unfrozen sample. From this, it is clear that the soil repair efficiency in the frozen sample is high.

Example 3 Phenol was added to fine sand having a water content of 12% to a concentration of about 200 ppm.
The fine sand is filled into 10 beakers of 100 ml each in an amount of 50 g. Five of these were soil-frozen in the same manner as in Example 1, and then allowed to stand at room temperature. 20 ml of a phenol-degrading bacterium Pseudomonas cepacia KK01 (FERM BP-4235) cultured in an M9 medium supplemented with 0.05% yeast extra (a bacterial concentration of about 10 ⁸ cfμ / ml) was added to the soil sample beaker, Every hour, the phenol concentration of the sand is determined by the JIS method (JIS K012-1933, 2).
8.1) Determined in accordance with The time required for the phenol concentration to reach 0.05 ppm was determined and averaged. The average was 21.4 hours for the frozen sample and 2 for the unfrozen sample.
It was 3.8 hours. Also in this case, it was shown that the decomposition efficiency was increased by freezing.

Example 4 (Test Tank) As shown in FIG. 3, a gravel layer 19 was provided in a lower layer (0.1 m) of a cylindrical test tank 13 (drum: about 300 mm in radius, about 850 mm in height). Then, a mixed soil of fine sand and silt containing 10 ppm of trichlorethylene (mixing ratio: fine sand: silt = 8: 2) was filled thereon to form a contaminated soil layer 14. Simultaneously with the filling of the soil, the freezing tube 15 into which the liquid nitrogen can be poured and the injection tube 16 which is opened at four lateral surfaces and whose periphery is covered with a rubber sleeve are both provided. So built. Also,
Two stainless steel tubes 17 and 18 having an inner diameter of 1/16 inch covered with a stainless mesh at the tip were placed 1 mm from the side wall of the tank.
It was built at 0 cm and used as a gas phase sampling tube in the soil. The upper part of the test tank is provided with a gravel layer 19 and covered. The lid is provided with a valve for releasing internal pressure, and is opened at the time of freezing or injection of the bacterial solution. Except that the freezing tube 15 is not built, a tank exactly the same as the above-mentioned test tank is prepared and used as a control tank.

After the test soil is frozen by flowing liquid nitrogen through the freezing tube of the test tank, the soil is left to thaw.

(Injection and Measurement of Bacterial Solution) The JM1 strain was set to have the same culture conditions as in Example 1, and a 50-liter jar fermenter (Mitsuwa Biosystems: KM) was used.
J-501MGU-FPMI1). The cells were collected by centrifugation at the 45th hour of the late logarithmic growth, and resuspended in an M9 medium without an equivalent amount of carbon source to obtain an inoculated bacterial solution comprising resting cells.

A total of 20 liters of the bacterial solution is injected into the test tank and the control tank from the injection tube via the liquid sending pump within a range of 1 to 10 liter / min. After that, trichlorethylene is supplied to the detector tube (Gastec,
132L) by sampling the gas in the soil. The results are shown in FIG. In this figure, ○ indicates the average of the sampling values at two locations in the freezing test tank, and □ indicates the average of the sampling values at two locations in the control test tank. From this result, it became clear that the frozen test tank decomposed TCE earlier and the decomposition efficiency increased.

[Embodiment 5] This embodiment is intended for a contaminated soil caused by petroleum pollution as the contaminated soil remaining in the ground, and has a freezing tube into which liquid nitrogen can be poured and four lateral surfaces. Both pressurized injection tubes, which were open and covered with a rubber sleeve, were introduced into the contaminated soil. After the test soil was frozen by flowing liquid nitrogen, compressed air was instantaneously and repeatedly sent from the pressure injection tube. Then, it was left to wait for natural thawing of the soil.

The petroleum-degraded microbial preparation HYDROBAG (POLYBAC CO
RP.) Was adjusted to 100 g per liter of water, and the nutrient source was adjusted so that C: N: P was 100: 10: 1. 800 liters of this microorganism liquid was injected from a pressure injection tube. In addition, air was sent from the pressure injection tube for about 5 hours every day. One month later, soil sampling was performed from 10 sites in the target contaminated soil, and their TPH values (Total petroleum hy
drocarbon concentrations) were measured according to EPA8015M.

The TPH value of the target soil before purification of the contaminated soil is 12
Although it was 200 ppm, the contaminated soil due to petroleum-based contamination was reduced to 97.8 to 9 by the method for purifying contaminated soil according to the present invention.
It was found to remove 9.5%, on average about 99%.

[Comparative Example 1] In a contaminated soil layer similar to that in Example 5, only a pressurized injection pipe whose four side surfaces were opened and whose periphery was covered with a rubber sleeve was introduced into the contaminated soil.

The petroleum-degraded microbial preparation HYDROBAG (POLYBAC CO
RP.) Was adjusted to 100 g per liter of water, and the nutrient source was adjusted so that C: N: P was 100: 10: 1. 800 liters of this microorganism liquid was injected from a pressure injection tube. In addition, air was sent from the pressure injection tube for about 5 hours every day. One month later, soil sampling was performed from 10 sites in the target contaminated soil, and their TPH values (Total petroleum hy
drocarbon concentrations) were measured according to EPA8015M.

The TPH value of the target soil before purification of the contaminated soil is 13
Although it was 200 ppm, the contaminated soil due to petroleum-based contamination was reduced to 77.8 to 9 by the method for purifying contaminated soil according to the present invention.
It was found to remove 6.5%, on average about 92%.

As is evident from the results of Example 5 and Comparative Example 1, the method for purifying contaminated soil according to the present invention can purify petroleum-based contaminated soil by 99% or more, and in particular, enables uniform purification. .

Example 6 (Test soil) Mixed soil of fine sand and silt (mixing ratio; fine sand:
Silt = 8: 2) N as a pollutant for 100 g
Hexadecane was mixed at a rate of 0.2 g to prepare a model of contaminated soil. To this contaminated soil was added 50 mg of yeast ectolact and left at room temperature for one month. As a control, a contaminated soil to which no yeast extract was added was also prepared and similarly left at room temperature for one month. N-hexadecane in each contaminated soil was extracted using N-hexane, and N-hexadecane was extracted from the contaminated soil using gas chromatography by the TCD method.
-The amount of hexadecane was measured. As a result, it was found that N-hexadecane was decomposed earlier in the contaminated soil to which yeast extract was added. This indicates that microorganisms that degrade N-hexadecane exist in the soil used in this experiment.

(Test tank) Next, as shown in FIG. 4, a cylindrical test tank 13 (drum: about 300 mm in radius, about 8 in height)
A gravel layer 19 was provided in the lower layer (0.1 m) of 50 mm), and the contaminated soil prepared in the same manner as described above was filled thereon to obtain a contaminated soil layer 14 of the model. Simultaneously with the filling of the soil, the freezing tube 15 into which the liquid nitrogen can be poured and the injection tube 16 which is opened at four lateral surfaces and whose periphery is covered with a rubber sleeve are both provided. So built. Except that the freezing tube 15 was not built, the same tank as the above-mentioned test tank was prepared and used as a control tank.

After the test soil was frozen by flowing liquid nitrogen through a freezing tube of the test tank, the soil was thawed by leaving it to stand. Furthermore, compressed air was repeatedly and instantaneously sent from the pressurized injection tube to the test tank.

(Injection and Measurement of Chemical Solution) A nutrient source having a ratio of 50 mg of yeast ethoxtrast in 1 liter of water is prepared. In each of the test tank and the control tank, 5 liters of this nutrient solution is injected from a pressure injection tube. Thereafter, the water is poured from the drain 20 at the bottom of the tank to the water collected at the bottom. Air is sent from the pressurized injection tube for about 5 hours every day. After repeating this for 30 days, soil was sampled from the test tank and the control tank, and residual N-hexadecane in the soil was measured in the same manner as described above. Table 1 below shows the remaining amount in the soil sampled from approximately 10 locations in the test tank and control tank.
The measured value is shown as the remaining amount in 100 g of soil.

(Test results)

[0056]

[Table 1] Residual oil amount (g) From the above results, it can be seen that the efficiency of decomposing contaminants is improved by injecting nutrients after freezing and thawing the contaminated soil.

Example 7 A contaminated soil to be treated was sampled, and 100 g of the soil was treated with 50% yeast extract.
mg was added and left for one month. At the same time, samples without the addition of yeast extract, a nutrient source, were prepared. In both soils, the TPH value (Total petroleum hydroc
arbon concentrations) were measured according to EPA8015M. From the comparison of the TPH values of both soils, it was confirmed that the petroleum contamination of the soil to which the nutrient was added was reduced more quickly. This confirmed that microorganisms capable of decomposing petroleum pollutants in the soil were present in the treated control contaminated soil.

Next, as in Example 5, both the freezing tube and the pressure injection tube were introduced into the contaminated soil. Liquid nitrogen was flown to freeze the soil, and compressed air was instantaneously and repeatedly sent from the pressure injection pipe. Thereafter, the soil was naturally thawed.

Next, a nutrient source was prepared so that the ratio of yeast extract was 50 mg per liter of water. 800 liters of this nutrient solution was injected from a pressure injection tube. Air was sent from the pressurized injection tube for about 5 hours every day. 1
After a month, soil sampling was performed at 10 sites in the target contaminated soil, and their TPH values (Total petroleum hydrocarbonc
oncentrations) were measured according to EPA8015M.

The TPH value of the target soil before purification of the contaminated soil is 32.
Although it was 00 ppm, the contaminated soil due to petroleum-based contamination was reduced to 92.8 to 9 by the method for purifying contaminated soil according to the present invention.
It was found to remove 7.5%, on average about 96%.

[Comparative Example 2] In a contaminated soil layer similar to that of Example 7, only a pressurized injection pipe with four lateral sides opened and the periphery thereof covered with a rubber sleeve was introduced into the contaminated soil.

Yeast extract 5 in 1 liter of water
The nutrient source was adjusted to be 0 mg, and 800 liters of this nutrient solution was injected from a pressure injection tube. Also, every day 5
Air was sent from the pressure injection tube for about an hour. One month later,
Soil was sampled from 10 sites in the control contaminated soil, and its TPH value (Total petroleum hydrocarbon concentrat
ions) was measured according to EPA8015M.

The TPH value of the target soil before purification of the contaminated soil is 31.
Although it was 80 ppm, according to the purification method of this comparative experiment, the contaminated soil due to petroleum-based contamination was reduced to 77.6 to 97.3.
%, On average about 83%.

As is clear from the results of Example 7 and Comparative Example 2, it is understood that the method for purifying contaminated soil of the present invention can purify 90% or more of petroleum-based contaminated soil, and in particular, uniform purification. .

Example 8 Trichloroethylene (TC
The soil to be treated due to the contamination of E) was sampled, and the soil to be treated was left under a 2% methane gas atmosphere for one month. Further, a sample to which methane gas was not added was also prepared at the same time, and after one month, the TCE concentration in the soil was measured for both soils. From the comparison of the TCE concentrations in both soils, it was confirmed that the soil in which methane was present reduced TCE contamination more quickly. This confirmed that microorganisms capable of decomposing trichlorethylene in the soil were present in the contaminated soil to be treated.

Next, as in Example 5, both the freezing tube and the pressure injection tube were introduced into the contaminated soil. Liquid nitrogen was flown to freeze the soil, and compressed air was instantaneously and repeatedly sent from the pressure injection pipe. Thereafter, the soil was naturally thawed.

To this soil, 2% methane gas was sent at a rate of 50 liter / min from the pressurized injection tube for about 5 hours every day.
Three months later, soil water was sampled from 10 sites in the target contaminated soil. The sampled liquid is immediately n-hexane
Put into a 5ml container and stir for 3 minutes, then n-hexane
Separate the layers and use TCD by ECD gas chromatography.
The amount was measured.

The TCE value of the target soil before purification of the contaminated soil is 1.
Although it was 2 ppm, by the method for purifying contaminated soil according to the present invention, 92.8 to 98.
It was found to remove 5%, on average about 96%.

[Comparative Example 3] In the same contaminated soil layer as in Example 8, only a pressurized injection pipe whose four side surfaces were opened and whose periphery was covered with a rubber sleeve was introduced into the contaminated soil.

About 2 hours each day, 2% methane gas was fed at a rate of 50 liter / min from the pressure injection tube. Three months later, soil water was sampled from 10 sites in the target contaminated soil. The sampled liquid was immediately placed in a container containing 5 ml of n-hexane, stirred for 3 minutes, and the n-hexane layer was separated, and the TCE amount was measured by ECD gas chromatography.

The TCE value of the target soil before purification of the contaminated soil is 1.
Although it was 2 ppm, according to the purification method of this comparative experiment, the contaminated soil due to TCE contamination was 82.6 to 97.3.
%, About 89% removal on average.

As is clear from the results of Example 8 and Comparative Example 3, it can be understood that the method for purifying contaminated soil according to the present invention can purify 90% or more of the contaminated soil of TCE, and in particular, can uniformly purify the soil.

Example 9 The same experiment as in Example 1 was carried out except that a mixed soil of fine sand and silt (fine sand: silt = 2: 8) was used.
The time when the remaining amount of TCE became 0.1 ppm or less was determined for each of these, and the average value was calculated. The result was 14.3 hours for the frozen sample and 20.5 hours for the unfrozen sample. This indicated that the decomposition time of the frozen soil sample was faster than that of the unfrozen sample.

Example 10 The same experiment as in Example 2 was carried out except that a mixed soil of fine sand and silt (fine sand: silt = 2: 8) was used. The time required for the TCE concentration to become 0.1 ppm or less was determined, and the average value was calculated. As a result, the frozen sample was 21.4 hours and the unfrozen sample was 2
It was 8.6 hours. Also in this case, it was shown that the decomposition time was shorter for the frozen sample.

Example 11 The same experiment as in Example 3 was carried out except that a mixed soil of fine sand and silt (fine sand: silt = 2: 8) was used, and a frozen sample and an unfrozen sample were used. The time required for the phenol concentration to reach 0.5 ppm was determined, and the average value was calculated. As a result, the frozen sample was 31.5 hours, and the unfrozen sample was 31.5 hours.
8.2 hours. Also in this case, it was shown that the decomposition efficiency was increased by freezing.

Example 12 An experiment was conducted in the same manner as in Example 4 except that the mixing ratio of fine sand and silt was set to 2: 8. A mixed soil of fine sand and silt containing 10 ppm of trichlorethylene (mixing ratio; fine sand: silt = 2: 8) was filled, and the same measurement as in Example 4 was performed as a contaminated soil layer of the model. FIG. 6 shows the result. In FIG.
Indicates the average of the sampling values of two places in the freezing test tank, and □ indicates the average of the sampling values of two places in the control test tank. From these results, it has been clarified that even in clay soil with a lot of silt, by injecting the microorganism after the freezing step, the microorganism can be distributed uniformly and TCE can be decomposed efficiently.

Example 13 An experiment similar to that of Example 6 was performed except that the mixing ratio of fine sand and silt in the mixed soil used in Example 6 was adjusted so that fine sand: silt = 2: 8. went. The results are shown in Table 2 below.

[0078]

[Table 2] Residual oil amount (g) From the above results, it can be seen that even in the case of clay soil, the decomposition efficiency of contaminants can be improved by freezing the soil before injecting nutrients.

[0079]

According to the present invention, after the step of freezing the contaminated ground area, the microorganisms for decomposing the contaminants and / or a chemical solution or gas necessary for decomposing the microorganisms are injected to increase the efficiency of the microbial purification. In addition, it has become possible to increase the efficiency of the construction method and shorten the construction period.

Further, according to the present invention, a step of freezing a contaminated ground area, a step of thawing the frozen ground, and a step of generating a crack in the ground by applying pressure to the ground are performed. The effect of the chemical solution or gas that enhances the decomposition activity has become remarkable, the efficiency of purification of microorganisms has increased, and it has become possible to realize more efficient construction methods and shorter construction periods.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a first embodiment according to the present invention.

FIG. 2 is a schematic explanatory view of a second embodiment of the soil repair method according to the present invention.

FIG. 3 is a schematic sectional view of a test tank used in Example 4.

FIG. 4 is a schematic sectional view of a test tank used in Example 6.

FIG. 5 is a graph showing the change over time in the concentration of trichlorethylene in a test tank and a control tank in Example 4.

FIG. 6 is a graph showing changes over time in trichlorethylene concentrations in a test tank and a control tank in Example 12.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container 2 Injection system 3,24 Supply device 4,25 Refrigerant supply source 5 Tube 6 Freezing area 7 Repair area 8 Well 9 Sleeve tube 10 Packer 11 Rubber sleeve 12,23 Injection tube 13 Test tank 14 Contaminated soil layer 15,26 Freezing Pipe 16 Injection pipe 17, 18 Pipe 19 Gravel layer 20 Drain 23 Pressure injection pipe 26 Freezing pipe

Claims (12)

[Claims] 1. A method for repairing soil contaminated with contaminants, comprising: (i) freezing the soil;
i) at least one selected from a microorganism capable of decomposing the contaminant, an inducer expressing the ability of the microorganism having the ability to decompose the contaminant, and a nutrient for growing the microorganism capable of decomposing the contaminant; A method for soil remediation comprising the step of dosing. 2. The method according to claim 1, wherein said step (i) is performed prior to step (ii). 3. The step (i) and the step (ii)
3. The method of claim 2, further comprising the step of thawing the frozen soil between. 4. Between said steps (i) and (ii),
3. The method of claim 2, further comprising the step of applying pressure to the frozen soil. 5. The method according to claim 1, wherein the soil comprises an indigenous microorganism inducibly provided with the ability to degrade the contaminant, and the step (i)
The method according to claim 1, wherein i) is a step of introducing at least one of an inducer for causing the indigenous microorganisms to express the contaminant decomposability and a nutrient for growing the indigenous microorganisms into the soil. 6. The method according to claim 1, wherein the microorganism capable of decomposing the contaminant is a microorganism constitutively expressing the ability to decompose the contaminant. 7. The contaminant is an aromatic compound or a chlorinated aliphatic hydrocarbon compound, and the microorganism is JM1
The method according to claim 6, which is a strain (FERM BP-5352). 8. The method according to claim 8, wherein the contaminant is an aromatic compound or a chlorinated aliphatic hydrocarbon compound, and the microorganism is JMC.
7. The method according to claim 6, wherein the strain is one strain (FERM BP-5960). 9. The method according to claim 7, wherein the aromatic compound is phenol, toluene or cresol. 10. The method according to claim 7, wherein the chlorinated aliphatic hydrocarbon compound is dichloroethylene or trichloroethialen. 11. The method according to claim 1, wherein the nutrient is a carbon source that can be assimilated by the microorganism. 12. The method of claim 1, wherein said nutrient is a gas.