JPH09276835A - Purification of contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a problem of secondary pollution, in purifying contaminated soil at a position lower than a ground water level, by arranging water pumping-up equipments sucking underground water up to a position lower than a contaminated stratum in a state surrounding a contaminated region and passing contaminated air through a bacteria decomposing region to purify the same to discharge purified air from the ground. SOLUTION: A plurality of water pumping-up equipments 1 are connected to a pump 3 in a state surrounding a contaminated region (c) so that the respective leading points of them are set to a position lower than the contaminated region (c). Sand columns 4 high in voids are formed around the water pumping-up equipments and air injection pipes covering the surfaces of the sand columns 4 are connected to the exhaust port of a pump 7 to supply air to the contaminated region (c) from the pump 7 through the sand columns 4. Further, an injection pipe 8 is connected to a decomposing bacteria soln. tank 16 and a bacteria activating soln. tank 17 to inject bacteria and a bacteria activating substance into the contaminated region (c) from an injection port. The part of the injection pipe 8 above the injection port is also covered with a sand column 9 and the suction pipe 10 covering the surface of the sand column 9 is connected to the suction port of the pump 7 to suck air in the ground.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for cleaning contaminated soil existing at a position deeper than the groundwater level.

[0002]

2. Description of the Related Art The rapid progress of science and technology in recent years has produced a large amount of chemical substances and chemical products. Many of these pollute nature as they gradually accumulate in the environment. Above all, considering that the land area, where human beings live, is most likely to be affected by human pollution and environmental water circulates,
Environmental pollution in the land area is a serious problem that spreads to the global level. Well-known soil (terrestrial) pollutants include hydrocarbons such as gasoline, organochlorine compounds such as PCBs, teratogenic pesticides such as dioxins, and volatile substances such as toluene, xylene, and benzene. Examples include organic solvents. In particular, organochlorine compounds such as trichlorethylene (TCE) and tetrachlorethylene (PCE) were once used in large amounts in the cleaning of precision parts and dry cleaning, and the substance of large-scale pollution of soil and groundwater due to their leakage is becoming clear. is there.
Furthermore, since teratogenicity and carcinogenicity of these organochlorine compounds have been pointed out and it has been found that they have a very serious impact on the living world, it is urgently necessary not only to cut off pollution sources but also to clean soils and groundwaters where pollution has already spread. It has become a problem to be solved.

As a method for cleaning soil contaminated with organic chlorine compounds, a method of excavating the contaminated soil and heat treatment, a method of vacuum extraction from the contaminated soil, or a method of injecting a microorganism capable of decomposing the pollutant, etc. Is mentioned.

Although the heat treatment method can almost completely remove pollutants from soil, soil excavation is necessary, so that purification treatment under a building is difficult, and the cost required for excavation and heat treatment is high. Since it is huge, it is difficult to apply it to the purification of a wide range of contaminated soil. Further, since the organic chlorine compound that is heated and evaporated from the soil causes air pollution, it is necessary to adsorb it on activated carbon or the like to recover it, but it is necessary to further treat this used activated carbon.

On the other hand, the vacuum extraction method and the microbial utilization method are inexpensive and simple because there is no need to excavate contaminated soil, and repair work is carried out even on soil where the ground surface is being used in a building or the like while using the ground surface. There is an advantage that can be done. But,
The vacuum extraction method has a low efficiency of removing low-concentration organic chlorine compounds of several ppm or less, and it is necessary to treat the recovered organic chlorine compounds again as in the heat treatment. Therefore, in Japanese Laid-Open Patent Publication No. 7-185252, a compact ground facility is proposed by adsorbing the sucked target gas with activated carbon and using a fluidized bed to reprocess the activated carbon.
It still requires the above-ground equipment for processing. On the other hand, the method for microbial purification is divided into a method of using the degrading microorganisms of the soil originally inhabiting the soil and a method of using an exogenous degrading microorganism not originally inhabiting the soil. In the former case, bacteria, such as nutrients, inducers, oxygen, and growth stimulants for enhancing decomposition activity are injected into the soil for purification.
In the latter case, the foreign microorganisms are injected into the soil, and the bacteria activator for increasing the decomposition activity is injected. For example, a report isolated from a microorganism capable of degrading an organochlorine compound is, as a TCE-degrading bacterium, Welchia alkenop.
hila sero 5 (USP 4877736, ATCC 53570), Welchia alk
enophila sero 33 (USP 4877736, ATCC 53571), Methyl
ocystis sp. strain M (Agric. Biol. Chem., 53, 2903
(1989), Biosci. Biotech. Biochem., 56, 486 (199
2), ibid., 56, 736 (1992)), Methylosinus trichosprium O
B3b (Am. Chem. Soc. Natl. Meet. Dev. Environ. Micr
obiol., 29,365 (1989), Appl. Environ. Microbiol., 5
5, 3155 (1989), Appl. Biochem. Biotechnol., 28, 877.
(1991), JP-A-02-92274, JP-A-03-292970), Methylomonas sp.MM2 (Appl. Environ. Microbio
l., 57, 236 (1991)), Alcaligenes denitrificans ss.
p. xylosoxidans JE75 (Arch. microbiol., 154,410 (1
990)), Alcaligenes eutrophus JMP134 (Appl. Enviro
n. Microbiol., 56, 1179 (1990)) Mycobacterium vacca
e JOB5 (J. Gen. Microbiol., 82,163 (1974), Appl. E
nviron. Microbiol., 54, 2960 (1989), ATCC 2967
8), Pseudomonas putida BH (Sewer Association Journal, 24, 27
(1987)), Acinetobactor sp.strain G4 (Appl. Enviro
n. Microbiol., 52, 383 (1986), same 53, 949 (1987),
54, 951 (1989), 56, 279 (1990), 57, 193 (199)
1), USP 4925802, ATCC 53617, this fungus was initially Pseudomona
s cepacia, but changed to Acinetobactor sp.), Pseudomonas mendocina KR-1 (Bio / Techno
l., 7, 282 (1989)), Pseudomonas putida F1 (Appl. E
nviron.Microbiol., 54, 1703 (1988), 54, 2578 (198)
8)), Pseudomonas fluorescens PFL12 (Appl. Environ.
Microbiol., 54, 2578 (1988)), Pseudomonas putida K
WI-9 (Japanese Patent Laid-Open No. 06-70753), Pseudomonas cepacia K
K01 (Japanese Patent Laid-Open No. 06-227769), Nitrosomonas europae
a (Appl.Environ.Microbiol., 56, 1169 (1990)), Lac
tobacillus vaginalis sp.nov (Int.J.Syst.Bacterio
l., 39, 368 (1989), ATCC 49540), etc. are known.
All of these degrading bacteria require chemical substances such as aromatic compounds and methane as degrading inducers in order to degrade TCE. When injecting such foreign microorganisms and fungal activators to enhance their degrading activity, inject as much microorganisms or chemicals as possible into the intended repair area to decompose pollutants. It is economically desirable to perform soil purification. For this reason, the microbial purification treatment is carried out by injecting into the soil a sufficient amount of the chemical liquid to fill the soil voids in the repair region, and there is a disadvantage that a huge amount of the chemical liquid is required for a wide repair region. Also,
Because it is difficult to contain the injected microorganisms and fungal activators in a certain area, and it is difficult to recover the degrading bacteria that proliferated in the soil after the treatment work and the fungal active substances that remained in the soil,
There is a problem of secondary pollution of soil due to these.

Thus, although the vacuum extraction method and the microbial purification method have advantages over the heat treatment method, they also have drawbacks.

Therefore, in Japanese Laid-Open Patent Publications Nos. 6-254537 and 7-112176, a vacuum extraction method and a microbial purification method are combined, and air or groundwater contaminated with organic chlorine compounds in contaminated soil is vacuum-sucked to remove the above-mentioned biotechnology. A method of leading to a reactor and performing decomposition treatment therein has been proposed. This is because the microbial decomposition of the organic chlorine compound eliminates the need for reprocessing of the recovered organic chlorine compound, which is a drawback of the vacuum extraction method, and the installation of a microbial decomposition reactor is a drawback of the microbial purification method. It aims to solve injection problems and cross-contamination problems.

[0008]

Most of the above-mentioned conventional methods for purifying contaminated soil are intended for unsaturated aquifers above the groundwater level, and are used for groundwater or below the groundwater level. It is not a method of treating contaminated soil. Organochlorine compounds represented by trichlorethylene generally have a high specific gravity, and in the case of soil pollution, they fall down to the impermeable layer in the ground. For this reason, there is a high possibility that a high-concentration pollution source exists at a position lower than the upper surface of the groundwater level. In such a situation, the efficiency of vacuum extraction and the supply of oxygen necessary for microbial purification do not remain.

[0009]

The present invention has been made to solve the above problems, and is a method for purifying soil contaminated with a volatile organic chlorine compound at a position lower than the groundwater level. In the state surrounding the contaminated area, a plurality of pumping equipment for sucking groundwater is installed up to a position lower than the contaminated layer, and a layer with a high porosity such as gravel is provided around this pumping equipment. By sucking groundwater, the groundwater level is lowered to a position lower than the contaminated stratum to be purified, the contaminated stratum is forcibly formed as a ventilation layer, and then air is supplied to the ground through this high porosity layer. . Then, a pipe for injecting microbial activating substance and a pipe for inhaling air are installed at almost the same position in the central part surrounded by the pumping equipment, and the microbial activating substance is injected by the pipe for injecting microbial activating substance to form a decomposition region. . The method is characterized in that polluted air is passed through the decomposition region by an air suction pipe to be purified, and then the air is sucked and discharged from the ground.

Further, it is a method of purifying soil contaminated with a volatile organic chlorine compound at a position lower than the groundwater level, in which groundwater is sucked to a position lower than the contaminated stratum in a state of surrounding the contaminated area. A pumping facility is installed for this purpose, a layer with a high porosity is provided around this pumping facility, and groundwater is sucked by this pumping facility group to lower the groundwater level to a position lower than the contaminated stratum to be purified, thereby causing pollution. After the formation is forcibly formed as a ventilation layer, air is fed into the ground through this high porosity layer. In addition, a pipe for injecting pollutant degrading microorganisms and microbial activators and an air suction pipe were installed at approximately the same position in the center surrounded by the pumping equipment, and contaminants were decomposed by the pipes for injecting pollutant degrading microorganisms and microbial activators. Injecting degrading microorganisms and microbial activators to form degrading areas. This is a method for purifying contaminated soil, which is performed by passing contaminated air through a decomposition region through an air suction pipe to purify it and then sucking the air and discharging it from the ground.

Examples of substances that enhance the decomposition activity of microorganisms include nutrients, inducers, oxygen, and growth stimulants.

Further, the temperature inside the soil does not change much as compared with the temperature, and it is possible to easily provide a microbial environment having a constant temperature throughout the year without using special heating, cooling and heat-retaining equipment.

The microorganisms in the present invention include bacteria, microalgae, molds, actinomycetes, and protozoa, and the bacteria particularly useful in industry are bacteria.

In particular, the JM1 strain (FERM BP-
5352) is preferably used in the practice of the present invention because of its strong activity of decomposing organic compounds and the nature of inducer-free property. It was noted that this bacterium was recognized as belonging to Corynebacterium at the time of depositing, but since some questions were raised in this respect in the subsequent research, at present it is simply JM1.
Call it a stock.

JM1 mycological properties Gram stainability and morphology: Gram-negative bacilli Growth on each medium BHIA: Good growth MacConkey: Viable Colony color: Cream Optimum temperature: 25 ° C> 30 ° C> 35 ° C Motility: Negative (semi-fluid medium) TSI (slant / butt): alkali / alkaline, H ₂ S (−) oxidase: positive (weak) catalase: positive sugar fermentation glucose: negative sucrose: negative raffinose: negative galactose: negative maltose: Negative urease: Positive Esculin hydrolysis (β-glucosidase): Positive Nitrate reduction: Negative Indole productivity: Negative Glucose acidification: Negative Arginine dihydrolase: Negative Gelatin hydrolysis (protease): Negative β-galactosidase: Negative Assimilation of each compound Glucose: negative L-arabinose: negative D-mannose: negative D-mannitol: negative N-acetyl-D-glucosamine: negative maltose: negative Potassium gluconate: negative n-capric acid: positive adipic acid: negative dl-malic acid: positive citric acid Sodium: Positive Phenyl acetate: Negative Hereinafter, the present invention will be described with reference to Examples, but these do not limit the scope of the present invention in any way.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a conceptual diagram showing an example of the configuration of equipment used for implementing the present invention.

Reference numeral 1 is a pumping equipment, which comprises a pipe for absorbing water and a point at the tip, and is installed so that the point at the tip is lower than the contaminated area c. These pumping equipment 1
Is arranged so as to surround the contaminated area c, and is connected to the pump 3 via the pipe 2. The point at the tip of the pumping equipment 1 is a nozzle with small holes opened, and a negative pressure is applied by a pump 3 via a pipe 2 to suck groundwater to the ground.

A sand column 4 having a high porosity composed of gravel (preferably having an average particle size of 10 mm or more) covers the pumping equipment 1. In addition, the surface of the sand pillar 4 is covered with an air injection pipe 5 and is insulated from the ground, but the lower part is exposed in the contaminated area c. These insufflation pipes 5 are connected to the exhaust port of the pump 7 via the pipes 6, and the air from the pump 7 is fed into the sand column 4
It can be supplied to the contaminated region c via.

Reference numeral 8 is an injection pipe for injecting a pollutant-degrading microorganism (for example, JM1 strain if the pollutant is TCE) and a microbial-activating substance from the injection port into the contaminated region c by a pipe 13, a pump 14, The valve 15 is connected to a tank 16 for decomposing bacteria containing a microorganism decomposing pollutants and a tank 17 for a bacteria active solution containing a microorganism activating substance. The area above the injection port of the injection pipe 8 is covered with a sand column 9 made of gravel or the like and having a high porosity. The surface of the sand pillar 9 is covered with an intake pipe 10, and the lower portion is exposed in the ground. The intake pipe 10 is connected to the intake port of the pump 7 via a valve 11 and a pipe 12, and a negative pressure is applied by the pump 7 to suck the air in the ground.

Next, the purification method will be described.

A negative pressure is supplied by the pump 3 to the group of pumping equipment 1 surrounding the contaminated area c, and groundwater is sucked to the ground from a point at the tip of the pumping equipment 1, whereby the groundwater level W1 in a natural state is obtained.
Is lowered to a position W2 lower than the contaminated area c to be cleaned. By lowering the groundwater level, the contaminated region c, which has been present in the groundwater until then, becomes ready for ventilation.

In the contaminated area c which can be vented, the valve 1
By closing 1 and driving the pump 14, the pollutant-degrading microorganisms and the microorganism-activating substance are injected by the injection pipe 8 to form the decomposition region b. The pollutant-degrading microorganisms and the microorganism-activating substance may be injected at the same time or sequentially by switching the flow path with the valve 15.

When the injection is completed, the valve 11 is opened, a negative pressure is supplied by the pump 7, and the air in the ground is sucked by the intake pipe 10 via the sand pillar 9. As a result, the gas in the decomposition area b is sucked, so that the air containing the contaminants in the contamination area c flows to the decomposition area b, and the clean air around the contamination area c flows to the contamination area c. In the decomposition region b, inflowing air is purified because microorganisms aerobically decompose pollutants in the air. In the contaminated region c, contaminants diffuse into the inflowing clean air, and as a result, the contaminated concentration in the contaminated region c decreases and purification proceeds. The clean air sucked by the intake pipe 10 is returned to the ground through the pipe 12, the pump 7, the pipe 6, the gas injection pipe 5 group, and the sand column 4 group.

As described above, (1) the clean air around the polluted area flows into the polluted area c and sucks the pollutant to lower the concentration of the polluted area c, and (2) the air containing the pollutant enters the decomposed area b. The pollutants are decomposed by microorganisms by flowing in, and (3) the clean air is returned to the vicinity of the contaminated region c, whereby the underground air is circulated and the contaminated soil is purified.

In the present embodiment, the decomposing region b was formed by injecting the pollutant degrading microorganisms and the microbial activator, but the degrading region b was formed by injecting only the microbial activator and activating the indigenous bacteria in the ground. You may form.

Further, as shown in FIG. 2, a pump 18 is connected to the pipe 6, the suction port of the pump 18 is opened to the atmosphere, and the exhaust port of the pump 7 is opened to the atmosphere, so that clean air in the atmosphere is obtained. The air may be sent into the ground and the air sucked from the ground may be released into the atmosphere. At this time, the pollutant concentration sensor 19 provided in the intake pipe 10 constantly monitors the pollutant concentration, and the control device 20 controls the pumps 7 and 18 to prevent the pollutant from being released into the atmosphere.

It is also possible to add a pipe and a valve, and connect the suction port of the pump 18 and the exhaust port of the pump 7 by switching the valve so that the circulation system can be switched.

[0028]

As described above, according to the present invention, microbial purification of organic matter-contaminated soil below a wide range of groundwater level can be performed at low cost, very efficiently, and safely as a closed system if necessary. Can be done.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of the configuration of equipment for implementing the present invention.

FIG. 2 is a diagram showing an example of implementation of the present invention.

[Explanation of symbols]

 1 Water Facilities 2 Pipes 3 Pumps 4 Sand Pillars 5 Gas Pipes 6 Pipes 7 Pumps 8 Injection Pipes 9 Sand Pillars 10 Intake Pipes 11 Valves 12 Pipes 13 Pipes 14 Pumps 15 Valves 16 Decomposing Bacteria Liquid Tanks 17 Bacterial Active Liquid Tanks 18 Pumps 19 Sensor 20 Control Device b Decomposition Area c Contamination Area W1 Natural Groundwater Level W2 Reduced Groundwater Level

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Etsuko Sugawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akira Kuriyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Co., Ltd. (72) Inventor Akira Watanabe 4-23, Kudankita 4-chome, Chiyoda-ku, Tokyo Lait Kogyo Co., Ltd. (72) Inventor Masatoshi Iio 4-35, Kudankita 4-chome, Chiyoda-ku, Tokyo Lait Kogyo Co., Ltd. (72) Inventor Yuri Chiaki 4-23, Kudankita 4-chome, Chiyoda-ku, Tokyo Light Industrial Co., Ltd.

Claims (9)

[Claims] 1. A method for purifying soil contaminated with volatile substances at a position lower than the groundwater level, which encloses a contaminated area with a pumping facility for sucking groundwater to a position lower than the contaminated stratum. The groundwater level is lowered to a position lower than the contaminated stratum to be purified by suctioning groundwater by the pumping facility group, and the contaminated stratum is forcibly installed. As a ventilation layer, air is supplied to the ground through the layer having a high porosity, a microbial decomposition region is formed in the central portion surrounded by the pumping equipment, and an air suction pipe is provided near the microbial decomposition region. A method for purifying contaminated soil, in which contaminated air is passed through the microbial decomposition region for purification by suctioning air by means of the above method and then discharged from the ground. 2. The method for purifying contaminated soil according to claim 1, wherein the volatile substance is a hydrocarbon. 3. The method for purifying contaminated soil according to claim 2, wherein the hydrocarbon is an organic chlorine compound or an aromatic compound. 4. The method for purifying contaminated soil according to claim 2, wherein the hydrocarbon is a fuel. 5. The method for cleaning contaminated soil according to claim 3, wherein the organic chlorine compound is trichloroethylene or tetrachloroethylene. 6. The decomposition region is formed by injecting a microbial activating substance through a pipe for pollutant-decomposing microbial activating substance injection pipe provided in a central portion surrounded by a water pumping facility. Method for cleaning contaminated soil. 7. A decomposition region is formed by injecting a pollutant-degrading microorganism and a microorganism-activating substance through a pipe for injecting a pollutant-degrading microorganism and a contaminant-degrading microorganism-activating substance provided in a central portion surrounded by a pumping facility. The method for purifying contaminated soil according to claim 1, wherein 8. An area of soil contaminated with volatile substances formed at a position lower than groundwater level (contaminated area)
A method for microbial purification of water, in which a plurality of ground water means for sucking groundwater to a position lower than the contaminated area are installed in a state of surrounding the contaminated area, and a gap reaching at least the contaminated area is provided close to the pumping means. An area with a high rate is provided, groundwater is sucked by the pumping means and the water level is lowered to a position lower than the contaminated area so that the contaminated area can be ventilated, and air is supplied through the gas-liquid injection and discharge means provided above the contaminated area. Then, a microbial decomposition region is formed in at least a part of the contaminated region, and a negative pressure is applied to the gas-liquid injection / exhaust means to remove air from the region having a large porosity through the contaminated region to the gas-liquid injection / discharge device. A method for purifying contaminated soil, characterized by performing a flow. 9. The method according to claim 8, wherein a means for supplying the pollutant-degrading microorganisms and / or the microbial activated material through the gas-liquid injection / discharge means is intermittently used in the microbial decomposition area.