JP3724967B2 - How to repair contaminated soil - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for purifying or immobilizing soil contaminated with halogenated organic compounds, hydrocarbons, or heavy metals, and more particularly, to a construction method for purifying contaminated soil combining soil agitation, chemical reaction and biological reaction. .
[0002]
[Prior art]
In recent years, halogenated organic compounds such as tetrachloroethylene, trichloroethylene, 1.1.1-trichloroethane, and dichloroethylene have been widely used as degreasing / cleaning agents for metal parts such as electronic devices and cleaning agents for dry cleaning. Contamination of soil and groundwater with this halogenated organic compound has been reported one after another. In addition, soil contamination by hydrocarbons such as gasoline and light oil, and heavy metals such as mercury and chromium has been reported in part. Since these pollutants are not easily decomposed in nature and are poorly water-soluble, they are likely to accumulate in soil and infiltrate into groundwater in contaminated areas. In addition, halogenated organic compounds are said to cause liver damage and have carcinogenicity, and it is desired to decompose or fix these substances contained in soil and the like there.
[0003]
For this reason, various methods have been proposed for purifying contaminated soil or immobilizing contaminants by injecting a chemical solution while stirring the soil while penetrating a device having stirring ability into the contaminated soil. These methods include injecting quicklime and vaporizing halogenated organic compounds by exothermic reaction, injecting nutrients and reducing agents and dechlorinating halogenated organic compounds by reducing reaction, and excavating soil. A method of removing hydrocarbon pollutants by steam injection and gas suction, a method of immobilizing the pollutants by injecting cement, a water retention agent, and a water shielding agent can be considered.
[0004]
However, in these methods, for example, soil agitation and chemical solution injection from a ground surface to a depth of about 10 m with respect to a contaminated soil layer concentrated at a depth of 5 to 10 m in the ground. This work was difficult. For example, a device capable of stirring soil up to a depth of 10 m requires a stirring device with a total height of about 15 m. Therefore, if the soil to be restored is under a building such as a factory, at least the roof of the building It was necessary to remove and install a stirring device.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a method for repairing contaminated soil that can efficiently repair contaminated soil that is concentrated in a relatively deep position.
[0006]
[Means for Solving the Problems]
Contaminated soil remediation process of the present invention, when the soil to be purified target is below the building block, to cutting drilling the surface layer of the pre-ground to a depth near the soil to be the cleaning object, the stirring machine excavated soil It is characterized in that the soil below the excavated ground is agitated and injected with a chemical solution or the like, the soil to be purified is repaired, and the surface layer of the ground is backfilled .
[0007]
The assembly and disassembly of the stirring machine is preferably performed on the ground surface from which the surface layer has been excavated and removed. Furthermore, the contaminated soil remediation method is preferably a halogenated organic compound-contaminated soil remediation method by decomposing a halogenated organic compound by a reductive dehalogenation reaction that combines a chemical reaction and a biological reaction.
[0008]
According to the present invention described above, since the surface ground is excavated to the vicinity of the depth of the contaminated soil to be purified in advance, and the soil to be purified is purified by stirring from the excavated surface, efficient contaminated soil Can be repaired. That is, when contaminated soil exists over a plurality of layers, for example, the surface layer is generally loam or sandy soil, and the deeper layer is silt or clay layer. In general, the surface layer is a ventilation layer above the groundwater surface, and the deeper layer is a saturated layer (aquifer) below the groundwater surface. In such a case, the contamination of the surface layer is low in concentration due to natural diffusion or can be easily removed by a physical method such as vacuum gas suction, and only deeper contamination tends to remain. Therefore, the part of the surface layer where the contamination concentration is low or the part where the purification has been completed is excavated and removed in advance, and a device having the ability to agitate the soil is installed on the removed ground surface and penetrates from this ground surface. However, by stirring the soil to be purified, it is possible to inject a chemical solution or the like while intensively stirring a portion having a high contamination concentration. As a result, it is possible to intensively purify or immobilize the soil in a portion having a high contamination concentration. And, for example, if there is a building, it is possible to put a device having a stirring ability into the space by excavating up to about 5 m in the basement, for example, without removing the roof of the building, etc. Can repair contaminated soil.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0010]
As shown in FIG. 1, it is assumed that a factory building 11 exists on the ground surface 10 and soil 15 contaminated with an organic base compound exists at 5 to 10 m below the ground. Here, the factory building 11 is supported by a column 12 and a ceiling 13 in the building. As described above, this contaminated soil 15 is difficult to decompose conventional bioremediation such as trichlorethylene (TCE), dichloroethylene (DCE), tetrachloroethylene (PCE), 1.1.1-trichloroethane, carbon tetrachloride and the like. Contaminated soil containing organic chlorine compounds. Such soil contamination distribution is, for example, when there is a strata that easily adsorbs pollutants at a depth of about 5 to 10 m and / or a poorly permeable layer that does not permeate pollutants at a depth of 10 m or more. Commonly observed when present.
[0011]
This type of contaminated soil is a hybrid environmental remediation method that combines the power of the ecosystem and chemical dechlorination by agitating the soil and injecting chemicals such as nutrients, reducing agents, and dissolved water. Organic chlorine compounds are decomposed and the soil is purified. Further, when the water content of the formation is relatively low, or when countermeasures are urgent, exothermic reaction by quicklime injection, removal reaction by steam injection and gas suction is preferably used. Furthermore, when the stratum is below the groundwater surface and there is a concern about the diffusion of contamination due to the groundwater flow, it is desirable to use the concrete, water retention agent, immobilization of the pollutant with a water barrier and diffusion prevention construction in combination.
[0012]
In the contaminated soil repairing method of the present invention, as shown in FIG. 2, first, a ground surface portion where no contaminated soil exists is excavated from the ground surface 10 to a distance M (for example, about 5 m). The excavation of the ground is performed using a civil engineering machine 17 such as a backhoe. As a result, the ground is lowered to the point where the contaminated soil 15 is present. Thus, when excavating the surface layer and lowering the ground, it is preferable to drive a sheet pile or the like around and fix the excavated wall surface. Further, when the excavation target range includes under the pillars of the building, etc., it is necessary to remove the pillars of the corresponding part and to apply beams to the roof to maintain the factory building 11.
[0013]
Next, as shown in FIG. 3, the slope 16a for entering from the ground surface is provided in at least a part of the excavated ground 16, and the disassembled stirring machine 18 and the crane 19 for assembly are entered. Then, the agitating machine 18 is assembled on the excavated ground 16 and, in particular, the column for excavation is started up. In this way, by lowering the ground by the distance M, the excavation length becomes shorter compared with the case where construction is performed from the ground surface, so that a stirring machine having a low overall height can be used. In addition, since the column of the stirring device for excavation is started up at a place where the ground is lowered, the distance to the ceiling can be increased, and the two effects of the stirring machine 18 are within the height to the ceiling. It is efficient because it is not necessary to remove the roof of the building.
[0014]
Next, as shown in FIG. 4, soil repair work using a soil agitation machine is performed.
The soil is repaired by injecting a chemical solution or the like while stirring the soil to a depth L where the contaminated soil is contained using the stirring machine 18. Reference numeral 20 denotes a portion of the soil that has been repaired by stirring and injection of a chemical solution or the like. Such a soil repairing operation is performed on the entire area of the ground 16 dug down as shown in FIG.
[0015]
After completion of the repair work, the agitating machine 18 is disassembled on the ground 16 excavated again using the crane 19 as shown in FIG. 6, and the agitating machine 18 is carried out to the ground. Thereafter, as shown in FIG. 7, the surface soil is backfilled using a civil engineering machine 17 such as a backhoe. Then, the site is restored by rolling with a roller or the like. FIG. 8 shows a state where the recovery is finished. In this method, the excavated soil close to the surface layer is backfilled again without adding water or agitation. For this reason, compared with the case where it stirs from the ground surface using a stirring apparatus, the ground strength of the ground surface does not fall, and subsequent recovery is easy. Needless to say, when part of the pillars in the building are removed, the restoration is also performed.
[0016]
In addition, in the said embodiment, although the case where a contaminated soil layer exists in the depth of 5-10 m was demonstrated, when a contaminated soil layer exists in the depth of 10-15 m, for example, excavation depth is about 10 m. And it is sufficient. In this manner, various modified embodiments are possible without departing from the spirit of the present invention.
[0017]
【The invention's effect】
As described above, according to the present invention, the ground on the ground surface is dug down, and then the soil containing the pollutant is repaired by stirring and injecting chemicals or the like. Thereby, since the agitation depth from the ground surface is relatively shallow, efficient soil repair work can be performed. In addition, since the soil is repaired from the ground dug down using a stirring machine, for example, when the contaminated soil under the factory building is repaired, the soil in the building is not contaminated without removing the roof of the building. It becomes possible to repair the soil.
[Brief description of the drawings]
FIG. 1 is a diagram showing a repair process of contaminated soil, and shows a case where contaminated soil exists under a factory building.
FIG. 2 is a diagram showing a process for repairing contaminated soil, showing the stage of excavating the surface layer.
FIG. 3 is a diagram showing a process for repairing contaminated soil, and shows a stage of carrying in a stirring machine or the like.
FIG. 4 is a diagram showing a process for repairing contaminated soil, and shows a stage in which the soil is stirred and the chemical solution is injected using a stirring machine.
FIG. 5 is a diagram showing a process for repairing contaminated soil, and shows a stage at which soil repair work is completed.
FIG. 6 is a diagram showing a process for repairing contaminated soil, and shows a stage where a stirring machine is carried out.
FIG. 7 is a diagram showing a process for repairing contaminated soil, and shows a step of refilling excavated ground.
FIG. 8 is a diagram showing a process of repairing contaminated soil, showing a stage where restoration is completed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Ground surface 11 Factory building 12 Prop 13 Ceiling surface 15 Contaminated soil 16 Excavated ground surface 17 Civil engineering machine 18 such as backhoe 18 Agitation machine 19 Crane 20 Repaired soil

Claims (3)

When the soil to be purified is under the building,
Cutting drilling the surface layer of the pre-ground to a depth near the soil to be the cleaning object,
Install a stirring machine on the excavated ground,
Stirring the soil below the excavated ground and injecting chemicals etc. , repairing the soil to be purified,
A method for remediating contaminated soil, wherein the surface layer of the ground is backfilled . The contaminated soil remediation method according to claim 1, wherein the agitation machine is assembled and disassembled on a ground surface from which the surface layer has been excavated and removed.   2. The contaminated soil remediation method is a halogenated organic compound-contaminated soil remediation method by decomposing a halogenated organic compound by a reductive dehalogenation reaction that combines a chemical reaction and a biological reaction. Or the contaminated soil repairing method of 2 description.

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