JP2004209451A - Method for treating contaminated soil caused by volatile organic compound and improving apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an economical method for treating a contaminated soil caused by a volatile organic compound in which the scale of an installation can be simplified and there exists little restriction. <P>SOLUTION: The soil is improved on every vertical hole 3 formed in the ground in such a way that a hot spot where the contaminated soil caused by the volatile organic compound is distributed is covered. The vertical hole is formed by a drilling apparatus 14 having a covering body 11 shutting the internal space from the open air and a chain saw 17 stored in the internal space S of the covering body and drilling into the ground. A discharging liquid is discharged into the vertical hole and air is compressed therein and the chain saw of the drilling apparatus is rotated. The contaminated soil fluidized around the chain saw and the injected air are mixed/agitated to expose the volatile organic compound included in the contaminated soil, and the contaminated soil is guided into the internal space, wherein the volatile organic compound is volatilized and is separated from the contaminated soil. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for treating contaminated soil with a volatile organic compound and an improved apparatus used for the method.
[0002]
[Prior art]
Volatile organic compounds such as dichloromethane, carbon tetrachloride, 1,2-dichloromethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, 1,1,1-trichloroethylene, tetrachloroethylene, benzene, 1,2-dichloroethylene These have been used in large quantities for various purposes such as cleaning IC boards and electronic components, pretreatment cleaning of metal components, and solvents for dry cleaning.
[0003]
Volatile organic compounds, except for benzene, have a specific gravity higher than that of water, are hardly soluble in water, and have a high vapor pressure, so that they are easily volatilized into the atmosphere and the like.
[0004]
For this reason, a hot spot (contamination center) of the contaminated soil due to the volatile organic compound is formed at the site where the volatile organic compound is used or before the volatile organic compound moves through the groundwater table and the like, and measures are taken. That is urgent.
[0005]
An air sparging method is a permanent measure for volatile organic compounds that satisfies the conditions of performing in-situ purification, not requiring pumping of groundwater, and not using quick lime.
[0006]
The air sparging method is widely used mainly in Europe and the United States.As an analogy of soil gas suction, air is injected into soil or groundwater contaminated with volatile organic compounds using air sparing wells. Perturbs the air flow between the soil particles to promote the vaporization of volatile organic compounds.
[Patent Document 1]
"Purification of contaminated groundwater by air sparging" Soil Environment Division, Water Environment Department, Environmental Management Bureau, Ministry of the Environment Published July 2002 [0007]
[Problems to be solved by the invention]
However, this method has the following problems.
(1) It is necessary to provide a large-scale aeration device on the ground.
(2) There are many restrictions such as inability to use due to groundwater table (saturated / unsaturated).
(3) A short circuit occurs due to problems specific to the well construction method (anisotropy of the stratum (for example, inhomogeneity, discontinuity such as bedding or cracks)) and the formation and uneven distribution of air channels along the peripheral surface of the well. The effect will be insufficient).
(4) The construction period is long and the cost is high.
[0008]
Therefore, an object of the present invention is to provide an economical method for treating polluted soil with volatile organic compounds, which can simplify the equipment scale, has few restrictions, and is economical.
[0009]
[Means for Solving the Problems]
The method for treating contaminated soil with the volatile organic compound according to claim 1,
A method of improving soil by forming a plurality of vertical holes in the ground so as to cover hot spots in which contaminated soil by volatile organic compounds is distributed, and for each vertical hole,
The vertical hole is
A cover that blocks the internal space from outside air,
A drilling device having a chainsaw that is housed in the interior space of the covering body and excavates in the ground in the interior space and advances and retreats into the ground,
By discharging the discharge liquid into the vertical hole, pressing air into the vertical hole, and rotating the chainsaw of the excavator,
Around the chainsaw, the fluidized contaminated soil and the injected air are mixed and agitated to aerate volatile organic compounds contained in the contaminated soil,
The contaminated soil is guided to the internal space, in which the volatile organic compounds are volatilized, and the volatile organic compounds are separated from the contaminated soil in the internal space.
[0010]
In this configuration, the fluidized contaminated soil and the injected air are mechanically mixed and stirred by a chainsaw to aerate volatile organic compounds contained in the contaminated soil. For this reason, the chainsaw and its surroundings function as an aeration device, and there is no need to provide a large-scale aeration device on the ground surface, and the equipment can be simplified.
[0011]
In addition, since this mechanical mixing and agitation is used, as long as drilling with a chainsaw is possible, it can be applied consistently regardless of the saturation zone / unsaturation zone, permeable layer / impervious layer, or the hardness of the ground. , Less restrictions.
[0012]
Furthermore, since this mechanical (forced) mixing and stirring is used, the efficiency of vaporizing or decomposing the volatile organic compound is higher than that of the suction method or the well method, and the construction period can be shortened and the cost can be reduced. .
[0013]
Moreover, the vertical hole can be easily moved to a free position on the ground surface in a plan view, so that a plurality of vertical holes are formed to easily improve the soil including the entire hot spot or the surrounding area, It is effective.
[0014]
In the method for treating contaminated soil with a volatile organic compound according to the second aspect, the volatile organic compound is sucked from the internal space into the gas recovery device to recover the volatile organic compound.
[0015]
In this configuration, the volatile organic compound can be recovered by the gas recovery device, and the inside of the vertical hole and the inside of the vertical hole can be purified.
[0016]
In the method for treating contaminated soil with a volatile organic compound according to the third aspect, the concentration of the volatile organic compound sucked into the gas recovery device is measured, and the chainsaw is continuously rotated until the concentration falls within a certain range.
[0017]
With this configuration, the soil can be purified to a level that satisfies a certain standard in all the vertical holes, and the quality of the purification result can be easily guaranteed.
[0018]
In the method for treating contaminated soil with a volatile organic compound according to the fourth aspect, after soil improvement, a solidified liquid is injected into a vertical hole to form a ground improvement body.
[0019]
In this configuration, by forming the ground improvement body, even if the volatile organic compound slightly remains in the vertical hole, it can be sealed and prevented from being diffused to the outside. In addition, the strength of the purified soil can be increased to improve its use value.
[0020]
In the method for treating contaminated soil with a volatile organic compound according to claim 5, prior to soil improvement, an underground continuous wall surrounding at least the hot spot is formed.
[0021]
In this configuration, by forming the underground continuous wall, the volatile organic compound is sealed, and diffusion to the outside can be prevented.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a site example according to an embodiment of the present invention, and FIG. 2 is a sectional view of the same.
[0023]
First, as shown in FIG. 1, prior to forming the vertical hole 3, an underground continuous wall 4 surrounding the hot spot 1 is formed. In the present embodiment, the improved device 10 used for forming the vertical hole 3 is also used for the underground continuous wall 4. However, when the underground continuous wall 4 is formed, soil improvement is not performed, and a solidifying agent such as cement milk is supplied and solidified.
[0024]
Next, a plurality of vertical holes (quadrangular prisms) 3 are formed for the hot spot 1 on the contaminated soil by the volatile organic compound, and the hot spot 1 is covered by the vertical holes 3. More preferably, the vertical hole 3 is also formed in the surrounding area 2 of the hot spot 1. The method of forming each vertical hole 3 will be described later in detail.
[0025]
By the way, in the state shown in FIG. 1 and FIG. 2, soil improvement has been completed for the vertical hole 3 in the improved area S1 to a predetermined depth H, and soil improvement is currently being performed for the vertical hole 3 in the improving area S2. The vertical holes 3 in the unimproved area S3 are soil-improved after the soil improvement of the vertical holes 3 in the improving area S2 is completed.
[0026]
Here, the improvement device 10 is provided with a hanger 12 at the top thereof, and the lower end of a wire 13 hung from a crane (not shown) is connected to the hanger 12. Therefore, by moving the crane truck on the ground 5, the improvement device 10 can be easily moved in the XY directions, and the vertical hole 3 can be formed at a desired position.
[0027]
Therefore, the processing method of the present invention is more mobile with respect to the position than the conventional technique of digging a well at a fixed position, and the movement is completed in a short time.
[0028]
Next, details of the improvement device 10 and its movement in the Z direction will be described with reference to FIG. FIG. 3 is an elevational view of the excavator, showing a state before starting excavation in the ground.
[0029]
As shown in FIG. 3, the improvement device 10 includes a cover 11 that is vertically expandable and contractible. The internal space S of the cover 11 is shielded from the outside, so that even if the volatile organic compound volatilizes in the internal space S, the volatile organic compound does not leak to the outside.
[0030]
More specifically, the cover body 11 includes a lower cover 11a installed on the ground 5, an upper cover 11b to which the hanging hardware 12 is fixed at the center of the upper surface, a lower end of the upper cover 11b, and an upper end of the lower cover 11a. And a bellows 11c for elastically connecting the bellows.
[0031]
Then, the vertically long excavator 14 is stored in the internal space S of the cover body 11. The excavator 14 has a drive roller 15 that is driven by a motor and a speed reducer (not shown) at the upper end thereof and rotates in the direction of the arrow N1, and a return roller 16 that is rotatably supported at the lower end.
[0032]
An endless chain saw 17 is stretched between the drive roller 15 and the return roller 16. Here, the “chainsaw” in the present specification only needs to be capable of forming the vertical hole 3 in the shape of a quadrangular prism, and is wider than the concept of a general chainsaw. For example, the shape of the bit of the chain saw 17 can be variously changed depending on the application.
[0033]
That is, as the drive roller 15 is driven and rotates in the direction of the arrow N1, the chainsaw 17 is once in contact with the drive roller 15 and then descends, then is in contact with the return roller 16 and is folded from the descending direction to the ascending direction. , And goes around the route to the drive roller 15.
[0034]
Here, the excavation of the underground by the excavator 14 (that is, the lowering of the improvement device 10 in the Z direction) proceeds only when the chainsaw 17 excavates the underground near the return roller 16. Normally, at this time, it is not necessary to apply a downward load to the excavator 14, and it is only necessary to unwind the wire 13 from the crane truck.
[0035]
In FIG. 3, the drive roller 15 is rotatably supported on the upper cover 11 b. Therefore, when the upper cover 11 b is moved up and down by feeding / rewinding the wire 13, the entire excavator 14 is moved. But it goes up and down integrally with it. The excavator 14 can freely move up and down with respect to the lower cover 11a in the Z direction.
[0036]
Mixing and stirring of the contaminated soil fluidized by the discharged liquid and the pressurized air are performed in the entire region of the chainsaw 17 located in the ground, and volatile organic compounds contained in the contaminated soil are Aeration is efficiently performed by the mechanical and forced action by mixing and stirring.
[0037]
That is, the entire region of the chainsaw 17 located in the ground and its surroundings are to be referred to as an aeration zone. That is, by forming the aeration zone in the ground, the installation of the aeration device on the ground 5 can be omitted.
[0038]
As shown in FIG. 3, an air supply 18 is installed on the ground 5, and air is injected from the air supply 18 into the drilling rig 14. Here, as the air supplier 18, for example, a compressor without an aftercooler, a steam generator, or the like is preferable. The air may contain components other than the atmosphere, but it is desirable to use a high-temperature air. This is because the vaporization of the volatile organic compound can be promoted.
[0039]
Further, on the ground 5, a discharge liquid supply device 19 is provided, and the discharge liquid supply device 19 supplies the discharge liquid to the drilling device 14. Here, in this embodiment, the discharge liquid supply device 19 supplies different types of discharge liquid during soil improvement and during formation of the ground improvement body.
[0040]
As the discharge liquid during soil improvement, water or heavy liquid is desirable. This is because floating of DNAPL (Dense Non Aqueous Phase Liquid) occupying most of the volatile organic compounds can be promoted.
[0041]
When a chemical solution capable of detoxifying a volatile organic compound can be used, it is desirable to add it.
[0042]
The liquid discharged during formation of the ground improvement body is cement milk or the like as a solidifying agent.
[0043]
In addition, the discharge liquid supply device 19 which discharges these discharge liquids individually may be provided. Of course, when the formation of the ground improvement body is omitted, the discharge of the solidifying agent may be stopped.
[0044]
Further, one end of a suction pipe 20 communicating with the internal space S is connected to the lower cover 11a, and the other end of the suction pipe 20 sucks gas (including a volatile organic compound) in the internal space S. And a suction fan 21 for feeding to the gas recovery device 22 by pressure.
[0045]
The gas recovery device 22 has an activated carbon adsorption device and the like inside, recovers volatile organic compounds, and releases purified gas to the atmosphere.
[0046]
The concentration meter 23 measures the concentration of the volatile organic compound in the gas pumped by the suction fan 21. Then, the rotation of the chainsaw 17 (that is, mixing and stirring) and the recovery of the volatile organic compound by the gas recovery device 22 continue until the concentration of the volatile organic compound measured by the densitometer 23 becomes equal to or less than a certain reference value. Is implemented.
[0047]
The supply of the discharged liquid and the press-fitting of the air may be performed simultaneously with the excavation by the excavator 14, or may be performed after the excavation by the excavator 14 is completed (after reaching the predetermined depth H). Is also good. However, when the underground is already sufficiently fluidized, the ejection of the ejection liquid may be omitted.
[0048]
Next, a more detailed description will be given with reference to FIGS. FIG. 4 shows a state where the excavation by the excavator 14 has been completed and the lower end of the excavator 14 has reached the predetermined depth H.
[0049]
At this time, since the upper cover 11b descends integrally with the excavator 14, the bellows 11c is contracted as apparent from comparison with FIG. Also at this time, since the internal space S of the cover 11 is isolated from the outside air, the volatile organic compound does not leak from the internal space S to the outside.
[0050]
Although not shown in FIG. 3, pits 24 having an area larger than the vertical hole 3 (see FIG. 5) are formed near the ground 5 of the vertical hole 3. For the formation of the pit 24, the excavator 14 may be used, or another device or tool may be used. The pit 24 does not need to be so deep.
[0051]
As described above, in the state of FIG. 4, the entire area of the chainsaw 17 located underground is an aeration zone. That is, in the descending zone indicated by the arrow N2, the ascending zone indicated by the arrow N3, and the return zone indicated by the arrow N4, the fluidized contaminated soil and the injected air are forcibly and mechanically mixed and stirred, and volatilized. Organic compounds are aerated.
[0052]
Then, in the return zone indicated by the arrow N4, the aerated contaminated soil containing the volatile organic compound temporarily stays in the pit 24 and flows in the pit 24, as shown in FIG.
[0053]
At this time, the inside of the internal space S is slightly lower than the atmospheric pressure by being sucked by the suction fan 21, and in the pit 24, the contaminated soil (including the volatile organic compound) is removed. Touch S. Naturally, as described in the section of the prior art, volatile organic compounds are hardly soluble in water and easily volatilized into the atmosphere. Further, since they have already been aerated, they can easily volatilize into the internal space S in the pit 24. It is separated from the contaminated soil and collected by a gas recovery device 22 via a suction fan 21.
[0054]
In this embodiment, since the element that enlarges the surface area of the vertical hole 3 in contact with the internal space S, such as the pit 24, is used, the volatile organic compound can be more efficiently recovered.
[0055]
After the above soil improvement, the discharged liquid is changed to a solidifying agent, the excavator 14 is raised to the surface of the ground, and the solidifying agent is solidified, whereby a ground improvement body can be formed in the vertical hole 3. As described above, both the soil improvement and the formation of the ground improvement body can be performed only by the improvement device 10.
[0056]
【The invention's effect】
According to the present invention, the following effects can be obtained.
(1) There is no need to provide a large-scale aeration device on the ground, and the equipment can be simplified.
(2) Consistently applied to a wide range with few restrictions.
(3) The construction period is short and economical.
[Brief description of the drawings]
FIG. 1 is a plan view of an example of a site in an embodiment of the present invention. FIG. 2 is a sectional view of the same. FIG. 3 is an elevation view of the excavator. FIG. 4 is an elevation view of the excavator. Plan view of the pit [Explanation of symbols]
REFERENCE SIGNS LIST 1 Hot spot 2 Surrounding area 3 Vertical hole 4 Underground continuous wall 5 Ground 10 Improvement device 11 Cover 11a Lower cover 11b Upper cover 11c Bellows 12 Hanging fitting 13 Wire 14 Drilling device 15 Drive roller 16 Return roller 17 Chainsaw 18 Air supply device 19 Discharge liquid supply device 20 Suction pipe 21 Suction fan 22 Gas recovery device 23 Densitometer 24 Pit S Internal space S1 Improved area S2 Improved area S3 Unimproved area H Constant depth

Claims (6)

Contaminated soil by volatile organic compounds is distributed, so as to cover a hot spot, forming a plurality of vertical holes in the ground, for each vertical hole, a method of improving the soil,
The vertical hole,
A cover that blocks the internal space from outside air,
A digging device having a chainsaw that is housed in the inner space of the covering body and that digs into the ground and retreats into the ground in the inner space,
By discharging the discharge liquid into the vertical hole, pressurizing air into the vertical hole, and rotating the chainsaw of the excavator,
Around the chainsaw, the fluidized contaminated soil and the injected air are mixed and agitated to aerate volatile organic compounds contained in the contaminated soil,
Guiding contaminated soil to the internal space, in the internal space, volatilizes volatile organic compounds and separates volatile organic compounds in the internal space from the contaminated soil,
A method for treating contaminated soil with volatile organic compounds. The method for treating contaminated soil with a volatile organic compound according to claim 1, wherein the volatile organic compound is sucked into the gas recovery device from the internal space to recover the volatile organic compound. The treatment of the contaminated soil with the volatile organic compound according to claim 1 or 2, wherein the concentration of the volatile organic compound sucked into the gas recovery device is measured, and the chainsaw is continuously rotated until the concentration falls within a certain range. Method. The method for treating contaminated soil with a volatile organic compound according to claim 1, wherein after soil improvement, a solidified liquid is injected into the vertical hole to form a ground improvement body. 5. The method for treating contaminated soil with a volatile organic compound according to claim 1, wherein an underground continuous wall surrounding at least the hot spot is formed prior to soil improvement. A drilling rig with a chainsaw that drills into the ground and retreats into the ground,
A cover body surrounding the drilling rig and shielding its internal space from outside air;
A discharge liquid supply device that discharges a discharge liquid into a vertical hole formed by the excavation device,
An air supply device for pressurizing air into the vertical hole,
The improvement device, wherein the cover is formed to be able to expand and contract in accordance with the movement of the excavator.

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