JP3634849B2 - Method and apparatus for treating contaminated soil with volatile organic compounds - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating contaminated soil with a volatile organic compound and an improved apparatus used therefor.
[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 Have been used in large quantities for various purposes such as cleaning of IC substrates and electronic parts, pretreatment cleaning of metal parts, and solvents for dry cleaning.
[0003]
Except for benzene, volatile organic compounds have a specific gravity greater than that of water, are not easily dissolved in water, and have a high vapor pressure, so that they easily evaporate into the atmosphere.
[0004]
For this reason, a hot spot (contamination center) of contaminated soil by volatile organic compounds is formed at the site where volatile organic compounds are used or where volatile organic compounds have moved through the groundwater surface, etc., and countermeasures are taken. There is an urgent need.
[0005]
There is an air sparging method as a permanent measure for volatile organic compounds that satisfies in-situ purification, no need for pumping groundwater, and no use of quicklime.
[0006]
The air sparging method is mainly used in Europe and the United States, and air is injected into soil and groundwater contaminated with volatile organic compounds as an analogy of soil gas suction using an air sparging well, Disturb the air flow between soil particles to promote the vaporization of volatile organic compounds.
[Patent Document 1]
"Purification of contaminated groundwater by air sparging" Issued by the Ministry of the Environment, Environmental Management Bureau, Water Environment Department, Soil Environment Division 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 being unable to use due to groundwater surface (saturated / unsaturated).
(3) A short circuit occurs due to problems unique to the well construction method (anisotropy of the formation (eg, heterogeneity, discontinuous surfaces such as layering and cracks)) and the formation and uneven distribution of air grooves along the peripheral surface of the well. Effect is insufficient).
(4) The construction period is long and the cost is high.
[0008]
Accordingly, an object of the present invention is to provide a method for treating contaminated soil with a volatile organic compound, which can simplify the scale of equipment, has few restrictions, and is economical.
[0009]
[Means for Solving the Problems]
A method for treating contaminated soil with a volatile organic compound according to claim 1,
A method of improving the soil for each vertical hole by forming a plurality of vertical holes in the ground so as to cover hot spots where soil contaminated with volatile organic compounds is distributed.
The vertical hole is
A covering that blocks the internal space from the outside air;
A drilling device having a chainsaw that is housed in the interior space of the cover body and that excavates in the ground and advances and retracts into the ground in the interior space,
By discharging the discharge liquid into the vertical hole, press-fitting air into the vertical hole, and rotating the chain saw of the excavator,
Around the chainsaw, fluidized contaminated soil and pressurized air are mixed and stirred to aerate volatile organic compounds contained in the contaminated soil.
The contaminated soil is guided to the internal space, and the volatile organic compound is volatilized in the internal space to separate the volatile organic compound from the contaminated soil in the internal space.
[0010]
In this configuration, the fluidized contaminated soil and the injected air are mechanically mixed and agitated by the chainsaw to aerate volatile organic compounds contained in the contaminated soil. For this reason, the chainsaw and its surroundings function as an aeration apparatus, and it is not necessary to provide a large-scale aeration apparatus 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 saturation zone / unsaturation zone, permeable layer / impermeable layer, or the hardness of the ground. There are few restrictions.
[0012]
Furthermore, since this mechanical (forced) mixing / stirring is used, the efficiency of vaporization or decomposition of volatile organic compounds is higher than that of the suction method or the well method, the construction period can be shortened, and the cost can be reduced. .
[0013]
Moreover, since the vertical holes can be easily moved to a free position on the ground surface in a plan view, a plurality of vertical holes are formed, including the entire hot spot or its surrounding area, and it is easy to improve the soil. It is effective.
[0014]
In the method for treating contaminated soil with a volatile organic compound according to claim 2, the volatile organic compound is sucked into the gas recovery device from the internal space, and the volatile organic compound is recovered.
[0015]
In this configuration, the gas recovery device can recover the volatile organic compound and purify the inside of the vertical hole and the inside space.
[0016]
In the method for treating contaminated soil with a volatile organic compound according to claim 3, 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 results can be easily guaranteed.
[0018]
In the method for treating contaminated soil with the volatile organic compound according to claim 4, after the soil improvement, the solidified liquid is injected into the vertical hole to form a ground improvement body.
[0019]
In this configuration, by forming the ground improvement body, even if a small amount of the volatile organic compound remains in the vertical hole, it can be sealed and diffusion to the outside can be prevented. In addition, the strength of the purified soil can be increased and its utility value can be improved.
[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 a hot spot is formed.
[0021]
In this configuration, by forming the underground continuous wall, it is possible to seal the volatile organic compound and prevent the diffusion to the outside.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of an example of a site in one embodiment of the present invention, and FIG. 2 is a sectional view thereof.
[0023]
First, as shown in FIG. 1, prior to the formation of the vertical hole 3, the underground continuous wall 4 surrounding the hot spot 1 is formed. In this 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, the soil is not improved, and a solidifying agent such as cement milk is supplied and solidified.
[0024]
Next, a plurality of vertical holes (square columnar shapes) 3 are formed in the hot spot 1 of the contaminated soil due to the volatile organic compound, and the hot spot 1 is covered by the vertical holes 3. More desirably, the vertical hole 3 is also formed in the peripheral region 2 of the hot spot 1. The method for forming each vertical hole 3 will be described in detail later.
[0025]
In the state shown in FIGS. 1 and 2, the soil improvement is completed to the predetermined depth H for the vertical hole 3 in the improved region S <b> 1, and the current soil improvement is currently performed for the vertical hole 3 in the improving region S <b> 2. The vertical hole 3 in the unimproved region S3 is improved after the soil improvement for the vertical hole 3 in the improved region S2 is completed.
[0026]
Here, the improvement apparatus 10 is provided with a hanging bracket 12 on the top thereof, and the lower end portion of the wire 13 suspended from a crane vehicle (not shown) is connected to the hanging bracket 12. Therefore, by moving the crane vehicle 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 superior in position-related mobility compared to 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 improved apparatus 10 and movement in the Z direction will be described with reference to FIG. FIG. 3 is an elevational view of the excavator and shows a state before starting excavation in the ground.
[0029]
As shown in FIG. 3, the improvement device 10 includes a cover body 11 that is vertically stretchable. The internal space S of the cover body 11 is shut off from the outside, and even if the volatile organic compound is volatilized 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 bracket 12 is fixed at the center of the upper surface, a lower end portion of the upper cover 11b, and an upper end portion of the lower cover 11a. And a bellows 11c that can be extended and retracted.
[0031]
The vertically long excavating device 14 is accommodated in the internal space S of the cover body 11. The excavator 14 has a driving roller 15 that is driven by a motor and a speed reducer (not shown) at the upper end 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 “chain saw” in the present specification is sufficient if it can form the rectangular columnar vertical hole 3, and is wider than a general chain saw concept. For example, the shape of the bit of the chainsaw 17 can be variously changed according to the application.
[0033]
That is, when the drive roller 15 is driven and rotates in the direction of the arrow N1, the chain saw 17 descends once after contacting the drive roller 15, and then returns to the ascending direction from the descending direction by contacting the return roller 16. The route that rises and reaches the drive roller 15 circulates.
[0034]
Here, the underground excavation by the excavator 14 (that is, the lowering of the improvement device 10 in the Z direction) proceeds only when the chain saw 17 digs underground in the vicinity of the return roller 16. Usually, at this time, it is not necessary to apply a downward load to the excavator 14, and it is only necessary to feed the wire 13 from the crane truck.
[0035]
In FIG. 3, since the drive roller 15 is pivotally supported with respect to the upper cover 11b, when the upper cover 11b is moved up and down by unwinding / winding the wire 13, the entire excavator 14 is moved. However, it moves up and down integrally with it. The excavator 14 can move up and down arbitrarily in the Z direction with respect to the lower cover 11a.
[0036]
Mixing / stirring of the contaminated soil fluidized by the discharge liquid and the injected air is performed in the entire region of the chain saw 17 located in the ground, and the volatile organic compound contained in the contaminated soil is Aeration is efficiently performed by mechanical and forced action by mixing and stirring.
[0037]
That is, the entire region of the chain saw 17 located in the ground and its surroundings are to be called aeration zones. That is, by forming an aeration zone in the ground, the installation of the aeration apparatus can be omitted on the ground 5.
[0038]
As shown in FIG. 3, an air supplier 18 is installed on the ground 5, and air is press-fitted from the air supplier 18 into the excavator 14. Here, as the air supply unit 18, for example, a compressor from which an aftercooler is removed, a steam generator, or the like is suitable. Air may contain components other than the atmosphere, but it is desirable to use high-temperature air. This is because the vaporization of volatile organic compounds can be promoted.
[0039]
In addition, a discharge liquid supply device 19 is installed on the ground 5, and the discharge liquid is supplied from the discharge liquid supply device 19 to the excavator 14. Here, in this embodiment, the discharge liquid supply device 19 supplies different types of discharge liquid during soil improvement and during ground improvement body formation.
[0040]
As discharge liquid during soil improvement, water or heavy liquid is desirable. This is because it is possible to promote the rise of DNAPL (Dense Non Aqueous Phase Liquid), which accounts for the majority of volatile organic compounds.
[0041]
Further, when a chemical solution capable of detoxifying volatile organic compounds can be used, it is desirable to add it.
[0042]
The discharged liquid during formation of the ground improvement body is cement milk or the like as a solidifying agent.
[0043]
In addition, you may install the discharge liquid supply device 19 which discharges these discharge liquids individually, and of course, when omitting the formation of the ground improvement body, the discharge of the solidifying agent may be stopped.
[0044]
Furthermore, 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 volatile organic compounds) in the internal space S. Then, a suction fan 21 for pressure feeding to the gas recovery device 22 is connected.
[0045]
The gas recovery device 22 includes an activated carbon adsorption device and the like inside, recovers a volatile organic compound, and releases the 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 / stirring) and the recovery of the volatile organic compound by the gas recovery device 22 are continued until the concentration of the volatile organic compound measured by the densitometer 23 falls below a certain reference value. Implemented.
[0047]
The supply of the discharge liquid and the press-fitting of the air may be performed simultaneously with the excavation by the excavator 14 or after the excavation by the excavator 14 is completed (after reaching the predetermined depth H). Also good. However, when the underground is already sufficiently fluidized, the discharge of the discharge liquid may be omitted.
[0048]
Next, it will be described in more detail with reference to FIG. 4 and FIG. FIG. 4 shows a state in which excavation by the excavator 14 is completed and the lower end portion of the excavator 14 has reached a predetermined depth H.
[0049]
At this time, since the upper cover 11b is lowered integrally with the excavator 14, the bellows 11c is contracted as is apparent from comparison with FIG. Also at this time, since the internal space S of the cover body 11 is blocked 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 that of the vertical hole 3 (see FIG. 5) are formed in the vicinity of 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 region located in the ground of the chainsaw 17 is an aeration zone. That is, in the descending zone indicated by the arrow N2, the rising zone indicated by the arrow N3, and the turning zone indicated by the arrow N4, the fluidized contaminated soil and the injected air are forcibly and mechanically mixed and stirred to volatilize. Organic compounds are aerated.
[0052]
In the turn-back zone indicated by arrow N4, the contaminated soil containing the aerated volatile organic compound once stays in the pit 24 and flows in the pit 24 as shown in FIG.
[0053]
At this time, by sucking with the suction fan 21, the pressure in the internal space S is slightly lower than the atmospheric pressure, and this contaminated soil (including volatile organic compounds) is contained in the internal space in the pit 24. Contact S. Of course, as described in the section of the prior art, the volatile organic compound is not easily dissolved in water and easily volatilizes to the atmosphere, and since it has already been aerated, it is easily volatilized in the internal space S in the pit 24. Then, it is separated from the contaminated soil, and is recovered by the gas recovery device 22 through the 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 is used like the pit 24, the volatile organic compound can be recovered more efficiently.
[0055]
After the soil improvement described above, the ground improvement body can be formed in the vertical hole 3 by changing the discharged liquid to the solidifying agent, raising the excavator 14 to the ground surface, and solidifying the solidifying agent. Thus, both the soil improvement and the formation of the ground improvement body can be carried out only by the improvement device 10.
[0056]
【The invention's effect】
The present invention has the following effects.
(1) It is not necessary to provide a large-scale aeration apparatus on the ground, and the facilities can be simplified.
(2) There are few restrictions and it can apply consistently over a wide range.
(3) The construction period is short and economical.
[Brief description of the drawings]
FIG. 1 is a plan view of an example site in one 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]
DESCRIPTION OF SYMBOLS 1 Hot spot 2 Surrounding area 3 Vertical hole 4 Underground continuous wall 5 Ground 10 Improvement apparatus 11 Cover 11a Lower cover 11b Upper cover 11c Bellows 12 Hanging metal fitting 13 Wire 14 Excavation apparatus 15 Driving roller 16 Return roller 17 Chain saw 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 Unmodified area H Constant depth

Claims (6)

A method of improving the soil for each vertical hole by forming a plurality of vertical holes in the ground so as to cover hot spots in which contaminated soil due to volatile organic compounds is distributed.
The vertical hole is
A covering that blocks the internal space from the outside air;
Formed with a drilling device having a chain saw that is housed in the internal space of the cover and that excavates in the ground and advances and retreats into the ground in the internal space,
By discharging the discharge liquid into the vertical hole, press-fitting air into the vertical hole, and rotating the chain saw of the excavator,
Around the chain saw, the fluidized contaminated soil and the injected air are mixed and stirred to aerate volatile organic compounds contained in the contaminated soil,
Guiding the contaminated soil to the internal space, volatilizing volatile organic compounds in the internal space to separate the volatile organic compounds from the contaminated soil in the internal space;
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, and the volatile organic compound is recovered. 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, and the contaminated soil is treated with the volatile organic compound according to claim 1 or 2. Method. The method for treating contaminated soil with a volatile organic compound according to claim 1, wherein after the soil is improved, a solidified solution is formed by injecting a solidified liquid into the vertical holes. The method for treating contaminated soil with a volatile organic compound according to claim 1, wherein a continuous underground wall surrounding at least a hot spot is formed prior to soil improvement. A drilling device having a chainsaw that excavates and advances into and out of the ground;
A cover that surrounds the drilling rig and blocks its internal space from outside air;
A discharge liquid supply device for discharging discharge liquid into a vertical hole formed by excavation by the excavator;
An air supply device for pressurizing air into the vertical hole,
The said cover is an improvement apparatus formed so that expansion-contraction is possible according to the advance / retreat of the said excavation apparatus.

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