JP2005021730A - Wall for preventing diffusion of volatile organic compound and method for constructing the wall - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformly and surely remove volatile organic compounds contained in ground water over a long time. <P>SOLUTION: In the construction of a wall 1 for preventing the diffusion of the volatile organic compounds, a mixture 4 of soil 2 and active carbon powder 3 is formed in the shape of a pile to obtain a mixed pile, and the mixed piles are arranged in the shape of columns to form a wall in the ground 5. In order to construct the wall 1, by agitating/mixing the soil 2 of the ground 5 and the active carbon powder 3 in situ, the mixture 4 of the soil 2 and the active carbon powder 3 is formed in the shape of the pile to obtain the mixed pile, and the mixed piles are arranged in the shape of the columns. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５７】
同表でわかるように、土中水中のテトラクロロエチレンの濃度は、初日は０．３ｍｇ／Ｌであったが、活性炭添加１日後には０．００３ｍｇ／Ｌ、２日後には０．００１ｍｇ／Ｌ以下となり、地下水環境基準である０．０１ｍｇ／Ｌを１日後にはクリアできることがわかった。
【００５８】
【発明の効果】
以上述べたように、本発明に係る揮発性有機化合物の拡散防止壁及びその構築方法によれば、拡散防止壁に流入してきた地下水に含まれる揮発性有機化合物は、混合体内の活性炭又は木炭の粉粒体に吸着し、揮発性有機化合物が下流側に拡散するのを防止することが可能となる。
【００５９】
【図面の簡単な説明】
【図１】本実施形態に係る揮発性有機化合物の拡散防止壁を示した図であり、（ａ）は鉛直断面図、（ｂ）はＡ−Ａ線に沿う断面図。
【図２】本実施形態に係る揮発性有機化合物の拡散防止壁の構築手順を示した作業図。
【図３】引き続き本実施形態に係る揮発性有機化合物の拡散防止壁の構築手順を示した作業図。
【図４】引き続き本実施形態に係る揮発性有機化合物の拡散防止壁の構築手順を示した作業図。
【符号の説明】
１ 拡散防止壁
２ 土
３ 活性炭の粉体（活性炭又は木炭の粉粒体）
４ 混合体
５ 地盤
２１ 中空攪拌軸
２４ 攪拌翼[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diffusion preventing wall for volatile organic compounds contained in soil or groundwater and a method for constructing the same.
[0002]
[Prior art]
The soil of the factory site may contain volatile organic compounds (VOC) typified by organochlorine compounds such as trichlorethylene. If such soil is left as it is, the volatile organic compounds will be groundwater. There is a risk of spreading to the surroundings through. Therefore, a predetermined purification process must be performed on such contaminated soil or contaminated groundwater.
[0003]
Various methods have been developed to remove volatile organic compounds. For example, groundwater contaminated with volatile organic compounds is pumped up and treated on the ground, iron powder or oxidized on contaminated soil. There are known a method of decomposing a volatile organic compound by injecting an agent, a method of bioremediation utilizing microbial activity, a method of aeration treatment in an airtight space after excavating contaminated soil.
[0004]
[Patent Document 1]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-119952
[Patent Document 2]
Japanese Patent Laid-Open No. 2001-205248
[Problems to be solved by the invention]
However, each of the conventional treatment methods has its own drawbacks.For example, in the method of pumping up contaminated groundwater, there is a variation in the distribution of contamination combined with the non-uniformity of the ground, so that uniform and reliable purification is difficult. It was happening.
[0007]
In addition, iron powder is used when the volatile organic compound is an organic chlorine compound such as trichlorethylene, but the activity is lost in several months due to the iron powder itself and the formation of an oxide film.
[0008]
In addition, the addition of oxidant and bioremediation require time and cost, and excavation and aeration treatment of contaminated soil is inherently unsuitable for groundwater contamination.
[0009]
The present invention has been made in view of the above-described circumstances, and provides a diffusion prevention wall for volatile organic compounds that can uniformly and reliably remove volatile organic compounds contained in groundwater over a long period of time, and a method for constructing the same. For the purpose.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the diffusion preventing wall of the volatile organic compound according to the present invention forms a mixture of soil and activated carbon or charcoal powder in the shape of a wall in the ground as described in claim 1. It is made.
[0011]
Further, the diffusion preventing wall of the volatile organic compound according to the present invention is such that the mixture is formed in a pile shape to form a mixed pile, and the mixed pile is arranged in a column.
[0012]
Further, the diffusion prevention wall of the volatile organic compound according to the present invention may be configured such that the mixing amount of the activated carbon or the charcoal powder in the mixture is a flow rate of groundwater, a concentration of the volatile organic compound in the groundwater, or a surrounding soil property. It is changed in the depth direction according to.
[0013]
In addition, the method for constructing a diffusion preventing wall for volatile organic compounds according to the present invention, as described in claim 4, comprises mixing the ground soil and activated carbon or charcoal powder in situ to mix the ground. A mixture of the soil and the granular material is formed inside.
[0014]
The volatile organic compound diffusion prevention wall construction method according to the present invention also includes a stirring blade attached to the lower end of the hollow stirring shaft that rotates around the axis of the hollow stirring shaft so that the stirring blade is within the ground. The mixture is piled by ejecting activated carbon or charcoal powder from the discharge port of the hollow stirring shaft or the discharge port of the stirring blade through the conveying space in the hollow stirring shaft while penetrating or pulling out. The mixed piles are formed in a column and arranged in a column.
[0015]
In the diffusion prevention wall of the volatile organic compound according to the present invention, a mixture of soil and activated carbon or charcoal powder is formed into a wall shape in the ground, and the diffusion of the volatile organic compound In the method for constructing a prevention wall, the soil and the activated carbon or charcoal powder are stirred and mixed in situ to form a mixture of the soil and the powder in the ground.
[0016]
If it does in this way, the volatile organic compound contained in the groundwater which has flowed into the diffusion prevention wall will be adsorbed to the activated carbon or charcoal powder in the mixture, and prevent the volatile organic compound from diffusing downstream. be able to.
[0017]
Needless to say, the technology for adsorbing volatile organic compounds (VOC) on activated carbon is already known at the time of filing of the present application. However, it is necessary to remove gasified volatile organic compounds and volatile organic compounds dissolved in water once. It is only known that it is gasified and adsorbed on activated carbon.
[0018]
Here, for the purification of the pumped contaminated groundwater, VOC dissolved in the groundwater was air-entrained by aeration, and the vapor phase VOC contained in the air was adsorbed on the activated carbon.
[0019]
However, the removal of VOCs dissolved in the pumped groundwater has inherent difficulties. That is, since the solubility of VOC in water is low in the first place (several hundred mg / kg to 2,000 mg / kg), even when VOC having a diameter of about 1 cm is a source of contamination, the VOC continues to elute into groundwater for several years. If the source VOC is a stock solution and its volume is high, the VOC will continue to elute into groundwater for decades. This means that facilities such as pumps and activated carbon adsorption towers must continue to operate for decades, which is too impractical in terms of economy.
[0020]
The applicant is not able to reliably and reliably purify groundwater at a location away from the pollution source while taking into account the problem of elution of volatile organic compounds from the pollution source into the groundwater. As a result of various research and development, if it is a non-diffusion wall for volatile organic compounds formed by forming a mixture of soil and activated carbon or charcoal powder in the shape of a wall in the ground, the diffusion The knowledge that volatile organic compounds contained in groundwater passing through the prevention wall can be adsorbed on the activated carbon or charcoal particles in the mixture, thus preventing the diffusion of volatile organic compounds downstream. I came to get.
[0021]
The level of publicly known technology at the time of filing of the present application is limited to the above-mentioned points, and a diffusion preventing wall for volatile organic compounds formed by forming a mixture of soil and activated carbon or charcoal powder in the shape of a wall in the ground. The fact that the groundwater VOC passing through the diffusion barrier wall can be directly adsorbed to the activated carbon or charcoal powder in the mixture is a very useful knowledge in the industry. .
[0022]
Volatile organic compounds, also called VOCs (Volatile Organic Compounds), include dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, 1,1,1-trichloroethane, 1 1,2-trichloroethane, trichloroethylene, tetrachloroethylene, 1,3-dichloropropene, benzene and the like.
[0023]
The granular material includes a so-called powder and a granular material having a particle diameter of about several mm to 1 cm, for example.
[0024]
Here, when the mixing amount of the activated carbon or charcoal powder in the mixture is changed in the depth direction according to the flow rate of groundwater, the concentration of volatile organic compounds in the groundwater or the surrounding soil properties, the downstream It is possible to more reliably and rationally prevent the diffusion of volatile organic compounds into the liquid.
[0025]
In the diffusion prevention wall construction method according to the present invention, how the ground soil is stirred and mixed in situ with the activated carbon or charcoal powder, and how the soil and powder are mixed in the ground. Whether to form a body is arbitrary, but, for example, it is possible to use a DJM method in which an improvement material for a granular material is supplied into a soft ground and stirred with the in-situ soil.
[0026]
That is, by rotating a stirring blade attached to the lower end of the hollow stirring shaft around the axis of the hollow stirring shaft, the stirring blade is excavated or pulled out in the ground, and the conveying space in the hollow stirring shaft is The mixture is formed into a pile by ejecting activated carbon or charcoal powder from the discharge port of the hollow stirring shaft or the discharge port of the stirring blade, and the mixed pile is formed in a columnar shape. You just have to line up.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Embodiments of a diffusion preventing wall for volatile organic compounds and a method for constructing the same according to the present invention will be described below with reference to the accompanying drawings. Note that components that are substantially the same as those of the prior art are assigned the same reference numerals, and descriptions thereof are omitted.
[0028]
FIG. 1 is a view showing a diffusion prevention wall for a volatile organic compound according to the present embodiment. As can be seen in the figure, the diffusion preventing wall 1 of the volatile organic compound according to the present embodiment forms a mixture 4 of the soil 2 and the activated carbon powder 3 in a pile shape to form a mixed pile. The mixed piles are arranged in a column shape and are formed in a wall shape in the ground 5.
[0029]
2 to 4 are views showing a procedure for constructing the volatile organic compound diffusion prevention wall 1 according to this embodiment. As can be seen from these figures, in order to construct the volatile organic compound diffusion prevention wall 1 according to the present embodiment, the ground soil 2 and the activated carbon powder 3 are stirred and mixed in-situ in the ground. A mixture 4 of soil 2 and activated carbon powder 3 is formed in a pile shape in 5 to form a mixed pile, and the mixed pile is arranged in a column.
[0030]
In order to stir and mix the soil 2 and the activated carbon powder 3, the DJM method may be used. That is, first, as shown in FIG. 2, the hollow stirring shaft 21 that is suspended by a base machine (not shown) so as to be rotatable around the vertical axis is positioned so as to be above the planned construction area of the diffusion prevention wall 1. To do.
[0031]
The anti-diffusion wall 1 is preferably constructed downstream of the contamination source where the VOC exists. Moreover, the diameter of the mixing pile which comprises the diffusion prevention wall 1, and the powder amount of the activated carbon in a mixing pile are determined suitably in consideration of the flow rate of a groundwater, and a contamination density | concentration.
[0032]
Next, the stirring blade 24 attached to the lower end of the hollow stirring shaft is rotated by rotating the hollow stirring shaft 21 around the vertical axis in the excavation direction.
[0033]
Here, since the excavation bit 25 protrudes obliquely downward on the lower surface of the agitating blade 24, the hollow agitating shaft 21 and the agitating member are excavated while the ground 5 is excavated downward by rotating the agitating blade 24 in the excavating direction. Wings 24 can penetrate into the ground.
[0034]
FIG. 3 shows a state where the hollow stirring shaft 21 and the stirring blade 24 are penetrated into the ground 5, and a region through which the stirring blade 24 has passed becomes a disturbance region 41.
[0035]
Next, as shown in FIG. 4, while the hollow stirring shaft 21 and the stirring blade 24 are rotated in the reverse direction, they are pulled out from the disturbance region 41. In this drawing step, the hollow stirring shaft 21 and the stirring blade 24 are transported through the transport space in the hollow stirring shaft 21. The activated carbon powder 3 thus produced is ejected from a discharge port 31 provided in the stirring blade 24.
[0036]
If it does in this way, the mixture 4 of the soil 2 and the powder 3 of activated carbon will be formed in the pile shape in the ground 5, and will become a mixed pile.
[0037]
Hereinafter, the mixing piles are arranged in a column while sequentially constructing new mixing piles in the same procedure as described above, and the diffusion prevention wall 1 shown in FIG. 1 is constructed.
[0038]
In the volatile organic compound diffusion prevention wall and its construction method according to the present embodiment, the volatile organic compound contained in the groundwater flowing into the diffusion prevention wall 1 is adsorbed on the activated carbon powder 3 in the mixture 4. To do.
[0039]
As described above, according to the volatile organic compound diffusion prevention wall and the construction method thereof according to this embodiment, the volatile organic compound contained in the groundwater flowing into the diffusion prevention wall 1 is contained in the mixture 4. It becomes possible to prevent the volatile organic compound from being diffused to the downstream side by adsorbing to the activated carbon powder 3.
[0040]
Further, according to the volatile organic compound diffusion prevention wall and the construction method thereof according to the present embodiment, when the VOC of the pollution source is, for example, a stock solution, the VOC eluted from the pollution source has contaminated the groundwater for decades. Even if it continues, the diffusion to the downstream of VOC can be prevented for a long period of time by adsorbing VOC in groundwater to the powder 3 of activated carbon.
[0041]
Of course, in such a long period of time, the adsorption function of the powder 3 is lowered, and it is assumed that the diffusion prevention wall 1 must be reconstructed. However, the groundwater pumping equipment and the gasified volatile organic compound are activated carbon. Compared to maintaining conventional facilities such as a transport facility that feeds the adsorption tower, the volatile organic compound diffusion prevention wall 1 according to the present embodiment does not require any such maintenance cost. There is no need for maintenance and the overall economy is much better.
[0042]
Further, according to the diffusion preventing wall for volatile organic compounds and the construction method thereof according to the present embodiment, the mixture 4 is formed by mixing the soil 2 and the activated carbon powder 3 with stirring. Permeability is secured and there is no concern of hindering the flow of groundwater.
[0043]
In this embodiment, the DJM method used for soft ground improvement is diverted as a means of stirring and mixing, but an apparatus or method for stirring and mixing soil and activated carbon or charcoal powder is arbitrary, for example, CDM You may make it divert a construction method.
[0044]
The CDM method is also a known method for soft ground improvement, and explanation of the contents is omitted, but when applied to the present invention, activated carbon or charcoal powder is added to water in advance and slurried, This may be sent to the planned construction area of the diffusion prevention wall and stirred and mixed in place with the soil of the planned construction area.
[0045]
In addition, when constructing a diffusion prevention wall in the ground that cannot be excavated by the soft ground improvement device in this way or in which the excavation efficiency is poor, in other words, in the ground that has a large earth strength and a good ground, for example, excavate the ground with an earth auger However, the slurry and activated carbon or charcoal powder may be stirred and mixed by ejecting a slurry in which activated carbon or charcoal powder is added to water in advance from the tip.
[0046]
In any case, the stirring and mixing means may be appropriately selected from known means in consideration of the soil properties and depth of the ground.
[0047]
Further, in the present embodiment and the modification thereof, the diffusion prevention wall is constructed by performing the stirring and mixing of the soil of the ground and the activated carbon or charcoal powder in the original position, but the mixing and mixing is not necessarily performed in the original position. There is no need to do this.
[0048]
That is, excavate the planned construction area of the diffusion prevention wall, stir and mix the excavated soil with activated carbon or charcoal particles on the ground to form a mixed soil, and backfill the mixed soil to form a mixture. It doesn't matter.
[0049]
Since the operation after the backfilling is the same as that of the above-described embodiment, the description thereof is omitted here.
[0050]
Although not particularly mentioned in the present embodiment, the diffusion prevention wall 1 is not necessarily a straight wall (a wall that is not curved), and may be a curved wall. In particular, when the VOC is constructed downstream of a high concentration contamination source existing in the stock solution, it is desirable to construct a curved diffusion prevention wall so as to surround the contamination source.
[0051]
Although not particularly mentioned in the present embodiment, the mixing amount of the activated carbon powder 3 in the mixture 4 is determined depending on the flow rate of groundwater, the concentration of volatile organic compounds in the groundwater, or the surrounding soil properties. You may make it change to a direction.
[0052]
According to such a configuration, it becomes possible to more reliably and rationally prevent the diffusion of the volatile organic compound downstream.
[0053]
[Example 1]
First, an elution test was conducted to determine whether the groundwater environmental standards could be cleared by adding activated carbon. The outline and results will be described below.
[0054]
The test method was added 2g of powdered activated carbon tetrachlorethylene content per soil 1 m ³ is relative to contaminated soil 1L of 1.6g, then placed in a glass bottle of water was added 200 mL, this sealed storage to stir did.
[0055]
Table 1 shows the results of collecting the soil water and analyzing the tetrachlorethylene concentration one day and two days after the addition of the activated carbon.
[0056]
[Table 1]

[0057]
As can be seen from the table, the concentration of tetrachlorethylene in soil water was 0.3 mg / L on the first day, but 0.003 mg / L after 1 day of addition of activated carbon and 0.001 mg / L or less after 2 days. It was found that the groundwater environmental standard of 0.01 mg / L can be cleared after one day.
[0058]
【The invention's effect】
As described above, according to the volatile organic compound diffusion prevention wall and the construction method thereof according to the present invention, the volatile organic compound contained in the groundwater flowing into the diffusion prevention wall is activated carbon or charcoal in the mixture. It becomes possible to prevent the volatile organic compound from being diffused to the downstream side by being adsorbed on the granular material.
[0059]
[Brief description of the drawings]
1A and 1B are diagrams showing a diffusion prevention wall for a volatile organic compound according to the present embodiment, wherein FIG. 1A is a vertical cross-sectional view, and FIG. 1B is a cross-sectional view taken along line AA.
FIG. 2 is a work diagram illustrating a procedure for constructing a volatile organic compound diffusion prevention wall according to the present embodiment.
FIG. 3 is a work diagram illustrating a procedure for constructing a volatile organic compound diffusion prevention wall according to the present embodiment.
FIG. 4 is a work diagram illustrating a procedure for constructing a volatile organic compound diffusion prevention wall according to the present embodiment.
[Explanation of symbols]
1 Diffusion prevention wall 2 Soil 3 Activated carbon powder (activated carbon or charcoal powder)
4 Mixture 5 Ground 21 Hollow stirring shaft 24 Stirring blade

Claims (5)

A diffusion preventing wall for volatile organic compounds, wherein a mixture of soil and activated carbon or charcoal powder is formed into a wall shape in the ground. The volatile organic compound diffusion-preventing wall according to claim 1, wherein the mixture is formed in a pile shape to form a mixed pile and the mixed pile is arranged in a column. The volatilization according to claim 1, wherein the mixing amount of the activated carbon or charcoal powder in the mixture is changed in the depth direction according to the flow rate of groundwater, the concentration of volatile organic compounds in groundwater, or the surrounding soil properties. For preventing the diffusion of organic compounds. A mixture of the soil and the granular material is formed in the ground by stirring and mixing the ground soil and activated carbon or charcoal powder in situ. Diffusion prevention wall construction method. By rotating a stirring blade attached to the lower end of the hollow stirring shaft around the axis of the hollow stirring shaft, the stirring blade is excavated and pulled out in the ground, and is passed through the conveyance space in the hollow stirring shaft. The mixture is formed into a pile by ejecting activated carbon or charcoal powder from the discharge port of the hollow stirring shaft or the discharge port of the stirring blade, and the mixed pile is arranged in a column. The method for constructing a diffusion-preventing wall for volatile organic compounds according to claim 4.

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