JP3684981B2 - Contaminated soil purification method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, while isolating the contaminated soil from the general environment, it relates to the contaminated soil remediation how the groundwater recycling to achieve remediation of contaminated soils.
[0002]
[Prior art]
Examples of applications relating to measures against contaminated soil purification include those described in JP-A-9-267082, JP-A-10-258266, and JP-A-10-277531.
[0003]
The invention described in Japanese Patent Application Laid-Open No. 9-267082 relates to a method for purifying soil contaminated with volatile organic compounds, and forms a purification region using microorganisms against the contaminated region, and the contaminated region and the purified region are separated from each other. Purification is achieved by a circulating gas flow. The invention described in Japanese Patent Application Laid-Open No. 10-258266 relates to a method for purifying soil contaminated with organic waste such as oil in its original position. In this case, the washing water is pressurized and supplied onto the water-impermeable layer, and the washing water is allowed to flow out to the ground while collecting the contaminants.
[0004]
The invention described in Japanese Patent Application Laid-Open No. 10-277531 relates to a purification method by groundwater circulation that can cope with a wide variety of pollution situations and can reduce costs, and has a water injection well surrounding a contaminated area. A pumping well is provided so that the injected water passes through the contaminated area, and the groundwater pumped up from the pumping well is treated with the above-mentioned pollution treatment equipment and returned from the water injection well to the ground again.
[0005]
On the other hand, according to the guidelines of the Environment Agency issued in February 1999, the basic policy for in-situ containment of pollutants is as follows.
(1) There is an impermeable layer in the basement with a layer thickness of 5m or more and a permeability coefficient of 1.0 × 10 ^-5 cm / sec or less.
[0006]
(2) Enclose the area around the contaminated area with a work with water stop function and close it. Specifically, a water shielding structure by constructing steel sheet piles and SMW underground continuous walls (soil mixing walls) can be considered, but the SMW underground continuous walls have a width of 50 cm or more and a water permeability of 1.0 × 10 ^{−. 6} cm / sec or less. Install underground impermeable layers.
[0007]
(3) When treating the groundwater in the contaminated area, remove the pollutant below the environmental standard value by the treatment facility and release it to the outside.
(4) In order to prevent the intrusion of rainwater, etc., a material with a high water shielding function is laid on the surface. Specifically, it becomes a double water-impervious structure of a combination of a water-impervious sheet material and an improved mixed soil layer. When this structure is applied, the processing by the processing facility (3) is not necessarily required.
[0008]
(5) It is desirable to set the groundwater level inside and outside the SMW below the surrounding water level in order to prevent the outflow and diffusion of contaminants outside the planned area.
[0009]
[Problems to be solved by the invention]
The above basic policy is aimed at building the same level of function as the water-impervious structure of the waste disposal site, and it is necessary to make adjustments in the business plan for the initial investment and the occurrence of maintenance costs during private development. It becomes.
[0010]
Other issues are:
(1) Depending on the installation depth of the SMW, there is a great potential for time and economic constraints.
(2) The impervious function of SMW depends on the construction conditions, and it is difficult to secure the impervious function at the laboratory level.
[0011]
(3) It is difficult to set the groundwater level in the contaminated area to a uniform steady water level, and it is difficult to link it to the groundwater level of the surrounding ground.
Etc.
The inventions described in Japanese Patent Laid-Open Nos. 9-267082 and 10-258266 are directed to specific pollutants and cannot be applied to various pollutants.
[0012]
In the case of the invention described in Japanese Patent Application Laid-Open No. 10-277531, it is possible to cope with various types of pollution according to the performance of the ground pollution treatment apparatus. However, in the arrangement of the water injection well and the pumping well, it is possible to secure a circulation route of groundwater. Difficult, there is a risk of contaminants spreading around. Further, the inventions described in the above-mentioned publications do not satisfy the basic policy of the above-mentioned contamination containment policy, and are considered to be insufficient as an alternative method.
[0013]
The present invention has an object to provide a practical polluted soil remediation how capable contaminated cleaning effect equal to or higher than the effect can be expected by, and significant cost reduction in the request by the basic policy is there.
[0014]
[Means for Solving the Problems]
Contaminated soil remediation method according to claim 1 of the present application, so as to surround the contaminated areas, underground impervious wall to reach the groundwater level below the depth of the outer contaminated areas provided, set the water collecting facility contamination in the district A permeation facility is installed inside the vicinity of the underground impermeable wall so as to surround the water collecting facility, at a predetermined distance from the underground impermeable wall, and continuously in a ring shape at a depth equal to or higher than the groundwater level. Then, after pumping up the contaminated groundwater pumped from the water collection facility, the purified groundwater is again infiltrated into the contaminated area from the infiltration facility, and the water is directed vertically to the water collection facility due to the difference in water level. It is characterized by generating horizontal and horizontal groundwater flows .
[0015]
According to the present invention, after the contaminated groundwater pumped from the water collection facility is purified, the groundwater is returned to the ground of the contaminated area again, and the groundwater flows from the high penetration level to the water collection facility where the water level is lowered. By flowing, a contaminated groundwater circulation path is formed, and the contaminated soil can be gradually purified while taking in contaminants in the contaminated soil.
[0016]
For the purification treatment of the pumped contaminated groundwater, various conventionally known purification treatments are performed in one or more stages depending on the type of the pollutant, for example, by a treatment plant provided near the water collection facility. be able to. Further, in the present invention, since is sequencing infiltration facilities in the ring shape, for one or more water collection facilities installed in the contaminated areas, it can form a low groundwater flow biased, contaminated soil efficiency While purifying well, it is possible to prevent the diffusion of pollutants outside the contaminated area.
[0017]
In addition, as a water collection facility, a conventional water collection well (pumping well) is generally used, but the form and scale are not particularly limited as long as it can pump contaminated groundwater. A second aspect of the present invention is the contaminated soil purification method according to the first aspect, wherein the infiltration facility is installed at a predetermined depth equal to or higher than the groundwater level in the ground of the contaminated area.
[0018]
Whereas the water level is lowered according to the amount of pumped water at the water collection facility, the infiltration facility is usually installed above the groundwater level so that the purified groundwater can naturally penetrate into the ground. it can. However, in this case, the water level at the infiltration facility is higher than the water level around the infiltration facility, so depending on the installation location and the amount of infiltration, groundwater that has been subjected to purification treatment but has not been completely removed of pollutants will be discharged outside the contaminated area. There is a risk of spreading.
[0019]
On the other hand, if the infiltration facility is installed at a predetermined depth or less in the ground as described in claim 2, the contamination outside the contaminated area can be controlled by adjusting the pumping amount of the water collection facility and the infiltration amount from the infiltration facility. Ru can be suppressed diffusion of the substance.
[0020]
In the invention according to claim 1, 2 of the present application, it was provided underground barrier water wall to isolate the contaminated areas outside fouling Somechi Zone is order to secure a diffusion preventing pollutant.
[0021]
However, in the case of the present invention, it is not necessary to construct the underground impermeable wall up to the impermeable layer, as in the conventional case, since there is an effect of preventing diffusion of the contaminants without the underground impermeable wall, Sufficient anti-diffusion effect can be expected by setting the depth below groundwater level outside the contaminated area.
[0022]
As the underground water-impervious wall, an SMW underground continuous wall, a steel sheet pile wall, or any other underground continuous wall that can be expected to be water-impervious can be used. According to claim 3 , in the contaminated soil purification method according to claim 1 or 2 , by adjusting the amount of contaminated groundwater pumped by the water collection facility and the amount of seepage from the infiltration facility of the purified groundwater, This is a case where the groundwater level outside the contaminated area is higher than the groundwater level inside the contaminated area near the water wall.
[0023]
As described above, in the vicinity of the water collection facility, the water level is lowered by pumping, thereby causing a difference in the groundwater level between the infiltration facility position and the water collection facility position, and further between the infiltration facility position and the underground impermeable wall position.
Therefore, by adjusting them, the groundwater level on the contaminated area near the underground impermeable wall can be made lower than the groundwater level outside the contaminated area, and satisfies the basic policy (5) in the aforementioned Environmental Agency Guidelines. be able to.
[0026]
If the infiltration facility is installed in the form of a culvert below the specified depth in the ground, the amount of pumped water in the water collection facility and the amount of infiltration from the infiltration facility can be adjusted without making the water level at the infiltration facility higher than necessary. Thus, the diffusion of pollutants outside the contaminated area can be suppressed.
As a concrete form of such a culvert type infiltration facility, for example, a crushed stone or the like is installed outside a perforated pipe provided with a large number of small holes for infiltration in a resin pipe such as a hard vinyl chloride pipe or a metal pipe. In addition, those wound with non-woven fabric to prevent inhalation of soil particles, etc., those using artificial water-permeable materials instead of crushed stones, or around crushed stones or artificial water-permeable materials without using perforated pipes It is conceivable that the material is wound with a suction prevention material. In addition, this infiltration facility is for injecting treated water from the inside to the outside, so if there is no risk of clogging due to surrounding earth and sand, etc., we removed suction prevention materials, crushed stones, and water-permeable materials. A simpler structure may be used.
[0027]
Note that the above is merely a specific example, and there is no particular limitation on the size, form, etc., as long as it can be installed at a predetermined depth in the ground and can infiltrate the contaminated groundwater after purification treatment. .
[0028]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 schematically shows an embodiment of the present invention. A water collecting well 1 is provided as a water collecting facility in a contaminated area I to pump up contaminated groundwater containing pollutants. In the figure, a single water collecting well 1 is shown, but of course, water collecting wells may be provided at a plurality of locations. The water collection well 1 is also used for water quality monitoring.
[0029]
The pumped contaminated groundwater is treated at the treatment plant 2 and then infiltrated into the ground from a culvert type infiltration facility 3 laid at a predetermined depth in the ground of the contaminated area I.
In this example, the underground impermeable wall 4 is constructed so as to surround the contaminated area I. This underground impermeable wall 4 does not reach the impermeable layer U and has a construction depth of a level below the groundwater level outside the contaminated area O.
[0030]
Looking at the groundwater level, the water level in the drainage well 1 where pumping is performed is low, and the water level is high in the culvert type infiltration facility 3 where the treated water is returned to the ground again. In the present embodiment, the culvert type infiltration facility 3 is arranged in an annular shape inside the underground impermeable wall 4 surrounding the contaminated area I and spaced apart from the underground impermeable wall 4 by a predetermined distance. It is structured to generate a groundwater flow due to the difference in water level from the basin to the water collecting well 1 and from the culvert type infiltration facility 3 to the underground impermeable wall 4.
[0031]
Therefore, the groundwater level in the contaminated area I in the vicinity of the underground impermeable wall 4 is adjusted by adjusting the amount of pumped water from the drainage well 1, the depth of the culvert type infiltration facility 3, the amount of treated water infiltrated, etc. It can be below the groundwater level of the outer O, thereby preventing the diffusion of contamination.
[0032]
On the other hand, a polluted groundwater circulation path is formed between the catchment well 1, the treatment plant 2, and the underdrainage infiltration facility 3. By repeating this circulation, pollutants in the soil are gradually removed, You can go clean. In addition, surplus treated water with a low contamination level that is processed and processed by the treatment plant 2 and removed contaminants can be carried out of the area and disposed of depending on conditions.
[0033]
Further, on the ground surface of the contaminated area I, a surface water-impervious work 5 for preventing permeation of rainwater or the like into the ground is installed as necessary. About this surface impermeable work, what is shown by the guideline etc. can be utilized.
2A to 2D show specific examples of the culvert type infiltration facility 3. FIG. 2 (a) has a perforated pipe 11 such as a hard vinyl chloride pipe having a water permeable hole as a core material, and a single-grain crushed stone 12 for securing a water permeable area is laid around it. A suction preventive material 13 made of a nonwoven fabric or the like is wound around the periphery to prevent clogging or the like due to intrusion of soil particles. This form has good water permeability when returning treated water to the ground, but tends to increase laying costs.
[0034]
The infiltration facility 3 in FIG. 2 (b) has a structure in which a fiber drainage material 14 is wound around a perforated pipe 11 in place of the crushed stone 12 in FIG. It has become. The water permeability is inferior to that of FIG. 2 (a), but the cost can be reduced. Examples of the commercially available fiber drainage material 14 include a porous material (trade name: Hetimaron) in which mutual nodes of fibers are welded and integrated.
[0035]
The infiltration facility 3 in FIG. 2 (c) is formed by winding a suction prevention material 13 around a single-grain crushed stone 12 without using a perforated pipe to form a continuous underdrain. Although the cost is the lowest, the water permeability is inferior to that of FIGS. 2 (a) and 2 (b).
The infiltration facility 3 in FIG. 2 (d) uses a fiber drainage material 14 instead of the crushed stone 12 in FIG. 2 (c), and a suction prevention material 13 is wound around it.
[0036]
【The invention's effect】
(1) According to the present invention, after the contaminated groundwater pumped from the water collection facility is purified, it is returned to the ground of the contaminated area again, and the groundwater circulation path is formed, thereby gradually purifying the contaminated soil. Can go.
[0037]
(2) Pumped contaminated groundwater can be purified by, for example, a treatment plant installed near the water collection facility, according to the type of pollutant.
(3) penetration if ask facility is continuous ring shape, toward the water collecting facility can form a low groundwater flow biased, while the contaminated soil was purified efficiently, the diffusion of pollutants into the contaminated areas outside Can be prevented.
[0038]
(4) By infiltrating the purified water into the ground again, it is possible to prevent the effects of land subsidence due to the groundwater level drop.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an embodiment of the present invention.
2 (a) to (d) are cross-sectional views each showing an example of an infiltration facility used in claim 2. FIG.
[Explanation of symbols]
I ... Contaminated area, O ... Outside contaminated area, U ... Impermeable layer, W ... Groundwater level,
DESCRIPTION OF SYMBOLS 1 ... Water collection well, 2 ... Treatment plant, 3 ... Underdrain type penetration facility, 4 ... Underground impermeable wall, 5 ... Surface impermeable construction,
DESCRIPTION OF SYMBOLS 11 ... Perforated pipe, 12 ... Crushed stone, 13 ... Suction prevention material, 14 ... Textile drainage material

Claims (3)

So as to surround the contaminated areas, underground impervious wall to reach the groundwater level below the depth of the outer contaminated areas provided only set the catchment facility contamination area, so as to surround the water collecting facilities, the underground An infiltration facility was installed inside the vicinity of the impermeable wall at a predetermined distance from the underground impermeable wall and continuously in a ring shape at a depth equal to or higher than the groundwater level . After purifying the contaminated groundwater, the purified groundwater is again permeated into the contaminated area from the infiltration facility, and a vertical and horizontal groundwater flow due to a water level difference is generated toward the water collection facility. Contaminated soil purification method.  The contaminated soil purification method according to claim 1, wherein the infiltration facility is installed at a predetermined depth equal to or higher than a groundwater level in the ground of a contaminated area.  By adjusting the amount of contaminated groundwater pumped by the water collection facility and the amount of infiltrated from the infiltration facility for purified groundwater, the groundwater level outside the contaminated area near the underground impermeable wall The method for purifying contaminated soil according to claim 1 or 2, wherein the method is made higher.

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