JP2002001362A - Groundwater cleaning structure and method of cleaning groundwater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a groundwater cleaning structure capable of exhibiting cleaning effect in an early stage in a contaminated ground with small water permeability and capable of treating the contaminated groundwater over a wide area at the site with a reduced execution cost. SOLUTION: In the whole area of the contaminated ground G, where the fluidization of the groundwater does not occur, a prescribed number of cleaning piles 11 placed in prescribed positions are provided and the cleaning pile contains a decomposition material for a contaminated material, a stabilizing material or an adsorptive material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a groundwater purification structure and a groundwater purification method for purifying groundwater contaminated with an organic halogen compound or heavy metal (hereinafter referred to as "contaminated groundwater").

[0002]

2. Description of the Related Art As a method of purifying contaminated groundwater in situ (hereinafter referred to as "in situ purification method"), there is a permeable groundwater purification wall method, which is attracting attention as a maintenance-free purification method. . As shown in FIG. 4, this permeable groundwater purifying wall construction method uses a permeable groundwater purifying wall (hereinafter referred to as a "permeated groundwater purifying wall") containing a permeable purifying material downstream of the flow of the contaminated groundwater W 'in the contaminated ground G'. Sex purification wall 1
1 ')) and the permeable purifying wall 1 if necessary.
This is a method of constructing a pair of water blocking walls 12 ′ on both sides of 1 ′ and purifying the contaminated groundwater W ′ by permeating the permeable purification wall 11 ′.

[0003]

However, the contaminated ground G '
If the water permeability is low, there is a problem that the time required for the contaminated groundwater W 'to reach the permeable purification wall 11' and pass therethrough is very long, and it takes a long time for the purification effect to appear. Was.

In the above case, it is conceivable that the entire area of the contaminated ground G 'may be replaced with a purification material.
Practical application was difficult because the construction work and the construction cost became enormous.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to quickly produce an effect of purification on a contaminated ground having a low water permeability and to reduce the construction cost. It is an object of the present invention to provide a groundwater purification structure and a groundwater purification method capable of purifying a wide range of contaminated groundwater in situ while planning.

[0006]

In order to solve the above-mentioned problem, the present invention according to claim 1 has a structure in which a predetermined number of a predetermined number of pavements are installed at predetermined positions in a contaminated ground where no groundwater flow occurs. The present invention provides a groundwater purification structure including a purification pile, wherein the purification pile contains a decomposition material, a stabilization material, or an adsorption material for pollutants.

[0007] Here, that the groundwater flow does not occur does not mean that the groundwater does not flow in the ground at all, but that the flow rate of the groundwater is extremely small (the hydraulic conductivity of the ground is 10 ^-5 cm). / Sec or less, and the groundwater flow velocity is 5 cm or less per year).

[0008] The purification pile is a material for decomposing pollutants,
It refers to a pile containing at least one type of purification material, a stabilizing material or an adsorption material, as a constituent material. Various materials can be used as the purification material, and can be appropriately selected depending on the type of pollutant contained in the contaminated ground.

For example, the decomposition material is a substance having a property of decomposing and detoxifying the contaminant by reacting with the contaminant. When an organic halogen compound is contained as a pollutant, a predetermined effect can be obtained by using iron powder as a decomposition material. A stabilizing material is a substance that has the property of reacting directly or indirectly with a contaminant to form an insoluble substance. The adsorptive material is a porous material capable of adsorbing contaminants by its adsorptive capacity, and includes activated carbon, coal ash, charcoal, lignite, zeolite, bentonite, and the like.

In addition, when a material obtained by mixing a metal reducing agent and a fine aggregate having water permeability such as silica sand or crushed stone is used as the purifying material, since the purifying material has sufficient permeability, It is possible to avoid clogging due to corrosion of metal reducing agents and precipitation of calcium salts, maintain desired water permeability for a long period after the start of operation, and to purify contaminated water by organic halogen compounds and heavy metals. It is suitable for.

Therefore, according to the present invention, by laying a predetermined number of purification piles directly on the contaminated ground, it becomes possible to purify the contaminated groundwater in situ even on the contaminated ground without groundwater flow.

Further, according to the present invention described in claim 2,
The groundwater purification structure according to claim 1, wherein:
By properly setting the interval between the purification piles adjacent vertically or diagonally within a range of 5 times or less the pile diameter, the arrangement of the purification piles can be determined most efficiently, so the minimum construction cost It can be.

Further, according to the present invention described in claim 3,
In the underground water purification structure according to claim 1 or 2, a monitoring hole is formed at a predetermined position on the contaminated ground to easily observe a state of purification of the contaminated ground and take appropriate measures. Becomes possible.

Further, according to the present invention, a predetermined number of purification piles containing a decomposing material, a stabilizing material, or an adsorbing material for pollutants are provided in the entire area of the contaminated ground where the groundwater flow is not generated. The present invention provides a groundwater purification method characterized by purifying groundwater at an original position by casting at a position.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
This will be described in detail with reference to the drawings. In addition, the target ground G is
It is a wide ground with a source of pollution, such as in a factory premises, and has low water permeability and hardly any groundwater flow.

As shown in FIG. 1, a groundwater purifying structure 10 of the present invention comprises a plurality of purification piles 11 installed on a contaminated ground G.
And a monitoring hole 12 formed at a predetermined position of the contaminated ground G. The purification pile 11 is a cylindrical pile in which iron powder as a metal reducing agent and silica sand are mixed.
Here, the reason why not only iron powder but also silica sand is mixed is considered that corrosion of iron powder occurs or calcium salt precipitates in gaps by sufficiently securing the permeability of the purification pile 11. The purpose of the present invention is to extend the life of the groundwater purification structure 10. Therefore, if the same purpose can be achieved, fine aggregate having water permeability equivalent to silica sand may be used instead of silica sand.

In addition, the purification pile 11 is arranged such that the interval between the purification piles 11A to 11I adjacent vertically and horizontally, and diagonally is 5 times or less the pile diameter over the entire area of the contaminated ground G. It is cast in a grid. In addition, the purification pile 11 can be appropriately selected according to the condition of the contaminated ground G, such as a staggered shape or a concentric shape instead of a lattice shape.

The monitoring holes 12 are provided for taking polluted groundwater from the contaminated ground G and observing the water quality. A predetermined number of the monitoring holes 12 can be provided at a desired position and a predetermined depth of the contaminated ground G. In the present embodiment, it is provided at a substantially central portion of the contaminated ground G and at an intermediate portion between the adjacent purification piles 11A and 11C.

The present invention employs a construction method in which a plurality of columnar piles are easily formed by burying a purification material in a drilled hole while preventing collapse of the ground using a casing pipe. it can. Therefore, material separation of the purification material having permeability, which is generally inevitable, can be significantly suppressed, and the permeability of contaminated groundwater can be sufficiently ensured, and the permeability can be maintained for a long time. It will be more complete and easier to achieve.

The operation of the underground water purification structure 10 of the present invention is as follows. The present invention provides an iron powder (metal-reducing agent) by placing a plurality of purification piles 11 directly on the contaminated ground G.
The pollutant can be removed from the contaminated groundwater by a reduction reaction between the pollutant and the pollutant B. Therefore, even in the contaminated ground G where there is no groundwater flow, the contaminated groundwater can be purified in situ. This is because the concentration of the pollutant decreases inside the purification pile 11 and the periphery of the purification pile 11 and the purification pile 11 are removed.
This is due to a mechanism in which only the pollutant B is collected in the purification pile portion and purified by the effect of concentration diffusion even when the flow of groundwater is not generated due to a difference in concentration of the pollutant between the inside and the inside. (See FIG. 2).

Thus, even when the plurality of purification piles 11 are set in a grid (intermittently arranged in a row), the reduction reaction between the iron powder (metal reducing agent) and the contaminant B occurs. The purification power substantially extends not only to the cross-sectional area of each purification pile 11 but also to the outer area R. Therefore, it is not necessary to replace the entire area of the contaminated ground G with the purification material, and the construction cost can be significantly reduced. At this time, since it has been proven that one purification pile 11 has an influence range (corresponding to the outer region R) of up to 2.5 times the pile diameter (see the example), the adjacent purification pile 11 is purified. By setting the interval between the piles 11A to 11I to be five times or less the pile diameter, the arrangement of the purification pile 11 can be determined most efficiently.

In the groundwater purifying structure 10 of the present invention,
Since the monitoring hole 12 is formed at a predetermined position of the contaminated ground G, the state of purification of the contaminated ground G can be easily observed by constantly monitoring the water quality of the monitoring hole 12 or at predetermined intervals, Appropriate measures can be taken as needed.

As described above, an example of a preferred embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and the design of each of the above-described components can be appropriately changed without departing from the spirit of the present invention. In particular,
As the purification material, various materials can be used depending on the type of the pollutant. As such a purifying material, for example, a metal reducing agent such as iron powder, an adsorbing substance such as activated carbon particles or a material having a purifying action such as a chelating resin particle alone, or a material such as fine aggregate and fine aggregates A material obtained by mixing materials having no purification action in a composition that does not lose the purification action may be used. Also, regarding the number, diameter, pile length, etc. of purification piles,
Selection is possible, and purification piles with different pile diameters may be cast. Further, a plurality of purification piles in which the ratio of the purification material is appropriately changed may be installed.

[0024]

EXAMPLE An in-situ test was performed to confirm the effect of a purification pile in the groundwater purification structure 10 of the present invention. The exam is
A 1.0 m diameter purification pile (purification material was iron powder) was placed in the contaminated ground, and the concentration of contaminated groundwater in a monitoring hole installed 20 cm apart from the purification pile was measured. FIG. 3 shows the time-dependent change in the concentration of contaminated groundwater in the monitoring hole. The horizontal axis represents the elapsed days (days), and the vertical axis represents the groundwater concentration at the start of the measurement.
The relative concentration of the pollutant contained in the contaminated groundwater W is set to 0.

According to the results, a decrease in the concentration was observed also in the monitoring hole provided at a distance from the purification pile, and a dramatic decrease in the concentration was observed particularly until the lapse of 10 days. This is because the concentration of pollutants decreases inside the purification pile, causing a difference in the concentration of the pollutant between the periphery of the purification pile and the inside of the purification pile. This is due to the mechanism that only pollutants collect in the purification pile and are purified by the effect of the above. Thus, by installing the purification pile at an appropriate interval on the contaminated ground, the contaminated groundwater can be efficiently purified even when there is no groundwater flow.

The initial concentration (C ₀ ) of the contaminant in the contaminated ground, the dry density and porosity of the ground forming the contaminated ground, and the diffusion coefficient (D) of the contaminant are determined by a governing equation (Boundary condition). Pile diameter (r ₀ ) of the purification stake such that the concentration of the contaminants in the contaminated ground becomes 1/10 of the initial concentration within 5 years When the influence range was calculated, it was confirmed that the influence range was 2.5 times the pile diameter. Therefore, the interval between adjacent purification piles is preferably 5 times or less the pile diameter, and within this range, the interval between purification piles is appropriately determined according to the period for completing purification, the initial concentration of contaminated ground, and the like. It is necessary.

[0027]

(Equation 1)

[0028]

According to the groundwater purifying structure and the groundwater purifying method of the present invention, the purifying effect can be generated at an early stage in the contaminated ground with low sewage permeability, and the construction cost can be reduced over a wide range. Of contaminated groundwater can be treated in situ.

[Brief description of the drawings]

FIG. 1 is a diagram showing a groundwater purification structure of the present invention;
(A) is a plan view, (b) is a side sectional view.

FIG. 2 is a plan view illustrating the operation of the groundwater purification structure of the present invention.

FIG. 3 is a graph showing a change with time of a pollutant concentration in a monitoring hole when the groundwater purification structure of the present invention is used.

FIG. 4 is a plan view showing a conventional permeable groundwater purification wall method.

[Explanation of symbols]

 G Contaminated ground 10 Groundwater purification structure 11 (11A-11I) Purification pile 12 Monitoring hole

Continuing from the front page (72) Inventor Naoki Shinohara 1-25-1, Nishishinjuku, Shinjuku-ku, Tokyo Taisei Construction Co., Ltd. (72) Inventor Kazuhiro Ikegami 1-1-25-1, Nishishinjuku, Shinjuku-ku, Tokyo Taisei Construction Shares F term in the company (reference) 4D024 AA01 AB11 AB16 BA02 BA03 BA06 BA07 BA18 BB01 DB22 4D050 AA02 AB19 BA02 BD03 CA06

Claims (4)

[Claims] 1. A fixed number of purification piles installed at a predetermined position in a whole area of a contaminated ground where groundwater flow does not occur, wherein the purification pile is a decomposition material, a stabilizing material, or an adsorption material for pollutants. A groundwater purification structure comprising: 2. The underground water purification structure according to claim 1, wherein an interval between the adjacent purification piles is 5 times or less a pile diameter. 3. A monitoring hole is formed at a predetermined position on the contaminated ground.
2. The groundwater purification structure according to 1. 4. A predetermined number of purification piles containing a decomposing material, a stabilizing material, or an adsorbing material for contaminants are cast at a predetermined position in the entire area of the contaminated ground where no groundwater flow is generated, so that the original position can be obtained. 2. A method for purifying groundwater, comprising purifying groundwater.