JP2002001363A - 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, keeping desired permeability for a long period after the application and treating the contaminated groundwater over a wide area at the site with a reduced execution cost. SOLUTION: The groundwater cleaning structure 10 is provided with a wall like region (permeable cleaning wall 11) containing a cleaning material (iron powder 12a) and a water permeating material (silica sand 12b) and constructed in the underground and a water flow accelerating means (water pump 15) and is formed to enable to pass the contaminated groundwater through the wall like region.

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 Conventionally, methods for purifying groundwater include:
Groundwater purification wall construction methods are known. In this groundwater purifying wall method, as shown in FIG. 4, a groundwater purifying wall 11 'made of a water-permeable purifying material is constructed on the downstream side of the flow of the contaminated groundwater W' in the contaminated ground G '. This is a method of purifying contaminated groundwater W 'by purifying it through the purification wall 11'.

[0003]

However, this groundwater purification wall method is not suitable for groundwater purification performance and cost.
It has the following problems.

(1) The groundwater flow velocity of the contaminated ground G 'is 1 year
In the case of about m or less, the time required for the contaminated groundwater W 'to reach the groundwater purification wall 11' and pass therethrough is very long, and it takes a long time for the purification effect to appear.

(2) Even when the contaminated groundwater W 'has a predetermined flow velocity, if only the most common iron powder is used as a purification material constituting the groundwater purification wall 11', the time elapses. As a result, the iron powder itself corrodes, and calcium salts precipitate in the gaps. As a result, clogging occurs and the water permeability (water permeability) gradually decreases. Therefore, when the permeability of the groundwater purifying wall 11 'becomes smaller than the permeability of the target ground, the contaminated groundwater W' is removed from the groundwater purifying wall 1 '.
Since it flows bypassing 1 ', the purifying action does not occur.

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

The present invention has been made to solve the above-mentioned problems, and has a small groundwater flow rate (1 m / year).
In the contaminated ground, the purification effect can be generated at an early stage, the desired water permeability can be maintained for a long time after the start of operation, and the construction cost can be reduced over a wide range. It is an object of the present invention to provide a groundwater purification structure and a groundwater purification method that can treat in-situ contaminated groundwater.

[0008]

In order to solve the above problems, the present invention according to claim 1 is directed to a purifying material and a water permeable material (hereinafter, a mixture of both materials is referred to as a "water permeable purifying material").
Comprising a wall-shaped region constructed underground, a water flow generating means or a water flow accelerating means of the contaminated groundwater, and configured to allow the contaminated groundwater to flow through the wall-shaped region. The present invention provides a groundwater purification structure characterized in that:

Here, the purifying material refers to a material capable of purifying contaminated groundwater by exerting a chemical or physical action, such as a decomposing material, a stabilizing material or an adsorbing material for pollutants. . In addition, the water-permeable material refers to a material such as a fine aggregate having water permeability enough to transmit contaminated groundwater in the wall-shaped region. The mixing ratio of the purifying material and the water-permeable material is not particularly limited as long as the mixing ratio is such that the purifying action is not lost. Various materials having reactivity and durability can be used as the purification material, and can be appropriately selected according to the type of pollutants contained in the contaminated ground.

[0010] The decomposed material is a substance having a property of decomposing and detoxifying the contaminant by reacting with the contaminant. For example, when an organic chlorine compound is contained as a contaminant, a predetermined effect can be obtained by adding 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 particular, when a material obtained by mixing a metal reducing agent as a purifying material and a fine aggregate as a water permeable material is used as the water permeable purifying material, good water permeability is obtained, and corrosion of the metal reducing agent is reduced. It is possible to avoid clogging due to precipitation of calcium salts and calcium salts, and to maintain desired water permeability for a long period of time after the start of operation, which is very suitable for purifying contaminated water due to organic halogen compounds and heavy metals. is there.

Therefore, according to the present invention, since a water-permeable wall-shaped region and a groundwater flow generating means for forcibly generating a water flow in contaminated groundwater, or a waterflow accelerating means for contaminated groundwater, are provided. By forcibly generating or accelerating the water flow of the contaminated groundwater and passing the water through the wall-like area, the contaminated groundwater can be purified very quickly.

According to a second aspect of the present invention, in the groundwater purifying structure according to the first aspect, the wall-shaped region includes:
A predetermined number of purification piles intermittently arranged in a row in the ground are included, and the purification pile includes a purification material and a water-permeable material.

Here, the purification pile refers to a pile body containing a purification material such as a decomposition material, a stabilization material or an adsorption material for pollutants, and a water-permeable material such as fine aggregate as constituent materials.

Therefore, according to the present invention, the water-permeable purification material is disposed in the ground by forming the wall-shaped region to include a predetermined number of purification piles intermittently arranged in the ground. In addition to minimizing the number of purification piles and minimizing the number of purification piles, the maximum purification effect can be obtained with minimum construction cost.

According to a third aspect of the present invention, in the groundwater purifying structure according to the first or second aspect, a water-guiding member having a water-blocking property for guiding the contaminated groundwater to the wall-shaped region. It is characterized by having.

Therefore, according to the present invention, the provision of the water guide member having the water blocking property makes it possible to collect the contaminated groundwater in the wall-shaped region, and thus the contaminated groundwater can be efficiently collected at the site. Purification can be performed, and the construction cost can be reduced.

Further, according to a fourth aspect of the present invention, a wall-shaped region containing a purification material and a water-permeable material, and a water-stopping water-guiding member for guiding contaminated groundwater to the wall-shaped region are provided underground. In addition to the construction, the contaminated groundwater is provided with a water flow generation means or a contaminated groundwater water flow acceleration means, and the contaminated groundwater is forcibly flowed and purified by passing the contaminated groundwater through the wall region. It is intended to provide a groundwater purification method characterized by the above.

[0019]

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. The target ground is a wide ground having a pollution source, such as in a factory premises, and is a ground where a slight flow of groundwater occurs.

As shown in FIG. 1, a groundwater purifying structure 10 of the present invention comprises a permeable purifying wall 11 provided on the contaminated ground G on the downstream side of the groundwater flow, and a permeable purifying wall 11.
Pair of water blocking walls 14 (water blocking member) installed on both sides of
And a pump 15 (groundwater flow acceleration means) inserted into a pumping well 16 on the downstream side of the permeable purification wall 11.

The permeable purification wall 11 includes a predetermined number of purification piles 12.
Is formed from a wall-shaped region having a fixed width and a fixed length. The purification pile 12 is a columnar pile intermittently arranged in a zigzag pattern in a wall-shaped region, and uses iron powder 12a as a purification material and silica sand 12b as a water-permeable material. . Here, the reason that not only the iron powder 12a but also the silica sand 12b was mixed is that the corrosion of the iron powder 12a occurs even if the water permeability of the purification pile 12 is sufficiently ensured.
Calcium salt is prevented from settling in the gap, the life of the groundwater purifying structure 10 is extended, and the iron powder 1
The purpose is to achieve an economic effect of greatly reducing the total use amount of 2a. Therefore, if the same object can be achieved, fine aggregate having water permeability equivalent to the silica sand 12b may be used instead of the silica sand 12b.

Further, the purification pile 12 is cast over the entire wall-shaped region 11 so that the interval between the purification piles 12 adjacent on the left and right is a predetermined distance. The purification pile 12
Can be appropriately selected according to the condition of the contaminated ground G, such as a staggered one instead of a staggered one.

Further, the purifying pile 12 is formed in a column shape by arranging a water-permeable purifying material in a hole drilled while preventing collapse of the ground using a casing pipe (not shown). Therefore, material separation in the water-permeable purification material, which is usually inevitable, can be significantly suppressed. Therefore, the water permeability of the contaminated groundwater is sufficiently ensured, and the maintenance of water permeability over a long period of time can be more completely and easily achieved.

As shown in FIG. 1, a pair of water stop walls 14
Each base end is connected to both ends of the permeable purification wall 11, and each of the front ends extends obliquely forward and left (in the upstream direction of the flow of contaminated groundwater) in plan view. . Here, the width of the tip must be equal to or greater than the maximum width d of the contaminated groundwater flow W (contaminated groundwater flow). By constructing the water blocking wall 14 in this manner, it is possible to collect and purify the contaminated groundwater flowing at the maximum width d by collecting the water at the portion of the permeable purification wall 11 located at the center. . This pair of water blocking walls 14 is constructed in the permeable layer 21 where the contaminated groundwater flow W is generated,
A predetermined burial length is ensured in 2 to thereby ensure the waterproofness.

In the present embodiment, it is assumed that the pair of waterproof walls 14 is constructed of an underground continuous wall made of concrete and a core material. However, the present invention is not limited to this. Selection may be made appropriately according to the service period and the like. Therefore, as long as the water blocking property of the water blocking wall 14 is ensured, for example, a sheet pile, a column-type steel pipe pile, an SMW, or the like can be used.

The pump 15 is inserted into a pumping well 16 provided at a position reaching a predetermined depth in the permeable layer 21 where the contaminated groundwater flow W exists. By pumping groundwater to the ground using the pump 15, the contaminated groundwater flow W can be forcibly accelerated.

(Operation) The operation of the underground water purification structure 10 of the present invention will be described. When the pump 15 provided on the downstream side of the permeable purification wall 11 is operated to continuously pump the groundwater, the flow of the groundwater from the pollution source to the pumping well 16 is accelerated. Therefore, the contaminated groundwater flow W passes through the permeable purification wall 11 in an accelerated state, and the iron powder 12a and the pollutant B
The contaminant B is removed from the contaminated groundwater by the reduction reaction. Therefore, even in the contaminated ground G where the groundwater flow is small, the contaminated groundwater can be purified in situ. In addition, even in contaminated ground where the ground has water permeability, but there is no hydrodynamic gradient, and groundwater flow does not occur, pumping is performed using a water pump (groundwater flow generation means) to secure the hydraulic gradient and forcefully By generating the flow rate of the contaminated groundwater, the contaminated groundwater can be quickly purified.

Further, since a pair of water blocking walls 14 are provided to extend diagonally forward in the left and right directions from each of the two ends of the permeable purification wall 11, the case where the contaminated groundwater flows with the maximum width d. Also, it becomes possible to collect and purify the contaminated groundwater at the portion of the permeable purification wall 11 located at the center. Therefore, since it is not necessary to install the permeable purification wall 11 over the entire width of the contaminated groundwater flow W, the contaminated groundwater can be purified while reducing the construction cost.

According to the present invention, the purification pile 12 is
Since it is configured as a column group including a water-permeable purification material composed of a and silica sand 12b, clogging due to corrosion of iron powder 12a and precipitation of calcium salt can be avoided. Therefore, it is possible to maintain desired water permeability for a long time after the start of operation, thereby contributing to extending the life of the permeable purification wall 11.

The preferred embodiment of the present invention has been described above. 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 purifying material, various materials can be used depending on the type of the pollutant. For example, in addition to the above materials, chelate resin particles may be used. This chelate resin is obtained by molding a chelate resin into particles so as to have water permeability, and has a chelate functional group having selective adsorption performance for a specific heavy metal, so that contaminated groundwater is contaminated with a specific heavy metal. Even in such a case, an excellent effect that a situation in which the specific heavy metal is re-eluted can be avoided is obtained.

Also, the number, diameter, pile length, etc. of the purification piles can be appropriately selected, and purification piles having different pile diameters may be cast. Further, a plurality of purification piles in which the ratio and type of the water-permeable purification material are appropriately changed may be cast. Further, the water stopping member is not limited to the water stopping wall, and the positional relationship between the wall region and the water stopping member is not particularly limited as long as the structure can effectively collect water at the wall region. Absent. Further, the groundwater flow generating means and the groundwater flow accelerating means are not limited to the pump, and may be provided in plural.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to confirm the effect of the underground water purification structure 10 of the present invention, results of an earth tank experiment shown in FIG. 2 will be described below. The experimental device is 1.5m long and 0.5m wide
Was used as the pollution area G ′ in the range of 0.5 m on the upstream side, and the permeable purification wall 11 ′ was formed in the range of 0.8 m to 0.9 m from the upstream side. This permeable purification wall 11 ′ is made up of a purification stake 12 ′ (formed from iron powder and quartz sand) having a pile diameter of 5 cm, intermittently arranged in two rows over a total width of 9 cm.
This book was arranged. Further, a pump 1 is provided outside the earth tank 20 '.
5 ′ was provided, water was sucked from the downstream side of the earth tank 20 and supplied to the upstream side, thereby forcibly generating a water flow.
FIG. 3 shows a temporal change in the concentration of pollutants in groundwater at the center A of the polluted area G ′. Here, the horizontal axis indicates the number of days elapsed (days) and the concentration of pollutants, the thick line indicates the case where the pump 15 ′ was operated to accelerate the flow rate of the groundwater, and the thin line indicates that the pump 15 ′ was not operated. Each case is shown. In this experiment, hexavalent chromium, which has poor adsorptivity to soil, was used as a contaminant.

According to the results, the time required to reach the concentration of the pollutant, which is the purification target, is about half the time when the pump 15 'is operated and the time when the pump is not operated. The effect of shortening the time to achieve was confirmed.

It should be noted that the period required to meet the purification target depends on the flow rate of groundwater (the amount of pumped water). However, in the case of hexavalent chromium or the like in which the adsorption of pollutants to the soil is negligible, the permeability of the permeable purification wall 11 'is reduced. It was found that doubling the flow velocity can reduce the time required to achieve purification to about half. As described above, the present invention is a method particularly effective for hexavalent chromium and arsenic, which are poor in adsorptivity to soil, among heavy metals that rapidly react with the purification pile 12 ′.

[0036]

According to the groundwater purifying structure and the groundwater purifying method of the present invention, the purifying effect can be quickly generated in the contaminated ground with low water permeability by forcibly generating or accelerating the flow velocity of the groundwater. And a groundwater purification structure capable of maintaining desired water permeability for a long period of time after the start of operation, and capable of treating a wide range of contaminated groundwater in situ while reducing construction costs. It becomes possible to provide a groundwater purification method.
Therefore, it is possible to adopt a maintenance-free purification method even on contaminated ground with low water permeability.

[Brief description of the drawings]

1A is a plan view showing a groundwater purification structure of the present invention, FIG. 1B is a side sectional view of the same, and FIG. 1C is an enlarged plan view of a purification pile.

FIG. 2 is an explanatory diagram of a test device for confirming the effect of the groundwater purification structure of the present invention.

FIG. 3 is a graph showing the change over time in the concentration of pollutants present in groundwater located downstream of a water-permeable purification wall when the groundwater purification structure of the present invention is used.

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

[Explanation of symbols]

 G Contaminated ground W Contaminated groundwater flow 10 Groundwater purification structure 11 Permeable purification wall (wall-like area) 12 Purification pile 12a Iron powder (purification material) 12b Silica sand (permeable material) 14 Waterproof wall (waterproof member) 15 Pumping pump ( Groundwater flow acceleration means) 16 Pumping well

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 1/28 C02F 1/28 F E02D 5/18 101 E02D 5/18 101 5/20 101 5/20 101 F-term (reference) 2D049 EA01 EA15 GB01 GB05 GC11 4D024 AA00 AB11 AB16 AB17 BA02 BA03 BA04 BA06 BA07 BA18 BB01 BC01 CA02 4D050 AA20 AB19 AB52 AB54 AB59 BA02 BD02 4G066 AA02B AB24B AE17B BA12 CA33 CA46 CA50 DA07

Claims (4)

[Claims] An underground constructed wall-like region including a purification material and a water-permeable material, and a contaminated groundwater water flow generation means or a contaminated groundwater water flow acceleration means, wherein the contaminated groundwater is contained in the wall-like region. A groundwater purification structure characterized by being configured to allow water to pass through. 2. The wall-shaped region includes a predetermined number of purification piles intermittently arranged in a row in the ground, wherein the purification pile includes a purification material and a water-permeable material. Item 2. The groundwater purification structure according to Item 1. 3. The groundwater purification structure according to claim 1, further comprising a water guide member having a water blocking property for guiding the contaminated groundwater to the wall-shaped region. 4. A wall-shaped region including a purification material and a water-permeable material, and a water-guiding member having a water-stopping property for guiding contaminated groundwater to the wall-shaped region, are constructed underground, and a water flow of the contaminated groundwater is generated. Means for purifying the contaminated groundwater by forcibly flowing the contaminated groundwater and passing the contaminated groundwater through the wall region.