JP5839252B2 - Contaminated groundwater purification structure - Google Patents

Description

  The present invention relates to a purification structure for soil or groundwater contaminated with volatile organic compounds or heavy metals.

  Conventionally, a method using a permeable reaction wall is known as a method for purifying soil or groundwater contaminated with a volatile organic compound such as trichlorethylene or heavy metal in situ. The permeable reaction wall is a structure that is permeable to water and has the ability to react (insolubilize, decompose, etc.) with contaminants in groundwater.

  FIG. 3 is a side sectional view showing a conventional purification method using a permeable reaction wall. In this purification method, the permeable reaction wall 30 is installed from the unsaturated zone 31 to the aquifer (saturated zone) 32 so as to reach the impermeable layer 33 made of clay or rock. At this time, the permeable reaction wall 30 is erected so as to be substantially orthogonal to the flow direction of the groundwater 36 flowing through the aquifer (saturation zone) 32. Thereby, the groundwater 36 containing the pollutant 35 diffused from the pollutant source 34 permeates the permeable reaction wall 30, and at the time of the permeation, the pollutant 35 reacts with the permeable reaction wall 30 to be rendered harmless or removed. The

  As a technique related to such a purification method, for example, Patent Document 1 embeds a plurality of protective pillars close to a certain contaminated area in which underground soil is contaminated so as to surround the contaminated area. A pollution diffusion prevention and purification method is disclosed. The protective column has a structure in which a tubular body provided with a large number of through holes is filled with charcoal as a filtering material, and filters out contaminants flowing out of the contaminated area together with groundwater and the like. Further, Patent Document 2 discloses a pollution diffusion prevention in which a pollution diffusion preventing wall having water permeability and carrying a rare earth compound is buried in the ground so as to partition contaminated soil and non-contaminated soil. A structure is disclosed.

JP 2000-117237 A International Publication No. 03/103866

  By the way, in the purification method using the permeable reaction wall 30 as described above, the thickness of the permeable reaction wall 30 is determined according to the concentration of the pollutant 35, the flow velocity of the groundwater 36, etc. The permeable reaction wall 30 is installed by excavating deeply to 33. Moreover, since the permeable reaction wall 30 once installed deteriorates or breaks down with passage of the groundwater 36 containing the pollutant 35 continuously, the permeable reaction wall 30 is maintained in order to maintain the purification action. It is desirable to replace 30 regularly. However, since the permeable reaction wall 30 is installed deep in the ground as described above, the exchange of the permeable reaction wall 30 is very difficult and requires a lot of cost.

  This invention is made | formed in view of the above, Comprising: It aims at providing the purification structure of the contaminated groundwater which can replace | exchange a permeable reaction wall easily.

  In order to solve the above problems, a contaminated groundwater purification structure according to the present invention is a purification structure that purifies contaminated groundwater in situ, and guides groundwater flowing deep in the aquifer to the shallow part of the aquifer. A flow path forming member that forms a flow path, and the ground water surface that is installed in the vicinity of the ground water surface and that is guided to a shallow portion by the flow path forming member, thereby reacting with a contaminant contained in the ground water, and A permeable reaction wall for purifying groundwater is provided.

  In the contaminated groundwater purification structure, the flow path forming member includes a first wall member installed in a region from the ground surface to a height higher than a bottom of the groundwater, and the first wall member downstream of the first wall member. A second wall member installed in a region separated by a predetermined distance from the wall member of 1 and from a bottom of the groundwater to a height lower than the groundwater surface, the permeable reaction wall, It is provided in at least an upper region of the second wall member.

  In the contaminated groundwater purification structure, the first wall member is a steel sheet pile placed from the ground surface to the depth, and the second wall member is on an impermeable layer that is a bottom of the ground water. It is an underground wall installed.

  The contaminated groundwater purification structure is characterized in that the permeable reaction wall is installed such that a main surface of the permeable reaction wall is substantially horizontal.

  In the contaminated groundwater purification structure, the permeable reaction wall is disposed on the upstream side or the downstream side of the first permeable reaction wall material having the ability to insolubilize heavy metals and the first permeable reaction wall material. And a second permeable reaction wall material having the ability to decompose volatile organic compounds.

  According to the present invention, since the water flow that guides the deep groundwater to the shallow part is formed by the flow path forming member, the permeable reaction wall can be disposed in the vicinity of the groundwater surface. Therefore, when the permeable reaction wall deteriorates, it can be easily replaced with a new permeable reaction wall.

FIG. 1 is a side sectional view showing a contaminated groundwater purification structure according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA of FIG. FIG. 3 is a side sectional view showing a conventional method for purifying contaminated groundwater.

  Embodiments of a contaminated groundwater purification structure according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment.

  FIG. 1 is a side sectional view showing a contaminated groundwater purification structure (hereinafter simply referred to as “purification structure”) according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA in FIG. A purification structure 10 shown in FIGS. 1 and 2 is a purification structure that purifies groundwater 6 flowing in an aquifer (saturation zone) 2 existing between the unsaturated zone 1 and the impermeable layer 3 in its original position. The purification structure 10 is installed on the downstream side of the pollution source 4 that diffuses the pollutant 5 including volatile organic compounds and heavy metals.

  The purification structure 10 includes a steel sheet pile 11, an underground wall 12, and a horizontal permeable reaction wall 13. Of these, the steel sheet pile 11 and the underground wall 12 constitute a flow path forming member that forms a flow path for guiding the groundwater 6 flowing in the deep part of the aquifer 2 to the shallow part of the aquifer 2.

  The steel sheet pile 11 is located on the upstream side of the horizontal permeable reaction wall 13 that is a purification point of contaminated groundwater, and is higher than the bottom of the groundwater 6 (that is, the surface of the impermeable layer 3) from the ground surface 1a (that is, the ground surface 1a). From the groundwater surface 2a to the depth D, and the flow of the groundwater 6 is shielded. Preferably, the main surface of the steel sheet pile 11 is installed so as to be substantially orthogonal to the flow direction of the groundwater 6.

  The underground wall 12 is a region on the downstream side of the steel sheet pile 11 and is installed in a region separated from the steel sheet pile 11 by a predetermined distance. The underground wall 12 is a wall member installed in a region from the bottom of the groundwater 6 to a height H lower than the groundwater surface 2a. By shielding the flow of the groundwater 6 that has passed below the steel sheet pile 11, the underground water The flow direction of 6 is changed upward along itself. The underground wall 12 is installed on the impermeable layer 3 by, for example, a ground improvement pile installation method such as a cement-based deep mixing (CDM) method. Preferably, the main surface of the underground wall 12 is also installed so as to be substantially orthogonal to the flow direction of the groundwater 6 (that is, substantially parallel to the main surface of the steel sheet pile 11).

  The horizontal permeable reaction wall 13 is a structure having a property of allowing water to permeate and a property of reacting (insolubilizing, decomposing, etc.) with a predetermined contaminant. The horizontal permeable reaction wall 13 is installed in the vicinity of the groundwater surface 2a, and purifies the groundwater 6 by transmitting the groundwater 6 guided to the shallow portion by the steel sheet pile 11 and the underground wall 12. In the present embodiment, the horizontal permeable reaction wall 13 is placed such that one end is placed on the underground wall 12 and its upper surface exceeds the groundwater surface 2a. As a result, the groundwater 6 flowing into the region between the groundwater surface 2 a and the underground wall 12 is reliably introduced into the horizontal permeable reaction wall 13. Preferably, the horizontal permeable reaction wall 13 is installed so that its main surface is substantially horizontal.

  In the present embodiment, the horizontal permeable reaction wall 13 includes a first permeable reaction wall material (hereinafter referred to as a first reaction wall material) 13a having a capability of reacting with a heavy metal such as lead, mercury, and arsenic to insolubilize it. And a second permeable reaction wall material (hereinafter referred to as second reaction wall material) 13b having the ability to react with volatile organic compounds such as trichlorethylene and decompose. The first reaction wall material 13 a and the second reaction wall material 13 b are arranged in order from the upstream side to the downstream side along the flow direction of the groundwater 6. 1 and 2, the first reaction wall member 13a is arranged on the upstream side and the second reaction wall member 13b is arranged on the downstream side, but the arrangement order may be reversed.

Next, the operation of the purification structure 10 will be described.
As shown in FIG. 1, when the steel sheet pile 11 is installed so that the bottom surface is lower than the top surface of the underground wall 12, between the steel sheet pile 11 and the underground wall 12, the deep part of the aquifer 2 is shallow. A flow of the groundwater 6 rising toward is formed. Here, in the deep part of the aquifer 2, there is a high-concentration pollutant 5 called a polluted plume, and this polluted plume also flows into the flow of groundwater 6 formed by the steel sheet pile 11 and the underground wall 12. Take it to the shallow area. The groundwater 6 containing the pollutant 5 passes through the horizontal permeable reaction wall 13 installed in the vicinity of the groundwater surface 2a. At that time, the pollutant 5 passes through the first reaction wall material 13a and the second reaction wall material 13b in sequence and is detoxified or removed.

  As described above, according to the present embodiment, by providing the steel sheet pile and the underground wall, a water flow that leads the deep underground water to the shallow portion is formed, so purification by the permeable reaction wall is performed in the vicinity of the underground water surface. be able to. Therefore, when the permeable reaction wall deteriorates, it can be easily replaced with a new permeable reaction wall. In particular, when the permeable reaction wall is arranged substantially horizontally as in the present embodiment, since the amount of excavation in the depth direction is small, the exchange of the permeable reaction wall is further facilitated. Moreover, the change of the thickness of the permeable reaction wall according to the concentration of the pollutant (the length in the direction along the flow direction of the groundwater) can be easily performed. Alternatively, when the rate of deterioration of the permeable reaction wall is non-uniform for each part, it is also possible to partially exchange the permeable reaction wall according to the deterioration state.

  Moreover, according to this Embodiment, since a high concentration contaminated plume is guided and purified to the shallow part of groundwater, it becomes possible to improve purification efficiency.

  Furthermore, according to the present embodiment, two kinds of permeable reaction walls having different performance are arranged side by side, and the groundwater is sequentially permeated, so that both heavy metals, which are pollutants, and volatile organic compounds are simultaneously purified. Is possible. Further, when the deterioration rates of the two types of permeable reaction walls are different, only one of them can be exchanged as necessary.

  In the present embodiment described above, by providing the steel sheet pile and the underground wall, a water flow that leads the deep underground water to the shallow portion is formed. However, if such a water flow can be formed, the steel sheet pile and the ground It is not limited to the configuration using the inner wall.

  In the above embodiment, the horizontal type permeable reaction wall is constituted by two types of permeable reaction walls. However, only one of them may be used depending on the type of contaminants. This kind of permeable reaction wall may be further added.

  Furthermore, in the above embodiment, as shown in FIG. 1, the horizontal permeable reaction wall 13 is supported by placing one end of the horizontal permeable reaction wall 13 on the underground wall 12. Further, a support column or the like that supports the horizontal permeable reaction wall 13 may be separately installed in the impermeable layer 3. In this case, if the groundwater 6 that has passed through the upper part of the underground wall 12 is reliably introduced into the horizontal permeable reaction wall 13, one end of the horizontal permeable reaction wall 13 is not necessarily placed on the underground wall 12. There is no need. For example, the arrangement of the members may be determined so that the lower end portion of the left end surface of the horizontal permeable reaction wall 13 and the upper end portion of the right end surface of the underground wall 12 abut.

  The contaminated groundwater purification structure according to the present invention is useful when purifying contaminated groundwater in situ, and is particularly useful when purifying groundwater in which a contaminated plume exists deep.

1, 31 Unsaturated zone 1a Ground surface 2a Groundwater surface 2, 32 Aquifer (saturated zone)
3, 33 Impervious layer 4, 34 Pollution source 5, 35 Pollutant 7, 37 Groundwater 10 Purification structure 11 Steel sheet pile 12 Underground wall 13 Horizontal permeable reaction wall 13a First permeable reaction wall material (first reaction wall material) )
13b Second permeable reaction wall material (second reaction wall material)
30 Permeable reaction wall 32a Groundwater level

Claims (4)

It is a purification structure that purifies contaminated groundwater flowing through the aquifer, which is a saturated zone that exists between the unsaturated zone and the impermeable layer ,
A flow path forming member for forming a flow path for guiding the ground water flowing deep of the aquifer to the shallow portion of the belt-water layer,
A permeable reaction wall that is installed in the vicinity of the groundwater surface and permeates the groundwater guided to the shallow portion by the flow path forming member, thereby purifying the groundwater by reacting with contaminants contained in the groundwater;
With
The flow path forming member includes a first wall member installed in a region from the ground surface to a height higher than the surface of the impermeable layer, which is the bottom of the aquifer, and downstream from the first wall member. A region separated by a predetermined distance, comprising a second wall member installed in a region from the surface of the impermeable layer which is the bottom of the aquifer to a height lower than the groundwater surface,
The bottom surface of the first wall member is installed to be lower than the top surface of the second wall member,
The permeable reactive walls, Ri horizontally disposed horizontal permeable reactive wall der, washed structure contaminated groundwater, wherein Rukoto provided at least above the region of the second wall member. The first wall member is a steel sheet pile driven from the ground surface to the height ,
2. The contaminated groundwater purification structure according to claim 1 , wherein the second wall member is an underground wall installed on an impermeable layer which is a bottom of the aquifer . The contaminated groundwater purification structure according to claim 1 or 2 , wherein the permeable reaction wall is installed such that a main surface of the permeable reaction wall is substantially horizontal. The permeable reaction wall is
A first permeable reaction wall material having the ability to insolubilize heavy metals;
A second permeable reaction wall material disposed on the upstream side or the downstream side of the first permeable reaction wall material and having the ability to decompose volatile organic compounds;
The structure for purifying contaminated groundwater according to any one of claims 1 to 3 , wherein:

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