JP2003112175A - Groundwater purification wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a groundwater purification wall which can treat polluted groundwater covering a wide range while reducing the cost. SOLUTION: This groundwater purification wall 1 comprises a permeable groundwater purification wall 1a which is formed by arranging a wall-like region 11 containing a permeable purifying material under the ground and a water stop wall (a pair of water stop walls 1b) which collects groundwater (polluted groundwater 3) not concerned with the permeable groundwater purification wall 1a to convert it into groundwater (polluted groundwater 3) concerned with the permeable groundwater purification wall 1a.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to groundwater purification technology using civil engineering and sanitary engineering, and more particularly to groundwater contaminated with organic chlorine compounds, heavy metals and the like. (Hereinafter referred to as “contaminated groundwater”). [0002] Conventional groundwater purification walls of this type include:
For example, as shown in FIG. 8, when the flow of the contaminated groundwater 102 generated from the contaminated source 101 has a permeable layer formed in the direction indicated by the black arrow in the drawing, the flow is formed by trench excavation in a direction in which the flow of the contaminated groundwater 102 is blocked. Slot 1
03 is filled with iron powder 104 as a metal reducing agent as a permeable purifying material. According to this type of groundwater purifying wall, when the contaminated groundwater 102 passes through the groundwater purifying wall made of iron powder 104, a detoxification treatment is performed by a reduction reaction. Contaminated groundwater 102 having
Can be a purified groundwater 105 having a flow in the direction of the white arrow in the figure. [0004] However, such a groundwater purifying wall has the following inconvenience in relation to groundwater purifying performance and cost. First, as shown in FIGS. 8 and 9 (FIG. 9 (a) is a longitudinal sectional view and FIG. 9 (b) is an enlarged view), a permeable purifying material constituting this groundwater purifying wall is used. Since it is composed only of the iron powder 104, the iron powder 10
As a result, the calcium salt precipitates in the pores, and as a result, the clogging occurs and the water permeability gradually decreases.
2 turns in the direction of the arrow 106, and the purification power is lost. Second, as shown in FIG. 10, when the contaminated groundwater 102 is contaminated with a specific heavy metal M, it is retained on the surface of the iron powder 104 when passing through the groundwater purification wall. The specific heavy metal M (FIG. 10 (a))
When the reducing ability of the iron powder 104 is lost, it is ionized and eluted again (FIG. 10B). [0007] Third, when the contaminated groundwater 102 is spread over a wide area, all the slots 103 excavated over a wide area are filled with iron powder 104 and the contaminated groundwater 102 is treated without leakage. The cost becomes enormous, and practical use becomes difficult. Accordingly, an object of the present invention is to provide a groundwater purification wall capable of treating a wide range of contaminated groundwater while reducing costs. [0009] In order to achieve the above object, a groundwater purifying wall according to the present invention has a permeable structure in which a wall-like region including a permeable purifying material is arranged in the ground. It is characterized by comprising a groundwater purifying wall and a water stop wall which collects groundwater not related to the permeable groundwater purifying wall and serves as groundwater for the permeable groundwater purifying wall. The present invention relates to a permeable groundwater purifying wall having a wall-like region including a permeable purifying material disposed in the ground, and a groundwater purifying wall comprising a water blocking wall for collecting groundwater to the permeable groundwater purifying wall. By doing so, even when the contaminated groundwater is spread over a wide area, it is possible to treat such contaminated groundwater while reducing the cost. [0011] In such technical means, the permeable purifying material is a chemical (for example, a reduction reaction) or a chemical reaction (for example, a reduction reaction) when the whole or a part of a wall-shaped high region through which contaminated groundwater permeates is formed in the ground. It refers to a particulate material, a powder material, or any other material that exerts a physical (eg, adsorption) action and purifies contaminated groundwater that permeates the wall-shaped region. Therefore, in order to make it a permeable purifying material, it is necessary to have water permeability enough to allow contaminated groundwater to permeate when all or part of the wall-shaped region is formed in the ground. Therefore, as such a permeable purifying material, for example, a material composed of only a purifying material such as a metal reducing agent such as iron powder, an adsorbing substance such as activated carbon particles, or a chelating resin particle, A material obtained by mixing a material having no purification action such as a fine aggregate with a material having no purification action can be used. That is, the permeable purifying material of the third invention is not limited to the permeable purifying materials of the first and second inventions. The wall-like region containing the permeable purifying material is
It refers to a wall-shaped region that is purified by permeating contaminated groundwater. The wall-shaped region including the permeable purifying material is formed by a portion made of the permeable purifying material and, in some cases, a surrounding ground portion. For example, a hole (trench) formed by excavating a trench may be filled with the permeable purifying material, and a column made of a permeable purifying material may be arranged in a row. You can also. However, from the viewpoint of minimizing material separation inevitably occurring when arranging underground and securing the permeability of contaminated groundwater, the wall-shaped regions are arranged in line in the ground. It is preferable to include a group of columns made of a permeable purifying material. In the column group, the columns may be disposed in close contact with each other or may be disposed intermittently. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. Embodiment 1 FIG. 1 is a perspective view schematically showing a groundwater purifying wall according to Embodiment 1 of the present invention, FIG. 2 is a plan sectional view schematically showing the groundwater purifying wall, and FIG. It is a figure which shows the outline of the permeable purification | cleaning material of a purification wall (FIG. 3 (a) is a longitudinal cross-sectional view, FIG.3 (b) is an enlarged view). In the first embodiment, as shown in FIG. 1, the groundwater purifying wall 1 is provided on the downstream side of the flow of the groundwater from the place where the groundwater is contaminated with the organic chlorine compound at the pollution source 2 existing on the site of the factory. The permeable groundwater purification wall 1a is located at the center, and a pair of water stop walls 1b are installed on both sides of the permeable groundwater purification wall 1a. The groundwater purifying wall 1 is for purifying the contaminated groundwater 3 which is sequentially generated from the contaminant source 2 and thereby purifying the contaminated groundwater 3 into purified groundwater 4. As shown in FIG. 2, the permeable groundwater purifying wall 1a has a wall-like region 11 containing a permeable purifying material disposed underground, and the wall-like region 11 containing the permeable purifying material is A column group 11a in which the columns are arranged in a row in the ground, including a column made of the permeable purifying material 21 (see FIG. 3). In the first embodiment, the column group 11a made of the permeable purifying material 21 is configured to be intermittently arranged in rows. The reason why the row arrangement of the column group 11a is intermittent is that the purifying power by the reduction reaction substantially extends not only to the cross-sectional area but also to the outer area of each of the cylinders constituting the column group 11a. This is because As shown in FIG. 3, the permeable purifying material 21, which is a construction material of the column group 11a, is a mixture of iron powder 21a as a metal reducing agent and silica sand 21b. Here, the mixing amount of the iron powder 21a was set to 20% by weight. The reason for using a mixture of iron powder 21a and silica sand 21b instead of only the iron powder as the permeable purifying material 21 is that the permeability of the permeable purifying material 21 is sufficiently secured to reduce the iron content. Even if the corrosion of the powder 21a occurs, the calcium salt is prevented from settling in the gap, and the life of the groundwater purification wall 1 is extended. Further, the present invention aims at an economic effect of greatly reducing the total usage of the expensive iron powder 21a. Therefore, if the same object can be achieved, fine aggregate having water permeability equivalent to the silica sand 21b may be used instead of the silica sand 21b. In the first embodiment, since the column group 11a made of the permeable purifying material 21 is arranged in the ground as the wall-shaped region 11 containing the permeable purifying material, Maintenance of permeability over a long period of time can be more completely and easily achieved. In other words, since it is possible to adopt a construction method of forming a cylinder by arranging a permeable purifying punch in a drilled hole while preventing collapse of the ground using a casing pipe, permeability which is generally inevitable Material separation of the purifying material 21 can be considerably suppressed, whereby the permeation performance of the contaminated groundwater is sufficiently ensured. Here, the performance of the permeable purifying material 21 was examined by conducting an experiment using the laboratory apparatus shown in FIG. 4A, and the result (graph) shown in FIG. 4B was obtained. . In FIG. 4A, reference numeral 41 denotes a raw water tank (φ150 × 290 mm) containing contaminated water contaminated with an organochlorine compound, and reference numeral 42 denotes purified water purified in this experiment. Purified water tank to be stored, reference numeral 43
Is a Teflon (registered trademark) tube (φ) for feeding contaminated water or purified water from the raw water tank 41 to the treated water tank 42.
Reference numeral 44 denotes a low flow rate liquid transfer pump (0.2 to 20 ml / min) for providing the Teflon tube 43 with a power to feed contaminated water or purified water. Reference numeral 45 denotes an iron powder 21a and silica sand 21b mixed therein (the mixing amount of the iron powder 21a is 20 by weight ratio).
%) And a glass column (φ4) containing a permeable purifying material 45 a having the same configuration as the permeable purifying material 21.
0 × 290 mm), reference numeral 46 is an inlet sampling unit which is a point for collecting contaminated water on the upstream side of the glass column 45, and reference numeral 47 is an outlet sampling unit which is a point for collecting purified water on the downstream side of the glass column 45. It is. In this experiment, the concentration of organochlorine compounds in the contaminated water was 1
ppm and the flow rate of the contaminated water passing through the glass column 45 was set to 30 cm / day. According to FIG. 4B, it is understood that the concentration of the organic chlorine compound at the outlet of the column contained in the purified water collected by the outlet sampling unit 47 is substantially zero regardless of the number of days elapsed. Therefore, the permeable purifying material 45 used in this experiment was used.
It has been confirmed that the permeable purifying material 21 having the same configuration as a can be made into purified groundwater 4 containing no organic chlorine compound by permeating the contaminated groundwater 3 contaminated at an organic chlorine compound concentration of 1 ppm. On the other hand, as shown in FIG. 2, a pair of water stop walls 1b have their base ends connected to both ends of the wall-shaped region 11 of the permeable groundwater purifying wall 1a, and their tip ends have left and right sides. It is a planar arrangement extending diagonally forward. That is, according to the pair of water blocking walls 1b, groundwater that is not related to the permeable groundwater purification wall can be collected and used as groundwater for the permeable groundwater purification wall 1a. The pair of water blocking walls 1b are arranged in the water permeable layer 31 where the flow of the groundwater exists. However, a predetermined burial length is secured also in the water impermeable layer 32, thereby securing the water stopping property. (Not shown). In the first embodiment, an underground continuous wall made of concrete and a core material is used as the pair of waterproof walls 1b. However, the present invention is not limited to this. It may be appropriately selected according to the situation. Therefore, as long as the water blocking property of the water blocking wall is ensured, for example, a sheet pile, a column-type steel pipe pile, an SMW, or the like can be used. Therefore, in the groundwater purifying wall 1 according to the first embodiment, the permeation is achieved by intermittently arranging the columns 11a of the permeable purifying material 21 composed of the iron powder 21a and the quartz sand 21b in the ground. As a groundwater purification wall,
Thus, it is possible to avoid clogging due to corrosion of a and precipitation of calcium salts. Therefore, desired water permeability can be maintained for a long time after the start of operation, and this contributes to extending the life of the permeable groundwater purification wall 1a. In addition, since a pair of water blocking walls 1b extend diagonally forward in the left and right directions from both ends of the permeable groundwater purifying wall 1a, respectively, when the contaminated groundwater 3 extends over a wide area. In addition, it is possible to treat such contaminated groundwater 3 while reducing the cost. Embodiment 2 FIG. 1 is a perspective view schematically showing a groundwater purifying wall according to Embodiment 2 of the present invention, FIG. 5 is a plan sectional view schematically showing the groundwater purifying wall, and FIG. FIG. 6 (a) is a longitudinal sectional view, and FIG. 6 (b) is an enlarged view showing the outline of the permeable purifying material of the purifying wall. Note that components similar to those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted. As shown in FIGS. 1 and 5, the basic configuration of the groundwater purifying wall 51 according to the second embodiment is substantially the same as that of the first embodiment. Instead, a permeable groundwater purifying wall 51a having a configuration different from this is applied, and is different from the first embodiment in that the pollution source 2 is contaminated with a specific heavy metal M. As shown in FIG. 5, the permeable groundwater purifying wall 51a has a wall-like region 61 including a permeable purifying material disposed underground, and the wall-like region 61 including the permeable purifying material.
Is formed by filling a slot 61a formed by excavating a trench with a permeable purifying material made of a chelating resin 71. In the second embodiment, as shown in FIG. 6, the chelating resin 71 as a permeable purifying material is used in the first embodiment.
Into a chelate resin particle having water permeability corresponding to the silica sand 21b according to the above. Thus, the same effect as in the first embodiment can be obtained also in the permeable purifying material according to the second embodiment. In the permeable groundwater purifying wall 51a, the chelating resin 71 has the following function in groundwater since it has a chelating functional group having selective adsorption. That is, as shown in FIG.
When the contaminated groundwater 3 containing permeates through the permeable groundwater purification wall 51a, the specific heavy metal M is adsorbed on the surface of the chelate resin 71. At this time, the specific heavy metal M is selectively adsorbed by the chelate functional group of the chelate resin 71 and chemically ion-exchanged as shown in FIG. I can't. That is, according to the groundwater purifying wall 51 according to the second embodiment, substantially the same effects as those of the groundwater purifying wall 1 according to the first embodiment can be obtained, and the permeable groundwater purifying wall 51a is constituted. By utilizing the selective adsorption performance of the chelating resin 71, even when the contaminated groundwater 3 is contaminated with a specific heavy metal M, an effect that the specific heavy metal M can be prevented from re-eluting can be obtained. Was. In the second embodiment, as the permeable groundwater purifying wall 51a, the chelating resin 71 formed into a granular shape is used.
Only those consisting of, but not limited to this, as long as the adsorption power of the chelating resin is properly exhibited,
As in Embodiment 1, a mixture of a chelate resin formed into granules and a water-permeable material such as silica sand can be used. According to the permeable groundwater purifying wall according to the present invention, the groundwater purifying wall capable of treating a wide range of contaminated groundwater while reducing the cost is constructed as described above. It is possible to obtain.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view schematically showing a groundwater purifying wall according to Embodiments 1 and 2 of the present invention. FIG. 2 is a plan sectional view schematically showing a groundwater purification wall according to Embodiment 1 of the present invention. FIG. 3 is a view schematically showing a permeable purifying material of a groundwater purifying wall according to Embodiment 1 of the present invention (FIG. 3 (a) is a longitudinal sectional view, and FIG. 3 (b) is an enlarged view). FIG. 4 is a diagram schematically showing an indoor experimental device (FIG. 4 (a)) for confirming the performance of the permeable purifying material according to the first embodiment of the present invention and the results of the indoor experimental device (FIG. 4 (b)). . FIG. 5 is a plan sectional view schematically showing a groundwater purification wall according to Embodiment 2 of the present invention. FIG. 6 is a view schematically showing a permeable purifying material of a groundwater purifying wall according to Embodiment 2 of the present invention (FIG. 6 (a) is a longitudinal sectional view, and FIG. 6 (b) is an enlarged view). FIG. 7 is a conceptual diagram illustrating the performance of a permeable purifying material according to Embodiment 2 of the present invention. FIG. 8 is a plan sectional view schematically showing a conventional permeable groundwater purifying wall. FIG. 9 is a view schematically showing a conventional permeable purifying material (FIG. 9 (a) is a longitudinal sectional view, and FIG. 9 (b) is an enlarged view). FIG. 10 is a conceptual diagram illustrating the performance of a conventional permeable purifying material. [Description of Signs] 1 Groundwater purification wall 1a Permeable groundwater purification wall 1b Water blocking wall 2 Pollution source 3 Contaminated groundwater 4 Purified groundwater 11 Wall-shaped area 11a Column group 21 Permeable purification material 21a Iron powder 21a Pig powder 21b Silica sand 31 Water-permeable layer 32 impermeable layer 41 raw water tank 42 treated water tank 43 teflon tube 44 low flow rate liquid pump 45 glass column 45a permeable purifying material 46 inlet sampling unit 47 outlet sampling unit 51 groundwater purifying wall 51a permeable groundwater purifying wall 61 wall-shaped area 61a slot 71 chelating resin 101 pollution source 102 polluted groundwater 103 slot 104 iron powder 105 purified groundwater 106 arrow M heavy metal

Continuation of front page    (72) Inventor Satoshi Imamura             1-25-1, Nishi Shinjuku, Shinjuku-ku, Tokyo Taisei             Construction Co., Ltd. F term (reference) 4D024 AA10 AB11 AB16 BA02 BA18                       BB01 BC01 CA07 DB22                 4D050 AA02 AB19 AB52 BA02 BD01                       CA06

Claims (1)

Claims: 1. A permeable groundwater purifying wall having a wall-like region including a permeable purifying material disposed in the ground, and groundwater irrelevant to the permeable groundwater purifying wall is collected and collected. A water-blocking wall that serves as groundwater for the permeable groundwater purification wall, the base end of which is related to the end of the wall-shaped region of the permeable groundwater purification wall, and the tip end of which is extended obliquely forward. A groundwater purification wall, characterized in that: