JP2007061799A - METHOD FOR pH ADJUSTMENT OF GROUND WATER - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for pH adjustment of ground water capable of preventing the elution of a harmful substance and a bad influence on a surrounding environment and capable of making the ground water dischargeable directly into a sewer system, by making the ground water flow through the soil and/or an underground zone for treating the ground water to adjust the pH of the acidified or alkalized ground water to the adequate value on the spot. <P>SOLUTION: The method for adjusting the pH of the ground water flowing through the soil and/or the underground zone 10 for treating the ground water comprises a permeable pH adjustment wall 5 built at the downstream side of the underground zone 10, allowing the ground water flowing down through the underground zone 10 to pass through the pH adjustment wall 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for adjusting the pH of groundwater, and in particular, by adjusting the pH of groundwater that has flowed through the soil and / or groundwater treatment section to an appropriate pH in situ, elution of harmful substances and the surrounding environment can be achieved. The present invention relates to a method for adjusting the pH of groundwater to prevent adverse effects.

  Groundwater flowing in the ground becomes alkaline or acidified due to various causes. For example, groundwater becomes alkaline or acidified in the following cases.

(1) When ground improvement work is performed in which cement or slaked lime is added to the soil.
Generally, in ground improvement work that improves soil strength, compressibility, water permeability, etc., inexpensive cement, quicklime, slaked lime, etc. are added and kneaded to the soil (Soil Stabilization Handbook, Matsuo) Shinichiro, Nikkan Kogyo Shimbun, p 175, 215). In this case, when rainwater or the like penetrates into the improved soil, or when groundwater penetrates into the improved soil, the groundwater may become alkaline.

(2) When the soil is treated with an alkaline treatment agent or an acidic treatment agent in order to insolubilize the second type specified harmful substance in the soil.
Explanation of technical methods of investigation and measures based on the Soil Contamination Countermeasures Act as a method for insolubilizing soil contaminated with the Class II Specified Hazardous Substances of the Soil Contamination Countermeasures Act (published and supervised by the first edition in September 2003) , Edition / issue: Soil Environment Center), various chemicals for insolubilization of these harmful substances are exemplified, but soil treated with these alkaline or acidic treatment agents is treated Depending on the soil, the soil becomes alkaline or acidified. Then, when rainwater or groundwater permeates into the alkalinized or acidified soil, the groundwater may be alkalized or acidified.

(3) When a purification wall is installed with a chemical that decomposes and adsorbs specific harmful substances of the Soil Contamination Countermeasures Law dissolved in groundwater and removes it from groundwater.
Japanese Patent No. 3329456 discloses that polluted groundwater is removed by passing through a purification wall constructed with a chemical that decomposes and adsorbs specific harmful substances dissolved in groundwater and removes them from groundwater. However, the pH of groundwater that has passed through such a purification wall may vary depending on the type of chemical used.
Japanese Patent No. 3329456

  However, such changes in the pH of groundwater may affect the use of groundwater as drinking water, the use of groundwater as irrigation water, agricultural land, etc. Since it may cause elution of two types of harmful substances, it is not preferable.

  Moreover, when flowing groundwater into a sewer etc., the pH needs to be the range of 5-9.

  Therefore, the present invention adjusts the pH of groundwater whose pH has been alkalinized or acidified by flowing through the soil and / or groundwater treatment section as described above to an appropriate pH at the original position. An object of the present invention is to provide a method for adjusting the pH of groundwater in order to prevent elution and adverse effects on the surrounding environment, and to allow discharge to sewers.

  The pH adjustment method for groundwater according to the present invention (Claim 1) is a method for adjusting the pH of groundwater that has flowed through a treatment section of soil and / or groundwater, and has a water-permeable pH adjustment wall downstream of the treatment section. And groundwater flowing down from the treatment section is allowed to pass through the pH adjusting wall.

  The groundwater pH adjusting method according to claim 2 is characterized in that, in claim 1, the pH adjusting wall is formed of a solid pH adjusting agent, or the pH adjusting agent and a water-permeable material.

  The pH adjustment method for groundwater according to claim 3 is the method according to claim 2, wherein the pH adjuster is selected from the group consisting of acid clay, activated clay, diatomite, humus soil, volcanic ash soil, and weakly acidic ion exchange resin. Or it is characterized by being 2 or more types.

  The groundwater pH adjusting method according to claim 4 is the method according to claim 2, wherein the pH adjusting agent is selected from the group consisting of iron powder, limestone, magnesium oxide, magnesium hydroxide, magnesium carbonate, and an anion exchange resin. Or it is characterized by being 2 or more types.

  The groundwater pH adjusting method according to claim 5 is characterized in that, in any one of claims 1 to 4, the treatment section is a soil region subjected to ground improvement work.

  The pH adjustment method for groundwater according to claim 6 is characterized in that, in any one of claims 1 to 4, the treatment section is a contaminated groundwater purification wall.

  The pH adjustment method for groundwater according to claim 7 is the in-situ containment method according to claim 6, wherein when the groundwater level inside the impermeable wall and the inside of the impermeable wall rises, the groundwater inside the impermeable wall is Providing a groundwater outflow part that flows out of the water wall and a purification wall for contaminated groundwater, and providing the pH adjusting wall downstream of the contaminated groundwater purification wall and upstream of the groundwater outflow part. Features.

  The groundwater pH adjusting method according to claim 8 is characterized in that, in claim 7, the groundwater outflow portion is a sewer.

  According to the pH adjustment method of groundwater of the present invention, the groundwater whose pH is alkalized or acidified by flowing through the soil and / or groundwater treatment section is passed through a water-permeable pH adjustment wall provided on the downstream side thereof. Thus, it can be easily adjusted to an appropriate pH at the original position. For this reason, the problem of elution of harmful substances in the soil due to the groundwater whose pH has changed and the adverse effect on the surrounding environment can be solved, and the outflow to the sewer can be performed without any problems.

  Hereinafter, embodiments of the pH adjustment method for groundwater of the present invention will be described in detail with reference to the drawings.

  1 and 2 are schematic views showing an embodiment of the pH adjustment method for groundwater according to the present invention, wherein (a) is a plan view and (b) is a BB line in (a). It is sectional drawing which follows.

  As shown in FIGS. 1 and 2, the impermeable layer 3 or the hardly permeable layer exists at a predetermined depth from the ground surface 1, and the aquifer 2 exists above the impermeable layer 3. 4 is the groundwater level.

  Since the ground improvement area 10, the ground improvement area, or the contaminated area 10A exists in the aquifer 2 on the impermeable layer 3, the ground improvement area 10, the ground improvement area, or the contaminated area 10A downstream of the groundwater flow direction W. The pH adjusting wall 5 or the contaminated groundwater purification wall 6 and the pH adjusting wall 5 are provided, and a sheet pile made of a steel plate or the like in a blade shape from both ends of the pH adjusting wall 5 or the contaminated groundwater purification wall 6 and the pH adjusting wall 5 is provided. 7 and 7 are provided to ensure that the groundwater from the upstream side passes through the pH adjusting wall 5 or the contaminated groundwater purification wall 6 and the pH adjusting wall 5.

  In FIG. 1, groundwater that has been alkalized or acidified by passing through a ground improvement region 10 where soil treated with an alkaline substance such as cement or slaked lime or a hazardous substance insolubilizing agent is present by ground improvement work. PH is adjusted by passing through the pH adjusting wall 5. In FIG. 2, the groundwater that has passed through the ground improvement area or the contaminated area 10 </ b> A where soil contaminated with the pollutant exists is purified through the contaminated groundwater purification wall 6 and passes through the contaminated groundwater purification wall 6. As a result, the pH of the groundwater that has been alkalized or acidified with the chemical in the purification wall 6 is adjusted by passing through the pH adjusting wall 5.

  The pH adjusting wall 5 has a plurality of boring holes formed in a continuous line in the ground to form a recess, and the pH adjusting agent or the pH adjusting agent and water permeation are formed in the recess or in a hole (trench) formed in the ground. By introducing a mixture with a functional material, a water-permeable layer can be provided and formed. The pH adjusting wall may have a laminated structure in which a pH adjusting agent and a water permeable material are provided in layers.

  The pH adjusting agent is appropriately selected depending on the pH and properties of the groundwater to be adjusted for pH, and for adjusting the pH of alkaline groundwater exceeding pH 8.7, acidic white clay, activated white clay, diatomaceous earth, humus soil, volcanic ash soil, and weak soil One or more selected from the group consisting of acidic ion exchange resins can be used. If it is these pH adjusters, alkaline groundwater can be neutralized by reaction with the hydrogen ion exchange part contained in a pH adjuster. Moreover, in order to adjust the pH of acidic groundwater having a pH of less than 5.7, one or more selected from the group consisting of iron powder, limestone, magnesium oxide, magnesium hydroxide, magnesium carbonate, and an anion exchange resin are used. Can be used. If it is these pH adjusters, acidic groundwater can be neutralized by reaction with the acid consumption part of a pH adjuster.

  As a water-permeable material that can be used in combination with these pH adjusters, sand, crushed stone, etc. having a relatively large particle diameter can be used. When using a water-permeable material, the use ratio or mixing ratio of the pH adjuster and the water-permeable material is appropriately determined in consideration of the flow rate of groundwater and the like.

  On the other hand, the contaminated groundwater purification wall 6 is formed with a continuous row of boreholes in the ground to form a recess, and this recess or a hole (trench) formed in the ground is used for groundwater purification. By introducing a treatment agent, that is, a treatment agent capable of decomposing or adsorbing harmful substances in groundwater, or a mixture of this treatment agent and a water-permeable material, a water-permeable layer can be provided. This contaminated groundwater purification wall may also have a laminated structure in which a purification agent and a water-permeable material are provided in layers.

  The purification agent for forming the purification wall 6 is appropriately selected according to the groundwater contamination status, for example, iron powder, activated carbon, hydrotalcite, rare earth compound, magnesium oxide, alumina, allophane, ion exchange resin, One or more selected from the group consisting of chelate resins and clay minerals can be used.

  As a water-permeable material that can be used in combination with these purification agents, sand, crushed stone, etc. having a relatively large particle diameter can be used. When using a water-permeable material, the use ratio or mixing ratio of the purification agent and the water-permeable material is appropriately determined in consideration of the flow rate of groundwater and the like.

  In FIG. 2, the pH adjustment wall 5 is provided adjacent to the purification wall 6 on the downstream side of the contaminated groundwater purification wall 6 in the direction of the groundwater flow. However, the pH adjustment wall 5 and the purification wall 6 may be separated from each other. . However, these are preferably provided adjacent to each other as shown in the figure, so that the boring work can be performed in common. Thus, when the purification wall 6 and the pH adjustment wall 5 are provided adjacent to each other, water-permeable sand, crushed stone, or the like is provided between the purification wall 6 and the pH adjustment wall 5 so that the purification agent and the pH adjustment agent are provided. Although mutual flow may be prevented, each effect can be exhibited without providing such a fluid.

  As shown in FIGS. 1B and 2B, the pH adjusting wall 5 and the purification wall 6 reach the impermeable layer 3 or the hardly permeable layer, and the upper ends thereof from the groundwater level 4 as shown in FIGS. Is also provided so as to be positioned above.

  Moreover, the sheet pile 7 is also provided so that the lower end thereof reaches the impermeable layer 3 or the hardly permeable layer and the upper end thereof is located above the groundwater level 4, similarly to the pH adjusting wall 5 and the purification wall 6. However, the upper end of the sheet pile 7 may be located above the ground surface 1. Instead of the sheet pile, a water-impervious wall constructed by pouring concrete into the ground by making a large number of drilling holes in a continuous line may be provided.

  1 and 2 are examples of embodiments of the present invention, and the present invention is not limited to the illustrated method. For example, in FIGS. 1 and 2, a funnel & gate method in which a water shielding wall is formed by a sheet pile 7 is adopted. However, such a water shielding wall is omitted and the pH adjusting wall 5 or the purification wall 6 and the pH adjusting wall 5 are omitted. You may provide only.

  In the present invention, the groundwater to be treated is groundwater whose pH deviates from an appropriate pH by flowing through various soil and / or groundwater treatment sections, that is, the alkaline water whose pH exceeds 8.7 or whose pH is over 8.7. Examples include acidic groundwater of less than 5.7. In particular, the present invention provides groundwater that has been made alkaline by flowing through the improved soil subjected to the ground improvement work of (1) described above, or the purification of contaminated groundwater according to (3) of the ground improvement work described above or (3). By flowing through the wall, it is suitable for adjusting the pH of groundwater that has been alkalized or acidified by chemicals.

  As shown in FIGS. 1 and 2, the water-permeable pH adjusting wall that allows passage of groundwater whose pH has changed by flowing through the soil and / or groundwater treatment section is as follows. It is provided in a wall shape in the direction of interruption with respect to the flow.

  In addition, in this invention, it is preferable to adjust to pH 5-9, especially 5.7-8.7 by allowing process groundwater to pass through such a pH adjustment wall.

  The present invention is particularly suitable for adjusting the pH of groundwater whose pH has been changed by passing through the contaminated groundwater purification wall described in (3) above. In this case, in particular, a water shielding wall is provided so as to surround the contaminated area. In the in-situ containment method, a water shielding wall, a groundwater outflow part that causes the groundwater inside the water shielding wall to flow out to the outside of the water shielding wall when the groundwater level inside the water shielding wall rises, and a purification part for contaminated groundwater It is suitable for the case where groundwater flowing out from the groundwater outflow part is purified by the contaminated groundwater purification wall and then discharged to the outside. In this case, it is downstream of the contaminated groundwater purification wall. The pH adjustment wall according to the present invention is provided upstream of the groundwater outflow part, and after adjusting the pH of the groundwater purified by the contaminated groundwater purification wall with the pH adjusting agent, the groundwater outflow part can be discharged from the groundwater outflow part, Like . By doing in this way, it becomes possible to adjust the pH of the groundwater whose pH is alkalinized or acidified by the purification wall to a neutral region of pH 5 to 9, and to discharge the groundwater to the sewer.

  Hereinafter, an embodiment in which the present invention is applied to such an in-situ containment method will be described with reference to FIGS.

  3 is a cross-sectional perspective view showing an area to which the in-situ containment method according to the embodiment is applied, FIG. 4 is a plan view showing the underground structure in this area seen through the soil, and FIG. FIG. 5B is a cross-sectional view taken along the line Vb-Vb in FIG. 6, and FIG. 6 is a perspective view in the soil showing the water shielding wall, the purifying means, and the water collecting path provided in the soil. FIG.

  As shown in FIG. 5A, the impermeable layer 3 or the hardly permeable layer is present at a predetermined depth from the ground surface 1, and the aquifer 2 is present on the upper side thereof.

  Since the contaminated soil 8 exists in all or a part of the area, the contaminated soil 8 is isolated from the surrounding 8A by the water shielding wall 9 and contained. The impermeable wall 9 has a lower end that reaches the impermeable layer 3 or the hardly permeable layer, and an upper end that is located near the ground surface 1 higher than the groundwater level 4. The upper end of the impermeable wall 9 may reach the ground surface 1.

  The impermeable wall 9 surrounds the entire circumference of the contaminated soil 8. In this embodiment, the planar view shape is a rectangular frame shape, but is not limited thereto. The water-impervious wall 9 can be constructed by pouring concrete into the ground with a large number of drilling holes in a continuous row, but may also be formed by driving a water-impervious steel sheet pile.

  As shown in FIG. 6, this water-impervious wall 9 is provided with one or a plurality of (three in this embodiment) square groundwater outflow portions 11 made of low places recessed downward from the upper end. . The lower edge of the groundwater outflow portion 11 is higher than the groundwater level 4 by a predetermined height (for example, about 0 to 100 cm).

  A purification / pH adjusting unit 12 is provided on the inner side (contaminated soil 8 side) of the groundwater outflow unit 11. The purification / pH adjustment unit 12 includes the above-described purification agent layer 12a on the water collecting channel 14 side and the pH adjustment agent layer 12b on the groundwater outflow unit 11 side, and the groundwater is purified by the purification agent layer 12a. Thereafter, the pH is adjusted by the layer 12b of the pH adjusting agent so as to flow out to the outside of the water shielding wall 9.

  Plate members 13 made of steel sheet piles or the like are disposed on both sides and the lower portion of the purification / pH adjusting unit 12. A waterproof concrete wall may be provided instead of the plate material 13.

  The upper surface of the purification / pH adjusting unit 12 is preferably positioned higher than the lower edge of the groundwater outflow unit 11 by about 0 to 200 cm. In addition, the lower surface of the purification / pH adjusting unit 12 is preferably located 50 to 500 cm lower than the lower edge of the groundwater outflow unit 11. Although both side surfaces of the purification / pH adjustment unit 12 are flush with the side edge of the groundwater outflow unit 11, the purification / pH adjustment unit 12 may be provided wider than that.

  The purification / pH adjustment unit 12 is provided so as to contact the inner surface of the water-impervious wall 9. In this embodiment, a part of the purification / pH adjusting unit 12 enters the groundwater outflow unit 11.

  The plate 13 preferably extends from 0 to 500 cm above the upper surface of the purification / pH adjustment unit 12, and preferably extends from 0 to 500 cm below the lower surface of the purification / pH adjustment unit 12. Yes. The plate material 13 is in contact with the inner side surface of the impermeable wall 9. This abutting portion may be sealed if necessary.

  The plate material 13 covers both sides and the entire lower part of the purification / pH adjustment unit 12, and water is prevented from flowing into the purification / pH adjustment unit 12 from the side and out into the groundwater outflow unit 11 in a short circuit. ing.

  Inside the impermeable wall 9, a water collecting channel 14 is provided at a level parallel to the impermeable wall 9 and including the groundwater level 4. The water collecting channel 14 is made of a water permeable material such as sand or crushed stone. The water collecting channel 14 may be a perforated pipe.

  The water collecting channel 14 is disposed so as to be in contact with the end surface of the purification / pH adjusting unit 12 opposite to the groundwater outflow unit 11. The water collecting channel 14 is provided so as to continuously circulate along the inner side surface of the impermeable wall 9, but the middle may be partially interrupted. Further, the water collecting channel 14 may be provided in a comb-teeth shape over the entire contaminated area.

  Although not shown, the ground surface 1 may be covered with asphalt, concrete, a water shielding sheet, or the like to prevent underground penetration of rainwater.

  In the containment structure configured in this way, the groundwater level inside the impermeable wall 9 is usually equal to or lower than the lower edge of the groundwater outflow portion 11, so that groundwater flows from the contaminated area to the surrounding 8A. Will not leak.

  When the groundwater level inside the impermeable wall 9 rises for some reason such as rainfall, the groundwater flows into the purification / pH adjustment unit 12 via the water collecting channel 14 or directly, and the purification / pH adjustment unit 12 performs purification and pH. After being adjusted, it flows out from the groundwater outflow part 11 to the surrounding 8A. This effluent water is subjected to the removal of heavy metals or decomposition or adsorption removal processing of contaminants such as halogenated organic substances in the purification / pH adjustment unit 12, and then the pH is adjusted, and the surrounding 8A is not contaminated.

  When the pollutant is a volatile organic chlorine compound, covering the ground surface 1 with asphalt or the like prevents (oxygen) from diffusing into the ground and improves the purification efficiency of the compound. Moreover, when a pollutant is a heavy metal, you may make the water in the contaminated soil 8 and the contaminated soil 8 contact with air, and the purification process efficiency of heavy metal improves by this.

  FIG. 7 is a plan view of an area to which the in-situ containment method according to another embodiment is applied, FIG. 8 is an enlarged plan view of the vicinity of the groundwater outflow portion in this area, and FIG. 9 is along the line IX-IX in FIG. It is sectional drawing.

  In this embodiment, a drain pipe 20 having a groundwater inflow port disposed in the inner region is provided so as to communicate the inner region surrounded by the impermeable wall 9 and the outer region.

  As shown in FIG. 7, also in this embodiment, a rectangular frame-shaped impermeable wall 9 is constructed so as to surround four sides of the contaminated soil (contaminated area) 8. As described above, the impermeable wall 9 has a lower end that reaches the impermeable layer 3 or the hardly impermeable layer and an upper end that is located near the ground surface 1 higher than the groundwater level 4. The upper end may reach the ground surface 1. In this embodiment, the outflow part 11 which consists of the low place recessed downward from the upper end of this water-impervious wall 9 is not provided.

  In this embodiment, a water collection container 21 is installed in the vicinity of one corner of the inner area of the water shielding wall 9. In this embodiment, the water collecting container 21 is a bottomed cylindrical container, the bottom is positioned below the groundwater level 4, and the upper part is exposed to the ground surface 1. A lid 21 a is attached to the upper end of the water collection container 21. However, the upper portion of the water collecting container 21 may not be exposed on the ground surface 1.

  One end (groundwater inlet) of the drain pipe 20 is connected to the vicinity of the bottom of the water collecting container 21 which is lower than the groundwater level 4. The drain pipe 20 extends from the inner area of the impermeable wall 9 to the outer area of the impermeable wall 9 through the impermeable wall 9. The drain pipe 20 is disposed so as to have a downward slope from the inner region to the outer region of the impermeable wall 9.

  In this embodiment, the other end side (outflow port) of the drain pipe 20 is connected to a sewer (not shown) that flows in the outer region of the impermeable wall 9. In addition, when the sewer is arrange | positioned in the height which becomes higher than this drain pipe 20, you may connect the drain pipe 20 and a sewer via a pumping equipment (not shown).

  In the inner region of the impermeable wall 9, a purification / pH adjustment unit 12 </ b> A is installed adjacent to the water collection container 21. As shown in FIG. 8, the purification / pH adjustment unit 12A includes a water-permeable material such as sand and crushed stone, a purification agent that performs purification by removing or decomposing contaminants, a pH adjustment agent, and these water-permeabilities. And a container 24 that contains a functional material, a purification agent, and a pH adjuster.

  As illustrated, in this embodiment, the container 24 includes three plate members 24a and 24b made of steel sheet piles, etc., arranged in a substantially U shape so as to surround the three sides of the purification / pH adjusting unit 12A. , 24c. Seals are applied to the joints between the plate members 24a to 24c as necessary. Of the container 24, the side that is not blocked by the plate members 24 a to 24 c is an inflow portion 24 d of groundwater into the container 24. A treated groundwater outlet 24e is provided in the plate 24b that closes the inflow portion 24d and the opposite side. The outflow port 24 e communicates with the inside of the water collection container 21 through a pipe 25. In addition, you may construct the container 24 with a concrete wall instead of the said board | plate materials 24a-24c.

  Each of the plate members 24a to 24c of the container 24 extends from 0 to 500 cm above the groundwater level 4, and preferably extends from 0 to 500 cm below the groundwater level 4. The outlet 24e and the pipe 25 are disposed substantially horizontally at a level including the groundwater level 4.

  In this embodiment, the first water-permeable material layer 22a, the purifying agent layer 23a, and the second water-permeable material layer 22b are arranged in the container 24 in the direction from the inflow portion 24d to the outlet 24e. The pH adjusting agent layer 23b and the third water-permeable material layer 22c are formed in this order in multiple layers.

  Each of the layers 22a to 22c, 23a, and 23b is fully extended from one inner surface to the other inner surface of the plate members 24a and 24c facing each other, and from the inflow portion 24d to the inner surface of the opposite plate member 24b. Filled. Each of the layers 22a to 22c, 23a, and 23b has a lower surface that reaches 50 to 500 cm below the groundwater level 4 and an upper surface that preferably reaches 0 to 200 cm above the groundwater level 4.

  In this embodiment, the upper and lower surfaces of the layers 22a to 22c, 23a, and 23b and the upper and lower sides of the plate members 24a to 24c are positioned at substantially the same level, but the plate members 24a to 24c are The layers 22a to 22c, 23a, and 23b may extend below the lower surface, and the layers 22a to 22c, 23a, and 23b may extend above the upper surface.

  The purifying agent layer 23a and the pH adjusting agent layer 23b are formed of the purifying agent and the pH adjusting agent, respectively.

  The first to third water-permeable material layers 22a to 22c may be made of the same type of water-permeable material, or may be made of different types of water-permeable materials.

  In this embodiment, by surrounding the three sides of the purification / pH adjustment unit 12A with the plate materials 24a-24c, it is possible to prevent water from flowing into the purification / pH adjustment unit 12A and outflowing into the water collecting container 21 in a short circuit. ing. If necessary, a plate material may also be provided on the bottom and top surfaces of the purification / pH adjustment unit 12A to prevent water from flowing into the purification / pH adjustment unit 12A from the bottom and top surfaces of the purification / pH adjustment unit 12A. Good.

  In this embodiment, the water collecting channel 14 </ b> A is provided in a comb-like shape over the entire contaminated area inside the impermeable wall 9 at a level including the groundwater level 4. In this embodiment as well, the water collecting channel 14A is made of a water-permeable material such as sand or crushed stone, but may be constituted by a perforated pipe or the like.

  Specifically, in this embodiment, as shown in FIG. 7, as shown in FIG. 7, the main part of the trunk is crossed diagonally from the corner where the water collection container 21 is installed, in the rectangular contaminated area 8. A water channel 14a is extended. The proximal end side of the main water collecting channel 14a is disposed so as to be in contact with the end surface of the first water-permeable material layer 22a facing the inflow portion 24d of the purification / pH adjusting unit 12A.

  Branch water collecting channels 14b extend from a plurality of locations along the extending direction of the main water collecting channel 14a in parallel with the respective sides in the two orthogonal directions (vertical direction and horizontal direction in FIG. 7) of the water shielding wall 9. Yes. In this embodiment, six branch water collecting channels 14b extend from the main water collecting channel 14a in the horizontal direction and the vertical direction in FIG.

  Although not shown, in this embodiment as well, the ground surface 1 may be covered with asphalt, concrete, water shielding sheets or the like to prevent rainwater from penetrating underground.

  Even in the containment structure configured in this way, when the groundwater level 4 inside the impermeable wall 9 rises due to some reason such as rainfall, the groundwater flows into the purification / pH adjusting unit 12A via the water collecting channel 14A or directly. . At this time, groundwater flows into the container 24 from the water collecting channel 14A through the inflow portion 24d, and the first water-permeable material layer 22a, the purification agent layer 23a, the second water-permeable material layer 22b, By sequentially passing through the pH adjusting agent layer 23b and the third water-permeable material layer 22c, contaminants in the groundwater are removed or detoxified, and then the pH is adjusted.

  This groundwater is purified by the purification / pH adjusting unit 12A, and then flows out from the outlet 24e through the pipe 25, the water collection container 21 and the drain pipe 20 to the sewer flowing in the outer region of the impermeable wall 9. The effluent water is subjected to the decomposition or adsorption removal processing of the pollutant by the purification / pH adjustment unit 12A, and further adjusted to pH, and does not contaminate the sewer or adversely affect the surrounding environment.

  In this embodiment, since the water collecting channel 14A is disposed over substantially the entire contaminated area 8, groundwater can be collected evenly over substantially the entire contaminated area 8.

  In the above embodiment, the water collection container 21 (the inlet of the drain pipe 20) is arranged near the corner of the inner region of the water shielding wall 9, but the water collection container 21 (the inlet of the drain pipe 20). The arrangement of is not limited to this. Further, the arrangement of the water collecting channel in the inner region of the water shielding wall 9 is not limited to the above embodiments.

  Further, the purification / pH adjustment unit 12, 12A may have a laminated structure of a purification agent layer and a pH adjustment agent layer, a mixture layer of a purification agent and a water permeable material, a pH adjustment agent and a water permeable material. It may be a laminated structure with a mixture layer.

It is a schematic diagram which shows embodiment of the pH adjustment method of groundwater of this invention, Comprising: (a) A figure is a top view, (b) A figure is sectional drawing which follows the BB line of (a) figure. It is a schematic diagram which shows other embodiment of the pH adjustment method of the groundwater of this invention, Comprising: (a) A figure is a top view, (b) A figure is sectional drawing which follows the BB line of (a) figure. . It is a perspective view which shows the area | region where the pH adjustment method of the groundwater in the in-situ containment construction method which concerns on embodiment was applied. It is a top view which shows the underground structure of the area of FIG. (A) The figure is the Va-Va sectional view taken on the line of FIG. 3, (b) The figure is the Vb-Vb sectional view taken on the line of FIG. It is a perspective view which shows the water-impervious wall, purification | cleaning / pH adjustment part, and water collection channel of FIG. It is a top view of the area where the pH adjustment method of groundwater in the in-situ containment construction method concerning another embodiment was applied. It is an enlarged plan view near the groundwater outflow part of the area of FIG. It is sectional drawing which follows the IX-IX line of FIG.

Explanation of symbols

1 surface 2 aquifer 3 impermeable layer (or hardly permeable layer)
4 Groundwater level 5 pH adjustment wall 6 Contaminated groundwater purification wall 7 Sheet pile 8 Contaminated soil 9 Impermeable wall 10 Ground improvement area 10A Ground improvement area or contamination area 11 Groundwater outflow part 12, 12A Purification / pH adjustment part 12a, 23a Layer 12b, 23b Layer of pH adjusting agent 13 Plate material 14, 14A, 14B Water collecting channel 20 Drain pipe 21 Water collecting container 22a-22c Layer of water permeable material 24 Container 24d Inflow portion 24e Outlet

Claims (8)

  A method for adjusting the pH of groundwater flowing through a soil and / or groundwater treatment section, wherein a water-permeable pH adjustment wall is provided on the downstream side of the treatment section, and the groundwater flowing down from the treatment section is supplied to the pH adjustment wall. A method for adjusting the pH of groundwater, characterized in that it is passed through.   2. The method for adjusting the pH of groundwater according to claim 1, wherein the pH adjusting wall is formed of a solid pH adjusting agent or the pH adjusting agent and a water-permeable material.   In Claim 2, the said pH adjuster is 1 type, or 2 or more types chosen from the group which consists of acid clay, activated clay, diatomaceous earth, humus soil, volcanic ash soil, and weak acid ion exchange resin, It is characterized by the above-mentioned. How to adjust the pH of groundwater.   In Claim 2, the said pH adjuster is 1 type, or 2 or more types chosen from the group which consists of iron powder, limestone, magnesium oxide, magnesium hydroxide, magnesium carbonate, and an anion exchange resin, It is characterized by the above-mentioned. How to adjust the pH of groundwater.   The groundwater pH adjusting method according to any one of claims 1 to 4, wherein the treatment section is a soil region subjected to ground improvement work.   The groundwater pH adjusting method according to any one of claims 1 to 4, wherein the treatment section is a contaminated groundwater purification wall.   The in-situ containment method according to claim 6, wherein a water shielding wall and a ground water outflow portion that causes the ground water inside the water shielding wall to flow out of the water shielding wall when the ground water level inside the water shielding wall rises. A groundwater pH adjusting method comprising: providing a groundwater purification wall; and providing the pH adjusting wall downstream of the groundwater purification wall and upstream of the groundwater outflow portion.   8. The method for adjusting the pH of groundwater according to claim 7, wherein the groundwater outflow portion is a sewer.

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