JP2015217351A - Groundwater purification system and groundwater purification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To purify groundwater in a contamination range of the ground from a deep layer side to the vicinity of a ground surface even if the contamination range exists in a laminated ground such as an impermeable layer, in a groundwater purification system for purifying groundwater in the contamination range of the ground by passing water through the contamination range.SOLUTION: A groundwater purification system 10 for purifying groundwater in a contamination range A of the ground by passing water through the contamination range A comprises: an impermeable wall 12 that is constructed so as to surround an area to be purified including the contamination range A and extend from a ground surface to a depth deeper than a groundwater level W.L in an area on the outer peripheral side of the area to be purified; a water-impervious sheet 40 that covers the ground surface of the area to be purified; a pouring well 30 that extends from the ground surface of the area to be purified to a depth deeper than the contamination range A and pouring water in a range from the ground surface of the area to be purified to a depth deeper than the contamination range A; and a pumping well 20 that extends from the ground surface of the area to be purified to a depth deeper than the contamination range A, is set to a negative pressure in the inside thereof, and pumps up water from a depth deeper than the contamination range A.

Description

  The present invention relates to a groundwater purification system and a groundwater purification method for purifying groundwater in the contaminated area by passing water through the contaminated area of the ground.

  As a soil purification system (groundwater purification system that purifies the groundwater in the contaminated area) by purifying the contaminated area by passing water through the contaminated area where the soil contamination occurred, the contaminated area is surrounded by a shielding wall, and the ground surface of the contaminated area Is known that allows water to flow into a contaminated area in a state of being covered with an airtight sheet (see, for example, Patent Document 1). In the soil remediation system described in Patent Document 1, the water injection well is constructed deeper than the contamination range, the pumping well connected to the vacuum pump is constructed in the unsaturated region directly under the airtight sheet, and the water injection well is brought into the contamination range. While pouring water, suction from the unsaturated area just below the airtight sheet in the pumping well. As a result, the vicinity of the ground surface becomes negative pressure, and the groundwater is sucked by the negative pressure, so that water can be passed near the ground surface, and contamination near the ground surface can be purified.

JP 2007-38175 A

  In the soil purification system described in Patent Document 1, the contamination range exists in the permeable layer, and the contamination range is purified by passing water upward from the deep layer side to the shallow layer side of the permeable layer. However, there is a case where the contamination range exists in an alternating layer ground such as an impermeable layer or a hardly permeable layer. In this case, since the water flow is blocked by the impermeable layer or the hardly permeable layer, it is difficult to adopt this system. .

  The present invention has been made in view of the above circumstances, and in a groundwater purification system that purifies groundwater in the contaminated area by passing water through the contaminated area of the ground, the contaminated area exists in an alternating layer ground such as an impermeable layer. Even in such a case, it is an object to be able to purify groundwater in a contaminated range from the deep side to the vicinity of the ground surface.

  In order to solve the above problems, a groundwater purification system according to the present invention is a groundwater purification system that purifies groundwater in a contaminated area by passing water through the contaminated area of the ground, and includes a purification target region including the contaminated area. A water-impervious wall constructed so as to extend from the ground surface to a depth below the groundwater level in the outer peripheral region of the purification target region, an airtight layer covering the ground surface of the purification target region, and the purification target A water injection well that extends from the ground surface of the region to a depth deeper than the contamination range, and injects water in a range from the ground surface of the purification target region to a depth deeper than the contamination range, and extends from the ground surface of the purification target region to a depth deeper than the contamination range, And a pumping well for pumping water from deeper than the contamination range.

  In the groundwater purification system, the impermeable wall may be constructed so as to extend to a hardly permeable layer existing on a deeper side than the contamination range.

  The groundwater purification system may include a water injection system that injects water into the purification target area through the water injection well, and an air supply system that supplies air to the purification target area through the water injection well.

  The groundwater purification method according to the present invention is a groundwater purification method for purifying groundwater in the contaminated area by passing water through the contaminated area of the ground, and the purification is performed from the ground surface of the purification target area including the contaminated area. Surrounding the area of the outer periphery of the target area deeper than the groundwater level with a water-impervious wall and covering the ground surface of the purification target area with an airtight layer, the surface of the purification target area is deeper than the contamination range. By a water injection well extending to a depth from the ground surface of the purification target area to the depth of the contamination range and extending from the ground surface of the purification target area to the depth of the contamination range by a pumping well having a negative pressure inside. The water is pumped from deeper than the contamination range of the purification target area.

  The groundwater purification method according to the present invention is a groundwater purification method for purifying groundwater in the contaminated area by passing water through the contaminated area of the ground, and the purification is performed from the ground surface of the purification target area including the contaminated area. Surrounding the poorly permeable layer existing on the deeper side than the target region with a water-impervious wall and covering the ground surface of the purification target region with an airtight layer, the contamination range from the ground surface of the purification target region The purification by a pumping well that extends to a depth deeper than the contamination range of the purification target area by a pumping well with a negative pressure inside, and a water injection well that extends from the ground surface of the purification target area to a depth deeper than the contamination range. A water injection step of injecting water in a range from the ground surface of the target area to a depth deeper than the contamination range.

  In the groundwater purification method, in the pumping step, air may be supplied to the purification target region through the water injection well, and in the water injection step, air may be sucked from the purification target region through the pumping well.

  According to the present invention, in the groundwater purification system for purifying the groundwater in the contaminated area by passing water through the contaminated area of the ground, even when the contaminated area exists in the alternating layer ground such as an impermeable layer, from the deep layer side. It can purify groundwater in the contaminated area up to the ground surface.

It is an elevation sectional view showing the groundwater purification system concerning one embodiment. It is a top view which shows arrangement | positioning of the pumping well, pumping well, and water injection well of the groundwater purification system which concerns on one Embodiment. It is an elevation sectional view explaining the procedure of constructing the groundwater purification system concerning one embodiment. It is an elevation sectional view explaining the groundwater purification construction method concerning one embodiment. It is an elevational sectional view showing a groundwater purification system according to another embodiment. It is an elevation sectional view explaining the procedure which constructs the groundwater purification system concerning other embodiments. It is an elevational sectional view explaining a groundwater purification method according to another embodiment. It is an elevational sectional view explaining a groundwater purification method according to another embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a vertical sectional view showing a groundwater purification system 10 according to an embodiment, and FIG. 2 is an arrangement of pumping wells 20 (illustrated by black circles) and water injection wells 30 (illustrated by white circles) of the groundwater purification system 10. FIG. As shown in FIG. 1, a groundwater purification system 10 is a groundwater purification method (soil purification) that purifies a contaminated area A existing in a region surrounded by a water-impervious wall 12 (hereinafter referred to as a purification target region) by water washing. For the construction method). The ground to be purified by the groundwater purification system 10 is an alternate layer ground in which permeable layers and impermeable layers are alternately stacked. It is the ground that extends deeper than L. The groundwater level W. L is the groundwater level on both the inside and the outside of the purification target area before starting water washing, and is hereinafter referred to as a first groundwater level.

  The groundwater purification system 10 includes a water shielding wall 12 constructed so as to surround the purification target area, a plurality of pumping wells 20 and a plurality of water injection wells 30 provided in the purification target area, and a ground surface of the purification target area. A water-impervious sheet 40 laid, and a water injection facility 50, a vacuum suction facility 60, and a water treatment facility 61 installed on the ground are provided. The water-impervious wall 12 is a steel sheet pile wall or the like having a water-impervious wall, and is constructed so as to reach from the ground surface to a depth below the first groundwater level.

  The pumping well 20 is composed of gravity drainage and forced drainage such as vacuum deepwell (vacuum deepwell), superwellpoint (registered trademark), hyper deepwell (registered trademark), etc. (In this embodiment, a vacuum deep well is employed), and extends from the ground surface to the deepest part of the contamination range A. The pumping well 20 is filled between the casing 23 disposed in the hole 26, the submersible pump 22, the pumping pipe 25 and the suction pipe 28 disposed in the casing 23, and the casing 23 and the wall surface of the hole 26. The filter material 27 and a lid 29 for sealing the top end of the casing 23 are provided.

  A screen 24 is provided at the lower end of the casing 23, and a submersible pump 22 is installed in the screen 24. Further, one end of the pumping pipe 25 is connected to the submersible pump 22, and the other end of the pumping pipe 25 is connected to the header pipe 62. The header pipe 62 is connected to the water treatment facility 61.

  One end of the suction pipe 28 is inserted into the casing 23 through the lid 29, and the other end of the suction pipe 28 is connected to the header pipe 64. The header pipe 64 is connected to a vacuum pump (not shown) of the vacuum suction facility 60. Here, the suction pipes 28 of the plurality of pumping wells 20 are connected to a single vacuum pump via the header pipe 64.

  The water injection well 30 extends from the ground surface to a depth similar to that of the pumping well 20 (deeper than the deepest part of the contamination range A). The water injection well 30 includes a casing 33 disposed in the hole 36, a water injection pipe 35 disposed in the casing 33, a filter material 37 filled between the casing 33 and the wall surface of the hole 36, and the casing 33. And a lid 39 for hermetically sealing the top end. A screen 34 is provided at the lower end of the casing 33. One end of the water injection pipe 35 is inserted into the casing 33 through the lid 39, and the other end of the water injection pipe 35 is connected to the header pipe 52. The header pipe 52 is connected to a water injection pump (not shown) of the water injection facility 50. Here, the water injection pipes 35 of the plurality of water injection wells 30 are connected to a single water injection pump via the header pipe 52. Further, the water permeability coefficient of the filter material 37 is set larger than the water permeability coefficient of the soil in the purification target area. In the present embodiment, the filter material 37 is gravel.

  The water shielding sheet 40 is a sheet material having airtightness such as a water shielding sheet used in a waste disposal site, for example, and is provided so as to cover the entire ground surface of the region surrounded by the water shielding wall 12. Yes. Here, the water-impervious sheet 40 is formed with a hole through which the heads of the casings 23 and 33 are inserted, and between the heads of the casings 23 and 33 and the edge of the hole of the water-impervious sheet 40, It is sealed with a sealing material (not shown).

  As shown in FIG. 2, the pumping wells 20 are scattered in the purification target region with a predetermined regularity, and a plurality of water injection wells 30 are arranged so as to surround the pumping wells 20. In the present embodiment, the water injection wells 30 are arranged in a honeycomb shape (a shape in which regular hexagons are arranged without gaps), and the pumping well 20 is arranged in the center of a plurality of water injection wells 30 arranged in a regular hexagonal shape. ing. Here, the water injection wells 30 are scattered throughout the purification target region, and the interval between the water injection wells 30 and the interval between the water injection well 30 and the pumping well 20 are both set to a predetermined interval (for example, about 10 m). Is set.

  FIG. 1 and FIG. 3 are elevation sectional views for explaining a procedure for constructing a groundwater purification system 10 according to the present embodiment. First, as shown in FIG. 3, the impermeable wall 12 is constructed so as to reach a depth deeper than the first groundwater level from the ground surface. Next, as shown in FIG. 1, the pumping well 20 and the water injection well 30 are constructed in the ground inside the impermeable wall 12, and the impermeable sheet 40 is laid on the ground surface inside the impermeable wall 12. Moreover, the water injection equipment 50, the vacuum suction equipment 60, and the water treatment equipment 61 are installed on the ground.

  A hole is made in the water shielding sheet 40 for each position of the pumping well 20 and the water injection well 30, and when the water shielding sheet 40 is laid, the heads of the casings 23 and 33 are inserted into the holes, and the casing 23 , 33 and the edge of the hole of the water shielding sheet 40 are sealed with a sealing material. Moreover, the outer peripheral edge part of the water shielding sheet 40 is joined to the water shielding wall 12, and the space between them is sealed. Thereafter, the pumping pipes 25 of the plurality of pumping wells 20 are connected to the header pipe 62, and the suction pipes 28 of the plurality of pumping wells 20 are connected to the header pipe 64. Further, the water injection pipes 35 of the plurality of water injection wells 30 are connected to the header pipe 52.

  Further, in the step of constructing the pumped well 20, the hole 26 is excavated from the ground surface so as to reach the deepest part of the contamination range A, and the casing 23 is inserted into the hole 26. And the submersible pump 22 and the pumping pipe 25 are installed in the casing 23, and the filter material 27 is filled between the casing 23 and the hole wall of the hole 26. Further, the top end of the casing 23 is sealed with a lid 29 to which a pumping pipe 25 and a suction pipe 28 are attached.

  In the step of constructing the water injection well 30, the hole 36 is excavated from the ground surface so as to reach deeper than the deepest part of the contamination range A, and the casing 33 is inserted into the hole 36. The water injection pipe 35 is installed in the casing 33, and a filter material 37 is filled between the casing 33 and the hole wall of the hole 36. Further, the top end of the casing 33 is sealed with a lid 39 to which a water injection pipe 35 is attached.

  After constructing the groundwater purification system 10 as described above, water purification is performed on the purification target area as shown in FIG. In this water flow washing process, the vacuum pump of the vacuum suction facility 60 is operated to bring the pumping well 20 into a vacuum state, the submersible pump 22 is operated to pump up the groundwater in the purification target area, and the water injection facility 50 is operated. Then, water is injected from the water injection well 30 to the purification target area.

  Here, the water-impervious sheet 40 covers the ground surface of the purification target region in an airtight state, and the water-impervious wall 12 extends from the ground surface to a depth deeper than the first groundwater level. An airtight space surrounded by the water shielding wall 12 and the groundwater in the purification target area is formed. For this reason, when the vacuum suction by the pumping well 20 is started, the unsaturated layer near the ground surface in the purification target region becomes negative pressure. As a result, the groundwater in the purification target area is sucked up by the negative pressure of the unsaturated layer, and the groundwater flows from the outside to the inside of the purification target area below the impermeable wall 12, whereby the groundwater level in the purification target area is changed. It rises to near the ground surface.

  On the other hand, when water is supplied from the water injection facility 50 into the water injection well 30, the water is injected from the screen 34 at the lower end through the filter material 37 into the ground. Here, the negative pressure is generated in the unsaturated layer in the vicinity of the ground surface in the purification target range, and the water permeability coefficient of the filter material 37 is larger than the water permeability coefficient of the ground. The water sent to the water reaches the top end from the lower end of the filter material 37. Thereby, water injection is performed in the range from the lower end to the top end of the water injection well 30 in the purification target region.

  That is, between the pumping well 20 and the water injection well 30, a lateral water flow from the water injection well 30 to the pumping well 20 is formed in the range from the lower end to the vicinity of the ground surface. As a result, it is possible to carry out water washing in a wide area from the deepest part of the contaminated area A to the vicinity of the ground surface in the alternate layer ground where the permeable layer and the impermeable layer are alternately overlapped. It can be purified.

  FIG. 5 is an elevational sectional view showing a groundwater purification system 100 according to another embodiment. As shown in this figure, the ground for purifying groundwater and soil by the groundwater purification system 100 is an alternating layer of alternately permeable and impermeable layers, and the contamination range A is from the vicinity of the ground surface. It is the ground that extends deeper than the first groundwater level. Further, the hardly water-permeable layer 101 exists deeper than the deepest part of the contamination range A in the ground.

  The groundwater purification system 100 includes a water blocking wall 112 instead of the water blocking wall 12 of the above-described embodiment, and includes an air supply water well 130 instead of the water injection well 30 of the above-described embodiment. The groundwater purification system 100 includes an asphalt layer 140 instead of the water shielding sheet 40 of the above-described embodiment. The impermeable wall 112 extends from the ground surface to the poorly permeable layer 101 and surrounds the purification target region.

  One end of the water injection pipe 35 is inserted into the casing 33 through the lid 39, and the other end of the water injection pipe 35 is connected to the water injection equipment 50 via the header pipe 52. Here, the branch pipe 172 branches from the vicinity of the other end of the water injection pipe 35 of the plurality of air supply water injection wells 130. An opening / closing valve 174 is provided at the tip of the branch pipe 172. The inside of the air supply / water injection well 130 is opened to the atmosphere with the opening / closing valve opened, and the inside of the air supply / water injection well 130 with the opening / closing valve closed. Becomes airtight. Then, the vacuum suction facility 60 is operated with the open / close valve 174 open, and the purification target region becomes negative pressure, so that air is sucked in through the branch pipe 172 and the water injection pipe 35 and the water injection equipment in the state where the open / close valve 174 is closed. By operating 50, water is supplied from the water injection facility 50 to the water injection pipe 35.

  Here, the interval between the pumping well 20 and the air supply water well 130 is wider than that in the above embodiment, and the number of the pumping well 20 and the air supply water well 130 per unit area is as described above. It is less than the embodiment.

  FIG. 5 and FIG. 6 are elevation sectional views for explaining the procedure for constructing the groundwater purification system 10 according to the present embodiment. First, as shown in FIG. 6, the impermeable wall 112 is constructed so as to reach the hardly permeable layer 101 from the ground surface. Next, as shown in FIG. 5, the pumping well 20 and the air supply water well 130 are constructed in the ground inside the impermeable wall 112, and the asphalt layer 140 is laid on the ground surface inside the impermeable wall 112.

  The asphalt layer 140 is laid so that the heads of the casings 23 and 33 protrude from the ground surface, and the periphery of the heads of the casings 23 and 33 is sealed with asphalt. Moreover, the outer peripheral edge part of the asphalt layer 140 and the water-impervious wall 112 are integrated, and the space between them is sealed. Thereafter, the pumping pipes 25 of the plurality of pumping wells 20 are connected to the header pipe 62, and the intake pipes 28 of the plurality of pumping wells 20 are connected to the header pipe 64. Further, the water injection pipes 35 of the plurality of air supply water injection wells 130 are connected to the header pipe 52.

  After the groundwater purification system 100 is constructed as described above, the groundwater in the purification target area is purified. In this groundwater purification step, first, as shown in FIG. 7, the vacuum pump of the vacuum suction facility 60 is operated to bring the pumping well 20 into a vacuum state, and the submersible pump 22 is operated to pump up the groundwater in the purification target area. At the same time, the on-off valve 174 is opened, and air is supplied from the air supply water well 130 to the purification target region. At this time, since the impermeable wall 112 extends to the hardly permeable layer 101, the groundwater in the purification target region is pumped from the pumping well 20 in a state where the groundwater does not flow from the outer peripheral side to the inner peripheral side of the purification target region. . Thereby, the groundwater level W. of the purification target area inside the impermeable wall 112. L decreases.

  Here, the asphalt layer 140 covers the ground surface of the purification target region so as to be in an airtight state, so that the outside air is not sucked by the suction force of the pumping well 20, and the suction force of the pumping well 20 is reduced. Everything acts in the area to be purified. In addition, in the range from the ground surface to the contamination range A or deeper, a lateral air flow from the supply water injection well 130 to the pumping well 20 forms a lateral flow of groundwater in the purification target area to the pumping well 20. Directional flow is promoted. As a result, a deeper position can be obtained in a shorter period of time than when the ground surface of the purification target region is in a state where air can be ventilated or only suction is performed from the purification target region without supplying air to the purification target region. Up to groundwater level W. L can be reduced.

  Next, as shown in FIG. 8, after lowering the groundwater level to a depth deeper than the contamination range A (removing pore water in the contamination range A), the water injection facility 50 is operated with the on-off valve 174 closed to supply water. Water is injected from the air injection well 130 to the purification target area, and the vacuum pump of the vacuum suction facility 60 is operated to suck air from the pumping well 20.

  When water is supplied from the water injection facility 50 into the air supply water well 130, water is injected into the ground through the filter material 37 from the screen 34 at the lower end. Here, when the water permeability coefficient of the filter material 37 is larger than the water permeability coefficient of the soil in the purification target region, the water sent from the screen 34 to the filter material 37 spreads from the lower end of the filter material 37 to the top end. Thereby, water injection is performed in the range from the lower end of the air supply water injection well 130 to the top end in the purification target region. That is, between the pumping well 20 and the air supply water well 130, a lateral water flow from the air supply water well 130 to the pumping well 20 is formed in the range from the lower end to the vicinity of the ground surface. . Therefore, regardless of the presence of the impermeable layer, water is injected over the entire area from the contamination range A to the ground surface in the purification target region.

  Here, in a state where an airtight space surrounded by the asphalt layer 140, the impermeable wall 112, and the poorly permeable layer 101 is formed, air is sucked from the pumping well 20, so that the space becomes negative pressure. Become. Thereby, since the water flow from the air supply water injection well 130 to the pumping well 20 is promoted, the water injection time can be shortened.

  By repeating the pumping process and the water injection process described above, the contamination in the purification target area is diluted. Here, the pumping process and the water injection process are performed separately, and in the pumping process, the contaminated pore water is suctioned by vacuum, so that the contaminated pore water is compared with the water flow cleaning in which the pumping and the water injection are performed simultaneously. Can be removed efficiently, and the time required to purify the groundwater can be shortened.

  In addition, the above-mentioned embodiment is for making an understanding of this invention easy, and does not limit this invention. It goes without saying that the present invention can be changed and improved without departing from the gist thereof, and that the present invention includes equivalents thereof. For example, in the above-described embodiment, the case where the purification target region is an alternating layer ground where an alternate layer such as an impermeable layer exists is taken as an example, but not limited to this, water is injected from the deep side of the purification target region and the vicinity of the ground surface The present invention can also be applied to ground that is unsuitable for pumping water from the ground, or ground that is effective for passing water in the lateral direction (for example, ground that spreads a poorly permeable layer over a wide area).

  In the above-described embodiment, the water injection well and the air supply water well have the same configuration as the vacuum deep well, but these may have the same configuration as various drains such as a well point, a paper drain, and a sand drain. . Furthermore, in the above-described embodiment, the airtight layer covering the ground surface of the purification target region is a water shielding sheet or asphalt layer, but other airtight sheet material such as a steel plate or a resin plate, Plates and paving materials can also be used.

DESCRIPTION OF SYMBOLS 10 Groundwater purification system, 12 Impermeable wall, 20 Pumping well, 22 Submersible pump, 23 Casing, 24 Screen, 25 Pumping pipe, 26 holes, 27 Filter material, 28 Suction pipe, 29 Lid, 30 Injection well, 33 Casing, 34 Screen, 35 Water injection pipe, 36 holes, 37 Filter material, 39 Lid, 40 Water shielding sheet, 50 Water injection equipment, 52 Header pipe, 60 Vacuum suction equipment, 61 Water treatment equipment, 62 Header pipe, 64 Header pipe, 100 Groundwater purification System, 101 Non-permeable layer, 112 Impermeable wall, 130 Air supply / water injection well, 140 Asphalt layer, 172 Branch pipe, 174 On-off valve

Claims (6)

A groundwater purification system that purifies groundwater in the contaminated area by passing water through the contaminated area of the ground,
A water-impervious wall that surrounds the purification target area including the contamination range and is constructed to extend from the ground surface to a depth below the groundwater level in the outer peripheral side of the purification target area;
An airtight layer covering the ground surface of the area to be purified;
A water injection well that extends from the ground surface of the purification target region to a depth deeper than the contamination range, and injects water in a range from the ground surface of the purification target region to a depth deeper than the contamination range;
A groundwater purification system comprising a pumping well that extends from the ground surface of the purification target region to a depth deeper than the contamination range, has a negative pressure inside, and pumps water from a depth deeper than the contamination range.   The groundwater purification system according to claim 1, wherein the impermeable wall is constructed so as to extend to a hardly permeable layer that exists on a deeper side than the contamination range. A water injection system for injecting water into the area to be purified through the water injection well;
A groundwater purification system according to claim 1 or 2, further comprising: an air supply system that supplies air to the purification target region through the water injection well. A groundwater purification method for purifying groundwater in the contaminated area by passing water through the contaminated area of the ground,
A state in which the ground surface of the purification target region including the contamination range is surrounded by a water-impervious wall from the groundwater level of the region on the outer peripheral side of the purification target region, and the ground surface of the purification target region is covered with an airtight layer The water injection well extends from the ground surface of the purification target area to a depth deeper than the contamination range, and injects water in the range from the ground surface of the purification target area to the depth of the contamination range and the contamination from the ground surface of the purification target area. A groundwater purification method in which water is pumped from deeper than the contaminated area of the purification target area by a pumping well extending to a depth deeper than the range and having a negative pressure inside. A groundwater purification method for purifying groundwater in the contaminated area by passing water through the contaminated area of the ground,
Surrounding the ground surface of the purification target area including the contamination range to the poorly permeable layer existing deeper than the purification target area with a water-impervious wall, and covering the ground surface of the purification target area with an airtight layer In the state, a pumping well that extends from the ground surface of the purification target area to a depth deeper than the contamination range, and pumps water from a depth deeper than the contamination range of the purification target area by a pumping well having a negative pressure inside, and the ground of the purification target area A groundwater purification method for performing a water injection step of injecting water in a range from the ground surface of the purification target region to the depth below the contamination range by a water injection well extending from the surface to the depth below the contamination range. In the pumping process, air is supplied to the area to be purified through the water injection well,
The groundwater purification method according to claim 5, wherein in the water injection step, air is sucked from the purification target area through the pumping well.