JP6933333B2 - Method of pumping contaminated groundwater, method of in-situ purification of contaminated groundwater - Google Patents

Description

The present invention relates to a method of pumping contaminated groundwater and a method of in-situ purification of contaminated groundwater.

Groundwater pollution by organic pollutants (organochlorine compounds, 1,4-dioxane, cyanide, benzene, etc.) has become a problem.

Groundwater containing such organic pollutants is subjected to water treatment such as oxidative decomposition treatment and discharged into the environment.

For example, a method of adding a sulfur compound containing a peroxide group to water to be treated and performing an oxidative decomposition treatment using ultraviolet rays (see Patent Document 1) can be applied to water treatment of groundwater.

Further, as a method of oxidative decomposition treatment of groundwater, there is a method of purifying groundwater in place by directly adding a perluteate and a reducing agent to groundwater contaminated with an organic compound (Patent Document 2). reference).

Japanese Unexamined Patent Publication No. 11-99395 Japanese Unexamined Patent Publication No. 2011-173089

Here, the research by the present inventors has clarified that the metals contained in groundwater (light metals such as magnesium and heavy metals such as manganese) affect the treatment efficiency such as oxidative decomposition treatment.

Therefore, for example, when the oxidative decomposition treatment of Patent Document 1 is performed on groundwater containing a metal, the treatment efficiency is lowered. Further, even when the oxidative decomposition treatment is carried out by using the method of Patent Document 2, the influence of the metal contained in the soil at the original position cannot be avoided, so that the treatment efficiency is lowered.

An object of the present invention is to provide a method for pumping contaminated groundwater and a method for in-situ purification of contaminated groundwater, which can remove metals contained in groundwater in the soil before performing water treatment or groundwater purification. do.

In order to solve the above problems, the method for pumping contaminated groundwater of the present invention is a method for pumping contaminated groundwater contaminated with organic pollutants, and the soil around a pumping well for pumping the groundwater. It has an alkali supply step of supplying alkali to the water pumping well and a water pumping step of pumping the groundwater from the pumping well.
Further, the method for pumping contaminated groundwater of the present invention further includes a water treatment step of treating the groundwater pumped from the pumping well with water for removing the organic pollutants, and the alkali supply step is described above. The alkali may be added to the groundwater treated with water, and water may be intermittently injected into a plurality of water injection wells provided around the pumping well.
Further, in the method for pumping contaminated groundwater of the present invention, in the alkali supply step, the alkali is added to at least a part of the groundwater pumped from the pumping well to a plurality of water injection wells provided around the pumping well. Water may be injected.
Further, in the method for pumping contaminated groundwater of the present invention, at least a part of the groundwater pumped from the pumping well is injected into a water injection well provided outside the alkaline dropping well provided around the pumping well. The alkali supply step may further include a step, and the alkali may be dropped into the alkali dropping well.
Further, the method for pumping contaminated groundwater of the present invention further includes a water treatment step of treating the groundwater pumped from the pumping well with water for removing the organic pollutants, and the water injection step is the water. The treated groundwater may be injected into the water injection well.
Further, in the method for pumping contaminated groundwater of the present invention, the alkali supply step may be provided so as to surround the periphery of the pumping well with a permeator that is permeable to the groundwater and is filled with alkali.
Further, in order to solve the above problems, the in-situ purification method for contaminated groundwater of the present invention is an in-situ purification method for contaminated groundwater that purifies groundwater contaminated with organic pollutants in soil. It has an alkali supply step of supplying an alkali to the contained soil and a groundwater purification chemical supply step of supplying a chemical for groundwater purification to the soil downstream from the position where the alkali is supplied.
Further, the in-situ purification method for contaminated groundwater of the present invention further includes a pumping step of pumping the purified groundwater from a pumping well provided further downstream than the soil to which the chemical for purifying the groundwater is supplied. In the alkali supply step, the alkali is supplied to the soil by using the purified groundwater to which the alkali is added, and the chemical supply step for the groundwater purification is to the purified groundwater for the groundwater purification. It is also possible to supply the chemical for groundwater purification to the soil by using the chemical added to the soil.

According to the present invention, it is possible to remove the metal contained in the groundwater in the soil in advance before performing the water treatment or the purification of the groundwater.

In this embodiment, it is a figure which shows the outline from the pumping of groundwater to the discharge of purified groundwater into the environment. It is a figure for demonstrating the 1st example of the alkali supply process to soil. It is a figure for demonstrating the 2nd example of the alkali supply process to soil. It is a figure for demonstrating the 3rd example of the alkali supply process to soil. It is a figure for demonstrating the 4th example of the alkali supply process to soil. It is a figure for demonstrating the 4th alternative example of the alkali supply process to soil. It is a figure which shows the example of purifying contaminated groundwater in the in-situ. It is a figure which shows another example of purifying contaminated groundwater in the in-situ. It is a graph which showed the relationship between the amount of groundwater flow and manganese concentration.

== Embodiment ==
[About groundwater purification treatment]
The treatment for purifying groundwater contaminated with organic pollutants is performed, for example, with the following configuration. FIG. 1 is a diagram showing an outline from pumping groundwater to discharging purified groundwater into the environment (soil is shown in cross section). The arrows in the figure indicate the flow of water.

The pumping well 1 is a dedicated well for pumping groundwater, and stores groundwater that has permeated the soil around the pumping well 1. The pumping well 1 is preferably formed on land where groundwater is likely to be contaminated with organic pollutants, for example, near an illegal dumping site. The pumping well 1 only needs to be able to store groundwater, and its depth, diameter, shape, number, and the like are not particularly limited.

The pumping device 2 pumps the groundwater stored in the pumping well 1 to the ground. The pumping device 2 is not particularly limited as long as it has a configuration capable of pumping groundwater from the pumping well 1, such as a pump for pumping. The pumping device 2 sends the pumped groundwater to the water treatment device 3. The step of pumping groundwater from the pumping well 1 by the pumping device 2 is an example of the “pumping step”.

The water treatment device 3 performs water treatment for removing organic pollutants on the groundwater pumped from the pumping well 1. Water treatment is a method of purifying groundwater pumped up using plant equipment such as a tank. The water treatment is, for example, an oxidative decomposition treatment (Fenton treatment or the like), an activated carbon treatment, or a chelate treatment. The step of removing organic pollutants by the water treatment apparatus 3 is an example of the “water treatment step”. The water treatment device 3 discharges the treated groundwater (that is, purified groundwater) into the environment.

Here, when the pumped groundwater contains a metal, as described above, this metal affects the treatment efficiency of the oxidative decomposition treatment, the activated carbon treatment, and the chelate treatment. Therefore, as shown in FIG. 1, in the present invention, alkali is supplied to the soil around the pumping well 1 in advance to alkalinize the soil. The metal contained in groundwater is insolubilized when it permeates the alkalized soil, and is precipitated and filtered in the soil. That is, the metal is removed from the groundwater by allowing the groundwater containing the metal to permeate the alkalized soil. By pumping the groundwater from which the metal has been removed in this way, it becomes possible to efficiently perform water treatment of organic pollutants contained in the groundwater. The process of supplying alkali to the soil around the pumping well is an example of the “alkali supply process”. Hereinafter, a specific example of the process of supplying alkali to the soil will be described. The alkali supplied to the soil is sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, barium hydroxide, sodium carbonate, potassium carbonate, sodium sesquicarbonate or the like, or a salt thereof. Alkali can be supplied to soil in liquid (aqueous solution) or solid state.

[Alkali supply process (1)]
A first example of supplying alkali to the soil around the pumping well 1 will be described with reference to FIG. FIG. 2 is a top view of the soil. The pumping device 2, the water treatment device 3, and the alkali adding device 5 (described later) in FIG. 2 are schematically shown. The arrows in the figure indicate the flow of water.

In the first example, a plurality of water injection wells 4 are formed around the pumping well 1. In this example, four water injection wells 4 are formed (see FIG. 2). The depth, diameter, shape, number, arrangement, etc. of the water injection well 4 are not particularly limited. However, in order to completely supply alkali to the soil around the pumping well 1 (to completely alkalinize the soil around the pumping well 1), the distance between adjacent water injection wells 4 and each water injection well 4 It is preferable to form the same distance from the pumping well 1 to the pumping well 1. Further, it is preferable that the pumping well 1 and the water injection well 4 have the same depth.

As shown in FIG. 2, in the first example, a part of the water treated by the water treatment device 3 is discharged into the environment, and the remaining part is injected into the alkali addition device 5.

The alkali adding device 5 adds alkali to the injected groundwater. Then, the alkali addition device 5 injects groundwater (alkali aqueous solution) to which alkali has been added into each water injection well 4.

Here, it is preferable to inject water into the water injection well 4 intermittently. The groundwater injected into the water injection well 4 in the first example is water-treated. Therefore, in order to continuously inject water, it is necessary to constantly operate the water treatment device 3 to perform water treatment. In addition, since the groundwater once treated (purified groundwater) is returned to the soil, the groundwater needs to be purified again. Therefore, by intermittently injecting water into the water injection well 4, the amount of water treated by the water treatment device 3 can be suppressed.

The timing of intermittent water injection can be determined, for example, based on the degree of alkalinity of the soil. That is, the hydrogen ion index (pH) of the soil is periodically measured using a measuring device. When the pH becomes neutral to acidic (pH 7 or less), the water treatment device 3 injects water-treated groundwater into the alkali addition device 5. The alkali addition device 5 adds alkali to groundwater and injects water into the water injection well 4. In addition, the timing of intermittent water injection can be determined based on the metal concentration of the soil and the amount of groundwater injected.

In this way, the groundwater to which the alkali has been added permeates the soil around the water injection well 4 from the water injection well 4. As a result, the soil around the water injection well 4 is alkalized, and the soil around the pumping well 1 provided inside each water injection well 4 is also alkalized (the shaded portion in FIG. 2 indicates the alkalized soil). .. In this state, it is assumed that groundwater containing metals and organic pollutants has infiltrated from the soil outside the water injection well 4. In this case, when the groundwater permeates the alkalized soil, the metal contained in the groundwater is insolubilized and settled and filtered in the soil. Therefore, the groundwater stored in the pumping well 1 is groundwater containing almost only organic pollutants. When such groundwater is pumped and treated, the efficiency of water treatment is improved because it is hardly affected by metals.

[Alkali supply process (2)]
A second example of supplying alkali to the soil around the pumping well 1 will be described with reference to FIG. In the second example, groundwater before water treatment is used as the water to which the alkali is added. FIG. 3 is a cross-sectional view of the soil. The pumping device 2, the water treatment device 3, and the alkali adding device 5 in FIG. 3 are schematically shown. The arrows in the figure indicate the flow of water.

In the second example, as in the first example, a plurality of water injection wells 4 are formed around the pumping well 1. FIG. 3 shows two water injection wells 4. In FIG. 3, the diameters of the pumping well 1 and the water injection well 4 and the depth in the ground are formed to be equal. Further, the distances from the water injection wells 4 to the pumping wells 1 are also formed equally.

As shown in FIG. 3, in the second example, a part of the groundwater pumped from the pumping well 1 by the pumping device 2 is sent to the water treatment device 3, and the remaining part is sent to the alkali adding device 5. Water is injected.

The alkali addition device 5 adds alkali to the injected groundwater (groundwater that has not been treated with water). Then, the alkali addition device 5 injects groundwater to which alkali has been added into each water injection well 4. In the case of the second example, since it is not necessary to treat the groundwater to which the alkali is added with water, the water injection may be performed continuously (may be performed intermittently as in the first example).

As described above, in the second example, as in the first example, the metal contained in the groundwater can be removed in advance in the soil before the groundwater is pumped. Therefore, the treatment efficiency when treating the pumped groundwater is improved. Further, in the second example, since the groundwater before water treatment with an alkali added is used, it is possible to suppress an increase in the amount of water treatment.

[Alkali supply process (3)]
A third example of supplying alkali to the soil around the pumping well 1 will be described with reference to FIG. In the third example, a dedicated well (well for dropping alkali 6) for adding alkali is provided. FIG. 4 is a diagram showing an example of an alkali supply process to soil. FIG. 4A is a top view of the soil. Further, FIG. 4 (B) is a cross-sectional view of the soil (A-A cross section of FIG. 4 (A)). The pumping device 2, the water treatment device 3, and the alkali adding device 5 of FIGS. 4 (A) and 4 (B) are schematically shown. The arrows in the figure indicate the flow of water.

In the third example, a plurality of alkaline dropping wells 6 are formed around the pumping well 1. FIG. 4 shows four alkaline dropping wells 6. The alkali dropping well 6 is a well dedicated to dropping alkali, and as in the first example and the second example, instead of injecting groundwater to which alkali has been added, alkali can be directly dropped. In this example, the pumping well 1 and the alkaline dropping well 6 are formed to have the same depth in the ground (see FIG. 4 (B)). Further, the distance between the adjacent alkaline dropping wells 6 and the distance from each alkaline dropping well 6 to the pumping well 1 are also formed (see FIGS. 4A and 4B).

Further, a plurality of water injection wells 4 are formed outside the alkali dropping well 6 (four in this example). In this example, the diameters of the pumping well 1 and the water injection well 4 and the depth in the ground are formed to be equal (see FIG. 4B). Further, the distance between the adjacent water injection wells 4 and the distance from each water injection well 4 to the pumping well 1 are also formed (see FIGS. 4A and 4B).

As shown in FIG. 4, in the third example, the groundwater pumped from the pumping well 1 by the pumping device 2 is sent to the water treatment device 3. The water treatment device 3 discharges a part of the treated groundwater into the environment and injects the remaining part into the water injection well 4.

In this way, when the alkali is dropped into the alkali dropping well 6, if the alkali is a liquid, it permeates the soil around the alkali dropping well 6. Alternatively, even when the alkali is solid, the groundwater or the like that has permeated from the water injection well 4 or the like permeates the alkali dropping well 6, so that the alkali dissolves and permeates the soil around the alkali dropping well 6. As a result, the soil around each alkaline dropping well 6 is alkalized, and the soil around the pumping well 1 provided inside the alkaline dropping well 6 is also alkalized (the shaded portion in FIG. 4 is alkalized). Indicates soil). In this state, it is assumed that groundwater containing metals and organic pollutants has infiltrated from the soil outside the water injection well 4. In this case, when the groundwater permeates the alkalized soil, the metal contained in the groundwater is insolubilized and settled and filtered in the soil. Therefore, the groundwater stored in the pumping well 1 is groundwater containing almost only organic pollutants. When such groundwater is pumped and treated, the efficiency of water treatment is improved because it is hardly affected by metals. Further, the third example is simple because it is not necessary to pump groundwater to add alkali or to add alkali to the pumped groundwater. Moreover, since it is not necessary to dissolve the alkali in the groundwater, a highly concentrated alkali can be added to the soil.

Note that FIG. 4 shows an example in which the treated groundwater is injected into the water injection well 4, but the present invention is not limited to this. That is, instead of the water treatment device 3 injecting groundwater into the water injection well 4, the water pumping device 2 injects a part of the groundwater (groundwater containing organic pollutants) to be sent to the water treatment device 3 into the water injection well 4. It may be. The above description does not exclude the method of injecting both the treated groundwater and the groundwater containing organic pollutants into the water injection well 4.

[Alkali supply process (4)]
A fourth example of supplying alkali to the soil around the pumping well 1 will be described with reference to FIGS. 5 and 6. A fourth example is a method of surrounding the pumping well 1 with an alkali-filled permeator 7. 5 and 6 are top views of the soil.

In the fourth example, the permeator 7 is formed around the pumping well 1. In this example, the permeator 7 is formed on the entire circumference of the pumping well 1. The permeator 7 is filled with alkali and other filler (for example, silica sand) and permeates groundwater. Further, when the groundwater permeates the permeate 7, the alkali contained in the permeate 7 dissolves in the groundwater and permeates the soil. As shown in FIG. 5, the permeator 7 is formed by drilling a plurality of holes similar to those of the water injection well 4 and the like around the pumping well 1 and filling the holes with an alkali and a filler. Alternatively, as shown in FIG. 6, it is also possible to form the wall-shaped transparent body 7. As a method for forming such a wall-shaped transparent body 7, the production method described in Japanese Patent Application Laid-Open No. 2015-188773 can be used. The depth, thickness, and the like of the transmissive body 7 are not particularly limited. However, the depth (length) of the permeator 7 in the soil is preferably equal to the depth of the pumping well 1.

In this way, the groundwater that has permeated the permeator 7 formed so as to surround the periphery of the pumping well 1 allows the alkali to permeate the soil inside the permeator 7. Therefore, the soil around the pumping well 1 can be alkalized (the shaded areas in FIGS. 5 and 6 indicate the alkalized soil). In this state, it is assumed that groundwater containing metals and organic pollutants has further infiltrated from the soil outside the permeator 7. In this case, when the groundwater permeates the alkalized soil, the metal contained in the groundwater is insolubilized and settled and filtered in the soil. Therefore, the groundwater stored in the pumping well 1 is groundwater containing almost only organic pollutants. When such groundwater is pumped and treated, the efficiency of water treatment is improved because it is hardly affected by metals. Further, in the fourth example, since the permeator 7 is formed so as to surround the periphery of the pumping well 1, the soil around the pumping well 1 can be more reliably alkalized. The permeator 7 does not necessarily have to be provided on the entire circumference of the pumping well 1.

[Regarding in-situ groundwater purification treatment]
It is also possible to purify groundwater in the in-situ (in the soil) by using the above-mentioned alkali supply process. FIG. 7 is a diagram showing an example of purifying contaminated groundwater at the in-situ. FIG. 7 is a top view of the soil. The arrows in the figure indicate the flow of water (groundwater flows from the upstream side to the downstream side).

As shown in FIG. 7, a water injection well 4 similar to the above example is formed on the upstream side of the soil. In this example, three water injection wells 4 are formed (see FIG. 7). For example, groundwater to which alkali has been added is injected into the water injection well 4.

On the other hand, a chemical injection well 8 for purifying groundwater is formed on the downstream side of the water injection well 4. The depth, diameter, shape, number, arrangement, etc. of the groundwater purification chemical injection well 8 are not particularly limited. However, in order to purify the groundwater in the soil thoroughly, it is preferable to form the adjacent groundwater purification chemical injection wells 8 at equal intervals. Further, it is preferable that the water injection well 4 and the groundwater purification chemical injection well 8 have the same depth. The "groundwater purification" is a method of purifying groundwater in the original position without using plant equipment such as a tank.

A chemical for purifying groundwater is a chemical for decomposing, adsorbing, and purifying pollutants in groundwater. Chemicals for groundwater purification include, for example, sodium peroxodisulfate (oxidizing agent), activated carbon for activated carbon treatment, chelating agent for chelating treatment, and the like.

In the configuration of FIG. 7, the groundwater to which the alkali has been added permeates the soil around the water injection well 4 from the water injection well 4. As a result, the soil around the water injection well 4 is alkalized (the shaded portion in FIG. 7 indicates the alkalized soil). In this state, it is assumed that groundwater containing metals and organic pollutants has infiltrated from the soil on the upstream side of the water injection well 4. In this case, when the groundwater permeates the alkalized soil, the metal contained in the groundwater is insolubilized and settled and filtered in the soil. Therefore, the groundwater that has permeated the downstream side of the water injection well 4 is groundwater that contains almost only organic pollutants. Further, when such groundwater permeates the groundwater purification chemical injection well 8, purification is performed by the groundwater purification chemical. Therefore, it is possible to purify the groundwater in the original position (in the soil). Moreover, since the groundwater to be purified is almost unaffected by metals, the efficiency of groundwater purification is improved. As described above, the step of supplying the chemical for groundwater purification to the soil downstream from the position where the alkali is supplied is an example of the “groundwater purification chemical supply step”.

Further, FIG. 8 shows a configuration in which the permeator 9 filled with the groundwater purification agent is provided on the downstream side of the permeator 7 filled with alkali, and the pumping well 1 is provided on the downstream side of the permeator 9. .. FIG. 8 is a top view of the soil.

In this example, the permeator 9 is formed on the downstream side of the permeator 7 (upstream side of the pumping well 1) so as to surround the pumping well 1. In this example, the permeator 9 is formed on the entire circumference of the pumping well 1. The permeator 9 is filled with a chemical for purifying groundwater and permeates the groundwater.

In this way, the groundwater that has permeated the permeator 7 formed on the upstream side allows the alkali to permeate the soil inside the permeator 7. Therefore, the soil around the pumping well 1 can be alkalized (the shaded portion in FIG. 8 indicates the alkalized soil). In this state, it is assumed that groundwater containing metals and organic pollutants has further infiltrated from the soil on the upstream side of the permeator 7. In this case, when the groundwater permeates the alkalized soil, the metal contained in the groundwater is insolubilized and settled and filtered in the soil. Therefore, the groundwater that has permeated the downstream side of the permeate 7 is groundwater that contains almost only organic pollutants. Further, when such groundwater permeates the permeating body 9, it is purified by a groundwater purifying agent. Therefore, it is possible to purify the groundwater in the original position (in the soil). That is, the groundwater pumped from the pumping well 1 provided further downstream than the permeate 9 is purified groundwater. Therefore, it is possible to discharge the water into the environment as it is without purifying it after pumping. The permeator 9 does not necessarily have to be provided on the entire circumference of the pumping well 1.

Further, in the configuration of FIG. 7, it is also possible to provide a pumping well 1 on the downstream side of the groundwater purification chemical injection well 8. In this case, the alkali can be supplied to the soil by injecting the groundwater pumped from the pumping well 1 (groundwater purified in the original position) with alkali added to the water injection well 4. Alternatively, the groundwater purification chemicals are supplied to the soil by injecting the groundwater purification chemicals added to the groundwater pumped from the pumping well 1 (groundwater purified in the original position) into the groundwater purification chemical injection well 8. It is also possible to do.

== Example ==
[Treatment efficiency of oxidative decomposition treatment]
The efficiency of water treatment by adding alkali was verified by the following tests (Examples 1 to 3 and Comparative Example 1). The test was carried out according to the following procedure.

First, a filler obtained by mixing mountain sand (produced in Nagano Prefecture) and Tochikure (clay produced in Tochigi Prefecture, manufactured by Kanto Kasei Co., Ltd.) at a ratio of 19: 1 was filled in a column so as to have a specific gravity of 1.8. The total length of the column is 20 cm, and the column diameter is 5 cm. In Examples 2 and 3, a material obtained by adding calcium hydroxide to a filler obtained by mixing mountain sand and toticley in the above ratio (Example 2: The ratio of calcium hydroxide to the filler is 1%, Example 3: Filler). The upper layer (4 cm) of the column was filled (the ratio of calcium hydroxide to 10%) (the lower layer portion (filler containing only mountain sand and toticley) was 16 cm).

Groundwater was passed through the upper layer of the prepared column, and the water flow was collected. The amount of manganese contained in the water passage was measured by an atomic absorption spectrophotometer. In addition, the pH of the water flow liquid before and after the Fenton treatment (an example of water treatment) and the concentration of 1,4-dioxane (an example of an organic pollutant) were measured by a gas chromatograph mass spectrometer. In the Fenton treatment, 0.1 mL of hydrogen peroxide solution having a 35% concentration was added to 50 mL of a water passing solution so that hydrogen peroxide became 20 mM, and ferrous sulfate became 2 mM. 0.1 mL of 1 mol / L ferrous sulfate was added to 50 mL of a water flow solution.

The groundwater shown in Table 1 (produced in the Tohoku region) was used as the groundwater flowing through the column. In Example 1, 250 mL of groundwater to which a sodium hydroxide reagent (2.5 g) was added so that the sodium hydroxide concentration in the groundwater was 1% was passed. In Example 2 and Example 3, 250 mL of groundwater was passed through. In Comparative Example 1 (control group), 500 mL of groundwater was passed through.

As shown in Table 2, according to Example 1, the pH of the water passing liquid showed higher alkalinity than the pH of the original groundwater. Further, according to Example 1, the manganese concentration in the water flow liquid was remarkably reduced. Furthermore, according to Example 1, the concentration of 1,4-dioxane after the Fenton treatment was significantly reduced.

On the other hand, according to Comparative Example 1, the water flow solution contained manganese at a higher concentration than that of Example 1. In addition, the dioxane concentration after the fenton treatment did not decrease as compared with Example 1.

From the above results, it is considered that in Example 1, the alkali added to the groundwater alkalizes the column layer, and manganese is precipitated and filtered there. It was also clarified that the smaller the amount of manganese contained in the water passage, the higher the efficiency of the Fenton treatment.

Further, according to the results of Examples 2 and 3, it was clarified that manganese could be removed by the permeation layer of calcium hydroxide, and as a result, the efficiency of the fenton treatment was increased.

[Durability of manganese removal effect by alkali]
We tested how long the manganese removal effect lasted when the column was alkalized. When 1 L of groundwater to which the 1% sodium hydroxide aqueous solution used in Example 1 is added is passed through the column, and then 2 L of groundwater only (groundwater to which 1% sodium hydroxide aqueous solution is not added) is passed through the column. The concentration of manganese contained in the water flow solution was measured. The manganese concentration was measured by the same method as in the above example.

FIG. 9 is a graph showing the amount of groundwater flowing (mL) on the horizontal axis and the manganese concentration (mg / L) on the vertical axis. According to FIG. 9, the alkalized column filler maintains the manganese removing effect even at the time of 2 L of water flow (3 L in total). For example, the manganese concentration at the time of passing 3 L of water is about 6 mg / L, which is considerably reduced as compared with the manganese concentration (37 mg / L) of Comparative Example 1 above.

According to this test, it was clarified that the soil once alkalized can maintain the metal removing effect even during the subsequent water injection. That is, it has been clarified that it is not always necessary to supply the alkali to the soil, and for example, as shown in the first example in the embodiment, the effect of the present invention can be obtained by intermittently supplying the alkali. ..

== Other ==
In the above embodiment, the configuration for alkalizing the soil has been described, but it is also possible to remove the metal by adding an oxidizing agent instead of the alkali and oxidizing the soil.

The above-described embodiments and the like are presented as examples, and do not limit the scope of the invention. The above configurations can be implemented in appropriate combinations, and various omissions, replacements, and changes can be made without departing from the gist of the invention. The above-described embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

1 Water pumping well 2 Water pumping device 3 Water treatment device 4 Water injection well 5 Alkali addition device

Claims (2)

A method of pumping contaminated groundwater that pumps groundwater contaminated with organic pollutants.
An alkali supply step of supplying alkali to the soil around the pumping well for pumping the groundwater and alkalizing the soil to insolubilize heavy metals in the groundwater.
A pumping process for pumping the groundwater from the pumping well,
A water injection step of injecting at least a part of the groundwater pumped from the pumping well into a water injection well provided outside the alkaline dropping well provided around the pumping well.
Have,
The alkali supply step is a method of pumping contaminated groundwater by dropping alkali into the alkali dropping well. Further having a water treatment step of performing water treatment for removing the organic pollutants on the groundwater pumped from the pumping well.
The water injection process, pumping method of polluted groundwater according to claim 1 wherein the water injection groundwater subjected to the water treatment in the water injection well.

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