JP2012183498A - Method for improving contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for improving contaminated soil excellent in a removal effect of contaminants by eluting the contaminants contained in the soil effectively, and by adsorbing the contaminants on contact with an adsorbent effectively.SOLUTION: The method for improving contaminated soil in which contaminants contained in groundwater is absorbed by an adsorbent 2 on contact with the groundwater flowing through the ground 1 where soil is contaminated by contaminants to the adsorbent 2 embedded in the ground 1, or on contact with the groundwater pumped up on the ground to the adsorbent 2 on the ground, includes injection of carbon dioxide into the ground 1 where the soil is contaminated by contaminants.

Description

  The present invention relates to a method for improving contaminated soil.

  Conventionally, patent document 1 is known as a contaminated soil improvement method. In the conventional example shown in Patent Document 1, a storage cylinder having a water passage hole is inserted into the soil where the soil is contaminated, and an adsorbent is put in and out of the storage cylinder so as to be freely inserted. The adsorbent absorbs contaminants contained in the groundwater that has entered the storage cylinder through the water holes.

  Here, the pollutant contained in the soil is gradually dissolved in the groundwater, and the groundwater from which the pollutant is eluted comes into contact with the adsorbent, so that the pollutant is adsorbed on the adsorbent.

JP 2009-297617 A

  However, the speed at which the pollutants contained in the soil dissolve and move in the groundwater is limited by the type and particle size of the soil, and is 1 m / year even in general sandy soil. In the case of silt or clay layers, groundwater As it is difficult to penetrate, it takes 10 to 100 times as many years.

  Therefore, it is conceivable to increase the speed of movement by flowing water, but if the water simply contacts the contaminated soil, the amount of elution will be small because the pollutants contained in the soil will only elute gradually. Takes time. Moreover, it is not easy to flow water from the upper layer to the lower layer on average.

  Therefore, there is a problem that it takes a long time to remove pollutants for a long time only by the method of eluting the pollutants into the groundwater and adsorbing the adsorbent with the adsorbent.

  The present invention was invented in view of the problems of the conventional example described above, and the object of the present invention is to effectively elute contaminants contained in the soil and to effectively contact the adsorbent. It is an object of the present invention to provide a method for improving contaminated soil that can effectively adsorb and remove pollutants and shorten the time required for removing pollutants.

  In the method for improving contaminated soil according to the present invention, the groundwater flowing through the underground 1 where the soil is contaminated with the contaminant is brought into contact with the adsorbent 2 embedded in the underground 1 or the groundwater is pumped to the ground to adsorb the groundwater. 2, the adsorbent 2 absorbs the pollutant contained in the groundwater in contact with 2, and carbon dioxide gas is injected into the ground 1 where the soil is contaminated with the pollutant.

  By adopting this method, the amount of arsenic and other contaminants eluted into the groundwater will increase, and the permeability of carbon dioxide (carbon dioxide) in the ground will expand the gap in which groundwater flows in the ground. Thus, the movement of the groundwater containing the contaminant can be improved, and the contaminant can be adsorbed by the adsorbent 2 and removed.

  In addition, water is poured into the ground from the water injection cylinder 3 inserted into the underground 1 where the soil is contaminated with pollutants, and the groundwater is pumped from the pumping cylinder 4 inserted into the ground. Contamination in the groundwater flowing through the communication pipe 5 is formed by forming a circulation channel 7 that is supplied again to the water injection cylinder 3 by the pump 6 through the communication pipe 5 in which the adsorbent 2 is arranged, and injected into the ground. In the case of adsorbing a substance with the adsorbent 2, it is preferable that carbon dioxide gas is injected into the underground 1 where the soil is contaminated with a pollutant.

  By adopting such a method, the contaminant contained in the circulating groundwater can be effectively adsorbed and removed by the adsorbent 2 while circulating the groundwater containing the contaminant. In this case, by injecting carbon dioxide into the ground 1, the amount of the pollutant elution from the soil increases due to the chemical reaction between the pollutant and carbon dioxide, and the underground water flows into the ground 1 due to the permeability of carbon dioxide. It can be removed by adsorbing with the adsorbent 2 by enlarging the flowing gap, improving the movement of groundwater containing pollutants. Moreover, it becomes possible to arrange | position the communicating pipe 5 on the ground, and to replace | exchange the adsorbent 2 on the ground, and replacement | exchange and disposal of the adsorbent 2 become easy.

  Further, a storage cylinder 8 having a water passage hole is inserted into the soil where the soil is contaminated, and an adsorbent is put in and out of the storage cylinder so as to be freely stored, and the storage cylinder is inserted through the water passage hole. It is preferable to inject carbon dioxide into the underground 1 where the soil is contaminated, in the case where the adsorbent 2 absorbs contaminants contained in the groundwater that has entered into the ground 8.

  By injecting carbon dioxide into the underground 1 where the soil is contaminated in this way, the amount of pollutant elution from the soil increases and the permeability of the carbon dioxide expands the voids through which groundwater flows. It can be removed by adsorbing the adsorbent 2 with good movement of groundwater containing pollutants. Moreover, it becomes possible to remove the adsorbent 2 from the storage cylinder 8, and the adsorbent 2 can be easily replaced and disposed.

  Moreover, it is preferable to insert the water supply cylinder 9 into the underground 1 and pour water into the underground 1 from the water supply cylinder 9.

  By adopting such a method, it is possible to promote the flow of groundwater, increase the water flowing through the voids enlarged by the permeability of carbon dioxide gas, and more effectively remove contaminants.

  In the present invention, since carbon dioxide is injected into the ground where the soil is contaminated with the pollutant as described above, the amount of the pollutant eluted from the soil increases, and the permeability of carbon dioxide causes groundwater to enter the ground. It is possible to expand the gap through which the water flows, improve the movement of the groundwater containing pollutants, and adsorb it with an adsorbent so that it can be effectively adsorbed. Thereby, the period required for the removal of soil pollutants in the ground can be shortened.

It is explanatory drawing of one Embodiment of this invention. It is explanatory drawing of other embodiment same as the above. It is explanatory drawing of other embodiment same as the above. It is explanatory drawing of other embodiment same as the above.

  Hereinafter, the present invention will be described based on embodiments shown in the accompanying drawings.

  FIG. 1 shows an embodiment of the present invention. In the present embodiment, first, a metal pipe, a synthetic resin pipe, and a ceramic industry in which a large number of water injection holes 10 such as small holes and slits are provided on the outer periphery in the ground 1 where the soil is contaminated with heavy metals such as lead and arsenic. A water injection cylinder 3 such as a system cylinder, and a pumping cylinder 4 such as a metal pipe, a synthetic resin pipe, and a ceramic industry cylinder provided with a large number of suction holes 11 such as small holes and slits on the outer periphery are embedded.

  The water injection cylinder 3 is embedded in the underground 1 to inject water into the underground 1 from the water injection hole 10, and the pumping cylinder 4 pumps ground water from the suction hole 11. This is because it is buried in the ground 1 for this purpose. Here, the suction hole 11 does not allow the earth and sand to pass through, but allows water to pass through.

  The upper end of the water injection cylinder 3 and the upper end of the pumping cylinder 4 are each shielded by a lid, and both ends of the communication pipe 5 penetrate the lid of the water injection cylinder 3 and the cover of the communication pipe 5. The water injection cylinder 3 and the pumping cylinder 4 are connected in communication.

  A pump 6 and an adsorbent storage part 12 are provided in the middle of the communication pipe 5, and the pump 6 and the adsorbent storage part 12 are located on the ground.

  The adsorbent storage unit 12 accommodates the adsorbent 2 so that it can be inserted and removed freely. In this case, the adsorbent 2 is stored in the adsorbent storage portion 12 in a state where it is put in a bag 16 that is water-permeable and does not flow out of the adsorbent. The adsorbent 2 to be used is not particularly limited as long as it adsorbs contaminants. For example, iron powder, zeolite, incinerated ash, mineral powder, clay and the like are used alone or in combination.

  As described above, the water injection cylinder 3 for injecting water into the underground 1 and the pumping cylinder 4 for pumping the underground water in the underground 1 are connected to each other having the pump 6 and the adsorbent storage part 12. By connecting the pipe 5 for communication, the water injection cylinder 3 → the underground 1 → the pumping cylinder 4 → the communication pipe 5 having the pump 6 and the adsorbent storage part 12 → the water injection cylinder 3 is circulated through the groundwater. A path 7 is formed.

  A water supply pipe 18 is further connected to the communication pipe 5 through a valve 13.

  Further, a carbon dioxide supply unit 14 is connected to the water injection cylinder 3 so that carbon dioxide can be supplied from the carbon dioxide supply unit 14 to the water injection cylinder 3.

  The contaminated soil is improved using the apparatus as described above.

  As a basic operation of the apparatus, the pump 6 is operated to pump ground water from the pumping cylinder 4 and supplied to the water injection cylinder 3 through the adsorbent storage section 12 storing the adsorbent 2 for water injection. An operation of returning groundwater from the water injection hole 10 of the cylinder 3 to the underground 1 is performed. In other words, the circulation operation is performed in which the circulation channel 7 is formed while the groundwater penetrates through the underground 1 where the soil is contaminated. Thereby, the pollutant contained in the soil is eluted in the groundwater penetrating the underground 1, and the pollutant is adsorbed by the adsorbent 2 when the groundwater from which this pollutant has eluted passes through the adsorbent 2.

  In the present embodiment, the carbon dioxide injection operation is performed before the groundwater circulation operation, or the carbon dioxide injection operation is performed in parallel with the groundwater circulation operation, or before the groundwater circulation operation. In addition to the carbon dioxide gas injection operation, the carbon dioxide gas injection operation is performed in parallel with the groundwater circulation operation.

  Here, when the carbon dioxide injection operation is performed before the ground water circulation operation and in parallel with the circulation operation, the carbon dioxide gas injection operation may be performed continuously or intermittently. May be performed. In some cases, especially in an enclosed space, air is mixed with carbon dioxide and injected.

  By injecting carbon dioxide gas into the underground 1 from the water injection cylinder 3, the carbon dioxide gas reacts with the water in the underground 1 to become carbonated water. Then, these carbonated water and carbon dioxide gas come into contact with the soil containing the pollutant to elute the pollutant, and the voids between the soil particles are widened by the permeability of the carbon dioxide gas. Therefore, the groundwater penetrates into the voids between the soil particles spread by the penetration of carbon dioxide gas, and the groundwater penetrates even in the silt layer and the clay layer.

  In this way, it is possible to increase the amount of contaminants eluted from the contaminated soil and increase the amount of groundwater infiltration. Therefore, in the circulation operation in which groundwater circulates in the circulation channel 7 as described above, the amount of contaminants dissolved in the groundwater pumped by the pumping cylinder 4 increases, and the contaminants adsorbed by the adsorbent 2 are increased. The amount increases, pollutants in the contaminated soil can be effectively removed in a short period of time, and the soil can be improved underground.

  When a certain period of time has passed or when it is confirmed that the adsorption of the pollutant to the adsorbent 2 is saturated, the bag 16 containing the adsorbent 2 is taken out of the adsorbent storage unit 12 and newly adsorbed. The bag 16 containing the material 2 is stored in the adsorbent storage unit 12.

  In the present embodiment, when the amount of circulating groundwater decreases, the valve 13 is opened, water is supplied from the water supply pipe 18, and water is injected from the water injection cylinder 3 into the ground 1.

  FIG. 2 shows another embodiment of the present invention. In the above embodiment, an example in which carbon dioxide gas is injected into the ground 1 using the water injection cylinder 3 is shown. However, in this embodiment, a carbon dioxide injection pipe 15 different from the water injection cylinder 3 is provided in the ground. In this example, carbon dioxide is injected into the underground 1 from the carbon dioxide injection pipe 15. Since other configurations are the same as those of the above-described embodiment, description thereof is omitted.

  Next, still another embodiment of the present invention will be described with reference to FIG.

  In the present embodiment, a storage cylinder 8 having a water passage hole 17 in the underground 1 where the soil is contaminated with a contaminant and a carbon dioxide injection pipe 15 are inserted into the underground 1.

  The adsorbent 2 is stored in the storage cylinder 8. The adsorbent 2 is put in a water-permeable bag 16 and suspended by a string 19 or the like and stored in the storage cylinder 8. By pulling up the string 19, the bag 16 containing the adsorbent 2 is taken out to the ground by attaching a pulley to the bottom of the tube, passing the cover 19, etc., and again storing the bag 16 containing the new adsorbent 2. I can do it.

  When the groundwater comes into contact with the contaminated soil containing the pollutant, the pollutant is dissolved in the groundwater, and the groundwater in which the pollutant is dissolved enters through the water passage hole 17 and comes into contact with the adsorbent 2, thereby Contaminants contained in the adsorbent 2 are adsorbed.

  Here, in the present embodiment, carbon dioxide is injected into the ground 1 from the carbon dioxide supply unit 14 through the carbon dioxide injection pipe 15. In injecting the carbon dioxide gas, it is continuously injected for a certain period (time) or intermittently within a certain period (time).

  By injecting carbon dioxide into the underground 1 from the carbon dioxide injection pipe 15, the carbon dioxide reacts with the water in the underground 1 to become carbonated water. Then, these carbonated water and carbon dioxide gas come into contact with the soil containing the pollutant to elute the pollutant, and the voids between the soil particles are widened by the permeability of the carbon dioxide gas. Therefore, the groundwater penetrates into the voids between the soil particles spread by the penetration of carbon dioxide gas, and the groundwater penetrates even in the silt layer and the clay layer.

  In this way, it is possible to increase the amount of contaminants eluted from the contaminated soil and increase the amount of groundwater infiltration. Therefore, the amount of contaminants adsorbed in contact with the adsorbent 2 increases, and the soil can be effectively improved underground in a short period of time.

  Next, still another embodiment of the present invention will be described with reference to FIG.

  In this embodiment, in the embodiment shown in FIG. 3, the water supply cylinder 9 is further inserted into the ground, and water is injected from the water supply cylinder 9 into the ground 1.

  Carbon dioxide gas is injected in parallel with the operation of injecting carbon dioxide gas before water is injected into the underground 1 from the water supply cylinder 9 or in parallel with the injection of water into the underground 1 from the water supply cylinder 9. Carbon dioxide gas is injected in parallel with the injection operation of carbon dioxide gas before water is injected into the underground 1 from the water supply cylinder 9 and water is injected into the underground 1 from the water supply cylinder 9 Perform the injection operation.

  Here, when performing the carbon dioxide gas injection operation in parallel with the operation of pouring water into the underground 1 from the water supply cylinder 9, the carbon dioxide gas injection operation may be performed continuously or intermittently. A gas injection operation may be performed.

  In the present embodiment, by injecting carbon dioxide into the underground 1, the carbon dioxide reacts with the water in the underground 1 to become carbonated water. Then, these carbonated water and carbon dioxide gas come into contact with the soil containing the pollutant to elute the pollutant, and the voids between the soil particles are widened by the permeability of the carbon dioxide gas.

  In addition, the flow of groundwater can be promoted by injecting water into the underground 1 from the water supply cylinder 9, so that the groundwater penetrates into the voids between the soil particles spread by the penetration of carbon dioxide gas, and the silt layer Even in clay layers, groundwater penetrates.

  In this way, it is possible to increase the elution amount of the pollutant from the contaminated soil and to increase the amount of permeation by promoting the flow of groundwater. Therefore, the amount of contaminants adsorbed in contact with the adsorbent 2 increases, and the soil can be effectively improved underground in a short period of time.

Hereinafter, an experimental example of the above-described embodiment of FIG. 1 will be described.
[Experimental Example 1]
(Conditions for experiment)
A pipe of φ10 mm was used as the water injection cylinder 3 and the pumping cylinder 4 and buried in the ground 1. In this case, the embedding depth H of the water injection cylinder 3 and the pumping cylinder 4 in the ground 1 was 100 cm, and the length M between the water injection cylinder 3 and the pumping cylinder 4 was 100 cm. Further, the depth N from the ground GL to the groundwater level was 10 cm.

  -Moreover, as the adsorbent 2, what mixed iron powder, zeolite, incinerated ash, and clay was used, and it put into the bag 16 and accommodated in the adsorbent accommodating part 12. FIG.

  The position between the water injection cylinder 3 and the pumping cylinder 4 in the underground 1 and a depth of 80 cm from the ground surface was defined as the measurement point X.

  First, groundwater at the measurement point X before treatment was collected, and the concentrations of lead and arsenic in the groundwater at the measurement point X were measured. The lead concentration before treatment was 0.1 mg / l. The arsenic concentration was 0.1 mg / l.

-Next, carbon dioxide gas is supplied to the water injection cylinder 3 from a liquefied carbon dioxide gas cylinder (carbon dioxide supply part 14) liquefied with carbon dioxide using a regulator (pressure regulator). Gas was injected into the ground 1. The injection pressure was 0.5 kg / cm ² .

  Carbon dioxide was injected into the underground 1 for 24 hours, and water in the pumping cylinder 4 after the 24 hours injection was collected and the initial pH was measured to be pH 6.

  After the carbon dioxide injection is completed, the pump 6 is operated to suck the groundwater in the pumping cylinder 4, and the water is injected into the ground 1 through the communication pipe 5 and the water injection cylinder 3, and the water injection cylinder 3 → Ground 1 → Pump 4 for pumping → Circuit pipe 5 having a pump 6 and adsorbent storage part 12 → Circulating water for ground water in which a circulation channel 7 for ground water is formed as water injection cylinder 3 . In this case, the flow of water was gentle, and if water was insufficient, the valve 13 was opened and water was supplied from the water supply pipe 18.

  The above groundwater circulation operation was continued for 20 days.

(result)
-After carrying out circulation operation for 20 days, the groundwater of the measurement point X was extract | collected, and the density | concentration of lead and arsenic in the groundwater in the measurement point X was measured. The lead concentration was 0.008 mg / l. Arsenic could not be detected.
[Experiment 2]
The experiment was performed under the same conditions as in Experimental Example 1 except that the carbon dioxide gas injection pressure into the underground 1 was 1.0 kg / cm ² .

  -Groundwater was collected at measurement point X before treatment, and the concentrations of lead and arsenic in groundwater at measurement point X were measured. The lead concentration before treatment was 0.1 mg / l. The arsenic concentration was 0.1 mg / l.

  -After injecting carbon dioxide into the underground 1 for 24 hours, the water in the pumping cylinder 4 was collected and the initial pH was measured to be pH 5.

  -After carrying out circulation operation for 20 days, the groundwater of the measurement point X was extract | collected and the density | concentration of lead and arsenic in the groundwater in the measurement point X was measured. The lead concentration was 0.002 mg / l. Arsenic could not be detected.

  As is clear from Experimental Example 1 and Experimental Example 2, it is found that both the lead concentration and the arsenic concentration after the treatment were reduced to a contamination standard value of 0.01 mg / l or less.

DESCRIPTION OF SYMBOLS 1 Underground 2 Adsorbent 3 Cylinder for water injection 4 Cylinder for pumping 5 Communication pipe 6 Pump 7 Circulation flow path 8 Storage cylinder 9 Water supply cylinder

Claims (4)

  The groundwater flowing through the ground where the soil is contaminated with the pollutant is brought into contact with the adsorbent buried in the ground, or the groundwater is pumped to the ground and brought into contact with the adsorbent on the ground to remove the pollutant contained in the groundwater. A method for improving contaminated soil, characterized by injecting carbon dioxide into the ground where the soil is contaminated with a pollutant in what is absorbed by an adsorbent. Water is poured into the ground from a water injection cylinder inserted into the ground where the soil is contaminated with pollutants, groundwater is pumped from the pumping cylinder inserted into the ground, and adsorbents are placed on the groundwater that has been pumped up. In the one that forms a circulation channel that is supplied to the water injection cylinder again by the pump through the arranged communication pipe and injected into the ground, and adsorbs contaminants in the groundwater flowing through the communication pipe with an adsorbent,
2. The method for improving contaminated soil according to claim 1, wherein carbon dioxide gas is injected into the ground where the soil is contaminated with a pollutant.   A storage cylinder having a water passage hole is inserted into the soil where the soil is contaminated, and the adsorbent is put in and out of the storage cylinder so as to be freely inserted into the storage cylinder and enters the storage cylinder through the water passage hole. 2. The method for improving contaminated soil according to claim 1, wherein carbon dioxide gas is injected into the ground where the soil is contaminated in the material that absorbs the pollutant contained in the groundwater with an adsorbent. 4. The method for improving contaminated soil according to claim 3, wherein a water supply cylinder is inserted into the ground, and water is poured into the ground from the water supply cylinder.

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