JP3191132B2 - How to clean contaminated soil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning contaminated soil, particularly suitable for cleaning contaminated soil in an unsaturated zone.

[0002]

2. Description of the Related Art Contamination of soil and groundwater occurs when the soil itself in the target area is contaminated (soil contamination).
Groundwater itself is contaminated (groundwater contamination). Among these, soil pollution mainly occurs when pollutants are adsorbed on the soil in the unsaturated zone above the groundwater table, and when soil pollutants are adsorbed on the soil in the saturated zone below the groundwater table. There is. The former is currently limited to soil pollution, but in the long term, pollutants are transported from the unsaturated zone to the lower saturated zone due to the effects of rainfall infiltration, which may lead to groundwater contamination and new soil contamination. There is also.

Conventionally, as a countermeasure against soil contamination, containment and replacement have been performed.

[0004]

However, in the conventional method of soil contamination, such as containment and replacement, the treatment becomes large-scale when the depth of the contaminated soil is deep or the distribution range is large, so that the treatment cost is high. There is a problem that it increases.

The present invention has been made in view of the above circumstances, and even if contaminated soil is deep and distributed over a wide area, the contaminated soil can be inexpensively cleaned with a simple device, and moreover, the present invention is not limited to this. An object of the present invention is to provide a method for cleaning contaminated soil that can effectively clean contaminated soil distributed in a saturated zone.

[0006]

According to the present invention, there is provided a method for cleaning contaminated soil, wherein the contaminated soil is laterally surrounded by a water stop wall constructed to a depth equal to or lower than the groundwater level, and an area surrounded by the water stop wall is provided. Drilling holes and pumping holes in
Next, water is injected from the water injection hole to raise the groundwater level in the area surrounded by the water blocking wall to saturate the vicinity of the contaminated soil, and then, while injecting water from the water injection hole, groundwater is discharged from the pumping hole. Pumping the groundwater to generate a groundwater flow from the water injection hole toward the waterhole to transport the contaminants, and then return the groundwater pumped from the waterhole to the waterhole after passing through the pollutant recovery device. It is characterized by.

It is preferable that the depth of the water injection hole is set to a depth equal to or lower than the groundwater level. Further, it is preferable that water is injected under pressure from the water injection hole. Further, it is preferable to add a chemical that promotes separation and elution of the contaminant from the soil to the treated water discharged from the contaminant recovery device.

[0008]

According to the method for purifying contaminated soil according to the present invention, it is possible to saturate the vicinity of contaminated soil by injecting water from a water injection hole and raising the groundwater level in a region surrounded by the water blocking wall. Contaminants can be transported by pumping groundwater from the pumping hole while injecting water from the filling hole to generate a groundwater flow from the filling hole toward the pumping hole. Furthermore, by returning the groundwater pumped from the pumping hole to the water injection hole after passing through the pollutant collecting device, the pollutant can be gradually recovered and the contaminated soil can be gradually cleaned.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, a method for cleaning contaminated soil according to one embodiment of the present invention and a cleaning facility used in the method will be described below.

As shown in FIGS. 1 and 2, the cleaning equipment according to the present embodiment surrounds contaminated soil 2 from the side by a water stop wall 1 constructed to a depth equal to or lower than the groundwater level, A water injection hole 4 and a water pumping hole 5 are excavated in the surrounded area 3. The water injection hole 4 is excavated so as to have a depth equal to or less than the groundwater level, and a packer 6 that partitions the water injection hole 4 up and down is provided in the middle of the water injection hole 4.

A method for cleaning contaminated soil according to this embodiment will be described. That is, water is injected under pressure from a water injection hole 4 by a pressurizing pump (not shown), and as shown in FIG.
Raises the groundwater level in the area 3 surrounded by. Thereby, the vicinity of the contaminated soil 2 can be saturated with the groundwater.

Next, as shown in FIG. 4, groundwater is pumped from the pumping hole 5 while water is injected from the water injection hole 4. As a result, a substantially horizontal groundwater flow from the water injection hole 4 to the pumping hole 5 is generated, and contaminants can be transported by the groundwater flow. Generally, since the horizontal permeability of the soil is larger than the vertical permeability,
, A horizontal groundwater flow to the pumping hole 5 can be effectively generated.

Next, the groundwater pumped from the pumping hole 5 is passed through a pollutant recovery device (not shown), and then returned to the water injection hole 4. The cycle of water injection and pumping is repeated until no contaminants are detected in the pumped groundwater or the pollutants are below the allowable value. In addition, as a contaminant collection | recovery apparatus, the well-known membrane filtration apparatus provided with the reverse osmosis membrane etc. is used, for example.

According to the method for cleaning contaminated soil according to the present embodiment, even when the contaminated soil is deep and widely distributed, the contaminated soil is contaminated by simple devices such as the water stop wall 1, the water injection hole 4 and the pumping hole 5. The soil can be cleaned, and the processing cost can be reduced.

In addition, since the groundwater level in the region 3 surrounded by the water blocking wall 1 is raised by the water injected from the water injection hole 4, the unsaturated zone can be saturated with the groundwater, and therefore, the unsaturated zone can be saturated. Contaminated soil distributed in the saturated zone can be effectively cleaned.

Further, according to the cleaning method of the present embodiment, the installation of the water blocking wall 1 and the installation of the water injection hole 4 for injecting water into the inside area prevent the contamination to the surroundings from expanding. It is possible to purify the contaminated soil while preventing it, and to reduce the influence of the rise and fall of the surrounding water level.

In the above embodiment, water is injected under pressure from the water injection hole 4, but it may be injected spontaneously.

Further, a chemical which promotes separation and elution of the pollutant from the soil may be added to the treated water discharged from the pollutant recovery device. When a low-pH acidic substance is used as the chemical, the negatively charged state of the ground is reduced, cations of heavy metals are easily released from the ground, and further, when powder of ion-exchange resin is used as the chemical. Can directly react with heavy metal ions to separate heavy metals from the ground, and further enhance the ground cleaning effect as compared to the case of simply using a pollutant recovery device as in the above embodiment. be able to.

[0019]

As described above, according to the method for purifying contaminated soil of the present invention, the contaminated soil is surrounded from the side by the water stop wall constructed to a depth equal to or lower than the groundwater level, and the water stop wall is used by the water stop wall. Drilling a water injection hole and a pumping hole in the surrounded area, then injecting water from the water injection hole to raise the groundwater level in the area surrounded by the water blocking wall to saturate the vicinity of the contaminated soil, Pumping groundwater from the pumping hole while injecting water from the filling hole to generate a groundwater flow from the filling hole toward the pumping hole to transport pollutants, and then removing the groundwater pumped from the pumping hole. Since the contaminated material is returned to the water injection hole after passing through the contaminant recovery device, even when the contaminated soil is deep and widely distributed, the contaminated soil can be purified at low cost by a simple device, and , Insatiable It is possible to effectively clean the contaminated soil to be distributed in the band.

[Brief description of the drawings]

FIG. 1 is a plan view showing a cleaning facility used in a method for cleaning contaminated soil according to one embodiment of the present invention.

FIG. 2 is a sectional view of FIG.

FIG. 3 is a sectional view showing a first step of the method for cleaning contaminated soil according to one embodiment of the present invention.

FIG. 4 is a sectional view showing a second step of the method for cleaning contaminated soil according to one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 water blocking wall 2 contaminated soil 3 area surrounded by water blocking wall 4 injection hole 5 pumping hole 6 packer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-228463 (JP, A) JP-A-4-225886 (JP, A) JP-A-52-48202 (JP, A) JP-A-6-28 193040 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) E02D 3/10 B09C 1/04

Claims (4)

(57) [Claims] 1. A water blocking wall constructed up to a depth equal to or lower than a groundwater level, surrounding contaminated soil from the side, excavating a water injection hole and a water pumping hole in an area surrounded by the water blocking wall, Injecting water from the hole to raise the groundwater level in the area surrounded by the water stop wall and saturating the vicinity of the contaminated soil, and then pumping groundwater from the pumping hole while injecting water from the injection hole. Generating a groundwater flow from the injection hole to the pumping hole to transport contaminants,
A method for cleaning contaminated soil, characterized in that groundwater pumped from the pumping hole is returned to the water injection hole after passing through a pollutant recovery device. 2. The method for cleaning contaminated soil according to claim 1, wherein the depth of the water injection hole is set to a depth equal to or less than a groundwater level. 3. The method for cleaning contaminated soil according to claim 1, wherein water is injected under pressure from the water injection hole. 4. The pollutant according to claim 1, wherein a chemical that promotes separation and elution of the pollutant from the soil is added to the treated water discharged from the pollutant recovery device. How to clean the soil.