JP2002035736A - Treatment device for contaminated soil and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and efficiently treat contaminated soil at a low cost on the spot without removing it to another place by applying the effects of electroosmosis and electrophoresis. SOLUTION: This treatment device comprises a portable container 2 that stores contaminated soil 1, a water-permeable upper electrode 3 installed in the outer layer of the contaminated soil 1, a sheet-like lower electrode 4 installed under the container 2, a DC power supply 5 that applies DC voltage between the upper electrode 3 and the lower electrode 4, a water spray device 8 that sprays water into the container 2 and a water supply device 6, and a wastewater treating device 9 that is connected through a drain valve 7. Wide and uniform voltage is added by a pair of sheet-like positive and negative electrodes to apply the wide and uniform effects of electroosmosis and electrophoresis to the contaminated soil, thereby realizing uniform decontamination. Vertical arrangement of the electrodes allows the use of buoyancy and gravity, thereby realizing efficient treatment. The treatment can be carried out on the contamination spot by using the portable container.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus and a method for treating contaminated soil, and more particularly to an apparatus and a method for removing contaminants from soil contaminated with heavy metals and the like.

[0002]

2. Description of the Related Art The problem of contaminated soil has been highlighted in recent years. The problem of contaminated soil originates in agricultural land pollution, such as copper contamination, cadmium contamination and arsenic contamination from mines.

On the other hand, with the development of industry, heavy metals (mercury, cadmium, arsenic,
(Valent chromium) and volatile organic compounds such as trichloroethylene. In addition, problems have arisen in agricultural lands such as eutrophication such as over-nitrogenation and over-neighboring due to spraying of pesticides for many years, and residual of chemicals for pest control and prevention.

Conventionally, the processing method differs depending on the contaminants and the state of contamination, but the following processing methods are available.
There are a method of removing contaminated soil to a waste disposal site and replacing with soil, a method of removing and backfilling pollutants by incineration of contaminated soil, and a method of fixing contaminated soil to prevent its spread.

[0005] The method of carrying out contaminated soil to a waste disposal site and replacing it with a piece of soil requires a large-scale construction and a great deal of cost. In addition, when the contaminated soil is carried out, the contaminated soil may scatter and expand.

In the method of removing and backfilling contaminants by incineration of contaminated soil or the like, a large amount of incineration energy is required for treatment, and a large cost is required. In the method of fixing to prevent the spread of pollution, there is a problem that the reuse of land is difficult because the pollution is not essentially eliminated.

[0007] In the farmland, 70 to 70
Digging 80cm and replacing the surface 30-40cm with the lower 40-80cm, we were able to survive. This method is possible only once, and even if the surface layer is replaced again, only the old soil will come out, and large-scale construction such as replacing the surface soil with new soil is required. There's a problem.

[0008]

As described above, in order to avoid large-scale construction and energy costs associated with soil replacement, etc., electrokinetic effects, that is, effects of electroosmosis and electrophoresis, are contaminated. There are methods applicable to soil treatment.

The principle of purification treatment of contaminated soil by electroosmosis and electrophoresis is described in the literature "Tadaaki Seno et al., In-situ electrokinetic soil purification method, resource treatment technology, Vol. 44, No. 4, 206-
212, (1997).

Electrokinetically, the soil particle surface is negatively charged. As a result, an electric double layer is formed near the soil particle surface, and positively charged ions maintain electrical neutrality. Come together for. When an electric field is formed there, the fluid in this region will flow toward the cathode. Fluid away from the soil particle surface is also induced to viscous and flows in the same direction.

This phenomenon is called an electroosmosis phenomenon.
In addition, since the ionized substances have positive or negative polarities, they are attracted to electrodes having opposite characteristics in an electric field. This is the effect of electrophoresis.
The purification treatment of contaminated soil by electroosmosis or electrophoresis has the advantage of treating contaminated soil in situ.

A rod-like electrode is inserted vertically into such contaminated soil, and the inserted rod-like electrode is made hollow, for example.
Methods of supplying and collecting water are disclosed in Japanese Patent Nos. 2132617 and 2715263. Japanese Patent No. 2853797 discloses a method in which contaminated soil is put into a container and the contaminated soil is purified using the effects of electrophoresis and electroosmosis.

However, in any of the above-described methods, since a rod-shaped electrode is used, a uniform electric field cannot be obtained, and the effects of electrophoresis and electroosmosis are not uniform, so that the degree of purification of contaminated soil to be treated is stable. There was a problem not to do.

The object of the present invention is to solve the above problems and to apply the effects of electroosmosis and electrophoresis, to carry out contaminated soil at low cost without taking it out to other places, to perform construction easily and efficiently. It is an object of the present invention to provide an apparatus and a method for treating contaminated soil.

[0015]

The object of the present invention is to provide a container for charging contaminated soil, a sheet-like first electrode provided at a lower portion of the container and for charging and loading the contaminated soil thereon.
A sheet-like electrode covering the surface of the contaminated soil stacked on the first electrode, and a power supply device connected to the two electrodes, wherein a voltage is applied between the two electrodes to treat the contaminated soil. This can be achieved by using a soil treatment device.

[0016] Further, contaminated soil is laminated on the first electrode, a second electrode is provided on the surface of the contaminated soil, moisture is applied to the contaminated soil, and the first electrode and the second electrode are disposed. Applying a voltage between the electrodes, of the at least one or more components to be treated in the contaminated soil, the components to be treated having a charge opposite to the polarity of the first electrode is moved to around the first electrode, The component to be treated having a charge opposite to the polarity of the second electrode is moved to the vicinity of the second electrode, and the component to be treated moved to the periphery of the first electrode is supplied to the contaminated soil with moisture. It can be achieved by a method for treating contaminated soil that is collected and treated together.

By arbitrarily switching the polarity of the electrode, the component to be treated having a positive or negative charge can be arbitrarily moved to the periphery of the electrode. Therefore, by giving a slope to the sheet-like electrode on the lower surface and imparting moisture to the contaminated soil, the component to be treated having either a positive or negative charge can be discharged from the electrode on the lower surface together with the moisture. .

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an apparatus for treating contaminated soil according to the first embodiment.

The treatment apparatus comprises a portable container 2 for storing contaminated soil 1, a permeable upper electrode 3 installed on the surface of the contaminated soil 1, and a sheet-like lower electrode 4 installed below the container 2. A DC power supply 5 for applying a DC voltage between the upper electrode 3 and the lower electrode 4; a watering device 8 for watering the container 2; a water supply device 6 for supplying water to the watering device 8; A drainage treatment device 9 connected via a drainage valve 7;

The lower part of the container 2 is inclined or installed at an angle, and a drain pipe is installed at the lower side of the inclination and a drain valve 7 is provided to discharge waste water containing pollutants.
The container 2 has a rectangular parallelepiped shape with an open top, and can be carried by a vehicle or the like together with the water supply device 6, the DC power supply 5, the wastewater treatment device 9, and the like.

By making the container 2 a portable container and integrating it with a wastewater treatment device 9, a water supply device 6, a DC power supply 5, etc., it is possible to treat the soil at the site of contaminated soil. Can be prevented from spreading.

In addition to the shape of the container shown in the present embodiment, a sheet-like lower electrode 4 which is substantially filled with contaminated soil and spreads below the container 2 and an upper portion which covers the surface layer of the contaminated soil 1 are used. Any shape and size can be used as long as the electrode 3 can be laid.

The upper electrode 3 installed at the upper part of the container is a conductive sheet widely covering the surface layer of the contaminated soil, and the lower electrode 4 installed at the lower part of the container and loaded with the contaminated soil widely covers the lower part of the container. An iron plate, a conductive sheet, or the like is used.

The upper electrode 3 and the lower electrode 4 are connected to a negative terminal and a positive terminal of a DC power supply 5, respectively, and
Has a function as a negative electrode and a positive electrode, respectively, so that a voltage is applied to the contaminants in the contaminated soil 1 to cause the effects of electroosmosis and electrophoresis. By using the effects of electroosmosis and electrophoresis, inexpensive treatment such as heat treatment that does not require high energy can be performed.

Further, in order to make the effect of electroosmosis and electrophoresis work, it is necessary to raise the water content of the soil as much as possible. It has the function of preventing evaporation and keeping the water content high.

As the negative electrode and the positive electrode connected to the DC power supply 5, the upper electrode 3 and the lower electrode 4 are both arranged in a planar shape and are arranged so as to be opposed to the upper and lower sides of the contaminated soil 1. In contrast, a wide and uniform electric field can be provided.

In addition to the effects of electroosmosis and electrophoresis,
Since the effects of buoyancy and gravity can also be used, inexpensive and efficient operation is achieved. That is, among the pollutants, substances having a low specific gravity have buoyancy acting to float on the soil surface, and substances having a high specific gravity have gravity acting to settle under the soil.

Since the direction of buoyancy and gravity acting on these contaminants coincides with the direction of electroosmosis and electrophoresis, the effect of accumulating contaminants near the upper and lower electrodes, respectively, is enhanced.

The water supply device 6 has a function of supplying water to the contaminated soil 1 in the container via the water spray device 8. Contaminated soil 1
In the water supply method for imparting moisture to the sheet, the sheet-shaped upper electrode 3 is provided with water permeability, and water is sprayed from above the upper electrode 3 by the water spray device 8.

Any method can be used as long as it can substantially impart moisture to the contaminated soil. For example, a sheet electrode in which a pipe is stretched around a sheet electrode and water is sprayed from an opening of the pipe may be used. The DC power supply 5 supplies a DC voltage between the upper electrode 3 and the lower electrode 4.

The wastewater treatment device 9 is a device for recovering the pollutants eluted in the wastewater in accordance with the effects of electroosmosis and electrophoresis. It is configured using an activated carbon adsorption tower, an electroosmosis membrane recovery device, and the like.

In this embodiment, an example of a portable device that can be transported by a vehicle such as a truck has been described from the viewpoint of preventing the spread of contamination due to the removal of contaminated soil. Is also good.

The procedure for purifying contaminated soil using the treatment apparatus is as follows. Put the contaminated soil in container 2.
The upper electrode 3 is installed on the surface layer of the contaminated soil 1, water is injected from a water supply device 6 through a sprinkler device 8, and the contaminated soil put in the container 2 is filled with water.

Next, a DC voltage is applied between the upper and lower electrodes 3 and 4 by using a DC power supply device. As a result, the effects of electroosmosis and electrophoresis act on the contaminants in the contaminated soil 1, whereby the negatively charged contaminants move around the lower electrode and the positively charged substances move around the upper electrode. Moving.

Next, the drain valve 7 at the bottom of the container 2 is opened,
The pore water of the soil containing the negatively charged contaminants is collected in the wastewater treatment device 9 and subjected to wastewater treatment. The amount of contaminants in the collected wastewater is monitored, and the above steps are repeated until the contaminant concentration falls below the target value.

When the concentration of the contaminants becomes equal to or lower than the target value, the soil of the cleaned container 2 is taken out, and if there is another contaminated soil to be cleaned, the same operation is continued.

Here, the polarity of the upper electrode 3 and the lower electrode 4 may be appropriately switched according to the polarity of the charge of the main pollutant to be purified. That is, if the contaminants to be recovered in the wastewater have negative charges,
If the upper electrode is negative and the lower electrode is positive, and the contaminants to be collected in the wastewater have a positive charge, the upper electrode may be positive and the lower electrode may be negative.

Next, some other embodiments of the present invention will be described. Various materials and forms are conceivable for the upper electrode 3 and the lower electrode 4 in the above embodiment, as shown in FIG.

For example, as shown in FIG. 2A, a punching plate 11 in which a large number of holes 10 are formed, FIG.
As shown in FIG. 2C, a wire mesh 12 as shown in FIG. 2B and a fibrous sheet 13 having conductivity such as carbon. What is important is to be electrically conductive, to be formed in a planar shape, and to have water permeability.

The water permeability of the upper electrode is not always essential. For example, as shown in the plan view of FIG. 3A and the side view of FIG. 3B, a watering pipe 15 provided with a large number of openings and a sheet-like upper electrode 3a having no water permeability.
May be combined.

In this case, as shown in the side view of FIG.
Therefore, the upper electrode 3a only needs to be conductive and formed in a planar shape.

In the embodiment shown in FIG. 1, the water supply method for the contaminated soil is one in which water is uniformly sprayed from the upper portion of the water-permeable upper electrode 3 to the entire surface of the container by the water spraying device 8, but the gap around the container is used. For example, as shown in FIG. 5, it is possible to function simply by providing a faucet 18 for supplying water to a container.

As described above, according to the embodiment of the present invention, by using a planar positive / negative electrode pair, a wide and uniform voltage is applied to effect the effects of electroosmosis and electrophoresis on contaminated soil. It can be applied uniformly over a wide area, and uniform purification of contamination can be achieved.

By arranging the electrodes vertically,
Since the effects of buoyancy and gravity can be used in addition to the effects of electroosmosis and electrophoresis, efficient processing is possible. Therefore, by inclining the lower electrode, imparting moisture to the contaminated soil, and arbitrarily switching the polarity of the electrode, any component having a positive or negative charge can be arbitrarily discharged together with the moisture from the lower electrode. It is possible to do.

In addition, by providing a portable container and integrating it with a water supply device, a wastewater treatment device, a power supply device, and the like, it is possible to provide a device capable of treating contaminated soil at a contaminated site without carrying it to another place. it can.

[0046]

As described above, according to the present invention,
By applying the effects of electroosmosis and electrophoresis, the contaminated soil can be processed at low cost without taking the contaminated soil to another place, and the contaminated soil can be processed easily and efficiently.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a contaminated soil treatment apparatus of the present invention.

FIG. 2 is a top view showing some examples of a water-permeable sheet-like electrode in the present invention.

FIG. 3 shows an example of a watering pipe according to the present invention;
(A) is a plan view and (B) is a side view.

FIGS. 4A and 4B show an example of a sprinkling pipe according to the present invention, wherein FIG. 4A is a side view and FIG.

FIG. 5 is a diagram showing a watering method using a water supply faucet according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Contaminated soil 2 Container 3 Upper electrode 4 Lower electrode 5 DC power supply 6 Water supply device 7 Drain valve 8 Watering device 9 Wastewater treatment device 10 Hole 11 Punching plate 12 Wire mesh 13 Conductive fibrous sheet 15 Watering pipe 16 Watering small hole 18 Faucet

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 35/06 T (72) Inventor Noriyuki Oyatsu 3-36 Takara-cho, Kure-shi, Hiroshima Babcock-Hitachi Kure Kenkyu (72) Inventor Goro Shuto 6-2-1, Sagimiya, Nakano-ku, Tokyo F-term (reference) 2D043 CA20 2E191 BA02 BB01 BD00 4D004 AA41 AB03 AC05 AC07 CA12 CA44 CA47 CA50 CB03 CB05 CB43 CB50 CC03 DA02 DA20 4D054 FA08 FB02

Claims (7)

[Claims] 1. A container for accommodating contaminated soil, a sheet-like first electrode installed below the container and carrying the contaminated soil, and a sheet-like electrode installed on the surface of the contaminated soil on the first electrode. An apparatus for treating contaminated soil, comprising: a sheet-like second electrode; and a power supply for applying a voltage between the first electrode and the second electrode. 2. An apparatus for treating contaminated soil according to claim 1, further comprising a water supply means for supplying water to said contaminated soil. 3. A wastewater treatment means for collecting and treating the water given to the contaminated soil out of the container.
Or the apparatus for treating contaminated soil according to 2. 4. A method according to claim 1, further comprising:
The apparatus for treating contaminated soil according to claim 1, further comprising a wastewater treatment unit that collects and treats the component to be treated in the contaminated soil outside the container. 5. A planar electrode is provided on an upper surface and a lower surface of a contaminated soil, water is applied to the contaminated soil to apply a voltage between the upper and lower electrodes, and a component to be treated in the contaminated soil is applied to the electrode. A method for treating contaminated soil, wherein the contaminated soil is moved to the periphery of the soil and the component to be treated is collected and treated together with the water. 6. A method according to claim 6, further comprising: installing a planar first electrode at a lower portion of the container, loading a contaminated soil on the first electrode, and installing a second electrode on an upper surface of the contaminated soil. Moisture is applied to the soil, a voltage is applied between the first electrode and the second electrode, and at least one or more components to be treated in the contaminated soil have the polarity of the first electrode. A component to be processed having an opposite charge is moved to the vicinity of the first electrode, and
The component to be treated having a charge opposite to the polarity of the
The method for treating contaminated soil, wherein the contaminated soil is moved around the first electrode and the component to be treated moved around the first electrode is collected and treated together with the water. 7. The method for treating contaminated soil according to claim 5, wherein the polarity of the electrode is arbitrarily switched to move a component to be treated having a charge opposite to the polarity to the periphery of the electrode.