JP2000084535A - Method of cleaning contaminated soil by volatile compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of cleaning contaminated soil by a volatile compound which is able to efficiently cleaning it in a short time. SOLUTION: A contaminated material in the soil is removed by inserting electrodes 4 at a certain interval into soil contaminated by the contaminated material composed of a volatile compound, impressing a voltage between the electrodes to pass a current through water in the contaminated soil 1 and generating steam by the generated Joule's heat to elute the contaminated material in the soil into the steam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to, for example, dichloromethane, carbon tetrachloride, 1,2-dichloromethane, 1,1
-Organic chlorine-based drugs such as dichloroethylene, cis-1,2-dichloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene, and tetrachloroethylene; and aromatic drugs such as benzene, xylene, and toluene. A method for purifying contaminated soil with volatile compounds.

[0002]

2. Description of the Related Art Conventionally, a method of purifying soil contaminated with volatile compounds of this type involves a method of removing soil gas by moving water or air in the contaminated ground to separate the pollutants eluted therefrom. And the groundwater positive water law.

[0003] In addition, there is a method in which quick lime is injected into the ground, steam is generated by the heat generated, and contaminants are eluted therefrom.

[0004]

Of these conventional methods, the soil gas suction method and the groundwater positive water method only suck and remove water and air from the ground. There is a problem that the road can be made, the purification efficiency is low, and the decontamination takes a long time of several to ten years,
In the method using the heat generated by quicklime, it is necessary to excavate the ground to supply a required amount of quicklime into the soil, and there is a problem that the cost is too high when the pollution is wide.

The present invention has been made in view of such conventional problems, and has as its object to provide a method for purifying contaminated soil with a volatile compound, which can be efficiently purified in a short period of time.

[0006]

SUMMARY OF THE INVENTION The features of the present invention for solving the conventional problems as described above and achieving the intended purpose are as follows.
Electrodes are inserted at intervals into soil contaminated with volatile compounds, and a voltage is applied between the electrodes to energize water in the soil. And removing the contaminant by eluting the contaminant in the water vapor.

[0007] It is to be noted that a vertical ventilation hole is provided in the contaminated ground to energize it, that the contaminated ground is surrounded by a water impervious wall, and that the soil is surrounded by the water impervious wall at intervals. It is preferable to insert an electrode, and it is also possible to provide a vertically-oriented electrode integrally with a part of the impermeable wall and to conduct electricity to the electrode.

Further, current is supplied to the ground surrounded by the impermeable wall by changing the groundwater level by injecting water into the ground, and the ground surrounded by the impermeable wall is disturbed by a civil engineering machine such as an auger to improve air permeability. It is preferable to energize in a state where is promoted, and to energize by using a large number of electrodes and changing the electrodes to be energized.

[0009]

Embodiments of the present invention will now be described with reference to the drawings.

FIGS. 1 and 2 show a first embodiment of the present invention. In the purification process, first, the area to be purified, that is, the ground 1 to be treated is surrounded by a continuous impermeable wall 2. The impermeable wall 2 is a continuous underground wall constructed by driving steel or concrete sheet pile into the impermeable layer 3 underground. In addition, a continuous underground wall made of cast-in-place concrete may be used.

Along the inside of the water-impervious wall 2 constructed in this manner, a number of electrodes 4, 4... Are driven vertically at a predetermined interval to a required purification processing depth, and power is supplied to each electrode 4. Conductor 5 for wiring.

In parallel with this, one or a plurality of ventilation holes 6 and pumping wells 7 are formed vertically in the ground 1 to be treated, and a submersible pump 8 is inserted into each pumping well 7 and a pumping and draining pipe is provided. 9 and the injection pump 10 are communicated.

After the electrodes 4, the ventilation holes 6 and the pouring / draining wells 7 have been installed in this way, the upper part of the ground to be treated, including the upper part of the impermeable wall 2, is covered with an impermeable hood 11, and the inside of the hood 11 is connected to the gas. The processing equipment 12 is communicated with the ventilation pipe 13.

Next, one or more of the electrodes 4, 4... Are selected and energized to energize the water in the ground to be treated. This energization generates Joule heat and heats water to generate steam. At this time, the water in the ground to be treated is brought into a boiling state in the soil, so that the vapor uniformly contacts the particles in the soil, and the volatile compound is eluted into the vapor. The steam generated in this way is guided to the ground through the ventilation holes 6 and introduced into the processing equipment 12 from inside the hood 11, where the pollutants are separated and released to the atmosphere.

When energizing the electrodes 4, 4,..., As shown in FIG. 2, for example, as shown in FIG. Is controlled so that the amount of current supplied per hour is constant, and the water in the ground is uniformly heated while preventing local heat.

When heating is performed by applying electricity to water in the soil to generate Joule heat, the solubility of the electrolyte increases and the electrical conductivity decreases. For this reason, the electricity charge in the portion where the temperature has risen increases, and local heat occurs in which the temperature further rises. To prevent this, measure the amount of electricity,
Heat is generated in a well-balanced manner while selecting the position and number of electrodes to be energized.

When the groundwater level is high, water is pumped from the pumping well 7 and the groundwater level is lowered to below the contaminated ground. The groundwater level a of the ground 1 is sequentially raised. As a result, the surface where the steam is generated sequentially rises, and the contact of the steam is made evenly in the vertical ground.

Next, a second embodiment of the present invention will be described with reference to FIGS.
Will be described. Note that the same parts as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, as shown in FIG. 4, after the ground 1 to be treated is surrounded by the impermeable wall 2, the auger 14 is sequentially screwed into the whole ground inside to disturb the soil, thereby increasing the air content. The disturbance of the soil is carried out by using a suitable earthmoving machine according to the depth of the contaminated ground, and a backhoe other than the auger and other excavating machines can be used.

After the soil is thus disturbed to improve gas permeability, as shown in FIG. 3, a pumping well 7 is installed and electrodes 4, 4,... Are installed in the same manner as described above. The upper surface of the ground 1 to be treated whose volume has been increased by the disturbance is covered with the air-impermeable sheet 15 and energized in the same manner as described above.
The groundwater is boiled by Joule heat and treated by passing the generated water vapor through the soil.

After completion of the treatment with steam in this way,
When the upper surface is left covered with the air-impermeable sheet 15, the ground becomes a vacuum state due to a decrease in temperature, and the ground returns to the original consolidation state or a state close to the original consolidation state by the vacuum pressure.

At this time, the inner surface of the air-impermeable sheet 15 and the ground 1 to be treated are previously provided with a ventilation passage 1 made of a drain material or the like.
6 in advance, and after treatment with steam,
By reducing the pressure in the vacuum pump 6 with a vacuum pump 17, the consolidation by vacuum can be performed more completely, and the water in the soil evaporates to remove latent heat. Can be.

In each of the above embodiments, the electrode is inserted inside the impermeable wall. However, as shown in FIG. 5, a conductive electrode 4 is integrally provided on a part of the impermeable wall 2. Alternatively, the electrodes may be installed simultaneously with the construction of the impermeable wall.
In addition, it is preferable that the surface of the impermeable wall other than the part used as an electrode is covered with a substance having lower electric conductivity than water.

[0023]

As described above, in the method for purifying soil contaminated with a volatile compound according to the present invention, electrodes are inserted at intervals into soil contaminated with a contaminant composed of a volatile compound. By applying a voltage between the electrodes to energize the water in the soil, and generating Joule heat by the Joule heat generated by the energization to elute the contaminants in the water vapor, the contaminants are volatilized. Is performed quickly and efficiently, and highly efficient purification of contaminated soil can be performed in a short period of time.

Further, in the steam purification treatment, by providing a vertical ventilation hole in the contaminated soil ground, the steam generated during the treatment can be quickly discharged.

Furthermore, the ground contaminated with a pollutant composed of a volatile compound is surrounded by a water impervious wall, and electrodes are inserted into the soil surrounded by the water impervious wall at intervals to perform a treatment. , Without affecting the surrounding ground,
Energy efficiency can be increased, the water level can be set arbitrarily, and the contaminated portion can be efficiently brought into contact with water vapor.

Furthermore, by applying water while injecting water into the ground surrounded by the impermeable wall and changing the groundwater level, the processing portion can be controlled up and down, and uniform processing can be performed in the up and down direction. .

Furthermore, by energizing the ground surrounded by the impermeable walls by increasing the air permeability by disturbing the ground with an earth-moving machine such as an auger, the contact between the water vapor and the soil particles is made uniform, Purification efficiency is improved.

By using a large number of electrodes and changing the electrodes to be energized to energize water in the ground, uniform processing can be performed without causing local heat.

Further, by forming the electrode by using a part of the impermeable wall as a conductive material, the electrode can be installed simultaneously with the construction of the impermeable wall, and the working efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the method of the present invention.

FIG. 2 is a plan view showing the above-described electrode energized state.

FIG. 3 is a sectional view showing a second embodiment of the method of the present invention.

FIG. 4 is a cross-sectional view showing an initial step of the same.

FIG. 5 is a partial perspective view showing an example of a water impermeable wall and electrodes used in the present invention.

[Explanation of symbols]

 Reference Signs List 1 ground to be treated 2 impermeable wall 3 impermeable layer 4 electrode 5 conducting wire 6 vent hole 7 pumping well 8 submersible pump 9 pouring drain pipe 10 pouring pump 11 hood 12 gas treatment facility 13 vent pipe 14 auger 15 impervious sheet 16 Ventilation path 17 Vacuum pump

Claims (7)

[Claims] 1. An electrode is inserted into a soil contaminated with a pollutant composed of a volatile compound at an interval, and a voltage is applied between the electrodes to energize water in the soil. A method for purifying contaminated soil with a volatile compound, characterized in that steam is generated by Joule heat, and the contaminant is removed by eluting the steam into the steam. 2. The method for purifying contaminated soil with a volatile compound according to claim 1, wherein a current is supplied by providing a vertical ventilation hole in the contaminated ground. 3. The method according to claim 1, wherein the ground contaminated with a pollutant composed of a volatile compound is surrounded by a water impervious wall, and electrodes are inserted into the soil surrounded by the water impervious wall at intervals. A method for purifying contaminated soil with the volatile compound described in the above. 4. A vertically oriented electrode is provided integrally on a part of the impermeable wall,
The method for purifying contaminated soil with a volatile compound according to claim 1 or 2, wherein the electrode is energized. 5. The method for purifying contaminated soil by a volatile compound according to claim 2, wherein electricity is supplied into the ground surrounded by the impermeable wall to change the groundwater level, and energization is performed. 6. Contamination by a volatile compound according to claim 3, 4 or 5, wherein the ground surrounded by the impermeable wall is energized while the air permeability is enhanced by disturbing the ground with an earth-moving machine such as an auger. How to clean the soil. 7. The method for purifying contaminated soil by a volatile compound according to claim 1, wherein a large number of electrodes are used, and a current is supplied by changing an electrode to be supplied with electricity.