JPH10290978A - Soil pollution purifying method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soil pollution purifying method capable of sucking and removing pollutants with one piece of suction well and lifting and removing the water accumulated in the suction well with a vacuum pump of a small pump head and a device therefor. SOLUTION: When the water accumulates in a suction well 12 and the ground water level in the suction well 12 attains the upper limit value, a solenoid valve 28 opens and compressed air is supplied from a pressure supplying source 30 to the space between an inside cylindrical pipe 16 and an outside cylindrical pipe 18. The spacing between the inside cylindrical pipe 16 and the outside cylindrical pipe 18 is pressurized by the compressed air to attain the pressure higher than the atm. pressure and the water in the inside cylindrical pipe 16 is lifted by a vacuum pump while the water level therein is kept risen. When the lifting is continued, the ground water level in the suction well 12 falls gradually. When the level of the ground water in the suction well 12 falls down to the lower limit value, the solenoid valve 28 closes and the pressurization by the compressed air from the pressure supplying source 30 is stopped. The polluting gases in the soil are again removed by the suction force of the vacuum pump and the vacuum extraction is restarted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for remediating soil pollution, and more particularly to a method for removing harmful substances such as trichloroethylene, tetrachloroethylene, 1,1, 1-trichloroethane from soil contaminated by industrial waste. The present invention relates to a method and an apparatus for purifying soil pollution by removing a volatile organic chlorine compound by suction by a vacuum extraction method.

[0002]

2. Description of the Related Art Contaminants of volatile organochlorine compounds exist in the soil and groundwater as a gas phase or a liquid phase. Therefore, a vacuum extraction method is used to remove volatile contaminants present in soil. The vacuum extraction method involves drilling a suction well from the ground surface to a contaminated area in the soil, and using a vacuum pump to remove air, contaminant vapor, water vapor,
The contaminated groundwater and the like are suctioned and removed in the state of a gas-liquid mixed flow through the suction well.

[0003] The operation efficiency of the vacuum extraction method depends on the nature of the soil around the suction well due to the nature of sucking volatile contaminants in the soil. Among the properties of soil, air permeability is a major factor that determines work efficiency. That is, when contaminants are suctioned and removed by the vacuum pump, moisture and groundwater in the soil are sucked, and water accumulates in and around the suction well. As a result, the air permeability deteriorates and contaminants are hardly sucked, so that the working efficiency is reduced. Therefore, if water accumulates in or around the suction well and the air permeability deteriorates, it is necessary to remove the accumulated water by a vacuum pump.

However, since a vacuum pump for sucking a gas-liquid mixed phase of volatile sludge is used at most with a lift of about 10 m at most, the depth of water accumulated in the suction well is limited by the vacuum pump. In the case where the head is not less than the head, it is impossible to pump water only by the vacuum pump. For this reason, conventionally, a large vacuum pump is installed, and when water accumulates in the suction well, the load on the vacuum pump is increased to pump water, and after the water is removed by suction and the air permeability is improved, the vacuum pump is In order to increase the work efficiency, the degree of vacuum and the displacement of the vacuum pump were changed according to the conditions in the soil, such as reducing the load on the soil.

[0005]

However, since a large-sized vacuum pump is installed, there is a drawback that the equipment becomes large-sized, which is not preferable in terms of work efficiency.
The present invention has been made in view of the above circumstances, and
It is an object of the present invention to provide a soil contamination purification method and apparatus capable of sucking and removing contaminants in a suction well and pumping and removing water accumulated in the suction well with a vacuum pump having a small head.

[0006]

According to the present invention, in order to achieve the above object, a suction well is drilled in soil contaminated with volatile contaminants, and the contaminants are sucked through the suction well. In the method for removing soil pollution, the suction well is formed in a double pipe structure, the contaminants are removed by suction from one of the double pipes, and water in soil is stored in the suction well. When water accumulates, compressed air is supplied to the other pipe to pump up and remove water accumulated in the suction well.

According to the present invention, in order to achieve the above object, a suction well is drilled in soil contaminated with volatile contaminants, and the contaminants are suctioned and removed through the suction well by a vacuum pump. The above-mentioned suction well is formed in a double pipe structure, and a compressed air supply device for supplying compressed air to one of the double pipes is provided.

According to the present invention, when water in the soil accumulates in the suction well, the water is sucked from one of the double pipes by a vacuum pump, and compressed air is supplied to the other pipe. Since the accumulated water is removed by pumping, a water pump having a depth higher than the head can be suctioned and removed by a vacuum pump having a small head.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the method and apparatus for purifying soil pollution according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing the overall configuration of the soil pollution purification device of the present invention. Soil pollution purification device 10
In the case, the suction well 12 is excavated in the soil which is the contaminated area. The suction well 12 includes a gas-liquid separation tank 13 and a vacuum pump 1 in this order.
5 is connected. Thereby, the vacuum pump 1
5 generates a suction effect and sucks contaminants in the soil. A processing tank 17 is provided downstream of the vacuum pump 15,
The suctioned contaminants are purified by being adsorbed on activated carbon or the like or decomposed by a method such as thermal decomposition. The gas purified after passing through the processing tank 17 is discharged to the atmosphere via an exhaust pipe 19.

FIG. 2 is a sectional view for explaining a suction well. As shown in FIG. 2, the suction well 12 is formed in a double pipe structure of an inner tube 16 and an outer tube 18, and a lid 14 is provided at an upper end of the suction well 12 located on the ground surface.
The depth of the suction well 12 is usually 10 m or more, and the inner tube 1
6 having a diameter of 15A and an outer tube 18 having a diameter of 50A are generally used. The head of the vacuum pump 15 used for suction is usually 10 m, and the suction amount is 600 m.
Those of about l / h are generally used. A strainer 20 is provided at the lower end of the outer tube 18 to take in contaminants in the soil into the suction well 12 from this portion and prevent solids such as soil from entering. The inner tube 16 has an opening at the lower end and is formed to have a length that does not contact the bottom of the outer tube 18.

The upper end of the inner tube 16 extends to the ground through the lid 14 and is connected to a vacuum pump 15 (see FIG. 1). A tip of an air pipe 26 is inserted through the lid 14 between the inner pipe 16 and the outer pipe 18 of the suction well 12, and the air pipe 26 is connected to an electromagnetic valve 28 on the ground side. . The electromagnetic valve 28 is connected to a pressure supply source 30, and when the electromagnetic valve 28 is opened, compressed air from the pressure supply source 30 connects the inner tube 16 and the outer tube 18 of the suction well 12 via the air pipe 26. Supplied in between. The opening and closing of the electromagnetic valve 28 is controlled by a signal from the level switch 24.

The lower end of the suction well 12 has an inner cylindrical tube 16.
A needle-type water level gauge 22 is provided between the outer tube 18 and the outer tube 18. The needle-type water level gauge 22 measures the level of groundwater accumulated in the suction well 12, and the measured value is sent to the level switch 24 via the signal cable 25. The lower limit value and the upper limit value of the groundwater level are stored in the level switch 24 in advance, and the measured value is compared with the lower limit value and the upper limit value.

Next, the operation of the soil pollution purifying apparatus configured as described above will be described. By this suction removal, groundwater in the soil accumulates around and inside the suction well 12. The accumulated water impedes the ventilation of the strainer 20 and lowers the efficiency of suction and removal of contaminants. Therefore, when water accumulates in the suction well 12, it is removed as follows. The level of groundwater in the suction well 12 is
It is measured by a needle type water level meter 22. When the groundwater level in the suction well 12 reaches the upper limit, the electromagnetic valve 28 is opened, and compressed air is supplied from the pressure supply source 30 to the space between the inner tube 16 and the outer tube 18. Thereby, the inner cylinder 1
The space between the outer tube 6 and the outer tube 18 is pressurized by compressed air to a pressure higher than the atmospheric pressure, and is pumped by the vacuum pump 15 while the water level in the inner tube 16 rises.

For example, as a control for opening and closing the electromagnetic valve 28 when pumping water, pressurization is performed for 30 seconds,
It is advisable to perform intermittent pressurization control so that groundwater is sucked for 10 minutes after closing 8. Therefore, for example, suction well 1
Water can be pumped even if the depth of the water accumulated in the tank 2 is not less than the head of the vacuum pump 15.

As the pumping is continued, the groundwater level in the suction well 12 gradually decreases. When the level of the groundwater in the suction well 12 drops to the lower limit, the electromagnetic valve 28 is closed, the pressurization by the compressed air from the pressure supply source 30 is stopped, and the pollutant gas in the soil is again sucked by the vacuum pump 15. And the vacuum extraction is resumed. As described above, by repeatedly opening and closing the electromagnetic valve 28 at the upper and lower limits of the groundwater level, pumping and vacuum extraction are alternately performed, and the groundwater and contaminated gas in the soil can be suctioned and removed.

Further, since the suction well 12 has a double pipe structure and the needle-type water level gauge 22 is provided between the inner pipe 16 and the outer pipe 18, the inside of the inner pipe 16 is maintained even when the vacuum pump 15 is operating. It is not affected by the turbulence of the water surface that occurs. Therefore, the water level of the groundwater can be accurately measured. still,
In the present embodiment, the depth of the suction well 12 is
Although the case where the head is 5 m or more was explained,
When it is within 10 m, the groundwater in the soil rises as a gas-liquid mixed flow in the inner tube 16 by the suction force of the vacuum pump 15 together with the pollutant gas, and is pumped to the ground.

In the above-described embodiment, the needle-type water level gauge 22 is used to measure the groundwater level. However, the present invention is not limited to this, and a float type water level gauge may be used. Further, although the needle-type water level gauge 22 is provided between the inner pipe 16 and the outer pipe 18, it may be provided inside the inner pipe 16.

[0018]

According to the present invention, when water collected in a suction well is pumped by a vacuum pump, the pumping is performed while supplying compressed air to the suction well. Can be pumped. As a result, water with a depth higher than the head can be pumped and removed by a vacuum pump having a small head that can pump water with one suction well and can remove volatile contaminants by suction.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the overall configuration of a soil contamination purification device of the present invention.

FIG. 2 is a cross-sectional view illustrating a suction well.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Soil pollution purification apparatus 12 ... Suction well 16 ... Inner cylinder pipe 18 ... Outer cylinder pipe 20 ... Strainer 22 ... Needle type water level gauge 24 ... Level switch 28 ... Electromagnetic valve 30 ... Pressure supply source

Continued on the front page (72) Inventor Masahiro Shimazu 1-1-1 Uchikanda, Chiyoda-ku, Tokyo Inside Hitachi Plant Construction Co., Ltd.

Claims (4)

[Claims] 1. A soil contamination purification method in which a suction well is excavated in soil contaminated with volatile contaminants, and the contaminants are removed by suction through the suction wells. The suction pipe removes the contaminants by suction from one of the double pipes, and sends compressed air to the other pipe when water in the soil accumulates in the suction well. And a method of purifying soil contamination, wherein water collected in the suction well is removed by pumping. 2. The soil according to claim 1, wherein the level of water accumulated in the suction well is measured, and compressed air is intermittently supplied to the other pipe according to the measured value. Pollution purification method. 3. A soil contamination purification apparatus for digging a suction well in soil contaminated with volatile contaminants and sucking and removing said contaminants through said suction well by a vacuum pump. A soil contamination purifying apparatus, which is formed in a double pipe structure, and provided with a compressed air supply device for supplying compressed air to one of the double pipes. 4. The soil pollution purifying apparatus according to claim 3, wherein a water level meter for measuring a water level of water accumulated in the suction well is provided in one of the double pipes.