JPH10192834A - Soil pollution cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soil pollution cleaning method for enabling the sensing of the water level position of underground water even during the suction operation. SOLUTION: A suction well 22 is constituted of an outer cylinder pipe 24 provided with a strainer 26 at the end and an inner cylinder pipe 28 to be inserted into the outer cylinder pipe 24. A gas-liquid separation tank and a vacuum pump are connected with the ground surface of the inner cylinder pipe 28, while an end opening 28A is formed in the vicinity of the strainer 26. A floating type water level indicator for sensing the water level position of underground water 29 is set between the inner cylinder pipe 28 and the outer cylinder 24. In a cleaning device 20 of the above-referred constitution, gas phases and liquid phases containing pollutants are introduced from the end opening 28A through the strainer 26. As a float is placed on the stabilized water surface between the inner cylinder pipe 28 and the outer cylinder pipe 24, the accurate water level can be found. The efficient purification can be carried out by adjusting the degree of vacuum and the displacement based on the value of measuring the above-referred water level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for soil contamination, in which harmful volatile organic chlorine compounds such as trichloroethylene, tetrachloroethylene, and trichloroethane are removed from a soil contaminated by industrial waste by vacuum extraction. It relates to a purification method.

[0002]

2. Description of the Related Art In the case of soil contamination by volatile organochlorine compounds, the contaminants are present in the soil and groundwater as a gas phase or a liquid phase. In order to remove such contaminants from the soil, a suction well is dug from the ground surface to the target contaminated area, and a vacuum pump installed on the ground surface is used to extract the contaminants in the soil through the suction wells by vacuum extraction. The law is known.

FIG. 4 is a structural explanatory view showing the structure of a purifying apparatus using a vacuum extraction method. As shown in the figure, in the purification device 1, first, a contaminated area is excavated, and a suction well 2 is hermetically inserted into soil. Here, a strainer 3 is provided at the tip of the suction well 2, and by operating a vacuum pump described later, contaminants are removed from the strainer 3 by air in the soil,
As a vapor-liquid mixed flow of contaminant vapor, water vapor, and contaminated groundwater, the mixture is sucked in a flow as indicated by arrow 4. The strainer 3 also serves to prevent solids such as soil from entering the inside of the suction well 2 during suction.

[0004] The suction well 2 is connected to the connecting pipe 5 on the ground surface,
Further, it is connected to a gas-liquid separation tank 6, a vacuum pump 7 for generating a suction action, and the like. A processing tank 8 is provided at the subsequent stage of the vacuum pump 7, and the contaminants are adsorbed by activated carbon or the like in the processing tank 8, or decomposed by thermal decomposition or other methods.
It is discharged from the exhaust pipe 9 to the atmosphere. The progress of the purification is grasped by measuring the concentration of the sucked gas and contaminants in the groundwater, and the amount of suction.

[0005] However, the purification efficiency of the above-mentioned vacuum extraction method is as follows.
The nature of sucking the contaminants in the soil depends on the properties of the soil around the suction well 2. And among the properties of soil, the permeability is a major factor that determines the purification efficiency. Therefore, in order to increase the efficiency of soil purification, if groundwater is present in the soil, the load on the vacuum pump 7 is increased and the groundwater is immediately pumped up. It was necessary to change the degree of vacuum and the amount of exhaust of the vacuum pump 7 according to the state in the soil, such as suppressing the load on the pump 7. Therefore, it was necessary to detect the groundwater level inside the suction well 2 during the purification work. However, in the structure of the suction well 2 described above,
It could not be achieved.

The reason why the groundwater level inside the suction well 2 cannot be detected will be described with reference to FIGS.

FIG. 5 is a sectional view showing the state of groundwater when the vacuum pump is stopped in the same stratum.
FIG. 6 is a sectional view showing a state when the vacuum pump is operated in FIG. FIG. 7 is an explanatory diagram showing an operation state of a conventional purification device provided with a float type water level meter inside a suction well. As shown in FIG. 5, when the vacuum pump 7 is stopped, the normal groundwater level 10 fluctuates due to precipitation, changes in atmospheric pressure, tide level, and the like, but maintains a constant water level in the same stratum. However, as shown in FIG. 6, when the vacuum pump 7 is operated, the inside of the suction well 1 becomes negative pressure and the groundwater is discharged to the ground, so that the groundwater level 10 around the suction well 1 becomes lower than the level around the suction well.

As shown in FIG. 7, inside the suction well 1, a gas phase (air in soil, contaminant vapor, water vapor) and a liquid phase (contaminated groundwater) form a gas-liquid mixed flow on the ground. The groundwater level 11 inside the well 1 inside the suction well 1 is disturbed. Therefore, in the float type water level meter 12, the float 14 has the groundwater level 1 inside the well.
1 and moved up and down, and a stable water level could not be measured. In addition, even if a needle-type water level meter is used instead of the float type water level meter 12, since the groundwater moves in the suction well 1 as a gas-liquid mixed flow, there is a possibility that electricity may be supplied at any position, The stable water level cannot be measured. Further, even when a water pressure type water level meter was used, the water level could not be obtained because the inside of the suction well 1 was already at a negative pressure.

From these facts, in the conventional suction well 1,
During the operation of the vacuum pump 7, the position of the groundwater level 11 inside the well could not be grasped, and it was unclear whether the pipe was empty and sucking air or groundwater. For this reason, in the conventional method, the suction of the vacuum pump 7 is stopped several times during operation, and the groundwater level 10 is detected. Then, the degree of vacuum and the exhaust amount of the vacuum pump 7 were adjusted so as to correspond to the groundwater level 10, and the purification operation was performed again.

[0010]

However, in the above-mentioned purification method, it is necessary to stop the operation of the vacuum pump during the operation, which causes a reduction in purification efficiency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to provide a method for purifying a soil contamination capable of measuring a groundwater level in a suction well for performing vacuum extraction without stopping a suction operation. With the goal.

[0012]

According to the present invention, if the suction well has a double pipe structure, the water level can be measured stably between the inner pipe and the outer pipe even when the vacuum pump is operating. Based on the knowledge that the capacity of the vacuum pump can be optimally controlled based on the measurement results. That is, the soil contamination purification method according to the present invention is a soil contamination purification method in which a well for extracting contaminants is excavated in soil contaminated with harmful substances, and the contaminants in the soil are removed by suction using a vacuum pump. Is a double pipe, and the groundwater level during soil purification can be measured by a water level gauge provided between the inner pipe and the outer pipe of the double pipe.

The groundwater level during soil purification is measured by a water gauge between the inner pipe and the outer pipe of the double pipe. Based on the measured water level, the degree of vacuum generated by a vacuum pump and the vacuum pump Soil pollution purification treatment was performed by adjusting the displacement.

[0014]

According to the above construction, when the vacuum pump is operated, the gas phase and the liquid phase become a gas-liquid mixed flow from the inner tube and are sucked to the ground, and the water surface inside the inner tube is disturbed. . However, a stable water surface is formed between the inner tube and the outer tube because the suction force from the vacuum pump always works in the vertical direction and the outer tube prevents the water surface from being disturbed outside the suction well. can do. Therefore, if a water level gauge is provided between the inner pipe and the outer pipe, and the water level is detected by the water level gauge, it is possible to accurately capture the fluctuation of the groundwater level. Then, if the suction force of the vacuum pump is varied with this value, the purifying operation according to the internal state of the inner tube becomes possible,
As a result, the purification efficiency can be improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the method for purifying soil contamination according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a configuration diagram of a purification apparatus to which the soil contamination purification method according to the present invention is applied. As shown in the figure, in the purifying apparatus 20, a suction well 22 is excavated in a contaminated area and an outer tube 24 is hermetically inserted by a lid 25 as in the conventional vacuum extraction method. Here, a strainer 26 is provided at the tip of the outer tube 24 to perform suction in the ground and to prevent solids such as soil from entering the inside of the outer tube 24 during a suction operation described later. ing.

An inner tube 28 is inserted inside the outer tube 24 constructed as described above. The inner tube 28
The overall length including the above-mentioned ground portion is set longer than the overall length of the outer tube 24, and the position of the tip opening 28A on the underground side is just before reaching the strainer 26 attached to the tip of the outer tube 24. Has become. A gas-liquid separation tank 27A, a vacuum pump 27B, and a processing tank 27C are connected to one end protruding toward the ground surface. After the processing tank 27C, an exhaust pipe 27D for discharging the purified gas via these devices to the atmosphere is provided.

Between the inner tube 28 and the outer tube 26,
A float type water level gauge 32 serving as a water level gauge is provided.
This floats the float 34 in the groundwater 29 that has entered between the inner pipe 28 and the outer pipe 26, and measures the up and down movement of the float 34 with a recorder 38 via a wire 36. I have. Here, in the lid 25,
An insertion hole 37 is provided to allow the wire 36 to be inserted. The insertion hole 37 is set to have a diameter such that a slight gap is generated when the wire 36 is inserted. For this reason, the pressure on the ground side does not affect the inside of the suction well 22 via the insertion hole 37.

The amount by which the float 34 moves up and down is defined as the water level fluctuation of the groundwater 29. A signal line 39 for outputting the water level fluctuation of the groundwater 29 from the recorder 38.
A is drawn out, and the signal line 39A is connected to a control unit 39B for adjusting the degree of vacuum and the exhaust amount of the vacuum pump 27B. And the said control part 39B is the groundwater 2
When the signal of the water surface fluctuation amount 9 is received from the recorder 38, the optimum vacuum degree and the exhaust amount of the vacuum pump 7 according to the groundwater level are calculated, and the vacuum pump 7 is controlled by the control signal.

In such a suction well 22, when a vacuum pump is operated, the groundwater 29 becomes a gas-liquid mixed flow 30 in which a gas phase and a liquid phase are mixed, and is pumped to the ground through the inner tube 28. By this suction work, the space between the inner tube 28 and the strainer 26 becomes a negative pressure, and the groundwater 29 continuously enters from around the suction well 22, and the groundwater 29 enters the inner cylinder at the bottom of the suction well 22. It flows into the distal end opening 28A of the tube 28. Therefore, the inner tube 28 and the outer tube 24
Is not affected by the gas-liquid mixed flow 30 generated in the inner pipe 28, and a stable flow toward the opening of the inner pipe 28 is always formed. Become. Therefore, if the float type water level gauge 32 is installed between the inner pipe 28 and the outer pipe 24, the water level of the suction well 22 can be measured even while the vacuum pump 27B is operating.

If it is confirmed that the water level of the groundwater 29 has dropped due to the continuation of the pumping operation of the groundwater 29, it is determined that the ratio of the gas phase in the gas-liquid mixed flow 30 has increased, and the load of the vacuum pump 27B has been increased. And the degree of vacuum and the amount of exhaust may be adjusted. By detecting the water level of the groundwater 29 in this manner, the operation of the vacuum pump 27B according to the water level of the groundwater 29 becomes possible, and the purification efficiency can be improved. Here, in the purifying device 20, the float type water level meter 32 is used as the water level meter, but a needle type water level meter may be used instead.

FIG. 2 is an explanatory view showing a structure of a needle-type water level meter for detecting a water level, and FIG. 3 is a configuration diagram in a case where the needle-type water level meter is applied to a purification device.

In the purifying apparatus 20, when the suction well 22 has a double-pipe structure, the space between the inner pipe 28 and the outer pipe 24 is narrowed, and the float 34 of the float type water level meter 32 may not enter. In such a case, the inner tube 28 and the outer tube 2
A needle-type water level gauge 40 as shown in FIG. In the needle type water level meter 40, two covered wires 4
2 is installed parallel to the depth direction. And a pair of covered wires 4
2, a power supply 44 is provided, and an ammeter 46 is disposed on the path. Further, in the covered wire 42, an exposed portion 44 serving as a needle-shaped conductive portion is provided at an arbitrary interval.

In the needle-type water level meter 40 configured as described above, when the exposed portion 48 is immersed in the groundwater, a current flows through the pair of covered wires 42 via the groundwater 29, and the current value is measured by an ammeter 46. Can be measured by If the water surface of the groundwater 29 changes, the exposed portion 48 immersed in the groundwater 29 changes, and the resistance value of the current path changes. This makes it possible to capture the fluctuation of the water surface position of the groundwater 29 as a current value in the ammeter 46. Therefore, as shown in FIG. 3, even if the water surface position of the groundwater 29 is detected by using a needle type water level meter 40 instead of the float type water level meter 32, the soil contamination purification method according to the present invention can be implemented.

[0025]

As described above, according to the present invention, a soil contaminated by excavating a well for extracting contaminants in soil contaminated with harmful substances and sucking and removing contaminants in the soil by a vacuum pump. In the method, the suction well is formed as a double pipe, and the groundwater level during soil purification can be measured by a water level gauge provided between the inner pipe and the outer pipe of the double pipe. It is not affected by the turbulence of the water surface generated in the sea. Therefore, the groundwater level in the suction well can be measured without stopping the suction. Then, the groundwater level during soil purification is measured by a water level gauge between the inner cylinder pipe and the outer cylinder pipe of the double pipe, and based on the measured water level, the degree of vacuum generated by the vacuum pump and the displacement of the vacuum pump are determined. Since the soil contamination purification treatment is performed by adjusting the amount, efficient purification work can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a purification apparatus to which a soil contamination purification method according to the present invention is applied.

FIG. 2 is an explanatory diagram showing a structure of a needle-type water level meter that performs water level detection.

FIG. 3 is a configuration diagram in a case where a needle-type water level meter is applied to a purification device.

FIG. 4 is a structural explanatory diagram showing a configuration of a purification device using a vacuum extraction method.

FIG. 5 is a sectional view showing a state of groundwater when a vacuum pump is stopped in the same stratum.

FIG. 6 is a cross-sectional view showing a state when the vacuum pump is operated in FIG.

FIG. 7 is an explanatory diagram showing an operation state of a conventional purification device provided with a float type water level meter inside a suction well.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Purification apparatus 2 Suction well 3 Strainer 4 Arrow 5 Connecting pipe 6 Gas-liquid separation tank 7 Vacuum pump 8 Processing tank 9 Exhaust pipe 10 Groundwater level 11 Well inside groundwater level 12 Float type water level gauge 14 Float 20 Purification apparatus 22 Suction well 24 Outside Cylinder pipe 25 Lid 26 Strainer 27A Gas-liquid separation tank 27B Vacuum pump 27C Processing tank 27D Exhaust pipe 28 Inner cylinder pipe 28A Tip opening 29 Groundwater 30 Gas-liquid mixed flow 32 Float-type water level meter 34 Float 36 Wire 37 Insertion hole 38 Recorder 39A signal wire 39B control unit 40 needle-type water level meter 42 covered wire 44 power supply 46 ammeter 48 exposed part

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

Claims (2)

[Claims] 1. A soil pollution purification method in which a well for extracting contaminants is excavated in soil contaminated with harmful substances, and the contaminants in the soil are suctioned and removed by a vacuum pump. A soil contamination purification method, wherein a groundwater level during soil purification can be measured by a water level meter provided between the inner tube and the outer tube of the double tube. 2. A groundwater level during soil purification is measured by a water level gauge between an inner cylinder pipe and an outer cylinder pipe of the double pipe, and a degree of vacuum generated by a vacuum pump and a vacuum pump are measured based on the measured water level. The soil pollution purification method according to claim 1, wherein the soil pollution purification treatment is performed by adjusting the exhaust amount of the soil.