JP3406434B2 - How to collect underground pollutants - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for recovering and removing volatile pollutants from the ground.

[0002]

2. Description of the Related Art Contamination of soil and groundwater due to outflow and infiltration of volatile substances has been a serious problem in obtaining drinking water, irrigation water and the like. Therefore, in order to remove these pollutants from the ground, especially from the upper layer, a method is devised, for example, in which a plurality of gas extraction wells formed in the ground are used to suction and collect the pollutants from the ground together with the gas. Has been done.
These wells are usually distributed and arranged in a lattice pattern as viewed from above in the contaminated zone to expand the treatment area and improve the treatment efficiency.

[0003]

However, in the above-mentioned conventional method, no matter how these wells are arranged, a gas unreachable portion is formed between the adjacent wells, and the wells are viewed from above. However, there is a problem that it remains as a diamond-shaped unprocessed portion.

On the other hand, due to the difference in the gas passage capacity in the ground, the gas in the ground forms gas passages in the ground in descending order of the gas passage ability. When concentrated, a gas unreachable portion may be formed in a region having a low gas passage ability and may remain as an untreated portion. Also,
The tendency is more remarkable as the difference in gas passage capacity in the ground is larger.

The present invention has been made in view of the above circumstances, and a method for recovering pollutants in the ground capable of efficiently recovering pollutants over the entire polluted zone without leaving unprocessed portions. The purpose is to provide.

[0006]

According to the present invention, a plurality of wells are dispersedly arranged in the ground of a polluted zone, a predetermined well is selected as a gas injection well from the plurality of wells, and the other wells are gas-filled. It is selected as an extraction well, and by injecting the gas into the ground from the gas injection well and sucking and recovering the gas from the gas extraction well, the pollutants in the ground are suctioned and recovered from the ground together with the gas. It relates to a method of recovering pollutants in the ground, and has the following features.

[0007]

A feature of the present invention is that in the method for recovering pollutants in the ground, the amount of gas in the ground is controlled by adjusting the amount of gas injected from the gas injection well and the amount of gas extracted from the gas extraction well. Depressurizing step to reduce the pressure of
By alternately repeating the injecting step of injecting the gas into the ground by adjusting the injecting amount and the extracting amount of the gas in the opposite direction to the depressurizing step, the pollutants can be recovered from the soil having different gas passing capacities. Is.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the present invention, a plurality of wells are dispersedly arranged in the ground of the contaminated zone, and a gas is injected into the ground from a predetermined well among the plurality of wells, and a gas is sucked and recovered from other wells. Therefore, when recovering the pollutant in the ground by suctioning and recovering the pollutant in the ground from the ground together with the gas, in particular, the operation method of the well is improved. Therefore, among the configurations related to the method of the present invention, illustration and description of the specific structure of the well and other configurations are omitted.

FIG. 1 shows a pollution zone 1 contaminated with pollutants.
It shows an example of the arrangement situation of the well 2 to the. Each of these wells 2 has a cylindrical shape, and gas (here, air) can be injected into the ground / sucked and recovered from the ground through the underground portion (reference numeral 2a in FIG. 1). Has become.

2 and 3 are plan views showing an example of the arrangement of the wells 2 in the contaminated zone 1. As shown in FIG. Well 2
Are arranged in a lattice shape for convenience, and of the wells 2, the reference numeral 21 in the drawing is a gas injection well and the reference numeral 22 is a gas extraction well. The well 2 is used as the gas injection well 21. Whether to use it as the gas extraction well 22 or not can be arbitrarily selected.

In the case of FIG. 2, these wells 2 are gas-injected so that wells vertically adjacent to each other in the figure become wells 2 of the same kind and wells vertically adjacent to each other in the figure become different wells 2. It is selected and used as the well 21 or the gas extraction well 22.

In this state, when the gas is injected into the ground from the gas injection well 21 at a constant pressure and the underground gas is sucked from the gas extraction well 22, the gas is injected from the gas injection well 21 side (high pressure side). Flow to the gas extraction well 22 side (low pressure side),
As a result, an air flow as shown by an arrow F in the figure is formed in the ground, and contaminants in the ground are volatilized and mixed into the air flow F due to contact with the gas forming the air flow F. Then, as the air flow F passes, the pollutants in the pollutant zone 1 are removed, while the gas in which the pollutants are mixed is sucked upward from the gas extraction well 22 and neutralized or decomposed to detoxify.

By the way, the gas released from the gas injection well 21 passes through the ground in a substantially straight line.
However, since the gas is sucked toward the lower pressure side, the effect of the pressure drop due to the gas extraction well 22 increases as the distance from the gas injection well 21 increases. As a result, the air flow F weakens while becoming linearly and gradually curved as it moves away from the gas injection well 21, leaving an unprocessed portion as indicated by symbol A in the figure. Since the amount of gas passing through the untreated portion A is relatively small or none, the pollutants contained in this region cannot be sufficiently recovered.

Therefore, in the present invention, after the gas is injected / sucked and recovered for a predetermined time in the state of FIG.
As shown in FIG. 2, a part of the well 2 that was the gas injection well 21 or the gas extraction well 22 in FIG. Gas injection and gas extraction well 2
The gas from 2 is sucked and collected. In the case of FIG. 3, well 2
Is a gas injection well 21 or a gas extraction well 22 so that different kinds of wells 2 are alternately arranged in the vertical direction in the figure.
Has been selected and used as.

Then, the pattern of the air flow passing through the contaminated zone 1 changes to that shown by the arrow R in the figure, and as a result, the air flow R passes through the untreated portion A and the untreated portion A. The contaminants inside are removed. On the other hand, in the case of FIG. 3 also, untreated points B are formed, but these untreated points B are the points where the pollutants have already been removed by the previous pollutant recovery shown in FIG. There is no problem because it exists. Then, by injecting / sucking and collecting the gas for a predetermined time in the state of FIG. 3, the pollutants are efficiently collected over the entire contaminated zone 1 without leaving unprocessed portions.

Here, how to change the arrangement of the gas injection well 21 and the gas extraction well 22 after the gas injection well 21 and the gas extraction well 22 are arranged in a predetermined order to collect the pollutants, The procedure is mainly as follows.

(1) The unprocessed portion is estimated from a simulation of an air flow formed by collecting the pollutant by the former arrangement or an actual flow rate measurement value. (2) Arrangement of the gas injection well 21 and the gas extraction well 22 is determined by simulation of the air flow formed by the pollutant recovery by various arrangements so that the air flow passes through the estimated untreated portion. Further, it goes without saying that the arrangement of the wells 21 and 22 and the subsequent recovery of the pollutants may be repeated many times until the untreated portions disappear.

On the other hand, due to the difference in the gas passage capacity in the ground, a gas unreachable area is formed in a region having a low gas passage ability and remains as an untreated area. For example, soil in which the pollution zone 1 is cracked. In such a case, it is dealt with by repeating the following two steps.

(1) Depressurizing step: By adjusting the amount of gas injected from the gas injection well 21 and the amount of gas extracted through the gas extraction well 22, the gas is sucked and recovered from the ground,
It lowers the pressure of gas in the ground. As a result, the pollutants are extracted from the fine channels formed in the ground that the gas does not pass through in the normal gas injection / suction.

(2) Injection process: The gas is injected into the ground by adjusting the injection amount of the gas from the gas injection well 21 and the extraction amount of the gas through the gas extraction well 22. As a result, new gas (uncontaminated) is supplied to the fine flow path, and the pollutants extracted in the depressurization step are brought into equilibrium with the newly supplied gas.
This pollutant is sucked and collected together with the gas from the gas extraction well in the next depressurization step.

That is, by repeating the above steps, it becomes possible to recover the pollutants from the region having a low gas passage ability. Therefore, pollutants can be recovered from soils having different gas passage capacities in the ground without leaving unprocessed parts.

Further, during the depressurizing step and the injecting step, while the gas pressure in the ground is kept at a low level, the gas is injected from the gas injection well 21 and the gas is sucked and recovered from the gas extraction well 22. You may provide the collection process which performs. By providing this step, it becomes possible to collect the pollutants together with the air flow from the gas injection well 21 to the gas extraction well 22 without waiting for the next depressurization step.

Here, in the injection step, the gas may be injected by a pump (not shown) connected to the gas injection well 21, and when air is used as the gas, the gas injection well 21 is used. You may open to the atmosphere and inject air directly from the atmosphere into the ground.

Further, as shown in FIGS. 2 and 3, the arrangement of the gas injection well 21 and the gas extraction well 22 for the contamination zone 1 is changed to inject / suck and recover the gas, and the above-described decompression step (recovery). It is also possible to use a combination of repeated steps) and injection steps.

[0026]

As described above, according to the present invention, even in soils having different gas passage capacities in the ground, pollutants can be efficiently removed over the entire contaminated zone without leaving untreated portions. It becomes possible to collect it.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of the arrangement of wells in a contaminated zone contaminated with pollutants.

FIG. 2 is a plan view showing an example of the arrangement of wells in a contaminated zone.

FIG. 3 is a plan view showing an example of the arrangement of wells in a contaminated zone.

[Explanation of symbols]

1 pollution zone 2 wells 21 Gas injection well 22 Gas extraction well A, B untreated part

Claims (2)

(57) [Claims] 1. A plurality of wells are dispersedly arranged in the ground of a contaminated zone, and a predetermined well of the plurality of wells is selected as a gas injection well, and another well is selected as a gas extraction well, By injecting the gas from the injection well into the ground and by suctioning and recovering the gas from the gas extraction well, the contaminants in the ground are recovered by suction from the ground together with the gas. In the method, the amount of gas injected from the gas injection well and the gas extraction well
Adjusting the amount of gas extracted from the door to reduce the pressure of the gas in the ground, and adjusting the injection amount and the extraction amount of the gas in the opposite direction to the depressurizing process. The method for recovering pollutants in the ground, characterized in that the pollutants are recovered from soils having different gas passage capacities by alternately repeating the injection step of injecting the gas into the ground. 2. Between the depressurizing step and the injecting step,
While maintaining the underground pressure at a low level, and the injection of the gas from the gas injection wells, claims, characterized in that a recovery step for performing suction recovery of the gas from the gas extracting wells Item 1. A method for collecting underground pollutants according to Item 1 .