JP2001009060A - Method for removing hazardous material in soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the efficient and rapid removal of hazardous materials in soil by a device of a small scale and to enable the removal even in the soil where hardly water permeable strata exist. SOLUTION: This method for removing the hazardous materials in soil consists in supplying ozone alone or gas containing the ozone, oxygen and an oxidizing agent into the soil 2 from an injection well 1a and decomposing the hazardous materials in the soil 2 by the oxidation effect of this gas. In the case of the latter, the oxidizing agent described above is preferably hydrogen peroxide or hypochlorous acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for removing harmful substances in soil.

[0002]

2. Description of the Related Art Volatile organic compounds (V
As a method of removing OC), there is a method in which a gas is supplied into the soil from an injection well, a volatile organic compound in the soil is transferred to the gas, and then the gas is sucked and collected from the extraction well together with the gas.

[0003]

However, in the case of the above-mentioned method, in addition to the injection well, an apparatus for gas recovery such as an extraction well and a vacuum apparatus, and an apparatus for treating the recovered gas are required. As a result, there has been a problem that the apparatus becomes large-scale and it takes a long time to install and withdraw the apparatus. In addition, if there is a poorly permeable layer such as a clay layer directly above the soil to which the gas is supplied, the upward movement of the supplied gas is hindered by the poorly permeable layer, and the gas accumulated below the poorly permeable layer is removed. Pollution could spread with groundwater and spread. The present invention has been made in view of the above circumstances, the harmful substances in the soil including the volatile organic compound, efficiently remove in a short time by a small-scale device, especially, the presence of a poorly permeable layer It is intended to be removable even in soil.

[0004]

According to the present invention, ozone alone or a gas containing ozone, oxygen and an oxidizing agent is supplied into soil from an injection well, and harmful substances in the soil are oxidized by the gas. It is characterized by being decomposed by. In the latter case, the oxidizing agent is desirably hydrogen peroxide or hypochlorous acid.

The harmful substances that can be removed by the method for removing harmful substances in soil according to the present invention include, in addition to the volatile organic compounds, dioxin, PCB, cyanide, and the like.
Contains oxidatively degradable harmful substances.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an apparatus used in the method for removing harmful substances in soil according to the present invention. Code 1, 1
a is an injection well, and the injection well denoted by reference numeral 1 is erected in the soil 2 so as to open to an unsaturated layer (range indicated by an arrow A in the figure) in the soil 2, and the injection well denoted by reference numeral 1a is: It is erected in the soil 2 so as to penetrate the unsaturated layer A and the poorly permeable layer A ′ and open to the aquifer (the range indicated by the arrow B in the figure). The upper ends of the injection wells 1 and 1a are connected to a gas supply device 5 via a pipe 3.

When removing harmful substances from the soil 2, gas supplied from the gas supply device 5 is supplied to the injection wells 1 and 1a through the pipe 3, and the unsaturated layer A is supplied from the injection wells 1 and 1a. Alternatively, the water is supplied to the aquifer B. The gas supplied from the injection well 1 to the unsaturated layer A moves in the unsaturated layer A as shown by an arrow C. Further, the gas supplied from the injection well 1a to the aquifer B rises while contacting the groundwater in the aquifer B, as shown by the arrow D, and the impervious layer A '
To move down.

In the present invention, the gas supplied from the gas supply device 5 into the soil 2 through the pipe 3 and the injection wells 1 and 1a contains ozone alone or ozone, oxygen and an oxidizing agent. Use a gas. In addition, hydrogen peroxide or hypochlorous acid is used as the oxidizing agent.

Then, the harmful substances in the soil 2 are subjected to oxidative decomposition by ozone or accelerated oxidative decomposition by ozone, oxygen and an oxidizing agent in the soil 2 to carbon dioxide, water, chlorine gas or hydrochloric acid. Decomposed and removed. These decomposition products are dissolved in the soil 2 and made harmless.

That is, according to the present invention, since the harmful substances in the soil 2 are decomposed in the soil 2 by the action of the supplied gas, various devices for collecting the supplied gas, and furthermore, A processing device or the like for the recovered gas becomes unnecessary.
As a result, the size of the device is reduced, and the time required for installation and withdrawal of the device is reduced.

Further, since the harmful substances in the soil 2 are decomposed in the soil 2 and the gas is dissolved in the water, a poorly permeable layer A 'such as a clay layer is formed immediately above the soil 2 to which the gas is supplied. Even if the existing gas is prevented from moving upward by the impervious layer, the harmful substances in the soil 2 are diffused together with the gas accumulated below the impervious layer A 'and the pollution is expanded. There is no.

In addition, harmful substances to be removed include, for example, dioxin and PC in addition to the volatile organic compounds.
Since it is expanded to toxic substances that can be oxidized and decomposed, such as B and cyanide, it is possible to treat harmful substances that were conventionally difficult to treat in the soil 2.

[0013]

As described above, according to the method for removing harmful substances in soil according to the present invention, harmful substances in soil are oxidized or decomposed by ozone supplied from the injection well in the soil. As it is decomposed by accelerated oxidative decomposition by oxygen and oxidizing agent, various devices for collecting the supplied gas and processing devices for the collected gas are not required, and as a result, harmful substances in the soil Can be efficiently removed in a short time by a small-scale device.

Further, even if the upward movement of the supplied gas is hindered by the impervious layer, the gas dissolves in the water, so that harmful substances in the soil diffuse together with the gas accumulated below the impervious layer. As a result, the contamination does not increase, and the removal operation can be performed even on the soil where the poorly permeable layer exists.

Further, harmful substances to be removed are not only volatile organic compounds (VOC) but also dioxins, P
Since it is expanded to harmful substances that can be decomposed by oxidation, such as CB and cyanide, it is possible to treat harmful substances that have conventionally been difficult to treat in soil.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an apparatus used in the method for removing harmful substances in soil according to the present invention.

[Explanation of symbols]

 1,1a Injection well 2 Soil

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Claims (3)

[Claims] Claims 1. An ozone is supplied from an injection well into soil.
A method for removing harmful substances in soil, comprising decomposing the harmful substances in soil by the oxidizing action of ozone. 2. A gas containing ozone, oxygen and an oxidizing agent is supplied from the injection well into the soil, and the harmful substances in the soil are decomposed by the oxidizing action of the ozone, oxygen and the oxidizing agent. How to remove harmful substances in soil. 3. The method for removing harmful substances in soil according to claim 2, wherein the oxidizing agent is selected from hydrogen peroxide or hypochlorous acid.