JPH06238260A - Removal of soil contamination with organochlorine compound - Google Patents

Abstract

PURPOSE:To remove an organochlorine compd. such as trichloroethylene remaining in soil in a safe form by oxidizing the same by ozone gas. CONSTITUTION:An ozone pressure intoruducing pipe 3 is driven in the contaminated part 4 of soil 9 and ozone gas is introduced into the contaminated part 4 under pressure by an ozone generator 1 to oxidize trichloroethylene in soil by ozone to change the same to a water-soluble org. substance and, further, water is injected in the soil 9 from a water injection pipe 12 to dissolve the water-soluble org. substance and the org. substance soln. is pumped up to the upper part through a water/gas discharge pipe 11 to remove trichloroethylene contained in the soil 9. By this constitution, the shortening of a removing time, cost reduction, the prevention of a contaminant from diffusion and technological development can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing soil contamination by organochlorine compounds, which tries to remove trichlorethylene and other organochlorine compounds remaining in soil by ozone gas in a safe form. Is.

[0002]

[Prior art]

(B) Environmental standards for harmful substances in soil were announced in August 1991, and the Environment Agency began studying regulatory measures for soil pollution in the spring of 4th year. According to a national survey conducted in November 1992, the Environmental Agency summarized that groundwater pollution by trichlorethylene and tetrachlorethylene, which are used in high-tech industries such as IC and in the cleaning industry, is still continuing. In this national survey, soil pollution was confirmed in a wide range of areas, but most local governments are having difficulty responding to the problems due to the enormous cost of removal, and cannot take radical measures. It is expected that the number of business establishments requiring countermeasures will increase to a considerable extent, and if low-cost removal methods are developed, their diffusion will progress rapidly. (B) In addition, in order to expand and strengthen water quality standards in accordance with the “Ideal standards for tap water quality” consulted by the Ministry of Health and Welfare, trichlorethylene, a general organochlorine compound, will be newly added from this fiscal year. Therefore, it is a compound that will continue to receive increasing attention as a substance to be monitored,
Potential demand is immeasurable. (C) Trichlorethylene is a precursor for the formation of carcinogens, and it remains in the soil and elutes in trace amounts into groundwater to contaminate well water for a long period of time, so early removal measures should be taken to prevent the spread of pollution. Is urgently needed.

[0003]

However, this has the following drawbacks. Due to its characteristics, trichlorethylene is insoluble in water and has a high specific gravity of 1.459. It gradually sinks downward in the soil, dissolves in water in a trace amount for a long period of time, and becomes a widespread source of well water pollution. Currently, as a countermeasure, a so-called vacuum extraction method, in which a well is dug and the inside pressure is reduced to extract soil gas containing harmful substances simultaneously with groundwater, has been put into practical use. However, this method has a problem in that it is difficult to remove in a short period of time and the processing cost is high. The present invention has been made to eliminate these drawbacks.

[0004]

As shown in FIG. 1, an ozone injection pipe (3) is driven into a contaminated part (4) of soil (9), and ozone gas is injected by an ozone generator (1) to generate ozone. By oxidizing trichlorethylene present in the soil with water to change it into a water-soluble substance, water is further injected through the water injection pipe (12) to dissolve the soluble organic substance, and the water / gas discharge pipe (11) pumps it up to Trichloroethylene contained in the soil (9) is removed. The present invention is a method for removing soil pollution by an organic chlorine compound having the above-mentioned constitution.

[0005]

[Function] Generally, substances that are considered to be produced by the oxidation reaction of trichlorethylene and ozone are trichloroacetic acid, trichloroacetaldehyde (chloral),
Trichloroethanol and the like. All the substances produced by the oxidation reaction with ozone are soluble in water, and it is considered that trichlorethylene can be removed by injecting it into soil by the oxidation treatment with ozone to dissolve it and collecting the water on the ground. Therefore, according to this method, trichlorethylene in the soil can be removed in a short period of time, the treatment cost is low, and the oxides can be safely taken out with water. Moreover, the construction period is short, and the diffusion of pollution to the surroundings is possible. Can also be prevented.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows the configuration of the present invention. (B) A ozone-injection pipe (3) is driven into the contaminated part (4) of the soil (9), ozone gas is injected by the ozone generator (1), and trichlorethylene existing in the soil is oxidized by ozone to dissolve the water-soluble substance. Change to. (B) The water injection pipe (12) is used to inject water into the soil (9) to dissolve soluble organic substances, and the water / gas discharge pipe (11)
The trichlorethylene contained in the soil (9) is removed by pumping it above the ground. The present invention is configured as described above, and the test and experimental results are as follows. (A) <Basic reaction test of ozone and trichlorethylene> Two samples were prepared by dispensing trichlorethylene into a sealed bag having gas barrier properties. About 10 ozone as a test area
Air having a concentration of 00 ppm was enclosed, while only air was enclosed in the same volume as the target section. After 1 hour, both trichlorethylene concentrations were measured by a detector tube. As a result, trichlorethylene was not detected in the test section, and the concentration in the target section was detected which was almost commensurate with the injection amount of trichlorethylene. As a result of the request test, the concentration of trichlorethylene is 1 / of the target area.
Only 100 or less was detected, demonstrating the support of the basic test and demonstrating that ozone can decompose trichlorethylene. (B) <Ozone Decomposition Experiment of Trichlorethylene Remaining in Soil> A certain plating company conducted an experiment to ozone-oxidize a trace amount of trichlorethylene remaining in the ground 1M from the ground surface. A pipe having an air hole at its tip was filled to a depth of 1M, and ozone air was continuously injected from above. Results of analysis of trichlorethylene concentration before and after test Trichlorethylene concentration Before test 0.072 mg / L After test 0.016 mg / L (Measurement method: Showa 48 Environmental Agency Notification No. 3, Appendix 3) Oxidation removal by ozone was possible.

[0007]

【The invention's effect】

(A) <Reduction of removal time> Since trichlorethylene has a high boiling point, desorption is not sufficient in the conventional vacuum extraction method from the soil, and it takes a long time to remove it. According to the present invention, ozone can be extracted from the soil in a shorter time by directly catalytically decomposing trichlorethylene to convert it into a water-soluble organic substance and dissolving it in water. (B) <Reduction of processing cost> The equipment is simple and the construction period can be shortened, so that the cost can be significantly reduced compared to the conventional price. (C) <Prevention of diffusion of pollution> By shortening the construction period, it is possible to prevent the diffusion of pollution to the outside. (D) <Possibility of technological development> By applying the present invention, technological development can be achieved for decomposition treatment of other organic pollutants existing in soil.

[Brief description of drawings]

FIG. 1 shows a configuration of the present invention.

[Explanation of symbols]

 1 Ozone generator 2 Compressor 3 Ozone injection pipe 4 Contaminated part 5 Filtration tank 6 Catalyst tower 7 Adsorption tower 8 Discharge pump 9 Soil 10 Clay layer 11 Water / gas discharge pipe 12 Water injection pipe 13 Water injection pump 14 Water tank

Claims (1)

[Claims] 1. A water-soluble compound obtained by reacting and oxidizing ozone with an organic chlorine-based compound such as trichlorethylene or tetrachloroethylene that has penetrated into the soil, and is removed from the soil by washing with water. Method for removing soil contamination by chlorine compounds.