Hydraulic and earth engineering – Soil remediation – In situ contaminant removal or stabilization
Reexamination Certificate
1998-12-21
2001-06-26
Will, Thomas B. (Department: 3673)
Hydraulic and earth engineering
Soil remediation
In situ contaminant removal or stabilization
C405S128100, C405S128150, C405S128700, C366S150100, C366S293000, C366S296000, C588S260000, C588S900000
Reexamination Certificate
active
06250846
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for purifying contaminated soil and to a method for remedying soil contaminated with pollutants.
2. Related Background Art
Chlorinated aliphatic hydrocarbon compounds such as trichloroethylene, and aromatic compounds such as phenol, are chemically very stable, and have been used in a large amount as raw materials for chemical or as cleaning solvents for semiconductors or machinery because of their high solubility for grease. On the other hand, their carcinogenicity has been pointed out. Thus organic chlorinated compounds leaked or discarded into the environment have become a source of wide range environmental pollution over the world.
Since well water, especially, is used in large quantities for industrial/agricultural use as well as drinking water, survey of the soil and groundwater contamination and a measure therefor are required urgently.
The number of the chemical substances under regulation is increasing year by year, and now is the time to make every effort to remedy the polluted environment worldwide.
To purify the soil and groundwater contaminated with organic compounds, there are two approaches: physicochemical approach and microbiological approach. For example, the physical/chemical approach includes heating or incinerating treatment of the dug-up contaminated soil, vacuum extraction of the pollutants from the contaminated soil, and aeration or adsorption treatment of the pumped-up contaminated groundwater. Neither of the vacuum extraction and pump-up aeration approaches, however, make the organic compounds harmless, requiring a further process to make them harmless.
On the other hand, the microbial remediation of the polluted environment (hereafter referred to as “bioremediation”) has been attracting considerable attentions as a more eco-minded approach than physicochemical approaches, since it allows degradation of pollutants into essentially harmless substances. One embodiment of the bioremediation is in situ remediation treatment. This is to purify the contaminated soil by directly introducing a microorganism capable of degrading pollutants into the polluted environment (soil, groundwater etc.), by propagating the native microorganisms capable of degrading the pollutant in the polluted environment, or by directly introducing certain substances to elicit or improve the pollutant-degrading activity of the native microorganisms.
For example, DE 4003362 A1 discloses a purification method in which the contaminated soil is mechanically agitated and crushed to uniformly mix with a degrading microorganism and nutrients.
EP 0620055 A1 describes a method in which the contaminated soil is mechanically agitated while injecting compressed air and the exhausted gaseous pollutant is collected for purification.
DE4028055 A1 describes a purification method in which the contaminated soil is dug while sprinkling microorganisms to the soil.
Alternatively, there is an approach to move the pollutant such as organic chlorinated compounds in the environment. U.S. Pat. No. 5347070, for example, describes a method in which a plurality of electrodes are inserted into the soil polluted with organic chlorinated compounds and sending an electric current to the soil to raise the soil temperature, so that the pollutants are vaporized to be removed. Further, U.S. Pat. No. 5340570 discloses a method in which pollutants are removed by electroosmosis due to an electric field applied to the soil.
Japanese Patent Application Laid-Open No. 7-112177 discloses an apparatus for effective in situ remediation of polluted soil, which comprises soil-agitating means for agitating the soil while penetrating it, means for supplying the agitated soil with a dispersion of a microorganism, and means for supplying a material to activate the microorganism. Disclosed also is a method for remedying a contaminated soil by using this apparatus, which comprises steps of: boring and agitating the contaminated soil using a device capable of boring and agitating the soil, feeding the soil with a dispersion of a microorganism capable of treating the contaminated soil, and agitating the soil for a prescribed period of time while injecting a substance(s) to activate the microorganism. These steps as one cycle are repeated in different places according to the area and site of the contaminated soil. As described above, various types of in situ bioremediation have been proposed.
The present inventors have learned from the previous studies that it should be avoided as much as possible for the introduced foreign microorganism or compounds which do not originally exist in the soil but required for in situ bioremediation to affect the ecological system of the polluted environment, particularly after the remediation.
SUMMARY OF THE INVENTION
The present invention has been made from the above point of view. An object of the present invention is to provide an apparatus for purifying the contaminated soil which can diminish the influence on the ecological system of the environment to be remedied as much as possible carrying out in situ environmental remediation more effectively.
It is another objective of the present invention to provide a method for remedying contaminated soil which enables the control of the influence on the ecological system of the environment to be remedied as well as the effective purification of the polluted environment in situ.
The device for remediation of contaminated soil to achieve the above objects comprises the following means:
(a) excavating means for excavating the soil,
(b) agitating means for agitating the soil,
(c) feeding means for introducing into the soil at least one agent selected from the group consisting of a microorganism capable of degrading the pollutant, a nutrient for the microorganism and an inducer to make the microorganism express the pollutant-degrading activity; and
(d) measuring means for measuring the pollutant concentration in the soil.
A method for remedying contaminated soil to achieve the above objectives comprises the steps of:
(1) excavating the soil contaminated with a pollutant,
(2) agitating the soil,
(3) measuring the pollutant concentration in the soil, and
(4) introducing into the soil at least one agent selected from the group consisting of a microorganism capable of degrading the pollutant, a nutrient for the microorganism, and an inducer to make a microorganism express the pollutant degrading capability,
wherein at least one of the steps (1), (2) and (4) is controlled according to the pollutant concentration obtained by the step (3).
By controlling the remedying treatment according to the sites and the pollutant concentration in the contaminated soil, it is possible to suppress the level of disturbance of the ecological system due to the introduced microorganism, nutrients or inducer. In addition, this method makes unnecessary to add the microorganism, nutrients or inducer superfluously to the soil, enabling more efficient remediation of the contaminated soil.
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patent: 4003362 (1991-08-01), None
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patent: 0453839 (1991-10-01), None
patent: 0569199 (1993-11-01), None
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patent: WO 86-01439 (1986-03-01), None
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Patent Abstracts of Japan, vol. 1998, No.
Handa Takeshi
Iio Masatoshi
Kawabata Yuji
Senshu Yuri
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Hartmann Gary S.
Will Thomas B.
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