JP2012040476A - Method and device for purifying contaminated soil or groundwater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for purifying contaminated soil or groundwater, the method being applicable to a ground which is low in water permeability.SOLUTION: This is a method which purifies, at a purification site, contaminated soil 6 or groundwater, which is contaminated with volatile organic compounds, the contaminated soil 6 being low in water permeability. In this case, microbubbles and a nourishing agent, which prompts microorganisms living in the contaminated soil 6 to decompose the volatile organic compounds, are poured into the contaminated soil 6 to stir and mix them. By this, the microbubbles and nourishing agent for the soil purification are surely supplied to a ground which is low in water permeability, and the contaminated soil or groundwater which is contaminated with the volatile organic compounds is purified inexpensively.

Description

  The present invention relates to a purification method and apparatus for contaminated soil or groundwater contaminated with volatile organic compounds (VOC) such as benzene, and more particularly to a method and apparatus for purification of contaminated soil or groundwater suitable for purification of low-permeability ground. Is.

  Conventionally, there has been known a method of purifying contaminated soil in situ by supplying oxygen and nutrients to contaminated soil contaminated with volatile organic compounds such as benzene and oil to enhance the decomposition activity of indigenous microorganisms. (For example, refer to Patent Document 1).

  The oil-contaminated soil purification method of Patent Document 1 is a method in which a nutrient source (degradation promoting substance) and fine bubble-containing water are each put into an injection well and oil in the soil is decomposed by the action of microorganisms. Here, it is shown that the nutrient source (degradation promoting substance) is supplied from the upper part of the injection well, and the water containing fine bubbles is supplied from the lower part of the injection well.

  On the other hand, by installing a well in a volatile organic compound-contaminated area and agitating the infiltrating part where the pollutant stayed before carrying out purification, the volatile organic compound is diffused into the groundwater. It is known to purify contaminated soil and groundwater (see, for example, Patent Document 2).

JP 2009-6304 A JP 2002-86130 A

  However, since the above-described conventional purification method such as Patent Document 1 is a method in which a well is constructed in the ground to be purified, and a liquid nutrient source or air is sent to the surrounding soil through this well, and therefore applicable soil quality Was limited to highly permeable ground such as sand and gravel. When this purification method is applied to ground with low water permeability such as clay and silt, it may be necessary to construct a huge number of wells, or purification may be difficult. For this reason, development of the purification technique applicable to a low-permeability ground was desired.

  This invention is made | formed in view of the above, Comprising: It aims at providing the purification method and apparatus of the contaminated soil or groundwater applicable to a low-permeability ground.

  In order to solve the above-described problems and achieve the object, the method for purifying contaminated soil or groundwater according to claim 1 of the present invention is based on the contaminated soil or groundwater with low water permeability contaminated with volatile organic compounds. In the method of purifying the contaminated soil, while injecting fine bubbles and a nutrient for promoting the decomposition of volatile organic compounds by microorganisms living in the contaminated soil, the contaminated soil Are mixed and stirred.

  Moreover, the purification method for contaminated soil or groundwater according to claim 2 of the present invention is characterized in that, in claim 1 described above, the fine bubbles are millibubbles, microbubbles having a diameter of 50 μm or less, and nanobubbles having a diameter of 1 μm or less. And

  Moreover, the purification apparatus for contaminated soil or groundwater according to claim 3 of the present invention is an apparatus for purifying contaminated soil or groundwater with low water permeability contaminated with a volatile organic compound in its original position. The contaminated soil is mixed and stirred while injecting fine bubbles and a nutrient for promoting the decomposition of volatile organic compounds by microorganisms living in the contaminated soil.

  Moreover, the purification apparatus for contaminated soil or groundwater according to claim 4 of the present invention is characterized in that, in claim 3 described above, the fine bubbles are millibubbles, microbubbles having a diameter of 50 μm or less, and nanobubbles having a diameter of 1 μm or less. And

  According to the present invention, there is provided a method for purifying in-situ contaminated soil or groundwater having low water permeability contaminated with volatile organic compounds, wherein the contaminated soil has fine bubbles and inhabited in the contaminated soil. The contaminated soil is mixed and agitated while injecting a nutrient for promoting the decomposition of volatile organic compounds by microorganisms that are present, so that fine bubbles and nutrients for soil purification are reliably supplied to the low-permeability ground. Therefore, it is possible to purify contaminated soil or groundwater contaminated with volatile organic compounds at low cost.

FIG. 1 is a side sectional view showing an embodiment of a purification apparatus for contaminated soil or groundwater according to the present invention. FIG. 2 is a diagram for explaining the characteristics of the fine bubbles. FIG. 3 is a diagram showing the purification status when fine bubbles are used. FIG. 4 is a diagram showing a purification state when fine bubbles are not used.

  Hereinafter, embodiments of a method and apparatus for purifying contaminated soil or groundwater according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  As shown in FIG. 1, a contaminated soil or groundwater purification apparatus 10 (hereinafter simply referred to as “purification apparatus”) according to the present invention uses contaminated soil 6 or groundwater with low water permeability contaminated with a volatile organic compound. In this method, the soil is mixed and stirred while injecting fine bubbles containing oxygen and nutrients into the contaminated soil 6. As a result, a purification range 12 in which these are mixed is formed.

  The purification device 10 includes a nutrient solution storage tank 14, a fine bubble liquid generation device 16, a stirring tank 18, and a stirring heavy machine 20 provided on the surface 8. The nutrient storage tank 14 is a storage tank for storing a liquid nutrient for promoting the decomposition of volatile organic compounds by microorganisms living in the contaminated soil 6. Moreover, the fine bubble liquid production | generation apparatus 16 is an apparatus for generating the liquid containing a fine bubble.

  The nutrient in the nutrient storage tank 14 and the liquid containing the fine bubbles generated in the fine bubble liquid generator 16 are sent to the stirring tank 18 and mixed and stirred. The mixture of nutrients and fine bubbles in the agitation tank 18 is sent to the agitation heavy machine 20.

  On the other hand, the agitation heavy machine 20 is provided with an agitation mechanism 22, and the contaminated soil 6 is agitated by the mechanism 22 to construct the purification range 12 in the soil 6. In addition, as the heavy machinery 20 for stirring, it is possible to utilize the heavy machinery for stirring used for the deep ground improvement process etc.

  When the purification range 12 is constructed by the stirring mechanism 22, the soil is mixed and stirred while injecting a mixture of fine bubbles and nutrients into the contaminated soil 6. Thereby, fine bubbles and nutrients for soil purification can be reliably supplied to the soil 6 in the low-permeability ground, and the contaminated soil or groundwater contaminated with volatile organic compounds such as benzene is purified at low cost. be able to.

  Here, the fine bubbles are millibubbles, microbubbles having a diameter of 50 μm or less, and nanobubbles having a diameter of 1 μm or less. For example, microbubbles or millibubbles having a diameter of 50 μm or less are included. Air, oxygen, ozone or the like can be used as the raw material for the fine bubbles. Moreover, tap water, ground water, etc. can be used as a liquid raw material containing fine bubbles.

  As shown in FIG. 2, the characteristics of fine bubbles having a diameter of 50 μm or less are as follows: (1) The rising speed in water is slower than normal bubbles (several mm to 50 μm); (2) The pressure in the bubbles is It is known that (3) the gas-liquid area is large, (4) the bubble surface is negatively charged, etc. Year "). In addition, as shown in FIG. 2, a normal bubble rises in water and bursts on the surface. Microbubbles shrink in water and eventually disappear. Nanobubbles are characterized by being present in water for a long period of time.

  The number of fine bubbles and the particle size distribution differ depending on the manufacturing principle. Typical manufacturing principles include (1) pressure dissolution method, (2) swirl method, and (3) static mixer method. (See reference "Microbubble generation method and application to industrial equipment, Terasaka, environmental purification technology, vol. 6 (11), pp. 13-17, 2007").

  Since the fine bubbles are easily dissolved in water or are easily retained for a long period of time, the amount of dissolved oxygen in the groundwater is increased, and activation of aerobic microorganisms in the soil can be promoted.

  Next, the difference in the purification effect between when the fine bubbles are used and when they are not used will be described taking as an example a soil composed of a silt layer, a saturated layer, and an unsaturated layer.

  FIG. 3 shows a conceptual diagram of the state of purification in soil when fine bubbles are used. As shown in FIG. 3, when the liquid and nutrient containing fine bubbles are injected into the holes provided in the soil composed of the silt layer, the saturated layer and the unsaturated layer, the supply area of the liquid containing fine bubbles and the nutrient to the soil Therefore, activation of a wide range of aerobic microorganisms is promoted early. As a result, reliable purification is possible in a short period of time. Moreover, this purification effect is maintained for a long time in the soil.

  On the other hand, in the case of the conventional purification method that does not use fine bubbles, as shown in FIG. 4, the area for supplying aerobic microorganisms is narrowed because the area for supplying oxygen gas to the soil is narrowed, and the purification efficiency is reduced. Is inferior to the present invention using fine bubbles. There is also a demerit that the cost of the oxygen gas is increased because the labor and time for supplying oxygen gas and the gas recovery equipment are required.

  As described above, according to the present invention, there is a method for purifying low-permeability contaminated soil or groundwater contaminated with a volatile organic compound in situ, wherein the contaminated soil includes fine bubbles and the contamination. The contaminated soil is mixed and agitated while injecting a nutrient for promoting the decomposition of volatile organic compounds by microorganisms living in the soil, so that fine bubbles and nutrients for soil purification are added to the low-permeability ground. The agent can be reliably supplied, and contaminated soil or groundwater contaminated with volatile organic compounds can be purified at low cost.

  As described above, the method and apparatus for purifying contaminated soil or groundwater according to the present invention is useful when purifying contaminated soil or groundwater in situ, and in particular, purifies contaminated soil or groundwater in a low-permeability ground. Suitable for

6 Soil 8 Ground 10 Contaminated soil or groundwater purification device 12 Purification range 14 Nutrient storage tank 16 Fine bubble liquid generator 18 Stirring tank 20 Stirring heavy equipment 22 Excavation stirring mechanism

Claims (4)

A method for purifying in-situ contaminated soil or groundwater contaminated with volatile organic compounds with low permeability,
The contaminated soil is mixed and stirred while injecting fine bubbles and a nutrient for promoting decomposition of volatile organic compounds by microorganisms living in the contaminated soil into the contaminated soil. To clean contaminated soil or groundwater.   The method for purifying contaminated soil or groundwater according to claim 1, wherein the fine bubbles are millibubbles, microbubbles having a diameter of 50 µm or less, and nanobubbles having a diameter of 1 µm or less. A device that purifies contaminated soil or groundwater with low water permeability contaminated with volatile organic compounds in situ,
The contaminated soil is mixed and stirred while injecting fine bubbles and a nutrient for promoting decomposition of volatile organic compounds by microorganisms living in the contaminated soil into the contaminated soil. To purify contaminated soil or groundwater.   4. The apparatus for purifying contaminated soil or groundwater according to claim 3, wherein the fine bubbles are millibubbles, microbubbles having a diameter of 50 [mu] m or less, and nanobubbles having a diameter of 1 [mu] m or less.

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