JP2006326500A - Purification method of contaminated soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a purification method of contaminated soil using decomposition fungus, capable of purifying the contaminated soil in a short period at a low cost in situ, or in the ground where the soil is originally present. <P>SOLUTION: In this purification method of contaminated soil, bio-slurry containing microorganisms and its nutrient having decomposition function of contaminants contained in the soil of the ground 4, is injected into the ground 4 through an injection pipe 6 erected in the ground 4. The bio-slurry of a high oxygen concentration obtained by dissolving microorganisms and nutrient into water of high oxygen concentration is used. The bio-slurry is laterally jetted from the injection pipe 6 erected into a given depth, and the injection pipe is rotatingly pulled up, to widely spread the highly active bio-slurry around the injection pipe. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for purifying contaminated soil with microorganisms having the ability to decompose pollutants (hereinafter referred to as “degrading bacteria”). The present invention relates to a method of injecting a treatment liquid mixed with the nutrients to purify the soil in the ground in situ.

  Work to clean the soil contaminated with organic chlorinated compounds such as tetrachloroethylene and dioxin and organic solvents such as benzene by injecting treated water containing the function of degrading these pollutants and their nutrients into the soil. Has been done.

  This type of work currently being carried out involves installing an injection tube in soil containing pollutants, and pouring treated water (bioslurry) into the injection tube mixed with decomposing bacteria and nutrients into water. In order to activate the decomposing bacteria injected into the soil, the air (oxygen) can be periodically supplied to the ground after injecting the decomposing bacteria. Has been done.

  Purification of contaminated soil with such degrading bacteria is characterized in that low concentration contaminated soil over a wide range can be purified at a relatively low cost.

  As a method for injecting treated water into the ground from an injection tube, Patent Document 1 below proposes a method in which treated water is ejected from the tip of the injection tube in a horizontal direction and pulled up while rotating the injection tube. In the method disclosed in this document, by supplying pressurized water into the soil, a part of the soil is slurried, and the treated water is supplied to the slurryed part, so that the treated water can be supplied to a wide range at a low cost. It can be injected.

Patent Document 2 discloses a pump having a function of mixing gas.
Japanese Patent Laid-Open No. 11-216457 JP 10-33961 A

  As described in Patent Document 1 mentioned above, in this type of purification method, it is important to allow the treated water to permeate as wide a range as possible centering on the injection pipe in order to reduce the construction cost.

  In order to achieve uniform purification throughout the soil to be treated, it is necessary for the degrading bacteria to penetrate into the soil evenly. If the diffusion range of treated water from the injection pipe is narrow, the injection pipe must be installed at short intervals. On the other hand, if the injected treated water spreads over a wide area centering on the injection pipe, the interval between the injection pipes can be increased accordingly, and the injection pipes can be installed per unit area of the soil to be purified. Since the number can be reduced, the cost of purification work can be reduced.

  The treated water injected into the ground gradually spreads, and the decomposing bacteria also grow and spread. Therefore, even if the interval between the installation of the injection pipes is wide to some extent, over time, the degrading bacteria will spread throughout the soil and purification will be performed. However, in this case, the nutrients injected with the decomposing bacteria are diffused and the decomposition process is performed in a low activity state in which less oxygen permeates into the soil, so the purification takes a long time from six months to two years. There is a problem that it takes. In order to maintain the activity of the decomposing bacteria, a method of injecting oxygen and nutrients regularly after injecting the decomposing bacteria has also been proposed, but the effect is small although the cost increases.

  On the other hand, the method described in Patent Document 1 is to disperse the injected decomposing bacteria and nutrients over a wide range centering on the injection tube by slurrying the soil to be purified. This method is effective in terms of the diffusion of degrading bacteria, but has the problem that the soil strength decreases due to the slurrying of the soil, and is unsuitable for purification of land where buildings and the like are to be built.

  The present invention provides a method for purifying soil in an in-situ location where soil can be purified in a short period of time by using biometering technology and construction can be performed at low cost, that is, land where the soil originally exists. The challenge is to do.

  The present invention relates to a contaminated soil purification method in which a bioslurry containing a microorganism having a function of decomposing pollutants contained in soil of the ground and a bioslurry containing the nutrients is injected from an injection pipe 6 built in the ground 4. A high-slurry bioslurry obtained by melting nutrients in water containing high-concentration oxygen is used, and the bioslurry is injected 10 from the injection tube 6 in which the bioslurry is built up to a predetermined depth in a lateral direction. The above-mentioned problems are solved by providing a method for purifying contaminated soil, characterized in that, by pulling up while rotating, a highly active bioslurry is permeated widely around the injection tube.

  In this invention, oxygen is forcibly mixed with the bioslurry to raise the dissolved oxygen concentration. Although the dissolved oxygen concentration of water is usually about 8%, a highly active bioslurry is produced by raising this to 40-50%. At the time of producing the bioslurry, oxygen is forcibly supplied as fine bubbles from the cylinder into the produced bioslurry or the water used to produce it. More preferably, bioslurry or water in which oxygen is dissolved at a high concentration by stirring or pumping water as the bioslurry or its material while supplying oxygen from a cylinder to a pump having a function of sucking and mixing gas. Is made. When high-oxygen water is produced, degrading bacteria and their nutrient sources are added and mixed therein to obtain a bio-slurry with a high dissolved oxygen concentration.

Injection of bioslurry into the soil is ensured by installing the injection tube 6 to the planned depth and rotating and raising the injection tube 6 while high-pressure jetting bioslurry from a nozzle provided horizontally at the tip of the injection tube 6. Realization of soil mixing. The injection pressure of bioslurry into the soil is preferably about 30 to 40 megapascal / cm ² .

  Activating degrading bacteria to increase the ability to decompose pollutants is directly related to shortening the purification period of contaminated soil. In this invention, oxygen can be effectively and continuously supplied from the water having a high dissolved oxygen concentration to the degrading bacteria. Since dissolved oxygen is retained by water as a solvent, it does not diffuse rapidly like gaseous oxygen, and it is possible to continue supplying oxygen necessary for decomposing bacteria over a long period of time.

  By injecting bioslurry from the injection tube 6 in a horizontal direction and forcibly mixing the soil of the ground to be improved, decomposing bacteria and their nutrients, reliable mixing of soil contaminants and decomposing bacteria is realized. it can. This and the fact that the activity of degrading bacteria is enhanced by producing bioslurry using high-concentration dissolved oxygen water solves the disadvantage of bioremediation, which requires a long period of time for purification. Purification can be performed in a period of about 2 to 1/3.

  Further, by injecting the high pressure in the lateral direction, the permeation range of the treated water at the time of injection is widened, so that the number of injection pipes can be reduced and the construction cost can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a method for obtaining a bioslurry having a high dissolved oxygen concentration. An oxygen cylinder 3 is connected to a mixer 1 for producing a bioslurry via an oxygen mixing pump 2. By forcibly supplying oxygen in the oxygen cylinder into the water supplied to the mixer 1 at the time of preparing the bioslurry, a high concentration of dissolved oxygen water is prepared, and a biopharmaceutical containing decomposing bacteria therein and its A nutrient source is added and mixed to obtain a bioslurry with a large amount of dissolved oxygen.

  As shown in FIG. 2, an injection tube 6 having a diameter of about 40 mm having a ground 4 to be improved with a boring machine 5 or the like and a horizontal spray nozzle 7 at the tip and a drilling nozzle at the tip. Is inserted into the soil 4 while spraying fresh water from the excavation nozzle at the tip, and is built to a predetermined depth, and the ball 8 is dropped into the injection pipe 6 to close the excavation slip. Next, the bio-slurry produced by the above method is pumped to the built-in injection pipe 6 by the ultrahigh pressure pump 9, and the injection pipe 6 is rotated by the boring machine 5 while the bio-slurry is injected 10 into the soil 4 from the injection nozzle 7. While raising the planned pulling speed. The preferred injection pressure is 20 to 40 megapascals, and the rotation speed of the injection tube during pulling is 3 to 10 revolutions per minute.

  While injecting bioslurry 10 to a predetermined depth, the injection tube 6 is pulled up, and the bioslurry is infiltrated into the ground at a desired diameter R and depth H shown in FIG. And repeat the above procedure.

Conceptual diagram showing a method for producing bioslurry with high dissolved oxygen concentration Conceptual diagram showing the work of installing the injection pipe into the ground Conceptual diagram showing the operation of injecting bioslurry into the ground

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mixer 2 Oxygen mixing pump 3 Oxygen cylinder 4 Ground 5 Boring machine 6 Injection pipe 7 Injection nozzle 9 Super high pressure pump

Claims (1)

  In a method for purifying contaminated soil, a bioslurry containing a microorganism having a function of decomposing pollutants contained in soil of the ground and a bioslurry containing its nutrients is injected from an injection pipe (6) built in the ground (4). Using a high-slurry bioslurry obtained by melting nutrients in water containing high-concentration oxygen, the bioslurry is sprayed laterally (10) from an injection tube (6) that has been built to a predetermined depth. A method for purifying contaminated soil, characterized in that a highly active bioslurry is permeated widely around the injection tube by pulling up the injection tube while rotating.

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