JP2011050948A - Method and apparatus for purifying contaminated soil or groundwater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for purifying contaminated soil or groundwater which can increase a diffusion area of a fine bubble-containing liquid injected into soil contaminated with volatile organic compounds, such as benzene, and can promote the activation of microorganisms. <P>SOLUTION: A biosparging method using a fine bubble-containing liquid-containing water for purifying the volatile organic compounds in situ includes a process for forming a tubular injection well 12 in the contaminated soil 6, a process for supplying the fine bubble-containing liquid W to a wide area in the contaminated soil 6, and a process for sending air A into the contaminated soil 6 through the injection well 12 by an air sparging method. <P>COPYRIGHT: (C)2011,JPO&INPIT

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.

  Conventionally, as a method of purifying soil and groundwater contaminated with volatile organic compounds such as benzene and trichlorethylene, air is sent to the contaminated soil and groundwater to promote the vaporization of the pollutant and collect the gasified pollutant. An air sparging method is known (for example, see Patent Document 1). The air sparging method is a technique in which volatile substances are transferred from a liquid phase to a gas phase by sending air, and the volatile substance gas transferred to the unsaturated layer is purified by sucking with a blower. On the other hand, when oxygen is sufficiently supplied, it can be expected that aerobic microorganisms living in the soil are activated and the decomposition of the pollutants is promoted.

  The purification method of Patent Document 1 includes a sparging well in the ground containing groundwater contaminated with a volatile organic chlorine compound such as chlorinated ethylene, and contains a gas and a nutrient source (organic material) from the lower end of the sparging well. By injecting liquid toward the ground, it is possible to purify contaminated groundwater by removing and collecting pollutant gases by sparging, microbial treatment by supplying oxygen and nutrients, pumping treatment of contaminated groundwater by pumping wells, etc. is there.

  On the other hand, an oil-contaminated soil purification method that decomposes oil by the action of microorganisms is known (see, for example, Patent Document 2). The purification system of Patent Document 2 purifies soil by putting nutrient sources (decomposition promoting substances) and fine bubble-containing water into injection wells, respectively. 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.

JP 2009-45558 A JP 2009-6304 A

  In the conventional contaminated soil or groundwater purification method described in Patent Document 1 and the like described above, the gas injected into the contaminated soil is easy to move upward and hardly diffuses in the horizontal direction. In this case, as shown in FIG. 5, there is a possibility that a part P where the contaminants remain without being vaporized or decomposed may be formed in the horizontal region of the soil 6 saturated with the groundwater around the lower end 4 of the sparging well 2.

  The present invention is a method for purifying contaminated soil or groundwater that can expand the diffusion range of fine bubble liquid injected into soil contaminated with volatile organic compounds such as benzene and promote the activation of microorganisms. And an object to provide an apparatus.

  In order to achieve the object of preventing a portion where the pollutant remains without being vaporized or decomposed in the soil subjected to the soil purification, the method for purifying the contaminated soil or groundwater according to claim 1 of the present invention is provided. A biosparging method using water containing fine bubble liquid to purify volatile organic compounds in situ, forming a tubular injection well in the contaminated soil, and spreading the liquid containing the fine bubbles over a wide area in the contaminated soil And a step of feeding air into the contaminated soil through the injection well by an air sparging method.

  Further, in the method for purifying contaminated soil or groundwater according to claim 2 of the present invention, in the above-mentioned claim 1, the fine bubbles contained in the liquid are millibubbles, microbubbles having a diameter of 50 μm or less, and nanobubbles having a diameter of 1 μm or less. It is characterized by being.

  The method for purifying contaminated soil or groundwater according to claim 3 of the present invention is the method according to claim 1 or 2, wherein the liquid is decomposed by microorganisms living in the contaminated soil. It is characterized by being a liquid containing a nutrient source (degradation promoting substance) that promotes the process.

  Moreover, in the purification method of the contaminated soil or groundwater which concerns on Claim 4 of this invention, when manufacturing the said fine bubble in any one of Claims 1-3 mentioned above using gas, the said fine bubble It is characterized by collecting and reusing unused gas that has not been used in the production of the above.

  In addition, the method for purifying contaminated soil or groundwater according to claim 5 of the present invention is the method according to any one of claims 1 to 4, wherein a plurality of injection wells having different depth positions of injection ports are formed in the contaminated soil. It is characterized by that.

  Further, the contaminated soil or groundwater purification apparatus according to claim 6 of the present invention is a biosparging method using fine bubble liquid-containing water for purifying volatile organic compounds in situ, and a tubular injection well provided in the contaminated soil A fine bubble liquid generating means for generating a liquid containing fine bubbles, a liquid supply means for feeding the liquid containing the fine bubbles generated by the fine bubble liquid generating means into the contaminated soil, and the air by the air sparging method. And means for feeding into the contaminated soil through the injection well.

  In addition, the contaminated soil or groundwater purification apparatus according to claim 7 of the present invention is not used for producing the fine bubbles in the above-described claim 6 when producing the fine bubbles using gas. A gas recovery mechanism for recovering and reusing unused gas is further provided.

  Further, the contaminated soil or groundwater purification apparatus according to claim 8 of the present invention is characterized in that, in the above-described claim 6 or 7, a plurality of the injection wells having different inlet depth positions are provided in the contaminated soil. To do.

  According to the present invention, there is a biosparging method using fine bubble liquid-containing water that purifies volatile organic compounds in situ, the step of forming a tubular injection well in contaminated soil, and the contamination of the liquid containing the fine bubbles A step of supplying a wide range in the soil, and a step of feeding air into the contaminated soil through the injection well by an air sparging method. Since liquid containing fine bubbles can be injected and air can be injected into the contaminated soil by the air sparging method, the diffusion range of the liquid and air injected into the soil can be widened.

  Moreover, since the amount of dissolved oxygen in the groundwater increases by injecting a liquid containing fine bubbles and air together in the contaminated soil, activation of aerobic microorganisms that inhabit the soil can be promoted. . Accordingly, a wide range of contaminated soil or groundwater contaminated with volatile organic compounds such as benzene can be efficiently purified.

FIG. 1 is a side sectional view showing Example 1 of a purification apparatus for contaminated soil or groundwater according to the present invention. FIG. 2 is a diagram showing an example of the relationship between the diameter and number of fine bubbles used in the present invention. 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. FIG. 5 is a conceptual diagram of the conventional state of purification of contaminated soil or groundwater. FIG. 6 is a perspective view showing Example 2 of the purification apparatus for contaminated soil or groundwater according to the present invention. FIG. 7 is a perspective view showing a conventional contaminated soil or groundwater purification device. FIG. 8: is a sectional side view which shows Example 3 of the purification apparatus of the contaminated soil or groundwater which concerns on this invention. FIG. 9 is a side sectional view showing a conventional contaminated soil or groundwater purification device.

  Hereinafter, embodiments (Examples 1 to 3) of a purification method and apparatus for 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.

[Example 1]
As shown in FIG. 1, a contaminated soil or groundwater purification apparatus 100 (hereinafter simply referred to as “purification apparatus”) 100 according to Embodiment 1 of the present invention is a tubular injection well 12 provided in soil 6 containing contaminated groundwater. And a liquid supply device 18 that supplies water containing fine bubbles to the soil 6 through the injection well 12 and a gas supply device 14 that supplies air A, and volatilizes benzene, oil, etc. in the contaminated soil 6 or groundwater. The organic compound is purified in situ by a biosparging method using water containing fine bubble liquid.

  This purification device 100 supplies a fine bubble liquid generation device 16 (fine bubble liquid generation means) that generates a liquid W (fine bubble-containing liquid) containing fine bubbles, and supplies the liquid W to the soil 6 through the injection well 12. A liquid supply device 18 (liquid supply means).

  The injection well 12 has an inner diameter capable of supplying the liquid W and the air A necessary for the purification of the contaminated soil 6 or the groundwater, and is constituted by a tubular body having an opening near the lower end thereof. The opening 20 is provided with a screen 20 that allows ventilation and water flow, and prevents intrusion of earth and sand into the injection well 12 while allowing supply of liquid W and air A from the injection well 12 to the soil 6. It is said. In addition, a liquid supply pipe 24 of the liquid supply device 18 and an air supply pipe 22 of the gas supply device 14 are connected to the upper end of the injection well 12. The injection well 12 is not limited to a steel pipe, and may be made of other materials as long as it is a tubular body that can supply the liquid W and air A into the contaminated soil 6.

  The liquid supply device 18 feeds the liquid W containing the fine bubbles generated from the fine bubble discharge nozzle 43 which is generated by the fine bubble liquid generation device 16 and is installed in the fine bubble-containing nutrient solution storage tank 42. It consists of a liquid feed pump 36 for feeding out to the air and a control unit 37. A valve 38 for adjusting the amount of liquid W to be supplied and a liquid amount sensor 40 are provided at predetermined positions of the liquid feeding pipe 24.

  The gas supply device 14 is for supplying air A into the contaminated soil 6 through the injection well 12, and is disposed on the ground surface 8. The gas supply device 14 includes a compressor 28 that pumps the air A to the air supply pipe 22. A valve 30, a flow sensor 32, and a pressure sensor 34 for adjusting the amount of air A to be supplied are provided at predetermined positions of the air supply pipe 22.

  The control unit 37 detects the supply start timing at which the supply of the liquid W from the liquid feed pump 36 is started immediately before supply, and starts the pressure feeding of the air A from the gas supply device 14 according to the detected supply start timing. This is for controlling the drive timing. The controller 37 can also control the operation of the compressor 28 and the opening / closing operation of the valve 30.

  The fine bubble liquid generator 16 is for generating a liquid W (microbubble-containing liquid) including millibubbles, microbubbles, and nanobubbles as fine bubbles, and is disposed on the ground surface 8. Here, the fine bubbles contained in the liquid W used in the present invention are millibubbles, microbubbles having a diameter of 50 μm or less, and nanobubbles having a diameter of 1 μm or less. For example, as shown in FIG. 2, 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, groundwater, etc. can be used as a liquid raw material.

  The characteristics of fine bubbles having a diameter of 50 μm or less are (1) the rising speed in water is slower than normal bubbles (several mm to 50 μm), (2) the pressure inside the bubbles is high, (3) gas-liquid It is known that the area is large and (4) the bubble surface is negatively charged (see the reference "the latest technology of fine bubbles, Takahashi et al., NTS, 2006"). In particular, the fine bubbles are characterized by shrinking in water and eventually disappearing or existing in water for a long time. In contrast, normal bubbles are characterized by rising in water and bursting at the surface of the water.

  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").

The operation and action of the above configuration will be described.
When the liquid feed pump 36 is driven, the liquid W containing the fine bubbles composed of microbubbles and millibubbles discharged from the fine bubble discharge nozzle 43 of the fine bubble-containing nutrient solution storage tank 42 is injected via the liquid supply pipe 24 into the injection well 12. Sent out. The supply start timing for starting the supply of the liquid W is detected by the control unit 37 immediately before the supply, and the control unit 37 can send the liquid W simultaneously into the contaminated soil 6, and the air The drive timing of the compressor 28 is controlled so that A is pumped into the contaminated soil 6.

  When the compressor 28 is driven, the air A is sent into the injection well 12 through the air supply pipe 22. Thus, the liquid W and air A simultaneously fed into the injection well 12 are injected into the contaminated soil 6 from the screen 20 at the lower end.

  In this way, when the liquid A containing fine bubbles is sent into the contaminated soil 6 by the air sparging method, the air A and the oxygen contained in the fine bubbles reach by simultaneously injecting the air A. (The radius of influence in the horizontal direction around the injection well 12) can be increased. For this reason, as shown in FIG. 5, the part P which a contaminant does not vaporize or decompose | disassemble in the horizontal area | region of the soil 6 surrounding the lower end 4 of the sparging well 2 which was difficult with the conventional air sparging method is made. Can be prevented.

  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. Therefore, a wide range of contaminated soil or groundwater contaminated with volatile organic compounds such as benzene can be efficiently purified in a shorter period of time than when only the conventional air sparging method is applied.

  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 W containing fine bubbles is injected into the injection well 12 provided in the soil composed of the silt layer, the saturated layer, and the unsaturated layer, the liquid W (nutrient) containing fine bubbles is applied to the soil. Since the supply area becomes large, 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 air 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 is increased due to the need to constantly supply air and gas recovery equipment that extracts pollutants.

  In the above-described embodiment, the depth of the injection well 12 is not limited as long as the liquid W and the air A can be reliably supplied to the contaminated soil 6 or the contaminated groundwater. Further, the number of the injection wells 12 is not limited to one, but the reach distance of the air A and the liquid W from the injection well 12 (range of influence of air sparging), the range to be purified, the air A and the liquid W It can be set as appropriate according to the injection amount, injection pressure, and the like.

[Example 2]
Next, Example 2 will be described.
As described above, Example 1 of the present invention activates aerobic microorganisms by injecting water containing fine bubbles into soil and decomposes volatile organic compounds such as benzene and oil. When air is used as a raw material for fine bubbles, an apparatus configuration as shown in FIG. 7 can be used.

  The apparatus of FIG. 7 includes a microbubble-containing water storage tank 42 a, a storage water tank 50, a nutrient solution storage tank 60, and an air storage tank 62. Water from the storage tank 50 is sent to the fine bubble-containing water storage tank 42 a via the pump 48. The air from the air storage tank 62 is sent from the path 52 to the fine bubble discharge nozzle 43 in the fine bubble-containing water storage tank 42a via the valve 64c and the fine bubble liquid generator 16. The nutrient solution from the nutrient solution storage tank 60 is mixed with the minute bubble-containing water in the minute bubble-containing water storage tank 42a via the valve 64a or 64b, and is sent to an injection well (not shown) by the liquid feed pump 36 and the liquid feed pipe 24. It is done. In addition, the fine bubble liquid production | generation apparatus 16 receives supply of the water from the storage tank 50 through the path | route 54 and the valve | bulb 64e.

  In the apparatus configuration shown in FIG. 7, a relatively expensive special gas such as pure oxygen can be used instead of air in order to increase the dissolved oxygen concentration. In this case, the use efficiency of the special gas is increased. It is preferable.

  Therefore, the contaminated soil or groundwater purification apparatus 200 according to the second embodiment of the present invention is configured to circulate the special gas in the apparatus in order to increase the use efficiency of the expensive special gas. That is, as shown in FIG. 6, the purification device 200 includes a microbubble-containing water storage tank 42 a, a storage water tank 50, a nutrient solution storage tank 60, a special gas storage tank 46, and a gas recovery mechanism 44. Prepare. The difference from the apparatus configuration of FIG. 7 is that a gas recovery mechanism 44 is provided and a special gas storage tank 46 is provided instead of the air storage tank 62. The gas recovery mechanism 44 includes a lid 58 and a circulation path 56 having a valve 64d.

  As shown in FIG. 6, the water from the storage tank 50 is sent to the fine bubble-containing water storage tank 42 a via the pump 48. The special gas from the special gas storage tank 46 is sent from the path 52 to the fine bubble discharge nozzle 43 in the fine bubble-containing water storage tank 42a via the valve 64c and the fine bubble liquid generator 16. The nutrient solution from the nutrient solution storage tank 60 is mixed with the fine bubble-containing water in the fine bubble-containing water storage tank 42a via the valve 64a or 64b, and is sent to the injection well (not shown) by the liquid feed pump 36 and the liquid feed pipe 24. It is done. In addition, the fine bubble liquid production | generation apparatus 16 receives supply of the water from the storage tank 50 through the path | route 54 and the valve | bulb 64e.

  The lid 58 is for preventing volatilization of the special gas in the fine bubble-containing water storage tank 42a, and covers the upper part of the tank 42a. The circulation path 56 passes through the lid 58 and communicates with the fine bubble-containing water storage tank 42a. Unused gas volatilized in the microbubble-containing water storage tank 42a without being used for the production of microbubbles is recovered through the path 56 and returned to the inlet side of the microbubble liquid generator 16, and then in the path 52. It is sent to the fine bubble discharge nozzle 43 and reused for producing fine bubbles.

  According to the second embodiment, when the special gas is used as the raw material for producing fine bubbles, the unused gas that has been volatilized without being used for production is recovered by the gas recovery mechanism 44 including the lid 58 and the path 56. Since it is reused, the use efficiency of special gas is increased. For this reason, the fine bubble which consists of expensive special gas can be manufactured at comparatively low cost.

[Example 3]
Next, Example 3 will be described.
Conventionally, as shown in FIG. 9, fine bubble-containing water from the nutrient solution storage tank 60 and the fine bubble-containing nutrient solution storage tank 42 is injected into the soil 6 through the screen 20 provided on the outer periphery of the injection well 12. It was. In this case, there is a concern that the liquid to be injected into the soil does not spread evenly in the horizontal and vertical directions as the depth of the injection depth increases.

  Therefore, in the contaminated soil or groundwater purification apparatus 300 according to the third embodiment of the present invention, as shown in FIG. 8, a plurality of injection wells 12 having the inlet 66 at the lower portion are changed (see FIG. 8). Then there are three). The injection amount and injection pressure for each injection port 66 can be changed by a control device (not shown). For this reason, if each injection amount and pressure are appropriately adjusted, the water containing fine bubbles can be evenly distributed in the soil 6 through the injection ports 66. By evenly diffusing the fine bubbles in the soil, oxygen consumption by the aerobic microorganism is promoted, and the surrounding soil can be efficiently purified.

  In addition, it can respond to the size of the width | variety of the purification | cleaning object depth by increasing / decreasing the number of the injection wells 12. FIG. For example, when the width of the purification target depth is large, the number of injection wells 12 may be increased.

  As described above, according to the present invention, a biosparging method using fine bubble liquid-containing water that purifies volatile organic compounds in situ, the step of forming a tubular injection well in contaminated soil, and the fine bubbles And a step of supplying air to the contaminated soil through an injection well by an air sparging method. Since liquid containing fine bubbles can be injected and air can be injected into the contaminated soil by the air sparging method, the diffusion range of the liquid and air injected into the soil can be widened.

  Moreover, by injecting fine bubbles into the contaminated soil, the amount of dissolved oxygen in the soil interstitial water increases, and the activation of in situ microorganisms is promoted. For this reason, the influence range of the gas inject | poured into soil can be expanded, and also the activation of the aerobic microbe which inhabits in situ can be promoted. Accordingly, a wide range of contaminated soil or groundwater contaminated with volatile organic compounds such as benzene can be efficiently purified.

  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, soil contaminated with volatile organic compounds such as benzene. It is suitable for the air sparging method using fine bubble-containing water that aerobically purifies the groundwater and groundwater.

2 Sparging well 6 Soil 8 Surface 12 Injection well 14 Gas supply device 16 Fine bubble liquid generator (fine bubble liquid generator)
18 Liquid supply device (liquid supply means)
DESCRIPTION OF SYMBOLS 20 Screen 22 Air supply pipe 24 Liquid supply pipe 28 Compressor 30 Valve 32 Flow rate sensor 34 Pressure sensor 36 Liquid supply pump 37 Control part 38 Valve 40 Liquid quantity sensor 42 Fine bubble containing nutrient storage tank 43 Fine bubble discharge nozzle 44 Gas recovery mechanism 66 Inlet 100 Purification equipment for contaminated soil or groundwater (Example 1)
200 Contaminated soil or groundwater purification equipment (Example 2)
300 Purification equipment for contaminated soil or groundwater (Example 3)
W Liquid A Air

Claims (8)

It is a biosparging method with fine bubble liquid-containing water that purifies volatile organic compounds in situ,
Forming a tubular injection well in the contaminated soil;
Supplying a liquid containing the fine bubbles to a wide area in the contaminated soil;
A method for purifying contaminated soil or groundwater, comprising a step of sending air into the contaminated soil through the injection well by an air sparging method.   The method for purifying contaminated soil or groundwater according to claim 1, wherein the fine bubbles contained in the liquid are millibubbles, microbubbles having a diameter of 50 μm or less, and nanobubbles having a diameter of 1 μm or less.   The said liquid is a liquid containing the nutrient source (degradation promoting substance) which accelerates | stimulates decomposition | disassembly of the said volatile organic compound by the microorganisms which inhabit the said contaminated soil. Methods for purifying contaminated soil or groundwater.   When producing the said microbubble using gas, the collection | recovery and reuse of the unused gas which was not utilized for manufacture of the said microbubble are performed. The contaminated soil or groundwater purification method described.   The method for purifying contaminated soil or groundwater according to any one of claims 1 to 4, wherein a plurality of the injection wells having different depth positions of the inlet are formed in the contaminated soil. It is a biosparging method with fine bubble liquid-containing water that purifies volatile organic compounds in situ,
Tubular injection well provided in the contaminated soil, fine bubble liquid generating means for generating liquid containing fine bubbles, and liquid supply means for feeding the liquid containing fine bubbles generated by the fine bubble liquid generating means into the contaminated soil And a device for purifying contaminated soil or groundwater, characterized by comprising means for sending air into the contaminated soil through the injection well by an air sparging method.   The gas recovery mechanism according to claim 6, further comprising a gas recovery mechanism that recovers and reuses unused gas that has not been used for manufacturing the microbubbles when the gas is used to manufacture the microbubbles. Purification equipment for contaminated soil or groundwater.   The apparatus for purifying contaminated soil or groundwater according to claim 6 or 7, wherein a plurality of the injection wells having different depth positions of the inlet are provided in the contaminated soil.

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