JP4257781B2 - Purification method for underground soil contaminated with organochlorine compounds - Google Patents

Description

  The present invention relates to a method for purifying underground soil contaminated with an organic chlorine compound such as trichlorethylene or tetrachloroethylene so as to remove the organic chlorine compound which is the contaminant.

In Patent Document 1 as a prior art, as a method for removing an organic chlorine compound contained as a pollutant in underground soil, anaerobic microorganisms in the underground soil are used, and the anaerobic microorganisms are used to It describes that chlorine compounds can be decomposed and removed.
JP 2002-224659 A

  This method according to the prior art activates anaerobic microorganisms in the underground soil by supplying nutrients thereto, but the purification treatment is exclusively for anaerobic microorganisms in the underground soil. Therefore, there is a problem that the capacity of the purification treatment here is considerably low.

  To improve this, groundwater in underground soil contaminated with organochlorine compounds is pumped from the underground soil to the ground, and a large amount of air is blown into the ground. It has been proposed to remove the organic chlorine compound contained therein and return the treated water after the bubbling (aeration) treatment to the underground soil as groundwater again.

  According to this method, the purification treatment can be performed by separating the treatment by bubbling (aeration) on the ground and the treatment by anaerobic microorganisms in the ground. Can be promoted.

  However, on the other hand, the treated water after the bubbling (aeration) treatment has a large amount of oxygen dissolved by the bubbling (aeration), in other words, a large amount of dissolved oxygen. Is returned to the underground soil as it is because some anaerobic microorganisms are killed by the amount of dissolved oxygen and the activation of the anaerobic microorganisms is reduced. Processing will be greatly reduced.

  Moreover, the treated water after bubbling (aeration) treatment of the groundwater pumped up from the underground soil contaminated with the organic chlorine compound is described in, for example, Japanese Patent Application Laid-Open No. 2002-316050 or Japanese Patent Application Laid-Open No. 2003-80074. As described above, it is conceivable to promote decomposition and treatment of the organochlorine compound with the iron powder by adding the iron powder and then returning to the underground soil. Most of the iron powder that is produced becomes iron oxide by reaction with a large amount of dissolved oxygen, and this iron oxide is mixed with groundwater together with the treated water. Not only will clogging occur, but the decomposition of organochlorine compounds by iron powder will be reduced.

  This invention makes it a technical subject to provide the purification method which eliminated these problems.

In order to achieve this technical problem, claim 1 of the present invention provides:
“Groundwater pumped up from underground soil contaminated with organochlorine compounds is supplied into an evaporator maintained at a reduced pressure lower than atmospheric pressure and boiled or evaporated, or the groundwater is reduced to a reduced pressure lower than atmospheric pressure . Supply to the deaeration can that has been held and deaerate, then add the treated water discharged from the evaporation can or the treated water discharged from the deaerator to the nutrients of anaerobic microorganisms After that, it is returned to a location away from the location where the groundwater is pumped out of the underground soil. "
It is characterized by that.

Moreover, claim 2 of the present invention is characterized in that "in the description of claim 1, iron powder is added to the treated water returned to the underground soil."

  By supplying the groundwater pumped up from the underground soil contaminated with organochlorine compounds into an evaporator maintained at a reduced pressure below atmospheric pressure and boiling and evaporating, the organochlorine compounds contained in this groundwater are boiled and evaporated. It is gasified together with the water vapor to be separated from the groundwater, and oxygen that is dissolved in this groundwater, that is, dissolved oxygen, is also gasified with water vapor by boiling evaporation under reduced pressure and separated from the groundwater Therefore, the treated water discharged from the evaporator is in a state where the content of the organic chlorine compound is extremely low and the amount of dissolved oxygen is also extremely low.

In addition, by supplying the groundwater pumped up from the underground soil contaminated with organochlorine compounds into a degassing can kept at a reduced pressure lower than atmospheric pressure, the organochlorine compounds contained in this groundwater Is separated from the groundwater by gasification along with the generation of bubbles, and dissolved oxygen in this groundwater is also gasified along with the generation of bubbles by degassing under reduced pressure and separated from the groundwater. The treated water discharged from the water is in a state where the content of the organic chlorine compound is remarkably low and the amount of dissolved oxygen is also remarkably low.

  In this case, before supplying the groundwater pumped up from the underground soil into the deaeration can kept under reduced pressure, the deaeration in the reduced pressure state becomes more intense by dissolving the gas such as air in the groundwater in advance. , The separation of the organochlorine compound can be further promoted.

  Therefore, the treated water after boiling or evaporating or deaerating in a reduced pressure state is in a state where the dissolved oxygen is remarkably low. Therefore, after adding the nutrient for anaerobic microorganisms to the treated water, By returning the ground soil to a location away from the location where the ground water is pumped up, the anaerobic microorganisms in the underground soil can be reliably activated under a state where the death of the anaerobic microorganisms due to dissolved oxygen can be reduced.

  The activation of the anaerobic microorganisms in the ground soil proceeds in order from the groundwater return point to the pumping point by allowing the groundwater in the ground soil to flow toward the pumping point. It will spread to the whole.

That is, according to the present invention, the organic chlorine compound is contaminated with the organic chlorine compound by evaporation or degassing of the groundwater pumped from the underground soil contaminated with the organic chlorine compound and reliable activation of the anaerobic microorganisms in the underground soil. It has the effect of greatly improving the purification treatment of underground soil.

  In this case, as described in claim 2, by adding iron powder to the treated water returned to the underground soil, the iron powder is oxidized because the amount of dissolved oxygen in the treated water is extremely small. As a result, almost all of them combine with chlorine (halogen elements) in the organic chlorine compound to decompose the organic chlorine compound in a state where clogging due to iron oxide is low in the underground soil. There exists an advantage which can further improve the purification process of the underground soil contaminated with the said organic chlorine compound.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a first embodiment.

  In the first embodiment, two wells 2 and 3 are separated from each other by an appropriate distance on the ground 1 in which the underground soil is contaminated with an organic chlorine compound such as trichlorethylene or tetrachlorethylene. Is excavated to a depth that reaches a portion deeper than the water surface 1a of the groundwater in the underground soil.

  Groundwater in the underground soil is pumped up by a pump 5 through a pipe line 4 loaded in one of the wells 2 and 3, and the temperature of the groundwater is about 15 ° C. Therefore, after heating to an appropriate temperature by the heating means 6b using steam or electricity from the boiler as a heat source, the inside is sealed and kept at a reduced pressure lower than the atmospheric pressure by a vacuum generation source such as the vacuum pump 7. By evaporating from the nozzle 6 a into the evaporator 6, the liquid evaporates in the evaporator 6.

  By this boiling evaporation, the organic chlorine compound such as trichlorethylene or tetrachloroethylene contained in the ground water is gasified together with the water vapor boiling and evaporated and separated from the ground water.

  In addition, since oxygen dissolved in the ground water, that is, dissolved oxygen, is gasified together with water vapor by the boiling evaporation and separated from the ground water, the discharge pipe 8 in the evaporator 6 is separated from the ground water. , The treated water in which the content of the organic chlorine compound is remarkably small and the amount of dissolved oxygen is remarkably small is discharged.

  A condenser 9 is provided between the evaporator 6 and a vacuum generation source such as a vacuum pump 7 for cooling and condensing water vapor generated by boiling evaporation, and the vacuum. The gas discharged from the vacuum generation source such as the pump 7 is condensed in the condenser 9 and then discharged into the atmosphere. Since this gas contains an organic chlorine compound, this gas is configured to be released into the atmosphere via a means for removing the organic chlorine compound (for example, a means for decomposing and removing by combustion).

  Then, the treated water discharged from the evaporator 6 through the discharge pipe 8 is used as a nutrient for anaerobic microorganisms (for example, butyric acid, lactic acid, ethanol, etc.) present in the underground soil from the pipe 10. After adding an appropriate quantity, it pressurizes with the pump 11 and supplies it to the bottom part in the said other well 3 via the pipe line 12, It returns to the groundwater in the said underground soil.

  Thereby, as shown by the arrow A, a flow in a direction from the other well 3 to the one well 2 is generated in the groundwater in the underground soil.

  From the fact that the treated water returned from the other well 3 to the groundwater in the underground soil is in a state in which the amount of dissolved oxygen is remarkably small and a nutrient for anaerobic microorganisms is added thereto. The anaerobic microorganisms in the underground soil can be reliably activated in a state where there is little killing of the anaerobic microorganisms by dissolved oxygen.

  And the activation of the anaerobic microorganisms in the underground soil pumps the groundwater from the other well 3 where the treated water in the evaporator 6 is returned to the groundwater, that is, the direction of the groundwater flow indicated by the arrow A. It will proceed in order toward the well 2, and will eventually spread to the entire area between the wells 2 and 3, so that the purification of underground soil contaminated with organochlorine compounds can be performed at a high speed. It can be achieved with certainty.

  Further, an appropriate amount of iron powder is added from the conduit 13 to the treated water discharged from the evaporator 6 through the discharge conduit 8.

  Then, this iron powder is mixed with the groundwater in a state in which the amount of dissolved oxygen in the treated water to which it is added is extremely small, hardly oxidized, and in the state where clogging due to iron oxide is small in the underground soil, Almost all of them combine with chlorine (halogen element) in the organic chlorine compound in the groundwater to decompose the organic chlorine compound, so that the purification treatment of the underground soil can be further promoted.

  FIG. 2 shows a second embodiment.

  In the second embodiment, the ground water pumped from the one well 2 through the pipe 4 by the pump 5 in the first embodiment is boiled and evaporated as in the first embodiment. Instead, the inside of the deaeration can 14 is ejected from the nozzle 14a into the deaeration can 14 that is sealed inside and maintained at a reduced pressure lower than the atmospheric pressure by a vacuum generation source such as a vacuum pump 15. Degas with.

  By this deaeration, organochlorine compounds such as trichlorethylene or tetrachloroethylene contained in the groundwater are gasified together with the generated bubbles and separated from the groundwater.

  In addition to this, oxygen that is present in the state of being dissolved in the groundwater, that is, dissolved oxygen is also gasified by the deaeration and separated from the groundwater. From the discharge pipe 16 in the deaeration can 14, The treated water in a state where the content of the organic chlorine compound is remarkably small and the amount of dissolved oxygen is remarkably small is discharged.

  In this case, before supplying the groundwater pumped up by the pump 5 to the degassing can 14, a gas such as air blown from the pipe line 17 is dissolved in advance in the degassing can 14. Since the deaeration in the reduced pressure state becomes more intense, the separation of the organic chlorine compound can be further promoted.

  And the treated water discharged | emitted from the said deaeration can 14 through the discharge pipe 16 is used as the nutrient for anaerobic microorganisms which exist in the said underground soil from the pipe 10 (for example, butyric acid, lactic acid, ethanol, etc.) After adding an appropriate amount, the pressure is increased by the pump 11 and supplied to the bottom of the other well 3 through the pipe 12 to return to the groundwater in the underground soil.

  Thereby, as shown by the arrow A, a flow in a direction from the other well 3 to the one well 2 is generated in the groundwater in the underground soil.

  From the fact that the treated water returned from the other well 3 to the groundwater in the underground soil is in a state in which the amount of dissolved oxygen is remarkably small and a nutrient for anaerobic microorganisms is added thereto. The anaerobic microorganisms in the underground soil can be reliably activated in a state where there is little killing of the anaerobic microorganisms by dissolved oxygen.

  Then, the activation of the anaerobic microorganisms in the ground soil pumps up the groundwater from the other well 3 where the treated water in the deaeration can 14 is returned to the groundwater in the direction of the groundwater flow indicated by the arrow A. Since it progresses in turn toward one well 2 and eventually spreads to the entire area between the two wells 2 and 3, the remediation of the underground soil contaminated with organochlorine compounds can be performed at a high speed. This can be achieved reliably.

  In the second embodiment, as in the case of the first embodiment, an appropriate amount of iron powder is added from the pipeline 13 to the treated water discharged from the degassing can 14. It goes without saying that it may be returned to the groundwater in the underground soil.

  Also in the second embodiment, since the gas discharged from the vacuum generation source such as the vacuum pump 15 contains an organic chlorine compound, the gas is removed from the organic chlorine compound removing means ( For example, it is configured to be released into the atmosphere through a means for decomposing and removing by combustion.

It is a figure which shows 1st Embodiment in this invention. It is a figure which shows 2nd Embodiment in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground 1a Groundwater surface 2 One well 3 The other well 6 Evaporator 7,15 Vacuum pump 14 Deaeration can

Claims (2)

Groundwater pumped up from underground soil contaminated with organochlorine compounds is supplied to an evaporator that is kept at a reduced pressure lower than atmospheric pressure to evaporate to boiling, or the groundwater is held at a reduced pressure lower than atmospheric pressure. The deaerated can was supplied to the deaerated can and deaerated, and then the treated water discharged from the evaporation can or the treated water discharged from the deaerated can was added with nutrients for anaerobic microorganisms. A method for purifying underground soil contaminated with organochlorine compounds, wherein the soil is returned to a location away from the location where the groundwater is pumped.
  The method for purifying underground soil contaminated with an organochlorine compound according to claim 1, wherein iron powder is added to the treated water returned to the underground soil.

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