JP2007105595A - Contamination cleaning method for clay layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently restore a contamination substance such as oils and an organic chlorine based compound existing in a clay layer at an original position without requiring a large number of facilities or the like. <P>SOLUTION: In the contamination cleaning method for the clay layer, a division wall 5 is installed to a water-permeable layer 2 positioned at a lower part of the upper clay layer 1 contaminated with the contamination substance and a surfactant and a nutrition source of a microorganism are poured to the upper clay layer 1 in the division wall 5 at a high pressure to remove and elute the contamination substance from soil particles of the upper clay layer 1. Further, the removed and eluted contamination substance and the nutrition source are moved to the water-permeable layer 2 to promote microorganism decomposition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a soil purification technique for restoring in situ by utilizing the activities of microorganisms indigenous to underground areas contaminated with oils, organic chlorine compounds and the like.

  In the underground soil such as factory ruins, organic chlorine compounds represented by trichlorethylene, oils such as light oil and heavy oil, and other pollutants may be mixed. It is indispensable to proceed with the purification business of soil contaminated by these, and there is a demand for the development of a more reliable and low-cost purification technology.

  In particular, when the contaminated area is a clay layer (silt layer), the viscosity of the soil is high and there is no movement of moisture due to water flow in a saturated state. Furthermore, contaminants are strongly adsorbed between the soil particle surface and between the soil particles. For this reason, it has the subject that purification of a pollutant becomes more difficult.

  Conventionally, various methods for purifying contaminated soil have been developed. As typical methods for repairing a contaminated underground area in situ, there are the following methods.

  Ventilation air pressure that feeds ventilation air to contaminated areas contaminated with contaminants such as oil, dioxins, or volatile organic chlorine compounds, among the unsaturated low-permeability water-permeable layers that exist above the groundwater level. An inlet mechanism, a vibration applying mechanism that applies vibration to the contaminated area, and a gas processing facility that sucks the contaminants entrained in the aerated air together with the air. The vibration imparting mechanism comprises a shaft excavated up to the unsaturated hardly-permeable air-permeable layer and an exciter installed at the excavation bottom of the shaft, and the vibration is not generated by driving the exciter. This is a treatment method in which a contaminant is collected by applying to a contaminated region of a saturated hardly permeable air permeable layer (see, for example, Patent Document 1).

In addition, a water blocking wall is provided in a square shape in the soil so as to surround the contaminated soil. In a contaminated area surrounded by a water blocking wall, uncontaminated soil located on the surface is carried out in advance and temporarily placed. While adding necessary nutrients to the contaminated area 2, the contaminated soil and groundwater are agitated by a stirrer to form a mud, and a biochemical chemistry of the contaminated soil that ventilates the contaminated soil and simultaneously vents sufficiently. Purification method (for example, see Patent Document 2).
JP 2005-74276 A JP 2003-71430 A

  However, the one described in Patent Document 1 includes a ventilation air pressure insertion mechanism that sends ventilation air to the contaminated area, a vibration imparting mechanism (vibrator) that imparts vibration to the contaminated area, and contamination that is entrained in the aerated air. Many equipment configurations such as gas treatment equipment that sucks substances together with air and large equipment are required, and there is a problem that vibration measures are required.

  In addition, when applying vibration of the desired frequency by the vibrator to the contaminated area of the unsaturated permeable air permeable layer, the vibration propagation tends to vary depending on the situation of the underground contaminated part, and it adheres to the surface of the soil particles. In some cases, the peeling of the pollutant becomes insufficient, and it is difficult to completely suck the pollutant.

  Moreover, the thing of above-mentioned patent document 2 installs a water stop wall in the shape of a square in the soil, excavates and carries out non-contaminated soil located on the surface, agitation of contaminated soil and groundwater in the contaminated area, mud soil Large equipment such as heavy machinery for backfilling uncontaminated soil temporarily placed in the contaminated area after completion of clarification and purification is required, and there are many work processes.

  There is also a problem that a vast space for storing soil by excavation is required.

  The present invention solves the above-mentioned conventional problems, and restores pollutants such as oils and organochlorine compounds existing in the clay layer efficiently in situ without requiring many facilities. It is intended to do.

  A partition wall is installed up to the permeable layer located under the clay layer contaminated with the pollutant, and a surfactant and a nutrient source of microorganisms are injected into the clay layer in the partition wall at a high pressure, and the contaminant is put into the clay layer. It is a method for decontaminating a clay layer, characterized in that the pollutants and nutrients separated and eluted from the soil particles are moved to the water-permeable layer to promote microbial degradation.

  According to the present invention, pollutants such as oils and organochlorine compounds existing in the clay layer can be repaired efficiently in situ without requiring many facilities.

  1st invention sets a partition wall to the water-permeable layer located in the lower part of the clay layer contaminated with the pollutant, and puts a surfactant and a microbial nutrient source on the clay layer in the partition wall under high pressure (10 MPa) Contamination of clay layer by injecting and leaching pollutants from soil particles in clay layer, and further detaching and eluting pollutants and nutrients to permeable layer to promote microbial degradation This is a purification method.

  As a result, the contaminants that are strongly adsorbed between the soil particle surface and between the soil particles of the clay layer are desorbed and eluted from the surface of the soil particles and between the soil particles by the surfactant.

  Furthermore, the pollutants and nutrients that are released from the surface and between the soil particles of the clay layer are transferred to the permeable layer that is gravel soil.

  As a result, the growth and decomposition activity of microorganisms can be increased in the water permeable layer to promote the purification of contaminants.

  This is because the clay layer is composed of kaolin, bentonite, etc., and the soil particles (about 2 μm) are finer than the microorganisms, and it is difficult for the microorganisms to decompose the contaminants adhering to the gaps between the soil particles. It is.

  Moreover, the purification equipment can be further simplified.

  Furthermore, secondary pollution due to the elution of contaminants from the clay layer to the permeable layer can be prevented by the partition wall to the lower part of the permeable layer.

  The second invention is a method for decontaminating a clay layer according to the first invention, wherein the surfactant is lecithin and the nutrient source is stearic acid as a main component.

  As a result, lecithin and stearic acid are natural production substances, which can suppress adverse effects on the surrounding environment.

  Hereinafter, a clay layer contamination purification method according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a basic configuration diagram of a cross-sectional portion showing a clay layer contamination purification method according to an embodiment of the present invention.

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

  In the basic underground area consisting of the upper clay layer 1, the water permeable layer 2, and the lower clay layer 3 from the ground surface, oil, organic chlorine compounds, etc. are applied to the upper clay layer 1 or the boundary between the upper clay layer 1 and the water permeable layer 2. This is an example in which a contaminated area 4 exists. Heavy oil or the like that is a pollutant exists in a raw liquid state, or is adsorbed by soil or organic matter in the soil.

  The partition wall 5 is installed so as to surround the contaminated area 4 up to the water permeable layer 2 located below the upper clay layer 1 contaminated with the pollutant. The partition wall 5 located in the water permeable layer 2 is formed with a water permeable material or a large number of pores 5a. The upper end of the supply pipe 6 is opened in the upper clay layer 1 in the partition wall 5, and the other end of the supply pipe 6 is connected to a high-pressure pump 7 that is an injection means. Furthermore, the high-pressure pump 7 is connected to reservoirs 8 and 9 for lecithin as a surfactant and stearic acid as a nutrient source. Moreover, the observation well 10 is installed to the lower end of the permeable layer 2, and at least the contamination concentration of the permeable layer 2, the amount of nutrients, etc. are monitored.

  The high-pressure pump 7 injects the surfactant lecithin and the nutrient source stearic acid into the upper clay layer 1 through the supply pipe 6 at a pressure of 10 MPa, for example. As a result, the contaminants strongly adsorbed between the soil particle surfaces of the upper clay layer 1 and between the soil particles are separated from the surface of the soil particles and between the soil particles into the contained water and eluted by the surfactant.

  Furthermore, the contaminants and nutrients that have been separated and eluted from the surface of the upper clay layer 1 and between the soil particles are transferred to the permeable layer 2 that is gravel soil. As a result, in the water permeable layer 2, the growth and decomposition activity of microorganisms can be increased and the purification of contaminants can be promoted. Moreover, the purification equipment can be further simplified.

  By using lecithin as a surfactant and stearic acid as a nutrient source, since these are natural products, adverse effects on the surrounding environment can be suppressed. In addition, an observation well 10 is installed to the lower end of the permeable layer 2, and at least the contamination concentration and nutrient amount of the permeable layer 2 are monitored to optimize the surfactant and nutrient source supplied to the upper clay layer 1. Adjust.

  You may supply anaerobic microorganisms to the water-permeable layer 2 with a surfactant and a nutrient source as needed. This ensures that microorganisms are always secured in the water permeable layer, and that the contaminants can be reliably decomposed while maintaining the decomposition activity of the microorganisms by supplying nutrient sources.

  As described above, in the present invention, the partition wall 5 is installed up to the water permeable layer 2 located below the upper clay layer 1 contaminated with the pollutant, and the surfactant and the surfactant are placed on the upper clay layer 1 in the partition wall 5. Injecting nutrient sources of microorganisms at a high pressure, detaching and eluting pollutants from the soil particles of the upper clay layer 1, and further detaching and eluting contaminants and nutrient sources to the permeable layer 2 to promote microbial degradation. This is a method for purifying clay layer contamination.

  According to the present invention, the contaminants that are strongly adsorbed between the soil particle surface and between the soil particles of the clay layer are separated from the surface of the soil particles and between the soil particles by the surfactant, and are eluted. In addition, the contaminants and nutrients that are released from the surface and between the soil particles of the clay layer are transferred to the permeable layer, which is gravel soil. As a result, the growth and decomposition activity of microorganisms can be increased in the water permeable layer to promote the purification of contaminants.

  Moreover, the purification equipment can be further simplified.

  It can be applied to a wide range of uses in the purification of soil contaminated with harmful substances.

The basic block diagram of the cross-sectional part which shows the contamination purification method of the clay layer of one Example of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper clay layer 2 Permeable layer 3 Lower clay layer 4 Contaminated area 5 Partition wall 5a Pore 6 Supply pipe 7 High pressure pump 8 Storage container 9 Storage container 10 Observation well

Claims (2)

A partition wall is installed up to the permeable layer located under the clay layer contaminated with the pollutant, and a surfactant and a nutrient source of microorganisms are injected into the clay layer in the partition wall at a high pressure, and the contaminant is put into the clay layer. A method for decontaminating a clay layer, characterized in that the contaminants and nutrients separated and eluted from the soil particles are moved to the water-permeable layer to promote microbial degradation. The method of claim 1, wherein the surfactant is lecithin and the nutrient source is stearic acid.

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