JP2007260611A - Method of cleaning contaminated soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of cleaning contaminated soil accomplishing shortening of a cleaning period. <P>SOLUTION: The method of cleaning the contaminated soil is provided with a soil heating step for pouring a steam into the soil G to heat it such that a temperature of the soil becomes 20-60°C and activating a microorganism in the soil G. Thereby, an activity of the microorganism in the soil G is enhanced and decomposition of the contamination substance by the microorganism is accelerated. As a result, shortening of the cleaning period of the soil can be accomplished. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for purifying contaminated soil in which soil contaminated with an organic compound is purified in situ.

  In recent years, interest in soil contamination accompanying industrial activities has increased, and the Soil Contamination Countermeasures Law has been enforced to reduce the impact of soil contamination. Benzene is the subject of regulation of the Soil Contamination Countermeasures Law, but countermeasures against oil films and oily odors from other petroleums are also desired for the purpose of preserving the living environment.

  Conventionally, techniques for purifying soil contaminated with volatile organic compounds (VOC) and the like include on-site processing and in-site processing. Examples of on-site treatment include heat treatment, chemical treatment, biological treatment, and extraction treatment. In-situ treatment includes extraction method, decomposition method, and washing method. Extraction methods include soil gas suction method, groundwater pumping method, and air sparging method. Decomposition methods include chemical treatment (oxidative decomposition, reductive decomposition). , Biological treatment (bioremediation, phytoremediation, etc.).

As a technique for purifying contaminated soil in-situ, there are those shown in the following patent documents. The in-situ purification method for contaminated soil described in the patent literature proposes a technology that purifies contaminated soil by supplying nutrient salts such as nitrogen and phosphorus to the contaminated soil and decomposing oil in the soil by the ability of microorganisms to decompose. Has been.
JP 2004-298830 A JP 2000-317436 A

  However, the conventional technique described in Patent Document 1 has a problem that the activity of microorganisms in the soil does not increase and the purification period becomes longer. The conventional technique described in Patent Document 2 has a problem that it takes time because the soil is sterilized and then purified.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a method for purifying contaminated soil in which the purification period is shortened.

  The method for purifying contaminated soil according to the present invention is a method for purifying contaminated soil in which soil contaminated with an organic compound is purified in situ using microorganisms, and the temperature of the soil is 20 to 60 ° C. by injecting steam into the soil. It is characterized by providing the soil heating process heated.

  According to such a purification method of contaminated soil, the activity of microorganisms in the soil can be improved by injecting steam into the soil and heating the soil to 20 to 60 ° C. Thereby, decomposition | disassembly of the pollutant by microorganisms is accelerated and the purification | cleaning period of soil can be shortened. In general, when the temperature of the soil is less than 20 ° C, the enzyme reaction rate required for the growth of microorganisms is low and the microorganisms cannot grow. When the temperature of the soil exceeds 60 ° C, the enzyme (protein) and the cell wall undergo thermal denaturation. Microorganisms cannot grow.

  Here, it is preferable to further include a supplying step of supplying nutrient salt and / or air into the soil. Thereby, nutrient salt and / or air are supplied in the soil, and the activity of microorganisms in the soil can be further improved.

  Moreover, it is preferable to perform the injection | pouring of the steam in a soil heating process, and the supply of the nutrient salt and / or air in a supply process using the same injection hole formed in soil. Accordingly, by making the injection hole for injecting steam the same as the injection hole for supplying nutrient salt and / or air, it is not necessary to form the injection holes separately, and the cost can be reduced. . The injection of steam and the supply of nutrient salt and / or air may be performed simultaneously or alternately.

  Moreover, it is preferable to further include a pumping process for pumping up groundwater in the soil and an aeration process for aeration of groundwater pumped from the soil. Thereby, groundwater can be purified by pumping up the groundwater in the soil and aeration of the pumped-up groundwater.

  Moreover, it is preferable to heat so that the temperature of soil may become 25-40 degreeC in a soil heating process. Thus, the activity of microorganisms in soil can be further improved by heating so that the temperature of soil may become 25-40 degreeC. In addition, when soil temperature is 25-40 degreeC, it becomes an environment suitable for growth of a general microorganism (room temperature microbe).

  According to the method for purifying contaminated soil of the present invention, the activity of microorganisms in the soil can be improved, so that the purification period can be shortened.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a preferred embodiment of a method for purifying contaminated soil according to the present invention will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted. FIG. 1 is a schematic configuration diagram illustrating a soil purification apparatus according to an embodiment of the present invention.

  The soil purification apparatus 1 is for purifying soil contaminated with an organic compound in situ, for example, and purifies the contaminated soil by decomposing the organic compound using the decomposition ability of microorganisms in the soil. is there. In the contaminated soil shown in FIG. 1, an unsaturated layer (non-aquifer) 2 is formed on the upper side of the groundwater level L, and a saturated layer (aquifer) 3 is formed on the lower side. A contamination layer 4 containing an organic compound is formed. Examples of the organic compound include petroleum oils such as volatile oil, kerosene, and light oil.

  The soil purification apparatus 1 includes a nutrient injection facility 5 that injects nutrient salts that activate microorganisms into soil G, an injection well (injection hole) 6 and a pumping well 7 that extend from the ground surface to the saturated layer 3, pumping water A purification facility 8 for purifying the groundwater pumped up through the well 7 is provided.

  A plurality of the injection wells 6 and 6 are formed around the contaminated layer (purification region) 4 in the soil G, and the pumping well 7 is formed at substantially the center of the contaminated layer 4.

  The nutrient salt injection facility 5 injects, for example, nutrient salts such as nitrogen and phosphorus (for example, an aqueous solution of nutrient salts) and air into the soil G. These nutrient salts and air are injected into the injection well 6. Is supplied to the saturated layer 3 via

  The purification facility 8 is connected to a pumping well 7 and pumps a pump 9 that pumps up groundwater, an oil / water separator 10 that separates oil from the pumped-up groundwater, and oil (recovered oil) is removed in the oil / water separator 10. An aeration tank 11 for aeration treatment of groundwater and an adsorption tower 12 for removing contaminants in the gas generated in the aeration tank 11 are provided.

  The aeration tank 11 is connected to the nutrient salt injection facility 5 and is supplied with nutrient salt and air. In addition, the aeration tank 11 is connected to the injection well 6 and is configured to be able to inject the aerated treated water into the soil G.

  Here, the soil purification apparatus 1 of the present embodiment includes a steam generating facility 13 that generates steam for heating the inside of the soil G, and a temperature measuring means 14 that measures the temperature of the soil. Then, the steam generated in the steam generating facility 13 is supplied into the soil G through the injection well 6.

  Next, a method for purifying oil-contaminated soil using the soil purification apparatus 1 configured as described above will be described. First, a soil heating process is performed in which steam is injected into the soil G through the injection wells 6 and 6 to heat the soil G. Here, the steam generated in the steam generating facility 13 is injected into the saturated layer 3 through the injection well 6 and heated so that the soil temperature becomes an appropriate temperature (20 to 60 ° C.). To activate. In addition, this "appropriate temperature of soil (20-60 degreeC)" is a temperature optimal for the activity of the microorganisms in soil, More preferably, it is 25-40 degreeC. Then, when the temperature of the soil is detected by the temperature measuring means 14 and reaches 20 to 60 ° C., the supply of steam is stopped.

  Next, a biotreatment process for decomposing organic compounds in the soil G by microorganisms is performed. In this biotreatment process, first, a supply process for supplying nutrient salts and air into the soil G is performed. In this supply process, nutrient salt and air are supplied into the saturated layer 3 through the injection wells 6 and 6 using the nutrient salt injection facility 5. Furthermore, a pumping process for pumping up ground water in the soil G is performed. In this pumping process, groundwater is pumped up using a pumping pump 9. Thereby, in the saturated layer 3, the hydrodynamic gradient which goes to the pumping well 7 from the injection well 6 is formed, nutrient salt and air can be supplied efficiently and the activity of microorganisms can be improved. Then, the pollutant can be efficiently decomposed by the microorganism having improved activity.

  The groundwater pumped up in the pumping process is treated by the purification process to remove contaminants. This purification process includes an oil / water separation process for separating and removing oil from groundwater, an aeration process for aeration treatment of groundwater from which oil has been removed, and a gas purification process for purifying gas generated by the aeration process. .

  In the oil / water separation step, oil in the groundwater is separated and removed using the oil / water separation tank 10, and the groundwater from which the oil has been removed is supplied to the aeration tank 11.

  In the aeration process, the aeration tank 11 is used for aeration treatment to purify the groundwater. At this time, nutrient salt and air are supplied to the aeration tank 11 by the nutrient salt injection facility. The purified treated water is reinjected into the soil G through the injection wells 6 and 6 together with the remaining nutrient salts. Thus, cost reduction is achieved by reusing the nutrient salt. Further, the gas generated during the aeration process is supplied to the adsorption tower 12.

  In the gas purification step, the pollutant in the gas is adsorbed and removed using an adsorption tower, and the gas from which the pollutant has been removed is exhausted to the atmosphere.

  Then, the biotreatment process and the purification process are continued until the contamination concentration in the soil G decreases to a predetermined value. Furthermore, a soil heating process is implemented according to soil temperature, and it is made for soil temperature to be 20-60 degreeC.

  According to such a method for purifying contaminated soil, steam can be injected into the soil and the temperature in the soil can be maintained at 20 to 60 ° C., so that the activity of microorganisms in the soil can be improved. . As a result, pollutants can be efficiently decomposed and the soil purification period can be shortened.

  Moreover, since the injection of the nutrient salt and air and the injection of steam are performed using the injection well 6, the injection well for injecting the nutrient salt and air and the injection well for the steam injection are installed separately. There is no need. As a result, cost reduction can be achieved.

  As mentioned above, although this invention was concretely demonstrated based on the embodiment, this invention is not limited to the said embodiment. In the said embodiment, although the groundwater pumped up is purified using the purification equipment 8, you may purify only in the ground, without pumping up groundwater. In short, the soil may be heated to 20-60 ° C. using steam to activate the microorganisms, and the contaminants may be decomposed in situ by the microorganisms in the soil.

  Moreover, in the said embodiment, although the aerated treated water is reinjected in soil, the method of not reinjecting treated water may be used.

  Moreover, in the said embodiment, although the nutrient salt and air are inject | poured in the supply process, what is necessary is just to supply either a nutrient salt or air.

It is a schematic block diagram which shows the soil purification apparatus which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Soil purification apparatus, 2 ... Unsaturation layer, 3 ... Saturation layer, 4 ... Contamination layer, 5 ... Nutrition salt injection equipment, 6 ... Injection well (injection hole), 7 ... Pumping well, 8 ... Purification equipment, 9 ... Pumping pump, 10 ... oil water separation tank, 11 ... aeration tank, 12 ... adsorption tower, 13 ... steam generating equipment, 14 ... temperature measuring means, G ... soil, L ... ground water level.

Claims (5)

In the purification method of contaminated soil, in which soil contaminated with organic compounds is purified in situ using microorganisms,
A method for purifying contaminated soil, comprising a soil heating step of injecting steam into the soil and heating the soil to a temperature of 20 to 60 ° C.   The method for purifying contaminated soil according to claim 1, further comprising a supplying step of supplying nutrient salt and / or air into the soil.   The injection of steam in the soil heating step and the supply of nutrient salt and / or air in the supply step are performed using the same injection hole formed in the soil. Purification method for contaminated soil. A pumping process for pumping groundwater in the soil;
The method for purifying contaminated soil according to any one of claims 1 to 3, further comprising an aeration step of aeration of groundwater pumped from the soil.   In the said soil heating process, it heats so that the temperature of the said soil may be 25-40 degreeC, The purification method of the contaminated soil as described in any one of Claims 1-4 characterized by the above-mentioned.

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