JPWO2015046416A1 - Method for modifying contaminated soil - Google Patents

Abstract

[PROBLEMS] To improve the contaminated soil using microorganisms, while preventing the degradation of the decomposition performance of microorganisms generated in combination with activated carbon, and exhibiting the adsorptive power possessed by activated carbon, stably and continuously There has been a demand for a method for improving contaminated soil for purification. The method for modifying contaminated soil according to the present invention comprises a microorganism present in the contaminated soil and / or a microorganism newly mixed in the contaminated soil, a powdery porous carbon material, and a nutrient. It is characterized by using. [Selection] Figure 1

Description

The present invention relates to a method for modifying contaminated soil contaminated with oil, volatile organic compounds (VOC), benzene, cyanide compounds, dichloro compounds and the like.
More specifically, by using a powdery porous carbon material (especially a porous carbon material having a specific specific surface area and particle size), the oily odor and oil film can be adsorbed quickly by the adsorption ability of the porous carbon material. The present invention relates to a method capable of modifying contaminated soil without reducing the ability of microorganisms to contaminate the contaminated soil (especially oil).

  Conventionally, there is known a method for modifying contaminated soil in which contaminated soil contaminated with oil or the like is modified using microorganisms, activated carbon, or the like. For example, in Patent Document 1, a microbial activator for activating microorganisms present in contaminated soil is supplied to the contaminated soil together with activated carbon, and the activated microorganisms are grown on the surface of the activated carbon to improve the contaminated soil. A method for modifying contaminated soil that performs quality is disclosed.

JP 2008-221167 A

Here, in the conventional method for modifying contaminated soil represented by Patent Document 1, activated carbon is usually used for the purpose of more effectively expressing the ability as an adsorbent.
However, since the powdery activated carbon used conventionally has too strong adsorption capacity, most of the pollutants are adsorbed on the activated carbon before the decomposition of the pollutants in the contaminated soil by microorganisms begins. This prevents microorganisms in the contaminated soil from coming into contact with the pollutants, which prevents the spread of oily odor and oil film, but delays the decomposition of the pollutants by the microorganisms, resulting in stable soil modification. There was a problem of disappearing.

  Also, in the conventional method for modifying pollutants using activated carbon, although the pollutants are adsorbed by the activated carbon, the diffusion of the pollutants into the soil is prevented, but the pollutants themselves are not removed. There is also a problem of not.

  The present invention has been made in view of the above-described conventional problems, and in the modification of contaminated soil using microorganisms, a powdery porous carbon material (particularly, having a specific specific surface area and particle size). By using a porous carbon material, the adsorption power of the porous carbon material can be expressed stably and continuously, while preventing the degradation of the degradation of microorganisms that occur when used in combination with the porous carbon material. The purpose is to provide a method for modifying contaminated soil to purify pollutants.

  In order to achieve the above object, a method for modifying a contaminated soil according to the present invention includes a microorganism present in the contaminated soil and / or a microorganism newly mixed in the contaminated soil, a powdery porous carbon material, It is characterized by using a nutrient.

The method for modifying contaminated soil according to the present invention is characterized in that the porous carbon material has a specific surface area of 355 to 817 m ² / g and a particle size of 150 μm or less.

  The method for modifying contaminated soil according to the present invention is characterized by adding 0.1 to 5 parts by weight of a porous carbon material to the contaminated soil.

  The method for modifying contaminated soil according to the present invention is characterized in that the porous carbon material is activated carbon.

  The method for modifying contaminated soil according to the present invention is characterized in that the microorganism is a microorganism having an alkB (alkane hydroxylase) gene.

  In the method for modifying contaminated soil according to the present invention, the microorganisms are Gordonia, Rhodococcus, Pseudomonas, Burkholderia, Acinetobacter, Corynebacterium, Mycobacterium, Nocardia, Actinomyces , One or more microorganisms selected from the group consisting of the genus Bacillus.

  Next, each component of the present invention will be described.

  The porous carbon material used in the present invention needs to be powdery. Therefore, use various porous carbon materials such as plants based on palm, wood, etc., minerals based on coal, petroleum, etc., or those activated by chemicals. Can do. Among these, with respect to porous carbon materials having a neutral pH (specifically, pH 5.8 to 8.6 which is also the drainage standard of the Water Pollution Control Law), the pH of the soil to be modified varies. This is preferable because it can prevent water pollution and also meets the drainage standards of the Water Pollution Control Law.

And as the particle size of the porous carbon material used in the present invention, among them, the adsorption power of the porous carbon material is expressed while preventing the degradation of microbial decomposition performance, and the processing efficiency of pollutants is improved. Therefore, it is preferable to use one having a specific surface area of 355 to 817 m ² / g and a particle size of 1 to 150 μm. In addition, about a specific surface area, it is preferable to use the thing of 355-600m < ² > / g among the said range.
Here, as the grounds for setting the upper limit of the specific surface area to 817 m ² / g, the specific surface area and the oil content decomposition of the contaminated soils of Examples 1 to 3 using the porous carbon material having a changed specific surface area as described later. When plotting the rate on a graph (Fig. 2) and drawing an approximate curve that satisfies the data of all the examples, the specific surface area that makes it possible to achieve an oil content decomposition rate of 50% or more from such a curve. It is the basis.

  Moreover, it is although it does not specifically limit as a compounding quantity of the porous carbon material (especially activated carbon) used for this invention, It is preferable to add 0.1-5 weight part with respect to a contaminated soil, Among these, 2 weight part is added. It is particularly preferred. This is because if the amount is less than 0.1 parts by weight, the adsorption effect may not be sufficient. On the other hand, when the blending amount exceeds 5 parts by weight, the effect of improving the earth strength, which is a characteristic of the cement-based solidified material when the cement-based solidified material is used for the purpose of ground improvement, is reduced, or the soil is improved. This is because there is a possibility that metals such as reinforcing bars buried in the ground will easily rust when a building is constructed after quality.

The microorganism used in the present invention is appropriately selected depending on the type of pollutant, for example, Gordonia, Rhodococcus, Pseudomonas, Bacillus, Acinetobacter, Halomonas, Achromobacter, Alkaligenes, Okrobactrum Genus, Kurthia, Staphylococcus, Serratia, Thiobacillus, Bacterium, Flavobacterium, Brevibacterium, Protaminobacter, Micrococcus, Mycobacterium, Mycoplana, Methanomonas And bacteria such as the genus Rodderomyces and Rhodopseudomonas, yeasts such as the genus Pachislen, genus Rhodosporidium and Saccharomyces, and filamentous fungi such as the genus Aspergillus, Mucor and Penicillium.
In addition, the microorganisms used in the present invention listed above can be used not only in a form that is newly mixed in contaminated soil but also those bacteria that are already present in the soil.

Among these, when the pollutant is oil, it is preferable to use a microorganism having a petroleum degrading enzyme gene called alkB (alkane hydroxylase) gene. Examples of such microorganisms include Gordonia, Rhodococcus, Pseudomonas, Burkholderia, Acinetobacter, Corynebacterium, Mycobacterium, Nocardia, Actinomyces, and Bacillus. .
Furthermore, among the microorganisms listed above, the genus Gordonia and Rhodococcus have a higher cell surface hydrophobicity (higher numerical value of turbidity reduction rate) than other microorganisms as shown in Table 1, and are porous carbon materials. This is preferable because it also brings about an effect of microbial decomposition upon contact with the oil adsorbed on the surface.

  Moreover, although the microbial nutrient is used in principle for the modification method of the present invention, the nutrient may not be used as required depending on the soil to be modified. Examples of such microorganism nutrients include LB medium, yeast extract (yeast extract), minerals, and other organic or inorganic fertilizers containing nitrogen, phosphorus, potassium, and the like. .

The supply amount of the porous carbon material used in the reforming method of the present invention to the contaminated soil is appropriately determined according to the contamination status of the contaminated soil to be reformed. In order to continuously modify the pollutant, it is preferable to supply 0.1 to 5 parts by weight of the porous carbon material to the contaminated soil.
Furthermore, regarding the method of supplying the porous carbon material to the contaminated soil, depending on the contamination status of the contaminated soil to be modified, a method of mixing with the entire contaminated soil, or after excavating the contaminated soil to a predetermined depth in advance Various methods such as a method of depositing a porous carbon material or the like having a certain thickness and then backfilling with contaminated soil or the like can be employed.

According to the method for modifying contaminated soil according to the present invention, the porous carbon material can be used without reducing the resolution of microorganisms to pollutants (especially oil) in the contaminated soil by using the powdery porous carbon material. The adsorption odor and oil film can adsorb oil odor and oil film quickly (very short time of about 1 hour).
As a result, it is possible to quickly process the pollutant while reducing the amount of additive to the contaminated soil as compared with the conventional reforming method.

  According to the method for modifying contaminated soil according to the present invention, by using a powdery porous carbon material having a specific surface area and particle size within a specific range, the treatment efficiency of the pollutant can be further improved. .

  According to the method for modifying contaminated soil according to the present invention, the processing efficiency of pollutants can be further improved by mixing the porous carbon material in a specific blending amount.

  According to the method for modifying contaminated soil according to the present invention, the treatment efficiency of oily odor and oil film can be further improved by using activated carbon as the porous carbon material.

  According to the method for modifying contaminated soil according to the present invention, the treatment efficiency of pollutants can be further improved by using a specific fungus species for microorganisms.

It is a graph which shows the measurement result of the residual oil content density | concentration at the time of performing the modification | reformation method of the contaminated soil which concerns on this invention. It is a graph which shows the relationship between a specific surface area and an oil decomposition rate about the contaminated soil of Example 2 and Example 3. FIG.

  The method for modifying contaminated soil of the present invention will be described based on examples and comparative examples. In addition, the Example described below is only an example which actualized this invention, and does not limit the technical scope of this invention.

Example 1
Powdered charcoal with a specific surface area of 355 m ² / g and a particle size of 150 μm or less is used for the porous carbon material, Rhodococcus sp. NDKK6 strain is used as the microorganism, and inorganic nutrient salts (nitrogen component: urea, phosphorus component: phosphorus as nutrients) Example 1 by mixing 2 g of porous carbon material and 10 ⁶ microorganisms / g-soil with 100 g of simulated soil in which A heavy oil was mixed at a concentration of 2000 mg / kg. Of contaminated soil.

(Example 2)
A contaminated soil of Example 2 was prepared in the same manner as Example 1 except that powdered activated carbon having a specific surface area of 600 m ² / g and a particle size of 150 μm or less was used as the porous carbon material.

(Example 3)
A contaminated soil of Example 3 was prepared in the same manner as Example 1 except that powdered activated carbon having a specific surface area of 950 m ² / g and a particle size of 150 μm or less was used as the porous carbon material.

(Comparative example)
A contaminated soil of a comparative example was prepared in the same manner as in Example 1 except that no porous carbon material was used.

(Reference example)
Using granular activated carbon with an average particle size of 1.3 mm for porous carbon material, Rhodococcus sp. NDKK6 strain for microorganisms, and inorganic nutrient salts (nitrogen component: urea, phosphorus component: diammonium hydrogen phosphate) for nutrients, The contaminated soil of the reference example was prepared by mixing 2 g of a porous carbon material and 10 ⁶ microorganisms / g-soil with 100 g of simulated soil in which A heavy oil was mixed at a concentration of 2000 mg / kg.

  Next, the effects of eliminating the oily odor and oil film and the residual ratio of the oil were evaluated for the contaminated soils of the above-described Examples, Comparative Examples, and Reference Examples.

(Evaluation of oil odor elimination effect)
About the effect of eliminating the oily odor, the oily odor on the 2nd day, 7th day, 14th day, 21st day, and 28th day was evaluated by sensory evaluation 1 hour after mixing. Specifically, the odor is evaluated in 6 stages from 0 to 5 in accordance with the Oil Pollution Countermeasure Guidelines (issued by the Ministry of the Environment in 2006). Certified. The results are shown in Table 2.

(Evaluation of oil film elimination effect)
About the cancellation | release effect of an oil film, after 1 hour after mixing, the oil film of the 2nd day and the 28th day was evaluated by sensory evaluation. Specifically, after performing the petri dish method described in the Guidelines for Countermeasures against Oil Contamination, visually evaluate the oil film in four stages from 0 to 3, and if only 1 or less oil film can be confirmed, eliminate the oil film Certified as effective. The results are shown in Table 2.

(Measurement of residual ratio of oil)
About the residual rate of oil, the oil content is extracted by extracting the oil in the contaminated soil sampled from the contaminated soil on the 1st, 14th, and 28th day after mixing with a solvent (H-997, manufactured by Asahi Glass Co., Ltd.). It was measured and evaluated by the residual ratio when the oil content on the first day after mixing was taken as 100. The results are shown in Table 2 and FIG.

First, regarding the effect of eliminating the oily odor, the contaminated soil of the examples using the porous carbon material developed the adsorbing ability by the porous carbon material immediately after mixing, and the oily odor was eliminated from the results of Table 2. It became evaluation of.
On the other hand, in the contaminated soil of the comparative example not using the porous carbon material, the effect of eliminating the oily odor was not observed even on the 21st day.

Next, regarding the effect of eliminating the oil film, from the results of Table 2, the contaminated soil of the example using the powdery porous carbon material developed the adsorbing ability by the porous carbon material immediately after mixing, and the oil film was eliminated. It became evaluation that there was.
In addition, about the contaminated soil of the reference example using granular activated carbon, it became evaluation that the oil film was not eliminated also in the 2nd day after mixing. Moreover, it was the same result as the reference example also about the contaminated soil of the comparative example which does not use a porous carbon material.

  Next, regarding the residual rate of oil, the contaminated soils of Examples 1 and 2 and the reference example showed a decomposition rate of oil equivalent to that of the comparative example from the results shown in Table 2. In addition, about the contaminated soil of Example 3, although the decomposition | disassembly efficiency was inferior compared with the contaminated soil of Example 1, 2, it resulted in decomposing | disassembling 30% of oil content in the 28th day.

Here, the contaminated soil of the comparative example is a contaminated soil in which only microorganisms not containing the porous carbon material and nutrient salts are mixed, and therefore, the contaminated soil in which the resolution inherent to the microorganisms is expressed.
Therefore, it was found that the contaminated soils of Examples 1 and 2 showing the oil decomposition rate equivalent to that of the comparative example exhibited the inherent resolution of microorganisms.

Moreover, about the contaminated soil of Examples 1-3 which used the porous carbon material which changed the specific surface area, the graph of the relationship between a specific surface area and an oil decomposition rate was performed. The results are shown in FIG.
Then, as shown in FIG. 2, when the specific surface area value at which the oil content decomposition rate is 50% is calculated based on the two plotted data, the specific surface area that can realize the oil content decomposition rate of 50% or more is obtained. The upper limit was found to be 817 m ² / g.

As described above, from the results of Examples and Comparative Examples, the method for modifying contaminated soil of the present invention uses a powdery porous carbon material (particularly, a porous carbon material having a specific surface area and particle size) together with microorganisms. By doing so, it was found that the pollutant can be stably and continuously purified without reducing the resolution of microorganisms while quickly preventing the odor and oil film from spreading.

In order to achieve the above object, a method for modifying a contaminated soil according to the present invention includes a microorganism present in the contaminated soil and / or a microorganism newly mixed in the contaminated soil, a powdery porous carbon material, a nutrient mixed into the soil, the porous carbon material, a specific surface area of 355~817m ² / g, and characterized by the following particle size der Rukoto 150μm

In order to achieve the above object, a method for modifying a contaminated soil according to the present invention includes a microorganism present in the contaminated soil and / or a microorganism newly mixed in the contaminated soil, a powdery porous carbon material, A nutrient is mixed with soil simultaneously or separately, and the porous carbon material has a specific surface area of 355 to 817 m ² / g and a particle size of 150 μm or less.

In order to achieve the above object, a method for modifying a contaminated soil according to the present invention includes a microorganism present in the contaminated soil and / or a microorganism newly mixed in the contaminated soil, a powdery porous carbon material, a nutrient mixed simultaneously or separately into the soil, the porous carbon material, a specific surface area of 355~817m 2 / ^g, and 150μm Ri particle size of less than der, as it does not further advance carrying microorganisms Oh, wherein the Rukoto.

Claims (6)

A method for modifying contaminated soil,
Microorganisms present in the contaminated soil and / or microorganisms newly mixed in the contaminated soil;
Powdered porous carbon material,
A method for modifying contaminated soil, characterized by using a nutrient.
The porous carbon material is
The method for modifying contaminated soil according to claim 1, wherein the method has a specific surface area of 355 to 817 m ² / g and a particle size of 150 μm or less.
The porous carbon material,
The method for modifying contaminated soil according to claim 1 or 2, wherein 0.1 to 5 parts by weight is added to the contaminated soil.
The porous carbon material is
The method for reforming contaminated soil according to any one of claims 1 to 3, wherein the method is activated carbon.
The microorganism is
The method for modifying contaminated soil according to any one of claims 1 to 4, wherein the microorganism has an alkB (alkane hydroxylase) gene.
The microorganism is
One or more selected from the group consisting of Gordonia, Rhodococcus, Pseudomonas, Burkholderia, Acinetobacter, Corynebacterium, Mycobacterium, Nocardia, Actinomyces, and Bacillus The method for modifying contaminated soil according to any one of claims 1 to 5, wherein the microorganism is a microorganism.