JP6590600B2 - Contaminated soil purification method - Google Patents

Description

  The present invention relates to a contaminated soil purification method for purifying soil in an underground region contaminated with harmful substances.

Cyanide is an inorganic substance composed of carbon and nitrogen, and is classified as a heavy metal and classified as a second-type specific hazardous substance in the Soil Contamination Countermeasures Law (hereinafter referred to as the soil-to-ground law). The cyan compound includes a group of compounds called cyanide and metal cyano complex. Cyanide is also called “free cyan” and is represented by the general formula An (CN) x, where A is hydrogen (H), sodium (Na), potassium (K), ammonium (NH ₄ ). , Calcium (Ca), etc., and is the most toxic form of cyanide compounds. The metal cyano complex is a compound in which a metal salt of hydrogen cyanide and a metal are combined with an excess of cyanide ion (CN ⁻ ), and is represented by the general formula An [M (CN) x]. Here, M corresponds to metals such as silver (Ag), gold (Au), cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), nickel (Ni), and zinc (Zn). However, it is dissolved or suspended in the solution.

  Cyanide compounds may be contained in industrial wastewater and the like, and are substances having properties that should be removed by purification treatment. Factories that discharge cyanide include plating factories, beneficiation refineries, steel heat treatment factories, and coke factories. In these factories, cyanide wastewater treatment facilities are installed in the factories because cyanide compounds are by-produced in the process of building baths such as copper, zinc, nickel, and gold, and in the product manufacturing process. According to “Survey results on the status of implementation of the 2008 Soil Contamination Countermeasures Law and Soil Contamination Surveys / Countermeasures Cases: February 2010: Ministry of the Environment” (hereinafter referred to as “Soil vs. Case Example Results”) The industry categories that exceeded the soil environmental standards by are in the order of metal products manufacturing industry, gas industry, and chemical industry. In Japan, there are many small and medium plating plants, and there are more than 2,000 companies nationwide. Most of them were built around urban areas during the post-war high economic growth period, and potentially leaked from plating baths and pipes due to leakage of cyanide compounds and aging of facilities during operation. The soil is expected to be contaminated with cyanide.

  Many studies have been conducted in the wastewater treatment field regarding the presence of cyanide compounds in solution (wastewater), and it has been reported that the form is mostly free cyanide and metal cyano complexes. Treatment methods for wastewater containing these cyanides include alkali chlorine method, ozone oxidation method, electrolytic oxidation method, bitumen method (precisely soluble complex compound precipitation method), acid decomposition combustion method, boiled method (boiled high temperature combustion method) In addition, a wet heat decomposition method and an adsorption method are known. However, these treatment methods do not apply to highly stable metal cyano complexes, such as iron, cobalt, silver, and gold cyano complexes, or require severe equipment under severe reaction conditions, There was a problem that further processing of the product was necessary. In view of this, a technique for restoring the environment using biological functions, so-called bioremediation, has attracted attention, and microorganisms having a cyanide compound resolution are being searched.

  At present, regarding microbial degradation of free cyanide such as potassium cyanide and sodium cyanide, Pseudomonas putida, Pseudomonas sp. Acinetobacter sp. Fusarium sp. Klebsiella sp. There are reports that microorganisms such as these have been isolated and identified.

Regarding metal cyano complexes, Fusarium solani and Trichoderum polysporum have been reported as decomposing microorganisms of nickel-cyano complexes ([K ₂ Ni (CN) ₄ ]). In addition, Fusarium oxysporum, Cytalidium thermophilum, and Penicillium miczynski have been reported as degrading bacteria of potassium ferrocyanide ([K ₄ Fe (CN) ₆ ]), which is an iron cyano complex (all of which are Non-patent Document 1). Also, the applicant of the present application has isolated and identified various microorganisms that degrade iron cyano complexes (for example, Patent Documents 1 and 2 and the like, Patent Document 3 and the like as identification examples other than the present applicant).

  However, when decomposing an iron cyano complex, all of the above microorganisms work under aerobic conditions, so the application form of the microorganism is limited, and the iron cyano complex is decomposed in soil with almost no oxygen supply. It has not been put into practical use because it has various technical problems in actual use. The microorganism described in Patent Document 3 has the possibility of decomposing an iron cyano complex under anaerobic conditions. However, the degrading bacterium Klebsiella pennumoniae is a pathogenic bacterium of BSL2 and is an in-situ treatment method Auger. It is not suitable for the treatment of anaerobic cyano complex compounds by the formation method and still has various technical problems, so it has not been put into practical use.

In view of the above circumstances, it is desirable that the purification of cyanide compounds represented by iron cyano complexes is applied to soil, particularly contaminated soil reaching the aquifer.
As the actual condition of the treatment of contaminated soil, excavation and removal for the purpose of complete purification are often selected in consideration of the psychological factors of the landowner and the economic aspects of real estate transactions. In particular, heavy metals such as lead and cadmium cannot be further decomposed, and despite the high cost of 50,000 yen / m ³ or more due to excavation and removal, the second class specified harmful Excavation removal is adopted in 83% of the cases of excess substances (according to “Soil vs. Case Results”). The reason why the excavation and removal ratio is very high at 83% is also because the in-situ purification technology has not been established. In particular, for cyanide compounds, the range where in-situ purification technology can be applied is limited. Insolubilization requires long-term monitoring, and land development is limited during development. The chemical addition process (Fenton method) and ozone injection process are limited to some cyanide compounds because they cannot be applied to stable ferrocyan (iron-cyan complex). In the case of excavation and removal, it is necessary to detoxify the excavated soil separately, heat treatment represented by cement raw materials, insolubilization treatment that is chemical treatment, chemical addition treatment, ozonolysis treatment, classification cleaning treatment that is physical treatment There is. As described above, cyanide is not easily decomposed and heat treatment is often employed. In addition, regarding the heat treatment, acceptance standards in the case of cement raw materials are strict, and there is no choice but to entrust the treatment to a dedicated heat treatment facility. Therefore, the treatment cost of the cyanide compound is higher than the normal heavy metal treatment cost, and application of the in-situ purification method is required as a lower cost treatment method.

JP 2000-270847 A JP 2003-275791 A JP 2006-281053 A

Knowles C.I. J. et al. et. al, Enzyme and Microbiology 22: 223-231, (1998).

  In the current bioremediation of cyan contaminated soil, biostimulation that promotes microbial activity by injecting nutrients, dissolved oxygen water and air into the soil is performed. However, there are conditions for the application of this method, and the contaminated site is contaminated soil of free cyanide or copper cyano complex, which is relatively easy to decompose cyanide, and suitable geological conditions (good water permeability, An empirical study has been conducted to confirm purification when the conditions such as aquifers that can be easily moved are satisfied.

  On the other hand, bioaugmentation, in which cyanogen-degrading microorganisms with high cyanide resolution are injected into contaminated soil to decompose cyanide and purify the contaminated soil, is also being studied. Since it is difficult to disperse microorganisms to the soil in the underground region containing selenium, it has not been established until it can be said that it is an effective method for purifying contaminated soil. In addition, the microorganisms introduced into the underground area have a large change in the growth environment, so the desired ability to decompose cyanide may not be fully demonstrated, and the activity in the underground area is greatly reduced, resulting in contaminated soil. It has also been reported that there are cases where it is not possible to purify.

  Therefore, in view of the above circumstances, an object of the present invention is to provide a contaminated soil purification method that can efficiently decompose and purify contaminated soil containing a cyanide compound regardless of the formation conditions.

[Configuration 1]
In order to achieve the above object, the contaminated soil purification method of the present invention comprises:
A contaminated soil purification method for purifying soil in an underground area contaminated with harmful substances,
Stirring and kneading the underground region, a transition step of transferring cyanide contained in the soil of the underground region to groundwater,
A pumping process for pumping the groundwater from the underground area after the transition process;
By adding a cyanide degradable microorganisms to the ground water that is pumped by the pumping process, it has rows and cyan decomposition step of culturing in the tank,
The cyan-degrading microorganism contains at least one microorganism selected from the microorganisms deposited under the deposit numbers: NITE P-01828, NITE P-01829, and NITE P-01856 .

[Operation effect 1]
In other words, the migration process is performed to stir and knead the underground area contaminated with harmful substances and transfer the insoluble cyanide to the groundwater, so even if the soil is contaminated with insoluble cyanide, The cyanide compound contained in is dissolved by kneading with the groundwater by kneading, and the cyanide can be temporarily transferred to the groundwater.
The cyanide transferred to the groundwater can be recovered as groundwater that can be handled on the ground by a pumping process.
Therefore, if the cyanide decomposing step of culturing cyanogen-degrading microorganisms in the tank with the groundwater obtained in the pumping step is performed, the cyanide compound contained in the groundwater is assimilated and detoxified by the cyanide-decomposing microorganisms.
Here, examples of the cyan compound include free cyan, inorganic cyan, organic cyan, and metal cyano complexes. Examples of the metal cyano complex include a copper cyano complex having a relatively high water solubility and a poorly soluble iron cyano complex.

As a result, the hardly decomposable cyanide compound in the underground area is decomposed and purified by tank culture. Therefore, the cyanide can be efficiently decomposed and purified in situ regardless of the formation conditions.
Further, the microorganisms deposited under the accession numbers: NITE P-01828, NITE P-01829, and NITE P-01856 have the ability to degrade the hardly decomposable iron cyano complex. Therefore, when an cyanide compound contained in groundwater obtained in the pumping process is decomposed in an environment containing at least one kind of microorganism selected from these microorganisms, even if an indegradable iron cyano complex is contained in the underground region, It becomes possible to purify. That is, the purification ability can be exerted even on soil that has been conventionally considered difficult to purify, and can be widely used.

[Configuration 2]
The transition process may include a stirring / kneading step for stirring / kneading the underground region and a solubilizing agent adding step for supplying a solubilizing agent for dissolving the insoluble cyanide compound to the underground region.

[Operation effect 2]
When the agitation / kneading step and the solubilizing agent addition step are performed as the transfer process, even if the cyanide compound is poorly soluble in groundwater, the cyanide compound can be efficiently transferred to the groundwater by the solubilizer. Therefore, the cyanide compound transferred to the groundwater is efficiently rendered harmless by the pumping process and the cyan decomposition process.

  The stirring / kneading step and the solubilizing agent addition step may be performed in any order. It is preferable that the solubilizer is in efficient contact with the soil in the underground area. This is because a state in which the solubilizer is suitably brought into contact with the cyanide in the soil is obtained, and can be appropriately adjusted according to the form of the underground region.

  Therefore, even if there are few microorganisms capable of decomposing cyanide in the underground area, the cyanide-degrading microorganisms cultured in tanks decompose and purify the cyanide in the underground area. I was able to do that.

Process chart of contaminated soil purification method Graph showing changes in total microbial count in groundwater Graph showing changes in the number of cyanide-degrading microorganisms in groundwater Graph showing changes in cyanide concentration in groundwater

  Below, the contaminated soil purification method concerning embodiment of this invention is demonstrated. Preferred examples are described below, but these examples are described in order to more specifically illustrate the present invention, and various modifications can be made without departing from the spirit of the present invention. The present invention is not limited to the following description.

Contaminated soil purification method according to an embodiment of the present invention,
A contaminated soil purification method for purifying soil in an underground area contaminated with harmful substances,
A stirring / kneading step for stirring / kneading the underground region and a solubilizing agent adding step for supplying a solubilizing agent for dissolving the cyanide compound to the underground region, and transferring the cyanide compound contained in the underground region to the groundwater Transition process;
A pumping process for pumping groundwater from the underground area after the transition process;
A cyanide decomposing step of adding a cyanolytic microorganism to the groundwater pumped in the pumping step and culturing the tank in a tank.

  The agitation / kneading step is performed by a ground kneader. The ground kneader is for excavating the ground while rotating the agitating blade that agitates and kneads the soil in the underground area around the axis, and in the vicinity of the agitating blade, an additive such as a solubilizer is agitated and kneaded. A nozzle for discharging into the soil is provided. As a result, when the underground area contaminated with harmful substances is stirred and kneaded in the ground kneader, the solubilizing agent that dissolves the insoluble cyanide compound is discharged from the nozzle, so that the stirring / kneading step and solubilizing agent addition It is comprised so that the transfer process which performs a step simultaneously can be implemented.

  NS Bioacty CN3 manufactured by Nippon Steel & Sumikin Engineering Co., Ltd. is preferably used as the solubilizer used here. As the solubilizer, those that dissolve insoluble cyanide are preferable, but any solubilizer that can dissolve cyanide that is insoluble in water in soil can be used. It is clear that it contributes to the purification of compounds.

  When the transfer process is performed, insoluble cyanide contained in the soil in the underground area contaminated with harmful substances is solubilized by the solubilizer and transferred to water in the soil, so it flows down to the groundwater aquifer. Thus, it becomes possible to pump up with the groundwater.

Since the soil that has undergone the transfer process becomes clean with the insoluble cyanide transferred to groundwater, it can be purified by removing the groundwater. In fact, groundwater can be pumped from a well that has been cut to the aquifer.
The groundwater pumped from the pumping well is introduced into a tank to which cyanide-degrading microorganisms are added, and is used for culturing cyanide-degrading microorganisms in the tank. As a result, the cyanide transferred to the ground water is assimilated and detoxified by the cyan degradable microorganisms. As a result, the cyanide contained in the soil in the underground region is removed and decomposed and purified.

Here, various known microorganisms are used as cyan-degrading microorganisms, for example, the genus Proteobacteria,
Betaproteobacteria genus,
Burkholderiales,
Burkholderiacea,
Burkholderia sp. ,
Actinobacteria genus,
Actinomycetales,
The genus Norcardioidaceae,
Genus Norcardioides,
Rhodococcus sp. ,
Alphaproteobacteria genus,
Caulobacterium genus,
Caurobacteraceae genus,
Brevundimonas sp. ,
Bacteroidetes genus,
Sphingobacteria genus,
Sphingobacterias genus,
Chitinophagaceae genus,
Chitinophaga sp.
At least one microorganism selected from the microorganisms deposited as NITE P-01828, NITE P-01829, and NITE P-01856 is suitable for degrading persistent cyanide compounds. It has been clarified by the present inventors that it has the ability to purify, and contributes to efficiently decomposing and purifying cyanide compounds in the pumped ground water.

  The wastewater used for culturing cyanide-degrading microorganisms in the tank is almost free of cyanide compounds, and is therefore discarded in rivers after confirming that it meets environmental standards. If it is difficult to meet environmental standards, it can be reprocessed separately, or by returning to the underground area, components other than cyanide can be decomposed and purified mainly by microorganisms that grow in the underground area. It becomes possible. Cyanolytic microorganisms that can be cultured in the tank can be easily selected, confirming the possibility of growth in the soil in the underground area, and omitting the process of acclimatizing to the growth conditions in the soil in the underground area It is possible to cultivate cyanogen-degrading microorganisms reliably and easily.

[Microorganism culture test]
While the cyan contaminated soil was kneaded with a ground kneader, a pumping well was provided in the underground area where the solubilizer was injected, and the groundwater pumped from the pumping well was collected. While adding nutrients to the collected groundwater, 6 types of exogenous cyanolytic microorganisms isolated from soil other than cyan-contaminated soil were cultured. The foreign cyanide-degrading microorganisms belong to the microorganisms deposited under the accession numbers: NITE P-01828, NITE P-01829 and NITE P-01856, and belong to a common genus with these microorganisms and have similar properties. The other three types of microorganisms that were confirmed were separately grown and used. 6 kinds of grown cyanolytic microorganisms were added to the ground water collected in a 200L tank and cultured, and the change in the total number of microorganisms in the tank, the change in the number of cyanolytic microorganisms, and the change in cyanide concentration were observed. When investigated, it became as shown in FIGS. The results in FIGS. 2 to 4 are obtained by adding an equal amount of all six types of microorganisms to obtain the initial number of bacteria. However, even if any of these microorganisms is added alone to the tank, it grows similarly. That has been confirmed.

  The change in the number of microorganisms in the tank is as follows. After adding 6 kinds of cyanide-degrading microorganisms obtained in the groundwater in the tank, normal cultivation is carried out with nutrient 1 for 7 days, and again 6 kinds of cyanide-degrading microorganisms are added. Culturing was carried out in nutrient solution 6 for 6 days, and the culture solution in the tank was collected to determine the number of grown bacteria (cfu / mL). In FIG. 2, the number of bacteria obtained on the standard agar medium was taken as the total number of microorganisms, and in FIG. 3, the number of bacteria obtained on the 227 agar medium was taken as the number of cyanolytic microorganisms. Further, in FIG. 4, the cyan density measured in accordance with the measuring method according to JIS K 0102 is taken as the cyan compound density.

NS Bioacty CN3 manufactured by Nippon Steel & Sumikin Engineering Co., Ltd. was used as a solubilizer, and NS Bioacty CN1 and CN2 manufactured by Nippon Steel & Sumikin Engineering Co., Ltd. were used as nutrients 1 and 2. In addition, three of the obtained six cyanolytic microorganisms were novel microorganisms deposited under the accession numbers: NITE P-01828, NITE P-01829, and NITE P-01856.
The standard agar medium is a medium composed of yeast extract 0.25%, peptone 0.5%, glucose 0.1%, and agar 1.5%, and most microorganisms grow well. On the other hand, 227 agar medium is a medium consisting of yeast extract 0.4%, malt extract 1.0%, glucose 0.4%, and agar 2.0%, and six kinds of foreign cyanolytic microorganisms grow specifically.

From FIG. 2, it can be seen that when cyanide-degrading microorganisms are cultured using groundwater pumped from the pumping well, both nutrients 1 (dashed line) and 2 (solid line) contribute to the growth of all microorganisms.
In addition, when examining the grown microorganisms from FIG. 3, according to the nutrient 1, although cyan-degradable microorganisms initially grow, the number of growth seems to be limited over time (broken line). It can be seen that a larger amount of growth (about 10 times) is obtained by using (solid line).
It was also found that the cyanide concentration in the tank during the cultivation period of the cyanolytic microorganisms decreased at a substantially constant rate for 13 days, and the cyanide concentration of about 30% decreased in 13 days.

  That is, it has been clarified that the cyanide compound in the soil can be efficiently decomposed and purified by the contaminated soil purification method of the present invention.

[Another embodiment]
In the embodiment described above, the stirring / kneading step and the solubilizing agent adding step are performed simultaneously in the transition process. However, the solubilizing agent adding step is solubilized from the ground surface to the underground region separately from the stirring / kneading step. It is good also as a structure which infiltrate and inject | pours an agent, and can also be the structure which inject | pours into an underground area | region by providing another injection well. Further, if the cyanide compound is transferred to the groundwater without using a solubilizer, the transfer process can be performed only by the stirring / kneading step.

  Since the contaminated soil purification method of the present invention can easily and reliably purify the contaminated soil, the soil contaminated with cyanide is purified as bioaugmentation that purifies the contaminated soil in situ. Used for.

Claims (2)

A contaminated soil purification method for purifying soil in an underground area contaminated with harmful substances,
Stirring and kneading the underground region, a transition step of transferring cyanide contained in the soil of the underground region to groundwater,
A pumping process for pumping the groundwater from the underground area after the transition process;
By adding a cyanide degradable microorganisms to the ground water that is pumped by the pumping process, it has rows and cyan decomposition step of culturing in the tank,
The contaminated soil purification method, wherein the cyan degradable microorganism contains at least one microorganism selected from the microorganisms deposited under the accession numbers: NITE P-01828, NITE P-01829, and NITE P-01856 .   2. The contaminated soil according to claim 1, wherein the transition step includes a stirring / kneading step of stirring / kneading the underground region and a solubilizing agent adding step of supplying a solubilizing agent that dissolves insoluble cyanide to the underground region. Purification method.

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