JPH11128903A - Decomposition removal of oil-polluted soil by microorganism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decompose/remove oil components in oil-polluted soil, including especially polycyclic aromatic hydrocarbons. SOLUTION: In a decomposition removal method of oil-polluted soil by microorganisms, the polluted soil is controlled for a prescribed period to strength the decomposition activity of microorganisms existing in the polluted soil (step 101). A mushroom rearing bed containing a lignin decomposition enzyme produced in the propagation process of white rot fungi is prepared separately (step 102). If the enzyme has been produced sufficiently in the bed, the bed in added into the polluted soil when indigenous fungi in the soil are weakened enough (step 3). Next, the ratio (C/N ratio) between the carbon content (T-C) and nitrogen content (T-N) of the polluted soil is controlled to >=100 (step 103).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for decomposing and removing oil-contaminated soil by microorganisms.

[0002]

2. Description of the Related Art Recently, a technique called bioremediation, in which contaminants are decomposed and rendered harmless by microorganisms, has attracted attention.

[0003] Bioremediation is a method of decomposing and detoxifying contaminants by utilizing the decomposing ability of microorganisms such as bacteria and fungi. -By improving the activity of microorganisms by adjusting the environment such as nutrition and ventilation, it is possible to decompose pollutants more efficiently than in the natural state.

[0004] Since such bioremediation does not use any chemical agent unlike physical treatment or chemical treatment, it is expected to be low in cost and high in safety, and its application range will be further expanded in the future.

[0005]

Here, for example, in a case where soil contaminated with crude oil is to be purified by bioremediation, various hydrocarbon compounds having about 5 to 40 carbon atoms, which are the main components of crude oil, have a molecular Depending on the type of structure, so-called aliphatic hydrocarbons such as paraffinic and olefinic types are roughly classified into aromatic hydrocarbons, and easily decomposable hydrocarbons such as aliphatic hydrocarbons and aromatic hydrocarbons with relatively simple structures. Hydrogen can be relatively easily decomposed by bacteria contained in the soil.

On the other hand, hard-to-degrade hydrocarbons such as polycyclic aromatic hydrocarbons having a complicated structure cannot be decomposed by such soil bacteria, and such polycyclic aromatic hydrocarbons can be easily degraded. Degradable special selection (screening)
Even with the bacteria that have been used, usually compete with soil bacteria,
There has been a problem that the decay occurs without being able to exert its original decomposition action.

The present invention has been made in view of the above circumstances, and has as its object to provide a method for decomposing and removing oil-contaminated soil by microorganisms capable of decomposing and removing polycyclic aromatic hydrocarbons.

[0008]

In order to achieve the above object, a method for decomposing and removing oil-contaminated soil by microorganisms according to the present invention, as described in claim 1, is a method for decomposing microorganisms existing in oil-contaminated soil. The oil-contaminated soil is managed for a predetermined period of time so that the easily degradable hydrocarbons in the oil-contaminated soil are decomposed and consumed, and the microorganisms decline. Is added to the oil-contaminated soil.

[0009] The method for decomposing and removing oil-polluted soil by microorganisms according to the present invention comprises the step of adding the mushroom-growing bacterial bed to the oil-polluted soil, and then adding the carbon content (TC) of the oil-polluted soil to nitrogen. The ratio (C / N ratio) to the amount (TN) is adjusted so that a new lignin-degrading enzyme is produced from the white rot fungus.

Further, in the method for decomposing and removing oil-contaminated soil by microorganisms according to the present invention, the mushroom-growing bacterial bed is a waste bacterial bed after removing the grown mushroom.

In the method for decomposing and removing oil-polluted soil by microorganisms according to the first aspect of the present invention, first, the activity of decomposing microorganisms existing in the oil-polluted soil to oil-polluted soil containing oil is enhanced. Manage nutrition, aeration, moisture, temperature, etc. for a predetermined period.

The oil component mainly contains so-called aliphatic hydrocarbons such as paraffins and olefins, and aromatic hydrocarbons. However, when the activity of decomposing microorganisms is enhanced as described above, these oils may be used. Of these, easily decomposable hydrocarbons, that is, most of aliphatic hydrocarbons and aromatic hydrocarbons having relatively simple structures are decomposed and removed by the action of microorganisms in the oil-contaminated soil. This is called primary decomposition.

Next, when the primary decomposition proceeds and the easily decomposable hydrocarbons are consumed, the energy source which is the source of the activity from the viewpoint of the microorganisms becomes deficient. to decline.

In view of such a stage, a mushroom-growing bacterial bed containing lignin-degrading enzyme generated in the process of growing white rot fungi is added to the oil-contaminated soil.

In this manner, the lignin-degrading enzyme contained in the fungus bed for mushroom growth exhibits its degrading activity without competing with the microorganisms that have already declined, and remains in the oil-contaminated soil. Quickly decomposes hard-to-degrade hydrocarbons.

As the microorganism, mainly bacteria, in particular, indigenous bacteria such as Pseudomonas and Rhodococcus which naturally exist in the soil can be used. Bacteria other than such indigenous bacteria, actinomycetes, filamentous fungi, yeasts and the like can be used. Such microorganisms other than bacteria may be used.

The polycyclic aromatic hydrocarbon includes substances having a plurality of benzene rings, particularly three or more rings, such as phenanthrene and pyrene.

Here, after the mushroom-growing bacterial bed is added to the oil-contaminated soil, the ratio (C / N ratio) between the carbon content (TC) and the nitrogen content (TN) of the oil-contaminated soil is determined. ) Is adjusted so that a new lignin-degrading enzyme is produced from the white-rot fungi, a new lignin-degrading enzyme is added to the newly added lignin-degrading enzyme in the oil-contaminated soil from the white-rot fungi. Can be generated.

The types of mushrooms include shiitake mushroom, maitake mushroom, nameko mushroom, oyster mushroom, enokitake mushroom, bunashimeji mushroom, mushroom mushroom, and kuromiku mushroom.

As a mushroom growth fungal bed, the culture substrate, culture conditions and growth stage of the mushroom are arbitrary as long as the lignin-degrading enzyme is produced from the white-rot fungi. The lignin-degrading enzyme can also be used in a state in which it is sufficiently expressed, or may be at the stage where the mushrooms have grown to some extent. In this case, it is possible to reuse a waste bacteria bed, which is a waste medium that has been conventionally disposed of, for the purpose of decomposing and removing oil-contaminated soil.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for decomposing and removing oil-polluted soil by microorganisms according to the present invention will be described below with reference to the accompanying drawings. It is to be noted that the same reference numerals are given to components and the like that are substantially the same as those in the conventional technology, and description thereof will be omitted.

(First Embodiment) FIG. 1 is a flowchart showing a procedure of a method for decomposing and removing oil-contaminated soil by microorganisms according to a first embodiment. As can be seen from the figure, in the decomposition and removal method of the present embodiment, first, nutrients are applied to an oil-contaminated soil containing oil for a predetermined period so that the decomposition activity of microorganisms present in the oil-contaminated soil is increased. Then, management of ventilation, moisture, temperature and the like is performed (step 101).

As the microorganisms, it is preferable to use indigenous bacteria naturally contained in oil-contaminated soil.

Here, the ratio (C / N ratio) between the amount of carbon (TC) and the amount of nitrogen (TN) of the oil-contaminated soil is about 10 to 50,
Sawdust, nitrogen fertilizer, and the like are added as appropriate so as to maintain especially around 20. By setting the C / N ratio in this way, it is possible to maintain a good activity of decomposing microorganisms in the oil-contaminated soil, in this embodiment, indigenous bacteria.

When the C / N ratio is set in this way to increase the activity of decomposing indigenous bacteria, easily decomposable hydrocarbons in the oil contained in the oil-contaminated soil, that is, paraffinic and olefinic ones are used. Aliphatic hydrocarbons and aromatic hydrocarbons having relatively simple structures are efficiently decomposed and removed by indigenous bacteria.

FIG. 2 is a graph showing a state in which hydrocarbons in the oil-contaminated soil are reduced by the decomposition action of indigenous bacteria.

However, as can be seen from the figure, the decreasing rate of hydrocarbons in the oil-contaminated soil gradually decreases with time, and hardly decreases in time. This is because easily degradable hydrocarbons such as aliphatic hydrocarbons that can be decomposed by indigenous bacteria and aromatic hydrocarbons with a simple structure are consumed by decomposition, and hardly degradable hydrocarbons are contained in oil-contaminated soil. This means that only certain polycyclic aromatic hydrocarbons remain.

In such a state, the energy source which is a source of the activity is deficient from the viewpoint of the indigenous bacteria, and the indigenous bacteria gradually decline.

On the other hand, a fungal bed for mushroom growth containing a lignin-degrading enzyme generated during the growth process of white rot fungi is separately prepared (step 102).

By preparing such a mushroom-growing fungal bed according to a method used for cultivation and cultivation of ordinary mushrooms, a culture having lignin-degrading enzyme activity can be obtained. When the mycelium of white-rot fungi is grown on a substrate, for example, a medium mainly containing a mixture of nutrient additives such as sawdust and bran, first, carbon sources and nitrogen sources in the nutrient additives that are easy to use are used. When the nutrients in the nutrient additives are depleted, cellulase, hemicellulase, lignin-degrading enzymes, etc. are secreted outside the cells in order to use hard-to-degrade substrates such as sawdust. Nutrients such as a carbon source and a nitrogen source are taken out of the substrate to keep growing.

It is sufficient that the lignin-decomposing enzyme is sufficiently produced from the white-rot fungus as such a mushroom-growing bacterial bed, and it is irrelevant to the degree of mushroom growth. Therefore, it can be used at various stages, such as those that have not grown as mushrooms but have grown to some extent, and those that have grown to some extent as mushrooms.However, consider recycling. For example, it is preferable to use a so-called waste bacteria bed after mushrooms have sufficiently grown and picked up for shipping.

When the lignin-degrading enzyme has been sufficiently produced in the mushroom-growing bacterial bed, the bacterial bed is added to the oil-contaminated soil at a time when the indigenous bacteria in the oil-contaminated soil have sufficiently declined ( Step 103).

Whether or not the indigenous bacteria have sufficiently declined is monitored by monitoring the oil content in the oil-contaminated soil using, for example, a graph as shown in FIG. 2 and based on the time when those contents hardly decrease. Judge it.

When a fungal bed containing a lignin-degrading enzyme is added to the oil-contaminated soil in which the indigenous bacteria have declined, the lignin-degrading enzyme exhibits its degrading activity without competing with microorganisms that have already declined. It decomposes and decomposes the polycyclic aromatic hydrocarbons remaining in the oil-contaminated soil as secondary decomposition.

Next, the carbon amount (TC) and the nitrogen amount (TN) of the oil-contaminated soil to which the mushroom-growing bacterial bed has been added are set to a ratio (C / N ratio) of, for example, 100 or more. It is adjusted so as to be (step 104). As a method of adjustment, if the amount of carbon is small, for example, sawdust may be introduced.

In this way, because of the lack of nitrogen, the white rot fungus newly produces lignin-degrading enzyme in the oil-contaminated soil, in addition to the lignin-degrading enzyme generated in the bacterial bed. Then, the polycyclic aromatic hydrocarbons, which are hardly decomposable hydrocarbons remaining in the oil-contaminated soil, are decomposed more efficiently.

As described above, according to the method for decomposing and removing oil-contaminated soil by microorganisms according to the present embodiment, first, as a first step, the activity of decomposing indigenous bacteria is increased to easily degrade hydrocarbons, that is, fats. Aromatic hydrocarbons and aromatic hydrocarbons having a simple structure are decomposed and removed. Then, in view of the decline of indigenous bacteria due to the depletion of easily degradable hydrocarbons that are the target of indigenous bacteria decomposition, as a second step, refractory carbonization is performed. Since a mushroom growth bacterial bed containing hydrogen, that is, a lignin-degrading enzyme capable of degrading polycyclic aromatic hydrocarbons, was added, such lignin-degrading enzyme can be degraded without competing with indigenous bacteria. Polycyclic aromatic hydrocarbons can be decomposed.

That is, by adopting such a two-stage decomposition and removal method, almost all hydrocarbons contained in the oil-contaminated soil can be decomposed and removed, and the hardly It is possible to avoid a situation in which only the polycyclic aromatic hydrocarbon that is hydrogen remains in the oil-contaminated soil without being decomposed.

Further, in such a two-stage decomposition and removal method, in the first stage, indigenous bacteria naturally contained in soil are removed.
In the second stage, hydrocarbons are decomposed using lignin-degrading enzymes contained in bacterial beds for growing edible mushrooms. There is almost no possibility of adverse effects, and it can be said that this is an extremely safe decomposition and removal method.

Further, according to this embodiment, after adding the mushroom-growing bacterial bed containing the lignin-degrading enzyme to the oil-contaminated soil, the C / N ratio of the oil-contaminated soil is adjusted to, for example, 100 or more. Therefore, in addition to the initially added lignin-degrading enzyme, lignin-degrading enzyme is newly produced by white rot fungi in oil-contaminated soil, and is a persistent hydrocarbon remaining in oil-contaminated soil. The cyclic aromatic hydrocarbon can be decomposed more efficiently.

Further, according to the present embodiment, the waste bacterial bed after picking up the grown mushroom is used as a mushroom growth bacterial bed. It can be reused for the purpose of decomposition and removal.

In this embodiment, after the mushroom-growing fungal bed is added to the oil-contaminated soil, the carbon amount (TC) and the nitrogen amount (TN) of the oil-contaminated soil are determined by their ratio (C / C / N). N ratio)
Although it was adjusted so as to be not less than 00 (step 104), if the hardly degradable hydrocarbon can be sufficiently decomposed only by the lignin degrading enzyme contained in the mushroom growth fungus bed, The step of adjusting the C / N ratio may be omitted.

[0043]

As described above, according to the method for decomposing and removing oil-contaminated soil by microorganisms according to the first aspect of the present invention, a lignin-degrading enzyme capable of decomposing and removing hardly decomposable hydrocarbons is used.
It is possible to exert its decomposition activity without competing with indigenous bacteria, and it is possible to avoid a situation in which only hardly decomposable hydrocarbons remain in oil contaminated soil without being decomposed as in the past. .

According to the method for decomposing and removing oil-contaminated soil by microorganisms according to the second aspect of the present invention, another lignin-degrading enzyme is newly added in addition to the lignin-degrading enzyme contained in the mushroom-growing bacterial bed. Generated from white-rot fungi in oil-contaminated soil,
There is also an effect that polycyclic aromatic hydrocarbons, which are hardly decomposable hydrocarbons remaining in the oil-contaminated soil, can be decomposed more efficiently.

Further, according to the method for decomposing and removing oil-contaminated soil by microorganisms according to the third aspect of the present invention, it is possible to reuse the waste bacteria bed which has been disposed of for the purpose of decomposing and removing oil-contaminated soil. Also has the effect of becoming.

[0046]

[Brief description of the drawings]

FIG. 1 is a flowchart showing a procedure of a method for decomposing and removing oil-contaminated soil by microorganisms according to the present embodiment.

FIG. 2 is a graph showing the operation of the method for decomposing and removing oil-contaminated soil by microorganisms according to the embodiment.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Genshiro Kawai 1-2-2 Nishikugata-cho, Kiryu-shi, Gunma Mori Industry Co., Ltd.

Claims (3)

[Claims] 1. The oil-polluted soil is controlled for a predetermined period of time so that the microorganisms present in the oil-polluted soil have a high decomposition activity, and the easily degradable hydrocarbons in the oil-polluted soil are decomposed and consumed to reduce the microorganisms. A method for decomposing and removing oil-contaminated soil by microorganisms, comprising adding, to the oil-contaminated soil, a mushroom-growing bacterial bed containing lignin-degrading enzymes generated during the growth of white-rot fungi after the decline. 2. The method according to claim 1, wherein the mushroom-growing fungal bed is added to the oil-contaminated soil, and then the ratio of carbon (TC) to nitrogen (TN) of the oil-contaminated soil (C / N ratio). The method for decomposing and removing oil-contaminated soil by microorganisms according to claim 1, wherein the method is adjusted so that a new lignin-degrading enzyme is produced from the white rot fungus. 3. The method for decomposing and removing oil-polluted soil by microorganisms according to claim 1, wherein said mushroom-growing bacterial bed is a waste bacterial bed after removing the grown mushroom.