JP6153304B2 - Purification method for oil-contaminated soil - Google Patents

Description

  The present invention relates to a method for purifying petroleum-contaminated soil and a composition for purifying petroleum-contaminated soil.

  “Soil pollution by petroleum hydrocarbons” caused by accidents when transporting oil, leaks from factories, etc. has been a problem in the past, and legislation and countermeasures against leaks are being promoted. The US first enacted the “Superfund Law” in 1980 as a law for measures against soil contaminated with petroleum hydrocarbons. This law requires all parties involved in soil contamination to pay for purification costs, etc., and the total petroleum hydrocarbon (TPH) concentration in the soil must be less than 1,000 mg / kg.

  In Japan, the “Soil Contamination Countermeasures Law” was enacted in 2002, but oil was not targeted for pollutants because of the lack of adequate countermeasures against petroleum hydrocarbon contamination. Later, in 2006, the “Oil Pollution Countermeasure Guidelines-Approaches to Land Owners' Response to Oil Odor / Oil Film Problems Caused by Soil Containing Mineral Oil” was announced. It was necessary to eliminate oil odor and reduce oil concentration in soil. Furthermore, since April 2010, the amendment of the “Soil Contamination Countermeasures Law” restricted the transportation of contaminated soil, and it became necessary to purify contaminated soil as much as possible.

  At present, incineration and thermal decomposition treatment using heavy oil is mainly performed for purification of petroleum hydrocarbon-contaminated soil. In these methods, the contaminated soil must first be dug up and transported to a treatment plant. However, this treatment method is not suitable because the amendment of the Soil Contamination Countermeasures Law restricts the transportation of contaminated soil. Incineration requires 10 times as much fuel as polluted oil, and there is a problem that the cost varies greatly depending on the oil price. Furthermore, since the soil after incineration is free of organic matter including microorganisms, it is difficult to reuse the soil.

  Therefore, in recent years, research on bioremediation that purifies contamination by microbial function is in progress. Bioremediation is more resource-saving than incineration and cleaning, and has the advantage that soil can be reused. Furthermore, since the soil can be purified in situ, further spread is expected in future revisions to the Soil Contamination Countermeasures Law. However, bioremediation has drawbacks such as longer time for purification than conventional methods.

  Bioremediation includes biostimulation in which microorganism nutrients are administered to activate indigenous microorganisms, and bioaugmentation in which microorganisms having a resolution of pollutants are introduced from the outside.

  In biostimulation, administration of nutrients increases petroleum degrading bacteria in the soil and promotes oil breakdown. However, it is difficult to maintain the petroleum hydrocarbon decomposition activity of microorganisms, and there remains a problem in shortening the processing time. In bioaugmentation, long-chain linear alkanes, aromatic, long-chain cyclic alkanes and the like, which are petroleum components that are likely to remain in the soil, can be decomposed by administering nutrient salts and petroleum-degrading bacteria from the outside. However, since it is necessary to confirm the safety of the oil-degrading bacteria to be administered and the presence or absence of harmful intermediate products, various problems remain for the spread of bioaugmentation.

  In order to improve the efficiency of bioremediation of petroleum-contaminated soil, the present inventors have isolated petroleum-degrading bacteria capable of degrading persistent hydrocarbons (Patent Document 1). In addition, it has been reported that a microorganism preparation for bioremediation with high degradability can be obtained by performing pre-culture and main culture using a medium having a specific composition (Patent Document 2). Furthermore, it has been reported that by adjusting the weight and ratio of nutrient components (Total-C, Total-N, Total-P) in the soil to a specific range, the number of soil microorganisms can be increased and maintained, and oil decomposition can be promoted. (Patent Document 3).

JP 2007-135425 JP JP 2008-228623 A JP 2012-71255 A

  However, both biostimulation and bioaugmentation are desired to further improve the efficiency of oil pollution purification.

  Accordingly, an object of the present invention is to provide a method for purifying oil-contaminated soil with high efficiency of oil pollution purification. Another object of the present invention is to provide a composition for purifying oil-contaminated soil with high efficiency of oil pollution purification.

  In order to purify oil-contaminated soil, it is considered that a higher effect can be obtained by using a material containing a large number of petroleum degrading bacteria. Therefore, the present inventor examined the distribution of petroleum-decomposing bacteria in compost and found that the number of petroleum-decomposing bacteria in compost was larger than that in natural soil. As a result, the present inventor achieves the above object by adding compost containing petroleum degrading bacteria to petroleum-contaminated soil, and further adjusting the weight ratio of nutrient components in the oil-contaminated soil to a specific range. I got the knowledge that I can do it.

  The present invention has been completed based on these findings and has been completed. The present invention provides the following method for purifying oil-contaminated soil and a composition for purifying oil-contaminated soil.

Item 1. By adding organic materials containing petroleum-degrading bacteria to oil-contaminated soil, the total carbon content in the oil-contaminated soil (excluding the amount of carbon in oil) is reduced to 10,000-60,000 mg / kg, and oil-contaminated soil A method for purifying oil-contaminated soil, including a step of adjusting the C / N ratio in the inside to 8-16.
Item 2. Item 2. The method according to Item 1, wherein the organic material contains petroleum degrading bacteria in an amount of 1 × 10 ⁶ cells / g or more.
Item 3. Item 3. The method according to Item 1 or 2, wherein the organic material is a composition containing compost as a main component.
Item 4. The organic material is compost, the total carbon content in the compost is 150,000 mg / kg or more, the total nitrogen content is 8,000 mg / kg or more, and the C / N ratio is 18 to 30. The method according to 1 or 2.
Item 5. A composition for purifying petroleum-contaminated soil containing petroleum degrading bacteria, having a total carbon content of 150,000 mg / kg or more, a total nitrogen content of 8,000 mg / kg or more, and a C / N ratio of 18-30.

  According to the method for purifying petroleum-contaminated soil of the present invention, the number of petroleum-decomposing bacteria in the soil can be increased and maintained, and it becomes possible to efficiently purify oil contamination.

10 is a graph showing changes in oil concentration in Test Example 3. ○, Mineral salt added; □, Fermented chicken manure added It is a graph which shows the change of the total number of bacteria in Experiment 3. ○, Mineral salt added; □, Fermented chicken manure added 10 is a graph showing changes in the number of petroleum-degrading bacteria in Test Example 3. ○, Mineral salt added; □, Fermented chicken manure added It is a graph which shows the relationship between the kind of organic material (compost) in Test Example 4, and an oil content decomposition rate.

  Hereinafter, the present invention will be described in detail.

  Definitions of terms used in the present specification are shown below.

“Total carbon” (sometimes referred to herein as TC) means the sum of organic and inorganic carbon in the soil. Total carbon can be measured with a total organic carbon meter (TOC-V _CPH , Shimadzu Corporation, Kyoto).

  “Total nitrogen” (sometimes referred to herein as TN) means the sum of organic and inorganic nitrogen in the soil. Total nitrogen can be measured by potassium peroxodisulfate decomposition-spectrophotometry or the like.

  “C / N ratio” means the ratio of total carbon / total nitrogen (TC / TN).

Method for purifying oil-contaminated soil The method for purifying oil-contaminated soil according to the present invention comprises adding an organic material containing petroleum-decomposing bacteria to the oil-contaminated soil, so that the total carbon content in the oil-contaminated soil (however, And a step of adjusting the C / N ratio in petroleum-contaminated soil to 8 to 16 in the oil-contaminated soil.

  The oil-contaminated soil in the present invention is not particularly limited as long as it is oil-contaminated soil that can be purified by the method of the present invention. For example, the oil-contaminated soil is contaminated with gasoline, kerosene, crude oil, light oil, heavy oil, lubricating oil, engine oil, etc. Soil. Examples of such soils include factory sites, factory sites, gas station sites, incinerators, pipeline areas, oil pollution accident sites, and the like.

  Specific examples of hydrocarbons contained in petroleum-contaminated soil include cycloalkanes such as cyclopropane, cyclobutane, cyclopentane, cycloheptane, cyclohexane, cyclooctane, and decalin; benzene, toluene, ethylbenzene, xylene, phenol, cresol, etc. Monocyclic aromatic hydrocarbons; polycyclic aromatic hydrocarbons such as naphthalene, anthracene, phenanthrene, biphenyl, phenolphthalein, triphenylmethane; 1,1-dichloroethane, chloroform, 1,2-dichloropropane, dibromochloromethane 1,1,2-trichloroethane, 2-chloroethyl vinyl ether, tetrachloroethene (PCE), chlorobenzene, 1,2-dichloroethane, 1,1,1-trichloroethane, bromodichloromethane, trans-1,3-dichloropropene, Cis-1,3-dichloropropene Bromoform, chloromethane, bromomethane, vinyl chloride, chloroethane, 1,1-dichloroethene, trans-1,2-dichloroethene, trichloroethene (TCE), dichlorobenzene, cis-1,2-dichloroethene, dibromoethane, 1 Halogen-containing hydrocarbons such as 1,4-dichlorobutane, 1,2,3-trichloropropane, bromochloromethane, 2,2-dichloropropane, 1,2-dibromomethane, 1,3-dichloropropane; Examples of hydrocarbons include long-chain cyclic hydrocarbons.

The organic material in the present invention is not particularly limited as long as it contains petroleum degrading bacteria and can adjust the total carbon content and C / N ratio in the petroleum-contaminated soil to the target range. The number of degrading bacteria is preferably 1 × 10 ⁶ cells / g or more, more preferably 1 × 10 ⁷ to 1 × 10 ¹⁰ cells / g or more.

  The petroleum decomposing bacteria in the present invention refers to bacteria capable of decomposing petroleum, particularly hydrocarbons contained in petroleum. Examples of such petroleum-degrading bacteria include, for example, Gordonia, Rhodococcus, Acinetobacter, Bacillus, Pseudomonas, Achromobacter, and Alkaligenes. Examples include bacteria of the genus (Alcaligenes), Mycobacterium, Sphingomonas, Ralstonia and the like.

  The number of petroleum-decomposing bacteria in organic materials and petroleum-contaminated soil can be determined, for example, by the method described in the examples. In the method described in the Examples, petroleum degrading bacteria can be quantified specifically with high sensitivity.

  As an organic material in this invention, the composition which contains compost as a main component can be mentioned, for example. Compost is desirable because it contains a relatively large amount of petroleum degrading bacteria. Examples of compost include plant compost such as bark compost, horse manure compost, chicken manure compost, cattle manure compost, livestock compost such as pig manure compost, and seaweed compost. Compost may be used alone or in combination of two or more. “Contains compost as a main component” means that organic compost is usually contained in an amount of 50% by weight or more, preferably 60 to 80% by weight.

  To the composition containing compost as a main component, subcomponents other than compost are added for the purpose of adjusting the amount of total carbon or total nitrogen in the composition to a suitable range. When the total carbon in the compost is insufficient, it is desirable to add a secondary component having a high total carbon content compared to the total nitrogen. Examples of such secondary raw materials include straw straw and rice husk. It is done. When the total nitrogen in the compost is insufficient, it is desirable to add a secondary component having a high total nitrogen content compared to the total carbon. Examples of such secondary raw materials include urea, ammonium nitrate, and nitric acid bitters. Ammonium, ammonium chloride, ammonium sulfate, ammonium phosphate, sodium nitrate, calcium nitrate, potassium nitrate, lime nitrogen, soybean meal, fish meal and the like can be mentioned.

  As the organic material in the present invention, compost having a total carbon content of 150,000 mg / kg or more, a total nitrogen content of 8,000 mg / kg or more, and a C / N ratio of 18 to 30 is preferably used. Can do. As described above, compost contains a relatively large number of petroleum-decomposing bacteria, and therefore, compost satisfying the above range is excellent in increasing and maintaining the number of petroleum-degrading bacteria. In addition, although the example of patent document 3 uses the chicken manure compost, the chicken manure compost does not normally satisfy said C / N ratio. The total carbon content is preferably 20,000 mg / kg or more, the total nitrogen content is preferably 10,000 mg / kg or more, and the C / N ratio is preferably 20-25.

  By adjusting the total carbon content in the oil-contaminated soil (excluding the carbon content of oil) to 10,000-60,000 mg / kg and the C / N ratio in the oil-contaminated soil to 8-16, It is possible to grow the degrading bacteria and maintain the number of bacteria after the growth. The total carbon content in the oil-contaminated soil (excluding the carbon content of oil) is preferably 30,000-60,000 mg / kg, and the C / N ratio in the oil-contaminated soil is preferably 10-14. is there.

  In adjusting the total carbon content and C / N ratio, for example, after measuring the total carbon and total nitrogen content of oil-contaminated soil and organic materials to be added, after mixing the oil-contaminated soil and organic materials, The mixing ratio is determined so that the total carbon content and the C / N ratio are within the above range, and the organic material is added to the petroleum-contaminated soil at the mixing ratio. The amount of the organic material added to the petroleum-contaminated soil is usually 1 to 10% by weight, preferably 2 to 8% by weight.

  The number of days required for purifying petroleum-contaminated soil by the purification method of the present invention is usually 1.5 months or more, preferably 2 to 6 months.

  According to the method for purifying petroleum-contaminated soil of the present invention, the number of petroleum-decomposing bacteria in the soil can be increased and maintained, and it becomes possible to efficiently purify oil contamination.

Composition for purifying oil-contaminated soil The composition for purifying oil-contaminated soil of the present invention contains petroleum-degrading bacteria, has a total carbon content of 150,000 mg / kg or more, and a total nitrogen content of 8,000 mg / kg or more. , And the C / N ratio is 18-30.

  The oil-contaminated soil and the oil-decomposing bacteria are the same as described above.

The number of petroleum-degrading bacteria in the purification composition is preferably 1 × 10 ⁶ cells / g or more, more preferably 1 × 10 ⁷ to 1 × 10 ¹⁰ cells / g or more.

  Examples of the purification composition include a composition composed only of compost or a composition containing compost as a main component. Compost is desirable because it contains a relatively large amount of petroleum degrading bacteria. Examples of compost include plant compost such as bark compost, horse manure compost, chicken manure compost, cattle manure compost, livestock compost such as pig manure compost, and seaweed compost. Compost may be used alone or in combination of two or more. In addition, although the example of patent document 3 uses the chicken manure compost, the chicken manure compost does not normally satisfy said C / N ratio.

  To the composition containing compost as a main component, subcomponents other than compost are added for the purpose of adjusting the amount of total carbon or total nitrogen in the composition to a suitable range. Examples of the auxiliary component include those described above. In the case of a composition consisting only of compost, not all composts satisfy the above range, so it is necessary to select a compost that satisfies the above range.

  The total carbon content is preferably 200,000 mg / kg or more, the total nitrogen content is preferably 10,000 mg / kg or more, and the C / N ratio is preferably 20-25.

  The amount of the purification composition of the present invention added to petroleum-contaminated soil is usually 1 to 10% by weight, preferably 2 to 8% by weight.

  The number of days required for purifying petroleum-contaminated soil with the purification composition of the present invention is usually 1.5 months or more, preferably 2 to 6 months.

  By the purification composition of the present invention, the number of petroleum-decomposing bacteria in the soil can be increased and maintained, and it becomes possible to efficiently purify petroleum pollution.

  Examples are given below to illustrate the present invention in more detail. However, the present invention is not limited to these examples.

Experimental method and total bacterial count
Weigh 1.0 g of soil into a 50 ml centrifuge tube, add 8.0 ml of DNA extraction buffer solution (pH 8.0) shown in Table 1 and 1.0 ml of 20% (w / v) sodium dodecyl sulfate solution, 1,500 rpm, at room temperature. Stir for 20 minutes. After stirring, 1.5 ml was taken from a 50 ml centrifuge tube into a sterilized 1.5 ml microtube and centrifuged at 16 ° C. and 8,000 rpm for 10 minutes. 700 μl of the aqueous layer was taken into a new microtube, 700 μl of phenol / chloroform / isoamyl alcohol (25: 24: 1, v / v) was added and mixed, and then centrifuged at 16 ° C. and 13,000 rpm for 10 minutes. After centrifugation, 500 μl of the aqueous layer was taken into a new microtube, 300 μl of 2-propanol was added, gently mixed, and centrifuged at 16 ° C. and 13,000 rpm for 15 minutes. After centrifugation, the supernatant was removed, 500 μl of 70% (v / v) ethanol was added, and the mixture was centrifuged at 16 ° C. and 13,000 rpm for 5 minutes. After centrifugation, the supernatant was removed and dried under reduced pressure with an aspirator for 30 minutes. To this, 50 μl of TE 10: 1 buffer solution (pH 8.0) shown in Table 2 was added and dissolved well, and this was used as an environmental DNA solution.

Distilled water was added to 2.0 g of agarose, 4.0 ml of 50 × TAE buffer (pH 8.0) shown in Table 3 and 20 μl of 0.1 mM ethidium bromide solution to make 200 ml, and a 1.0% agarose gel was prepared. 1.0 μl of loading dye (Toyobo, Osaka) was mixed with 5.0 μl of the environmental DNA solution, and a total amount of 6.0 μl and 1.5 μl of a smart ladder (Nippon Gene, Toyama) containing a known amount of DNA were applied to an agarose gel. After electrophoresis at 100 V for 40 minutes, the agarose gel was irradiated with UV to confirm the DNA band. A smart ladder DNA band was analyzed using KODAK 1D Image Analysis software (KODAK, NY, USA), and a calibration curve of DNA amount against fluorescence intensity was prepared. Using this calibration curve, the amount of DNA was determined from the fluorescence intensity of the DNA band of each sample DNA solution, and the amount of environmental DNA per 1.0 g of each soil was calculated using the following formula.
Y = 4.0 × 10 ⁹ X (R ² = 0.99) [Y: soil bacteria count (cells / g-soil), X: environmental DNA amount (μg / g-soil)]
Was used to calculate the number of soil bacteria.

-Number of petroleum degrading bacteria Environmental DNA solution and agarose gel were prepared by the same method as described above. To 15 μl of the environmental DNA solution, 2.0 μl of a loading die (Toyobo, Osaka) was mixed, and a total amount of 17 μl was applied to an agarose gel. After electrophoresis at 100 V for 40 minutes, the agarose gel was irradiated with UV to confirm the DNA band. The DNA band was cut out from the agarose gel and the environmental DNA was purified. KAPA SYBR FAST qPCR Master Mix 10 μl, 10 μM forward primer (5′-AACTAYMTCGARCAYTAYGG-3 ′) and reverse primer (5′-TGRTCKSWRTGNCGYTGVARGTG-3 ′) 1 μl, ROX high 0.4 μl, purified environmental DNA 1 to 1 A 20 μl reaction solution containing 5 μl was added to a 200 μl tube and set in an Applied Biosystems 7300 Real Time System (Applied Biosystems, USA) to perform real-time PCR. PCR reaction conditions were 95 ° C for 5-10 minutes, followed by 40 cycles of 95 ° C for 15-30 seconds and 60 ° C for 30-60 seconds. Of the samples used for real-time PCR, KAPA SYBR and ROX high were used according to the protocol of KAPA SYBR qPCR kit (KAPA BIOSYSTEMS, Osaka). The number of petroleum-degrading bacteria was calculated from the obtained Ct value using the following formula.
Number of petroleum-degrading bacteria (cells / g-sample) = (3 × 10 ¹⁴ ) × e ^{(-0.516 × Ct value)}
By this method, petroleum degrading bacteria can be quantified specifically with high sensitivity.

-Oil content analysis The oil content contained in the sample was analyzed by IR (HORIBA oil content analyzer OCMA-355, Horiba, Kyoto).

-Measurement of total carbon (TC) TC of the sample was measured using a total carbon meter (TOC-V CPH, Shimadzu Corporation, Kyoto).

Test Example 1 (Distribution of petroleum degrading bacteria in soil)
In biostimulation, it is important to know the number of indigenous petroleum-degrading bacteria. Therefore, we investigated the distribution of petroleum-degrading bacteria in various soils using a newly designed primer set. The total number of bacteria and the number of petroleum-degrading bacteria were examined by the above methods. The results are shown in Table 4.

  Petroleum-degrading bacteria were detected in all the soils used in this test. This suggested that petroleum-degrading bacteria are widely distributed in the environmental soil. The ratio of petroleum degrading bacteria in the total number of bacteria was 0.10-4.32%. It is known that ammonia-oxidizing bacteria and nitrite-oxidizing bacteria that play a role in the natural nitrogen cycle are present at a rate of 0.002 to 4.2%, and petroleum-degrading bacteria were present at almost the same rate as these bacteria.

Test Example 2 (Distribution of petroleum-degrading bacteria in compost)
In order to purify oil-contaminated soil, it is considered that a higher effect can be expected by using materials containing a large number of oil-degrading bacteria. Therefore, the distribution of petroleum degrading bacteria in compost was investigated. The results are shown in Table 5.

  The total number of bacteria and the number of oil-degrading bacteria contained in compost showed a tendency to be higher than that of natural soil. In addition, the number of petroleum degrading bacteria in chicken manure compost tended to be higher than other composts.

Test Example 3 (Efficient bioremediation by activating indigenous petroleum-degrading bacteria)
In order to investigate whether bioremediation of petroleum-contaminated soil would be efficient by using organic materials containing many petroleum-degrading bacteria, the relationship between the oil concentration, the total number of bacteria, and the number of petroleum-degrading bacteria was analyzed.

The organic material is fermented chicken manure (Agrienuwai) and added so that the soil TC is 20,000 mg / kg-soil (5% added) and the C / N ratio is 8, and the inorganic salt [4 × MSW (per liter: 4.84 g (NH ₄ ) ₂ NO ₃ , 57.28 g Na ₂ HPO ₄・ 12H ₂ O, 21.78 g KH ₂ PO ₄ , 2 g NaCl, 0.986 g MgSO ₄ , 11 mg FeSO ₄・ 7H ₂ O, 59 mg CaCl ₂・ 2H ₂ O, 0.801 mg ZnSO ₄・ 7H ₂ O, 0.06 mg (NH ₄ ) ₆ Mo ₇ O ₂₄・ 4H ₂ O, 0.08 mg CuSO ₄・ 5H ₂ O, 0.16 mg CoCl ₂・ 6H ₂ O, and compared _{0.06 mg MnSO 4 · 5H 2 O} , 2 g polypeptone, and 1 g yeast extract)] and conventional bioremediation using. Petroleum-contaminated soil was prepared by adding base oil of automobile engine oil to 5,000 mg / kg-soil. Fig. 1 shows changes in the oil concentration, Fig. 2 shows changes in the total number of bacteria, and Fig. 3 shows changes in the number of petroleum-degrading bacteria.

  The oil concentration decomposed 30% base oil in 28 days when inorganic salt was added. On the other hand, 47% of the base oil was degraded in 28 days in the soil added with fermented chicken manure.

The number of soil bacteria increased to 1.8 × 10 ¹⁰ cells / g-soil in 7 days when inorganic salt was added, but then decreased to 6.8 × 10 ⁹ cells / g-soil. On the other hand, in the soil to which fermented chicken manure was added, the number increased to 7.1 × 10 ¹⁰ cells / g-soil in 14 days, and the number of bacteria was maintained up to 3.3 × 10 ¹⁰ cells / g-soil on the 28th day.

The number of petroleum-degrading bacteria increased to 2.0 × 10 ⁹ cells / g-soil in 7 days when inorganic salts were added, but then decreased to 1.4 × 10 ⁸ cells / g-soil. On the other hand, in soil to which fermented chicken manure was added, it increased to 3.7 × 10 ⁹ cells / g-soil in 7 days and maintained a relatively high number of bacteria at 2.7 × 10 ⁹ cells / g-soil until 21 days thereafter. Was.

  From the above results, by adding fermented chicken manure and adjusting TC to 10,000 mg / kg or more and C / N ratio to 8 or more, the total number of bacteria and the number of petroleum-degrading bacteria are maintained high, promoting oil degradation It is thought that it was connected to.

Summary There are relatively many oil-degrading bacteria in compost, and many oil-decomposing bacteria existed especially in chicken manure compost. By adding fermented chicken manure to oil-contaminated soil and adjusting the TC and C / N ratio to a certain range, the soil bacteria and petroleum-degrading bacteria increased and maintained high, and the oil decomposition was also promoted.

Test Example 4 (Efficiency of bioremediation by using fermented cow manure compost whose total carbon, total nitrogen, and C / N ratio satisfy the scope of claim 4)
Light oil was added to 5,000 mg / kg of soil with TC of about 1,000 mg / kg to make this soil oil-contaminated soil. Add fermented beef manure compost (manufactured by Tosho) or chicken manure compost (manufactured by Sakamoto Sangyo) shown in Table 6 and mix them at room temperature so that the TC is about 10,000 mg / kg (excluding TC of oil) in oil-contaminated soil. Let stand for 13 days. The oil content in the soil was determined by IR. The result is shown in FIG.

  The use of fermented cow dung in which the total carbon, total nitrogen, and C / N ratio in the compost satisfy the range of claim 4 promoted oil decomposition compared to the case of using fermented chicken dung. This is probably because fermented chicken manure contains a large amount of nitrogen components (C / N ratio is small), so that the decomposition of oil was inhibited due to the high ammonia component in the soil after the addition of the material.

Test Example 5 (Efficiency of bioremediation by adjusting TC and C / N ratio)
The engine oil base oil (Shin Nippon Oil) was added so that the TC would be 5,000 mg / kg to the 2,000 mg / kg oil-contaminated soil. Chicken manure compost (manufactured by Agrienuwai Co., Ltd.) was added to the oil-contaminated soil and mixed so that TC was 10,000 mg / kg (excluding TC of oil), and allowed to stand at room temperature for 28 days. The oil content in the soil was determined by IR. The results are shown in Table 7.

  Decreasing oil content was observed by adjusting TC and C / N ratio by chicken manure compost. The soil that did not adjust TC and C / N ratio did not show any decrease in oil content. It is thought that petroleum-degrading bacteria in the soil were activated by adjusting TC and C / N ratio.

Claims (2)

By adding organic materials containing petroleum-degrading bacteria to oil-contaminated soil, the total carbon content in the oil-contaminated soil (excluding the amount of carbon in oil) is reduced to 10,000-60,000 mg / kg, and oil-contaminated soil A method for purifying oil-contaminated soil, including a step of adjusting the C / N ratio in the inside to 8-16,
The organic material contains petroleum degrading bacteria in an amount of 1 × 10 ⁶ cells / g or more,
The organic material is compost, the total carbon content in the compost is 150,000 mg / kg or more, the total nitrogen content is 8,000 mg / kg or more, and the C / N ratio is 18-30. .   The method according to claim 1, wherein the organic material is a composition containing compost as a main component.

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