JP2001079538A - Aqueous composition for biologically restoring contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively promote the propagation of contaminant decomposing bacteria and to efficiently clean the contaminated soil by incorporating a slowly available nitrogenous fertilizer, protein and a clay mineral to prepare an aq. composition for biologically restoring the contaminated soil. SOLUTION: An aq. composition effective to clean the soil contaminated with the oil leaked from a gas station, etc., is formed by incorporating a slow- release nitrogenous fertilzer, protein and a clay mineral. IB urea, CDV urea, uraform, guanyl urea phosphate, oxamide, coated urea, etc., are exemplified as the slowrelease nitrogenous fertilizer. Casein, gelatin, collargen, keratin, albumin, ceresin, sein, etc., are exemplified as the protein, and zeolite activated clay, bentonite, diatomaceous earth, etc., are used as the clay mineral. Mineral oil, animal and vegetable oil and poisonous chemical substance, etc., are exemplified as the contaminant, and the aq. composition is directly sprayed on the soil contaminated with the contaminant to clean the contaminated soil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to soil and various types of soil contaminated with oil spilled from shore (including reefs), riverbeds, gas stations, etc., which are contaminated with oil spilled from oil tankers and oil storage bases. The present invention relates to an aqueous composition effective for purifying soil and the like contaminated with toxic effluent chemicals from factories and the like by biological remediation.

[0002]

2. Description of the Related Art Conventionally, a bioremediation method for contaminated soil has been proposed in which a microorganism using a contaminant-resolving microorganism existing in the contaminated soil is used, and a microorganism having a contaminant-resolving power which is additionally sprayed on the contaminated soil. It is roughly divided into the method of using.

The former includes (1) a method of spraying a composition containing a paraffin-treated water-soluble nitrogen-containing compound and a phosphorus-containing compound (see JP-A-50-40780), and (2) diguanidinium salts. A method of spraying a composition containing a surfactant (see JP-A-58-153530 and JP-A-59-82995); (3) an aqueous solution (dispersed phase) containing a nitrogen-containing compound and a phosphorus-containing compound; A method of spraying a microemulsion composed of an oil-miscible organic liquid (dispersion medium) (see JP-B-58-49232 and JP-B-61-11590) and (4) a cyclic amide in which a metal essential for microbial growth is chelated. A method of spraying the contained proliferating agent (see US Pat. Nos. 5,571,715 and 5,849,193) and the like have been proposed.

As the latter, (5) a method of spraying a high-density growth medium containing an additive such as proline or betaine together with the microorganism (see Japanese Patent Application Laid-Open No. 9-271749); A method of spraying a mixture of microorganisms and composted chicken manure (see US Pat. No. 5,656,486) has been proposed.

[0005] However, the method (1) has a drawback that the decomposition efficiency of the soil pollutant is low because paraffin imposes a load on microorganisms, and the method (2) has a disadvantage that it is more expensive than water-soluble inorganic nutrients. The method has the disadvantage of being low in practicality in terms of cost due to the necessity of a nitrogen organic compound. Further, in the case of the method (3), the microemulsion is separated in a relatively short time, so that the nitrogen-containing compound or There is a problem that not only does the phosphorus-containing compound flow out of the contaminated area to be treated, but also the organic dispersion medium imposes a load on microorganisms, so that the efficiency of decomposition of the soil pollution source is low. Furthermore, method (4),
(5) and (6) have a drawback that microbial growth factors such as nitrogen-containing compounds dissolve and diffuse into water and flow out of the contaminated area to be treated.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the art, and provides an aqueous composition effective for efficiently purifying contaminated soil by effectively promoting the growth of pollutant-degrading bacteria. It was made to provide.

[0007]

That is, the present invention relates to an aqueous composition for biologically remediating contaminated soil, comprising a slow-release nitrogenous fertilizer, a protein and a clay mineral.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The slow-release nitrogenous fertilizer used in the present invention means a fertilizer that gradually releases ammonium ions. Examples of such fertilizers include IB urea (isobutyraldehyde processed urea) and CDU urea (acetaldehyde). Modified urea), uraform (formaldehyde processed urea), guanyl urea phosphate, oxamide, coated urea, and the like. These may be used in combination of two or more as needed. The slow-release nitrogenous fertilizer is particularly effective as a growth factor of the pollutant-decomposing bacteria in that the nitrogen source can be retained in the contaminated soil for a long time. The amount of the slow-release nitrogen-containing fertilizer depends on the type of the polluting source, the soil quality of the contaminated soil, the temperature at the site, and the like, and is not particularly limited, but is usually 10 to 90% by weight, preferably 30 to 80% by weight. is there.

Examples of the protein used in the present invention include casein, gelatin, collagen, keratin, albumin, sericin, zein and the like, and these may be used in combination of two or more as needed. Such a protein is particularly effective as a growth factor of a contaminant-degrading bacterium in that amino acids generated after its hydrolysis can be immediately used as a protein source. The amount of the protein is also dependent on the type of the contamination source, the soil quality of the contaminated soil, the temperature at the site, and the like, but is not particularly limited, but is usually 1 to 20% by weight, preferably 5 to 15% by weight.

Examples of the clay mineral used in the present invention include zeolite, activated clay, bentonite, diatomaceous earth and synthetic hectorite, and these may be used in combination of two or more. Preferred clay minerals are those having high water dispersibility, for example, synthetic hectorite having a particle size of 20 to 30 nm. Such a clay mineral is particularly effective as a component of an aqueous composition for biologically remediating contaminated soil, in that it adsorbs ammonium ions and proteins and retains it in the contaminated soil. The amount of the clay mineral is not particularly limited, but is usually 0.1 to 5% by weight, preferably 0.5 to 2% by weight. If the amount of the clay mineral is too small, the slow-release nitrogenous fertilizer and protein are likely to dissolve and diffuse into water and flow out of the contaminated soil area. Not only is efficiency reduced, but wasteful.

The aqueous composition according to the present invention can be prepared by mixing the above-mentioned slow-release nitrogenous fertilizer, protein and clay mineral with water to a desired concentration. If desired, other conventional growth factors such as fatty acid amide and alkyl ether phosphoric acid may be appropriately added to the aqueous composition.

The aqueous compositions according to the present invention are useful for cleaning soils (including shores and riverbeds) contaminated by various sources by biological remediation. Pollution sources include mineral oils (eg, crude oil, heavy oil, light oil, kerosene, etc.), animal and vegetable oils (eg, soybean oil, linseed oil, and funnel oil, etc.) and toxic chemicals (eg, tetrachloroethylene, trichloroethylene, dichloroethylene, PCB, etc.). Is exemplified.

The aqueous composition may be applied directly to soil contaminated with such a source. The amount of application depends on the type of the contamination source, the geological characteristics of the contaminated soil, the type and amount of the components in the composition, the temperature at the site, etc., and is not particularly limited. 20% by weight
It is.

Microorganisms capable of degrading contaminants that live in contaminated soil are actively multiplied by utilizing growth factors in the composition, so that decomposition of the contaminants is promoted and contaminated soil is effectively purified. You. In this case, the action of the clay mineral contained in the composition prevents the premature outflow of the growth factor from the contaminated soil area, and the decomposition rate of the contaminant is maintained at a high level over time. Soil purification is done efficiently.

In order to further promote the purification of the contaminated soil, a known microorganism having a decomposability for the contaminant may be additionally sprayed together with the aqueous composition. Flavobact which has petroleum resolution as such microorganisms
erium sp. (Journal of the Oceanographic Society of Japan, vol. 32, p. 242-
248 (1976)), Can with oil resolution
dida sp. (Journal of Biotechnology, Vol. 73, No. 4, 295
Pp. 299 (1995)), with crude oil resolution
Pseudomonas sp. And Caulobacter sp. (Journal of
the Oceanographical Society of Japan, Vol. 41,
337-344 (1985)), Coryneforms and Moraxella sp.
on Suisan Gakkaishi, Vol. 55, No. 6, No. 1091
Pp. 1095 (1989)) and Coryn having the ability to decompose chlorine-containing organic compounds such as trichloroethylene.
ebacterium sp. and Pseudomonas sp.
271749) and the like.

[0016]

The present invention will be described below with reference to examples. Examples 1 and 2 3 g of the aqueous composition prepared according to the formulation (% by weight) shown in Table 1 was mixed with 30 g of mousse artificially prepared using 1 kg of sea sand and 500 g of C heavy oil, and 45 g of the mixture was mixed with polypropylene. (100 ml). The cylinder was set in a tide device using natural seawater, and tide was performed for 30 days. At the start of the test, 15 days and 30 days later, the oil in the sample collected from the cylinder was extracted with chloroform. The extracted oil was subjected to a dehydration treatment with anhydrous sodium sulfate, and then the solvent was removed and weighed. On the other hand, alkanes in the extracted oil were analyzed by gas chromatography, and the degree of biodegradation of heavy oil was evaluated based on the ratio of n-C17 / pristane and n-C18 / phytan. The results are shown in FIG. 1 and FIG. The vertical axis indicates the degree of biodegradation, and the horizontal axis indicates the number of tide sunsets. In the figure,
“O” and “□” indicate the results of Examples 1 and 2, respectively.

[0017]

[Table 1]

Comparative Examples 1 to 3 FIGS. 1 and 2 show test results obtained by using the compositions prepared according to the formulations shown in Table 1 and by the same procedure as in the examples. In the figure, “●”, “■”, and “」 ”indicate the results of Comparative Examples 1, 2, and 3, respectively.

[0019]

By using the aqueous composition according to the present invention, the conventional problems in the field can be solved and the growth of the pollutant-degrading bacteria can be effectively promoted, whereby the contaminated soil can be efficiently removed. Can be purified.

[Brief description of the drawings]

FIG. 1 is a graph showing the time-dependent change in the degree of biodegradation of fuel oil (n-C17 / pristane) in Examples and Comparative Examples. The vertical axis indicates the degree of biodegradation, and the horizontal axis indicates the number of tidal days.

FIG. 2 is a graph showing a time-dependent change in the degree of biodegradation of fuel oil (n-C18 / phytan) in Examples and Comparative Examples. The vertical axis shows the degree of biodegradation of heavy oil, the horizontal axis shows the tide days,

[Explanation of symbols]

“○” indicates the result of Example 1. “□” indicates the result of Example 2. “●” indicates the result of Comparative Example 1. “■” indicates the result of Comparative Example 2. “▲” indicates the result of Comparative Example 3.

Claims (7)

[Claims] 1. An aqueous composition for the biological remediation of contaminated soil, comprising a slow-release nitrogenous fertilizer, a protein and a clay mineral. 2. The aqueous composition according to claim 1, wherein the slow-release nitrogenous fertilizer is a fertilizer selected from the group consisting of IB urea, CDU urea, uraform, guanyl urea phosphate, oxamide and coated urea. 3. The aqueous composition according to claim 1, wherein the protein is a protein selected from the group consisting of casein, gelatin, collagen, keratin, albumin, sericin, and zein. 4. The aqueous composition according to claim 1, wherein the clay mineral is a clay mineral selected from the group consisting of zeolite, activated clay, bentonite, diatomaceous earth and synthetic hectorite. 5. The aqueous composition according to claim 1, wherein the contaminated soil is a soil contaminated by a contaminant selected from the group consisting of mineral oil, animal and vegetable oils, and chlorine-containing organic compounds. 6. A method for biologically remediating contaminated soil, comprising spraying the aqueous composition according to claim 1 on contaminated soil. 7. A method for biologically remediating contaminated soil, which comprises spraying the aqueous composition according to claim 1 on contaminated soil together with a known microorganism capable of resolving the contaminated source.