RU2320430C1 - Method of biological recultivating soils contaminated with oil products - Google Patents

Abstract

FIELD: soil recultivation.

SUBSTANCE: method comprises cutting slots in vertical and horizontal directions and trenches by a depth of 60-80 cm, filling them with zoo bacteria fertilizer , applying sapropel composition, manure, and fresh soil in 5-7 days, applying water solution of oil-decomposing Rhodoccus sp. MNF bacteria, plowing, harrowing, and seeding multiannual grasses.

EFFECT: enhanced efficiency.

4 cl, 3 dwg

Description

The invention relates to environmental technologies and can be used to restore over-compacted soils contaminated with oil and oil products.

In areas of oil fields and in the territories through which oil pipelines pass, soil contamination with oil and oil products occurs, leading to a loss of land productivity, and often complete degradation of landscapes. The process of tearing away land from agricultural use is becoming increasingly widespread. This is due to the fact that during the repair of pipelines for pumping (transporting) liquid, gaseous and other media, an exclusion zone of 50-150 m wide is provided for passage of construction, road and repair equipment, as well as for storage of materials for various purposes.

As a result of the impact of the supports of the chassis of heavy equipment, soil compaction to a depth of more than 1.0 m occurs, the structural units of the surface layer are destroyed, as well as oil pollution.

Currently, the use of microorganisms introduced into the soil is considered to be the most advanced technology for cleaning oil-contaminated soils.

Known methods for cleaning oil-contaminated soils using microorganisms Pscudomonas aeruginoza PAO, Actinomyces flavus, Pseudomonas putida 36 [1, 2, 3].

The disadvantage of this method is the incomplete decomposition of oil due to the selective action of destructors on certain fractions of petroleum products. In this case, only the upper layers of pollution (0-20 cm) are destroyed. The methods do not provide soil remediation.

A known method of purifying soils from oil products using a consortium of strains of microorganisms-destructors, which is applied to the soil after plowing [4].

However, the method is effective for surface soil contamination, not more than 20%.

EFFECT: development of an effective method for biological reclamation of soils contaminated with oil and oil products, including re-compacted and highly polluted ones, by utilizing bottom sediments of fresh water bodies (sapropel).

The technical result is achieved by the fact that in the method, which involves applying fertilizer twice to a site contaminated with oil and oil products, loosening the soil and introducing an aqueous solution of oil-degrading bacteria, according to the invention, slits are cut in the vertical and horizontal directions and moles to a depth of 60-80 cm, which are filled with zoobacterial fertilizer obtained by soaking the unproductive part of plants (e.g. straw) in river or pond or lake water in a volume ratio AI 1: 130-150 for 4-5 days, repeated fertilizing is carried out after 5-7 days, the composition obtained by composting sapropel, manure and uncontaminated soil is used as fertilizer, the bacterial strain Rhodococcus sp.MFN is used as oil-decomposing bacteria grown on a nutrient medium in which hydrocarbons identified in the contaminated area are used as a carbon source, an aqueous solution of Rhodococcus sp.MFN bacteria is added 2-3 days after the composition is applied. After keeping for 2-2.5 months, plowing is carried out with the formation turning to a depth of 25-27 cm, leveling the surface with heavy harrows and sowing seeds of perennial grasses, moreover, an aqueous solution of oil-degrading bacteria Rhodococcus sp.MFN is obtained by culturing bacteria to a suspension concentration of 1 · 10 ⁷ cells / ml, 5 ml of the suspension are diluted in 3 liters of water and made at the rate of 1 liter of an aqueous solution per 1 m ² .

Soil in a contaminated area and unpolluted soil for composting belong to the same type of soil.

The ratio of components for composting sapropel, manure and unpolluted soil are 11: 13: 6-7: 1-2, respectively.

The humidity of the composted mass is maintained at 60% throughout the entire composting period by adding zoobacterial fertilizer.

The composition is applied at the rate of 45-55 t / ha.

Straw, for example, cereal crops contains 12-14% of water-soluble substances, the carbohydrate fractions of which are a complete source of nutrient substrate, an energy source for obtaining and growing zoobacterial plankton contained in water (river or pond or lake).

As a result of the insistence of straw, the number of nitrogen-fixing microorganisms increases significantly. The dominant microorganisms are Aguspirillum, Pseudomonas, Bacterium. The amount of nitrogen fixation for 5 days is 2 g of nitrogen per 1 kg of straw. With the growth of nitrogen-fixing microorganisms, their partial death occurs, which leads to an increase in the number of ammonification microorganisms mainly of the genera Bacillus, Bacterium, as well as protozoa, which are encysted in straw and pond water. The reproduction of aquatic protozoa and invertebrate hydrobionts against the background of an increase in the number of microorganisms occurs according to the laws of the trophic chain.

The predominant forms of protozoa are small flagellates from the class Mastigophora (10 ind./ml), as well as ciliates pp. Colpidium, Cyclidium, Chilodonella (10 ³ ind./ml). Against the background of the multiplication of microorganisms and protozoa, after 2-3 days of straw infusion, the number of multicellular invertebrate hydrobionts, the natural inhabitants of water sources, from which water for infusion is taken, comes from the classes Copepoda, Cladocera, Rotatoria in the amount of several dozen specimens in 1 ml. Invertebrates Rotatoria and Cladocera have a very high reproduction rate. In Cladocera, the average daily gain is 15-20% of the average daily biomass of all products, in Copepoda - 3-8%. In contrast to plant residues, the ratio of nitrogen and carbon of microorganisms and invertebrate hydrobionts is an order of magnitude higher than 1: 5-1: 10.

Passing through microorganisms, especially under aerobic conditions, phytotoxic substances of plant residues (straw) causes their detoxification.

The proposed strain of bacteria Rhodococcus sp.MFN isolated from oil pipeline "Friendship" obtained at the refinery in Kapotnya, Moscow region. The strain is deposited by the All-Russian collection of industrial microorganisms, collection number VKMN As-1558.

The culture grows on a mineral medium, using oil, oil products and individual oil hydrocarbons as a carbon source.

Optional aerobic grows in the temperature range from 4 ° C to 40 ° C (optimum 28 ° C), does not need additional growth factors.

The strain is not virulent, not toxic, not toxigenic (tested on white mice). The strain is resistant to heavy metal ions.

Uncontaminated soil is the most favorable natural environment for the normal development of microorganisms. The upper humus horizon is most densely populated by microbes: up to 10 billion bacteria per 1 g of soil.

Soil is considered uncontaminated if the hydrocarbon level is below 500 mg / kg according to AFNOR NFT 90114.

According to the invention, soil contaminated with oil and oil products and unpolluted soil for composting belong to the same type of soil. This is due to the following.

The intensity of self-cleaning of various types of soils is different, therefore, their attitude to the negative effect of oil and oil products is different. Hence the differences in threshold values, the excess of which leads to serious changes in physico-chemical microbiological properties.

The method is as follows.

On the area contaminated with oil and oil products, gaps are cut in the vertical and horizontal directions and molehills to a depth of 60-80 m. Gaps and molehills are filled with wet zoobacterial fertilizer.

Zoobacterial fertilizer is obtained by insisting crushed up to 80-100 mm waste of the unproductive part of plants, such as cereal straw, in river, pond or lake water in a ratio of 1: 130-150. Infusion is carried out for 4-5 days. 5-7 days after filling the cracks and molehills with zoobacterial fertilizer, a composition of 45-55 t / ha is applied to the contaminated area.

The composition is obtained by composting sapropel, manure and unpolluted soil.

Sapropel is frozen in settlers in the winter, frozen water is separated, mixed with the solid fraction of manure, humidity not less than 60% and unpolluted soil in the ratio 11-13: 6-7: 1-2.

The humidity of the composted mass is maintained at 60% over the entire composting period of 1.5-2 months by the addition of zoobacterial fertilizer. The mass is periodically mixed.

An aqueous solution of oil-degrading bacteria is prepared as follows.

The strain Rhodococcus sp.MFN is grown (cultivated) on mineral medium 8E of the following composition, g / l:

(NH ₄ ) ₂ HPO ₄ - 0.5; KN ₂ PO ₄ - 0.7; NaCl - 0.5; MgSO ₄ × 7H ₂ O - 0.8; distilled water  - 1 liter; pH - 7.2

As a carbon source, 1% (of the volume of medium) of hydrocarbons identified in the contaminated area is added.

Cultivate to a suspension concentration of 1 · 10 ⁷ cells / ml. For uniform application, a suspension of Rhodococcus sp.MFN is diluted in water at the rate of 5 ml of suspension in 3 l of water.

An aqueous solution of bacteria is applied to the contaminated area at the rate of 1 liter of an aqueous solution of bacteria per 1 m ² 2-3 days after the composition is applied.

After 2-2.5 months of aging, plowing is carried out with the formation turning to a depth of 25-27 cm, leveling the surface with heavy harrows and sowing seeds of perennial grasses.

Sowing seeds is carried out along with the dry residue of frozen water.

Example 1. Research was conducted in the Volgograd region at the pipeline passage for pumping oil. As a result of repair work to restore the integrity of the pipeline and prevent oil leakage, the soil is compacted to a depth of 70 cm. At the same time, the site is contaminated with oil and oil products. Moreover, the degree of contamination varies in depth of the plot and is 5003-7029 mg / 100 g of soil. The soil of the contaminated area is a type of dark chestnut soil.

The test for the presence of aerobic bacteria is negative (sterile soil).

On the studied area, cracks and molehills are cut to a depth of 80 cm and filled with liquid zoobacterial fertilizer.

Zoobacterial fertilizer is prepared as follows.

Straw, for example, cereal, crushed to a size of 80-100 mm, is soaked in river or pond or lake water in a ratio of 1: 130 for 5 days.

After 5 days, a composition is prepared on the test site, which is prepared as follows.

Sapropel is frozen in the winter period of time, frozen water is removed, mixed with a solid fraction of manure and unpolluted soil in a ratio of 13: 6: 1. Uncontaminated soil is a type of dark chestnut soil. Humidity of the composted mass of 60% is maintained during the entire composting period of 1.5-2 months by adding zoobacterial fertilizer.

2 days after the composition was applied to the contaminated area, an aqueous solution of bacteria Rhodococcus sp.MFN was added at a rate of 1 l / m ² .

As a result of the studies, it was found that:

- 4 weeks after the introduction of an aqueous solution of bacteria, the content of petroleum hydrocarbons decreased unevenly along the depth of the site and amounted to at a depth of:

0-20 cm 3655 mg / 100 g of soil (48% of oil hydrocarbons destroyed); 20-40 cm 4760 mg / 100 g of soil (22% destroyed); 40-60 cm 4423 mg / 100 g of soil (19% destroyed); 60-80 cm 4352 mg / 100 g of soil (13% destroyed).

- after 6 weeks:

0-20 cm 2038 mg / 100 g of soil (71% destroyed); 20-40 cm 2866 mg / 100 g of soil (54% destroyed); 40-60 cm 2914 mg / 100 g of soil (43% destroyed); 60-80 cm 3001 mg / 100 g of soil (40% destroyed).

- after 8 weeks:

0-20 cm 1405 mg / 100 g of soil (80% of hydrocarbons destroyed); 20-40 cm 1370 mg / 100 g of soil (78% of oil hydrocarbons destroyed); 40-60 cm 2045 mg / 100 g of soil (60% of oil hydrocarbons destroyed); 60-80 cm 2401 mg / 100 g of soil (52% of oil hydrocarbons destroyed).

- after 10 weeks:

0-20 cm 527 mg / 100 g of soil (92.5% of hydrocarbons destroyed); 20-40 cm 560 mg / 100 g of soil (91% of oil hydrocarbons destroyed); 40-60 cm 562 mg / 100 g of soil (89% of hydrocarbons destroyed); 60-80 cm 650 mg / 100 g of soil (87% of hydrocarbons destroyed).

Then, in the study area, plowing is carried out with the formation turning to a depth of 25-27 cm, leveling the surface with heavy harrows and sowing seedless rump.

Sowing seeds was carried out along with the dry residue of frozen water.

Seed germination rate was 84%.

The residual amount of hydrocarbons in the soil 5 months after sowing the grass was 479 mg / 100 g of soil over the entire depth, which, according to the AFNOR NFT 90114 standard, makes it possible to consider the studied area cleared of hydrocarbons.

Example 2. The conditions are the same.

Differences: a) cereal straw is soaked in river or pond. or lake water in a ratio of 1: 150 for 7 days;

b) the ratio of components for composting sapropel, manure and unpolluted soil is 11: 7: 2;

c) the composition is applied to the contaminated area after 7 days;

g) the introduction of an aqueous solution of bacteria Rhodococcus sp.MFN was carried out 3 days after application of the composition.

As a result of studies, it was found that the destruction of oil hydrocarbons took place more evenly, after 4 weeks from 20 to 46% of oil hydrocarbons were destroyed along the depth of the site:

- after 6 weeks - from 59 to 72% of oil hydrocarbons are destroyed;

- after 8 weeks - from 68 to 82%;

- after 10 weeks - from 90 to 93%.

Seed germination rate was 83%.

The residual amount of hydrocarbons in the soil 5 months after sowing the grass was 466 mg / 100 g of soil.

Example 3. The method is carried out similarly to examples 1 and 2. Differences in soil types, namely, the soil of the contaminated area refers to the type of dark chestnut soil, and unpolluted soil for composting refers to the type of light chestnut soil.

As a result of studies, it was found that the content of petroleum hydrocarbons more than doubled 2.5 months after the introduction of an aqueous solution of bacteria Rhodococcus sp.MFN, the content of petroleum hydrocarbons according to examples 1 and 2.

The seed germination of the beanless rump was 51%, and the hydrocarbon content in the soil 5 months after sowing was 698 mg / 100 g of soil - the soil is contaminated with petroleum hydrocarbons.

The ratio of waste from the unproductive part of plants and river or pond water 1: 130-150 to obtain zoobacterial fertilizer is optimal. With more water, the fertilizer is less concentrated, there is a decrease in the biomass of the association of microorganisms and invertebrate hydrobionts, which is introduced into the soil, with less water, putrefactive processes develop in the infusion.

The ratio of components for composting was obtained experimentally. The duration of all stages of biological soil remediation is optimal.

The advantage of the claimed method is that it allows not only to clean the soil from oil and oil products, but also to restore the soil fertility of the contaminated and over-compacted area. This is due to the fact that the composition of sapropel includes all the nutrients necessary for the growth and development of plants, so it can be attributed to the group of complex multifactorial fertilizers. The optimal biological ratio of nutrients, as well as a slightly soluble state, excludes “overfeeding” or “underfeeding” of plants. The assimilation of individual elements by the plant occurs as the humus of the sapropel is mineralized. More than half of the organic part of sapropel is represented by humic substances, due to which it is possible to solve the problem of soil fertility by creating a deficit-free balance of humus in the soil of lacustrine regions.

Information sources

1. US patent No. 3813316, CL 195-28, 1974.

2. SU 250849, class C12N 1/20, 1968.

3. SU 1076446, class C12N 15/00, 1984.

4. RU 2127310, cl. C12N 1/20, 1999 - prototype.

Claims (5)

1. The method of biological remediation of re-compacted soils contaminated with oil and oil products, which involves applying fertilizer twice to the contaminated area, loosening the soil and applying an aqueous solution of oil-degrading bacteria, characterized in that vertical and horizontal cracks are cut in the contaminated area and moles are 60- 80 cm, which is filled with zoobacterial fertilizer obtained by soaking the unproductive part of plants, such as straw in river or pond, or lake water in a volume ratio of 1: 130-150 for 4-5 days, repeated fertilizing is carried out after 5-7 days, as a fertilizer, use the composition obtained by composting sapropel, manure and uncontaminated soil, the bacterial strain Rhodococcus sp is used as oil-decomposing bacteria .MFN grown on a nutrient medium in which hydrocarbons identified in the contaminated area are used as a carbon source, an aqueous solution of Rhodococcus sp.MFN bacteria is added 2-3 days after the composition is applied, after being kept for 2-2.5 months, plowing is carried out with a turnover of the formation to a depth of 25-27 cm, leveling with heavy harrows and sowing seeds of perennial grasses, moreover, an aqueous solution of oil-degrading bacteria Rhodococcus sp.MFN is obtained by culturing bacteria to a suspension concentration of 1-10 ⁷ cells / ml , 5 ml of the suspension is diluted in 3 l of water and made at the rate of 1 l of an aqueous solution per 1 m ² . 2. The method according to claim 1, characterized in that the soil of the contaminated area and uncontaminated soil for composting belong to the same type of soil. 3. The method according to claim 1, characterized in that the ratio of the components for composting sapropel, manure and uncontaminated soil is 11-13: 6-7: 1-2, respectively. 4. The method according to claim 1, characterized in that the humidity of the composted mass is maintained at 60% during the entire period of composting by adding zoobacterial fertilizer. 5. The method according to claim 1, characterized in that the composition is applied at the rate of 45-55 t / ha.