RU2128703C1 - Method of removing petroleum and petroleum products from soil - Google Patents

Abstract

FIELD: oil pollution removal. SUBSTANCE: method consists in treating soil with culture fluid containing microorganisms. Preliminarily, microorganisms utilizing spelt oil are isolated from soil taken from polluted area and cultured in culture fluid until maximum cell concentration is reached. Area is then treated with biomass in proportion corresponding to concentration of microorganisms taken off and in amount sufficient to completely destroy spelt oil. EFFECT: accelerated oil destruction. 3 tbl, 2 ex

Description

 The invention relates to the protection of the environment, namely to the protection and rational use of soil.

 The annual pollution of the environment by oil and oil products leads to enormous environmental and economic damage.

 The natural restoration of contaminated lands and surfaces requires decades, this process is especially complicated in areas with cold climatic conditions, in which the restoration of contaminated soils without outside intervention is almost impossible.

 There are various methods for the restoration of oil-contaminated lands: plowing, burning, backfilling of contaminated sites with soil and removal of contaminated soils.

 However, the above methods do not always contribute to soil restoration, and often themselves cause long-term environmental damage.

 Various chemical methods for removing oil are known.

 So known is a method of removing hydrophobic aromatic impurities from the soil, which consists in treating the contaminated material with organic solvents taken in an amount of 20-90% by weight of the material, to which polystyrene foam particles are then added in a ratio of 1: 1 to 1: 100. The result is a redistribution of impurities between the material and polystyrene foam, which, together with the part of the impurities that transferred to the particles, is separated from the purified material (US Pat. No. 5,242,598).

 This process is very expensive and time-consuming, and therefore not practical application.

 To remove oil stains from the surface of seawater, a dispersant composition is used that contains a surfactant, a solvent and a monoalkylguanidinium salt (US Pat. No. 4,623,468). The method is not suitable for soil treatment, because promotes secondary pollution of the processed surface.

 One of the most promising methods for controlling oil spills is the microbiological and biochemical methods of purification.

 It is known to use for purification of industrial waters contaminated with oil of the bacterial strain Flavebacteril tirenicum VKPM B-3369, which works well under aeration conditions (av. St. 1409594).

 The closest way to clean the soil from oil and oil products is a method that includes treating the soil with a solution containing the bacterial strain Rhodococus erythropolis VKM Ac-1339D (St. St. 1805097, C 02F 3/34, 1993).

 In all known microbiological methods for cleaning the surface of oil and oil products, the form of application of the strain is a lyophilized culture or a culture dried using a spray dryer, which leads to a sharp loss of activity of the drug. The use of energy-intensive processes (separation and drying) leads to an increase in the cost of the cleaning process.

 When applying strains utilizing oil, in different regions, the adaptation of the strain used to specific sources of pollution was not always observed.

 The authors found that when introducing strain associations into contaminated soil, which is capable of destroying oil and oil products, but which is not peculiar to the ecological community of a particular soil, the wild local microflora creates serious competition for it, which leads to a slowdown in the vital processes of the introduced association, up to her death, i.e. crowding out by a local stronger community, adapted to these sources of substrates and geochemical conditions.

 To effectively clean the soil from oil and oil products, a cleaning method is proposed, which includes treating the soil with a culture fluid containing microorganisms. In this case, microorganisms utilizing the spilled oil and oil products are preliminarily isolated from the soil contaminated from the soil, then the selected microorganisms are separately produced in the fermenters until the maximum concentration of cells in the culture fluid is reached and the biomass is mixed in the ratio corresponding to the ratio of isolates in the sample taken from the pollution site, after which they treat the soil in an amount sufficient to completely destroy oil and oil products.

 The use of local microorganisms isolated from pollution sites in each specific region made it possible to more efficiently and more deeply utilize various complex substrates not accessible to monocultures.

 The treatment of contaminated sites with a culture fluid containing microorganisms characteristic of the locality made it possible to achieve a high rate of decomposition of oil and oil products due to the high activity of microorganisms obtained during production without using the isolation and drying stage.

The proposed cleaning method is also suitable in Siberia and the northern regions, because local microorganisms reproduce at low temperatures (5-10 ^o C).

 Examples of the implementation of the proposed cleaning method.

 Example 1. Isolation of microorganisms-destructors of oil pollution.

 Soil samples for the experiment were taken at the boreholes of the Sosnovskoye, Talinskoye fields, the Van Yegan field and the Ufa oil refinery.

The selection of crops was carried out in the following way:
- by plating 3 initial samples on meat-peptone agar with 0.5 oil (MPA with H) according to the Drigalsky method / A.S. Labinskaya. Microbiology with the technique of microbiological research. M., 1972, p. 66 / followed by seeding the obtained monocultures onto Raymond’s liquid medium with oil, followed by transfer to Petri dishes with (MPA with H) according to the Drigalski method.

According to this method of isolation, 20 ml of nutrient medium was poured into Petri dishes. The medium was kept in a thermostat at 37 ^o C for 24 hours to check for the presence of extraneous microflora. Then, a series of dilutions of the initial samples in physiological saline was prepared and cultures were diluted from dilutions 10 ^-3 and 10 ^-4 into sterile-tested plates, 0.1 ml of the suspension was pipetted into Petri dishes and ground with a spatula near the burner flame. The cups were turned over and placed in a thermostat, where they were incubated at a temperature of 30 ^o C for 72 hours. After that, morphological and microscopic analysis of the obtained microorganism colonies was carried out, and their ratios were determined. On average, 30 colonies of various morphological types were obtained on Petri dishes. Next, the colonies were sieved using a bacteriological loop on a solid nutrient medium, beveled into a test tube to obtain a monoculture.

 The isolated microorganisms of biodestructors were plated on Raymond's liquid medium with oil in order to select the most active clones and the biodegradable activity of the isolated monocultures was determined.

For this, a number of dilutions (10 ^-1 - 10 ^-4 ) of the initial samples on Raymond's liquid medium were prepared. After oil addition, the obtained variants were incubated for 5 days at room temperature. Biodegradable activity was determined according to a conventionally accepted five-point scale. Score 5 points - a highly emulsified layer of oil, with shaking a homogeneous emulsion of oil in water; grades from 4 to 2 points - various degrees of emulsification of oil in water with colloidal particles of oil of different sizes; score 1 point - oil decomposition is practically absent.

Thus, as a result of the work carried out, it was highlighted:
- from the soil of the Sosnovsky deposit 12 active isolates of bacteria with biodegradable activity in relation to oil,
- from the soil of the Talinsky field - 7,
- from the soil of the Van Egan field - 10,
- from the soil of the Ufa oil refinery -12.

 So, for example, isolates that utilize oil and oil products were isolated in the Sosnovskoye field, the qualitative and quantitative composition of which is shown in Table 1 with the points for the selected five-point system.

 Example 2. The cultivation of selected microorganisms.

The cultured isolates were cultured in a laboratory fermenter using Raymond culture medium. After reaching the necessary cultivation conditions: the composition of the nutrient medium, temperature (25-28 ^o C), pH values (6.5-7.5), the fermenter was seeded with a selected microorganism culture. In the fermenter, process parameters were maintained.

 After separate cultivation of the isolated monocultures and reaching the maximum concentration of cells in the culture fluid, the latter is removed from the fermenter. The produced microorganisms are mixed in the ratio corresponding to the ratio of isolates in the sample taken from the pollution site (for the example of the Sosnovsky field, see Table 1 at the end of the description). After that, the prepared composition is treated with the contaminated surface in an amount sufficient for complete destruction of the oil.

 The maximum concentration of cells grown in Raymond medium with oil and without oil in the culture fluid is shown in table. 2.

 Similarly, the results of the growth of selected microorganisms for the remaining pollution sites were obtained.

 The results of soil cultivation by the obtained associations (examples 2, 3) and the most active one strain from the selected association (examples 4, 5) are given in table. 3.

Claims (1)

 A method of purifying the soil from oil and oil products, comprising treating the soil with a solution containing microorganisms, characterized in that the microorganisms utilizing spilled oil and oil products are previously isolated from the soil contamination, then the selected microorganisms are separately produced in fermenters to achieve the maximum concentration of cells in the culture liquids and mix biomass in the ratio corresponding to the ratio of isolates in the sample taken from the place of contamination, and then process its soil in an amount sufficient for the complete destruction of oil and oil products.

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