RU2301258C2 - Method of cleaning oil polluted lands - Google Patents

Abstract

FIELD: oil pollution elimination and biotechnological methods.

SUBSTANCE: removal of petroleum products from land is accomplished by introducing therein molasses until final saccharide concentration 3-10 g/kg and surfactant within concentration range 10 to 40 mg/kg land. Additionally potassium and/or nitrogen and/or phosphorus in amount 0.112 g/kg are added. Thereafter, temperature and water conditions are maintained in land to assure living functions of microorganisms over a period no less than 2 months until residual content of hydrocarbon fraction 30-40% is attained.

EFFECT: achieved more effective freshly polluted land cleaning and shortened cleaning time.

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Description

The invention relates to the protection of the environment and can be used to clean the soil or soil from oil pollution in all industries related to the processing, transportation or storage of oil and oil products, as well as in the aftermath of accidents or disasters. This method is effective for cleaning from fresh oil contaminants, i.e. being in the environment for no more than 12 months, with a concentration of oil products of 10-75 g / kg of soil and in the presence of a pool of hydrocarbon-oxidizing microorganisms in it.

Currently, in situ technology for the remediation of oil-contaminated soils, the use of in situ biostimulation is more preferable for a number of reasons, including, primarily, economic. In some cases, for example, at large scales of pollution, they are the only possible ones. An important stage in this is the selection of techniques for intensifying the functional activity of natural microbial cenoses and especially the group of hydrocarbon-oxidizing microorganisms (UOM).

A known method of bioelectric cleaning of the soil from organic contaminants, which consists in introducing into the cleaning zone a solution of oil-oxidizing microorganisms and placing electrodes - anode and cathode. A constant electric current is passed through the electrodes and a solution is collected that accumulates at the cathode, with its repeated introduction into the cleaning zone. A constant electric current is periodically turned on and off and the soil temperature near the surface of the anode is maintained within 10-40 ° C. In this case, the soil is pre-heated to a temperature in the range of 10-20 ° C. Air is periodically supplied to the cleaning zone, and vapors of oil and oil products are pumped out (RF Patent for the invention of the Russian Federation No. 2177379, IPC: B09C 1/00, B09C 1/10).

This method is aimed at providing optimal conditions for the life of microorganisms temperature conditions and pH values of the soil. However, the disadvantage of this method is the complexity of the cleaning process during accidental spills in environmental objects, remote from communications and a current source. In addition, the cleaning process is associated with high energy consumption.

A known method of purification of soils, soil, fresh and mineralized water from oil and oil products, based on the introduction of the biological product "Roder", prepared on the basis of R-dissociants of strains Rhodococcus ruber BKM Ac-1513D and Rhodococcus erythropolis BKM Ac-1514D, grown on medium with high sea salt content. Selected microorganisms that are part of the preparation are able to multiply and degrade oil hydrocarbons in a wide range of salinity (0.05-10%) and temperatures (8-35 ° C) (Patent for the invention of the Russian Federation No. 2174496, IPC: 7 C02F 3/34 , B09C 1/10, C12N 1/26, C12N 1/26).

The disadvantage of this method is the narrow range of microorganisms used and low competitiveness with respect to indigenous microorganisms due to the low growth rates of this group of bacteria. In addition, the use of a biological product is a more expensive way compared to stimulation.

A known method of cleaning the surface of water and soil from oil and oil products using a sorbent, which is used is converted into a neutral mixture when composting with bird droppings, hydrolysis lignin, enriched with oil-degrading microorganisms, dried to air-dry state and crushed, which is applied to the contaminated oil surface in the ratio by weight of the sorbent: oil 1: (3-5) at an ambient temperature of at least 5 ° C. With an oil film thickness on the water surface exceeding 1 mm, the sorbed oil is collected and taken to landfills for its decomposition on the ground, with less pollution, the sorbent is left on the surface for decomposition in place (Patent for the invention of the Russian Federation No. 2106309, IPC: C02F 1/28, C02F 3/34, EBB 15/04, C12N 1/26).

However, using this technology, pollution is not eliminated, but is transferred to another form and requires further processing.

All these methods are based on the introduction of foreign microorganisms - destructors into the contaminated object. These technologies are expensive due to the additional costs of building, storage and pre-treatment of microorganisms before entering the soil.

A number of publications are known concerning the development of methods for stimulating natural biodegradation by improving aeration of contaminated soil, water regime, the ratio of nutrient components: carbon, nitrogen and phosphorus, the introduction of emulsifiers, organic materials, etc.

The Osmocote fertilizer with slow release of nutrients (nitrogen, phosphorus and potassium) and Inipol EAP-2 containing organic nitrogen and phosphorus is known to have a significant positive effect on the activity of microorganisms and the loss of aliphatic hydrocarbons in the soil of the coastal sea zone (Ran Xu, JP Obbard, Effect of nutrient amendment of indigenous hydrocarbon degradation in oil-contaminated beach sediments // Journal of Environmental Quality. - 2004. - V.32. - P.1234-1243).

However, the use of the above fertilizers for cleaning soils from oil pollution on an industrial scale is expensive. In addition, this technology is not effective enough, because only aliphatic oil compounds are significantly reduced, unlike other fractions that pose the greatest danger to the environment.

It is known to use chemically pure D-glucose at a concentration of up to 1 mg / g of soil to stimulate the development of a population of hydrocarbon-oxidizing bacteria in soil contaminated with diesel fuel, which accelerated its decomposition three times (Guzev VS, Halimov E.M., Volde M.I. , Kulichevskaya I. S. Regulatory effect of glucose on the activity of hydrocarbon-oxidizing microorganisms in the soil / UMicrobiology. 1997. - T.66, No. 2. - S.154-159).

However, the use of clean reagents for cleaning real objects is impractical because of their high cost.

A known method of cleaning soils from oil pollution using activated sludge biochemical plant to restore their biological activity. Three months later, there was a positive effect on the biological activity of the soil, the oil content at an initial concentration of 6% decreased by about three times (Kireyeva N.A. Biodegradation of oil in the soil by cultures of hydrocarbon-oxidizing microorganisms // Biotechnology. - 1996. - No. 1. - P. 51-54).

However, activated sludge remains active for a very short time, which makes it difficult to use it at real sites remote from the treatment facilities of enterprises whose activated sludge is adapted to the corresponding pollutants.

It is known to use biologically produced surface-active substances (bio-surfactants) that are environmentally friendly for cleaning soils from oil pollution (Oberbremer A., Muller-Hurtig R, Wagner F. Effect of the addition of microbial surfactant on hydrocarbon degradation in a soil population in a acquired reactor // Applied Microbiology and Biotechnology. - 1990. - 32. P.485-489).

However, bio-surfactant production is expensive, which limits their use for bioremediation of contaminated sites.

Closest to the claimed is a method for cleaning dumps of waste bleaching soil contaminated with oil products, which can also be used in soil remediation (Loginov O.N., Boyko T.F., Kostyuchenko V.P., Komarov S.I., Podsepikhin A. K., Galimzyanova NF About biological cleaning of technological dumps from oil products // Soil Science. - 2002. - No. 4. S.481-486). It is based on the introduction of biotrin - a feed additive containing proteins, micro and macro elements, amino acids and vitamins - and molasses - waste production of sugar containing up to 40% sugars to a concentration of 1 g / kg of soil for sugars. In addition, to accelerate degradation, highly oxidized inorganic substances were introduced: superphosphate, potassium nitrate, iron sulfate, and hydrogen peroxide. To improve the characteristics, the cultivated soil was diluted with fertile soil or activated sludge in a ratio of 1: 1. When making molasses in a laboratory experiment, the loss of petroleum products per month was 20%. In a full-scale treatment, the contaminated soil was mixed with fertile soil and activated sludge, a mixture of molasses, biotrin and superphosphate was introduced for stimulation, which allowed to reduce the content of residual oil products from 29 to 11%.

However, this method involves the introduction of a large volume of soil or activated sludge, which with large volumes may be unacceptable, in addition, a large volume of fertile soil is contaminated and cannot be used, the area required for soil cultivation increases significantly.

In addition, no determination was made of the change in the content of the most biodegradable and toxic fractions: aromatic compounds and resins, possibly as a result of such treatment they accumulate in purified soil. A positive result is largely determined by the introduction of a large number of oil-oxidizing microorganisms with activated sludge.

The objective of the invention is to simplify the method and reduce the cost of bioremediation, accelerate the cleaning of soils and soils with fresh oil pollution while improving quality by stimulating the UOM population by introducing molasses - an additional readily available carbon source and biologically active substances and surfactant - emulsifier of hydrophobic substrate.

The problem is solved in that in the method of cleaning the soil, which consists in introducing into the soil a nutritional supplement, including molasses, stimulating the growth of oil-oxidizing microorganisms contained in the soil, according to the proposed solution, the additive additionally contains surfactants in a concentration range of 10-40 mg / kg of soil, and Molasses is added to a final sugar concentration of 3-10 g / kg of soil.

Moreover, the additive additionally contains potassium, and / or nitrogen, and / or phosphorus, taken in quantities of 0.112 g / kg of soil.

In addition, after the addition of the additive, the temperature and water conditions of the soil are maintained to ensure the vital function of microorganisms for at least 2 months to a residual hydrocarbon fraction of 30-40%.

The invention is illustrated by drawings, in which Fig. 1 shows the dynamics of the abundance of UOM in soil with oil pollution for the selected options, Fig. 2 shows the results of stimulation of oil destruction, Fig. 3 graphically shows the rate of oil destruction in the experimental and control versions.

The invention is directed to the selection of optimal additives that stimulate an increase in the number and activity of hydrocarbon-oxidizing microorganisms in soils that have fresh contamination with oil products at a concentration of 10-75 g / kg.

The method is based on the introduction into the soil of an additive based on molasses, stimulating the development of oil-oxidizing microorganisms present in contaminated soil (soil). Molasses is a waste of sugar production, it usually contains 20-25% water, 58-60% carbohydrates (46-50% sucrose, as well as raffinose, galactose, arabinose, etc.), about 9% nitrogen compounds (betaine , amino acids, amides, ammonium salts), as well as growth substances (vitamins B ₃ , B ₈ and H) and trace elements. The introduction of additives in conjunction with the use of certain modes - temperature, humidity, processing time, accelerates the process of cleaning the soil with fresh contamination with oil products while maintaining efficiency and reducing costs. The method can be used both for processing contaminated soils and soils in situ (in situ), and in specially equipped sites on which the extracted soil is placed (ex situ).

To implement the method, the soil is moistened to a total moisture content of 15-17%, for example, tap water through a stationary water supply system or from a nearby freshwater source using a submersible pump or a vacuum barrel. With a small area of the cultivated area, watering can be done manually from a watering can. When watering, natural rainfall is taken into account. The introduction of molasses is carried out using a submersible pump or manually, if necessary, it is diluted with water. The amount of molasses introduced depends on the sugar content in it, to a final sugar content in the soil of 3-10 g / kg. When diluting twice molasses with a sugar content of about 50%, this will be 18-60 l / m of soil or 2-6 l / m of soil, respectively, when oil penetrates to a depth of 10 cm. Surfactants are pre-dissolved in water, application is made by pump through a hose or manually from a watering can. When dissolved in a ratio of 1: 100, the application rate is 1.5-6 l / m ^{3 of} soil or 0.15-0.6 l / m ² , which corresponds to 10-40 mg / kg. Mineral fertilizer is applied dry, when using an azofoska, the application rate is 1 kg / m ³ or 100 g / m ² with a contaminant penetration depth of 10 cm. After making the additives, the soil is mixed by disking, harrowing, plowing or using an excavator, depending on the depth of penetration of the pollutant and the state of the soil. Humidity at the level of 12-17% is maintained by irrigation; regular loosening (1 time in 10 days) is carried out to maintain optimal aeration. The process is recommended to be carried out at a temperature of 19-32 ° C.

A mixed soil sample (southern chernozem) taken in the Saratov Region was artificially contaminated with crude oil at a concentration of 50 g / kg. The soil was placed in plastic containers in an amount of 1.5 kg. The cleaning process was carried out at room temperature 19-24 ° C, with the introduction of various stimulants and periodic loosening and moisturizing. Microbiological analysis of the original soil showed that the content of hydrocarbon-oxidizing microorganisms in it was 6.5 × 10 ⁵ cells / g of soil, which indicated the presence of objects for stimulation.

To stimulate the development of UOM, the most accessible and cost-effective additives for industrial use were used: azofosku mineral fertilizer, which is a source of nitrogen and phosphorus, molasses as an additional readily available source of carbon and biologically active substances, and surfactants as an emulsifier. The components were added individually and in various combinations (Table 1).

Table 1.
Remediation options for contaminated soil Options Additives, g / kg of soil one control - no additives 2 azofoska - 0.7 3 molasses - 10 four Surfactant - 0.02 5 azofoska - 0.7; molasses - 10 6 azofoska - 0.7; Surfactant - 0.02 7 molasses - 10; Surfactant - 0.02 8 azofoska - 0.7; molasses -10; Surfactant - 0.02

According to the degree of impact on the microbial community, additives containing molasses, as in the form of a single component and especially in combination with others, had a powerful positive effect on the number of microbial populations, the second, containing only mineral fertilizer and surfactant in different ways, did not show a pronounced stimulating effect, and in some cases, the microbial community was somewhat depressed.

In the variants with the introduction of molasses of the maximum number, the UOM population (about 10 ⁸ ) reached on the 14-30th day of the experiment, and in option 8 it amounted to 4.5 × 10 ⁸ colony forming units (CFU) / g of soil (see figure 1). In the control variant (1) (using only agrotechnical techniques), the number of UOM increased to a maximum of about 20 times from the original, while in option 8 - almost 700 times. This allowed us to conclude that the stimulation of the development of oil-oxidizing microorganisms to a greater extent is caused by the introduction of molasses in combination with surfactants and mineral fertilizers. After 2 months, the number of UOM decreased.

Figure 1 shows the dynamics of the number of UOM in soil with oil pollution in the options: 1 - agricultural; 5 - agricultural technology, fertilizer and molasses; 8 - agricultural technology, molasses, fertilizer and surfactants.

When analyzing the loss of oil products in the soil being cleaned (see Fig. 2), the best results were obtained in options 7 (adding molasses and surfactants) and 8 (a full range of additives), the degradation of the pollutant for 1 and 3 months was 25.7 and 45%, and 24.4 and 45.8%, respectively.

Figure 2 shows the results of stimulation of the destruction of oil (at an initial concentration of 50 g / kg) in the soil in the following embodiments: 1 - agricultural technology; 7 - agricultural technology, molasses, surfactants; 8 - agricultural technology, molasses, surfactants and fertilizers, the residual oil content is given in absolute values.

It should be emphasized that in option 4 the degree of destruction did not differ from the control and the effect achieved with the simultaneous use of molasses and surfactants is a consequence of their combined effect. Molasses contributes to the rapid recovery and increase in the number of microorganisms after pollution, and surfactants, increasing the availability of petroleum products, providing them with a growth substrate.

When assessing changes in the rate of oil destruction, it was found that the maximum decrease was observed during the first month. In option 8, it reached 0.86% per day of the total content (see figure 3). In the control version, this value was equal to 0.55% per day. During the second month, the degradation rate decreased in variant 8 to 0.47, and in the control - to 0.27% per day, during the third month it was 0.18 and 0.14% per day in 8 and control variants, respectively. After six months a day, only 0.07 in the experimental and 0.08% in the control variant were destroyed. The data obtained show that the destruction processes are slowed down after 2-3 months of treatment, which indicates the feasibility of completing the stimulation of UOM by this method. Figure 3 shows the rate of destruction of oil in the experimental version 8 and the control version 1.

An analysis of the content of individual fractions in the residual oil products after three months showed that when molasses was added, the content of mono- and bicyclic aromatic and paraffin-naphthenic compounds decreased to a greater extent - from 62 to 67%. The destruction of PAHs was from 27 to 31%, alcohol-benzene resins - from 12 to 27%.

Based on the studies, it was found that to stimulate the development and activity of UOM in soil with fresh oil pollution, the introduction of molasses and surfactants is optimal, as well as in combination with mineral fertilizers. Molasses provides a quick recovery and a further increase in the number of UOM, while surfactants provide the bioavailability of a hydrophobic contaminant, especially its heavy fractions, due to its emulsification and desorption.

The maximum rate of degradation of oil products was observed during the first two months, and then it decreased. After the destruction of 60-70% of the hydrocarbon fraction, the residual oil products were slowly eliminated, on the basis of which it can be concluded that, upon reaching this level, active processing can be stopped. With an optimal combination of techniques, the degree of destruction can exceed the control values by 15-30%. The data obtained indicate the prospects of using this method.

Example 1

Soil was cleaned with fresh oil pollution at a concentration of 38 g / kg at a landfill for reclamation at a temperature of 15-23 ° C. Ridges 1 and 2 meters wide were formed from the soil. When cleaning used the following complex of stimulating additives: molasses, azofoska; Surfactant. Molasses with an initial sugar content of 45% was diluted in half and introduced using a submersible pump at the rate of 20 l / m ^{3 of} soil, which amounted to 3 g / kg of soil. Azofoska was applied in dry form manually at the rate of 1 kg / m ^{3 of} soil, which was about 0.7 g / kg of soil. Surfactants (neonol AF9-12) were dissolved in water (1: 100) and introduced manually at the rate of 1.5 l per m ^{3 of} soil, which was approximately 0.01 g / kg of soil. After adding additives, the soil was watered at the rate of 20 l / m ³ from a stationary water supply and mixed with an excavator. Regular cultivation and irrigation was performed to maintain the moisture content of the treated soil 12-17%. After 3 months of the experiment, the decrease in oil was 46%, in the control variant without additives, the decrease was 32%.

Example 2

For in situ cleaning of soil with fresh oil pollution at a concentration of 72 g / kg and a penetration depth of about 20 cm, molasses at a concentration of 10 g / kg and a surfactant mixture were used. Molasses with an initial sugar content of 50% was dissolved in water in a ratio of 1: 1, surfactants were added here to a concentration of 1 g / l and introduced using a submersible pump at a rate of 12 l / m ² , which was 10 g / kg molasses and 40 mg / kg surfactant. After adding additives, the soil was watered at the rate of 15 l / m using a vacuum barrel and mixed using a disk harrow. Cleaning took place at a temperature of 21-30 ° C, periodic loosening and maintaining humidity at the level of 12-17%. After 3 months, the active treatment was completed, the loss of oil was 49%. In the next two months, if necessary, only watering was carried out, with a repeated analysis carried out 5 months after the start of remediation, the destruction of the pollutant was 63%. Fractional analysis of residual oil products showed that along with fractions of paraffins, naphthenes and mono- and bicyclic aromatics, PAHs were effectively destroyed, their decrease was 47%.

Example 3

When in situ cleaning of soil with fresh fuel oil pollution at a concentration of 53 g / kg and a penetration depth of 10-15 cm, a complex of additives was used: molasses, surfactant, azofoska. Molasses with an initial sugar content of 50% was diluted in half and introduced using a submersible pump at the rate of 8 l / m ² , which amounted to 10 g / kg of soil. Azofoska was applied in dry form manually at the rate of 140 g / m ² , which was about 0.7 g / kg of soil. A surfactant (syntanol DS-10) was dissolved in water (1: 200) and applied manually at the rate of 0.4 l / m ^{2 of} soil, which was approximately 0.01 g / kg of soil. After making additives, the soil was watered at the rate of 20 l / m ² using a vacuum barrel and mixed using a disk harrow. The process took place at a temperature of 21-29 ° C, periodic loosening and maintaining humidity at the level of 12-17%. After 3 months, the decline in oil products amounted to 47%.

Example 4

When cleaning the soil with fresh fuel oil contamination at a concentration of 46 g / kg under laboratory conditions at a temperature of 21-23 ° C, the following methods were used:

1) agrotechnical processing (loosening and watering);

2) the introduction of molasses to a final sugar concentration of 10 g / kg along with agrotechnical processing;

3) the introduction of molasses to a final sugar concentration of 10 g / kg and a surfactant solution to a final concentration of 0.5 g / kg along with agrotechnical processing.

The experiments showed that option 3 was characterized by an increased duration of up to 3 months of a period of increased numbers of hydrocarbon-oxidizing microorganisms and the rate of destruction of fuel oil. Over six months of treatment, the destruction amounted to 29.3, 45.0 and 58.9% in options 1, 2 and 3, respectively.

During the implementation of the claimed processing method, it was possible for a long time to maintain an increased number of UOM, which contributes to a more rapid elimination of residual oil products after the completion of the active processing phase, and “biologically hard” fractions are largely destroyed. This is due to the optimal selection of concentrations of stimulating additives, the proposed amount of molasses application ensures the active functioning of the whole complex of soil microorganisms, including soil fungi, which are also active hydrocarbon destructors, at the recommended moisture level, the concentration of surfactants introduced in soil moisture approaches 0.5 KKM ( critical micelle concentration), which provides effective emulsification and desorption of a hydrophobic contaminant without toxic effect on soil biocenosis.

The inventive method makes it possible to process large quantities of contaminated soil, while the volume of contaminated material and the treatment area do not increase, fertile soil is not withdrawn from circulation, the technology is carried out without the use of foreign microorganisms that can upset the balance of the natural microbial community.

Claims (3)

1. The method of cleaning the soil from oil pollution, which consists in introducing into the soil a nutritional supplement, including molasses, stimulating the growth of oil-oxidizing microorganisms contained in the soil, characterized in that the additive additionally contains surfactants in a concentration range of 10-40 mg / kg of soil, and molasses is introduced to a final sugar concentration of 3-10 g / kg of soil. 2. The method according to claim 1, characterized in that the additive further comprises potassium, and / or nitrogen, and / or phosphorus, taken in quantities of 0.112 g / kg of soil. 3. The method according to claim 1, characterized in that after the addition of the additive, the temperature and water conditions of the soil are maintained to ensure the vital function of microorganisms for at least 2 months until the residual content of the hydrocarbon fraction is 30-40%.

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