CLEANING OF OIL-CONTAMINATED LANDS IN THE CLIMATIC CONDITIONS OF AZERBAIJAN

ABSTRACT

In this work, two biotechnological technologies were tested to restore contaminated soils using microorganisms. One technology with the activation of natural microflora and a technology that requires the introduction of oil-oxidizing microorganisms in the form of a biological product. When using biological methods of cleaning soil from oil pollution in combination with agrotechnical methods, the natural microflora of oil-polluted soils was activated. The introduction of a biological product under these conditions makes it possible to increase the intensity of soil cleaning from oil pollution as a result of the cleaning time in comparison with the natural microflora, it can be reduced by 3-4 months.

Keywords: oil contaminated soils, microorganisms, activity, biodegradation of oil pollution.

At this time, as a result of anthropogenic activity, there is a large-scale pollution of the environment with harmful substances. Oil and petroleum products are one of the main pollutants in the environment. Particular load is experienced by the soil, its morphological and physicochemical properties deteriorate, there is a suppression of self-cleansing ability, there are negative changes in the development and functional activity of the organism. The limitation of land resources puts an indefinite task of return in economic use of all disturbed and degraded soil.

To accelerate the process of self-purification of soils from oil, all natural reserves of the ecosystem, including biological ones, are used. Microbiological methods of soil cleaning can complement various technologies, and in certain situations, they have no analogues [1].

The need for civilized technologies for the destruction of the consequences of oil pollution of terrestrial ecosystems can hardly be overestimated. The use of physicochemical methods of remediation (combustion, excavation of soil layers with further storage, mechanical isolation, high-temperature extraction, washing, electric current treatment, solvent extraction, redox reactions) has reached its limits, and the methods of bioremediation of oil-contaminated lands are becoming increasingly important environmentally friendly and relatively inexpensive [2-5].

The existing methods of soil bioremediation are mainly aimed at eliminating a specific pollutant and are ineffective with simultaneous soil contamination with organic and inorganic pollutants [6]. In regions with a temperate and cold climate, methods of reclamation using functionally oriented technologies are relevant, providing for the effective stimulation of the oxidation of hydrocarbons by natural oil-oxidizing microorganisms. The optimal combination of agrotechnical measures makes it possible to reduce the level of pollution, as a rule, by 30–40%, mainly due to easily degradable oil components. In this case, high-molecular hydrocarbon components, as well as heavy metals, the content of which in oil can reach 1 g / kg [7], are not destroyed for a number of years. Heavy hydrocarbons firmly bind with soil particles, forming hydrophobic films, and soils become inaccessible to microorganisms. In order to increase the bioavailability of hydrocarbons, surfactants are used that promote desorption and solubilization of oil components. However, synthetic surfactants widely used in industry are environmentally hazardous substances with a high degree of toxicity, which are actively accumulated in soil biocenoses. In this regard, the use of bacterial surfactants with low toxicity and stable activity under extreme conditions is promising. In [8], an assessment was made of the possibility of using rhodococcus-biosurfactants for bioremediation of soils contaminated with hydrocarbons. It is shown that the introduction of rhodococcus-biosurfactants into the model soil leads to a decrease in the level of contamination with crude oil by 76%, a model mixture of hydrocarbons by 39%, and polyaromatic hydrocarbons (pahs) by 75%.

A biotechnology for the purification of oil-contaminated soils was developed at the Integrated Research Laboratory, which took into account the soil and climatic conditions of the region, characterized by an insignificant humus content, a low thickness of the humus horizon, high temperatures and a lack of moisture in the summer months. This technology allows cleaning of soils from oil and oil products at a concentration of petroleum hydrocarbons of no more than 12%, to a depth of 25-30 cm using the activation of natural microflora, as well as with the introduction of microorganisms into the soil as a biological product.

The technology used makes it possible to optimize the process of biodegradation of petroleum hydrocarbons by the method of introducing certain ameliorants into the soil, in combination with agrotechnical methods.

• Improvement of the air-gas regime, retention of moisture and prevention of leaching of cells of microorganisms from the soil, is ensured by the introduction of chopped straw, plowing, loosening by mixing the soil layer to the depth of its processing;
• Activation of microbiological processes, degradation of toxic components, the formation of soil, which was facilitated by organic and mineral fertilizers;
• The rate of decomposition of pollutants, the mobility of nutrients, the activation of biological processes of self-cleaning of soils, an effective effect is exerted by irrigation, by sprinkling.

Cleaning the oil-contaminated area using microorganisms included several stages:

1. Field or preparatory stage:

• inspection of the oil-contaminated area and elimination of pollution sources;
• dismantling and removal of the remaining concrete foundations and other remnants of communications, as well as household waste;
• elimination of accidental spills;
• planting work, including drainage and backfilling of soil into swamps formed after rains;
• creation of a drainage system, the size of the drainage channel is 05 × 10 m;
• installation of containers around the perimeter of the site to collect irrigation water.

2. Biotechnological stage:

• plowing, loosening, disking of the area (to a processing depth of 25-30cm);
• marking of stations for taking soil samples;
• taking averaged soil samples from a depth of 0-25cm;
• the introduction of ameliorants – straw, organic and mineral fertilizers, is carried out for surface treatment (plowing, loosening, disking), then the soil is moistened by sprinkling;
• application of organic fertilizers (cow or bird manure);
• application of mineral fertilizers Ammophos, Nitrofoska;
• introduction of chopped straw (5-10 cm);
• irrigation of the site by sprinkling.

Organic fertilizers and straw are thoroughly mixed and evenly distributed over the area to be cleaned. Mineral fertilizers are applied in the form of aqueous solutions during irrigation. The irrigation regime is determined by the external temperature.

When using a biological product for cleaning oil-contaminated soils, microorganisms are introduced into the soil during irrigation by sprinkling. The biotechnological stage provides for monitoring studies to control the cleaning process:

• the number of biodestructors;
• soil moisture;
• phytotoxicity of the soil.

Phyto-reclamation stage:

The phytomeliorative stage of bioremediation begins after most of the oil hydrocarbons, 30-40%, have been oxidized and destroyed by microorganisms, when the soil becomes practically non-toxic to plants.

To carry out biotechnological work to clean up oil-contaminated soils of the Apsheron Peninsula, an oil-polluted area was selected at the Ramana field, soil samples were taken with a size of 20 × 30 meters and analyzes were carried out to obtain initial data on the concentration of oil and the number of oil-oxidizing microorganisms.

The number of oil-oxidizing microorganisms in the selected area does not exceed 45 × 10, and the minimum is 25 × 10. The number of heterotrophic bacteria varies from 12 × 10 to 56 × 10. The concentration of oil is about 12%. Thus, these data indicate that the number of microorganisms in the study area is at a low level

At the same time, it is known that the effectiveness of soil cleaning using microorganisms is carried out when the number of microflora is at least a million or more. Further, to improve the quality of soil cleaning from pollution, clean soil was brought to this area and ameliorants were introduced: – finely chopped (5-10 cm) straw, at the rate of 15 kg / m2; organic fertilizer (cow dung, chicken droppings), at the rate of 25 kg / m2 in combination with the use of agricultural techniques (plowing, loosening). After that, microbiological and chemical analyzes were again carried out.

As a result of these measures, the oil content was also improved by about 2%.

Conclusion

In this work, as a result of the research carried out for the purification of oil-contaminated soils, a biological product was used for the first time, consisting of active strains of microorganisms with the addition of ameliorants, consisting of sawdust, mineral fertilizers. The introduction of a biological product into the soil together with ameliorants made it possible to maintain a high level of biodegradation of petroleum hydrocarbons in the upper soil layers at all stages of the work being carried out.

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