Microbiological researches of the petro polluted soil and methods of restoration

More than 208 oil fields have been discovered in Kazakhstan, while oil and oil products are one of the most dangerous and large-scale environmental pollutants [1,2]. Therefore, the ecological problem of rebuilding a biosystem, contaminated with oil and oil products is an extremely urgent task. Soil belongs to the most important natural resource, the state of which determines the ecological balance of the planet. The main characteristic of the soil is fertility, which is formed, due to the vital activity of microorganisms. Economic human activity leads to soil pollution reducing potential fertility. Soil pollution with oil and petroleum products is currently an urgent problem. The extraction of oil from the bowels, cleaning and transportation are not only technically complex, but also dangerous processes. Inevitably, each stage of production operations is accompanied by oil leakage, which can cause irreparable phenomena. Chronic oil spills are a serious threat to the environment and human health.

When eliminating pollution only mechanical and physicochemical methods do not always achieve the desired effect, since often there are problems of recycling of waste generated after treatment. The most promising are biological methods of cleaning oil-contaminated objects, as they do not cause additional damage to the environment and they are the cheapest. A great deal of preference is given to bacterial

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preparations, since they are more viable and competitive in the environment. On the basis of active strains of microorganisms-oil depleters, biopreparations are being developed with different degrees of effectiveness [3 -5].

Methods of introducing cultures of microorganisms are used in cases when the necessary aboriginal microflora is absent or very weak. They can be used for massive and accidental pollution, in difficult conditions, in the absence of a developed natural biocenosis. The advantage of these methods is their selectivity and the ability to remove and destroy complex toxic compounds.

Biological purification is most often used to remove organic contaminants in petro polluted soil. Biological purification methods can be divided into: 1) methods of microbio-degradation of pollutants; 2) methods of bioabsorption and redistribution of pollutants. Methods are based on the ability of various organisms, especially plants, to absorb all kinds of toxic components from soils, accumulate them in their tissues and thereby purify the soil. For example, sowing on oil-polluted soil of beans and grasses promotes acceleration of biodegradation of oil. For this purpose, sorghum, arable pea, alfalfa, sweet clover, vetch, barley, oats can also be grown.

Methods of microbio degradation are based on the destruction of pollutants by various types of microorganisms. The effect is achieved due to the activation of native microflora or the introduction of certain microorganisms into the soil, as well as various complex preparations. As a result, microorganisms begin to actively absorb the pollutant and cause its destruction. Activation of biodegradation in oil- contaminated soils and groundwaters is achieved by the introduction of mineral fertilizers.

Soils in the city of Shymkent differ in terms of anthropogenic impact. Microbial communities in the investigated soils react to environmental influences and accordingly all stations demonstrate different quantitative and qualitative indices.

The soil moisture content, the water content, and also the content of CFU (colonies forming units) of urban soil have a special effect on the microbiological community of soils:

Station No. 1 - the territory of the Sayram District (within the city of Shymkent);

Station No. 2 - the territory of the SKSU M. Auezov;

Station number 3 - oil-polluted territory of railway station;

Station number 4 - the territory of the coast of the river Koshkarata;

The results of the experiments conducted during the spring-summer period show that the water content decreases, which directly reduces the amount of soil microorganisms. And if the maximum amount was in the first period of spring (March-April) is fairly stable 6,4x10⁸ -7,5x10¹⁰, then from May to August, there is a sharp decrease in both moisture in the studied soils and a significant decrease in soil microorganisms.

It has been established that the bacterial community of the soil of stationary stations within the city of Shymkent is not characterized by constancy and stability, the microbiocenosis is sensitive to changes in the environment.

It is shown that the number of microorganisms in the soil reaches its maximum in the spring, which is due to sufficient warming of the soil and sufficient humidity during this period. In summer, there is a decrease in the number of microorganisms on the soil surface, at the same time, the difference between the values at the surface and in the depth decreases.

Thereby, the most acceptable period for cleaning soil from oil is spring time.

The main natural destructors of oil and oil products are oil-oxidizing bacteria, fungi and yeast. To date, some strains of these microorganisms are already used to clean contaminated areas of hydrocarbons, especially in large quantities, they are found in places heavily polluted with oil and oil products [6].

Specialists in the field of biotechnology for the biodegradation of petroleum and petroleum products carry out the selection and selection of specialized types of microorganisms: Pseudomonas, Arthrobacter, Rhodococcus, Acinetobacter, Flavobacterium, Corynebacterium, Xanthomonas, Alcaligenes, Nocardia, Brevibacterum, Mycobacterium, Beijerinckia, Bacillus, Enterobacteriaceae, Klebsiella, Micrococcus, Spaerotilus, Serratia, microscopic fungi and yeast.

References:

1. Диаров М.Д., Гилажов Е.Г., Димеева Л.А., Большов А.А. и др. Экология и нефтегазовый комплекс: в 7 т. /Под ред. М.Д. Диарова. – Алматы: Fалым, 2003. – Т. 2. Почвенно-растительный покров. Природно-заповедные зоны. – 234 с.
2. Тимергазина И.Ф., Переходова Л.С. К проблеме биологического окисления нефти и нефтепродуктов углеводородокисляющими микроорганизмами //Нефтегазовая геология. Теория и практика. – 2012. – Т. 7, № 1. – http://www.ngtp.ru/rub/7/16_2012.pdf
3. Ветрова А.А., Иванова А.А., Филонов А.Е. и др. Биодеструкция нефти отдельными штаммами и принципы составления микробных консорциумов для очистки окружающей среды от углеводородов нефти // Известия Тульского государственного университета. Серия Естественные науки. – 2013. – В. 2., Ч.1. – С. 241– 257.
4. Мокеева А. В., Алексеев А. Ю., Емельянова Е. К. и др. Ассоциация штаммов бактерий - нефтедеструкторов для ремедиации нефтезагрязненных территорий // Вестник НГУ. Серия Биология, клиническая медицина. – 2011. – Т. 9, № 3. – С. 27-34.
5. SánchezO., FerreraI., ViguésN. et al. Presence of opportunistic oil-degrading microorganisms operating at the initial steps of oil extraction and handling // J. International Microbiology. –2006. –№ 9. –P.119-124.
6. Zhang Z., Gai L., Hou Z.et al. Characterization and biotechnological potential of petroleum-degrading bacteria isolated from oil-contaminated soils // Bioresour. Technol. –2010. –Vol. 101. –Р. 8452–8456.