Biotechnology for Recultivation of Oil Polluted Soils

Abstract

All the biotechnologies intended for improvement of environmental conditions are based on the ability of microorganisms for hydrocarbon oxidizing. In the development of biotechnological approaches for soil re-cultivation the extent of soil pollution has to be taken into account. Among the advantages of a technology employing mineral nutrient substrates for enhancing the oxygenizing activity of soil microflora its cost-effectiveness is very important. When dealing with highly polluted soils, more complex methods for soil restoration are called for; however, these are much more labour-extensive and time-consuming. Experimental investigations have been performed to study the effect of oil pollutants on the ability of soil microflora to assist the destruction of hydrocarbons. Variation in the activity of indigenous soil microflora was investigated using three major groups of bacteria, i.e. Heterotrophs, Actinomycetes and microfungus cultures. The presence of oil in amounts constituting up to 5% is found to stimulate the growth and oxygenizing activity of the soil biocenosis. Thus the residual oil samples were exposed into the soil microflora for a time period of 60 days and then analyzed by gas-liquid chromatography (GLC). The results obtained reveal significant changes in the molecular-mass distributions of saturated hydrocarbons C₉-C₃₂. An addition of stimulating nutrient substrates is found to enhance the biochemical activity of soil microorganisms. Thus a 60 days' contact with soil microflora resulted in destruction of 80–85% of the saturated oil hydrocarbons, mostly C₉-C₁₅ and C₂₀-C₃₁ compounds. However, the occurrence of 10% oil pollutants exerts an inhibiting effect on the indigenous soil microflora; therefore, only an insignificant amount of hydrocarbons undergoes degradation.