Microbiological Oxidation of High Viscosity Bitumen in Soil

Abstract

This paper presents the results of an investigation of microbiological oxidation in the model soil system of high viscosity bitumen from the Bayan-Erkhet deposit (Mongolia) with a high content of heteroelements. It is shown that bitumen, being a mixture of high molecular weight components, has no inhibitory effect on the indigenous soil microflora. Its active growth in the presence of oil products starts without adaptation and lasts for a good part of experiment resulting in 15‒30 fold excess of microorganisms over its reference number. The enzymatic activity of the contaminated soil increases by a factor of 1.5‒2.0, which indicates an assimilation of various hydrocarbon compounds. The weight analysis revealed that
the biodegradation of oil products after 180 days of the experiment was 50% of the initial contamination at initial waste oil concentration 50 g/kg (5%). The analysis by IR spectroscopy revealed an accumulation of oxygen-containing compounds which are intermediate products of bio-oxidation of bitumen components. The method of chromatography-mass spectrometry (GC-MS) revealed the ability of
aboriginal soil microflora to mineralize virtually all hydrocarbons contained in the bitumen under study. Their biodegradation ranges from 18 to 97%. It was shown by the GC-MS method that high-molecular heteroatomic components of bitumen (resins and asphaltenes) also undergo a microbial degradation, since their molecular structure changed after the destruction. Thus, the number of structural units in a
hypothetical molecule and that of heteroatoms increased due to the high content of oxygen-containing structures. In addition, the ratio of hydrocarbons (oils), resins, and asphaltenes contained in the sample is also changed.