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Field-scale experiments on bioremediation of soil heavily contaminated with crude oil were undertaken on the territory of the Kokuyskoye oil field (Perm region, West Urals, Russia) owned by the LUKOIL Company. The pollution consisted of the contents of a oil waste storage pit, which mostly received soils contaminated after accidental oil spills and also the solid n-alkane (paraffin) wastes removed from the surface of drilling equipment. Laboratory analyses of soil samples
indicated contamination levels up to 200 g/kg of total recoverable petroleum hydrocarbons (TRPH). Average oil composition consisted of 64% aliphatics, 25% aromatics, 8% heterocyclics, and 3% of tars/asphaltenes. Ex situ bioremediation techniques involved the successive treatment of contaminated soil using a bioslurry reactor and land farming cells. An oleophilic biofertilizer based on Rhodococcus surfactant complexes was used in both treatment systems. An aerobic slurry bioreactor was designed, and the biofertilizer applied weekly. Slurry-phase biotreatment of the contaminated soil resulted in an 88% reduction in oil concentration after 2 months. The resulting reactor product, containing approximately 25 g/kg of TRPH, was then loaded into land farming cells for further decontamination. To enhance bioremediation, different treatments (e.g., soil tilling, bulking with woodchips, watering, and biofertilizer addition) were used The rates of oil biodegradation were 300 to 600 ppm/day. As a result, contamination levels dropped to 1.0 to 1.5 g/kg of TRPH after 5 to 7 weeks. Tertiary soil management involved phytoremediation where land farming cells were seeded with a mixture of three species of perennial grass. The effect of phytoremediation on the residual decontamination and rehabilitation of soil fertility is being evaluated.
KEY WORDS: bioremediation, oil-contaminated soil, oleophilic biofertilizer, slurry bioreacter, land farming cells.
INTRODUCTION
Perm region has one of the largest oil-extracting areas in Russia where crude oil has been extracted using traditional drilling technology for several decades. This involved the preliminary settling of crude oil in settling pits to achieve separation of the hydrocarbon fraction from drilling fluids and cuttings. In later years, modern separation systems have reduced the need for so many settling pits. Some of the pits have begun to be used as waste storage reservoirs for the disposal of oily wastes from drilling wells and oil-contaminated soil. The content of these pits represents significant potential harm for the...