A COMBINED REMOVAL OF OIL, TOXIC METALS AND ARSENIC FROM SOILS BY MEANS OF WILD AND LABORATORY-BRED MICROORGANISMS

摘要

In the Tulenovo oil deposit, North-eastern Bulgaria, soil, polluted with crude oil, toxic heavy metals (Pb, Cd, Cu, Zn) and arsenic was subjected to bioremediation by the heap technique. The best results were achieved in an experimental heap in which a stable microbial community consisting of both indigenous and laboratory-bred microorganisms was established. The activity of this community was enhanced by suitable changes in the levels of some essential environmental factors such as oxygen, water and nutrient contents in the soil. The oil content in the heap was decreased from the initial 23 g/kg dry soil to less than 2 g/kg dry soil within 8 months of treatment and, simultaneously, the contents of toxic heavy metals and arsenic were decreased below the relevant permissible levels.