Stimulating Indigenous Anaerobic Microorganisms for the Bioremediation of a Geological Environment Polluted with Petroleum Products

Changes in the number of anaerobic microorganisms (denitrifying, sulfate, and iron-reducing) in ground and groundwater polluted with oil products have been investigated during bioremediation. It is shown that, in the studied geological media, the number of psychrophilic microorganisms of anaerobic groups (denitrifying and sulfate and iron-reducing, as assessed by the number of the colony-forming units on the respective cultivation media) is higher than the number of mesophilic ones. When N, P, and K fertilizers are introduced into the contaminated zone, the number of psychrophilic microorganisms changes more significantly, both increasing and decreasing. When the ground in the aeration zone is treated, the number of anaerobes decreases, probably due to competitive displacement by aerobes. The number of hydrocarbon-oxidizing and ammonifying microorganisms increases by an order of magnitude to 10⁶ CFU/g and 10⁶–10⁷ CFU/g, respectively. When fertilizers are added to groundwater, the number of anaerobic microorganisms increases 1-4 orders of magnitude and the number of denitrifiers reaches 10⁵ CFU/mL, whereas the CFU number of sulfate and iron reducers is 10³–10⁴ and 10²–10³ CFU/mL, respectively. It is revealed that, simultaneously with the increase in CFU numbers, some chemical properties change, indicating the intensified biodegradation of petroleum products. In particular, antiphase changes in the ammonium and nitrate concentrations are observed due to the decomposition of petroleum products, nitrification, and denitrification, as well as the concentration of bicarbonate and sulfate ions due to sulfate reduction.