ИСТИНА

In our earlier studies it was shown that the aerobic oil-degrading bacteria of the genus Rhodococcus forming the basis of the commercial oil-oxidation preparation «Rhoder» are able to degrade oil hydrocarbons (HC) under anaerobic conditions in the presence of certain electron acceptors on soils contaminated by accidental oil spills, both in laboratory and field experiments. The present work is devoted to the study of the influence of the electron acceptor doses in the form of the nitrate containing salt on the HC degradation in the soil under anaerobic conditions by the action of the Rhoder aerobic bacteria. The soil with 10% contamination of petroleum hydrocarbons (PH) excavated from a 10 m deep well was treated with a working solution of the Rhoder with a concentration of hydrocarbon oxidation bacteria (HCO) of 109 cells/ml in anaerobic batch reactors with volume of 120 ml of each in a ratio of soil:working solution as 1:1. Ca(NO3)2 was investigated as electron acceptors at three different concentrations: 12.5g/l; 25g/l and 50g/l. NH4NO3 (3,0g/l) was added to each of the three bioreactors as a source of ammonium nitrogen. The destruction process of the HC was carried out at a temperature of 28° C. The results of biological treatment of the soil contaminated with HC showed that a lag period of 2 and 3 days was observed at concentrations of Ca(NO3)2 of 25 and 50g/l into the medium caused by the adaptation of aerobic bacteria to the high concentrations of calcium nitrate. At the same time, a lower concentration of calcium nitrate in the medium (12.5g/l) made it possible to detect degradation of HC by the aerobic bacteria of the Rhoder from the first day of the experiment. The degradation rate constant of the HC was 1.19 per year-1 and the half-life of the HC was 0.58 year. The carried out researches have shown that the content of calcium nitrate must be not less than 12.5g/l to maintain the achieved the degradation rate of HC by aerobic bacteria of the Rhoder in the reactors, otherwise there is a risk of launching competing biological processes of sulfate reduction and methanogenesis by soil indigenous microorganisms under anaerobic conditions