Change of isoprenoids, steranes and terpanes during ex situ bioremediation of mazut on industrial level

The paper presents results of the ex situ bioremediation of soil contaminated by mazut (heavy residual fuel oil) in the field scale (600 m3). A treatment-bed (thickness 0.4 m) consisted of mechanically mixed mazut-contaminated soil, softwood sawdust as the additional carbon source and crude river sand, as bulking and porosity increasing material. The inoculation/reinoculation was conducted periodically using a biomass of a consortium of zymogenous microorganisms isolated from the bioremediation substrate. The biostimulation was performed through addition of nutritious substances (N, P and K). The aeration was improved by systematic mixing of the bioremediation system. After 50 days, the number of hydrocarbon degraders increased 100 times. Based on the changes in the group composition, the average biodegradation rate during bioremediation was 24 mg/kg/day for the aliphatic fraction, 6 mg/kg/day for the aromatic fraction, and 3 mg/kg/day for the nitrogen-sulphuroxygen compounds (NSO)-asphaltene fraction. In the saturated hydrocarbon fraction, gas chromatography-mass spectrometry (GC-MS) in the single ion-monitoring mode (SIM) was applied to analyse isoprenoids pristane and phytane and polycyclic molecules of sterane and triterpane type. Biodegradation occurred during the bioremediation process, as well as reduction of relative quantities of isoprenoids, steranes, tri- and tetracyclic terpanes and pentacyclic terpanes of hopane type