Optimisation research of petroleum hydrocarbon biodegradation in weathered drilling wastes from waste pits

The aim of this article is to discuss the problem of drilling waste remediation. Analyses and research showed that material stored in waste pits could be classified as soil with a high level of petroleum impurities (total petroleum hydrocarbons [TPH] = 102,417—132,472 mg kg^—1 dry mass). While preparing the complex technology of soil decontamination (which included primary reclamation, basic bioremediation and inoculation with biopreparations based on indigenous bacteria and fungi), laboratory tests indicated the use of an ex-situ method was fundamental. Remediation was controlled with a chromatographic method of qualitative and quantitative determination of petroleum hydrocarbons. Based on analytical data, there was the possibility to determine the effectiveness of consecutive purifying phases. Laboratory tests, following 135 days of basic bioremediation stimulated by optimum conditions to activate the growth of indigenous micro-organisms, resulted in a decrease in the TPH content, which was in the range of 52.3—72.5%. The next phase of soil decontamination lasted 135 days and involved the use of inoculation with biopreparations based on indigenous micro-organisms and fungi. This process enabled a TPH decrease of 93.8— 94.3%. Laboratory biodegradation research was done with the use of the biomarker C₃₀-17α(H)21β(H)-hopane to normalize analyte (TPH, Σn-C₈—n-C₂₂ and Σn-C₂₃—n-C₃₆) concentrations. The calculated first-order biodegradation constants enable estimation of the purification stage dynamics and the effectiveness of the applied biopreparations. Furthermore, they represent the biodegradation degree of individual n -alkanes in subsequent stages of the soil purification process.