The impact of a mixture of biosurfactants on the efficiency of the bioremediation of soil contaminated with petroleum hydrocarbons

The article presents issues related to the use of biosurfactants (surfactants of natural origin) in the bioremediation of soils contaminated with petroleum hydrocarbons. Bioremediation studies were carried out on soil contaminated with TPH (total petroleum hydrocarbons) and PAHs (polycyclic aromatic hydrocarbons) using the ex-situ pile method (semi-technical scale) in two test systems (system 1 - biodegradation of petroleum hydrocarbons by inoculation with a biopreparation, system 2 - biodegradation of petroleum hydrocarbons by inoculation with a biopreparation containing an admixture of biosurfactants). The biopreparation used in the study was developed on the basis of indigenous bacteria and fungi capable of decomposing petroleum hydrocarbons, while the biosurfactant solution consisted of a mixture of y-PGA, rhamnolipids, and surfactin. Bioremediation studies were carried out over a period of 6 months, with changes in TPH and PAH concentrations in the soil and its toxicity being monitored every 2 months. As a result of the six-month purification process, the TPH concentration was reduced from 6062.59 mg/kg dry matter (d.m.) to 1774.72 mg/kg d.m. (in system 1) and to 768.92 mg/kg d.m. (in system 2), while PAHs from 12.05 mg/kg d.m. to 4.27 mg/kg d.m. (in system 1) and to 2.20 mg/kg d.m. (in system 2). The addition of biosurfactants to the inoculant allowed to increase the biodegradation effectiveness of TPH by 16.59% and PAH by 17.17% compared to inoculation with the biopreparation alone. Toxicological analyzes carried out using the PhytotoxkitTM, TM , OstracodtoxkitTM TM and Microtox (R) STP (R) STP tests showed an improvement in soil quality as a result of the bioremediation and confirmed that a reduction in the petroleum hydrocarbons concentration decreased the negative impact of the biotreated soil on the test organisms. Research conducted in the two systems allowed for the assessment of the impact of the biosurfactants on the effectiveness of bioremediation process of soil contaminated with TPH and PAHs and enabled improvement of methods used for the reclamation of crude oil-contaminated soil.