Bioremediation of Spent Oil-Contaminated Soil Through the Application of Biostimulantsq

Abstract

Environmental pollution resulting from anthropogenic activities, particularly in mechanical workshop environments, has led to significant soil contamination by spent oil. Bioremediation offers an effective, eco-friendly, and cost-efficient approach for restoring such polluted soils. This study evaluates the effectiveness of biostimulation using both organic and inorganic amendments, as well as natural attenuation, in enhancing the biodegradation of spent oil in contaminated soil under controlled conditions. The initial residual oil content in soils treated with inorganic fertilizers ranged from 0.022±0.03 to 0.036±0.01 g/g, decreasing to between 0.013±0.00 and 0.023±0.00 g/g after a 42-day incubation period. Similarly, soils amended with organic fertilizers showed a reduction from an initial range of 0.033±0.01 to 0.024±0.00 g/g to final values between 0.010±0.00 and 0.023±0.00 g/g. In contrast, the untreated (attenuated) microcosm exhibited a smaller reduction, from 0.056±0.01 g/g to 0.045±0.00 g/g over the same period. Microbial population counts ranged from 1.7 × 10³ to 4.2 × 10¹⁰ CFU/g, indicating substantial microbial activity. The results demonstrate that the addition of biostimulants enhances the proliferation of indigenous microorganisms, which utilize hydrocarbons as a carbon source, thereby accelerating the biodegradation process. Although both organic and inorganic fertilizers proved effective, organic amendments showed greater potential due to their ability to introduce additional microbial populations, further enhancing remediation efficiency. Overall, the study highlights the effectiveness of biostimulation in the remediation of oil-contaminated soils and underscores the added advantage of organic amendments in improving microbial activity and soil recovery.