BIOREMEDIATION OF SPENT OIL - CONTAMINATED SOIL USING BIOSTIMULANTS

Anthropogenic activities such as those occurring in mechanical workshops have caused environmental pollution. Bioremediation, a biological method that is cost effective, safer and environmentally friendlyfor reclaiming polluted land can be utilized to degrade the spent oil in soil. This study compared the bioremediation of spent oil-contaminated soil using biostimulants such as organic and inorganic biostimulants and attenuated microcosms within a short period via appropriate standard methods. The initial residual oil content of the microcosm bio-stimulated with various quantities of inorganic fertilizer ranged from 0.022±0.03 to 0.036±0.01 g/g, while at the end of the 42-day incubation period, the residual oil content ranged from 0.013±0.00 to 0.023±0.00 g/g. However, the amount of residual oil in the microcosms biostimulated with organic fertilizer ranged from 0.033±0.01 to 0.024±0.00 g/g at the outset and from 0.010± 0.00 to 0.023±0.00 g/g at the end of the process. The mean residual oil content of the attenuated microcosm ranged from 0.056±0.01 g/g at the beginning of the biostimulation period to 0.045±0.00 g/g at the end of the incubation period. The number of colony-forming units of the inherent microbes ranged from 1.7 × 103 to 4.2 × 1010 CFU/g. The results indicate that the biostimulants stimulated the growth of inherent microbes for the biodegradation of spent oil by utilizing the spent oil as the sole source of carbon, thereby remediating the contaminated soil. The results also showed that both organic and inorganic fertilizers can be used as biostimulants, but organic fertilizers add their inherent microbes to contaminated soil, thereby increasing the microbial load of the soil, which enhances its remediation.