EVALUATION OF THE EFFICIENCY OF INTRINSIC MICROORGANISMS IN THE REMEDIATION OF CRUDE OIL POLLUTED SOIL MICROCOSMS

Abstract

Soil provides habitat for diverse types of microorganisms. This study investigated the effectiveness of indigenous soil microorganisms in natural attenuation. Soil samples used in this study were collected from Awoye, Orioke- Iwamimo, Igodan- Lisa, Oba-Ile and Idoani all in Ondo State, Nigeria. Samples were collected into sterile black cellophane bags using hand auger at depth of 15- 20 cm. One set (200 g) of partially air- dried, homogenized and sieved samples were sterilized by autoclaving for three consecutive times at 121^oC for 30 min. The moisture contents of the soil samples were adjusted with sterile water to obtain 25% (w/w) and contaminated with sterile crude oil by thoroughly mixing crude oil with the soils to obtain 5% (w/w) crude oil pollution. The weight loss method was used to determine the amount of crude oil in samples and then evaluated for amount of crude oil lost at intervals of 30 days for six months. The results indicated that the amount of crude oil degraded was higher in non- sterile soil samples (41.01- 49.00%) than the sterile samples (17.00 -22.99%). This implies that crude oil degradation by intrinsic soil microorganisms constituted 52.33-58.74% of crude oil reduction by natural attenuation. It could be concluded that crude oil removal from soil occurred without human intervention due to the activities of autocthonous microorganisms. This study concludes that soil is rich in microorganisms possessing the desired catabolic potentials for crude oil utilization.