Biostimulatory Effect Of Processed Sewage Sludge In Bioremediation Of Engine Oil Contaminated Soils

A study was conducted to evaluate the influence of sewage sludge on biodegradation of engine oil in contaminated soil. Soil samples were collected from a mechanics workshop in Sokoto metropolis. The Soil samples were taken to the laboratory for isolation of engine oil degrading bacteria. About 1 g of soil sample was used to inoculate 9 ml of trypticase soy broth and incubated at 28oC for 24 h. The growth obtained was sub-cultured in mineral salt medium overlaid with crude oil and allowed to stand at 28oC for 72 h. The culture obtained was then maintained on tryticase soy agar plates at 28oC for 48 h. A combination of microscopy and biochemical tests was carried out to identify the colonies. The sewage sludge was obtained from sewage collection point located behind Jibril Aminu Hall of Usmanu Danfodiyo University Sokoto and processed i.e. dried grounded and sterilized. A portion of land obtained in a botanical garden was divided into small portions 30 X 30 cm and the soil was excavated in-situ and sterilized in the laboratory. A polythene bag was subsequently used to demarcate between the sterilized soil and the garden soil. The sterilized soil plots were artificially contaminated with equal amount of used engine oil to represent a typical farmland oil spill. The plots were amended with various amount of processed sewage sludge i.e. 200 g 300 g and 400 g respectively. A pure culture of the bacteria was maintained on trypticase soy broth and was introduced into the sterile amended soil. The plots were watered twice daily for ten days. The degree of biodegradation and heavy metal content were assessed using standard procedures and the results obtained indicate a remarkable reduction in poly aromatic hydrocarbons PAHs total petroleum hydrocarbon TPH and heavy metal content.