Remediation of soil polluted with spent oil using cow dung

Spent oil is any petroleum-based or synthetic oil that contain impurities or loss of major properties thus affecting its unique purpose. In this study, we selected and contaminated a site in Covenant University with spent oil. This site was amended with cow dung and studied for 56 days. Spent oil contaminated soil without stimulation with cow dung served as the control. This study was done during the dry season period and the sites left to natural edaphic factors. Physicochemical parameters such as pH, moisture content were monitored to determine the influence of cow dung as biostimulatory agent when compared with control (untreated) site. Within the period of this investigation, we recorded decrease in the pH value on the amended site, the value ranged between 8.60-7.77 while the control increased from 8.30 -8.42. The moisture content (%) were 95.0- 82.1 and 90.8-103.0 for the amended and control sites respectively. Following these obtained dynamics, we isolated organisms using enrichment technique from the contaminated sites and the control. We characterized the isolates using phenotypic characteristics and comparison with standard reference organisms. The bacterial isolates obtained include: Arthrobacter Mycobacteria Pseudomonas and Corynebacterium. The axenic cultures ability to utilize spent oil was monitored via indirect estimation using pH and Optical density dynamics for 240hrs. All the organisms exhibited growth in the MS medium supplemented with spent oil. The pH and optical density (OD) from bacterial species obtained from the control sample ranged between 6.91 ± 0.20- 6.56± 0.29 and the OD 0.278±0.150-0.826 ± 0.33. For the amended sample, the bacterial species showed decline in pH that ranged between 7.13±0.30 - 6.33±0.10 while the recorded OD values ranged between 0.190±0.03 - 0.621±0.50. Comparing the results obtained for the control and the amended soil. It was obvious that organisms from the amended soil (either in-situ or in-vivo) showed more metabolic activities on the spent oil. This study suggests that use of cow dung in appropriate concentrations could be very useful in bioremediation of soil contaminated with spent oil.