Screening of organic wastes and microorganisms for bioremediation of spent lubricating oil polluted soil

Abstract

Spent lubricating oil polluted soil was remediated with organic wastes; cow dung (CowD) and chicken droppings (ChiD) (animal wastes), corn cob (CorC) rice husk (RicH) and sorghum husk (SorH) (plant wastes). The nitrogen contents of the organic wastes were determined to be 11.45, 10.92, 9.80, 9.66 and 12.04g/kg respectively. The organic wastes were screened for ability to remediates spent lubricating oil polluted soil. The potential of the organic wastes to remediate spent lubricating oil polluted soil was monitored for 12 weeks by measuring the pH, moisture contents, microbial counts nitrogen contents and total petroleum hydrocarbon (TPH). The pH of unremediated soil ranged from 6.14– 6.31 while that of soil remediated with CowD, CorC, ChiD, RicH and SorH ranged from 6.18 – 7.25, 6.12 – 6.42, 6.38 – 7.51, 6.20 – 6.52 and 6.22 – 6.45 respectively after 12weeks. The results showed that reduction in pH of the treatments were higher compared to the control. Also there was an increase in microbial count of the treatments while there was reduction in that of the control. The nitrogen content in spent lubricating oil polluted soil (control) was lower compare to all the treatments. The nitrogen content in soil treated with CowD, CorC, ChiD, RicH and SorH reduces from 12.82– 9.24 g/kg, 11.14 – 9.46 g/kg, 12.26 – 8.16 g/kg, 11.01 – 9.52 g/kg and 13.38– 9.22g/kg respectively after 12 weeks. The percentage of oil degradation in soil remediated with organic wastes (CowD, CorC, ChiD, RicH and SorH) increased from 22.22 – 68.52%, 14.19 – 61.11%, 23.46 – 74.07%, 6.0 – 57.40% and 20.37 – 66.67% respectively after 12 weeks. The percentage of oil degradation was low in the control soil compared to the treatments, meaning that the organic wastes added to the polluted soil enhanced the activities and populations of microorganisms to remediate the oil polluted soil. This revealed that organic wastes had the potential to enhance the activities and populations of microorganisms to remediate the oil polluted soil considerably