Abstract
This study was aimed at assessing the bioremediation of crude oil contaminated soil from kokori, Delta state, Nigeria by indigenous bacteria flora using cow dung as biostimulants. The activities of commercial agricultural investors, small-scale farmers, and the indigenous people of the Nigerian Niger Delta, whose livelihood has been heavily dependent on agriculture, have all been severely impeded and even destroyed by the crude oil spill. Therefore, a solution to the issue of oil spills in these places is required. Hydrocarbon contaminated soil was collected from a crude oil polluted sites and a non-contaminated soil was collected from Agricultural cultivable farmland in kokori, Delta state and its physicochemical properties were determined before the bioremediation period. The nutrients composition of cow dung used for the study was determined. After adding different amounts of cow dung to 200g of soil, the mixture was left to incubate at room temperature for six (6) weeks. Throughout the course of the experiment, measurements of the total petroleum hydrocarbon eliminated and the hydrocarbon-utilizing bacteria count (HUB) were made at one-week intervals. Increased in the HUB counts with corresponding decrease in the amount of hydrocarbons were observed. While highest HUB count was observed for the various amendment at week six, 5g/kg cow dung treatments had the highest count (3.35 x103cfu/g) with residual hydrocarbon (519.56mg/kg) while treatments 2.5g/kg cow dung had 2.91x103cfu/g with residual hydrocarbon of 541.06mg/kg. The result further revealed the degree of degradation likewise the bioremediation efficiency with C having the highest degree of degradation of (49.04%) at week six and bioremediation efficiency of (75.26%) at the first week of study. The introduction of cow dung into soil that has been contaminated with hydrocarbons promotes the growth of naturally occurring bacteria that break down hydrocarbons, leading to a greater amount of hydrocarbon degradation.

Key words: Crude oil pollution, remediation, counts, degradation, efficiency, cow dung, microorganism