Response of Soil Microorganisms to Oilfield Wastewater

Environmental pollution resulting from oil exploitation and exploration has impacted negatively on the biodiversity of the affected areas. Therefore, this study investigated the response of soil microorganisms to oilfield wastewater. The oilfield wastewater and soil samples were collected from an onshore oil producing platform fortnightly for a period of three months and microbiological analyses were performed using standard methods. Soil around pond average counts for THB and HUB (Log10 CFU/g) were 7.32 to 7.35 and 4.16 to 4.22 respectively. Soil 80 m away from pond average range for THB and HUB were 7.38 to 7.40 and 3.32 to 3.34 respectively. For TF and HUF, Soil around the pond mean recorded 4.65 to 4.85 and 4.12 to 4.16 (Log10 CFU/g) respectively. Mean monthly counts for soil 80m away TF and HUF (Log10 CFU/g) were 5.03 to 5.05 and 3.26 to 3.34 respectively. Soil around the pond recorded lower total heterotrophic bacteria count and total fungi count but higher hydrocarbon utilizing bacteria and hydrocarbon utilizing fungi than soil 80 m away.

There was significant difference (P<0.05) between the THB and HUB in the various samples. For the fungi count there was no significant difference (P>0.05) between TF and HUF in all the samples except in sample obtained from soil 80 m away from pond.

Bacteria species isolated from the study include: Bacillus, Aeromonas, Micrococcus, Staphylococcus, Chryseomonas, Proteus, Pseudomonas, Klebsiella. Apart from Aeromonas and Chryseomonas the rest of the isolate were identified also as hydrocarbon utilizing bacteria. While fungi species isolated includes: Aspergillus fumigates, Aspergillus niger, Aspergillus flavus, Saccharomyces cerevisiae, Geotricum, Trichoderma, Fusarium and Penicillium. Hydrocarbon utilizing fungi that occurred includes: Aspergillus niger, Aspergillus flavus, Fusarium, Penicillium and Saccharomyces cerevisiae. The response of these microorganisms in the oil polluted environment suggests that the isolated bacteria and fungi could utilize the oil as energy and carbon source and could be effective in the cleanup of the polluted sites.