Post-impact studies of an inland oilfield in South-Western Nigeria: a bacteriological perspective.

Abstract

The study was designed to determine the post-impact effect of operation of Shell Petroleum Development Corporation (SPDC) in Afiesere oilfields for both rainy and dry season using bacteriological indices. Soil samples from transects, villages and water (surface and underground) from Rivers and boreholes, as well as sediments from Rivers were cultured using appropriate media for heterotrophic and hydrocarbonoclastic bacteria, respectively. The hydrocarbonoclastic bacteria consistently isola ted from samples were Pseudomonas, Bacillus, Aeromonas, Chromobacterium, Corynebacterium, Flavobacterium, Citrobacter, Micrococcus and Alcaligenes species. In general, heterotrophic counts were more than hydrocarbonoclasts. Hydrocarbonoclasts were preponderant in rainy than dry seasons along transects. The percentage hydrocarbonoclasts were lower than 1.0% except in T3, T5 and T6 with values of 1.06, 1.06 and 3.2 respectively. Lower counts were obtained for water and sediments analyzed. Pseudomonas, Aeromonas and Chromobacterium used crude oil better with optical density of 0.105 after 10 days of fermentation. Analysis with SPSS Version 17 shows there is no significant seasonal difference in the distribution of hydrocarbonoclastic bacteria in Afiesere oilfield (P<0.05) except for transect 5. We conclude that Afiesere oilfield has not suffered from petroleum crude oil pollution and that the indigenous hydrocarbonoclastic bacteria genera in the oilfield can respond appropriately in the event of a spill. More information may be needed from chemical analysis to validate this finding. The oilfield consists of numerous bacteria that can be cultured and used as inocula for bioremediation of petroleum crude impacted soils and water.