Abstract

O. A. Ojo

The application of a consortium of native bacterial species in bioremediation processes has long been desired in Nigeria because they would be cost effective and efficient in terms of acclimation time. Two Nigerian crude oils (Bonny light and Escravos blend) were exposed to the wastewater canal via oil impregnated membrane filters (0.45 µm diameter) for 21 days in a microcosm experiment. Bacterial petroleum-hydrocarbon utilizers were later harvested from both the millipore membrane filters and laboratory biodegradative studies. Some of the striking discoveries made were that pH fluctuations in the reaction flasks were due to microbial activities, microbial enzymes, presence of crude oil degradation metabolites such as organic acids, surfactants and aldehydes. More petroleumhydrocarbon utilizers were detected at 0 to 15 cm depth than at 15 to30 cm. The petroleum sample with higher fractions of saturated hydrocarbon was biodegraded faster (Bonny light) than the ones with higher fractions of asphaltenes and aromatics (Escravos blend). Escravos blend had C-14 component undegraded after the 3-week oil explosure to the waste water. The physico-chemical properties of the freshwater ecosystem were determined and it supported previous conclusion on the latent self purification capability of the aquatic ecosystem inspite of frequent oil pollution incidents. The mean temperatures of the freshwater ecosystem were within the mesophilic range 27-29°C and the pH of the environment supported acidophilic bacterial consortium. Gas chromatographic profiles of the mineralization process of Bonny light and Escravos blend gave the conclusive evidence for the capability of the native bacterial population to mineralize petroleum hydrocarbons in wastewater, at optimum physico-chemical conditions in the habitat. Petroleum-hydrocarbon utilizers detected included Bacillus megaterium, Pseudomonas putida, Micrococcus luteus, Bacillus brevis, B. punilis and Enterobacter aerogenes.