A study of natural attenuation processes involved in a microcosm model of a crude oil-impacted wetland sediment in the Niger Delta

Sediment sample from a previously impacted Ochani stream was recreated in four glass chambers (A–D) as microcosms. The aim was to model and compare natural attenuation processes to forced aeration for remediation of a crude oil-impacted ecosystem. The initial hydrocarbon concentration was 90,212 mg/kg of sediment. After 60 days, the natural attenuation processes of photooxidation, evaporation, volatilization and biodegradation accounted for 31.9% of the total hydrocarbon removed while 13% was attributable to forced aeration, bringing the cumulative hydrocarbon removed to 44.9%. Photooxidation, evaporation and volatilization accounted for 15.6% of the total hydrocarbon removed. Biodegradation alone accounted for 24.7% removal. Gas chromatographic tracings showed appreciable reductions in peak heights and base. Hydrocarbon utilizing bacteria genera isolated included Pseudomonas, Micrococcus, Flavobacterium, Staphylococcus, Serratia, Bacillus, Chromobacterium, and Alkaligenes. Temperature was mesophilic (26–31 °C), while the pH tended towards acidity. The study revealed the applicability and the effectiveness of natural attenuation and forced aeration in the remediation of oil-impacted sediment in a typical Niger Delta setting.