Impact of Rigwash Oil Spill ‘Dispersants’ on the Biodegradation of Crude Oil in Nigeria

Aim: To ascertain the impact of Rigwash oil spill ‘dispersant’ on the biodegradation of crude oil.

Study Design: The study employs experimental design and statistical analysis of data and interpretation.

Place and Duration of Study: The water sample for the study was collected from Okrika High Sea via Adedemebiri, Rivers State of Nigeria at a depth of 1 m. It was transported to the laboratory at 25 – 30°C within 2 hours. The ‘dispersant’ and the oil were obtained from an industrial chemical store at Trans-Amadi, Port Harcourt and from the Nigerian National Petroleum Corporation (NNPC), Port Harcourt, Rivers State of Nigeria respectively. Experimental analyses were done at the Departments of Microbiology, and Biochemistry, University of Port Harcourt, Rivers State, and at the Federal Institute of Industrial Research, Oshodi (FIIRO), Lagos State. The biodegradation setups were monitored at a weekly interval over 21-days period at room temperature (approximately 30°C) on a static shake-flask system.

Methodology: Standard techniques such as the spread plate method, titrimetric technique, atomic absorption spectrophotometry and Gas Chromatography (GC-FID) were adopted during the study. The preliminary range findings involves plating out in duplicates on nutrient agar an 0.1 ml aliquot of a mixture of 100 ml seawater and each of the different concentrations of ‘dispersants’ (0, 0.01,0.1,1.0, 2.0, 5.0,10, 20, 50, 100,1000) ml (v/v) respectively. The cultures were incubated at 35°C for 48 hours. Analysis of variance at confidence limit P ≤ 0.05 was adopted.

Results: The result of the study revealed that Rigwash oil spill ‘dispersant’ may have negative impact on the biodegradation of Bonny light crude oil over time. The effect may portend great danger to the health, safety and environment of aquatic floras and faunas of marine systems. The level of biodegradation achieved for the crude oil-dispersant mixture (K2) and crude oil alone (R2) were 1.01% and 1.10% respectively. Analysis of variance at confidence limit P ≤ 0.05 showed that there was no significant difference in the biodegradation of crude oil or its combination with Rigwash oil spill ‘dispersant’.

Conclusion: Rigwash oil spill ‘dispersant’ may have negative impact on the biodegradation of Bonny light crude oil. However, this may be injurious to the health, safety and environment of living organisms.