The effect of the dispersant Corexit 9500 on the biodegradation of North Sea crude oil at low temperatures
MetadataShow full item record
Constituents from crude oil and petroleum are major sources of marine pollution and despite the natural presence of crude oil hydrocarbons in the marine environment; anthropogenic activity is a major contribution to the total release of hydrocarbons to the oceans. The removal of hydrocarbon pollution is based on the natural weathering mechanisms, specifically biodegradation and its enhancement. Chemical dispersants have been developed that serve to disperse spilled oil more rapidly and extensively into the water column as tiny oil droplets, increasing the surface area available for microbial biodegradation. This study was conducted to investigate the effect of temperature on biodegradation, as well as the effect of the chemical dispersant Corexit 9500 on the enhanced biodegradation of crude oil from the Norwegian oil field, Ekofisk. The biodegradation of the dispersant alone was also investigated. Both chemical and microbiological methods were used to analyse the effects on biodegradation at 3, 8 and 15°C. BOD analysis showed increased biodegradation rates with increasing temperature. Total hydrocarbon analysis via GC-‐FID revealed that between 82 and 95% of hydrocarbons in the size range between decane and tetracosane were degraded over a period of 46 days. The addition of Corexit showed an increase of hydrocarbon removal of 2% at 8 and 15°C, and 10% increased removal at 3°C. Molecular analysis revealed changes in the microbial community of samples containing crude oil. All samples, including blank samples showed a shift in the microbial community from the original community found in the source seawater, over the biodegradation period of 46 days. Based on the results of this study it was concluded that the addition of Corexit 9500 had little or insignificant effects on the rate of biodegradation of North Sea crude oil in seawater at all temperatures. Increased biodegradation rates were however clearly observed as temperature increased. Further research is recommended to better understand the effects of chemical dispersants on biodegradation in low temperature marine environments and to develop more successful methods for the remediation of hydrocarbon contamination.
Master's thesis in Environmental technology