Abstract

The biodegradability of three oil spill dispersants (teepol, sodium dodeocyl sulphate (SDS) and corexit 9527) in a brackish water were monitored using the ratio of dissolved organic carbon (DOC) to total organic carbon (TOC) (primary biodegradation), the ratio of inorganic carbon to total organic carbon (mineralization) and total microbial (bacteria and fungi) population. The study lasted for 20 days. Sampling was done every 5 day period (0, 5, 10, 15 and 20 days). The biodegradation setup containing corexit 9527 dispersant showed the highest primary biodegradation (98.3%), followed by teepol (69.2%) and SDS (58.3%) at the 20^th day. The percentage mineralization of the biodegradation setup containing teepol, SDS and corexit 9527 was 19.2, 7.8 and 3.3%, respectively, at the 20^thday. The total heterotrophic bacterial (THB) and fungal counts were slightly decreased compared to the control with increasing time interval. However, SDS dispersant supported the highest THB and dispersant-utilizing bacteria, followed by teepol and corexit 9527, while teepol showed the highest fungal count. Teepol was the most biodegradable of the test dispersants in this study, followed by SDS and corexit9527. This study reveals the toxic implications of some dispersants used in oil spill control on the growth of aquatic microbial population and the biodegradability of the dispersants, and therefore suggests that, ecotoxicological analysis of oil spill dispersants should be carried out before field application on any natural ecosystem since some of them are not completely biodegradable and persist in the such environments.

Key words: Ecosystem, oil spill, biodegradation, dispersants, brackish water.