|Dispersion of Crude Oil and Petroleum Products in Freshwater (EPA/600/R-08/037) March 2008
The objective of this research was to investigate the relationship between dispersion effectiveness in freshwater and the surfactant composition for fresh and weathered crude oil. Although limited research has been conducted on the chemical dispersion of crude oil and petroleum products in freshwater, previous studies did not identify the dispersants that were investigated, much less describe the chemistry of the surfactants that were used. The absence of information on surfactant composition is a major impediment to the scientific investigation of dispersant effectiveness because this information is necessary for the development of a more fundamental understanding of dispersant effectiveness. Therefore, the relationship between surfactant chemistry and dispersant effectiveness was systematically evaluated. This report showed that, at least with Mars Blend crude oil in simulated lake water, dispersants can be designed to drive an oil slick into the freshwater column with the same efficiency as in saltwater as long as the hydrophilic-lipophilic balance is optimum. Clearly, many more oils would need to be tested under different conditions (temperature, organic content, water composition, etc.) to enable firm conclusions that oil can be dispersed in freshwater as a response tool. The ultimate decision to use dispersants in treating freshwater petroleum oil spills is up to the federal on-scene coordinator, the incident command team, the regional response teams, and EPA headquarters, because many other factors need to be considered before rendering a decision to disperse oil into the water column. It is beyond the scope of this report to consider such factors. Its purpose was simply to determine whether freshwater dispersion is possible and to determine whether effective freshwater dispersants can be designed to produce stable oil droplet distributions in such an environment.
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