DETERMINING DISPERSANT EFFECTIVENESS DATA FOR A SUITE OF ENVIRONMENTAL CONDITIONS

• Main Authors: S Chandrasekar, G Sorial, J Weaver
• Format: Text
• Language: unknown
• Published: 2005
• Subjects: Eros; Alaska North Slope; north slope; Alaska
• Online Access: http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=62125

Chemical dispersants are used in oil spill response operations to enhance the dispersion of oil slicks at sea as small oil droplets in the water column. To assess the impacts of dispersant usage on oil spills, US EPA is developing a simulation model called the EPA Research Object-Oriented Oil Spill (ERO3S) model (http://www.epa.gov/athens/research/projects/eros/). Due to the complexity of chemical and physical interactions among spilled oils, dispersants and the sea, an empirical approach to the interaction between the dispersant and oil slick may provide a useful or practical approach for including dispersants in a model. The main objective of this research was to create a set of empirical data on three oils and two dispersants that has the potential for use as an input to the ERO3S model. These data were intended to give an indication of the amount of dispersal of these oils under certain environmental conditions. Recently, the US EPA developed an improved dispersant testing protocol, called the baffled flask test (BFT) which was a refinement of the swirling flask test. This protocol was the basis of the experiments conducted in this study. The variations in the effectiveness of dispersants caused by changes in oil composition, dispersant type, and the environmentally related variables of temperature, oil weathering, and rotational speed of the BFT were studied. The three oils that were tested were South Louisiana Crude Oil, Alaska North Slope Crude, and Number 2 fuel oil. Two dispersants that scored effectiveness above 85% by the BFT were selected for this study. A factorial experimental design was conducted for each of the three oils for the four factors, namely, volatilization, dispersant type, temperature and flask speed. Each of the four factors was studied at three levels except for the dispersant factor where only two dispersants are considered. Statistical analysis of the experimental data was performed separately for the three oils. Analysis of variance was conducted to determine which factors, or set of factors were related to the percent effectiveness. Empirical relationships between the amount of oil dispersed and the variables studied were developed.