Evaluating Surface Washing Agent Performance

Robert Grosser, Robyn Conmy, Devi Sundaravadivelu, Andrea Burkes, Edith Holder, Emma Webster, Raghu Venkatapathy
2021 International Oil Spill Conference Proceedings  
Surface washing agents (SWAs) can be used to enhance removal of spilled oil from shoreline surfaces and structures. There are two classes of SWA products, "lift and float" products which remove the oil from the surfaces to create an oil slick which can be recovered mechanically and "lift and disperse" products which emulsify and disperse the oil into the water column, which are more difficult to remove mechanically. Therefore, information regarding the ability of a product to lift oil from a
more » ... face and its mechanism of action once the oil has been removed is important for oil spill responders. The SWA effectiveness (SWAE) of 15 products (conducted and reported blind) listed on the NCP Product Schedule was evaluated by applying oil to a sand substrate, allowing time for the oil to adhere to the substrate, treating with SWA, and washing with artificial seawater to release any oil that has been lifted from the substrate surface. The efficiency of SWAs is calculated based on the mass of oil remaining on the substrate relative to the total mass of oil applied. The Dispersant Effectiveness (DE) of SWA products was determined using the Baffled Flask Test and was used to sort products based on their mechanism of action ("lift and disperse" rather than "lift and float"). Using a sand basket approach, the amount of oil remaining in sand varied from 10 to 95% for the various products tested, where a lower percent signifies a better SWA. The DE varied between 8 and 81%. Though previous studies have concluded that good SWAs are poor dispersants and vice versa, the results from this study demonstrate that this is not a general rule. A stoplight decision framework was developed that considers the relationship between DE and SWAE, and serves to identify products whose primary mechanism is "lift and disperse" rather than "lift and float." Results suggest that regardless of which test is used to evaluate SWAs, coupling findings with DE can provide useful information for decisions during response operations.
doi:10.7901/2169-3358-2021.1.1141596 fatcat:blb27udjs5bo7g2dojpiy3tx5y