U.S. Navy Ship Salvage Manual Volume 6 - Oil Spill Response

S0300-A6-MAN-0606.3 SURFACE COLLECTING AGENTSSurface collecting agents absorb, congeal, trap, fix or make the mass of oil more rigid or viscous,which enhances mechanical removal. Surface collecting agents are applied to the surface or alongthe periphery of an oil slick. Surface collecting agents include elastomers, gelling agents andherding agents.6.3.1 Elastomers. Elastomers are the most promising surface collecting agent. An elastomer—usually a powder formulated from a nontoxic polymer (polyisobutylene)—gives a visco-elasticproperty to spilled oil and makes the oil somewhat adhesive to oil spill recovery equipment.Tests show that elastomers are effective on a wide range of oils. Effectiveness is increased bymixing and high temperatures. Under good mixing conditions, oils exhibit some degree of elasticitywithin 15 minutes of application, with maximum elasticity being achieved after one hour.Weathering increases the elasticity of treated oil, thus adding to the productivity of elastomers.6.3.2 Gelling Agents. Gelling agents cause oil to become solid or semisolid. While gellingagents may control a spill, gelled oil is difficult to handle with conventional response equipment.The large amount of gelling agent required—up to 40 percent of the volume of spilled oil—makesgelling agents impractical for most spills.6.3.3 Herding Agents. Herding agents stop oil from spreading by pushing oil films together.They function best on small spills in absolutely calm water and, therefore, have little overallutility.6.3.4 Approval. Procedures for gaining permission to apply surface collecting agents are thesame as those for dispersants. Approved surface collecting agents are included in the EPANational Contingency Plan Product Schedule.6.4 BIOLOGICAL ADDITIVESBiological additives are microbiological cultures, enzymes or nutrient additives, deliberatelyintroduced into an oil spill for the specific purpose of encouraging biodegradation to mitigate theeffects of the spill. Because natural biodegradation is a slow process, degradation of oil by biologicalmeans—or bioremediation—has not been a primary means of removing oil from contaminatedsites. Only recently has bioremediation received significant attention as a responsemechanism.Biological additives were applied effectively in response to the oil spills from EXXON VALDEZin Alaska in 1989 and from MEGA BORG in the Gulf of Mexico in 1990. In Alaska, bioremediationcleaned oil from several miles of contaminated beaches. In the MEGA BORG spill, biologicaladditives were applied to the light Angolan crude oil at sea.6.4.1 Biodegradation. Biodegradation of oil is the process of biological oxidation, similar to thatutilized in municipal sewage treatment plants. There are over 200 natural micro-organisms—bacteria, yeast and fungi—that are able to metabolize hydrocarbons. The organisms require oxy-6-9