Maryam Rasouli - Marine Prevention Of Pollution Expert, Ports and Maritime Organization(PMO),Tehran, Iran

Dispersants are products used in oil spill response to enhance natural microbial degradation, a naturally occurring process where microorganisms remove oil from the environment. All environments contain naturally occurring microbes that feed on and break down crude oil. Dispersants aid the microbial degradation by forming tiny oil droplets, typically less than the size of a period on this page (<100 microns), making them more available for microbial degradation. Wind, current, wave action, or other forms of turbulence help both this process and the rapid dilution of the dispersed oil. The increased surface area of these very small oil droplets in relation to their volume makes the oil much easier for the petroleum- degrading microorganisms to consume. The reason for using dispersants, either on floating oil or by subsea application, is the same: to minimize the overall ecological and socio-economic damage, by preventing the released oil from drifting into near shore or coastal habitats and onto the shore. Dispersant use on floating oil breaks the surface slick into many small oil droplets that are dispersed, rapidly diluted and subsequently biodegraded in the upper layer of the water column. Subsea dispersant use aims to prevent the oil released subsea from reaching the sea surface by dispersing the oil into the water close to the release. This provides a major health and safety benefit by greatly reducing the exposure of personnel responding near the release site to volatile organic compounds (VOCs). Adding dispersant to the released oil and gas subsea causes a greater proportion of the released oil to break into small oil droplets that will be dispersed, diluted and biodegraded in the water column, unlike the larger oil droplets that will float up to the sea surface. The surfactants in the dispersant greatly reduce the oil/water interfacial tension that exists between oil and water and this permits the turbulence associated with a subsea oil and gas release to convert a greater proportion of the released oil into small oil droplets. The potential toxicity of existing chemical dispersants on the marine environment has motivated the search for environmentally friendly dispersants with excellent dispersion ability

Dispersant, Seawater, oil spill, response, biodegradability, marine life