NEW DISPERSANT DELIVERED AS A GEL

Abstract

ABSTRACT Recent research has led to a next-generation dispersant that potentially provides significant improvements for all spill scenarios where dispersants are an option in addition to extending dispersant use to oils previously considered too viscous. The new dispersant is formulated as a positively buoyant viscous gel with the consistency of honey. This allows delivery as a spray of large (up to 0.5 cm) droplets that are persistent in breaking-wave conditions and adhere to an oil slick rather than being washed off as do many commercial dispersants. The new formulation is roughly 90% active ingredient while currently available dispersants are at most 40–50% active ingredient with the remainder being a solvent. Wave-basin tests indicate that the increases in dispersant viscosity and active ingredient content allow the new dispersant to treat conventional oils with very low dispersant-to-oil ratios (as low as 1:100 or lower) and disperse oils currently considered too viscous. The new formulation dispersed heavy California crude oils and heavy fuel oil collected after the Prestige spill significantly better than a commercial dispersant in wave-basin and lab tests. Responders did not attempt to use dispersants on the Prestige spill because they considered the oil too viscous. The new dispersant also includes advances not readily evaluated in basin tests. It is a white gel-like material that visually contrasts with oil allowing response personnel to immediately evaluate slick coverage after application. Application as buoyant, pea-size droplets can reduce spray drift and increase delivery accuracy. The large, persistent, and buoyant droplets allow the new dispersant to penetrate slicks after initial contact or even miss the slick altogether but remain intact and floating near the oil allowing re-contact with the slick. Aircrafts apply most conventional dispersants as small 300–700 µm droplets. The conventional-dispersant spray is not visible after application, and the small droplets are susceptible to spray drift in turbulent wind conditions. The advances provided by the new dispersant - those shown by basin tests and the expected field application improvements - may more than triple the capacity of a single plane load of dispersant, and disperse oils currently considered too viscous either because of naturally high viscosity, weathering, emulsification, or cold temperatures.