DISPERSION AND BIODEGRADATION OF OIL SPILLS ON WATER

Abstract

ABSTRACT Published literature indicates that oil spill dispersion by chemical dispersants will enhance biodegradation because of the increase in interfacial area. However, some of the literature is contradictory concerning whether the use of surfactants will enhance or temporarily inhibit biodegradation, suggesting that more than one mechanism is at work. We set out to study the correlation between the area of dispersed oil droplets and the rate and extent of microbial oil degradation using sorbitan surfactants. We varied the surfactant blend hydrophile-lipophile balance (HLB) and treat level in a statistically designed experiment. Both dispersed area and percent oil degraded at a given time were shown to depend on surfactant HLB and treat level, but to different degrees. The difference was accounted for by demonstrating that percent oil degraded depended on both dispersed area and percent sorbitan in the dispersant treat. The quantitative finding that both dispersed area and surfactant chemistry control microbial growth and oil biodegradation explains the apparent contradiction that some good dispersants enhance, while others temporarily inhibit, degradation. Corexit 9500 dispersant was observed to have a positive influence on biodegradation of oil on water.