Abstract
Biodegradation of oil in the marine water column is mainly associated with oil dispersions. The operational use of chemical dispersants may therefore enhance oil biodegradation in seawater. The dispersant treatment results in oil droplet size reductions, increasing the surface-to-oil ratio of the oil. Several laboratory systems have been developed for testing of oil dispersions. The protocol presented here describes a system for generating oil dispersions with small droplets (10–30 μm) and maintaining the dispersions during biodegradation experiments. The dispersions are generated in a system consisting of a series of nozzles. The system is designed to generate accurately controlled oil concentrations and droplet sizes. The dispersions are transferred to a carousel system for incubation with slow continuous rotation around the carousel axis. This carousel system has been developed for keeping the oil droplets in suspension due to the combined effect of turbulence created in the flasks and the fact that the rising velocity of the oil droplets will make them constantly change direction in relation to any fixed point at the flasks inner surface. Biodegradation is determined by quantification of selected oil compounds and by microbiological analyses during the biodegradation period. Results from these studies have been used as input data in dynamic environmental models as part of fate predictions after oil spill and for describing successions of microbial communities related to the biodegradation of different groups of oil compounds.