Petroleum products, with a high concentration of polar compounds, which undergo agitation in the presence of water (natural wave action, travelling through a skimmer pump...) form reverse emulsions by incorporating droplets of water in the oil phase. These emulsions can contain up to 80% water and are sticky, viscous masses, brown to dark brown in colour, which explains why they are often known as "chocolate mousse".
The formation of reverse emulsions, along with the evaporation of the lighter fractions, strongly influences the viscosity of an oil pollutant during weathering at sea. The viscosity of the crude oil from the Amoco Cadiz multiplied by 200 due to the formation of an emulsion containing 75% water. Emulsification significantly increases the volume of pollution and thus complicates operations. The incorporation of 75% of water in the Amoco Cadiz oil meant that the volume of pollution was muliplied by four.
Treating reverse emulsions with an emulsion breaker separates the oil from the water and the debris trapped in the emulsion, making pumping operations and the transfer of the pollutant considerably easier. After settling, the volume of oil to be eliminated may be significantly reduced and the settling water is released into the environment.
Only one efficiency test currently exists for these products and this test requires improvement. It measures the settling time of a typical emulsion. There are also some toxicity test results for the settled water after treatment. A test procedure must be designed based on these two criteria of accurate methodologies.