Decreasing the amount of oil entering the system is most economically accomplished at the source of the contamination. When the initial treatment of an oil desalination spill at sea includes mechanically skimming the water's surface, a mixture of floating oil, emulsified oil, tar balls, etc. will be taken onto the recovery barge and delivered for reclamation. A large percentage of the water will settle out by gravity. Other processes include centrifuging, desalination, and chemical separation. Heating the oil-water emulsion is not generally recommended when light fuels such as gasoline, jet fuel, kerosene, and other solvents are present and could present a fire hazard, especially aboard ship.
Oily sludge is slow to resolve.
Several weeks of settling may be required. Storage space is tied up because more oily sludge and slop oil is on hand than can be heat treated and resolved or recovered. Recovered oil quality is usually poor and unsuitable for recycling to crude units or desalters. Centrifuging can handle comparatively stable mixtures with heat. However, many emulsions, such as those occurring when an oil spill mixes with seawater, fail to yield to physical methods alone.