The water that collects in the bilges of a vessel which generally becomes foul and noxious. Bilge water also contains fluids from machinery spaces, internal drainage systems, sludge tanks and various other sources. This mixture is collected in the bilge water holding tank, which generally is maintained at an elevated temperature. Regardless of its source bilge water must be treated to reduce the oil content to levels meeting international regulations for release into the environment.
Note: Cleaning agents, emulsifiers, solvents or surfactants used for cleaning purposes may cause the bilge water to emulsify. Proper measures should be taken to minimize the presence of these substances in the bilges of a ship.