We also rigorously treat the three basic types of wastewater that are produced on cruise ships: bilge water, which is a mixture of liquids, primarily fresh water, that is collected in the engine room from machinery spaces and internal drainage systems; graywater, which is water from showers, baths, washbasins, laundry, dishwashers and galleys; and blackwater, which is water from toilets, urinals and medical facilities.