Black water

Black water is sewage as defined by MARPOL Annex IV: drainage from toilets and urinals, drainage from medical spaces, drainage from spaces holding live animals, and other waste water mixed with these. It is distinct from gray water (galley, shower, and laundry drainage), which Annex IV does not regulate. Annex IV applies to ships of 400 GT and above and smaller ships certified to carry more than 15 persons on international voyages. Discharge of untreated sewage is barred within 12 nautical miles of the nearest land, comminuted and disinfected sewage within 3 miles, and an approved treatment plant allows discharge subject to the effluent standard. Compliant ships hold an International Sewage Pollution Prevention Certificate.