Different terms are used when dealing with this topic: Wastewater, sewage, black water, grey water. Here you can find out what is meant and what it is all about!


“Wastewater” is to be understood as a generic term and can refer to black and grey water together or separately, depending on the context. The term “wastewater” is also used synonymously with the term “sewage”. While “wastewater” is the most commonly used term, it is less selective than e.g. “Sewage”.


“Sewage” is the term used, for example, by the IMO (International Maritime Organization) or in the MARPOL Convention (International Convention for the Prevention of Pollution from Ships; “MARine POLution”) when dealing with the subject. “Sewage” is defined in MARPOL Annex IV as follows:

“3. Sewage means:

    1. drainage and other wastes from any form of toilets and urinals;
    2. drainage from medical premises (dispensary, sick bay, etc.) via wash basins, wash tubs and scuppers located in such premises;
    3. drainage from spaces containing living animals; or
    4. other waste waters when mixed with the drainages defined above.”


The term black water is not officially used by the regulatory authorities and is therefore not clearly defined. In general, the term black water is used to mean “Sewage” as defined in Annex IV of the MARPOL Convention.


Grey water is defined in IMO (International Maritime Organization) resolution MEPC.227(64) as follows:

“2.7 Grey water – is drainage from dishwater, galley sink, shower, laundry, bath and washbasin drains and does not include drainage from toilets, urinals, hospitals, and animal spaces, as defined in regulation 1.3 of MARPOL Annex IV and does not include drainage from cargo spaces.”


Sludge, also known as sewage sludge, is an unavoidable by-product of wastewater treatment. Wastewater treatment plants generate a stream of treated water, which can be discharged into the sea, and they produce sludge that has to be kept on board in tanks until it can be discharged ashore. Sewage sludge is disposed of in ports with appropriate equipment or by specialised service providers with the help of tankers. An Land, the sewage sludge from ships is disposed of together with the sewage sludge from land-based sewage treatment plants.


Solid garbage is to be considered separately from wastewater. Garbage is defined in MARPOL Annex V as follows:

“1.1 Garbage means all kinds of victual, domestic and operational waste excluding fresh fish and parts thereof, generated during the normal operation of the ship and liable to be disposed of continuously or periodically except those substances which are defined or listed in other Annexes to the present Convention.”

Garbage also includes food waste. Important: If garbage as defined in MARPOL Annex V, e.g. food waste from the galley, is mixed with sewage as defined in MARPOL Annex IV, i.e. mainly from the toilets, the stricter requirements of MARPOL Annex V apply to the treatment of the mixture.

HAMANN sewage treatment plants are exclusively designed for the treatment of sewage according to MARPOL Annex IV and grey water according to IMO resolution MEPC.227(64) and are not suitable for the treatment of garbage according to MARPOL Annex V.