6.(a) With reference to MARPOL Annex IV, explain what is meant by the term sewage.(4)
(b) State the current regulations for the discharge of sewage.(6)
(a) Definition of Sewage – MARPOL Annex IV (4 marks)
Under MARPOL Annex IV, sewage means:
- Drainage and wastes from toilets, urinals, and water closets.
- Drainage from medical premises (dispensary, sick bay, etc.) via wash basins, wash tubs, and scuppers.
- Drainage from spaces containing living animals.
- Other wastewaters mixed with the above (including some grey water if combined).
(b) Current regulations for the discharge of sewage (6 marks)
- Untreated sewage:
- Discharge only permitted when the ship is en route and 12 nautical miles or more from the nearest land.
- Discharge must be at a moderate rate, not instantaneously.
- Comminuted and disinfected sewage (through an approved system):
- May be discharged when the ship is en route and 3 nautical miles or more from the nearest land.
- Sewage treated in an approved sewage treatment plant:
- May be discharged at any distance from land, provided the effluent meets IMO standards.
- General requirement:
- Discharge must not cause visible floating solids or discolouration of the surrounding water.