Relevant documents and M-notices: MARPOL Annex IV, MGN 631, RESOLUTION MEPC.157(55)
What is sewage? From MARPOL Annex IV Reg. 1:
Sewage means:
drainage and other wastes from any form of toilets and urinals
drainage from medical premises (dispensary, sick bay, etc.) via wash basins, wash tubs and scuppers located in such premises
drainage from spaces containing living animals
other waste waters when mixed with the drainages defined above.
Grey water - water from washbasins, showers etc. - isn’t considered sewage unless it is mixed with water from toilets etc.
Where is Annex IV made into UK law?
The Merchant Shipping (Prevention of Pollution by Sewage from Ships) Regulations 2020. These regulations apply to UK ships wherever they may be, and non-UK ships while in UK waters (henceforth all regulations referred to will be from this legislation).
Who does the requirements apply to?
All vessels over 400GT, or certified to carry more than 15 persons.
Certification
International Sewage Pollution Prevention Certificate
Known as the ‘Sewage Certificate’, this is issued after an initial survey and is valid for 5 years, at which point it is subject to a renewal survey. A UK ship may not proceed to sea, or remain at sea, if she does not have a valid ISPPC. The survey looks at the sewage treatment plant, the holding tank, the discharge pipeline and connection and the comminuting system. This certificate can be issued by flag or by a Recognised Organisation (class society).
The ISPPC will contain descriptions of the sewage treatment plant, comminuter/sanitzer or holding tank.
Equipment
Sewage treatment plant
As per Regulation 8, ships must have a type-approved sewage treatment plant. These are generally approved by a Recognised Organisation but may be approved by Flag.
Sewage discharge pipeline
As per Regulation 9, this must be fitted with a standard discharge connection.
Discharge
See Regulation 7 of the MS (Prevention of Pollution by Sewage from Ships) Regulations 2020, and Regulation 11 of MARPOL .
Before sewage can be discharged, one of three requirements must be met:
For a ship outside a special area it is permitted to discharge comminuted and disinfected sewage at least 3 NM from the nearest land, or sewage which is not comminuted and disinfected at least 12 NM from the nearest land. In either case, the sewage should be discharged at a moderate rate when the ship is en route and proceeding at not less than 4 knots. The moderate rate is set by Flag (as per MGN 631, the MCA considers this rate to be no greater than that set out in the table below, taken from MEPC 157(55)):
For a passenger ship inside a special area, discharge is permitted when she has a functioning, type approved sewage treatment plant and no discolouration of the water is caused, with no floating solids.
For a UK ship in polar waters, discharge is permitted if sewage is comminuted and disinfected, more than 3 NM from land or an ice-shelf or fast ice, and as far as practicable from ice concentrations of 1/10 or more. If sewage is not comminuted and disinfected she must be at least 12 NM from any ice-shelf or fast ice and be as far as practicable from ice concentration of 1/10 or more. If she has an approved sewage treatment plant she may discharge sewage provided she is as far as practicable from the nearest land, ice-shelf, fast ice or areas of ice concentration exceeding 1/10.
Other than in the above cases, discharge is permitted only for safety of life or the vessel, or when it is the result of an accident or damage when all reasonable precautions were taken to prevent this and to minimise the discharge (Regulation 7b)
Special areas
The Baltic Sea is the only special area under MARPOL Annex IV. This only applies to passenger vessels.
However, the Polar Code does have some additional requirements for vessels operating in Polar areas. See the Polar Code Part II-A, Chapter 4. This makes the Arctic and Antarctic de facto special areas, though under the Polar Code.
MCAQs
What are the special areas under Annex IV?
What about the Arctic and Antarctic?
How would you find what the MCA deems an acceptable rate of discharge of sewage?
When may a passenger ship discharge sewage in a special area?