Prevention of Pollution by Sewage from Ships

Regulations for the prevention of pollution by sewage are contained in Annex IV of MARPOL 73/78.

Sewage the problem

The discharge of raw sewage into the sea can create a health hazard, while in coastal areas, sewage can also lead to oxygen depletion and an obvious visual pollution - a major problem for countries with large tourist industries.

The main sources of human-produced sewage are land-based - such as municipal sewers or treatment plants.

Annex IV of MARPOL

Annex IV contains a set of regulations regarding the discharge of sewage into the sea, ships' equipment and systems for the control of sewage discharge, the provision of facilities at ports and terminals for the reception of sewage, and requirements for survey and certification. It also includes a model International Sewage Pollution Prevention Certificate to be issued by national shipping administrations to ships under their jurisdiction.

It is generally considered that on the high seas, the oceans are capable of assimilating and dealing with raw sewage through natural bacterial action and therefore the regulations in Annex IV of MARPOL 73/78 prohibit ships from discharging sewage within a specified distance of the nearest land, unless they have in operation an approved treatment plant.

Governments are required to ensure the provision of adequate reception facilities at ports and terminals for the reception of sewage.

The Annex entered into force on 27 September 2003. A revised Annex was adopted on 1 April 2004, with an entry into force date of 1 August 2005.

The revised Annex will apply to new ships engaged in international voyages, of 400 gross tonnage and above or which are certified to carry more than 15 persons. Existing ships will be required to comply with the provisions of the revised Annex IV five years after the date of entry into force of Annex IV, namely from 27 September 2008. The Annex requires ships to be equipped with either a sewage treatment plant or a sewage comminuting and disinfecting system or a sewage holding tank.

The discharge of sewage into the sea will be prohibited, except when the ship has in operation an approved sewage treatment plant or is discharging comminuted and disinfected sewage using an approved system at a distance of more than three nautical miles from the nearest land; or is discharging sewage which is not comminuted or disinfected at a distance of more than 12 nautical miles from the nearest land.

Revised sewage standards

The Marine Environment Protection Committee (MEPC) at its 55th session in October 2006 adopted revised Guidelines on implementation of effluent standards and performance tests for sewage treatment plants. The revised guidelines, which will apply to sewage treatment plants installed onboard on or after 1 January 2010, replace the Recommendation on international effluent standards and guidelines for performance tests for sewage treatment plants adopted by resolution MEPC.2(VI) in 1976.

The MEPC also adopted a standard for the maximum rate of discharge of untreated sewage from holding tanks when at a distance equal or greater than 12 nautical miles from the nearest land.