The revised MARPOL Annex IV containing regulations for the prevention of pollution by sewage from ships was formally adopted and is expected to enter into force on 1 August 2005. 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.

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 its entry into force. The Annex requires ships to be equipped with either a sewage treatment plant or 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 and 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.