Port state control officers are inspecting sewage treatment onboard ships calling Dutch ports. First results claim that a vast majority of installations is not meeting the required performance standards. As a result, the Dutch delegation will pass the results of the sampling campaign to IMO level.

Sewage, the problem

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

The main sources of human-produced sewage are land-based, such as municipal sewers or treatment plants. However, the discharge of sewage from ships into sea contributes to marine pollution.

Annex IV of MARPOL

Annex IV contains regulations on discharge of sewage from ships into the sea, on ships' equipment and systems for sewage discharge control, on the provision of port reception facilities for sewage, and includes requirements for survey and certification. It came into force on September 27, 2003 and revised on April 1, 2004, which took effect on August 1, 2005. The revised Annex applies to new ships engaged in international journeys of more than 400 gross tonnage or certified to carry more than 15 people. Existing ships are required to comply with the provisions of the revised Annex IV five years after the date of entry into force of Annex IV, being September 27, 2008.

Governments are required to ensure the provision of adequate reception facilities at ports and terminals for the reception of sewage, without causing delay to ships.

It is generally stated that on the high seas, oceans are capable of assimilating and dealing with raw sewage through natural bacterial action. Regulations of MARPOL Annex IV deal with prohibiting sewage discharge into sea within a specified distance from the nearest land, unless otherwise provided.

The discharge of sewage into sea is prohibited, except when the ship is equipped with a sewage holding tank, or it has an approved sewage treatment plant in operation, or when the ship is discharging comminuted and disinfected sewage using an approved system at a distance of more than three nautical miles from the nearest land. Sewage which is not comminuted or disinfected may be discharged at a distance of more than 12 nautical miles from the nearest land, and the maximum standard rate of discharge of untreated sewage approved by the Administration (resolution MEPC.157(55)).

Special area

In July 2011, MEPC 62 adopted, by resolution MEPC.200(62), the most recent amendments to MARPOL Annex IV, which entered into force on January 1, 2013. The amendment introduces the Baltic Sea as a special area under Annex IV and adds new discharge requirements for passenger ships while in this special area. The date on which the requirements regarding this special area will be effective, depends on sufficient notifications to IMO from the parties bordering the Baltic Sea and on the availability of reception facilities for sewage.​​

The amendment states that discharge of sewage from passenger ships within this special area are prohibited, except when the ship has an approved sewage treatment plant certified by the Administration (see resolution MEPC.227(64)) in operation. The sewage treatment plant installed on a passenger ship intending to discharge sewage effluent in special areas should additionally meet the nitrogen and phosphorus removal standard when tested for its Certificate of Type Approval by the Administration (resolution MEPC.227(64)​, section 4.2).


The inspection by Port State Control officers in the Netherlands, shows that test results obtained in laboratories of marine equipment, are not always met in real live conditions. This was already experienced for the first generation of ballast water systems; but it seems that also the operation of a good functioning sewage treatment systems is a ‘challenge’.