Prevention of Pollution by Sewage from Ships: MARPOL Annex IV

MARPOL Annex IV regulates the discharge of sewage from ships to prevent marine pollution. It applies to ships of 400 gross tonnage and above, or those carrying more than 15 passengers. The annex prohibits the discharge of untreated sewage within 12 nautical miles from the nearest land, unless the ship uses an approved sewage treatment plant that meets specific effluent standards. In special areas, stricter rules apply, and discharge is only allowed if the sewage is treated to meet the required standards. Ships must also be equipped with either a holding tank for sewage storage and delivery to port reception facilities or a treatment system. Compliance ensures the protection of marine ecosystems and human health.

Sewage – the problem

The discharge of raw sewage into the sea can create a health hazard. Sewage can also lead to oxygen depletion and can be an obvious visual pollution in coastal areas – 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 into the sea from ships also contributes to marine pollution.

Annex IV of MARPOL

Annex IV contains a set of regulations regarding the discharge of sewage into the sea from ships, including regulations regarding the ships’ equipment and systems for the control of sewage discharge, the provision of port reception facilities for sewage, and requirements for survey and certification. It is generally considered that on the high seas, the oceans are capable of assimilating and dealing with raw sewage through natural bacterial action. Therefore, the regulations in Annex IV of MARPOL prohibit the discharge of sewage into the sea within a specified distance from the nearest land, unless otherwise provided. 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.

Summary of Sewage Solutions for Ships (MARPOL Annex IV):

1. Holding Tank and Delivery to Port:

   • Store sewage in a holding tank.
   • Discharge sewage to port reception facilities.

2. Sewage Treatment Plant:

   • Use an approved sewage treatment plant.
   • Treat sewage to meet effluent standards (e.g., ≤ 100 fecal coliforms/100 mL, ≤ 50 mg/L suspended solids).
   • Discharge treated sewage anywhere, including in special areas, if compliant.

3. Sewage Comminuting and Disinfecting:

   • Use a comminuter (grinder) and disinfection system.
   • Discharge comminuted and disinfected sewage ≥ 3 nautical miles from shore.

4. Sewage Discharge Overboard (Untreated):

   • Discharge untreated sewage only ≥ 12 nautical miles from shore.
   • Must be en route and at a moderate speed.

Key Rules:

• Special Areas: Stricter rules; treated sewage discharge allowed if compliant.
• Record Keeping: Log discharges in the Garbage Record Book if required.

Sewage treatment plants for ships , source: https://www.wartsila.com/waw/waste-treatment/wastewater/sewage-treatment-plants

Special Areas under MARPOL Annex IV

The Baltic Sea is currently the only Special Area designated under MARPOL Annex IV, with stricter sewage discharge rules. Amendments adopted in 2011 (MEPC.200(62)) and updated in 2017 (MEPC.275(69)) prohibit sewage discharge from passenger ships in Special Areas unless they use an approved sewage treatment plant certified by the Administration. These plants must meet advanced standards, including nitrogen and phosphorus removal (MEPC.227(64)).

The phased implementation of these rules began:

• 1 June 2019: New passenger ships.
• 1 June 2021: Existing passenger ships.
• 1 June 2023: Existing passenger ships en route directly to/from ports outside or east of 28˚10′ E in the Baltic Sea without additional port calls.

These measures aim to protect sensitive marine environments like the Baltic Sea.

Update on Sewage Sludge Dumping Ban

Parties to the London Protocol have adopted an amendment to prohibit the dumping of sewage sludge at sea worldwide. The amendment, adopted at the IMO meeting (3-7 October 2022), removes sewage sludge from the list of permissible wastes under Annex 1 of the Protocol.

Key Points:

• Sewage sludge dumping, once common, has declined significantly due to regional bans and better waste management alternatives.
• The amendment takes effect 100 days after adoption or upon acceptance by Contracting Parties.
• The London Protocol uses a “reverse list” approach: all dumping is banned unless explicitly permitted. Permitted wastes now include dredged material, fish waste, inert geological material, and CO2 streams from carbon capture.

Background:

• The London Convention (1972) and Protocol (2006) aim to prevent marine pollution by regulating waste dumping.
• The Protocol, with 53 Parties, is stricter, applying a precautionary approach.

This amendment marks a significant step in protecting marine ecosystems.

Reference: IMO