95.D1 and D2 standard

hips are required to have on board and implement an approved Ballast Water Management Plan.

Ships must maintain a Ballast Water Record Book to record when ballast water is taken on board, circulated or treated for Ballast Water Management purposes and discharged into the sea. It should also record accidental or other exceptional discharges of ballast water.

The BWM Convention includes two performance standards for the discharge of ballast water: D1 and D2.

The D1 standard concerns ballast water exchange, which must be undertaken within open ocean areas, >200nm from land and in seas >200m deep.


The D2 standard covers approved ballast water treatment systems.

D1 - Ballast water exchange (BWE)

The standard set by the Convention states that ships undertaking BWE shall do so with an efficiency of at least 95% volumetric exchange of ballast water. For ships exchanging the ballast water by the pumping-through method, pumping through three times the volume of each ballast tank will be considered equivalent to meeting the 95% standard.
Ships undertaking ballast water exchange should conduct the operation at least 200 nautical miles from the nearest land and in water at least 200 metres deep; or in cases where the ship is unable to conduct ballast water exchange in accordance with the above, as far from the nearest land as possible, and in all cases at least 50 nautical miles from the nearest land and in water at least 200 metres deep.
In sea areas where the minimum distance and depth criteria cannot be met, the Parties to the Convention have the ability, within their waters, to designate BWE areas. Areas designated by a Party should be used in compliance with the terms of use stipulated by the Administration(s) responsible for the designation. Vessels may be required to deviate or delay their voyage in order to use the designated BWE area.
Owners are urged to contact relevant port State Administrations for confirmation of BWE requirements within local waters.

D2 - Ballast water performance standard

D2 stipulates the acceptable level of organisms that may be found within discharged ballast water. The D2 Standard specifies that treated and discharged ballast water must have:

• fewer than ten viable organisms greater than or equal to 50 micrometers in minimum dimension per cubic metre;
• fewer than ten viable organisms less than 50 micrometres in minimum dimension and greater than or equal to 10 micrometers in minimum dimension per millilitre.

In addition, a ballast water discharge of indicator microbes, as a health standard, shall not exceed the following specified concentrations:

• Toxicogenic Vibrio cholerae (O1 and O139) with less than one colony-forming unit (cfu) per 100 millilitres or less than 1 cfu per 1 gram (wet weight) zooplankton samples;
• Escherichia coli less than 250 cfu per 100 millilitres;
• Intestinal Enterococci less than 100 cfu per 100 millilitres

Ballast water treatment equipment is developed, and type approved on the basis of the equipment’s ability to treat the ballast water to the required standard. Although not the only way to meet the D2 standard, the installation of an appropriately type approved ballast water treatment system will be the most common method used.