Overview of the 2004 Ballast Convention

Updated 11 Oct 2019


Using water as ballast for empty or part-laden ships is not a new development having been in use for more than 200 years. Ballast is not just used to adjust draught but also to help trim to enable safe and efficient operation of ships under a variety of conditions including cargo shift and water ingress. Few of those that were innovative enough to make use of water instead of solid ballast could have thought that their idea was later to be considered as ecologically unsound.

It was not until the 1982 UN Convention on the Law of the Sea (UNCLOS) that control of species transfer became a topic of international concern. Some ten years later, the 1992 United Nations Conference on Environment and Development (UNCED) requested the International Maritime Organization (IMO) to consider the adoption of appropriate rules on ballast water discharge.

The ballast water treatment convention was to be a further 12 years under discussion before its final Adoption in February 2004. Adoption did not mean that the convention automatically came into force; for that to happen there needed to be ratification by at least 30 states representing 35% of the world merchant shipping fleet by gross tonnage.

The first trigger point was reached some years ago, but the 35% fleet figure was only achieved on 7 September 2017 when Finland ratified.

Several nations have not so far ratified the convention and neither has the US although it has introduced its own federal regulation very similar to that of the IMO Convention. The US regulation has meant that the potential for individual states in the union introducing their own local laws has been averted but all vessels intending to trade to the US will now have to fit a treatment system.

Although it is generally accepted that the requirements of the convention will become standard practice, parties to it are given the right to take, individually or jointly with others ‘more stringent measures with respect to the prevention, reduction or elimination of the transfer of harmful aquatic organisms and pathogens through the control and management of ships’ ballast water and sediments, consistent with international law’. However, this has been tempered by adding a clause saying that ‘Parties should ensure that ballast water management practices do not cause greater harm than they prevent to their environment, human health, property or resources, or those of other States’.

The structure of the convention includes 22 Articles that govern the operation of the convention, a number of regulations spread over five categories and a set of 14 guidelines each covering a different topic.

The five areas of regulations are:

  • Section A – General provisions
  • Section B – Management and control requirements for ships
  • Section C – Special requirements in certain areas
  • Section D – Standards for ballast water management
  • Section E – Survey and certification requirements for ballast water management

The list of guidelines and the topics covered are:

  • G1. Guidelines for sediment reception facilities
  • G2. Guidelines for ballast water sampling
  • G3. Guidelines for ballast water management equivalent compliance
  • G4. Guidelines for ballast water management and development of ballast water management plans
  • G5. Guidelines for ballast water reception facilities
  • G6. Guidelines for ballast water exchange
  • G7. Guidelines for risk assessment under regulation a-4 of the convention
  • G8. Guidelines for approval of ballast water management systems
  • G9. Procedure for approval of ballast water management systems that make use of active substances
  • G10. Guidelines for approval and oversight of prototype ballast water treatment technology programmes
  • G11. Guidelines for ballast water exchange design and construction standards
  • G12. 2012 guidelines on design and construction to facilitate sediment control on ships
  • G13. Guidelines for additional measures regarding ballast water management including emergency situations
  • G14. Guidelines on designation of areas for ballast water exchange

The Convention — which applies to all vessels which carry ballast water — allows for two means of meeting the requirements and these are contained in Section D – Standards of Ballast Water Management. The methods are Ballast Water Exchange (Regulation D-1) or Ballast Water Management (Regulation D-2); with the latter requiring some form of treatment system. The convention has detailed requirements for both methods.

Regulation D-1 Ballast Water Exchange Standard

Ships performing Ballast Water exchange shall do so with an efficiency of 95% volumetric exchange of Ballast Water. For ships exchanging ballast water by the pumping-through method, pumping through three times the volume of each ballast water tank shall be considered to meet the standard described. Pumping through less than three times the volume may be accepted provided the ship can demonstrate that at least 95% volumetric exchange is met.

The D-1 Ballast Water Exchange method was conceived as an interim measure that would be allowed only to existing ships with ballast capacities up to and including 5,000m3 built before 2009 and for vessels with ballast capacities over 5,000m3 built before 2012. Those ships allowed to perform ballast exchange as a means of compliance would be permitted to do so only for a limited period depending upon construction date and ballast capacity.

By 2017 the permission was supposed to expire for all vessels and only ballast water management would be permitted. Delay in the ratification of the convention means these dates are no longer valid and some ships can now continue with ballast exchange until 2022.

Under Regulation B-4 (Ballast Water Exchange) of the convention, all ships using ballast water exchange should whenever possible, conduct ballast water exchange at least 200 nautical miles from the nearest land and in water at least 200 metres in depth, taking into account the Guidelines developed by IMO. In cases where the ship is unable to conduct ballast water exchange as above, then it should be 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 in depth. When these requirements cannot be met, areas may be designated where ships can conduct ballast water exchange. All ships shall remove and dispose of sediments from spaces designated to carry ballast water in accordance with the provisions of the ships’ ballast water management plan (Regulation B-4).

As well as being contained in the convention, ballast water exchange has also been made mandatory under local regulations in many parts of the world as governments saw it as an interim way of tackling the issue of invasive species and disease control. Reasons why ballast water exchange was considered only a temporary measure include doubts as to its effectiveness in removing all viable organisms from ships’ ballast tanks and also concerns

over safety. The latter reason was starkly highlighted in July 2006 when the car carrier Cougar Ace almost capsized following a problem during ballast exchange. Salvage of the vessel was eventually achieved but only after the tragic death of one of the salvage surveyors. Several other less serious incidents have also been reported over time.

Regulation D-2 Ballast Water Performance Standard

Ships conducting ballast water management shall discharge less than 10 viable organisms per cubic metre greater than or equal to 50 micrometres in minimum dimension and less than 10 viable organisms per millilitre less than 50 micrometres in minimum dimension and greater than or equal to 10 micrometres in minimum dimension; and discharge of the indicator microbes shall not exceed the specified concentrations. The indicator microbes, as a human health standard, include, but are not limited to:

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

This is the standard that all treatment systems have to meet to obtain type-approval under IMO rules. It is also the standard that the US regulations currently require although, the US rules also contain provision for an even stricter future standard.

Exemptions available under convention

Because the aim of the convention is to prevent species transfer it is clear that for ships which operate only in restricted areas, the need for ballast management does not exist as the same species will be present throughout the area in any case. Regulation A-4 of the BWM Convention recognises this fact and permits any single port state or groupings of port states to permit exemptions. There are restrictions contained within the regulation as detailed


1. A Party or Parties, in waters under their jurisdiction, may grant exemptions to any requirements to apply regulations B-3 or C-1, in addition to those exemptions contained elsewhere in this Convention, but only when they are:

• granted to a ship or ships on a voyage or voyages between specified ports or locations or to a ship which operates exclusively between specified ports or locations;

• effective for a period of no more than five-years subject to intermediate review;

• granted to ships that do not mix Ballast Water or Sediments other than between the ports or locations specified in paragraph 1.1; and

• granted based on the Guidelines on risk assessment developed by the Organization.

2. Exemptions granted pursuant to paragraph 1 shall not be effective until after communication to the Organization and circulation of relevant information to the Parties.

3. Any exemptions granted under this regulation shall not impair or damage the environment, human health, property or resources of adjacent or other States. Any State that the Party determines may be adversely affected shall be consulted, with a view to resolving any identified concerns.

4. Any exemptions granted under this regulation shall be recorded in the Ballast Water record book.

As at March 2017, no regional exemption arrangements are in place. There are however discussions between some states in the Baltic and also in South East Asia that could result in common risk zones being established in the very near future.

A further possible exemption is available to ships if they discharge ballast water to reception facilities approved under the G5 guideline. This is an option that has been promoted by numerous parties and there are projects being developed in India and the Netherlands involving treatment systems installed in barges or ballast boats or even containerised systems placed on shore at terminals.

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