Ships and cargoes – guidance

Control and management of ballast water

How to manage ballast water in shipping including exchange and treatment, plans and systems, and management requirements for specific regions.


Loading and discharge of ballast water is an essential part of a ship’s operation, and is fundamental to maintaining safe operations under different conditions of load.

However, large vessels require thousands of tonnes of water to ensure stability and manoeuvrability, and the environmental impacts of this can be considerable. These impacts result from the fact that the ballast water can contain hundreds of different species, many of which can have serious ecological, economic and public health effects if transferred to regions where they are not native. The recognition of these effects has made ballast management increasingly important for protection of the marine environment.

This guide explains the need to control and manage ballast water. It also includes information on ballast water exchange and treatment, ballast water management plans and systems, and management requirements for specific regions.

Control and manage ballast water and sediments

The ballast water that ships require to maintain stability and ensure manoeuvrability contains microscopic organisms. Most will not survive the voyage, but those which do may establish themselves in a new environment. As non-native species these can have a severe impact on local ecology, economy and public health.

The International Maritime Organization (IMO) has developed a Convention aimed at preventing these harmful effects, adopting the International Convention for the Control and Management of Ships’ Ballast Water and Sediments (the Ballast Water Management Convention) in 2004. This convention provides a structure to address the issues of ballast water and provides two performance standards for the discharge of ballast water - D1 and D2.

The D1 standard is for ballast water exchange, and specifies the volume of water to be replaced.

The D2 standard covers approved ballast water treatment systems, and specifies levels of viable organisms left in water after treatment.

The Convention will come into force at different times, depending on ballast-tank capacity and date of vessel construction. At the present time, the Convention is not in force.

Other guidelines issued in relation to the Convention include procedures for:

  • ships to carry a ballast water management plan
  • recording and reporting of ballast management
  • minimising uptake of organisms, removing of sediment and avoiding unnecessary discharge

Guidelines for ballast water exchange

Ballast water exchange involves replacing water taken in port or near the coast at the start of a voyage with water taken up from open ocean areas. This reduces the risk of introducing species as deep ocean water tends to contain fewer organisms and these generally have more difficulty surviving in coastal and port environments when discharged.

The D1 standard developed by the IMO, as part of the Ballast Water Management Convention, specifies that you must replace at least 95 per cent of the water. If the exchange involves pump-through of ballast tanks, at least three times the volume should be pumped through each tank.

As safe and effective ballast water exchange at sea depends on weather and sea conditions, an exchange may not always be possible. In addition, there is likely to be a residue of organisms in the water, and these can still cause issues if you discharge closer to land - particularly if tanks are allowed to extensively silt up.

At no time when undertaking ballast water exchange should the stability of the vessel be impaired.

Guidelines for ballast water treatment

Ballast-water exchange at sea is not considered an ideal method of ballast-water management, and considerable efforts are being made to develop treatment methods. These methods must be in accordance with Standard D-2 of the IMO’s Ballast Water Management Convention.

Standard D2 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, Standard D2 specifies that your discharge of the indicator microbes shall not exceed specified concentrations as follows:

  • 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

These are the indicator microbes, as a human health standard, but they are not limited to these types.

Options being considered for ballast-water treatment include:

  • mechanical filtration and separation
  • treatment methods such as sterilisation
  • chemical treatment
  • a combination of these methods

Research is still being conducted into these methods, although it is agreed that any treatment must be safe, environmentally acceptable, cost-effective and must work.

Create a ballast water management plan

The IMO has developed guidelines for control and management of ships’ ballast water, which operate alongside the international Ballast Water Management Convention. Although compliance with the guidelines is not legally required at this time, UK-registered ships are encouraged to follow them.

Your ships should carry and implement a ballast water management plan, detailing safety procedures for your ship and crew. The plan must provide a detailed description of the actions to be taken to implement the ballast water management requirements.

The ballast water management plan must be approved by a recognised Classification Society, and must include safety procedures for the ship and crew. It must also have a detailed description of actions to be taken to implement the ballast water management requirements.

Your ships should also carry a Ballast Water Record Book, which must be completed after each ballast water operation.

Ballast water management plans are required for ships taking on or discharging ballast water in some ocean sectors.

Ballast water management requirements in specific areas

In addition to the IMO’s Ballast Water Management Convention, specific areas of the oceans have additional requirements for ballast water control, which you must adhere to.

Antarctic waters

There are specific requirements for the uptake or discharge of ballast water in Arctic or Antarctic waters. You must follow these unless the safety of the ship is jeopardised by a ballast exchange, or where it is necessary for saving life at sea.

A ballast water management plan is to be prepared for vessels entering Antarctic waters, taking into account problems of ballast water exchange in Antarctic conditions. Your vessels should keep a record of ballast water operations.

Ballast water should first be exchanged before arrival in Antarctic waters or at least 50 nautical miles from the nearest land in waters at least 200 metres deep. Similarly, ballast water taken on in Antarctic waters should be exchanged north of the Antarctic Polar Frontal Zone, and at least 200 nautical miles from the nearest land in water at least 200 metres deep.

The release of sediments during the cleaning of ballast tanks should not take place in Antarctic waters. Vessels that have spent significant time in the Arctic should discharge and clean tanks before entering Antarctic waters. If this is not possible, sediment accumulation in ballast tanks should be monitored and sediment disposed of in accordance with the ship’s ballast water management plan.

Washington State waters

Some United States territorial waters also have regulations controlling ballast water management. If your commercial vessel is over 300 gross tonnes it is not permitted to discharge ballast water in Washington State waters without previously having undergone open ocean exchange or some approved form of treatment.

Brazilian waters

Vessels entering Brazilian waters must carry a ballast water management plan.

Further information

Download Marine Guidance Note (MGN) 363 (M+F) The Control and Management of Ships’ Ballast Water and Sediments

Download MGN 81 (M+F) Guidelines for the Control and Management of Ships’ Ballast Water to Minimize the Transfer of Harmful Aquatic Organisms and Pathogens

Global Ballast Water Management Programme information on the GloBallast website

Download Marine Information Note (MIN) 283 Practical Guidelines for Ballast Water Exchange in the Antarctic Treaty Area from the MCA website (PDF, 275KB)

Download MIN 282 Ballast Water Legislation Update: Brazil & US (Washington State) from the MCA website (PDF, 274KB)