The UK Maritime & Coast Guard Agency (MCA) has issued a Marine Guidance Note on the control and management of ships' ballast water and sediments. MGN 363 draws attention to the developments at the International Maritime Organization (IMO) with respect to non-indigenous species being transported in ships' ballast water. The main points of the notice are outlined below.

The International Maritime Organization (IMO) through its Marine Environment Protection Committee (MEPC) has, over many years, been developing international legislation to prevent the harmful effects of transporting aquatic organisms in ships ballast water.

Over 9-13 February 2004 a Diplomatic Conference was held to adopt the "International Convention for the Control and Management of Ships' Ballast Water and Sediments". The Ballast Water Management (BWM) Convention puts in place international legislation for the first time and will enter into force 12 months (with a first application date of 2009) after it has been signed by 30 States, representing 35% of world merchant shipping tonnage.

To date, thirteen Member States have ratified the convention. Member States have been urged to ratify the instrument to facilitate its timely entry into force. The UK is intending to begin the process of ratifying the Convention as soon as it has been proved that technology is available to meet the water quality standards under Regulation D-2.

The Convention provides two ballast water discharge performance standards for the industry - the first providing a standard for ballast water exchange and the second based on ballast water treatment. These are set out below:

• D1 Standard - Ballast Water Exchange (at least 95% volumetric exchange) or if using the pump though method - pumping through three times the volume of each tank.
• D2 Standard - Ballast Water Treatment systems approved by the Administration which treat ballast water to an efficacy of:
  • Less than 10 viable organisms per m3 >50 micrometres (one millionth of a meter) in minimum dimension, and
  • Less than 10 viable organisms per millilitre < 50 micrometres in minimum dimension and >10 micrometers in minimum dimension.

Indicator Microbe concentrations shall not exceed: a) toxicogenic vibrio cholerae: 1 colony forming unit (cfu) per 100 millilitre or 1 cfu per gram of zooplankton samples; b) Escherichia coli: 250 cfu per 100 millilitre c) Intestinal Enterococci: 100 cfu per 100 millilitre.

These then apply to different vessels at different times as set out in the table below, depending on the ratification date of the Convention.