With ballast water in ships, marine organisms are transported around the globe and to environments on which they may have adverse effects (e.g. displacement or even elimination of indigenous species). In order to prevent this world-wide distribution, the International Maritime Organisation (IMO) approved the ‘International Convention for the Control and Management of Ships' ballast water and sediments’ (Ballast Water Convention) in 2004. This convention aims at a management of ballast water to avoid the transfer of organisms around the world. Consequently, a variety of technologies have been developed to remove living organisms from ballast water before it is discharged into the environment. Subsequently, any toxic substance that has served as biocide in the process or was formed during the treatment will be released to the environment when the large amounts of ballast water are discharged. Hence, before ballast water treatment measures are approved by the competent authorities, an assessment of the potential  isk for the environment needs to be carried out.