The ballast on most ships is usually achieved using water, and the amount of ballast water transferred globally each year is estimated to be 10 billion tonnes (see Wright and Mackey, 2006 and MacPhee, 2006). Ships usually discharge ballast water in INK 128 order ports while loading and take up ballast water in destination ports while unloading, where the water is shallow and rich in aquatic organisms. Taking up non-indigenous species (NIS) in one port and transporting them to another sea can lead to significant environmental problems. Zebra mussels, native to the Caspian Sea region of Asia but transported to the Great Lakes via ballast water, reduce

the amount of phytoplankton available for other organisms and cost $100 M/year to manage control measures (see Pimentel et al., 2000). In order to prevent the transfer of aquatic organisms from one region to another via ballast water, the International Maritime Organization adopted the Ballast Water Management Convention in 2004. According to Ballast Water Exchange Standard, Regulation D-1 of the Convention, ships utilising the exchange method need to exchange ballast water

at least Galunisertib manufacturer 95% by volume; for ships exchanging ballast water by the pumping-through method, pumping through three times the volume of each ballast tank was considered to meet the standard. Pumping through less than three times the volume may be acceptable if the procedure can demonstrate that at least 95% of original ballast water is removed. The original intention of the Ballast Water Convention was that the water exchange technique would be a short-term solution and be replaced by water treatment. When

the Convention was written no ballast water treatment plants were in production. Their development has been slower than expected due to various reasons including an underestimation of the technical challenges, insufficient resources Thalidomide and market economics (see King et al., 2012). The magnitude of the logistical effort required for effective enforcement and regulation of various aspects of the Convention have also been identified as potential barriers to implementation (see Wright, 2012). These are some of the reasons that the Convention is still not ratified even though some of its initial deadlines for implementation have already passed. The situation is complex but the outcome is that ballast water exchange is still in widespread use and will continue to be so for quite some time. Moreover some authorities are now insisting on a combination of ballast water exchange and treatment. It is also becoming clear that a much more detailed understanding of the flow behaviour within ballast tanks is required for compliance assessment and enforcement once ballast water treatment is introduced.