Mitsui O.S.K. Lines completed initial tests of technology to purify the seawater being pumped into a vesselís ballast tank, using an exclusive filter that offers safe and efficient removal of marine organisms. When a vessel sails without cargo, it must take on seawater as ballast to ensure stability and safe navigation. For example, a 170,000 ton bulk carrier will take on about 50,000 tons of ballast water when there is no cargo on board. The ballast water is then discharged at ports where the cargo is loaded in a volume proportional to the on-loaded cargo.
In the Mitsuiís system, incoming ballast water is filtered thus removing most aquatic organisms before the water enters the ballast tanks. This new cleaning method uses both back-flushing and high-pressure jets to remove foreign matter from clogged filters with no chemicals used, which makes the process environment-friendly. Large filters are adequate for various types of vessels, including VLCCs.
International Maritime Organization (IMO) estimates say some 12 billion tons of ballast water is moved around the world annually. Aquatic organisms moved from one area to another in ballast water might infest the new area, affect its ecological systems, and destroy the marine environment, and adversely affect economic activities such as commercial fishing. This makes ballast water an international environmental issue.