Methods for Treating Ballast Water

Abstract

A vessel sailing with ballast, or partially loaded, must use its ballast tanks, water currently being the most commonly used medium. An estimate of over 10,000 million tonnes of ballast water is transferred in the entire world each year, transporting 4,000 species of aquatic organisms a day. The most immediate way to confront this problem consists in taking measures on board the vessel through the appropriate treatment of ballast water. Facing the importance of this problem, the International Maritime Organization (I.M.O.) has developed the International Convention for the Control and Management of Ship’s Ballast Water and Sediments (BWM-2004), at the moment pending approval. In summary, the Convention obliges members to the “what” but not to the “how”, recommending the exchange of ballast water by a “reballasting” method, technique which is not 100% effective. For this reason, important research efforts are being carried out throughout the world dedicated to finding a system that is 100% effective. The main methods currently being studied are the mechanical, physical and chemical ones.