Novel ballast water heating technique offers cost-effective treatment to reduce the risk of global transport of harmful marine organisms

Ten billion tonnes of shipping ballast water are carried around the world a nnually. This provides an inadvertant mechanism for the transfer and disper sal of harmful bacteria, toxic dinoflagellates, seaweeds, molluscs, starfis h, crabs and fish (Rigby & Hallegraeff 1996). Establishment of nonindigenou s and harmful organisms have resulted in significant ecological and environ mental damage and also pose a threat to human health through Paralytic Shel lfish Poisoning, and possibly even Cholera outbreaks (McCarthy & Khambaty 1 994). As a result of these concerns, the International Maritime Organisatio n has recognised skipping ballast water as an international pollutant of ma jor consequence and is currently developing a set of draft regulations for potential use in future international shipping operations. These guidelines will require ships to undertake appropriate management or treatment operat ions to minimise the risks of ballast water introductions. Ballast water ex change at sea in organism-depleted deep ocean waters is currently the recom mended treatment option, although this technique has some limitations (Rigb y & Hallegraeff 1994). Here we show how a novel, cost-effective heating tec hnique using waste heat from the ship's main engine can be used to kill man y unwanted organisms. Healed water flushed through 1 of the ballast tanks i n an ocean trial resulted in destruction of all the zooplankton with very L imited survival of the original phytoplankton. The original organisms were essentially reduced to flocculent amorphous detritus.