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

Ten billion tonnes of shipping ballast water are carried around the world annually. This provides an inadvertant mechanism for the transfer and dispersal of harmful bacteria, toxic dinoflagellates, seaweeds, molluscs, starfish, crabs and fish (Rigby and Hallegraeff 1996). Establishment of nonindigenous and harmful organisms have resulted in significant ecological and environmental damage and also pose a threat to human health through Paralytic Shellfish Poisoning, and possibly even Cholera outbreaks (McCarthy and Khambaty 1994). As a result of these concerns, the International Maritime Organisation has recognised shipping ballast water as an international pollutant of major 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 operations to minimise the risks of ballast water introductions. Ballast water exchange at sea in organism-depleted deep ocean waters is currently the recommended treatment option, although this technique has some limitations (Rigby and Hallegraeff 1994). Here we show how a novel, cost-effective heating technique using waste heat from the ship's main engine can be used to kill many unwanted organisms. Heated water flushed through 1 of the ballast tanks in an ocean trial resulted in destruction of all the zooplankton with very limited survival of the original phytoplankton. The original organisms were essentially reduced to flocculent amorphous detritus.