Ballast Water Heating Offers a Superior Treatment Option
Geoff Rigny, Gustaff Hallegraeff, and Alan Taylor
Ballast water regulations in place in many parts of the world to minimise the risks associated with the introduction and establishment of nonindigenous organisms into ports around the world currently require ship’s Masters to undertake a range of approved management procedures, primarily based on exchanging the water at sea during the voyage. Limitations associated with ocean exchange have prompted significant research and development into alternative treatment techniques that will offer enhanced biological effectiveness and make practical implementation, ship’s safety and cost more attractive. At a Diplomatic Conference in February 2004 the International Maritime Organisation adopted the International Convention for the Control and Management of Ships’ Ballast Water and Sediments (which includes Performance Standards and provisions for incorporating improved treatment techniques). Heating the ballast water to 40-45°C is sufficient to kill or inactivate most ballast water organisms (except bacteria) that have the potential to initiate new invasions by inactivating their metabolic processes. Heating to lower temperatures for longer periods of time can be effective and the relationship between time and temperature for a wide range of marine organisms is reviewed. A variety of practical shipboard design options utilizing waste heat from the engine cooling system in conjunction with other heat sources available on the ship are examined in a number of case studies and other suggested operational concepts based on optimizing the heat availability, different voyage conditions, sea temperatures and other operating parameters (including higher treatment temperatures for bacteria, if required. Full scale shipboard trials utilising one of the options involving only waste heat from the cooling system in a combined flushing/heating mode has demonstrated high levels of biological and cost effectiveness with a superior performance to typical ballast water exchange and other treatment options currently available.