The introduction of aquatic nuisance species (ANS) and bacterial pathogens from discharge of ballast water by sea-faring vessels is an ongoing problem that threatens ecosystems and human health. This study investigates the disinfecting capability of ferrate in a marine environment on several organisms listed in international standards for ballast water management. Organisms were grown in a saline solution and were treated with dosages of ferrate ranging from 0.25-5.0 mg/l. A ferrate dose of 5 mg/l resulted in almost complete kill for all organisms tested. Smaller dosages have also been very effective, particularly if all organic material from the nutrient broth used to cultivate them is removed by washing the cells with saline solution. Ferrate appears to act very quickly, with tailing occurring after about 5-15 minutes. Analyses of the data with the CT approach, the Chick-Watson and Hom's models, and an oxidant demand equation derived from equations recommended by the Water Environment Federation (WEF) are in good agreement that ferrate concentration is more important than contact time. The Hom's model appeared to most accurately represent the action of ferrate on these organisms. Salinity and pH did not adversely affect results, and regrowth was not a problem. Two measures to reduce clumping did not eliminate the observed tailing effect, suggesting a different mechanism for this phenomena. These preliminary tests indicate that ferrate could be a very effective disinfectant in the treatment of ballast water, and the short half-life of ferrate is an advantage, since the ballast water is subsequently released into the environment.
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