Effectiveness and kinetics of ferrate as a disinfectant for ballast water

This study examined whether ferrate could meet the international standards for successful ballast water treatment, including final concentrations of less than 1 CFU/mL of Enterococci, less than 2.5 CFU/mL of Escherichia coli, and less than 1 CFU/100 mL of Vibrio cholerae. Pure cultures of E. coli, Klebsiella pneumoniae, and V. cholerae, and a mixed culture of Enterococcus faecium and E. faecilis were grown in saline solution to simulate ballast water and were treated with dosages of ferrate ranging from 0.25 to 5.0 mg/L. A ferrate dose of 5 mg/L resulted in complete disinfection of all organisms tested, and smaller dosages were also very effective. Tailing was consistently observed, and the Hom's model (1972) 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. Ferrate shows good potential as an effective disinfectant in the treatment of ballast water.