Abstract: A method and apparatus for treating ship ballast water before it is discharged into coastal waters. The ballast water may contain a generalized and diverse species population of harmful non-indigenous microorganisms. Before discharge, the ballast water is oxygenated and deoxygenated to reduce the populations of anaerobic and aerobic microorganisms, respectively. If anaerobic microorganisms are of no concern, the oxygenation step can be eliminated. Also, a method and apparatus for treating large volumes of any water, to reduce the population of a wide spectrum of diverse species of microorganisms wherein the water is deoxygenated, and then held in a sealed space for a period of time until the aerobic population has been reduced.

Abstract: A method and apparatus for treating ship ballast water before it is discharged into coastal waters. The ballast water may contain harmful non-indigenous microorganisms. Before discharge, the ballast water is oxygenated and deoxygenated to reduce the populations of anaerobic and aerobic microorganisms, respectively. If anaerobic microorganisms are of no concern, the oxygenation step can be eliminated.