International Maritime Organization (IMO) adopted the International Convention for the Control and Management of Ships' Ballast Water and Sediments in 2004. This convention requires the strict standard for discharge of ballast water performance described as D-2 regulation, but many technical problems in developing ballast water management systems remain to be solved to keep the D-2 regulation. Most developed equipment for ballast water treatment are based on chemical treatment, but it could be feared that the chemical substances cause some marine environment risks due to residual chemical ones in the discharged ballast water. Our developed equipment for the ballast water treatment is based on filtration technology by the combination of spring filter and diatomite as physical treatment. We expect that this technology would become one of practical measures for environmental-friendly ballast water treatment not to use of chemical ones.