ClearBallast purifies ballast water by combining magnetic separation technology developed for high-speed water treatment during rainy periods and coagulation technology used to remove plankton and bacteria at many water treatment plants. ClearBallast does not use disinfectants so the risk of residual chemicals causing secondary contamination is removed.

To gain approval from the Japanese government, Hitachi and Mitsubishi tested the ClearBallast water purification system at a land-based testing facility near Tokyo Bay. The companies used an actual-scale device and on-board testing used a test device installed on a 78,500 m³ LPG tanker.