A D-1 Ballast Water Exchange Standard, which can be achieved using either of three methods of ballast water exchange, and a D-2 Ballast Water Performance Standard, which is achieved by ballast water treatment. (For questions on the latter see BALLAST WATER TREATMENT EQUIPMENT in Section D. ) Due to its limited biological efficiency, the D-1 Standard is to be regarded as an interim measure until the D-2 Performance Standard comes into effect.
