MHI and Mitsui O.S.K. Lines Co-develop Japan's First ClassNK Approved Installation Technology for Container-Type Ballast Water Treatment System -- Will Enable Faster BWTS Retrofitting and Deployment. Mitsubishi Heavy Industries, Ltd. (MHI), working jointly with Mitsui O.S.K. Lines, Ltd. (MOL), has developed installation technology of a ballast water treatment system (BWTS) enclosed in a standard-size freight container in the hold of container ships. The system using container-type BWTS design is the first to receive the concept approval from Nippon Kaiji Kyokai (ClassNK)*.