The probability of special demand to replace the current ships has risen to the surface in accordance with the reinforced protection scheme for marine ecological systems. Applicable to any ocean-going ship to be completed in next autumn or later, it has been decided that a new environmental restriction will be imposed to make a ballast water treatment system mandatory to protect ecosystems.

Ballast water is sea water used for so called “balance weight” poured down to the bottom of ship for the purpose to keep ships balanced when passengers or cargoes have been unloaded at the ports of destination. The ballast water is discharged at the port of destination when cargoes are loaded again, but it means that biological substances or germs mixed in sea water are brought into the foreign sea zones far out of their habitats in case of ocean-going ships. They may break local ecological systems or affect economic activities mainly including fishery depending upon the regional conditions. It has been brought out to be controversial since the late 1980s.

In 2004, to cope with the issue, the “Ballast Water Control Treaty” was adopted in which it is mandatory to exchange 95% of ballast water in the sea zone in a distance of at least 200 miles away from the inland or to compel installation of the treating facilities to kill living substances in the ballast water. As Japan ratified in 2014, followed by Finland in September 2016, all conditions for enforcement were met and became effective in September 2017.
　
The treaty is applicable to almost all ocean-going ships except for those not loaded with ballast water or war ships, including existing ships as well as newly built ships. In case of the existing ships, the deadline to install a treatment facility will be by the first IOPP renewal test (test made every 5 years to certify conformity to oil discharge control) after enforcement of the treaty. For reference, it is not permitted to exchange ballast water after the test. In case of no loading of the mandatory treatment facility even after the deadline, no international navigation will be possible. Therefore, all applicable ships will be loaded with the facility by 2022 at latest.
　
There are a variety of ballast water treating systems such as a filter combined with UV or medical agents or an ozone sterilization type, either of them is said to be priced at 50 to 100 million yen. In case of the existing ships, as further costs must be added including construction charges, a certain shipbuilder said, “We expect that some business operators will make up their mind to replace their old ships which will require so much expenses. Even for loading the treating system welding works will be needed for installing the equipment platform or piping arrangements, and cutting works might be needed to cut the outer plates for the sake of putting the system into the ship. It means there are possibilities of special procurements of gas and welding/cutting supplies.”