A purification vessel was built for the purpose of purifying seawater by converting from a barge (2,350 tons), and seawater purification experiments were performed in Kasaoka Bay of Okayama Prefecture and Ashiya Port of Hyogo Prefecture. The capacity of the purification of seawater is more than 6,000 tons per day, and more than 80% of the suspended solids were removed. Therefore, many kinds of problems caused by the suspended solids are expected to be solved by purification vessels.