MOL Test Microplastics Collection System on Underway Car Carrier

Japan’s Mitsui O.S.K. Lines recently completed testing on a new device developed with Miura Co. that can continuously collect microplastics from seawater while a vessel is underway. The device, which builds on the companies’ previous efforts to filter microplastics while vessels are on dock, was demonstrated last month on the MOL-operated car carrier Emerald Ace.

With the aim of collecting microplastics, which are increasingly polluting the world’s oceans, MOL and Miura have been working together to design devices that capture the small plastic particles contained in seawater. 

The first system launched in November 2020 collects and traps the participles with a filter with a backwashing function, which is incorporated into the ballast water treatment system. Ballast water being treated for release passes through a fine filer that traps the plastics before the waters leave the vessel. After a successful test on a wood chip carrier, MOL has installed the system on five vessels, including three bulk carriers and two wood chip carriers. While these vessels are unloading ports, the systems treat a total of about 16,000 m3 of seawater.

The new system expands on that capability by continuously filtering seawater while the vessel is underway. According to the companies, the addition of a centrifuge allows the device to efficiently separate floating microplastics from concentrated seawater with a high density of floating debris, without closed plumbing. This enables further filtering of a seawater line, which continually draws in seawater, and treating the full amount of discharge water after passing through the filter with the backwashing function of the ballast water treatment system. 

 

Schematic view of centrifugal microplastic collection device and piping (MOL)

 

On the Emerald Ace, microplastics were continuously collected while sailing, by connecting the system to the cooling seawater line, which always draws in seawater. This gives the system an annual seawater treatment capacity about 70 times that of the previous device. 

MOL is also collecting data on the levels of microplastic being filtered. They report that there is a growing demand for this type of data among research institutes, as this data can be applied to research on microplastic’s movement. The data also permits measurement of the effects of various approaches to the reduction of the pollution. MOL collects data such as components, amounts, places, and periods of microplastics collected with the device for future research.

Miura is moving ahead with the development of the product, which will have a larger treatment capacity. The commercial system will also have a full treatment system for ballast discharge water by combining a ballast water treatment system and a microplastic collection device with cooling seawater.