Next time you see a container ship in port unloading its freight, remember that there is another, unseen cargo on board that could threaten the ecosystems of the very port the ship is berthed in. Ships take on huge volumes of ballast water each time they leave port. Ballast is used as compensation for the weight of unloaded or missing cargo and emptying fuel tanks to maintain the required draught of a vessel and ensure stability. The World Wildlife Fund estimates that a staggering ten to twelve billion tons of ballast water is transported across the world’s oceans every year! This water is discharged at every port the ship calls into, as cargo and fuel is loaded or unloaded. Countless alien animal and plant organisms are carried along as tiny stowaways in the ballast, and then released into each port of call. In many cases these new habitats offer the chance for the organisms to prosper in the absence of their natural enemies. This enables them to spread rapidly, causing irreversible damage to the local aquatic flora and fauna.
A new standard laid down in 2004 in the Ballast Water Management Convention, called D-2, prescribes the treatment of ballast water required on every ship. Filtration is an important step in removing organisms down to sizes in the range of 10 to 50 μm.
With their Optimized Dutch Weaves and Reversed Plain Dutch Weaves, GKD –GEBR. KUFFERATH AG has developed a solution that fits the bill. The company has a range of mesh constructions (laid, wrapped or sintered) and seam designs (welded, folded or clamped), as well as a wide range of materials capable of withstanding aggressive environments: super duplex (1.4410), Hastelloy (2.4602), Monel 400 (2.4360), SS 904L (1.4539) or SS 316L (1.4404). This allows tailoring of the filter media materials to the particular system in terms of resistance to corrosion, chloride ions and heat, as well as non-stick and anti-fouling properties.
A recent article in Stainless Steel World examined some of the advantages of these robust filters; read the full article.