The problems start when this water, which may have been taken on board in far-flung places, is released in ports thousands of miles away – microorganisms, plants, worms and crustaceans gain a foothold in a new environment and often out compete the local flora and fauna. The results can be devastating, with wholesale collapses in the populations of local wildlife.
And it’s not a new problem - scientists first noted the signs of an alien species probably introduced in this way after a mass occurrence of the Asian phytoplankton algae Odontella (Biddulphia sinensis) in the North Sea in 1903.
Fortunately, the world has woken up to the issue and there are now strict regulations in place to prevent the spread of invasive organisms from ballast water.
Under the Ballast Water Management (BWM) Convention, a ballast water management system (BWMS) must meet a performance standard based on agreed numbers of organisms per unit of volume.
There are numerous ways to control organisms – physical barriers, chemical disinfection, heat treatment and ultraviolet are just a few.
Whatever method is chosen, it is vital to control the flow of ballast water throughout the stages of the system and discharge it according to the guidelines.
This is achieved by using a series of valves. Positioning them reliably is critical to ensure the overall system works as intended and so valve positioners are essential.
Valves are likely to be working close to pumps and other heavy machinery, so the positioners you choose need to be robust. Conditions will be wet so quality materials are also important. ABB’s entry level TZIDC positioners have an aluminium housing, for example, while the top-of-the-range EDP300 uses stainless steel to offer the best possible long-term protection - a high IP rating is also a good idea.