Ballast Water Management Options Summary
Currently, ballast water exchange is the most common and widespread management tool to reduce the risk of ballast-mediated invasions. Ballast water exchange involves replacing coastal water with open-ocean water during a voyage. This process replaces coastal water and reduces the density of coastal organisms in ballast tanks that may be able to invade a recipient port, exchanging the BW tank's contents for oceanic water and possibly oceanic organisms which have a lower probability of survival in nearshore waters.
Ballast water exchange, conducted at least 200 nautical miles from any land mass, is recommended as a voluntary measure by the International Maritime Organization (IMO), but in 2004 BW exchange became a mandatory procedure for any vessel arriving to a US port or place that had previously operated outside the US/Canadian EEZ [link to reg]. However, it is important to recognize that BW exchange is not perfect. First, the ability to safely conduct ballast water exchange depends upon weather and sea surface conditions. Second, depending on route, a vessel may either be constrained by never passing more than 200 nautical miles from a land mass or the length of the voyage may not be long enough to complete an open ocean BW exchange. Second, BW exchange does not completely remove all viable organisms from BW tanks, so this process is only partly effective.
In 2012 the US Coast Guard promulgated new concentration-based BW discharge Standards for Living Organisms in Ship's Ballast Water Discharged in U.S. Waters (Ballast Water Discharge Standard) that laid out a schedule by which existing vessels and new builds must comply. Under these discharge standards, vessels must limit the number of viable organisms released with BW discharge to set values, either through
- no BW discharge,
- use of a Coast Guard approved ballast water management system
- discharge to facility onshore or to another vessel for purpose of treatment, or
- use of only water from a U.S. public water system.
For specific details regarding BW management and discharge regulations, visit the United States Coast Guard Ballast Water Management Program.