Ballast water is great for stabilizing a ship in rough waters. Unfortunately, it is equally great at carrying all sorts of aquatic organisms across the world before releasing them into new ecosystems where many of them become problematic invasive species.

The cost of invasive species in the Great Lakes of North America have now reached $200 million a year and scientists predict that this number will increase sharply if the dreaded fish virus known as VHS manage to hitchhike its way into Lake Superior. Considering the number of international shipping vessels that arrive to this river system each week, it is probably just a matter of time unless drastic measures are put in place to stop the costly carrying of disruptive stowaways.

Is ballast treatment the solution?
On-board ballast treatment systems have been proposed by parts of the shipping industry as well as by many scientists, but so far, no one has been able come up with an efficient, cost-effective and safe solution that will work in both freshwater and saltwater. Researchers from the Lake Superior Research Institute* in Superior are now trying to change this.

“The question is how clean is clean? Zero would be great, but is it achievable?” asks Mary Balcer, director of the Lake Superior Research Institute.

Balcer, her research team and students at the University of Wisconsin-Superior are currently analyzing a long row of different solutions developed by private companies to see if any of them could help protect environments such as the Great Lakes from the threat of marauding newcomers.

The goal is to find a solution that will eliminate as many living organisms as possible before the ballast water is released. The treatment must also be safe for the ecosystem into which the water will be released.

Freshwater more demanding
Last month, researcher Tom Markee and several students tested using chlorine to eliminate organisms such as tiny worms, midges and water fleas growing in fish tanks in the university lab. Carrying large containers of chlorine on a ship is naturally dangerous, so Markee and his team instead opted for a solution where the treatment system produces its own chlorine by exposing saltwater to an electric current. The goal for Markee et al is now to find the ideal dose of chlorine as well as make sure that the system works in different types of water.

“They’ve tested it in saltwater and it works fine, but when you get to harbors or a river system, that’s when it becomes less effective,” Markee explains.

Other examples of techniques that are being explored by the research institute are the use of ultraviolet light, ozone and even lethal inaudible sound.

Balcer says her research team hasn’t yet found any viable treatment system that would kill all the living organisms in a ballast tank, but she’s happy with the progress that’s been made.

“Everyone’s behind getting the problem solved,” she says. Eventually we’ll be able to find something that really works.”

* Lake Superior Research Institute, http://www.uwsuper.edu/wb/catalog/general/2006-08/programs/LSRI.htm