Tool could curb invasive species
- By Tom Weaver
The Green / Invention
Tool could curb
Eighty percent of world trade is carried by ships. A big cargo ship docks in the United States about every six minutes. It unloads goods that can come from any port on the planet.
Unfortunately, these ships also often unload invasive species—unwanted hitchhikers, like zebra mussel larvae and purple loosestrife seeds—travelling in the ship’s ballast water. This, too, can come from any port on the planet.
In the United States, dumped ballast water may be the leading source of invasive species found in freshwater and marine ecosystems, according to the Environmental Protection Agency. From the Caspian Sea to Lake Champlain, communities have suffered profound damage—like collapsed fisheries and clogged pipes—due to invaders that arrived in ballast water.
Ballast water is essential to cargo ships (as well as cruise-liners and sailboats) allowing them to stay at the proper depth, steer correctly, and not tip over. Unfortunately, efforts to remove species from the twelve billion tons of ballast water dumped annually have proven very difficult, often toxic, and expensive.
But Junru Wu, a physicist at the University of Vermont, has invented a promising new approach: blast them to death with sound.
He and Meiyin Wu (no relation), an ecologist at Montclair State University in New Jersey, have been collaborating for nearly a decade to create a device—they call it BallastSolution. The machine will treat ballast water, as ships take it in and dump it out, with a lethal dose of ultrasound. (Lethal, that is, to wee beasties; it’s harmless to people.)
In recent tests, “we thought we’d be happy if we could kill close to ninety percent” of the small clams, water fleas, and E. coli bacteria sent into the machine, says Junru Wu, “but the results were over ninety-nine percent.”
The promise of their collaboration is well timed, as the U.S. Coast Guard rolled out rules in March requiring ocean-going ships to have an onboard ballast treatment system and limiting how many organisms they can release in coastal waters. And the U.N.’s International Maritime Organization will require all ships, millions worldwide, to have a treatment system by the end of 2016.
The patented BallastSolution device, funded by a $673,000 grant from the U.S. Department of the Interior, is made from twenty ultrasound transducers, arranged in a spiral, that protrude into a pipe about ten inches wide on the interior. As the ballast water pumps through, the transducers oscillate at frequencies above the range of human hearing. In goes a load of potential bad guys at one end—and out comes nearly sterile water at the other.
At least that’s what the first tests have shown. The machine, built at UVM by Junru Wu and post-doctoral researcher Di Chen, was delivered to Meiyin Wu at the beginning of 2012 for testing in her laboratory in New Jersey.