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Stopping The Invasion Of Zebra Mussels

February 01, 2006

Hans van Leeuwen’s research presentation includes pictures of zebra mussel colonies clogging pipes and covering boat bottoms.
It also shows a map that indicates zebra mussels invaded Iowa’s stretch of the Mississippi River in the early 1990s.

And there’s a picture of van Leeuwen, an Iowa State University professor of civil, construction and environmental engineering, wearing his hardhat to examine technology he’s helping to develop that would prevent such invasions.

The invasion of exotic marine species is a national problem. There are sea lampreys and spiny water fleas impacting the Great Lakes. There are more than 230 exotic species dominating San Francisco Bay. And there are problem species that have made it inland to Iowa.

To get from place to place, these species often hitch a ride in a ship’s ballast tanks. Those tanks are filled when empty tankers and cargo ships travel from port to port. The extra weight gives the ships stability and control. Exotic species – such as zebra mussels from Russia – can be carried in the ballast and dumped in a new home where they have no predators or natural controls. They can overwhelm native ecologies, spread into new territories and cause billions in economic damage.

Prof. van Leeuwen and a team that includes researchers from the University of Washington in Seattle, the University of North Carolina Wilmington, the BP energy company, the Alaska Tanker Company, the Nutech-03 water recycling and pollution control company and other research companies have developed a solution. They say treating ballast water with ozone generated on ships is a safe, economical and effective way to remove exotic species from the ballast tanks and thereby reduce their spread.

The ozone is toxic to the exotic species. It also reacts with bromide in seawater to create bromine, another toxin to the species. The ozone and bromine break down in the ballast tanks after two days so the treated water can be safely discharged back into the sea.

The National Oceanic and Atmospheric Administration is supporting the research with $1.7 million in grants. Prof. van Leeuwen said BP and the Alaska Tanker Company have provided in-kind support equivalent to about $2 million.

His contribution has been to design the equipment that introduces ozone into the ballast tanks as they’re filled. The injection technology virtually eliminates ozone gas emissions. Prof. van Leeuwen and his colleagues have five patents pending on the technology.

The technology has been tested for about two years on a double-hulled oil tanker, the Tonsina. Improved technology is being installed on another tanker, the Prince William Sound, for more testing.

He said the technology has several advantages: Ozone can be created on ships. Ship crews don’t have to bother with stockpiles of toxic and corrosive chemicals. And ozone treatment can be traced and verified in the seawater helping to enforce any future treatment requirements.

Prof. van Leeuwen has met with U.S. House and Senate staffers who are drafting legislation that would require treatment of ship’s ballast water. And he knows what kind of treatment he’d like to see in the law.

“I’m totally convinced,” he said of the ozone treatment. “I certainly believe this is the technology for the future. There’s nothing that can beat it in terms of simplicity, cost effectiveness, low maintenance, accountability and safety to protect our water resources.”

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