Treating Ballast Water Could Fight Invasive Species

Jon Hamilton, NPF 14 Jul 09;

Ships that transport goods around the world are carrying some dangerous stowaways.

Tiny organisms travel from port to port in a ship's ballast water. And some of them have become invasive species, wreaking havoc in waters around the world.

So scientists are testing ways to kill these potential invaders before they can escape.

One place that sort of testing takes place is on the Cape Washington, a 700-foot cargo vessel moored in the Chesapeake Bay near Baltimore.

"The Chesapeake is a perfect place for this work," says Mario Tamburri, a researcher at the University of Maryland and director of the state's Maritime Environmental Resource Center. He estimates that at least 150 nonnative species have become residents of the Chesapeake Bay — most probably arriving in ballast water.

And the Cape Washington offers a perfect example of how that's possible, Tamburri says, as he opens a hatch in the ship's bottom deck. The hatchway leads to one of the ship's ballast tanks, which allow the ship to remain stable despite changes in the amount of cargo it's carrying.

"The tank itself is about 650 cubic meters," he says, or the size of a large swimming pool. And there's another tank just as big on the other side of the ship.

When the Cape Washington unloads cargo, it fills its tanks with millions of gallons of Chesapeake Bay water, carrying billions of organisms, including tiny eggs and larvae from a wide range of sea creatures. Those creatures could, in theory, be transported to Dubai or Singapore within a couple of weeks, Tamburri says.

"Even though lots of organisms die on those voyages, it only takes a few that survive," he says, to allow an invasive species to establish itself in another part of the world.

And once invasive species become established, "they are virtually impossible to eradicate," says Andrew Hudson, who advises the United Nations Development Program on international water issues.

Most species don't do well in a new place, he says. But the ones that can survive are often so adaptable that they take over.

Zebra mussels from Russia, for example, have clogged the intake pipes of power plants and water treatment facilities along many U.S. rivers. That costs the United States billions of dollars each year.

And invasive species coming from U.S. waters can cause even bigger problems. A comb jellyfish that has found its way to the Black and Caspian seas is devouring the tiny offspring from a fish called the kilka, Hudson says.

"The kilka fishery has in effect collapsed," he says. "And we've seen very moving footage of Iranian fishermen who've basically lost their livelihoods because of the collapse of the kilka fishery."

Countries including the U.S. have tried to control the problem by requiring incoming ships to flush their ballast tanks in the open ocean. But that hasn't done the trick.

So governments are preparing to impose tougher standards on discharged ballast water.

In response, several companies have developed systems to kill organisms in ballast tanks.

These systems need to be affordable and meet two other criteria, he says. First, "they have to be highly effective in terms of drastically reducing the proportion of living organisms in that water," Hudson says. Second, "if they use chemicals, they need to ensure that the water that's released is free of any kind of toxic chemicals."

Independent scientists need to test the systems to make sure they work as advertised.

And that's what Tamburri and his team are doing on the bottom deck of the Cape Washington.

It's a space big enough for full-court basketball, and designed to carry things like tanks and Humvees and helicopters.

But for the moment, this part of the ship has been transformed into a research lab to test ballast water treatment systems.

"We have a variety of pipes and tanks and areas for looking under a microscope and sensors and a whole suite of instruments, Tamburri says.

Tamburri points to a pipe coming from the ship's engine room.

"Water comes through that first 8-inch valve, and then it's split in two ways," he says. "Half the water goes into a control tank, which means its untreated, just natural ballast water; and half the water goes through a treatment system. And the one we're looking at over the next few weeks is a system that chlorinates the water and filters the water to remove the organisms."

A ship couldn't easily carry enough chlorine to get the job done, so the Cape Washington is making its own using electricity, which can produce chlorine from the salt in sea water.

The chlorine is potent at first, but breaks down and would presumably become harmless during the voyage.

Researchers won't know how well this system works, though, until they compare samples from the treated ballast tank with samples from the untreated control tank.

"The idea is that after five days, the treated [tank] should have very close to nothing alive in there," he says.

Chlorine is just one approach to the ballast water problem, Tamburri adds. Companies are also trying to zap the stowaways with heat, ultraviolet light, ozone and nitrogen.