How to kill invasive species aboard a Great Lakes freighter

Aug 23, 2011

Invasive species introduced into the Great Lakes by the shipping industry have caused enormous economic and ecological damage. Some estimates put the costs of invasive species in the Great Lakes at billions of dollars annually.

Quagga mussels, round gobies, and spiny waterfleas have spread all over the place in the Great Lakes, disrupting the food chain.

The question is, how do you get rid of these critters that can hide in the nooks and crannies of a ship's ballast tanks?

The critters get in when a ship pumps in ballast water in an overseas port. They hitch a ride across the Atlantic or Pacific and get dumped in U.S. waters.

Today the EPA requires ships to "swish and spit" before entering U.S. ports. That means international ships have to flush out their ballast tanks with salt water from the open ocean before coming in.

It's a sanitizing method that several states and environmental groups say is inadequate, and they're pushing the EPA to do more. But nobody knows what kinds of ballast water treatment systems will work AND will be cost-effective to shipping companies.

The Duluth News Tribune has a story today about an effort that is thought to be the first "major-scale test on the Great Lakes" of a ballast water treatment system.

It's being tested on a 1,000 ft. Great Lakes freighter. Freighters that stay in the Great Lakes don't bring the invasive species in, but they can help spread invasives from port to port around the region.

They Tribune reports the researchers treated 1.8 million gallons of ballast water in the ship with lye - a caustic chemical often used as an industrial cleaning agent. Before the ship reached it's destination port, they neutralized the treated water with carbon dioxide before releasing it.

One of the biggest challenges in combating invasive species in ballast tanks, is how best to sanitize such a large amount of water sitting in the complex maze of a ship's hull:

“The good news is that we were successful in delivering the biocide at this huge level for a 1,000-foot laker, then successfully delivered the neutralizer, all while the Indiana Harbor was on the job,” Phyllis Green, superintendent of Isle Royale National Park and the instigator behind the effort, told the News Tribune.

The Tribune reports that research into the real-world test is ongoing. Water samples from the ballast tanks will show whether the lye killed organisms "and whether the treated water was then successfully neutralized to prevent environmental harm."

Results of these tests should be available next month, the paper reports.