DULUTH, Minn. (AP) — Researchers have conducted a large-scale test of a new system to kill invasive species hiding in the ballast water of Great Lakes freighters and expect to get test results back next month.

Crews recently pumped lye into two of 10 ballast tanks inside the 1,000-foot Indiana Harbor as it left Gary, Ind., treating 1.8 million gallons of ballast water. The chemical then was neutralized with carbon dioxide as the boat traveled across Lake Superior before releasing the ballast water in the Duluth-Superior harbor.

The Duluth News Tribune reported Tuesday it’s believed to be the first such major-scale test on the Great Lakes, with researchers from multiple universities and federal agencies involved along with funding from multiple state and federal grants.

The issue is important because state and federal governments are moving to require ballast treatment to help stop invasive species such as zebra mussels and nonnative fish, which cause an estimated $5.9 billion in damage to the Great Lakes every year. More than 60 percent of invasive species introduced in the Great Lakes have come from ballast water discharged by oceangoing ships.

“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 of the effort, told the News Tribune.

Lye, also known as sodium hydroxide, raises the pH of water to kill organisms. It is commonly used in wastewater treatment plants but had not been used in major ballast water applications before. Crews then neutralized the chemical with carbon dioxide so it wouldn’t keep killing when the ballast water was released.

“We hope to prototype it all the way to full size, all 10 tanks, very quickly,” Green said.

Green praised American Steamship Co. for offering the Indiana Harbor for the tests, calling the company a leader in the effort to curb invasives. The effort required installing more than a half-mile of tubes on the boat, and researchers welded treatment equipment to the boat for the tests.

“As stakeholders in both the economic and environmental health of the Great Lakes region, we feel an obligation to support efforts to combat the detrimental effect of invasive species brought in by oceangoing ships,” Noel Bassett, vice president of American Steamship Co., said in a statement.

The Superior, Wis.-based Great Ships Initiative now is testing water samples drawn from the ballast tanks to see if the chemical indeed killed organisms and whether the treated water was then successfully neutralized to prevent environmental harm. Results should be available next month.

Barnaby Watten, a senior scientist with the U.S. Geological Survey, said earlier shore-station testing at the Great Ships Initiative facility in Superior reached a 98 percent kill rate for living organisms in the water, with most perishing within 2 hours of exposure to sodium hydroxide.

“We’re hoping to get similar results in real world conditions,” Watten said in a statement. “But this trial demonstrated the feasibility of our process, and we are on target with equipment development to deliver and mix these biocides and neutralizers.”

Green moved earlier to ban ballast water discharges in Isle Royale National Park waters and installed a ballast treatment system onto the park’s own passenger boat to avoid introducing a fish-killing disease to the park’s waters. She has worked over the past three years to bring academic researchers, industry leaders and federal regulators together to develop a system for Great Lakes freighters.

“I can’t protect the park unless we have a safety net for all of Lake Superior,” she said.

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