The Free Press, Mankato, MN

Local News

November 15, 2012

Victory celebrated in Minnesota River phosphorus battle

MANKATO — Wastewater managers and environmental regulators met in Mankato Thursday to do something they don't get to do very often.

They celebrated their success on a complicated environmental issue -- the reduction of phosphorus pollution in the Minnesota River basin -- with conclusive data to back it up.

"Hopefully, you can feel good about what you've accomplished collectively ... I want to stress collectively," said Gene Soderbeck, municipal unit supervisor of the Minnesota Pollution Control Agency's southwest region.

Phosphorus pollution starts a chemical process that eventually hurts a river's fish and wildlife. The phosphorus feeds excess algae, which die and are eaten by bacteria, which suck up oxygen in the process.

Though the program to reduce phosphorus has not technically met its goal -- if only because the drought hasn't been severe enough to test it -- it has clearly succeeded. Phosphorus emissions from the largest polluters, during the driest months when phosphorus is most dangerous, have declined from 90,227 pounds in 2000 to 25,323 pounds this year. One of the program's goals was a reduction to 26,891 pounds.

The results of a study on this program was announced earlier this week and printed in Tuesday's Free Press.

Mankato has been a leader in trading phosphorus credits, which are essentially the right to pollute above your limit. Of the 15 cities and companies that bought the right to exceed their limits, Mankato sold credits to nine.

Public Works Director Mark Knoff told the civic center crowd of several dozen about how Mankato's sewer plant cut so much of its phosphorus that it had lots of credits to sell to other entities.

It started, he said, when the nearby Calpine power plant needed a lot of water to operate. Instead of using water from the river or the aquifers, the city and Calpine paid to clean the wastewater so it could be legally useable in the power plant. Mankato then had the first wastewater plant in the state that treated its water to that degree.

And a lot of phosphorus was removed in the purification process, giving the city a lot of credits to trade.

While the officials congratulated themselves on this progress, they acknowledged there are other pollutants in the river, such as sediment. And that environmental victory is unlikely to come as swiftly. Though individual facilities were responsible for 65 percent of phosphorus pollution, sediment comes from eroding riverbanks and farms, of which there are many.

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