Northern Minnesota researchers close in on sulfate pollution solution Outside the wastewater treatment plant in the Iron Range town of Aurora, ...

Northern Minnesota researchers close in on sulfate pollution solution Outside the wastewater treatment plant in the Iron Range town of Aurora, ...Northern Minnesota researchers close in on sulfate pollution solution 

Outside the wastewater treatment plant in the Iron Range town of Aurora, a small trailer could hold clues to solving a big environmental problem facing northern Minnesota — how to protect wild rice from sulfate, a pollutant released by iron ore mines, wastewater treatment plants and other industries.

Mei Cai, an environmental engineer with the Natural Resources Research Institute at the University of Minnesota Duluth, points to a series of tanks where a chemical called barium chloride reacts with dissolved sulfate in the water to form particles.

Then another chemical is added that clumps those particles together into bigger pieces, forming a sludge that can be removed from the water, which then goes through a final filtration process.

The water that comes out of the Aurora treatment plant has high levels of sulfate; about 250 parts per million. The technology Cai is demonstrating in the mobile trailer has successfully reduced sulfate levels in the water from the plant to below 10 parts per million, low enough to meet the state's strict sulfate rule for water that's released into lakes and rivers where wild rice grows.

That could be especially important here in Aurora, because treated water discharged from the city water plant eventually flows into the Partridge River, which was recently added by the U.S. Environmental Protection Agency to Minnesota’s list of waters that do not meet the state’s wild rice sulfate standard.