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Published September 16, 2013, 10:25 AM

Removing nitrates from Minn. water

Residents of St. Peter, Minn., pay high rates for drinking water because it takes extra equipment to remove the unhealthy levels of nitrates from its groundwater.

By: Minnesota Public Radio News,

ST. PETER, Minn. — Residents of St. Peter, Minn., pay high rates for drinking water because it takes extra equipment to remove the unhealthy levels of nitrates from its groundwater.

When nitrates from agricultural fertilizer seep into drinking water supplies, they pose a risk to infants, pregnant women and others. They’ve made the southern Minnesota city one of at least two dozen communities in the state with unhealthy levels of fertilizer by products in their groundwater.

Bruce Montgomery, manager of the fertilizer management section for the state Department of Agriculture, says adjusting fertilizer practices can only partially help protect water supplies. Despite farmer cooperation, nitrate levels in one St. Peter city well are still 60 percent above recommended levels.

So St. Peter uses a reverse osmosis water treatment system. It’s one reason customers pay in the top third of municipal water rates in Minnesota, says

Todd Prafke city administrator. The city hasn’t analyzed exactly how much nitrate removal costs an average resident. But state agriculture officials say it can add as much as $200 a year to a typical homeowner’s bill.

“It’s an additional level of treatment that you might not otherwise undertake,” Prafke says. “If you’re doing more stuff there’s an additional cost related to that more stuff that you’re doing.”

Montgomery says there’s a proven solution: growing perennial crops that absorb nitrates, such as alfalfa, strategically placed in wellhead areas. Alfalfa root systems grow as much as 8 feet a year.

He says the crop is “like a very good Hoover vacuum cleaner ... It does a really, really good job of removing those nitrates.”

Alfalfa can reduce nitrates reaching aquifers by up to 90 percent, he says. The hitch is that farmers are reluctant to switch because they don’t think it’s as profitable as corn.

But they’re not necessarily right, says Mike McDuffy, an extension economist at Iowa State University. He says he knows several farmers who are making good money from alfalfa, partly because it’s in short supply as a result of drought.

According to Iowa State University data, alfalfa this year could clear as much as $300 an acre. Corn, on the other hand, is fetching lower prices than recent years, and corn farmers may see profits of less than $200 an acre this year.

Duffy says rotating alfalfa with other crops preserves a good share of the environmental benefits, while also increasing profitability.

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