Minnesota River phosphorus cleanup

Waste water
This wastewater is just about to leave the New Ulm plant and flow underground to the nearby Minnesota River. The state has mandated a 35 percent reduction in the amount of phosphorus water like this can carry into the Minnesota.
MPR Photo/Mark Steil

At a laboratory in the New Ulm Wastewater Treatment Plant a busy little machine is a key player in the fight against river pollution.

Del Senst
Del Senst supervises the New Ulm Wastewater Plant. Senst served in Viet Nam with the Army and worked construction before joining the plant some 30 years ago.
MPR Photo/Mark Steil

A steady stream of water flows past it. Every few minutes the machine hisses into action. It scoops a few ounces of water and deposits the liquid in a holding tank. The water is a small diversion from the much larger stream the plant discharges into the Minnesota River.

Plant Supervisor Del Senst says the water in the holding tank will be tested.

"Every 24 hours we take out and run our samples based on the flow going through the plant," says Senst.

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The testing gives a complete profile of what's in the discharge, including phosphorus. The unwelcome element comes from varied household and industrial sources. Right now, like nearly all the wastewater treatment plants in the Minnesota River basin, New Ulm discharges too much phosphorus. That will change under new state regulations.

"By 2010 there has to be a minimum of a 35 percent reduction in phosphorus."

"In fact by 2010 there has to be a minimum of a 35 percent reduction in phosphorus loading to the Minnesota River," says Senst.

To accomplish this New Ulm will spend about $3,000,000 on a new system to biologically remove phosphorus. Senst says one-cell organisms in the wastewater, similar to amoebas, will do the job.

"The bugs will eat the phosphorus and then when the bugs die we're able to collect them in the sludge that's produced," says Senst. "And then taking the bugs and the sludge out and letting the clear water go, then has reduced the amount of phosphorus that's in the clear water."

With more than three dozen wastewater plants doing the same thing the water quality of the Minnesota River should improve noticeably.

New Ulm wastewater plant
The New Ulm plant tests and treats the city's waste water.
MPR Photo/Mark Steil

The accumulated effects of too much phosphorus are most noticeable in the last 20 miles or so of the Minnesota River before it joins the Mississippi.

There's a concentration there of phosphorus from many sources; city wastewater but also farm field runoff and other locations. The accumulated phosphorus produces river choking algae. The algae's life and death cycle consumes oxygen.

Jim Wolf of Bloomington is president of a group called "Friends of the Minnesota Valley". He says the impact of low oxygen levels in the Minnesota River is visible.

"The water is green and some days you'd almost say it has a little bit of an odor to it," says Wolf. "It does not appear to be something that you'd like to swim in or eat fish that come out of that environment."

Individual cities along the Minnesota and its tributaries must begin reducing phosphorus discharges by 2008.

Further reductions are required each following year.

Steve Sommer of the Minnesota Pollution Control Agency says most communities plan to take the New Ulm approach; using biological tools to reduce phosphorus.

There is another option. Sommer says some wastewater treatment plants may be able to meet phosphorus targets without building new treatment structures.

They can buy pollution reduction.

That's because of something called Jordan Trading Units. The units calculate the impact phosphorus has on the Minnesota River at the town of Jordan. The closer to Jordan, the bigger the impact. Sommer says the units can be sold. So a city that's under its phosphorus cap can sell units to a city which is over its maximum.

"Typically what we figure is going to happen is the larger facilities that have the money to make the add-ons, the control equipment, would be the ones that would be able to sell to maybe a smaller facility that doesn't have the money in order to make the plant upgrades," says Sommer.

Sommer says the open market will determine the price of a Jordan Trading Unit. It's an approach that's used in other types of pollution control.

The Minnesota River will be a special laboratory for the concept. It's routinely listed as one of the state's most polluted rivers. The phosphorus cleanup is one part of a multi-faceted effort to improve water quality. Already state regulators claim success in reducing sediment levels. Phosphorus reduction adds to the hope that one day the river will run clean.