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First of 10 planned bioreactors installed near targeted rivers

By Staff | Sep 26, 2011

This bioreactor was recently built on the Arlo Van Diest farm near Webster City. It’s 126-by-31-feet and is filled with wood chips, designed to filter nitrates from tile water before it reaches a nearby waterway in the Boone River watershed.

WEBSTER CITY – Through the Mississippi River Basin Healthy Watershed Initiative, the Natural Resources and Conservation Service, Iowa Soybean Association and the The Nature Conservancy are partnering together on a project that will eventually install close to 10 bioreactors along watersheds in Iowa.

The first of a potential 10 bioreactors that are a part of the project was installed earlier this month on the Arlo Van Diest farm near Webster City, situated along the Boone River watershed.

“This is a first in Iowa the NRCS is a part of,” said Jason Johnson, public affairs specialist for the USDA NRCS. “We are unique in getting this started.”

Areas along the Boone River watershed where bioreactors will be installed, Johnson said, feature flat topography which calls for more tile installed throughout the fields and more drainage issues and issues with water impairment.

Bruce Voigts, MRBI project coordinator for the Boone River Watershed in Wright and Hamilton counties, described the denitrifying bioreactor simply as a “septic tank in a field.”

Wood chips are being dumped into the bioreactor on the Arlo Van Diest farm, near Webster City.

According to the ISA Environmental Programs and Services website, a bioreactor is essentially a buried trench filled with a carbon source, such as wood chips, through which tile water is allowed to flow.

The carbon source provides material upon with microorganisms can colonize. Using wood chips as a food source, the microorganisms begin breaking down nitrate in the water and expelling the nitrate as dinitrogen gas (N2), a primary atmospheric component.

A bioreactor has no adverse effects on crop production and is designed in a way that it does not restrict drainage.

A control structure determines the amount of tile flow that is diverted into the bioreactor. During periods of high flow, excess water bypasses the bioreactor and continues to flow through the existing field tile.

Typically, the bioreactors do not take any land out of production as they are usually installed into existing filter strips on the edge of the field.

“This is a first in Iowa the NRCS is a part of.” —Jason Johnson USDA-NRCS public affairs specialist

The is the second bioreactor that has been installed on one of Van Diest’s fields, the first one being installed a few years ago through the ISA.

So far, Van Diest said, he is pleased with the results from the first one and excited to see the results of reduced nitrates flowing into the water as a result of the newer structure.

Johnson said project partners are expecting a 70 percent reduction of nitrates in the surface water in the nearby watershed as a result of the new bioreactor.

Ingraham Construction, of Webster City, was the contractors to build the 126-by-31-foot bioreactor.

Contact Kriss Nelson at jknelson@frontiernet.net.

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