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A Denitrifying Bioreactor is a nitrate reduction method that involves underground trenches filled with woodchips, through which tile water flows before exiting the line. The woodchips serve as a substrate for bacteria that break down the nitrates through chemical processes. Bacteria “eat” the carbon in the woodchips, “breath in” nitrate from the water, then “breathe out” N2, thus reducing the nitrate content of the water before it enters surface runoff.

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Denitrifying Bioreactor

Denitrifying Bioreactor

Photo by Louie, Ben and Blake

Denitrifying Bioreactor

Location: Tesdell Century Farm, South of Slater, IA
Featuring: Family Farmer Lee Tesdell

Helping nature break down nitrate in the soil, before it reaches waterways.

An edge of field structure, usually a subsurface trench containing a carbon source such as wood chips, that denitrifies subsurface agricultural drainage flows to reduce nitrate levels and improve water quality.

Step 1: Drainage Control Box – The tile water enters through the drainage control box, which offers a bypass if the water volume gets too high.

Step 2: Filtering – The water then filters through a bed of woodchips, colonized by naturally occurring bacteria. In the woodchips the bacteria catalyze a series of anaerobic reactions that break down and remove nitrates from the water, releasing nitrogen gas and small amounts of nitrous oxide.

Step 3: Drainage Control Box II – The water flows through a second box that can change the water level in the woodchip bed and flows out the tile outlet.

“I’m spending money most farmers wouldn’t."

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