Bioreactors are essentially subsurface trenches filled with a carbon source, mainly wood chips, through which water is allowed to flow just before leaving the drain to enter a surface water body. The carbon source in the trench serves as a substrate for bacteria that break down the nitrate through denitrification or other biochemical processes. Bioreactors provide many advantages:
How do bioreactors work? Organisms from the soil colonize the woodchips. Some of them break down the woodchips into smaller organic particles. Others “eat” the carbon produced by the woodchips, and “breathe” the nitrate from the water. Just as humans breathe in oxygen and breathe out carbon dioxide, these microorganisms breathe in nitrate and breathe out nitrogen gas, which exits the bioreactor into the atmosphere. Through this mechanism, nitrate is removed from the tile water before it can enter surface waters.
Interactive routine that can be used to determine size, cost and evaluate performance of a bioreactor installed in a field with a specified soil and county in Illinois: http://www.wq.illinois.edu/dg/Equations/Bioreactor.exe.More
Denitrifying Bioreactors are eligible for financial assistance through the NRCS Environmental Quality Incentives Program, Where the conservation practice standard has been accepted, financial assistance is often available through EQIP. In Indiana, the incentive is $5800. Incentives in IowaMore
Bioreactors can greatly reduce nitrate loads from tile drainage systems, with the amount depending on residence time and the proportion of drain flow that flows through the bioreactor. A typical design goal is 30-50% of the total nitrate load.More