Increasing Tile Drainage Nitrate Removal in Bioreactors By Treating More Water.

Denitrifying woodchip bioreactors are sized to treat a portion of subsurface drainage system peak flow, so during larger events substantial bypass flow remains untreated. Over sizing bioreactors to capture a higher portion of peak flow can create conditions under which unintended consequences could occur. Conversely, under sizing them results in lost opportunity to treat water. A potential solution for treating additional water is to use a cascading series of bioreactor cells that come on line as overflow is initiated from the previous cell. A large, three-cell bioreactor of the described design has been engineered, installed, and operated in southern Minnesota on a 266-ha watershed. This presentation will highlight the instrumentation and early flow and water quality results from the first year of operation.