Iowa State University Pilot Tests

 

Situation:  Denitrifying bioreactors hold great promise to reduce nitrogen (N) loads to streams in tile-drained agricultural settings.  One design challenge of these bioreactors is to balance the ability to treat substantial volumes of drainage flow and still maintain sufficient retention time for N transformations to take place over a range of temperatures and flow rates.

 

Actions:  Researchers at Iowa State University examined the impact of bioreactor geometry, storm flows and nitrate-N concentration on N reduction in a series of pilot-scale bioreactors in tile drained agricultural settings with local hardwood woodchips.

 

Take-home message: 

• Retention times of 4-8 hrs in a bioreactor can yield 30-70% N reduction from tile drainage waters.
• Design-estimated retention times under-estimated field observations, probably due to nonideal flow resulting from the design of the pipes within system.   
• Stay tuned for more information on revisions in bioreactor size recommendations.   

 

For more information:

• Christianson et al. 2011.  Pilot-scale evaluation of denitrification drainage bioreactors: Reactor geometry and performance.  Journal of Environmental Engineering 137.

• Email Dr. Laura Christianson at lauraechristianson@gmail.com, Dr. Matthew Helmers at mhelmers@iastate.edu, or Dr. Alok Bhandari at bhandari@ksu.edu