Research reports

Mid-Project Preliminary Research Report: Optimization of denitrifying bioreactor performance with agricultural residue-based filter media

Read the Mid-Project Preliminary Research Report: Optimization of denitrifying bioreactor performance with agricultural residue-based filter media

About This Report

Wood-chip denitrifying bioreactors are one promising technology to mitigate subsurface drainage nitrate-N losses. Drainage water is routed through these denitrifying bioreactors, where anaerobic microbes reduce nitrate-N to nitrogen gas that ultimately escapes to the atmosphere. We seek to demonstrate that agricultural residue-based materials (e.g., stover, straw, cobs) used as filter media can improve the performance and decrease the size of bioreactors, and potentially lower their cost.  Additionally, a large fraction of annual subsurface drainage and nitrate-N loss occurs during the spring snowmelt when soil temperatures are just above freezing (Jin and Sands, 2003). The cold temperatures tend to reduce microbial activity and negatively affect reactor efficiency. We propose to test the cold-temperature effectiveness of bioreactors with agricultural residue-based materials, in which the carbon is more labile than in wood chips.

Project Objectives

  1. Identify agriculturally derived materials that will maintain required hydraulic properties in a bioreactor.
  2. Improve the nitrate-N removal rate of bioreactors using agriculturally derived materials rather than wood chips, including at temperatures just above freezing.
  3. Investigate the cost for bioreactors using agriculturally derived materials and compare to the cost for wood chip bioreactors.

Partners

A special thanks to the Minnesota Corn Research & Promotion Council for their funding support of this project.