Efficacy of a denitrification wall to treat continuously high nitrate loads

 

Situation: Denitrification walls (wood chip bioreactors) can be an effective long-term method for reducing high nitrogen (N) concentrations in groundwater below agricultural fields. Denitrification walls may be more effective if they were sited in areas of high groundwater flow where large, targeted portions of agricultural effluent is discharged. 

 

Actions: Researchers from the University of Florida installed a denitrification wall adjacent to a 65 ha container nursery in Alachua, Florida. The wall was placed next to a break in surface elevation where large volumes of N-containing groundwater from the nursery was discharged as surface water seepage. The purpose of the study was to evaluate the efficacy of a denitrification wall receiving continuously high nitrate-N loads. 

 

Take-home message: wall construction

  • Placing the wall by a rapid-flow aquifer allowed for a large reduction of total nitrogen load.
  • Nitrogen was rapidly removed in only a fraction of the wall width, showing that a greater volume of water could have been treated by using a thinner wall over a longer length.
  • The larger wall provides a greater carbon pool which increases the longevity of the wall.
  • Denitrification walls can maintain high N removal rates in groundwater with high velocity.

 

For more information: