Improving Denitrifying Woodchip Bioreactor Design and Management through Denitrification Potential Testing

Denitrifying woodchip bioreactors promote biological removal of nitrate to prevent negative environmental consequences of nitrate loading to downstream waters. Bioreactor media should promote complete denitrification while maintaining high rates favorable for nitrate removal. Considering woodchip type, oak had the highest denitrification potential, which also corresponded to the most nitrate removal in lab studies. The overall proportion as N2O was low for all submerged woodchips (<14%), suggesting that woodchips generally have high potential for complete denitrification. There were higher denitrification potentials when carbon was added, suggesting that some bioreactors may experience carbon limitations. Without exposure to drainage water, fresh woodchips were capable of denitrification, albeit at a much lower rate than active or spent woodchips harvest from an operational bioreactor in the field. This demonstrates that denitrifying organisms are present in woodchip media prior to installation in bioreactors. Overall, woodchip type and properties should be an additional consideration for bioreactor design and construction, but this needs to be contextualized within practical factors such as woodchip availability and cost. In addition, field conditions are known to influence performance and N2O proportions should be monitored over time to ensure bioreactors are reaching optimal performance.

  • PI: Laura Christianson
  • PI Institution: University of Illinois
  • June 18, 2019 – December 31, 2020