Bacteria-Coated Corncob Bioreactors to Mitigate Nitrate Pollution

Mitigating Agricultural Drainage and Urban Stormwater

End-of-the-pipe denitrification bioreactors are a promising approach to treat and improve the water quality of subsurface drainage. Denitrification bioreactors are trenches filled with woodchips or other media that serve as substrates for microbial denitrification. 

However, there are some challenges associated with this process. The nitrate removal efficiency of woodchip bioreactors can be limited when the water temperature is low, the process can emit nitrous oxide, and there are high material and construction costs.

Corncobs, an agricultural byproduct easily available to farmers in Midwestern states, have emerged as a viable solution to this sustainability challenge while offering added benefits. Studies have shown that corncob-filled bioreactors achieve significantly higher nitrate removal rates under cold conditions compared to their woodchip counterparts and can improve bioreactor cost-effectiveness. 

This study proposes an innovative inoculation strategy to overcome challenges associated with corncob bioreactors.

Project Goals

• Develop laboratory-scale up-flow corncob bioreactors and measure for nitrate removal and nitrous oxide emission

• Improve performance of the bioreactors, with a goal to achieve >80 percent nitrate load reduction with no or negligible emission of nitrous oxide

• Examine the corncob degradation products

• Conduct outreach to to disseminate bioreactor technology through University of Minnesota Extension and MN Stormwater Research Council