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Denitrifying ‘Woodchip’ Bioreactor Projects

While in-field practices such as 4Rs nitrogen management and cover crops will be vital to meeting agricultural water quality goals, as substantial investments in drainage systems continue to be made, edge-of-field practices like bioreactors will also be a necessary part of the solution. Inside a bioreactor, provision of a solid organic carbon source in addition to maintenance of anoxic conditions allows the natural process of denitrification to be enhanced, meaning waters leaving these treatment systems have significantly reduced nitrate loads.


Simply put, denitrifying bioreactors are trenches, generally filled with woodchips, through which tile drainage water is routed. This simple “water cleaning” system typically removes approximately 25-45% of the annual nitrate load leaving a field. (Image credit: Christianson and Helmers, 2011; Iowa State University Extension and Outreach PMR 1008)

Bioreactors for Illinois: Smaller, Better, Faster

High flow booster_edited_1

Considering the scale of new water quality goals, there is an increasing need to design bioreactors to remove nitrate more effectively under both high and low flow rates, from cool early-season drainage, and with a smaller bioreactor footprint. The goal of this work is to test novel full-size bioreactor designs intended to maximize nitrogen removal while limiting land removed from production. Four novel bioreactors will be designed, built, and monitored: two for treatment of ditch drainage (“Ditch Bioreactors”), one will include a step-feeding system for high flows (“High-Flow Booster Bioreactor”), and one will take advantage of solar heating to better treat low temperature drainage water (“Heat-enhanced Bioreactor”).

Funding Partner: Illinois Nutrient Research & Education Council
Co-PI: Dr. Richard Cooke, Biological & Agricultural Engineering, University of Illinois (L. Christianson, Lead PI)


Transforming Denitrifying Bioreactor Research and Applications: Unveiling the Inside of the Black Box

webpage_trial2Widespread denitrifying ‘woodchip’ bioreactor implementation is needed to significantly decrease nitrate loads on a regional scale, and the major technical and financial tasks that this entails demand that we transform our approach to their research, design and management to optimize nitrate removal. Bioreactors can no longer be assumed to be ‘black boxes’ under this new, bold way of thinking. We propose a laboratory, field and modeling study to provide novel science-based tools and guidelines needed to improve, optimize and maintain removal efficacy of existing and future bioreactors. For the first time, we will open the bioreactor ‘black box’ using state of the art continuous sensors for water quality and gases to disentangle and quantify the tightly coupled hydraulic and biochemical processes inside.

Funding Partner: USDA NIFA Foundational Program
Lead PI: Dr. François Birgand, Biological & Agricultural Engineering, North Carolina State University (L. Christianson, IDROP Co-PI)


 Enhanced Denitrification Technologies for for the Delmarva Peninsula

08_01_Initial gravel placement (93)Woodchip denitrifying bioreactors have gained much attention and acceptance over the past decade for treatment of nitrate in subsurface tile drainage. There may be the potential for such enhanced denitrification systems to have wider applicability by, for example, rethinking the carbon source or retrofitting the design to provide treatment of drainage in agricultural ditches. This project developed and evaluated a variety of novel bioreactor designs for the Delmarva Peninsula.

Funding Partner: USDA NRCS Consevation Innovation Grant
Lead PI: Dr. Zach Easton, Department of Biological Systems Engineering, Virginia Tech
Collaborators: Drs. Peter Kleinman and  Ray Bryant, USDA ARS; Dr. Arthur Allen, University of Maryland Eastern Shore; L. Christianson, UIUC