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Optimization of Denitrifying Bioreactor Performance

Optimization of Denitrifying Bioreactor Performance with Agricultural Residue-Based Filter Media

The Agricultural Utilization Research Institute (AURI), in partnership with USDA-Agricultural Research Service (USDA-ARS), Minnesota Corn Research & Promotion Council (MCRPC) and the University of Minnesota (U of M) are pleased to announce the release of a new study, titled “Optimization of Denitrifying Bioreactor Performance with Agricultural Residue-Based Filter Media.”

The study examined the performance of agriculturally‐derived residue materials in denitrifying bioreactors. The report describes experimentation conducted by USDA‐ARS to measure nitrate removal, microbial abundance and dissolved nitrous oxide gas, comparing wood chips with stover, straw and corn cobs. These are important measures because nitrate‐nitrogen loss via drainage water is a widely concerning topic for farmers and agricultural communities. This study shows promise in reducing the size of bioreactors and lowering their costs via agricultural residue‐based materials.

Utilization of these agricultural residue-based materials showed a potential benefit to Minnesota economic/environmental development. Given the greater nitrate-N removal rates of agricultural residues, there may be opportunities to reduce the size of the bioreactor unit, or to increase nitrate-N removal effectiveness within a given bioreactor footprint. Also, the proximity of agricultural residues to an edge-of-field bioreactor is a significant incentive to design a way to use them successfully.

The study also indicated a potential for reduced cost of implementation and maintenance of bioreactors using residue-based materials. In comparing the costs for installation of a denitrifying bioreactor designed to treat 50 acres, the study found that installation costs of a residue-based reactor may be 70% of those experienced when installing a traditional wood-based bioreactor.

While not ready for wide‐scale adopon, the research is promising. The results have also since informed two additional research efforts to increase the rate of nitrate‐N removal in Minnesota tile drainage water. An additional column experiment, funded by the Minnesota Department of Agriculture, was also conducted by a Master of Science (M.S.) student at the University of Minnesota using three treatments that included corn cobs and three that used wood chips. In order to enhance the rate of removal of nitrate-N from tile drainage water in a field setting in southwestern Minnesota, the study further combined the findings from this additional column experiment with those of the present experiment. Thus, the impact of the relatively modest project that is the subject of this report has continued well beyond the project’s scope.

To download a copy of the study, click here.

Additional published articles about this study can be found at: