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Field Performance of Denitrifying Bioreactors in the Northeastern United States

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2016 10th International Drainage Symposium Conference, 6-9 September 2016, Minneapolis, Minnesota  .(doi:10.13031/IDS.20162493551)
Authors:   Bahareh Hassanpour, Shree K. Giri, William T. Pluer, Tammo S. Steenhuis, Larry D. Geohring
Keywords:   Biochar, Denitrifying bioreactor, Nitrate removal rate, Temperature, Tile drainage.

Abstract. Denitrifying bioreactors are increasingly being used for treating nitrate-rich agricultural drainage water. Filled with carbon substrates, often woodchips, denitrifying bioreactors provide a favorable environment for denitrification under anaerobic conditions. Despite several installations across the Midwestern United States, there have not been any field studies demonstrating and investigating the efficiency of denitrifying bioreactors in the northeastern United States which has cold winters and numerous relatively shallow sloping soils over glacial till. Thus, this study investigates the seasonal efficiency of denitrifying bioreactors in different landscapes throughout two years of application. Paired bioreactors (one filled with woodchips only and one filled with woodchips amended with biochar) were installed at three sites in upstate New York. Flow rate, temperature, nitrate (NO3–N), and dissolved organic carbon (DOC) were measured in the inflow and outflow water of the bioreactors. Results show the average reduction in NO3–N concentrations in the bioreactors ranged from 38 to 68%, with average removal rates ranging from 4 to 15 g N m-3d-1. The removal efficiency improved with increasing temperature, however, sporadic high flow events temporarily lowered NO3–N removal for a period afterwards. Bioreactors in the northeastern United States have potential to remove NO3–N from agricultural drains when soil temperatures are above 5°C. Below this temperature, DOC release and NO3–N removal are not optimal.

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