METHODS FOR REMOVING NITRATE NITROGEN FROM AGRICULTURAL DRAINAGE WATERS: A REVIEW AND ASSESSMENT

Authors: Appelboom, Timothy; Fouss, James

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 3/7/2006
Publication Date: 7/12/2006
Citation: Appelboom, T.W., Fouss, J.L. 2006. Methods for Removing Nitrate Nitrogen from Agricultural Drainage Waters: A Review and Assessment. Presented at the Proceedings of the American Society of Agricultural and Biological Engineers International Meeting, ASABE, St. Joseph, Mich., in Portland, Oregon, July 9-12, 2006. Paper No. 062328.

Interpretive Summary: Conventional surface and subsurface drainage have resulted in increased nitrate losses from agricultural croplands to surface waters. A number of approaches have been identified to reduce nitrate losses carried off cropland in surface and subsurface drainage. These include; controlled-drainage (that is, restrictig drainage at selected annual seasons such as during the winter, non-cropping months), diverting or directing drainage discharge through natural or constructed wetlands, bioreactors, zones that surround or border the drain pipes, and in-stream denitrification. Potential nitrate reductions for each of these methods are approximately 50% for controlled-drainage, 37% to 65% for natural/constructed wetlands, 60% to 90% for bioreactors, and 1% to 60% for in-stream denitrification. Combinations of these methods would lead to even higher nitrate removal. A combination of controlled-drainage, constructed wetland and in-stream denitrification could result in approximately 76% nitrate removal, thus significantly reducing water quality degradation in downstream flow.

Technical Abstract: Widespread adoption of conventional surface and subsurface drainage has resulted in increased nitrate losses from agricultural cropland to surface waters. This is due to the drainage water bypassing nutrient removing landscape features (i.e. riparian buffers and wetlands as it moves from the fields to the stream). A number of approaches have been identified to reduce these nitrate losses including controlled-drainage, routing of drainage water through natural/constructed wetlands and through constructed bioreactors, and in-stream denitrification. Controlled-drainage and infield bioreactors reduce the loss carried off field in drainage discharge, whereas natural/constructed wetlands and in-stream denitrification are post-drainage methods of nitrate reduction. The potential for nitrate reduction with each of these approaches is; approximately 50% for controlled drainage, 37% to 65% for natural/constructed wetlands (with up to an additional 18% if a berm is used in creation of the wetland), 60% to 90% for constructed bioreactors, and 1% to 66% for in-stream denitrification. Combinations of these methods would lead to even higher nitrate removal. A combination of controlled-drainage, constructed wetland and in-stream denitrification could possibly result in more than 75% nitrate removal, thus significantly reducing water quality degradation in downstream flow.