Assessing denitrification rate limiting factors in a constructed wetland receiving landfill leachate

The focus of this research was to investigate denitrification in constructe d wetlands to improve the nitrogen treatment capabilities of these systems. A free water surface flow constructed wetland located at the New Hanover C ounty Solid Waste Management Facility, near Wilmington, North Carolina, USA , was used for this research. Field water sampling in conjunction with a la boratory acetylene block method was used to quantify nitrogen removals in t he wetland. Background denitrification rates as well as potential denitrifi cation rates using sodium acetate and sodium phosphate were measured in the laboratory. According to field measurements, average nitrate nitrogen load ing and removal rates in the constructed wetland during 1997 were 11.1 +/- 3.4 g N/m(3)/d and 4.5 +/- 2.2 g N/m(3)/d, respectively. Denitrification ra tes measured in the laboratory with the addition of sodium acetate were hig her than background denitrification rates while the addition of sodium phos phate had no effect on the denitrification rates. Results suggested denitri fication in the wetland was limited by the availability of easily degradabl e sources of organic carbon. Background denitrification rates measured usin g the laboratory method were comparable to the nitrate nitrogen removal rat es measured by field water sampling. (C) 1999 IAWQ Published by Elsevier Sc ience Ltd. All rights reserved.