Substrate Organic Matter to Improve Nitrate Removal in Surface‐Flow Constructed Wetlands

• Published in: Journal of Environmental Quality
• Main Authors: Burchell, Michael R., Skaggs, R. Wayne, Lee, Charles R., Broome, Steven, Chescheir, George M., Osborne, Jason
• Other Authors: USACE Engineering Research and Development Center, USDA-NRI
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2007
• Subjects: Eagle Island
• Online Access: http://dx.doi.org/10.2134/jeq2006.0022; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2134%2Fjeq2006.0022; http://onlinelibrary.wiley.com/wol1/doi/10.2134/jeq2006.0022/fullpdf

ABSTRACT A wetland mesocosm experiment was conducted in eastern North Carolina to determine if organic matter (OM) addition to soils used for in‐stream constructed wetlands would increase NO 3 − –N treatment. Not all soils are suitable for wetland substrate, so OM addition can provide a carbon and nutrient source to the wetland early in its development to enhance denitrification and biomass growth. Four batch studies, with initial NO 3 − –N concentrations ranging from 30 to 120 mg L −1 , were conducted in 2002 in 21 surface‐flow wetland mesocosms. The results indicated that increasing the OM content of a Cape Fear loam soil from 50 g kg −1 (5% dry wt.) to 110 g kg −1 (11% dry wt.) enhanced NO 3 − –N wetland treatment efficiency in spring and summer batch studies, but increases to 160 g kg −1 (16% dry wt.) OM did not. Wetlands constructed with dredged material from the USACE Eagle Island Confined Disposal Facility in Wilmington, NC, with initial OM of 120 g kg −1 (12% dry wt.), showed no improvement in NO 3 − –N treatment efficiency when increased to 180 g kg −1 (18% dry wt.), but did show increased NO 3 − –N treatment efficiency in all batch studies when increased to 220 g kg −1 (22% dry wt.). Increased OM addition and biosolids to the Cape Fear loam and dredged material blends significantly increased biomass growth in the second growing season when compared to no OM addition. Results of this research indicate that increased OM in the substrate will reduce the area required for in‐stream constructed wetlands to treat drainage water in humid regions. It also serves as a demonstration of how dredged material can be used successfully in constructed wetlands, as an alternative to costly storage by the USACE.