Submitted to: Ecological Engineering
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/26/2004
Publication Date: 12/1/2004
Citation: Stone, K.C., Poach, M.E., Hunt, P.G., Reddy, G.B. 2004. Marsh-pond-marsh constructed wetland design analysis for swine lagoon wastewater treatment. Ecological Engineering. 23:127-133. Interpretive Summary: In the eastern Coastal Plain and during the past decade, there has been a large increase in animal production. This increase in animal production has led to additional environmental concerns because of the large amount of waste produced by these animal production facilities. These animal wastes must be treated in an environmentally sustainable manner. Traditional treatment methods need to be enhanced or replaced to prevent adverse impacts on the surrounding streams and ground water. One alternative to enhance treatment is the use of constructed wetlands. Constructed wetlands have been used for many years in municipal wastewater treatment. A constructed wetland with marshes on each end and an open water section in the middle was built at the North Carolina A&T State University swine farm in 1995 to treat swine lagoon effluent. In this study, we evaluated how well this constructed wetland treated various amounts of the lagoon effluent from September 2000 to September 2001. We found that these constructed wetlands were somewhat effective in treating nitrogen. We then analyzed the results with the equations that engineers and consultants use in designing similar wetlands. These design equation results can be used by engineers and consultants in the future to construct and improve similar wetland systems.
Technical Abstract: Constructed wetlands have been identified as a potentially important component of animal wastewater treatment systems. Continuous marsh constructed wetlands have been shown to be effective in treating swine lagoon effluent and reducing the land needed for terminal application. Constructed wetlands also have been used widely in polishing wastewater from municipal systems. Constructed wetland design for animal wastewater treatment has largely been based on that of municipal systems. The objective of this research was to determine if a marsh-pond-marsh wetland system could be described using existing design approaches used for constructed wetland design. The marsh-pond-marsh wetlands investigated in this study were constructed in 1995 at the North Carolina A&T State University research farm. There were six wetland cells (11 m x 40 m). The first 10 m was a marsh followed by a 20-m pond section followed by a 10-m marsh planted with bulrushes and cattails. The wetlands were effective in treating nitrogen with mean total nitrogen and ammonia-N concentration reductions of approximately 33%; however, they were not effective in the treatment of phosphorus. Outflow concentrations were reasonably correlated (r2 0.82 and r2 0.79, respectively) to inflow concentration and hydraulic loading rate for both total N and ammonia-N. Our calculated first-order plug-flow kinetics model rate constants (K20) for total-N and ammonia-N (4.5-6.0 and 5.4-6.2, respectively) were considerably lower than those reported in the limited literature and currently recommended for use in constructed wetland design.