Marsh-pond-marsh constructed wetland design analysis for swine lagoon wastewater treatment

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 have also 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 University research farm near Greensboro, NC. There were six wetland systems (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 30%; however, they were not as effective in the treatment of phosphorus (8%). Outflow concentrations were reasonably correlated (r(2) greater than or equal to 0.86 and r(2) greater than or equal to 0.83, respectively) to inflow concentrations and hydraulic loading rates for both total N and ammonia-N. The calculated first-order plug-flow kinetics model rate constants (K-20) for total N and ammonia-N (3.7-4.5 m/day and 4.2-4.5 m/day, respectively) were considerably lower than those reported in the limited literature and currently recommended for use in constructed wetland design for animal wastewater treatment. Published by Elsevier B.V.