Denitrification in constructed wetlands used for treatment of swine wastewater

• Published in: Journal of environmental quality 2003-03, Vol.32 (2), p.727-735
• Main Authors: Hunt, Patrick G, Matheny, Terry A, Szogi, Ariel A
• Format: Article
• Language: English
• Subjects: acetylene; animal manure management; Animal wastes; Animals; Applied sciences; Aquatic plants; Artificial wetlands; Biodegradation, Environmental; Biological and medical sciences; Biological treatment of waters; Biotechnology; carbon; constructed wetlands; Denitrification; Ecosystem; Environment and pollution; Enzymatic activity; enzyme activity; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; Juncus effusus; nitrogen; Nitrogen - metabolism; Other wastewaters; pig manure; Plant communities; Poaceae; Pollution; pollution load; Schoenoplectus; Schoenoplectus americanus; Schoenoplectus tabernaemontani; Scirpus; Scirpus cyperinus; Sparganium; Sparganium americanum; Swine; Typha angustifolia; Typha latifolia; Waste Disposal, Fluid; wastewater treatment; Wastewaters; Water depth; Water Purification - methods; Water treatment and pollution; wetland plants; wetland soils
• ISSN: 0047-2425; 1537-2537; 1537-2537
• DOI: 10.2134/jeq2003.0727

Constructed wetland treatment of swine wastewater probably involves substantial denitrification. Our objective was to assess denitrification and denitrification enzyme activity (DEA) in such wetlands in relation to plant communities, N loading, carbon or nitrogen limitations, and water depth. Two wetland cells each 3.6 m wide and 33.5 m long were connected in series. One set of cells was planted with rushes and bulrushes, including soft rush (Juncus effusus L.), softstem bulrush [Schoenoplectus tabernaemontani (K.C. Gmel.) Palla], American bulrush [Schoenoplectus americanus (Pers.) Volkart ex Schinz & R. Keller], and woolgrass bulrush [Scirpus cyperinus (L.) Kunth]. Another set was planted with bur-reeds and cattails, including American bur-reed (Sparganium americanum Nutt.), broadleaf cattail (Typha latifolia L.), and narrowleaf cattail (Typha angustifolia L.). The sets will be referred to herein as bulrush and cattail wetlands, respectively. Denitrification and DEA were measured via the acetylene inhibition method in intact soil cores and disturbed soil samples that were taken during four years (1994-1997). Although DEA in the disturbed samples was greater than denitrification in the core samples, the measurements were highly correlated (r2 >or= 0.82). The DEA was greater in the bulrush wetlands than the cattail wetlands, 0.516 and 0.210 mg N kg-1 soil h-1, respectively; and it increased with the cumulative applied N. The DEA mean was equivalent to 9.55 kg N ha-1 d-1 in the bulrush wetlands. We hypothesized and confirmed that DEA was generally limited by nitrate rather than carbon. Moreover, we determined that one of the most influential factors in DEA was wetland water depth. In bulrush wetlands, the slope and r2 values of the control treatment were -0.013 mg N kg-1 soil h-1 mm-1 depth and r2 = 0.89, respectively. Results of this investigation indicate that DEA can be very significant in constructed wetlands used to treat swine wastewater.