title: Oxygen fluxes and ammonia removal efficiencies in constructed treatment wetlands.
abstract: Ammonia-removal efficiency in constructed wetlands is often limited by the amount of oxygen available in the system. In this study, the oxygen-transfer rates to laboratory-scale, subsurface-flow and free-water-surface constructed wetlands were quantified for two input concentrations of ammonia, 10 and 50 mg nitrogen/L, both with and without Typha latifolia. Rates of oxygen diffusion into the subsurface-flow constructed wetlands were 6.01 to 7.92 g/m2 x d and were strongly correlated with ammonia concentration in the water. In contrast, low oxygen diffusion rates of 1.36 to 1.76 g/m2 x d were observed for the free-water-surface system. The presence of Typha latifolia had small but consistent effects on atmospheric oxygen-diffusion rates and ammonia-removal efficiencies in both the subsurface-flow and free-water-surface systems. The observed small effects were consistent with measurements of oxygen inputs from T. latifolia roots. Only approximately 0.023 g/m2 x d of oxygen was released from roots of T. latifolia, as measured using the titanium (III) citrate buffer method. The results for the ammonia-removal rates of the laboratory-scale constructed wetlands were further verified using pilot-scale constructed wetlands under greenhouse conditions.
authors.affiliation: Center for Earth and Environmental Science, Plattsburgh State University of New York, 12901, USA.
authors.forename: M Y
authors.initials: MY
authors.lastname: Wu
authors.forename: E H
authors.initials: EH
authors.lastname: Franz
authors.forename: S
authors.initials: S
authors.lastname: Chen
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001673:Biodegradation, Environmental; D004058:Diffusion; D017753:Ecosystem; D009584:Nitrogen / Q000378:metabolism*; D010100:Oxygen / Q000032:analysis* / Q000737:chemistry; D018517:Plant Roots / Q000502:physiology; D010944:Plants; D014872:Water Movements
chemical_list: D000641:Ammonia; D009584:Nitrogen; D010100:Oxygen