title: Temperature, plant species and residence time effects on nitrogen removal in model treatment wetlands.
abstract: Total nitrogen (TN) removal in treatment wetlands (TWs) is challenging due to nitrogen cycle complexity and the variation of influent nitrogen species. Plant species, season, temperature and hydraulic loading most likely influence root zone oxygenation and appurtenant nitrogen removal, especially for ammonium-rich wastewater. Nitrogen data were collected from two experiments utilizing batch-loaded (3-, 6-, 9- and 20-day residence times), sub-surface TWs monitored for at least one year during which temperature was varied between 4 and 24 °C. Synthetic wastewater containing 17 mg/l N as NH4 and 27 mg/l amino-N, 450 mg/l chemical oxygen demand (COD), and 13 mg/l SO4-S was applied to four replicates of Carex utriculata, Schoenoplectus acutus and Typha latifolia and unplanted controls. Plant presence and species had a greater effect on TN removal than temperature or residence time. Planted columns achieved approximately twice the nitrogen removal of unplanted controls (40-95% versus 20-50% removal) regardless of season and temperature. TWs planted with Carex outperformed both Typha and Schoenoplectus and demonstrated less temperature dependency. TN removal with Carex was excellent at all temperatures and residence times; Schoenoplectus and Typha TN removal improved at longer residence times. Reductions in TN were not accompanied by increases in NO3, which was consistently below 1 mg/l N.
authors: Department of Civil Engineering, Montana State University, Bozeman, MT, 59717, USA E-mail: ottos@ce.montana.edu; Center for Biofilm Engineering, Montana State University, Bozeman, MT, 59717, USA.
authors: C R
authors: CR
authors: Allen
authors: Department of Civil Engineering, Montana State University, Bozeman, MT, 59717, USA E-mail: ottos@ce.montana.edu; Center for Biofilm Engineering, Montana State University, Bozeman, MT, 59717, USA.
authors: O R
authors: OR
authors: Stein
authors: Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, 59717, USA and Intermountain Aquatics, Inc. Driggs, ID, 83422, USA.
authors: P B
authors: PB
authors: Hook
authors: Center for Biofilm Engineering, Montana State University, Bozeman, MT, 59717, USA.
authors: M D
authors: MD
authors: Burr
authors: Center for Biofilm Engineering, Montana State University, Bozeman, MT, 59717, USA.
authors: A E
authors: AE
authors: Parker
authors: Department of Civil Engineering, Montana State University, Bozeman, MT, 59717, USA E-mail: ottos@ce.montana.edu.
authors: E C
authors: EC
authors: Hafla
mesh_terms: D031255:Carex Plant / Q000378:metabolism*; D009584:Nitrogen / Q000302:isolation & purification* / Q000378:metabolism; D013696:Temperature; D032401:Typhaceae / Q000378:metabolism*; D018508:Water Purification; D053833:Wetlands
chemical_list: D009584:Nitrogen