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Item Influence of saturation on denitrification in a two-stage, vertical flow treatment wetland at Bridger Bowl ski area(Montana State University - Bozeman, College of Engineering, 2018) Woodhouse, Shayla Lee; Chairperson, Graduate Committee: Otto SteinA full-scale two-stage vertical flow treatment wetland (VF TW) pilot system was installed at the Bridger Bowl Ski Area in 2013 to test its capability as a secondary wastewater treatment system. Water quality was monitored throughout the 2015-2016 and 2016-2017 ski seasons with the primary objective to optimize the system for total nitrogen removal. Eight different combinations (schemes) of daily hydraulic and nutrient loading, dose frequency, effluent recycle, and depth of saturation of the first stage were tested. Average system removal was 93% and 95% for chemical oxygen demand (COD) and 70% and 75% for total nitrogen (TN) in 2016 and 2017, respectively, despite elevated influent concentrations of 930 mg x L -1 COD and 195 mg x L -1 TN. In addition, the system converted virtually all influent TN to nitrate. Both 1:1 and 2:1 (recycle to influent) ratios were effective as were saturation depths of 53 and 71 cm. At the 2:1 recycle ratio, the higher saturation level was superior at light hydraulic and constituent mass loadings while the lower saturation level was superior at higher loadings, but the differences were small. Overall, TN removal and nitrogen species transformations were linearly related to the mass load applied (surface area basis) over the range evaluated. In addition, the maximum removal capacity of the system was not exceeded during any scheme, thus the inherent removal capacity of the system is greater than evaluated. Nevertheless, the removal efficiencies of the VF TW from the past two seasons has shown that this technology can successfully perform secondary wastewater treatment in cold climates with efficient nitrogen removal and can exceed the regulatory requirements under which Bridger Bowl operates.Item Nitrogen removal and associated greenhouse gas production in laboratory-scale treatment wetlands(Montana State University - Bozeman, College of Engineering, 2016) Allen, Christopher Robert; Chairperson, Graduate Committee: Otto Stein; Mark D. Burr, Anne K. Camper, Jefferson J. Moss and Otto R. Stein were co-authors of the article, 'Plant influence on denitrification in treatment wetlands' submitted to the journal 'Water research' which is contained within this thesis.; Mark D. Burr, Anne K. Camper, Jefferson J. Moss and Otto R. Stein were co-authors of the article, 'Influence of plants and organic carbon addition on greenhouse gas emissions from model treatment wetlands' submitted to the journal 'Environmental science and technology' which is contained within this thesis.; Otto R. Stein was a co-author of the article, 'Empirical modeling of plant influence and organic carbon addition on nitrogen removal in treatment wetlands' submitted to the journal 'Ecological engineering' which is contained within this thesis.Treatment wetlands (TWs) are designed to treat domestic wastewater and water polluted from non-point sources such as agricultural runoff. Because many recent design improvements have increased aerobic removal pathways, nearly complete removal of biological oxygen demand (BOD) and oxidation of ammonium to nitrate in domestic wastewater is possible. These improvements have come at the expense of reducing the TW capacity to remove nitrate. Nitrate is also a main pollutant of concern in many non-point pollution sources. Organic carbon (OC) is a limiting factor for microbial nitrate removal and in wetlands can be supplied externally or provided by plants. Nitrate removal has the potential to release greenhouse gases (GHG) resulting in TWs being capable of acting as a net source or sink for GHG. Increasing our understanding of nitrogen removal and GHG production in TWs is the overarching goal of this project. A multi-year controlled environment greenhouse study measured water quality within 15-day incubations over annual cycles of temperature as well as greenhouse gas production at the seasonal extremes of the annual cycle. The experiment consisted of microcosms planted with either Carex utriculata, Deschampsia cespitosa, Phragmites australis, Schoenoplectus acutus, Typha latifolia or left unplanted. The fully factorial experiment also included three levels of OC addition, ranging from zero to two times the stoichiometric equivalent required for complete nitrogen removal. Nitrogen removal was affected by all experimental factors; plant species, OC addition, and temperature, with plant species mediating the effects of carbon and temperature in some treatments. The three highest performing species, C. utriculata, P. australis and S. acutus, removed nitrogen at an annual rate exceeding 166 g m -2 yr -1, without OC; only C. utriculata showed less N removal in winter. Incubation time series analysis indicated greater total and seasonal removal capacity for these plant treatments. Total GHG emission was dominated by summer CO 2 emission and varied by plant treatment and carbon load. CO 2 emission correlated negatively with OC addition in the high performing species attributable to plant biomass that decreased with OC addition. N 2O production significantly increased with the addition of organic carbon and did not vary significantly by season.