Further Research Efforts 



Research is continuing with the established wetland system. Presented data 

 represents several different operating temperatures. Data will be analyzed for the 

 development of temperature-dependent kinetic modeling. Research will also 

 focus on the development or application of models for evapotranspiration, as ET 

 has significant effects upon parameter concentrations and volume of wetland 

 effluent. Greater attention will additionally be paid to the study of the root zone 

 microcosm, including redox potential and oxygen transfer from plant roots to 

 biofilms. 



Summary and Conclusions 



Substantial reduction in COD has been observed from all three constructed 

 wetland treatments at two unique influent concentrations (Fig. 1). Nitrogen 

 removal has been far less dramatic and appears to be positively affected by the 

 presence of two plant species (Typha sp. and Scirpus sp.) (Fig. 2). Phosphate 

 removal is also positively affected by macrophytic plant species, especially during 

 active growth (Fig 3). Chemical reduction of sulfate to hydrogen sulfide appears 

 to be the primary transformation of oxygenated sulfur-containing compounds in 

 the wetland system. Influent COD concentrations of >150 mg/L appear to 

 facilitate this transformation in all treatments (Figs. 1 and 4). This transformation 

 did not take place in planted treatments when influent COD concentrations were 

 approximately 100 mg/L. Apparently the plants provide sufficient oxygen to 

 inhibit this reaction which provides evidence for the plant-mediated oxygenation 

 of the wetland environment. In general, plant effects appear to be correlated to 

 the season and growth status of the plant. These effects are thought to be 

 correlated to plant uptake of nutrients, oxygen transport into the root zone and to 

 other plant-microbial biofilm interactions. 



Acknowledgments 



This research has been made possible with grants from several sources 

 including; USGS Section 104, Montana Agricultural Experiment Station, NRI 

 Competitive Grants Program/USDA Grant #96-35102-3837, and USDI Bureau of 

 Reclamation Great Plains Regional Office. 



References 



Biederman, J. A. and O.R. Stein. 1997. Physical Modeling of Constructed 

 Wetlands for Wastewater Treatment. IN: Environmental and Coastal 

 Hydraulics: Protecting the Aquatic Habitat , Vol. 2 pp. 901-906. XXVII 

 Inter. Asso. Hydr. Res. Congress. San Francisco, Aug. 10-15, 1997. 



Stein, O.R. J. A. Biederman and P.B. Hook. 1998. Performance of Model 

 Wetlands for Wastewater Treatment. Accepted to the Eighth National 

 Symposium on Individual and Small Community Sewage Systems, 

 Orlando, FL. 



Stein et al 



