Michigan Technological University Digital Commons @ Michigan Tech Dissertations, Master's Theses and Master's Dissertations, Master's Theses and Master's Reports - Open Reports 2009 Nitrogen removal and sustainability of vertical flow constructed wetlands for small scale wastewater treatment Valerie J. Fuchs Michigan Technological University Follow this and additional works at: https://digitalcommons.mtu.edu/etds Part of the Environmental Engineering Commons Copyright 2009 Valerie J. Fuchs Recommended Citation Fuchs, Valerie J., "Nitrogen removal and sustainability of vertical flow constructed wetlands for small scale wastewater treatment", Dissertation, Michigan Technological University, 2009. https://doi.org/10.37099/mtu.dc.etds/730 Follow this and additional works at: https://digitalcommons.mtu.edu/etds Part of the Environmental Engineering Commons NITROGEN REMOVAL AND SUSTAINABILITY OF VERTICAL FLOW CONSTRUCTED WETLANDS FOR SMALL SCALE WASTEWATER TREATMENT By VALERIE J. FUCHS A DISSERTATION Submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY (Environmental Engineering) MICHIGAN TECHNOLOGICAL UNIVERSITY 2009 Copyright © Valerie J. Fuchs 2009 This dissertation, "Nitrogen Removal and Sustainability of Vertical Flow Constructed Wetlands for Small Scale Wastewater Treatment," is hereby approved in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in the field of Environmental Engineering. PROGRAM: Environmental Engineering Signatures: Dissertation Co-Advisor ________________________________________________ John S. Gierke Dissertation Co-Advisor ________________________________________________ James R. Mihelcic Program Chair ________________________________________________ Judith A. Perlinger Date ________________________________________________ ABSTRACT The challenge for wastewater professionals is to design and operate treatment processes that support human well being and are environmentally sensitive throughout the life- cycle. This research focuses on one technology for small-scale wastewater treatment: the vertical flow constructed wetland (VFCW), which is herein investigated for the capacity to remove ammonium and nitrate nitrogen from wastewater. Hydraulic regime and presence/absence of vegetation are the basis for a three-phase bench scale experiment to + determine oxygen transfer and nitrogen fate in VFCWs. Results show that 90% NH4 -N - removal is achieved in aerobic downflow columns, 60% NO3 -N removal occurs in anaerobic upflow columns, and 60% removal of total nitrogen can be achieved in downflow-upflow in-series. The experimental results are studied further using a variably saturated flow and reactive transport model, which allows a mechanistic explanation of the fate and transport of oxygen and nitrogen. The model clarifies the mechanisms of oxygen transport and nitrogen consumption, and clarifies the need for readily biodegradable COD for denitrification. A VFCW is then compared to a horizontal flow constructed wetland (HFCW) for life cycle environmental impacts. High areal emissions of greenhouse gases from VFCWs compared to HFCWs are the driver for the study. The assessment shows that because a VFCW is only 25% of the volume of an HFCW designed for the same treatment quality, the VFCW has only 25-30% of HFCW impacts over 12 impact categories and 3 damage categories. Results show that impacts could be reduced by design improvements. Design recommendations are downflow wetlands for nitrification, upflow wetlands for denitrification, series wetlands for total nitrogen removal, hydraulic load of 142 L/m2d, 30 cm downflow wetland depth, 1.0 m upflow wetland depth, recycle, vegetation and medium-grained sand. These improvements will optimize nitrogen removal, minimize gaseous emissions, and reduce wetland material requirements, thus reducing environmental impact without sacrificing wastewater treatment quality. iii ACKNOWLEDGEMENTS This research and my time at Michigan Technological University were financially supported by the National Science Foundation (NSF) Sustainable Futures IGERT grant at Michigan Technological University (DGE 0333401), the NSF Graduate Research Fellowship Program, the Water Environment Research Foundation (Project DEC11U06), the DeVlieg Foundation, the Michigan Water Environment Association, and Michigan Technological University in conjunction with the Department of Civil and Environmental Engineering, the Department of Geological and Mining Engineering and Sciences, the School of Forest Resources and Environmental Science, and the Graduate School. I appreciate the efforts of Noah Mirovsky, Ashley Vincent, Colin Casey, Austin Andrus and Lisa Weidemann in the laboratory; they willingly got their hands dirty to solve problems, collected quality data, and helped work through a research project that could not be done by one person. Thanks to Matt Seib who worked through an iteration of life cycle assessment with me. Many thanks to Dave Perram, Chris Wojick and Bob Barron who have my utmost respect for their analytical skills. I am thankful to the many professors and staff that have influenced my time, education, writing, ideas, research development, career development; this university has a truly outstanding group of employees who clearly care about the work, life and future of their students. I truly appreciate the input, advice and encouragement of my fellow graduate students on research and life topics. To each of you with whom I’ve shared an office, lab or house, thank you for your friendly presence! You kept me smiling and laughing. Very much thanks to each of the friends I’ve made over the last five and a half years! You’ve opened my eyes to so many new ideas and experiences, and to the value of friendships near and far. I hope that we will be a community for many, many years to come. iv I am so grateful to my family for having supported me from afar, for coming to visit me, for understanding how much I have loved my work, this place, and the people here. Mom and Dad, I can never express how much I appreciate you. I appreciate my committee members, Dr. John S. Gierke (Geological and Mining Engineering and Sciences), Dr. James R. Mihelcic (University of South Florida Civil and Environmental Engineering), Dr. Thomas G. Pypker (School of Forest Resources and Environmental Science), Dr. John W. Sutherland (Purdue University Division of Environmental and Ecological Engineering), and Dr. Qiong Zhang (University of South Florida Civil and Environmental Engineering) for their input into and review of this research. To my advisors, I am incredibly indebted. I have been so blessed as to have amazing and rigorous advising, mentoring, career training, and care from not one, but two. Jim, you helped me open a door into putting sustainability to work in research and in life, and you’ve become a true friend. Thank you and Karen for your care, guidance and humor. John, I could write a whole other dissertation on the many things I’ve learned from you. They have to do with enjoying friendship and time, family, fishing, solving big and little problems, and laughing a lot. Thanks so much to you and your family for befriending me. v TABLE OF CONTENTS LIST OF TABLES .................................................................................................................................... viii LIST OF FIGURES .....................................................................................................................................ix 1. INTRODUCTION ............................................................................................................................... 1 1.1. RESEARCH HYPOTHESES ............................................................................................................... 4 1.2. RESEARCH OBJECTIVES ................................................................................................................ 5 1.3. DISSERTATION FRAMEWORK ........................................................................................................ 5 1.4. REFERENCES ................................................................................................................................. 7 2. CONSTRUCTED WETLANDS AND NITROGEN REMOVAL ................................................. 10 2.1. BACKGROUND ............................................................................................................................. 10 2.1.1. Constructed Wetlands for Wastewater Treatment ................................................................. 10 2.1.2. Flow regime in constructed wetlands .................................................................................... 11 2.1.3. Vegetation impact .................................................................................................................. 13 2.1.4. Oxygen transport ................................................................................................................... 14 2.1.5. Nitrification ........................................................................................................................... 14 2.1.6. Denitrification ....................................................................................................................... 15 2.1.7. Total nitrogen removal .......................................................................................................... 16 2.1.8. Conclusion of literature review ............................................................................................