A Dissertation entitled Life Cycle Assessment of Rainwater Harvesting Systems at Building and Neighborhood Scales and for Various Climatic Regions of the U.S. by Jay P. Devkota Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Engineering Dr. Defne Apul, Committee Chair Dr. Steven Burian, Committee Member Dr. Ashok Kumar, Committee Member Dr. Cyndee Gruden, Committee Member Dr. Youngwoo Seo, Committee Member Dr. Patricia R. Komuniecki, Dean College of Graduate Studies The University of Toledo December 2015 Copyright 2015, Jay P. Devkota This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of Life Cycle Assessment of Rainwater Harvesting Systems at Building and Neighborhood Scales and for Various Climatic Regions of the U.S. By Jay P. Devkota Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Civil Engineering The University of Toledo December 2015 Rainwater harvesting can be a strategy to address challenges with urban water and wastewater infrastructure such as leakage, underfunding energy usage and combined sewer overflow. Rainwater harvesting system has been used for centuries to meet urban water demands such as toilet flushing, lawn irrigation, cleaning and recreational activities. Of these uses of harvested rainwater, toilet flushing is more common as it constitutes a higher percentage of indoor water use. Life cycle assessment is becoming a powerful tool to estimate environmental sustainability of rainwater harvesting systems. With growing interest in rainwater harvesting systems, it is now essential to understand and estimate the factors affecting its environmental sustainability to better design the system as well as to provide a framework for future researchers. Three research needs were identified and addressed in this study. Knowing that the prior studies lacks generalization of results to other cases, a water demand to supply ratio (D/S) ratio was proposed and demonstrated to estimate environmental impacts from rainwater harvesting systems. A decision framework was also proposed based on the result to help designers and practitioners estimate the environmental impacts without much effort. This study hypothesized that there is a lack of iii consistency in the analysis of rainwater harvesting systems. Supply and demand based approach was compared for rainwater harvesting system at ten climatic regions with one cubic meter of rainwater supplied and sanitation service in the building throughout its life time as respective functional units. Unexpectedly, the result showed that the region with lower environmental impact for one functional unit did not necessarily have lower impacts for the other functional unit making it clear that regional preference for rainwater harvesting system depends on the specific goal to be met: using harvested rainwater as a potential supplemental source versus using it to meet the water demand needs. Implementation of rainwater harvesting system also depends on the scale of its implementation. A suburban neighborhood was selected to demonstrate the environmental sustainability of different rainwater harvesting implementation strategies (decentralized, centralized and partly centralized). The result showed that the stormwater reduction from rainwater harvesting system mainly depends on the downspout connectivity. A selection framework was also proposed to select the system with lower environmental impact based on downspout connectivity, soil type and the centralized, partly centralized, or decentralized strategy. The results of this study are expected to help designers and policy makers choose environmentally attractive rainwater harvesting scenario by looking into different factors such as building characteristics (roof area, occupancy), method of analysis and scale of implementation. iv Acknowledgements Learning theories and concepts of a computational research to address the issues on water sustainability has been one of the most challenging academic tasks I have ever faced. This research project would not have been possible without the support of Dr. Defne Apul. This is a great opportunity to express my respect to Dr. Defne Apul for her guidance, advice and support for the entire three and a half years. I would like to extend my gratitude to National Science Foundation for the financial support. I owe my deepest gratitude to the committee members Dr. Steven Burian, Dr Ashok Kumar, Dr Cyndee Gruden and Dr. Youngwoo Seo for their assistance; without their knowledge on the specific topic; this research would not have been successful. My special thanks go to all my friends and group members, especially Robert, Chirjiv, Thelma, Hassan and Prayag for their valuable help and suggestions throughout my PhD. Last but not least, I would like to thank the Civil and Environmental Engineering Department, at The University of Toledo for providing me financial support and quality education for those wonderful years, and Rose Marie Ackerman for always being there to provide resources whenever needed. This dissertation is dedicated to my family and due to their inspiration and support, I am here. v Table of Contents Abstract ............................................................................................................................. iii Acknowledgements ............................................................................................................. v Table of Contents ............................................................................................................... vi List of Tables ..................................................................................................................... xi List of Figures .................................................................................................................. xiv List of Abbreviations ....................................................................................................... xix List of Symbols ................................................................................................................. xx 1 Introduction ............................................................................................................. 1 2 Introducing Demand to Supply Ratio as a New Metric for Understanding Life Cycle Greenhouse Gas (GHG) Emissions from Rainwater Harvesting Systems . 13 2.1 Introduction ............................................................................................... 15 2.2 Methodology ............................................................................................. 17 2.2.1 Goal and Scope ............................................................................. 17 2.2.2 Life cycle inventory, impact assessment, and interpretation ........ 24 2.3 Results and Discussion ............................................................................. 26 vi 2.3.1 Characteristics of the medium office buildings that have RWH systems ...................................................................................................... 26 2.3.2 Effect of demand to supply ratio (D/S) on life cycle greenhouse gas emissions from buildings with RWH systems .................................... 29 2.3.3 Comparison of buildings with and without RWH systems (RWH vs BAU scenarios) .................................................................................... 33 2.3.4 Per person and per area metrics .................................................... 36 2.3.5 On which type of building should one implement RWH? ............ 38 2.4 Conclusions ............................................................................................... 42 2.5 References ................................................................................................. 45 2.6 Supporting Information: Introducing Demand to Supply Ratio as a New Metric for Understanding Life Cycle Greenhouse Gas (GHG) Emissions from Rainwater Harvesting Systems. ....................................................... 50 3 Environmental impacts from harvesting rainwater: A comparison of supply versus demand based analysis for different climatic regions ........................................... 76 2.1 Introduction ............................................................................................... 79 2.2 Methodology ............................................................................................. 82 2.2.1 Life cycle modeling approach ....................................................... 82 2.2.2 Building characteristics ................................................................. 88 2.2.3 System sizing ................................................................................ 88 2.2.3.1 Demand and Supply ......................................................... 88 vii 2.2.3.2 Tank Sizing ...................................................................... 89 2.2.3.3 Dual Piping ....................................................................... 92 2.2.3.4 Energy use by pump ......................................................... 92 2.2.3.5 Other rainwater harvesting components ........................... 93 2.2.4 Regional precipitation variation .................................................... 94 2.2.5 Sewer Type ................................................................................... 95 2.3