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Perchlorate Bioremediation: Controlling Media Loss in Ex-Situ

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UNLV Theses, Dissertations, Professional Papers, and Capstones 5-1-2016 Perchlorate Bioremediation: Controlling Media Loss in Ex-Situ Fluidized Bed Reactors and In-Situ Biological Reduction by Slow-Release Electron Donor Sichu Shrestha University of Nevada, Las Vegas, [email protected] Follow this and additional works at: https://digitalscholarship.unlv.edu/thesesdissertations Part of the Civil Engineering Commons, and the Environmental Engineering Commons Repository Citation Shrestha, Sichu, "Perchlorate Bioremediation: Controlling Media Loss in Ex-Situ Fluidized Bed Reactors and In-Situ Biological Reduction by Slow-Release Electron Donor" (2016). UNLV Theses, Dissertations, Professional Papers, and Capstones. 2744. https://digitalscholarship.unlv.edu/thesesdissertations/2744 This Dissertation is brought to you for free and open access by Digital Scholarship@UNLV. It has been accepted for inclusion in UNLV Theses, Dissertations, Professional Papers, and Capstones by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. PERCHLORATE BIOREMEDIATION: CONTROLLING MEDIA LOSS IN EX-SITU FLUIDIZED BED REACTORS AND IN-SITU BIOLOGICAL REDUCTION BY SLOW- RELEASE ELECTRON DONOR By Sichu Shrestha Bachelor of Engineering in Civil Engineering, Institute of Engineering, Tribhuvan University, Nepal 2004 Master of Science in Civil and Environmental Engineering Carnegie Mellon University 2011 A dissertation submitted in partial fulfillment of the requirements for the Doctor of Philosophy- Civil and Environmental Engineering Department of Civil and Environmental Engineering and Construction Howard R. Hughes College of Engineering The Graduate College University of Nevada, Las Vegas May 2016 Copyright 2016 by Sichu Shrestha All Rights Reserved Thesis Approval The Graduate College The University of Nevada, Las Vegas April 21, 2016 This thesis prepared by Sichu Shrestha entitled Perchlorate Bioremediation: Controlling Media Loss in Ex-Situ Fluidized Bed Reactors and In-Situ Biological Reduction by Slow-Release Electron Donor is approved in partial fulfillment of the requirements for the degree of Doctor of Philosophy- Civil and Environmental Engineering Department of Civil and Environmental Engineering and Construction Jacimaria R. Batista, Ph.D. Kathryn Hausbeck Korgan, Ph.D. Examination Committee Chair Graduate College Interim Dean Daniel Gerrity, Ph.D. Examination Committee Member Sajjad Ahmad, Ph.D. Examination Committee Member David James, Ph.D. Examination Committee Member Eduardo A. Robleto, Ph.D. Graduate College Faculty Representative ii ABSTRACT The main concern of perchlorate exposure through drinking water is its effects on the production of thyroid hormone, which is important for human metabolism and child’s brain development. The US Environmental Protection Agency (EPA) has listed perchlorate in the contaminant list as well as in the Unregulated Contaminant Monitoring rule. The extent of perchlorate contamination can be categorized by the level of contamination into parts per million (ppm) levels, typically in locations where perchlorate was manufactured, and parts per billion (ppb) levels where perchlorate was used for various purposes. Ion-exchange is generally adopted for treating ppb levels of perchlorate while biological reduction, bioremediation, is preferred for treating ppm level contamination. This dissertation focuses on two important but not completely researched issues related to ex- situ and in-situ perchlorate biodegradation: (a) Use of digital image as a tool to determine appropriate backwashing frequency for fluidized bed reactor (FBR) used to treat perchlorate contaminated waters, (b) Feasibility of using a slow release electron donor, emulsified oil, to support in-situ degradation of perchlorate in groundwater with slow and fast hydraulic conductivities. To address the first issue, two FBRs were built using five feet long and half inch diameter transparent plexiglass columns. Activated carbon was used as media and synthetic solutions containing 100 ppb, 100 ppm, and 10 ppm perchlorate were used. A high resolution camera was mounted targeting the operating zone of the FBR and pictures were taken at interval of 1.5 hours. The digital pictures were analyzed using the image processing tool, ImageJ. A biofilm model was developed and its simulated results were used to determine theoretical frequencies to backwash the filters so to avoid media loss. To address the second issue, four 5-foot long and iii 2.5-inch diameter column bioreactors were used to simulate saturated groundwater zones with fast and slow groundwater velocities. Soil and plastic rings were used as media to simulate slow and fast velocities, respectively. The results revealed that the biofilm model predicted backwashing times that were very close to those observed using digital imaging. For the first FBR run, backwashing time forecasted using biomass growth, in perchlorate fed batch bioreactors, was in agreement with the other two methods used. However, the biomass growth data was unable to simulate similar backwashing for the second and third runs in the FBRs. The result of FBR operation indicates that images processed with the ImageJ closely represented the height of the expanded media in the FBR, and hence it can be used to decide backwashing frequency. A good agreement was found between the backwashing needs encountered in the FBR runs and those forecasted using the biofilm model. For the testing of slow release electron donor, emulsified oil was proven to be an effective slow release electron donor to degrade nitrate and perchlorate in saturated groundwater zones. The removal of perchlorate required acclimation time while nitrate degraded almost immediately. Perchlorate degradation was highly impacted by high hydraulic conductivities (i.e. smaller contact time). Perchlorate degradation commenced after nitrate levels decreased to less than 0.5 mg/L. On the other hand, once a significant amount of biomass has been built into the system, degradation of both perchlorate and nitrate took place. It was found that the extent of degradation is dependent upon the relative amounts of perchlorate and nitrate present, the amount of electron donor present, and the residence time. iv ACKNOWLEDGEMENTS I would like to first and foremost thank my supervisor, Dr. Jacimaria Batista, for her inspiration and encouragement throughout this study. My work would not have been what it is now without her guidance and support. She has provided immense support and motivation during the entire course of my graduate study. I would like to extend my sincere gratitude and appreciation to my committee members, Dr. Sajjad Ahmad, Dr. Daniel Gerrity, Dr. David James, and Dr. Eduardo Robleto for their constructive and invaluable suggestions to finalize my work. I am very grateful to Mr. Peter Fraught for his assistance in the laboratory and for helping me with the experimental set-up. I would like to mention Ms. Julie Bertoia and Winnie David for their support and help. I am thankful to Mr. R. Marsh Starks for his assistance in setting up the camera. I would like to appreciate the support and opportunities that I received as a graduate student at UNLV, from the entire Civil and Environmental Engineering and Construction family, and also to the Fulbright S&T for the opportunity and supporting my study. My gratitude is to the Southern Nevada Water District for giving me the opportunity to work as intern, and learn about the emerging contaminants and other challenges that a drinking water sector is facing. I want to thank all my colleagues of Environmental Laboratory for their direct or indirect contributions and encouragement. Special thanks go to Erica, Mayra, Kazim, Mennah, Charles, Olivier, Yesika, Miguel, Bany and Caroline. It was pleasure working with you all. Thanks to the Nepalese community in Las Vegas for making me feel at home and giving me a memorable time at UNLV. Last but not the least; I would like to thank all my family members for their love and blessings. No words can express my gratitude to my parents, in-law parents, Mr. Gyanendra v Khadka and Ms. Naradevi Shrestha Khadka, sister Dr. Sinora Shrestha Joshi, brother in-law, Dr. Biswas Joshi, and in-law brother, Milan Khadka, for their support and constant inspiration to work harder. Special thanks to my husband, Mr. Mukesh Khadka, for being patient and supportive throughout this journey. It would not have been possible without his help and moral support. To my daughter, Aadya Khadka, thank you for being such an understanding and wonderful little girl. My words cannot convey suffice her efforts to cheer me up, give me hope and unconditional love, and her patience to give me the time I needed to complete my work. To my nephew, Aryav Joshi, your smile is the world best stress-busters for me. Lastly, I would like to dedicate this work to my parents who gave their all to make me who I am today. vi TABLE OF CONTENTS ABSTRACT........................................................................................................................ iii ACKNOWLEDGEMENTS................................................................................................. v TABLE OF CONTENTS.................................................................................................... vii LIST OF TABLES............................................................................................................... xi LIST OF FIGURES............................................................................................................
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