Volatile Fatty Acids Effects on Nitrite Removal and Nitrate Formation During Activated Sludge Treatment
Total Page:16
File Type:pdf, Size:1020Kb
University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 8-2004 Volatile Fatty Acids Effects on Nitrite Removal and Nitrate Formation during Activated Sludge Treatment Merve Oguz University of Tennessee - Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Civil and Environmental Engineering Commons Recommended Citation Oguz, Merve, "Volatile Fatty Acids Effects on Nitrite Removal and Nitrate Formation during Activated Sludge Treatment. " PhD diss., University of Tennessee, 2004. https://trace.tennessee.edu/utk_graddiss/2341 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Merve Oguz entitled "Volatile Fatty Acids Effects on Nitrite Removal and Nitrate Formation during Activated Sludge Treatment." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Civil Engineering. Kevin G. Robinson, Major Professor We have read this dissertation and recommend its acceptance: Alice C. Layton, Gary S. Sayler, Gregory Reed, Paul Frymier Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) To the Graduate Council: I am submitting herewith a dissertation written by Merve Oguz entitled “Volatile Fatty Acids Effects on Nitrite Removal and Nitrate Formation during Activated Sludge Treatment.” I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, with a major in Civil Engineering. Kevin G. Robinson Major Professor We have read this dissertation and recommend its acceptance: Alice C. Layton Gary S. Sayler Gregory Reed Paul Frymier Acceptance for the Council: Anne Mayhew Vice Chancellor and Dean of Graduate Studies (Original signatures on file with official student records.) VOLATILE FATTY ACID EFFECTS ON NITRITE REMOVAL AND NITRATE FORMATION DURING ACTIVATED SLUDGE TREATMENT A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Merve Oguz August 2004 DEDICATION This dissertation is dedicated to my beautiful daughter ZEYNEP and my baby son EDIZ ii ACKNOWLEDGMENTS I would like to state my deep gratitude to my major professor, Dr. Kevin Robinson, for his support and guidance throughout this project. I wish to express my sincere appreciation to Dr. Alice Layton for her generous guidance and encouragement. I am thankful to Dr. Gary Sayler for his help and financial support for this study. Special thanks are also extended to other committee members, Dr. Gregory Reed and Dr. Paul Frymier for their advice and comments during this research. I would also like to thank Shawn Hawkins for being my friend and helping in the laboratory when I needed. I am indebted to the members of Center for Environmental Biotechnology. Special thanks go to Dr. John Sanseverino, Dr. Fu-Min Menn, James Easter and Victoria Garrett for their help with laboratory techniques. I would also like to acknowledge Dr. Robert Compton, Dr. Steven Hagan and Jeff Steill from Chemistry Department for their help with nitrous oxide analysis. I am very thankful to Turkish Ministry of Education for giving me this opportunity and supporting me financially. My sincere thanks are extended to my parents, Leyla and Aytekin Temizer, for their immeasurable sacrifices, patience, love and support. I would like to thank my husband, Osman Oguz, for his moral support, companionship and love. My 6-year old daughter Zeynep deserves my special appreciation for her love and understanding during this study. iii ABSTRACT Reaction sequences of nitrifying and denitrifying bacteria are widely used to eliminate nitrogenous compounds from wastewater. During nitrification, ammonia is oxidized to nitrite by autotrophic ammonia oxidizing bacteria and nitrite is further oxidized to nitrate by nitrite oxidizers. Subsequently, nitrate or nitrite is reduced by denitrifying bacteria to gaseous nitrogen compounds. It is common knowledge that nitrification is an aerobic process and denitrification an anaerobic process. However, recent research has shown that denitrification can occur under aerobic conditions in pure cultures. Volatile fatty acids (VFAs), produced during anaerobic treatment processes, can affect both nitrite oxidation and aerobic denitrification. VFAs were shown to reduce nitrate formation via nitrite oxidation in activated sludge systems and to stimulate aerobic denitrification in pure cultures. Nitrite removal inhibition by VFAs observed in activated sludge systems may be due to the level of aerobic denitrification which occurs. Investigation of this possibility can provide a new insight for the removal of nitrogen from wastewater and possibly reduce the chemical and energy demand for nitrogen treatment. The overall goal of this research was to demonstrate that nitrification and denitrification could occur in the same reactor under aerobic conditions in the presence of VFAs. The impact of VFAs on nitrite removal and nitrate formation in activated sludge systems was studied in batch and CSTR experiments. The experimental work included measurements of nitrite removal, nitrate formation and CO2 fixation in the absence and presence of VFAs. In addition, molecular tools were applied to examine changes in microbial population density when the population was exposed to VFAs. Production of iv N2O and activity of periplasmic nitrate reductase enzyme (NAP) which catalyses the first step of aerobic denitrification were also analyzed. Nitrite removal and nitrate formation rates were reduced in the presence of VFAs in batch experiments. Nitrate formation rate was reduced to a greater extent (74%) than nitrite removal rate (35%) indicating that products other than nitrate were formed during nitrite oxidation. The addition of VFAs into an activated sludge CSTR treating municipal wastewater resulted in a rapid decrease in nitrate formation rate (> 70% reduction); however, nitrite removal rate was not reduced. No nitrogen was discharged in the effluent of the CSTR indicating that nitrogenous compounds were completely removed from the wastewater. In contrast, VFAs were not found to impact carbon dioxide fixation efficiency in either batch or CSTR experiments although it is generally believed to be limited by the availability of energy derived from nitrite oxidation. Non-inhibitory effect of VFAs on carbon dioxide fixation implied that VFAs disturb nitrite removal and nitrate formation by a different system other than nitrite oxidation. Additionally, the number of nitrite oxidizing bacteria (NOB) remained relatively constant in the presence of VFAs indicating that any reduction observed was not due to a decrease in NOB. N2O gas was produced in the presence of VFAs which was a clear indication that aerobic reduction of nitrite and/or nitrate occurred. It appeared that aerobic denitrification was responsible for the unbalanced nitrification conversions in the presence of VFAs. Also, the activity of NAP enzyme increased when VFAs were present suggesting a significant role of aerobic denitrification during nitrogen conversions. v Table of Contents CHAPTER 1 .......................................................................................................................1 INTRODUCTION .............................................................................................................. 1 1.1 Background............................................................................................................... 1 1.2 Hypothesis and Objectives .................................................................................... 5 CHAPTER 2 .......................................................................................................................8 LITERATURE REVIEW ................................................................................................... 8 2.1 The Activated Sludge Process ................................................................................. 8 2.2 Anaerobic Treatment and VFAs ............................................................................. 10 2.3 Nitrification............................................................................................................. 12 2.3.1 Physiology of Nitrifying Bacteria .................................................................... 13 2.3.2 Biochemistry of Nitrifying Bacteria................................................................. 17 2.3.3 Carbon Metabolism in Nitrifying Bacteria....................................................... 22 2.3.4 Activated Sludge Nitrification ......................................................................... 25 2.4 Denitrification........................................................................................................ 27 2.5 Conceptional Model for Nitrogen Removal Focusing on Nitrite as the Central Compound........................................................................................................................