SIMULTANEOUS CARBON AND NITROGEN REMOVAL ACCOMPANIED BY ENERGY RECOVERY FROM WASTEWATER IN A COUPLED MICROBIAL FUEL CELLS SYSTEM BY NGUYEN HOANG DUNG A DISSERTATION SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY (ENGINEERING AND TECHNOLOGY) SIRINDHORN INTERNATIONAL INSTITUTE OF TECHNOLOGY THAMMASAT UNIVERSITY ACADEMIC YEAR 2022 Ref. code: 25656222300219VQS THAMMASAT UNIVERSITY SIRINDHORN INTERNATIONAL INSTITUTE OF TECHNOLOGY DISSERTATION BY NGUYEN HOANG DUNG ENTITLED SIMULTANEOUS CARBON AND NITROGEN REMOVAL ACCOMPANIED BY ENERGY RECOVERY FROM WASTEWATER IN A COUPLED MICROBIAL FUEL CELLS SYSTEM was approved as partial fulfillment of the requirements for the degree of Doctor of Philosophy (Engineering and Technology) on June 26, 2023 Chairperson (Professor Nipon Pisutpaisal, Ph.) Member and Advisor (Professor Sandhya Babel, D.) Member (Associate Professor Rachnarin Nitisoravut, Ph.) Member (Associate Professor Paiboon Sreearunothai, Ph.) Member (Associate Professor Jenyuk Lohwacharin, Ph.) Member (Warunsak Liamlaem, Ph.) Director (Professor Pruettha Nanakorn, D. code: 25656222300219VQS (1) Dissertation Title SIMULTANEOUS CARBON AND NITROGEN REMOVAL ACCOMPANIED BY ENERGY RECOVERY FROM WASTEWATER IN A COUPLED MICROBIAL FUEL CELLS SYSTEM Author Nguyen Hoang Dung Degree Doctor of Philosophy (Engineering and Technology) Faculty/University Sirindhorn International Institute of Technology/ Thammasat University Dissertation Advisor Professor Sandhya Babel, D. Academic Years 2022 ABSTRACT For over a decade, microbial fuel cell (MFC) has received much attention as a pioneering technology for wastewater treatment, owing to its ability to generate electricity from organic matter.
However, most wastewater has the presence of nitrogen and the requirement to remove nitrogen as a contaminant has caused limitations in energy recovery from organic carbon. Despite the advantages of integrating biological nitrogen removal (BNR) into MFC and the promising results in organic carbon removal, achieving high nitrogen removal efficiency while optimizing energy recovery from organic matter remains a challenge. It is difficult to select an external resistance (ER) value that satisfies both goals. The chambers of a stacked MFC system can be sequencing-batch operated to achieve specific goals.
System can configured accordingly with suitable conditions for each chamber to achieve the goal of energy recovery from organic carbon and nitrogen removal. In this study, BNR was integrated into a coupled MFC with four chambers sequencing-batch operated reactor. With ER close to its internal resistance, the first MFC (N-MFC) was responsible for power generation from organic carbon and ammonium oxidation in the input wastewater. The ER of the second MFC (D-MFC) Ref.
code: 25656222300219VQS (2) was set at a small value (10 Ω) to have a high current density, facilitating nitrogen removal in presence of minimum carbon as required for the denitrification. The study evaluated the removal efficiency of carbon and nitrogen accompanied by power generation by applying three different sequencing-batch operation modes to four chambers of a coupled MFC. In the first mode, wastewater transferred from the N-MFC anode chamber to the cathode chamber, then to the D-MFC anode chamber, and lastly to the D-MFC cathode chamber. In the second and the third modes, the wastewater was fed into anode chamber of the N-MFC.
The D-MFC received the N-MFC output (in order from anode chamber to anode chamber, from cathode chamber to cathode chamber). The output of the cathode chamber of the D-MFC was the effluent of the coupled MFC system, while the output of the anode chamber of the D-MFC came back to the cathode chamber of the N-MFC. The distinction between the second and third modes is the different dissolved oxygen (DO) in the cathode chamber of N-MFC to control the nitrification process. The study provided a solution for optimizing electrical energy recovered from organic matter in parallel with efficient nitrogen treatment and better understanding of integrating BNR process into MFC technology.
Depending on each operation mode, the following specific objectives are proposed: (i) to investigate the effect of DO, and initial ammonium concentration for ammonium oxidizing and power generation from N-MFC; (ii) to assess the ability of ammonium diffusion through cation exchange membrane (CEM) in N-MFC; (iii) to investigate the effect of the COD/N ratio for nitrogen removal in D-MFC; (iv) to evaluate the coulombic efficiency of the system; (v) to evaluate the ratio of autotrophic denitrification in cathodic chamber of D-MFC. The following is a summary of the results and findings of this study. (i) In the N-MFC, the second operational mode produced more power than the first operational mode by addressing the flaws that impeded electricity production in the first operational mode. Overall, power generation decreases as DO at the cathode decreases, while variations in nitrogen input showed no great influence on power generation of the N-MFC.
Ammonium was completely oxidized to nitrate as the major product with very small amounts of nitrite detected under high DO at the cathode chamber. In the third operational mode with low DO at the cathode chamber of the N- MFC, nitrite was the main product of the ammonium oxidation process. code: 25656222300219VQS (3) (ii) The input COD of the anode chamber and the DO concentration in the cathode chamber affect the electricity generation of the N-MFC, directly influencing the diffusion of cations (such as ammonium) from the anode chamber to the cathode chamber in order to balance the charge. In addition, the ER of N-MFC in the second operational mode (50 Ω) is lower than that in the third operational mode (100 Ω), resulted in more favorable current production and more ammonium diffusion for charge balance.
(iii) The nitrogen removal efficiency at the D-MFC increased when the COD/N ratio of wastewater entering the D-MFC increased. The first operational mode, which used both the anode and cathode chambers for denitrification, enhanced nitrogen removal efficiency. In the second and third operational modes, the denitrification process only occurred in the cathode chamber of D-MFC. The nitrogen removal efficiency at the cathode chamber of the D-MFC was higher in the third operational mode than in the second operational mode for the same COD/N ratio input to the D- MFC, which is the result of a higher reduction rate of nitrite than nitrate.
(iv) In the first operational mode, an increase in the COD input of the anode chamber resulted in a decrease in the anodic coulombic efficiency. The anodic coulombic efficiencies of N-MFC in the second operational mode was higher than that in the first operational mode. The anodic coulombic efficiencies of N-MFC in the third operational mode were relatively low because of low DO in the cathode chamber. (v) In all operational mode, the high ratio of autotrophic denitrification in the cathode chamber of the D-MFC demonstrated that autotrophic denitrification was the primary process assisting in nitrogen removal.
In conclusion, this study showed that a properly configured and operated coupled MFC can effectively remove carbon and nitrogen with energy recovery from wastewater. By taking advantage of ammonium diffusion across the CEM to improve the operating method, the second operational mode outperformed the first operational mode with respect to power generation and coulombic efficiency. The suitable setup of the system allowed the N-MFC to oxidize over 75% of organic matter input and isolate nitrogen input simultaneously, giving favorable environmental conditions for generating the energy from wastewater primarily in the N-MFC. The nitrogen isolation efficiency of the N-MFC depends on input organic matter of the anode chamber, the Ref.
code: 25656222300219VQS (4) DO concentration in the cathode chamber, and the ER. In the second and the third operational mode, the main mechanism for nitrogen removal at the D-MFC was autotrophic denitrification. When comparing the second and the third operational modes, the power generation was higher in the second mode, which followed a conventional nitrification/denitrification system. However, the third mode with shortcut nitrification-denitrification was more energy-efficient and better in nitrogen removal.
Keywords: Biodegradation, Anaerobic process, Nitrogen removal, Microbial fuel cell, Energy recovery Ref. code: 25656222300219VQS (5) ACKNOWLEDGEMENTS I would like to express my sincere gratitude to my advisor Prof. Sandhya Babel, for her patient guidance, continuous support, and valuable encouragement throughout my Ph. Her expertise, kindness, and dedication have been uncountable to me.
I am also deeply grateful to my thesis committee members, Prof. Nipon Pisutpaisal, Assoc. Paiboon Sreearunothai, Assoc. Rachnarin Nitisoravut, Dr.
Warunsak Liamlaem and Assoc. Jenyuk Lohwacharin, for their insightful feedback and constructive criticism. Their comments have been instrumental in shaping my research. I thank my colleagues and friends, Dr.
Tuan Anh Ta, Dr. Yahampath Arachchige Don, and Mr. Tan Thong Nguyen, for contributing to the experimental model construction, proofreading, and helpful brainstorming. I am indebted to the staff and faculty of Sirindhorn International Institute of Technology (SIIT), Thammasat University, for providing a stimulating research environment and many personal growth opportunities.
This work would not have been possible without the full financial support of SIIT through an EFS scholarship in the School of Bio-Chemical Engineering and Technology. Finally, I would like to give my heartfelt appreciation to my family, especially to my father Van Nghia Nguyen, my mother Hong Phuong Ha, my brother Trung Hieu Nguyen, my sister Ngoc Lan Nguyen, my brother Hoang Long Nguyen, for their unwavering love throughout my abroad study. Their sacrifices and understanding have been my constant source of strength. Thank you all for your inspiration.
Nguyen Hoang Dung Ref. code: 25656222300219VQS (6) TABLE OF CONTENTS Page ABSTRACT (1) ACKNOWLEDGEMENTS (5) LIST OF TABLES (9) LIST OF FIGURES (10) LIST OF SYMBOLS/ABBREVIATIONS (12) CHAPTER 1 INTRODUCTION 1.3 Scope of research 7 CHAPTER 2 LITERATURE REVIEW 8 2.1 Principle of MFCs technology 8 2.2 Design of MFCs 11 2.4 Inoculum and substrate 14 2.3 Recent MFCs studies for nitrogen and carbon removal, power generation 15 2.1 Nitrification and cathodic denitrification in MFCs 16 2.2 Shortcut nitrification/denitrification process in MFCs 22 2.3 Heterotrophic anodic denitrification in MFCs 23 2.5 Influencing factors for carbon and nitrogen removal in an MFC 27 Ref.6 Challenges in using MFC for carbon and nitrogen removal 30 CHAPTER 3 RESEARCH METHODOLOGY 32 3.2 Inoculation and medium 33 3.3 Start-up MFCs 34 3.4 MFCs operation after start-up 35 3.1 First operational mode 37 3.2 Second operational mode 37 3.3 Third operation mode 38 3.5 Analysis and calculations 40 3.6 Characterization analysis of electrode surfaces 41 CHAPTER 4 RESULTS AND DISCUSSION 43 4.1 Start-up stage 43 4.2 First operational mode 46 4.1 Electricity generation and COD removal 46 4.3 Second operational mode 54 4.1 Electricity generation and COD removal 56 4.2 Nitrogen isolation and removal 60 4.4 Third operational mode 64 4.1 Power generation from COD removal 64 4.4 Denitrification at the D-MFC 76 4.5 The advantages and disadvantages of three different operational modes: A comparison 79 4.6 Characterization of electrode surfaces 81 CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS 84 5.2 Recommendations 86 REFERENCES 88 APPENDICES APPENDIX A 100 APPENDIX B 102 APPENDIX C 103 APPENDIX D 104 BIOGRAPHY 105 Ref. code: 25656222300219VQS (9) LIST OF TABLES Tables Page 2.1 Redox reactions with theoretical potentials standard conditions in MFC 8 2.2 The advantages and disadvantages of some electrode materials 13 2.3 The performance with pros and cons of various MFC configurations for simultaneous removal of carbon and nitrogen 19 2.4 Some microorganisms and their roles in MFC system 27 4.1 COD output of each chamber of MFC 49 4.2 Nitrogen parameter outputs of each chamber of MFC 51 4.3 A comparion of three different operational modes with same influent wastewater input 80 4.4 EDS analysis before and after operation 83 Ref. code: 25656222300219VQS (10) LIST OF FIGURES Figures Page 2.1 Diagram of MFCs technology principles in wastewater treatment 9 2.2 DET mechanisms to anode 11 2.3 Shortcut nitrification-denitrification process in MFCs 22 2.4 Mechanism of heterotrophic anodic denitrification process in MFCs 24 3.1 The main components of the coupled MFCs 32 3.2 The procedure for pretreatment of CEM 33 3.3 The procedure for pretreatment of electrode 33 3.4 Schematic diagram of start-up stage 35 3.5 Summary of operational stage 36 3.6 Schematic diagram of the first operational mode 37 3.7 The second mode operating schematic of the coupled MFC system 38 3.8 The third mode operating schematic of the coupled MFC system for shortcut nitrification-denitrification 40 4.