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Nutrient Removal and Fouling Reduction in Electrokinetic Membrane Bioreactor at Various Temperatures

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Nutrient Removal and Fouling Reduction in Electrokinetic Membrane Bioreactor at Various Temperatures Nutrient Removal and Fouling Reduction in Electrokinetic Membrane Bioreactor at Various Temperatures By Chunliang Wei A Thesis Submitted to the Faculty of Graduate Studies in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Department of Civil Engineering University of Manitoba Winnipeg, CANADA Copyright © 2016 by Chunliang Wei ABSTRACT With the aim of mitigating membrane fouling, an electrocoagulation (EC) based electrokinetic membrane bioreactor (EMBR) was developed and operated with real municipal wastewater under low temperatures. Both batch tests and continuous EMBR experiments demonstrated the significant advantages in membrane fouling reduction over the conventional antifouling strategies, ushering its potential applications as an attractive hybrid MBR technology for decentralized wastewater treatment in remote cold regions. The main research observations and findings could be summarized as follows: (1). Effective membrane fouling mitigation at low temperatures was due to destruction of extracellular polymeric substances (EPS) and subsequent reduction of the biocake resistance. The transmembrane pressure (TMP) increased at a much slower rate in EMBR and the filtration resistance was about one third of the control MBR prior to chemical cleaning cycle; (2). A new membrane parameter, the specific fouling rate (SFR) was proposed, relating the fouling rate with permeate flux and temperature-dependent viscosity. Pore clogging and biocake resistances were quantified for the first time with the same membrane module and operating conditions as in regular MBR, rather than resorting to the use of batch filtration setups; (3). The floc size in EMBR did not increase as a result of the air scouring shear force and decrease in the extracellular polymeric substances (EPS); (4). When current intensity was less than 0.2 A, polarity reversal had minimal impact on electrode passivation reduction due to insignificant hydrogen yield, however, if current intensity was above 0.2 A, frequent polarity reversal (< 5 min per cycle) was detrimental to electrode passivation if no sufficient mixing was provided; (5). Viability of the microorganisms in the EMBR system was found to be dependent on duration of the current application and current density. The bacterial viability was not 1 significantly affected when the applied current density was less than 6.2 A/m2; (6). Significant abiotic ammonification was found in electrocoagulation (EC). DO in the treated liquid was depleted within an hour, under the anaerobic condition in EC, nitrate was chemometrically reduced to ammonium following a two-step first order reaction kinetics. Aeration (DO > 2 mg/L) was shown effective in suppressing abiotic ammonification; (7). Magnetic resonance imaging (MRI) technology was used for the first time as an in-situ non-invasive imaging tool to observe membrane fouling status in an EMBR. 2 To My Mother, My late Father and My Late Brother 3 ACKNOWLEDGEMENTS First of all I would like to express my greatest gratitude to my doctoral advisor Professor Jan Oleszkiewicz and co-advisor Professor Maria Elektorowicz for offering me the opportunity to conduct this research, for their far-reaching scientific insights, tireless guidance and persistent encouragement during this long journey. They are not only my academic supervisor, but also my life mentors. I am profoundly benefitted by their enduring research enthusiasms and respectful scientific spirits. I am deeply grateful to Professor Nazim Cicek for his valuable instructions, suggestions and discussions during this thesis work. I would also like to thank all of the examination committee members for their time to review and comment on my thesis. I wish to express my sincere gratitude and appreciation to the former and present heads of the Civil Engineering Department Professor Peter Rasmussen and Professor Ahmed Shalaby for allowing me to do the research work while working full time. Thanks also go to the staff in the Civil Engineering Dept. and graduate students in the Environmental Engineering Laboratory for their help. I would like to acknowledge the financial support of the Natural Sciences and Engineering Research Council of Canada (NSERC: STPGP/350666). 4 Finally I want to thank my mother, my late father and my late brother who have always been on my side during my difficult times in life. I particularly appreciate my daughter Mian Wei because she has never complained I didn’t spend enough time with her in her childhood. 5 THE UNIVERSITY OF MANITOBA FACULTY OF GRADUATE STUDIES ***** COPYRIGHT PERMISSION Nutrient Removal and Fouling Reduction in Electrokinetic Membrane Bioreactor at Various Temperatures By Chunliang Wei A Thesis/Practicum submitted to the Faculty of Graduate Studies of The University of Manitoba in partial fulfillment of the requirement of the degree of Doctor of Philosophy (c) 2016 Permission has been granted to the Library of the University of Manitoba to lend or sell copies of this thesis/practicum, to the National Library of Canada to microfilm this thesis and to lend or sell copies of the film, and to University Microfilms Inc. to publish an abstract of this thesis/practicum. This reproduction or copy of this thesis has been made available by authority of the copyright owner solely for the purpose of private study and research, and may only be reproduced and copied as permitted by copyright laws or with express written authorization from the copyright owner. 6 TABLE OF CONTENTS ABSTRACT .................................................................................................................................... 1 ACKNOWLEDGEMENTS ............................................................................................................ 4 TABLE OF CONTENTS ................................................................................................................ 7 LIST OF TABLES ........................................................................................................................ 14 LIST OF FIGURES ...................................................................................................................... 15 LIST OF APPENDICES ............................................................................................................... 20 ABBREVIATIONS AND NOMENCLATURE........................................................................... 20 CHAPTER 1: INTRODUCTION AND OBJECTIVES ............................................................... 26 1.1 Background and Research Needs ................................................................................... 26 1.1.1 Applications and challenges of the membrane bioreactor in wastewater treatment 26 1.1.2 Electrokinetic technologies in MBR wastewater treatment .................................... 29 1.1.3 Fundamental issues to be addressed in the electrokinetic technologies ................. 32 1.2 Objectives of the thesis .................................................................................................. 34 1.3 Thesis organization ............................................................................................................. 35 CHAPTER 2: LITERATURE REVIEW ...................................................................................... 38 2.1 Membrane bioreactor (MBR) .............................................................................................. 38 2.1.1 Membrane separation technology ................................................................................. 38 2.1.1.1 Membrane Materials .............................................................................................. 39 7 2.1.1.2 Membrane Configuration ....................................................................................... 39 2.1.1.3 Dead end filtration and crossflow filtration ........................................................... 41 2.1.1.4 Membrane Classification ....................................................................................... 41 2.1.2 MBR in wastewater treatment ...................................................................................... 42 2.1.2.1 Brief introduction ................................................................................................... 42 2.1.2.2 Constant pressure and constant flux operating modes ........................................... 43 2.1.2.3 Two basic MBR application modes ....................................................................... 44 2.1.2.4 Characteristic MBR operating parameters ............................................................. 45 2.1.3 Membrane fouling and control ..................................................................................... 47 2.1.3.1 Particle transport behavior and anatomy of membrane fouling ............................. 48 2.1.3.2 Membrane fouling factors ...................................................................................... 49 2.1.3.2.1 Fouling stages .................................................................................................. 51 2.1.3.2.2 Influence of membrane characteristics on fouling .......................................... 52 2.1.3.2.3 Influence of feed-biomass characteristics on fouling ...................................... 52 2.1.3.2.4 Influence of operating conditions on fouling .................................................. 58 2.1.3.3 Microscopic observation of membrane fouling through NMR or MRI technologies ...........................................................................................................................................
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