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Mitigation of Membrane Fouling in Microfiltration

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Mitigation of Membrane Fouling in Microfiltration MITIGATION OF MEMBRANE FOULING IN MICROFILTRATION & ULTRAFILTRATION OF ACTIVATED SLUDGE EFFLUENT FOR WATER REUSE A thesis submitted in fulfilment of the requirement for the degree of Doctor of Philosophy (PhD) Sy Thuy Nguyen Bachelor of Engineering (Chemical), RMIT University, Melbourne School of Civil, Environmental & Chemical Engineering Department of Chemical Engineering RMIT University, Melbourne, Australia December 2012 i DECLARATION I hereby declare that: the work presented in this thesis is my own work except where due acknowledgement has been made; the work has not been submitted previously, in whole or in part, to qualify for any other academic award; the content of the thesis is the result of work which has been carried out since the official commencement date of the approved research program Signed by Sy T. Nguyen ii ACKNOWLEDGEMENTS Firstly, I would like to thank Prof. Felicity Roddick, my senior supervisor, for giving me the opportunity to do a PhD in water science and technology and her scientific input in every stage of this work. I am also grateful to Dr John Harris and Dr Linhua Fan, my co-supervisors, for their ponderable advice and positive criticisms. The Australian Research Council (ARC) and RMIT University are acknowledged for providing the funding and research facilities to make this project and thesis possible. I also wish to thank the staff of the School of Civil, Environmental and Chemical Engineering, the Department of Applied Physics and the Department of Applied Chemistry, RMIT University, for the valuable academic, administrative and technical assistance. Lastly, my parents are thanked for the encouragement and support I most needed during the time this research was carried out. Sy Nguyen March 2012 iii LIST OF PUBLICATIONS Refereed journals S. T. Nguyen, F. A. Roddick and J.L. Harris (2010), Membrane foulants and fouling mechanisms in microfiltration and ultrafiltration of an activated sludge effluent, Water Science & Technology, 62(9), 1975-1983. S. T. Nguyen, F. A. Roddick (2010), Effects of ozonation and biological activated carbon filtration on membrane fouling in ultrafiltration of an activated sludge effluent, Journal of Membrane Science, 363(1-2), 271-277. S. T. Nguyen and F. A. Roddick (2011), Chemical cleaning of ultrafiltration membrane fouled by an activated sludge effluent, Desalination & Water Treatment, 34, 94-99. S. T. Nguyen, F. A. Roddick (2013), Pre-treatments for removing colour from secondary effluent: Effectiveness and influence on membrane fouling in subsequent microfiltration, Separation & Purification Technology, 103, 313-320. Refereed conference proceedings Membrane foulants and fouling mechanisms in microfiltration and ultrafiltration of an activated sludge effluent, in Proceedings & Abstracts of the 7th IWA World Congress on Water Reclamation and Reuse, 20-25 September 2009, Brisbane, Australia. S. T. Nguyen, F. A. Roddick and J.L. Harris (2010), Multi-cycle test for evaluating membrane fouling propensity in ultrafiltration of a secondary effluent, in Proceedings & Abstracts of the 5th IWA Young Water Professionals Conference, 5-7 July 2010, Sydney, Australia. S. T. Nguyen and F. A. Roddick, Chemical cleaning of ultrafiltration membrane fouled by an activated sludge effluent, in Proceedings of the 6th Conference of the Aseanian Membrane Society, 22-26 November 2010, Sydney, Australia. iv TABLE OF CONTENTS SUMMARY ................................................................................................................................................................ 1 CHAPTER 1 . INTRODUCTION ............................................................................................................................ 4 1.1. BACKGROUND OF THE PROJECT ......................................................................................................................... 4 1.2. RATIONALE ....................................................................................................................................................... 4 1.3. RESEARCH OBJECTIVES ..................................................................................................................................... 5 CHAPTER 2 . LITERATURE REVIEW ................................................................................................................ 8 2.1. OVERVIEW OF CONVENTIONAL MUNICIPAL WASTEWATER TREATMENT PROCESSES .......................................... 8 2.1.1. Preliminary treatment .............................................................................................................................. 8 2.1.2. Primary treatment .................................................................................................................................... 8 2.1.3. Secondary treatment ................................................................................................................................. 8 2.1.4. Tertiary treatment .................................................................................................................................... 9 2.2. MEMBRANE FILTRATION IN WATER AND WASTEWATER TREATMENT ................................................................ 9 2.2.1. Membrane classification ........................................................................................................................ 10 2.2.2. Membrane materials and structures ....................................................................................................... 11 2.2.3. Membrane configurations ...................................................................................................................... 12 2.2.4. Operation modes of membrane processes .............................................................................................. 14 2.2.5. Feedwater for membrane processes for water reuse .............................................................................. 14 2.3. MEMBRANE FOULING AND FACTORS AFFECTING FOULING .............................................................................. 16 2.3.1. Effect of feedwater content ..................................................................................................................... 17 2.3.2. Effect of solution chemistry .................................................................................................................... 21 2.3.3. Effect of membrane characteristics ........................................................................................................ 22 2.3.4. Effect of membrane configuration .......................................................................................................... 23 2.3.5. Effect of operating conditions ................................................................................................................ 24 2.4. RESISTANCES IN MEMBRANE FILTRATION AND FOULING MODELS ................................................................... 24 2.4.1. Fouling models for dead-end filtration .................................................................................................. 25 2.4.2. Fouling models for cross-flow filtration ................................................................................................. 28 2.4.3. Concentration polarisation .................................................................................................................... 29 2.4.4. Resistance-in-series model ..................................................................................................................... 30 2.5. FOULING MITIGATION ..................................................................................................................................... 31 2.5.1. Pre-treatment of the feedwater ............................................................................................................... 31 2.5.2. Selection of membrane types and surface modification ......................................................................... 40 2.5.3. Optimising module configuration and process conditions ..................................................................... 40 2.5.4. Membrane cleaning ................................................................................................................................ 41 2.6. EVALUATING THE FOULING POTENTIAL OF FEEDWATER .................................................................................. 46 2.6.1. Modified fouling index (MFI) ................................................................................................................. 46 2.6.2. Unified membrane fouling index (UMFI) ............................................................................................... 47 v 2.7. CHARACTERISATION OF FILTRATION MEMBRANES .......................................................................................... 48 2.7.1. Contact angle measurement ................................................................................................................... 49 2.7.2. Streaming potential ................................................................................................................................ 49 2.7.3. Atomic force microscopy (AFM) ............................................................................................................ 49 2.8. TECHNIQUES FOR FOULING CHARACTERISATION ............................................................................................. 50 2.8.1. Characterisation of organic matter .......................................................................................................
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