vii
Table of Contents
Sommario i
Abstract iv
Table of contents vii
List of figures xi List of tables xv Abbreviations xvii
1. Introduction
1.1 Research motivation 1 1.2 Objectives 21.3 Structure of the thesis 3
2. Overview of membrane filtration
2.1 Introduction 4
2.2 Types of membranes 7
2.2.1 Hollow fibre modules 9
2.2.2 Tubular devices 10
2.2.3 Flat plate modules 11
2.2.4 Spiral wound modules 12
2.3 Membrane properties 14 2.3.1 Membrane materials 14 2.3.1.1 Organic membranes 14 2.3.1.2 Inorganic membranes 19 2.3.2 Hydrophobicity 21 2.3.3 Charge 23 2.3.4 Roughness 24 2.3.5 Pore size 24
2.3.6 Porosity and pore size distribution 25
viii 2.4 Membrane technology market: from the world
marketing to the Italian one
27
3. Membrane technology
3.1 Introduction 34 3.2 Membrane processes 36 3.2.1 Reverse osmosis 373.2.2 Electrodyalysis and electrodyalysis reversal 39
3.2.3 Nanofiltration 40
3.2.4 Micro- and ultrafiltration 41
3.3 Membrane operation parameters 44
3.4 Advantages and disadvantages of membrane filtration 50
4. Microfiltration and Ultrafiltration membranes
4.1 Introduction 52
4.2 Feed categorization 54
4.3 MF/UF membrane materials 55
4.4 MF/UF module formats 57
4.5 MF/UF filtration processes 61
4.6 MF/UF membrane properties 65
4.7 MF/UF membrane applications and costs 68
5. Fouling
5.1 Introduction 71 5.2 Fouling mechanisms 72 5.3 Physical description 80 5.4 Types of fouling 82 5.4.1 Crystallization fouling 82 5.4.2 Particulate fouling 835.4.3 Surface reaction (corrosion) fouling 84
5.4.4 Biological fouling 86
ix
5.4.6 Composite fouling 91
5.5 Internal and external fouling 91
5.6 Reversible and irreversible fouling 92
5.7 Feed properties 93
5.7.1 Concentration 93
5.7.2 pH and Ionic strenght 94
5.7.3 Component interactions 95
5.7.4 Prefiltration and the removal of aggregates 96
6. Fouling Indices
6.1 Introduction 98 6.2 Fouling measuring 99 6.2.1 Turbidity 996.2.2 Silt density index SDI 101
6.2.3 Plugging factor PF 105
6.2.4 Mini plugging factor index MPFI 107 6.2.5 Membrane fouling index MFI and MFIUF 108
6.2.6 CrossFlow membrane fouling index CFS-MFI and CFS-MFIUF
113 6.2.7 Unified membrane fouling index UMFI 117
6.2.8 Vito fouling measurement VFM 120
6.2.9 Thermogravimetric method 124
6.2.10 Ultrasonic time-domain reflectometry TDR 129 6.2.11 Fluorescence excitation–Emission matrices–PIF 131
6.2.12 Normalized fouling rate NFR 134
6.3 Discussion of fouling indices 139
7. Membrane fouling control
7.1 Introduction 147
7.2 Strategy 148
7.3 Cleaning methods 149
7.3.1 Chemical cleaning 149
7.3.1.1 Chemical wash (CW) & Chemical enhanced backwash (CEB)
152
7.3.1.2 Clean in place (CIP) 153
x 7.3.2.1 Backwash 155 7.3.2.2 Air flush 156 7.3.2.3 Air scour 157 7.3.2.4 Crossflow 159 7.4 Foulant removal 160
7.4.1 Organics, algae and biofouling 162
7.4.2 Inorganics 163
7.4.3 Iron (Fe) and Manganese (Mn) 164
8. Conclusions
8.1 Conclusions and future research 165
Acknowledgements 168
