Singh Membrane Technology and Engineering for Water Purification

Application, Systems Design and Operation
2. Auflage 2014
ISBN: 978-0-444-63409-2
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 452 Seiten

Membrane Technology and Engineering for Water Purification, Second Edition is written in a practical style with emphasis on: process description; key unit operations; systems design and costs; plant equipment description; equipment installation; safety and maintenance; process control; plant start-up; and operation and troubleshooting. It is supplemented by case studies and engineering rules-of-thumb. The author is a chemical engineer with extensive experience in the field, and his technical knowledge and practical know-how in the water purification industry are summarized succinctly in this new edition. This book will inform you which membranes to use in water purification and why, where and when to use them. It will help you to troubleshoot and improve performance and provides case studies to assist understanding through real-life examples. - Membrane Technology section updated to include forward osmosis, electrodialysis, and diffusion dialysis - Hybrid Membrane Systems expanded to cover zero liquid discharge, salt recovery and removal of trace contaminants - Includes a new section on plant design, energy, and economics

Rajindar Singh is President of Membrane Ventures, LLC. He is a Senior Member of the American Institute of Chemical Engineers, with more than 35 years of experience focusing on desalination, bioseparations, ion exchange, high purity water production, produced water treatment, membrane plants technical support, electrochemical fuel cells and polymers. Rajindar received post-graduate degrees in chemical engineering and bioengineering from the Univeristy of Massachusetts, Amherst, USA. He is the co-inventor of six patents, and has published 40 journal papers and three books.

Autoren/Hrsg.

Singh, Rajindar

Inhaltsverzeichnis

1;Front Cover;1
2;Membrane Technology and Engineering for Water Purification: Application, Systems Designand Operation;4
3;Copyright;5
4;Dedication;6
5;Contents;8
6;Preface Two;10
6.1;References;11
7;Acknowledgements for the Second Edition;12
8;Chapter 1: Introduction to Membrane Technology;16
8.1;1.1. Technology Overview;16
8.2;1.2. Historical Development;18
8.3;1.3. Membrane-Separation Characteristics;23
8.3.1;1.3.1. Membrane-separation basics;23
8.3.1.1;The membrane process;23
8.3.1.2;Membrane transport;25
8.3.1.3;Membrane selectivity;28
8.3.1.4;Concentration polarisation;28
8.3.2;1.3.2. Membrane materials and properties;33
8.3.2.1;Polymeric membranes;33
8.3.2.2;RO membranes;36
8.3.2.3;Inorganic membranes;40
8.3.2.4;Charged membranes;41
8.3.2.5;Molecular weight cut-off;41
8.3.2.6;Bubble point;42
8.4;1.4. Membrane Processes;43
8.4.1;1.4.1. Reverse osmosis;43
8.4.2;1.4.2. Nanofiltration;48
8.4.3;1.4.3. Ultrafiltration;50
8.4.4;1.4.4. Microfiltration;54
8.4.4.1;Submerged membrane filtration systems;56
8.4.4.2;Membrane bioreactors;57
8.4.4.3;Dead-end cartridge filters;57
8.4.5;1.4.5. Dialysis;58
8.4.5.1;Hemodialysis;59
8.4.5.2;Diffusion dialysis;59
8.4.6;1.4.6. Electrodialysis;60
8.4.7;1.4.7. Gas separation;63
8.4.7.1;Porous membranes;64
8.4.7.2;Non-porous membranes;64
8.4.8;1.4.8. Pervaporation;67
8.4.9;1.4.9. Membrane contactors;68
8.4.10;1.4.10. Other membrane technologies;69
8.4.10.1;Membrane distillation;69
8.4.10.2;Membrane reactors;70
8.4.10.3;Dynamically formed membranes;70
8.4.10.4;Electrofiltration;72
8.4.10.5;Polyelectrolyte-enhanced ultrafiltration;73
8.4.10.6;Micellar-enhanced ultrafiltration;73
8.4.10.7;Fractionation of macromolecules;74
8.4.10.8;Activated carbon-enhanced filtration;75
8.4.10.9;Pressure-retarded osmosis;75
8.4.10.10;Forward osmosis;76
8.5;1.5. Membrane Modules;78
8.5.1;1.5.1. Conventional modules;78
8.5.2;1.5.2. Newer modules;80
8.5.2.1;High-performance SW modules;80
8.5.2.2;Hollow fibre modules;81
8.5.2.3;Ceramic modules;81
8.5.2.4;Short flow-path modules;81
8.5.2.5;Advanced PAF membrane module;84
8.5.2.6;Flux-enhancing techniques;85
8.6;1.6. Membrane Fouling;85
8.6.1;1.6.1. The fouling phenomena;87
8.6.2;1.6.2. Fouling-resistant membranes;87
8.6.2.1;Surface chemistry;87
8.6.2.2;Polymer modification;88
8.6.2.3;Hydrophilic-hydrophobic blend membranes;88
8.6.2.4;Surface modification;88
8.6.2.5;Ceramic/polymeric hybrid membranes;91
8.6.2.6;Neo-dynamic membranes?;91
8.7;1.7. Concluding Remarks;92
8.8;References;93
9;Chapter 2: Water and Membrane Treatment;96
9.1;2.1. Priceless Water;96
9.2;2.2. Water Treatment;99
9.2.1;2.2.1. Coagulation;103
9.2.2;2.2.2. Softening;106
9.2.2.1;Lime softening;106
9.2.2.2;Ion-exchange softening;107
9.2.2.3;NF softening;108
9.2.3;2.2.3. Granular media filtration;109
9.2.4;2.2.4. Activated carbon filtration;110
9.2.5;2.2.5. Membrane filtration;111
9.2.5.1;Continuous cross-flow filtration;113
9.2.5.2;Semicontinuous dead-end filtration;114
9.2.5.3;Membrane bioreactors;114
9.2.6;2.2.6. Deaeration-decarbonation;115
9.2.7;2.2.7. Chemical oxidation;117
9.2.7.1;Manganese greensand oxidation-filtration;117
9.2.8;2.2.8. Disinfection;118
9.2.8.1;Chlorination;118
9.2.8.2;Ozonation;119
9.2.8.3;UV irradiation;119
9.2.9;2.2.9. Electrocoagulation;120
9.2.9.1;Operating parameters;122
9.2.9.2;Treated waters;122
9.2.10;2.2.10. Ion exchange;123
9.2.10.1;IX resins;123
9.2.10.2;Strongly acidic cation resins;123
9.2.10.3;Weak acid cation resins;124
9.2.10.4;Strongly basic anion resins;124
9.2.10.5;Weak base anion resins;124
9.2.10.6;Resins selection;124
9.2.10.7;Physical characteristics;125
9.2.10.8;Limitations;125
9.2.10.9;Demineralisation;125
9.2.10.10;Dual-bed demineralisation;126
9.2.10.11;Mixed-bed ion exchange;126
9.2.10.12;Normal operation;127
9.2.10.13;Regeneration;128
9.2.11;2.2.11. Non-DI water ion-exchange applications;130
9.2.11.1;Organics removal;130
9.2.11.2;Nitrates removal;130
9.2.11.3;Industrial wastewater treatment;130
9.2.11.4;Carbohydrate refining;130
9.2.11.5;Pharmaceutical processing;131
9.2.12;2.2.12. Membrane degasification;131
9.2.13;2.2.13. Electrodeionisation;131
9.2.14;2.2.14. Post-treatment of desalinated water;135
9.3;2.3. Membrane Fouling, Scaling, and Controls;136
9.3.1;2.3.1. Scaling and fouling mechanism;138
9.3.2;2.3.2. Membrane scaling;139
9.3.3;2.3.3. Membrane fouling;141
9.3.3.1;Organic fouling;145
9.3.3.2;Colloidal fouling;145
9.3.3.3;Silica fouling;145
9.3.3.4;Biofouling;146
9.3.4;2.3.4. In-line chemical treatment;149
9.3.4.1;In-line coagulation;149
9.3.4.2;In-line dechlorination;150
9.3.4.3;In-line pH adjustment;150
9.3.4.4;Anti-scalant threshold treatment;151
9.4;2.4. Membrane Systems Design;152
9.4.1;2.4.1. RO/NF system basics;153
9.4.2;2.4.2. Membrane system controls;159
9.4.2.1;Basic controls;159
9.4.2.2;Control systems;160
9.4.2.3;Process control valves;161
9.4.2.4;Product quality controls;162
9.4.2.5;Safety features;162
9.4.3;2.4.3. RO/NF array design;163
9.4.4;2.4.4. Cross-flow (constant pressure) UF/MF design;169
9.4.4.1;Single-pass system;170
9.4.4.2;Batch filtration;171
9.4.4.3;Feed-and-bleed configuration;171
9.4.4.4;Multiple array design;171
9.4.4.5;UF/MF performance;172
9.4.5;2.4.5. Constant flux (variable pressure) UF/MF design;176
9.4.6;2.4.6. ED design;177
9.4.7;2.4.7. Performance monitoring;178
9.5;2.5. Membrane Cleaning and Sanitisation;180
9.5.1;2.5.1. Membrane cleaning;180
9.5.1.1;Cleaning chemicals;181
9.5.1.2;In situ RO/NF element cleaning procedure;184
9.5.1.3;Membrane filters cleaning procedure;187
9.5.2;2.5.2. Membrane sanitisation;187
9.5.2.1;Chemical sanitisation;187
9.5.2.2;Hot water sanitisation (HWS);188
9.6;2.6. Concluding Remarks;190
9.7;References;191
10;Chapter 3: Hybrid Membrane Systems - Applications and Case Studies;194
10.1;3.1. Novel Applications;195
10.1.1;3.1.1. Industrial wastewater treatment;195
10.1.2;3.1.2. Produced water treatment;196
10.1.3;3.1.3. Zero liquid discharge;199
10.1.4;3.1.4. MVC-RO hybrid desalination;200
10.1.5;3.1.5. Hybrid NF-RO-MSF seawater desalination process;201
10.1.6;3.1.6. Salts recovery from seawater desalination plants;202
10.1.7;3.1.7. Landfill leachate water treatment;203
10.1.8;3.1.8. Arsenic and nitrate-contaminated groundwater;205
10.1.9;3.1.9. Treatment of acidic streams;206
10.1.10;3.1.10. Dairy processing;207
10.1.11;3.1.11. Sugar processing;209
10.1.12;3.1.12. Vegetable proteins;210
10.1.13;3.1.13. Edible leaf protein concentrates;210
10.1.14;3.1.14. Vegetable and corn oil processing;212
10.1.15;3.1.15. Fruit juice and wine processing;215
10.1.16;3.1.16. Recovery of flavour compounds by osmotic distillation;218
10.1.17;3.1.17. Bioprocessing;220
10.1.18;3.1.18. Membrane recycle bioreactors;222
10.1.19;3.1.19. Dehydration of ethanol;223
10.1.20;3.1.20. Flue gas desulphurisation by membrane gas absorption;224
10.1.21;3.1.21. Fuel cell integrated membrane desalination;225
10.1.22;3.1.22. Seawater desalination by ion-concentration polarisation;226
10.1.23;3.1.23. Low-energy electrochemical process for seawater desalination;227
10.1.24;3.1.24. Sea salt recovery from seawater by electrodialysis;227
10.2;3.2. Water Desalination;228
10.2.1;3.2.1. Seawater RO desalination;232
10.2.1.1;Dual-purpose plants;232
10.2.1.2;Energy recovery;234
10.2.1.3;Seawater intake;236
10.2.1.4;Alternate SWRO system designs;236
10.2.1.5;Case studies - Several examples of small and large SWRO plants are described below;237
10.2.2;3.2.2. Brackish water RO desalination;243
10.2.2.1;Case studies;245
10.2.3;3.2.3. Brackish water desalination by electrodialysis;251
10.2.3.1;ED/EDR industrial water desalting;254
10.2.4;3.2.4. High recovery/brine treatment membrane processes;255
10.2.4.1;Integrated membrane processes;255
10.2.4.2;Zero discharge desalination (ZDD);257
10.2.4.3;Hybrid membrane processes;257
10.3;3.3. High-Purity Water Production;258
10.3.1;3.3.1. Boiler water treatment;259
10.3.2;3.3.2. Microelectronics rinse water;261
10.3.3;3.3.3. USP grade water;266
10.3.3.1;USP plant operation modifications;268
10.4;3.4. Water Reclamation and Recycling;269
10.4.1;3.4.1. Industrial water treatment;270
10.4.2;3.4.2. Municipal water application;276
10.4.3;3.4.3. Submerged membrane filtration;281
10.5;3.5. MBR Sewage and Wastewater Treatment;288
10.5.1;3.5.1. Membrane bioreactor systems;288
10.5.2;3.5.2. Applications of MBRs;290
10.6;References;292
11;Chapter 4: Hybrid Membrane Plant Design and Operation;298
11.1;4.1. RO Membrane Plant Description;301
11.1.1;4.1.1. Pre-treatment system;301
11.1.2;4.1.2. RO membrane system;303
11.1.3;4.1.3. MB ion-exchange polishing;306
11.2;4.2. Plant Design and Controls;308
11.2.1;4.2.1. Granulated media filter;308
11.2.1.1;GMF design criteria;308
11.2.2;4.2.2. RO membrane system;308
11.2.2.1;RO design criteria;308
11.2.3;4.2.3. MB ion-exchange system;310
11.2.3.1;MB design criteria;310
11.2.4;4.2.4. System controls;311
11.3;4.3. System Operation;312
11.3.1;4.3.1. Start-up requirements;324
11.3.1.1;Granular media filters;324
11.3.1.2;RO membrane unit;325
11.3.1.3;MB deionisers;325
11.3.1.4;Miscellaneous equipment;325
11.3.2;4.3.2. Operation;325
11.3.2.1;Service operation checklist;326
11.3.2.2;Service run;327
11.3.3;4.3.3. Performance evaluation;331
11.4;4.4. System Diagnosis and Maintenance;333
11.4.1;4.4.1. Diagnostics;333
11.4.2;4.4.2. Process water pumps;333
11.4.3;4.4.3. Process water storage tanks;334
11.4.4;4.4.4. Chemical feed systems;335
11.4.5;4.4.5. Granular media filters;335
11.4.6;4.4.6. Cartridge filters;336
11.4.7;4.4.7. Heat exchangers;336
11.4.8;4.4.8. RO membrane system;337
11.4.9;4.4.9. MB ion exchangers;337
11.4.10;4.4.10. MB regeneration systems;338
11.4.11;4.4.11. Ultraviolet units;339
11.4.12;4.4.12. Preventive maintenance;339
11.5;4.5. RO plant equipment;341
11.5.1;4.5.1. Equipment selection;341
11.5.2;4.5.2. Equipment specifications;343
11.5.2.1;Feed water pumps;343
11.5.2.2;Granular media filters;343
11.5.2.3;Chemical feed systems;345
11.5.2.4;Cartridge filter;345
11.5.2.5;Feed water heat exchanger;345
11.5.2.6;RO unit;345
11.5.2.7;Water reuse tank;345
11.5.2.8;GMF backwash pumps;346
11.5.2.9;RO product water tank;346
11.5.2.10;RO water-distribution pumps;346
11.5.2.11;MB regeneration pump;346
11.5.2.12;Ultraviolet light units;346
11.5.2.13;MB ion exchangers;346
11.5.2.14;Cartridge filters;347
11.5.2.15;MB regeneration skids;347
11.5.2.16;Control panels;347
11.6;4.6. Membrane-Filtration System;347
11.6.1;4.6.1. Principle of operation;348
11.6.1.1;Continuous cross-flow operation;348
11.6.1.2;Semicontinuous dead-end filtration;349
11.6.1.3;Constant flux vs. constant pressure and critical flux;349
11.6.2;4.6.2. System equipment;350
11.6.3;4.6.3. Service and cleaning operations;351
11.6.3.1;Service cycle;351
11.6.3.2;Backwash/cleaning cycle;351
11.7;4.7. Summary;352
11.8;References;352
12;Chapter 5: Design, Energy and Cost Analyses of Membrane Processes;354
12.1;5.1. Membrane System Performance Correlations;355
12.1.1;5.1.1. RO/NF systems;355
12.1.2;5.1.2. UF/MF systems;356
12.2;5.2. Energy and Cost Survey of Membrane Processes;357
12.2.1;5.2.1. Energy consumption survey;357
12.2.1.1;Process A - single-pass RO seawater desalination;362
12.2.1.2;Process B - double-pass RO seawater desalination;364
12.2.1.3;Process C - brackish water RO desalination;364
12.2.1.4;Process D - surface water membrane filtration;365
12.2.1.5;Process E - biological wastewater membrane bioreactor treatment;366
12.2.1.6;Process F - industrial wastewater cross-flow membrane treatment;366
12.2.1.7;Process G - high-purity water;367
12.2.1.8;Process H1 - ultrapure water;367
12.2.1.9;Process H2 - power plant water;368
12.2.2;5.2.2. Temperature effect on energy consumption and membrane performance;368
12.2.2.1;SWRO design;369
12.2.2.2;BWRO design;371
12.2.2.3;Post-analysis;371
12.2.3;5.2.3. Capital and operating costs assessment;375
12.2.3.1;Water desalination costs;375
12.2.3.2;RO design for cost analyses;375
12.2.3.3;Desalination - Capex and Opex calculation basis;376
12.2.3.4;UF/MF water treatment cost figures;377
12.2.4;5.2.4. Electrodialysis energy consumption and costs;377
12.2.4.1;High salinity feed waters;379
12.2.5;5.2.5. Energy-saving options;379
12.3;References;381
13;Chapter 6: Appendix: Engineering Data and Notes;384
13.1;6.1. Glossary/Terminology;384
13.2;6.2. Membrane Polymer Performance;395
13.3;6.3. Chlorination of PA Membranes;397
13.4;6.4. Fluid Flow in Microporous Membranes;399
13.5;6.5. CP and Mass Transfer Coefficient;401
13.6;6.6. Surfactant Micelles Size Correlation;402
13.7;6.7. Deioniser Design;404
13.7.1;6.7.1. DI system design basis;405
13.7.2;6.7.2. Cation ion-exchanger design;405
13.7.3;6.7.3. Anion ion-exchanger design;406
13.8;6.8. Process Controls;407
13.9;6.9. Centrifugal Pumps;409
13.9.1;6.9.1. Pump selection criteria;409
13.9.2;6.9.2. Pump controls;411
13.10;6.10. Control Valves;412
13.11;6.11. Materials Properties;416
13.11.1;6.11.1. Stainless steel;416
13.11.2;6.11.2. Plastics;417
13.11.3;6.11.3. SS vs. plastics;418
13.12;6.12. Process Validation;418
13.13;6.13. RO/NF Feed Water Analysis;419
13.14;6.14. Chemistry of Feed Water Treatment in Membrane Plants;421
13.14.1;6.14.1. Mineral precipitation;421
13.14.2;6.14.2. Calcium carbonate chemistry;422
13.14.3;6.14.3. Procedure for calculating LSI value;424
13.14.4;6.14.4. Silica and boron removal;424
13.15;6.15. Wastewater Treatment;426
13.15.1;6.15.1. Common constituents in wastewater;426
13.15.2;6.15.2. Trace contaminants in wastewater;427
13.16;6.16. Conversion Factors;427
13.16.1;Area;427
13.16.2;Density;427
13.16.3;Diffusivity;428
13.16.4;Flux;428
13.16.5;Force and pressure;428
13.16.6;Length;428
13.16.7;Mass;428
13.16.8;Mass transfer coefficient;428
13.16.9;Power, work, and energy;429
13.16.10;Temperature;429
13.16.11;Velocity;429
13.16.12;Viscosity;429
13.16.13;Volume;429
13.16.14;Molar concentration - TDS - conductivity chart (NaCl, 25C);429
13.17;6.17. Physical and Chemical Data;430
13.18;6.18. Membrane Data;436
13.19;References;439
14;Index;442

Leseproben

Chapter 2 Water and Membrane Treatment
Abstract
Water treatment in membrane plants implies pre-treatment and often post-treatment also. Pre-treatment is mandatory because membrane systems are susceptible to fouling. The extent of physical and chemical pre-treatment depends on the quality of raw water, e.g. well water typically require minimum pre-treatment, whereas wastewaters require extensive pre-treatment. Both physical and chemical pre-treatment processes and technologies are discussed in detail. Post-treatment technologies are also detailed. Post-treatment is required depending on the application of product water at the point-of-use, e.g. RO permeate is remineralised prior to distribution for potable use. Conversely, RO product water is polished to further demineralise it for applications that require high-purity water (pharmaceuticals) or ultrapure water (microelectronics). Membrane scaling/fouling, process design guidelines to minimise fouling and membrane cleaning are discussed in detail. This chapter describes in detail membrane system designs including important design features and system controls. Keywords Water treatment Scaling Fouling Cleaning Sanitisation Electro-membrane processes Membrane filtration “Whisky is for drinking, water is for fighting over.” — Mark Twain 2.1 Priceless Water
Current shortages of potable water around the world and the looming water scarcity, especially in the developing countries, is the greatest crisis facing humanity in the twenty-first century and possibly beyond [1–3]. According to the UN, 1.2 billion people do not have access to clean drinking water, and half of the world’s population lacks adequate water purification. By 2025, 1.8 billion people will be living in areas likely to experience absolute water scarcity [1]. One-third of the world’s population that currently lives in water-stressed countries is expected to rise to two-thirds by 2025. By the year 2050, between 2 and 7 billion people will face water shortages. Inadequate supply of potable water, coupled with higher water demand in developing countries due to rapid population growth and industrialisation, are among the major reasons for the worsening water situation. Nearly 60% of illness around the world is due to contaminated water and lack of sewer treatment. According to the World Health Organisation (WHO), about 2.4 billion people do not have access to basic sanitation facilities, and more than one billion people do not have access to safe drinking water. Unclean water causes diarrhoea, cholera, dysentery, guinea worm infection, typhoid, intestinal worm infection and trachoma [3]. According to the WHO, four billion people get diarrhoea every year that kills nearly 1.8 million people of which 90% are children under the age of five. Although water is the most common substance in the world, only 3% is fresh water (97% is seawater), and only 1% is available for human consumption. According to many experts even 1% is adequate since fresh water supply is infinite because of the natural water cycle [1,3]. However, the availability and application of water is uneven around the world; in water-stressed countries such as India, China as well as in countries in South-East Asia, Northern Africa and North-East Africa, the situation is especially acute. In India, for example, groundwater from aquifers is being pumped at nearly twice the rate of aquifer recharge from rainfall, while both the demand for water and the country’s population is expected to increase at least 50% by 2050 [4]. Further, the quality of available or useable water is decreasing due to increasing water pollution from industrial, agricultural and other human activity. In fact, it is becoming a major environmental problem today. For example, due to excessive use of fertilisers in India’s bread-basket state of Punjab during the last 40 years, the nitrate level in groundwater has exceeded the carcinogenic level of 50 parts per million (ppm) in many areas [4]. Nitrates are a health concern because they are converted to nitrites which interfere with hemoglobins to exchange oxygen in blood. This can cause serious problems especially for fetus and children. Nitrate residues also accelerate eutrophication – enrichment of ponds and lakes by nutrients that results in oxygen depletion – of water bodies. Another major source of water pollution is chlorine, which is used in pulp and paper bleaching, metal processing, pharmaceutical manufacturing, textile dyeing and cleaning, corrosion control, photography and water treatment [3]. Arsenic, a carcinogen at concentrations greater than 10 parts per billion (ppb), occurs naturally in groundwater in several countries. The problem is especially acute in Bangladesh where 60 million people are seriously affected by arsenic in natural drinking water. Similarly, endocrine-disrupting compounds in wastewaters from pharmaceutical, cosmetic and food processing plants in even trace amounts (ng/l) are carcinogenic, and pose a problem due to incomplete removal by conventional primary and secondary treatment processes. Prominent among the endocrine disrupting contaminants are steroid hormones that are continuously excreted by humans and animals. Scarcity of water resources is also often the limiting factor for economic and social development. Water is needed not just for drinking, household purposes and for agriculture, but also for manufacturing goods, food processing and power generation. Industrial water purification has been growing in the US at approximately twice the GNP, according to the American Society of Testing Materials. Highly purified water plays a critical role in the manufacture and use of advanced materials such as biotechnology, quenching of turbine forgings, final rinsing of fluorinated polymer films, manufacture of new glass laminates, and the use of ultrahigh purity (resistivity = 18.2 M?-cm) water in the production of graphite fibres and microchips. Current and looming water scarcity and the effects of environmental pollution, groundwater degradation and global warming on water availability can have severe and adverse effects on the world economy, especially developing countries. This may lead to human displacement at an unprecedented scale. It is imperative, therefore, that existing water resources are preserved and advanced treatment processes are deployed to provide potable water. Water demands and its quality depend on its usage, which varies from region to region. Water shortages have been attributed to varied reasons such as nearly 50% loss due to leaks in piped water systems and inefficient usage of water (70–90% of available water) for agricultural irrigation. For example, intensive and indiscriminate pumping of groundwater is depleting the huge Ogallala aquifer in middle America eight times faster than it is being replenished. Similarly, excessive use of water required for high-yielding grain crops is depleting groundwater in the Punjab region of India [4]. Water scarcity problems, however, can be solved by a combination of water conservation, reclamation, recycling and desalination, as discussed in Chapter 3. Industrial water management relies heavily on separation science, e.g. coagulation and flocculation are used to separate or remove suspended solids from water for clarification by accelerating their settlement rates during conventional treatment. Membrane filtration processes – ultrafiltration (UF) and microfiltration (MF) – are being used for treating waste water in lieu of coagulants such as aluminium sulphate (alum) and polymers, thereby eliminating the production of sludge and its disposal (see Figure 3.47). Separation techniques such as adsorption, ion-exchange, membrane separation and chemical coagulation and precipitation are being deployed for removing arsenic from groundwater. RO membrane separation has been traditionally used for seawater and brackish water desalination, and production of high-purity water for food, pharmaceutical processing and industrial waste treatment, as discussed in Chapter 1. The development of nanofiltration (NF) membranes has opened up many areas of application including water softening, removal of disinfection by-product precursors (trihalomethanes), removal of total organic carbon (TOC), food processing and industrial water treatment [5]. Low-pressure membrane filtration using MF and UF membranes is becoming the separation processes of choice for municipalities for removing turbidity and pathogens [6,7]; membrane filtration has proven to be very effective and reliable in removing microbiological parasites, Giardia and Cryptosporidium, since first used in this application in 1995. Increasingly integrated UF/MF-RO membrane systems are being used for the reclamation of industrial and municipal water where UF or MF replaces conventional filtration for treating RO feed water, e.g. treating secondary treatment effluent with membrane filtration followed by RO membrane treatment for producing water for industrial use and aquifer recharge, and RO seawater desalination pre-treatment [8]. Several case studies of integrated membrane systems used in water treatment are discussed in Chapter 3. The reasons why membrane filtration is becoming the preferred technology for water treatment complementing RO or NF membrane systems are detailed...