Operation and Optimisation of Microfiltration & Ultrafiltration Membrane Processes

Practical Guide to the Operation & Optimisation of Microfiltration & Ultrafiltration Membrane Processes

K at h y No r t h co tt, G re g Cre e k a n d Pe t e r M o s s e

The Authors Dr Kathy Northcott is the R&D Manager - Veolia Australia & New Zealand, and a specialist in water treatment, wastewater treatment and water recycling processes. Greg Creek is a senior training officer with Water Industry Training Consultants. Dr Peter Mosse provides specialist technical support in water and wastewater technology.

Acknowledgements The authors wish to thank Konrad Mueller and Colin Ellett from Veolia ANZ; Stephen Wilson from Water Industry Training Consultants; and Rick Maffescioni from Aqua Manage for their critical review of the manuscript. Thanks also to Veolia ANZ, Melbourne Water, Dunedin City Council, Barwon Water, DuPont Water Solutions and Victoria University for providing some of the photos appearing in this publication. The authors acknowledge the contribution of all the sponsors who have provided funding for the publication of this book. • New South Wales Water Directorate • Queensland Water Directorate (qldwater) • TRILITY • Victorian Water Industry Association (VicWater) • Water Services Association of Australia (WSAA) Particular thanks are extended to the Water Industry Operators Association (WIOA) for their commitment to improving the skills of operations staff in the water industry and for coordinating the development of this resource as part of the process. The efforts of WIOA MD, George Wall, in proof reading the final document and for organising the layout and publication of this book have been invaluable.

Publications Details First Edition, May 2021.

Ordering More Copies An order form is available from the WIOA website (www.wioa.org.au) for people wishing to order additional copies or any of the other Practical Guides to Water Treatment or Wastewater Treatment.

Other WIOA Publications Practical Guides to Water Treatment. • Practical Guide to Understanding and Managing Surface Water Catchments. • Practical Guide to the Optimisation of Chemical Dosing, Coagulation, Flocculation and Clarification. • Practical Guide to the Operation and Optimisation of Media Filters. • Practical Guide to the Operation and Optimisation of Chlorine and Chloramine Disinfection. • Practical Guide to the Operation and Optimisation of Distribution Systems.

Practical Guides to Wastewater Treatment. • Practical Guide to Odour Control in Sewage Transport Systems. • Practical Guide to the Operation and Optimisation of Activated Sludge Wastewater Treatment Plants.

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General Introduction The WIOA Practical Guides to Water Treatment focuses on each of the major steps in the process from catchment to tap, namely: 1. 2. 3. 4. 5. 6.

Catchment. Chemical dosing, coagulation, flocculation and clarification. Media Filtration. Membranes. Disinfection. Distribution.

Each guide provides practical advice regarding the management and operation of each of the critical control points identified by Utilities as they implement the Australian Drinking Water Guidelines Framework for the Management of Drinking Water Quality (ADWG 2011), state based legislation such as the Safe Drinking Water Act 2003 in Victoria, or a HACCP or ISO program. An underlying objective of each of the guides is that all the way through, operational staff should be able to make mental notes to themselves along the lines of: • That’s a good idea. • We should be doing that. • We can start on that immediately. The guides are not about identifying costly solutions but simply identifying ways to get the best out of what is available at any particular time. The aim is to provide suggestions and hints that can be implemented easily, cheaply and immediately in the field. Finally, the Australian Drinking Water Guidelines are concerned “both with safety from a health point of view and with aesthetic quality of drinking water”. These guides deal with both of these aspects; not just with safety aspects. They are about getting the absolute best out of the system, in order to deliver the absolute best quality drinking water to the consumer.

Feedback Requested These guides have been written to help operators peform their jobs effectively and to help operators understand the vitally important roles they fulfil within the water industry. The authors would be pleased to receive any feedback on this guide. Suggestions for further information, or areas where additional explanation would have aided understanding, can all help to make any future editions stronger and more useful for operators in our industry. Any suggestions can be directed by e-mail to the Water Industry Operators Association of Australia (WIOA) at info@wioa.org.au or by post to PO Box 6012, Shepparton, Victoria, 3632.

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Contents 1. Hazards, Risks and Control Points................................................................................. 4

• Hazards and Drinking Water............................................................................................................. 4 • Pathogens are the Main Hazards in Drinking Water ........................................................................ 5 • Other Hazards................................................................................................................................... 8 • Control Points.................................................................................................................................... 9 • Critical Limits and Target Criteria.................................................................................................... 10 • Corrective Actions........................................................................................................................... 11 • Responsibilities............................................................................................................................... 12

2. Membranes and Public Health...................................................................................... 13 • Operating Criteria and Performance Parameters............................................................................ 15

3. Introduction to Membranes........................................................................................... 17

• Membranes and Water Treatment................................................................................................... 17 • Basic Membrane Terminology......................................................................................................... 17 • Membrane Filtration Processes....................................................................................................... 19 • How Membranes Work.................................................................................................................... 20 • Membrane Fouling.......................................................................................................................... 21 • Membrane Materials........................................................................................................................ 21 ◦ Hydrophobicity............................................................................................................................ 22 ◦ Oxidant Tolerance....................................................................................................................... 23 • Flow Configurations......................................................................................................................... 23 • Types of Membrane Systems.......................................................................................................... 26 • Membrane Pre-treatment................................................................................................................ 30 • Membrane Resistance ................................................................................................................... 31 • Flux................................................................................................................................................. 31 ◦ Normalised Flux (Correction for Viscosity).................................................................................. 32 • Transmembrane Pressure and Membrane Permeability................................................................. 33

4. Optimisation of Membrane Filtration Systems ........................................................... 34

• 1. Know Your Process..................................................................................................................... 34 • 2. Know Your Plant ......................................................................................................................... 34 • 3. Feedwater Quality and Pre-treatment......................................................................................... 35 ◦ Prefiltration.................................................................................................................................. 35 ◦ Feedwater Coagulation............................................................................................................... 37 ◦ Use of Polymers......................................................................................................................... 38 • 4. Membrane Integrity..................................................................................................................... 38 • 5. Membrane Fouling...................................................................................................................... 39 • 6. Flux............................................................................................................................................. 40 • 7. Backwashing and Chemical Cleaning......................................................................................... 40 • 8. Inspections of Membrane Elements............................................................................................ 40 • 9. Calibrate Gauges, Meters and Associated Instrumentation........................................................ 42 • 10. Reduce the Risks Associated with Washwater Recycling ........................................................ 43

5. Membrane Cleaning....................................................................................................... 44

• Backwashing of Hollow Fibre Membranes...................................................................................... 44 • Backwashing of Immersed Membranes.......................................................................................... 46 • Chemical Cleaning.......................................................................................................................... 47 ◦ 1. Chemically Enhanced Backwash (CEB) ................................................................................ 47 ◦ 2. Chemical Clean-in-Place (CIP)............................................................................................... 47 • Monitoring the Effectiveness of Cleaning........................................................................................ 50 • Management of Chemical Sludge................................................................................................... 51

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6. Membrane Maintenance................................................................................................. 52

• Record Keeping............................................................................................................................... 56 • Using Maintenance Statistics.......................................................................................................... 56 • Storage and Preservation of Membranes........................................................................................ 57 • Membrane Autopsies...................................................................................................................... 58 • Trouble Shooting............................................................................................................................. 63

7. Membrane Replacements.............................................................................................. 64

• When to Change out Membranes................................................................................................... 64 • Preparation for Changing out Membranes...................................................................................... 65 • Decommissioning and Dismantling ................................................................................................ 67 • Replacement of Membrane System Components........................................................................... 68 • Recommissioning the Membrane System....................................................................................... 69

8. Nanofiltration and Reverse Osmosis............................................................................ 70

• Comparison of NF and RO to MF and UF....................................................................................... 70 ◦ Sizes of Particles Removed........................................................................................................ 70 ◦ Operating Pressures................................................................................................................... 70 ◦ How NF and RO Membranes Work............................................................................................ 71 ◦ Diffusion and Osmosis................................................................................................................ 71 ◦ Osmotic Pressure and Reverse Osmosis .................................................................................. 72 ◦ Actual Membrane Performance.................................................................................................. 72 • The RO System. Membrane Elements, Stages and Arrays ........................................................... 73 ◦ Stages and Recoveries............................................................................................................... 74 ◦ Importance of Pre-Treatment...................................................................................................... 76 ◦ Silt Density Index (SDI)............................................................................................................... 77 ◦ Integrity Testing for RO Membranes........................................................................................... 78 ◦ Post Treatment........................................................................................................................... 79 ◦ Causes of Membrane Failure..................................................................................................... 80 ◦ Energy Recovery ....................................................................................................................... 81 ◦ Concentrate Management.......................................................................................................... 81 ◦ Pressure Vessel Safety ............................................................................................................. 82 • Terminology .................................................................................................................................... 82

9. Closing Words................................................................................................................ 83

• Further Reading.............................................................................................................................. 83

Case Study in Membrane Troubleshooting...................................................................... 84

• 1. Impacts of Raw Water Quality Changes on Microfiltration Plants .............................................. 84 ◦ Monitoring Membrane Performance........................................................................................... 86 ◦ Membrane Cleaning Trials.......................................................................................................... 87 ◦ Review of Membrane Condition and Performance..................................................................... 88 ◦ Follow-up Autopsies................................................................................................................... 88 ◦ Conclusions................................................................................................................................ 89 • 2. Importance of Pre-Treatment...................................................................................................... 90

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