Choulis Book (Abstract Table Of Contents)

CHOULIS KONSTANTINOS
Mechanical & Industrial Engineer,
Diplom Ingenieur (Dipl. – Ing.), MEng (equivalent), CEng (equivalent).
Water Quality & Treatment and Process Development Consultant,
Reverse Osmosis Desalination Specialist.

DESIGN AND CONSTRUCTION PARAMETERS OF
REVERSE OSMOSIS DESALINATION PLANTS –
STUDY AND ANALYSIS

ATHENS, GREECE, November 2011
i

ABSTRACT

The global demand for water can no longer be met due to the constant reduction of the
available groundwater and surface water sources and their simultaneous
contamination to an irreversible level. The problem is solved in 2 ways.
The first and cheapest option is the treatment of the available polluted and / or
brackish groundwater and surface water.
The second and most expensive option is the production of clear freshwater by
treating seawater, given that seawater is an unlimited source.
The reverse osmosis is the most effective technology which is applied in both cases.

The design and manufacturing of water treatment and RO plants demands knowledge
of a series of sciences of which the professionals insist on not cooperating with each
other. The involving sciences are: mechanical engineering, electrical & automation
engineering, chemical engineering, chemistry, microbiology, medicine, international
law for the drinking water (guidelines-standards), environmental engineering
(environmental consequences study) and geology.
A water professional, and especially a water treatment and desalination professional,
should have some knowledge of all the above. Unfortunately, during my career, I
haven't met any professional acquiring the above combination of knowledge. And I
think that this is the most important reason for the fact that the majority of pubic water
networks globally provide unacceptable water.

The end product water should be healthy, tasty, legal, non-corrosive, non-scaling.
This means water safe for human consumption and in the same time safe for any kind
of hydraulic facilities/devices/equipment.
Very soft and very hard water is dangerous.
Optimum drinking water electrical conductivity: 300-500 µS/cm.
Optimum water hardness for both drinking use and hydraulic installations & devices
use: 180-200 mg/L as CaCO3.

When an engineer has to deal with the consulting, the design, the simulation, the
construction, the installation, the operation and the maintenance of a water treatment
plant, he has first of all to be able to answer the following questions:
• What is the problem of the water?
• What is the desired quality and quantity of the product water?
• Which are all the possible technologies that can be applied effectively and
what are the characteristics of each one?
After answering these questions, the engineer decides which the best combination of
methods for each case of problem is.

This dissertation analyzes all the parameters related to reverse osmosis desalination
plants.
There is a full analysis of every section of such facilities: water intakes, water pre-
treatment, reverse osmosis system and water post-treatment.
At the end, there is a case study dealing with the design and manufacturing of a small-
scale reverse osmosis plant treating brackish feedwater.

The purpose of this dissertation is the description of the guidelines and the steps that
must be followed for the proper preparation of a design and construction study of
a reverse osmosis desalination plant and furthermore the implementation of
these guidelines at a real case study.
ii

TABLE OF CONTENTS

CHAPTER 1

WATER RESOURCES – DESALINATION – REVERSE OSMOSIS

1.1. The Global Situation of Water Resources p. 1
1.1.1. The Situation of Water Resources Today p. 1
1.1.2. Prediction of the Situation of Water Resources in the Future p. 2
1.1.3.Total Global Saltwater and Freshwater Estimates p. 3
1.1.4. The Role of Desalination p. 5
1.2. Main Definitions of Desalination and Classification of the Various
Desalination Processes p. 7
1.2.1. Desalination is Part of the Water Cycle p. 7
1.2.2. Streams and Energy p. 8
1.2.3. Energy Demands p. 9
1.2.4. Pros & Cons of the Main Desalination Technologies p. 10
1.2.5. Environmental Effects of Reverse Osmosis Desalination Units p. 12
1.3. Reverse Osmosis and NanoFiltration Fundamentals p. 12
1.3.1. History p. 12
1.3.2. Desalination Technologies and Filtration Methods p. 13
1.3.3. Operating Principles of Reverse Osmosis and NanoFiltration p. 18
1.3.4. Membrane Sheet Description p. 26
1.3.5. Membrane Element Performance p. 30
1.3.6. Membrane Element Structure p. 32
1.3.7. Membrane Element Characteristics p. 35
1.4. References p. 41

CHAPTER 2

WATER INTAKE SYSTEMS

2.1. Introduction to the Design of Desalination Systems p. 42
2.2. Water Intakes p. 43
2.2.1. Introduction to Raw Water Intake Systems p. 43
2.2.2. Offshore (Open - Ocean) Water Intakes p. 45
2.2.2.1. Introduction p. 45
2.2.2.2. Velocity Caps – Passive Screens p. 48
2.2.3. Filtration Intakes p. 52
2.2.3.2. Conventional Vertical Wells (Beach Wells) p. 53
2.2.3.3. Horizontal Wells (Directional Wells) p. 55
2.2.3.4. Collector Wells (Ranney Collectors) p. 57
2.2.3.5. Beach Galleries p. 59

iii

CHAPTER 3

WATER CHEMISTRY AND PRETREATMENT SYSTEMS

3.1. Water Chemistry – Main Terms and Parameters p. 64
3.2. Pretreatment Systems p. 70
3.2.1. Introduction p. 70
3.2.2. RO & NF Membranes Feedwater Types - Classification p. 73
3.2.3. Nominal Rejection Characteristics of Thin Film Composite (TFC)
Reverse Osmosis Membranes p. 83
3.3. Scaling Prevention p. 86
3.3.2. Acid Addition p. 88
3.3.3. Chemical Antiscalant (Scale Inhibitor) Addition p. 89
3.3.4. SAC (Strong-Acid-Cation) Resin Softening p. 91
3.3.5. WAC (Weak-Acid-Cation) Resin Dealkalization p. 94
3.3.6. Lime Softening p. 96
3.3.7. Preventive Membranes Cleaning p. 97
3.3.8. Operation Parameters Adjustment p. 98
3.4. Scaling Calculations p. 99
3.4.2. Calcium Carbonate Scaling Prevention p. 101
3.4.2.1. Brackish Water p. 101
3.4.2.2. Seawater p. 108
3.4.3. Calcium Sulfate Scaling Prevention p. 113
3.5. Prevention of Colloidal and Particulate Membrane Fouling p. 116
3.5.1. Evaluation of Colloidal Fouling Potential p. 116
3.5.2. Media Filtration – Sand/Anthracite Filters p. 121
3.5.2.2. Selection of Media Grain Size – Media Specification p. 123
3.5.2.3. Slow Sand Filtration vs Rapid Sand Filtration p. 143
3.5.2.4. Filter Aggregate (Filter Ag.) p. 144
3.5.3. Oxidation–Filtration p. 145
3.5.3.1. Manganese Greensand Filter p. 146
3.5.3.2. Birm Filter p. 147
3.5.3.3. Pyrolox Filter (Manganese Dioxide – MnO2) p. 148
3.5.4. Coagulation-Flocculation-Filtration p. 149
3.5.5. Coagulation-Flocculation p. 151
3.5.6. Microfiltration (MF) / Ultrafiltration (UF) Membranes p. 152
3.5.7 Sediment Filters (Cartridge Filters – Bag Filters) p. 153
3.5.7.1. Basic Principles p. 153
3.5.7.2. Sediment Filters Technical Parameters p. 155
iv

3.5.7.3. Cartridge Filters p. 157
3.5.7.4. Bag Filters p. 161
3.5.7.5. Cartridge Filters vs Bag Filters p. 163
3.5.7.6. Polypropylene p. 165
3.5.8. Other Methods of Colloidal and Particulate Fouling Prevention p. 166
3.5.9. System Design and Operation p. 168
3.6. Biofouling (Biological Fouling) Prevention p. 169
3.6.2. Evaluation of Biofouling Potential p. 171
3.6.2.1. Culture Techniques p. 172
3.6.2.2. TBC – Total Bacteria Count p. 173
3.6.2.3. AOC - Assimilable Organic Carbon p. 174
3.6.2.4. BFR - Biofilm Formation Rate p. 174
3.6.3. Chlorination / Dechlorination p. 175
3.6.3.1. Chlorination p. 175
3.6.3.2. Dechlorination p. 180
3.6.3.2.1. Activated Carbon p. 181
3.6.3.2.2. KDF p. 190
3.6.3.2.3. SMBS (Sodium MetaBiSulfite) p. 191
3.6.3.3. Redox Potential p. 193
3.6.4. SBS – Sodium BiSulfite p. 194
3.6.5. DBNPA p. 194
3.6.6. Combined Chlorine - Chloramines p. 196
3.6.7. Copper Sulphate p. 196
3.6.8. Ozone p. 197
3.6.9. Other Disinfection Chemicals p. 197
3.6.10. Biofiltration p. 197
3.6.11.Microfiltration (MF) / Ultrafiltration (UF) p. 198
3.6.12. UltraViolet Irradiation (UV) p. 198
3.6.13. Fouling Resistant (FR) RO Membranes p. 199
3.7. Organics Fouling Prevention p. 199
3.7.1. TOC – Total Organic Carbon p. 199
3.7.2. BOD – Biochemical Oxygen Demand p. 200
3.7.3. COD - Chemical Oxygen Demand p. 200
3.7.4. Humic Substances p. 201
3.7.5. Oils & Greases p. 201
3.7.6. Effluent p. 201
3.7.7. THMs – TriHaloMethanes p. 201
3.8. Prevention of Membrane Degradation p. 202
3.9. Iron & Manganese Fouling Prevention p. 202
3.10. Aluminum Fouling Prevention p. 207
3.11. Summary Tables – Examples of RO Pretreatment Systems p. 208

v

CHAPTER 4

REVERSE OSMOSIS MEMBRANES SYSTEM DESIGN

4.1. Introduction p. 218
4.2. Non-Stop vs Intermittent RO System Operation p. 220
4.3. Single Model (One Pressure Vessel) System p. 223
4.4. Pressure Vessels Array - Single-Stage System p. 225
4.5. Multi-Stage System p. 226
4.6. One-Way Circuit vs Brine Recirculation p. 227
4.7. Double-Pass RO System p. 233
4.8. Special Design Considerations p. 236
4.9. Guidelines for the Design of Reverse Osmosis Membranes Systems p. 237
4.9.1. Feedwater SDI correlation with Permeate Flux Rate and
Membranes Recovery p. 237
4.9.2. Membranes Operation Limits p. 238
4.9.3. Average Flux Rate p. 238
4.9.4. System Cleaning Frequency and Operation Limits Excess p. 239
4.9.5. Conservative Design p. 239
4.9.6. Feedwater physical & chemical parameters p. 240
4.9.7. Standards and Guidelines for the Design of Small-Scale
and Medium-Scale Membranes Systems with
Medium-Sized Elements (2,5’’ & 4’’Elements) p. 241
4.9.7.1. Small-Scale Systems p. 241
4.9.7.2. Medium-Scale Systems p. 242
4.9.7.3. Large-Scale Systems - 8’ ’ Elements p. 244
4.9.7.4. Tables of Guidelines Standards for the Design
of Reverse Osmosis Systems for each type of
Feedwater and each Type & Size of Elements p. 245
4.9.7.5. Definitions for the Terms of Tables 4.3 - 4.6 p. 249
4.10. Steps for the Design of Membrane Systems p. 250
4.10.1. Step 1: Basic Information for the Design of Membranes
Systems and Raw Feedwater Chemical Analysis p. 250
4.10.2. Step 2: Choice of Flow Type (One-Way or Brine
Recirculation), System Operation Type (Non-Stop or
Intermittent) and Number of RO Passes (Single-Pass or
Double-Pass) p. 253
4.10.3. Step 3: Choice of Elements Type p. 254
4.10.4. Step 4: Choice of Permeate Average Flux Rate p. 254
4.10.5. Step 5: Calculation of the Number of Needed Elements
and Pressure Vessels p. 255
4.10.6. Step 6: Choice of the Number of System Stages p. 255
vi

4.10.7. Step 7: Choice of the Staging Ratio in a Multi-Stage
System (Ratio of the Number of Pressure Vessels in
Consecutive Stages) p. 257
4.10.8. Step 8: Adjustment and Balancing of Permeate Flow Rate p. 258
4.10.9. Step 9: RO System Optimization and Analysis p. 259
4.11. Equations and Parameters p. 260
4.11.1. Basic Parameters – Symbols Definitions p. 260
4.11.2. Basic Equations p. 262
4.11.2.1. Osmotic Pressure p. 262
4.11.2.2. NDP - Νet Driving Pressure p. 264
4.11.2.3. Permeate Flow Rate (Q) p. 265
4.11.2.4. Salts (Brine) Flow Rate (Qs) p. 266
4.11.2.5. Permeate Salinity (Cp) p. 267
4.11.2.6. Salts Passage (SP) p. 267
4.11.2.7. Salts Rejection (R) p. 268
4.11.2.8. Permeate Recovery (Y) p. 268
4.11.2.9. Salts Concentration Polarization Factor (pf) p. 269
4.11.2.10. Temperature p. 270
4.11.2.11. Temperature Correction Factor (TCF) p. 271
4.11.2.12. Calculation of the Real Performance of
a Membrane based on the Standard
Conditions of Reference p. 273
4.11.3. Analytical Equations for the Calculation a System
Performance p. 274
4.11.3.1. Equations for the Calculation of each Single
Element Performance p. 274
4.11.3.2. Equations for the Calculation of the System
Average Performance p.275

CHAPTER 5

SYSTEM COMPONENTS

5.1. Pumps – Energy Consumption p. 279
5.1.1.1. Pumps Definitions p. 279
5.1.1.2. Pumps Classification p. 280
5.1.1.3. Centrifugal Pumps p. 280
5.1.1.4. Positive Displacement Pumps p. 281
5.1.1.5. Pumps in Reverse Osmosis Desalination Plants p. 283
5.1.2. Intake Pump p. 284
5.1.3. Feed Pump – Transfer Pump p. 284

vii

5.1.4. High Pressure Pumps System p. 285
5.1.4.2. High Pressure Pump p. 285
5.1.4.3. Energy Recovery Devices p. 286
5.1.4.3.1. Energy Consumption p. 286
5.1.4.3.2. Energy Recovery Systems Classification p. 288
5.1.4.3.3. Pelton Turbines p. 288
5.1.4.3.4. Work-Pressure Exchangers p. 289
5.1.4.4. Motors p. 291
5.1.4.5. Calculations for the choice of H.P. Pump and
Driving Motor for a Small-Scale R.O. p. 291
5.1.5. Other Pumps p. 293
5.2. Emergency Alarms and Switches (Stand-by / Shutdown) p. 294
5.3. Control Instruments and Valves p. 296
5.3.1. Display Control Instruments p. 296
5.3.2. Valves p. 298
5.3.3. Optional Equipment p. 300
5.4. Tanks p. 301
5.5. Pressure Vessels p. 303
5.6. Construction Materials – Prevention of Corrosion p. 304

CHAPTER 6

WATER POST-TREATMENT SYSTEMS
6.1. Introduction p. 311
6.2. Permeate Blending with Pre-Treated Feedwater p. 313
6.3. Chemicals Addition – Water Stabilization p. 317
6.3.2. Lime (Calcium Hydroxide) p. 319
6.3.3. Soda Ash (Sodium Carbonate) p. 320
6.3.4. Baking Soda (Sodium Bicarbonate) p. 320
6.3.5. Caustic Soda (Sodium Hydroxide) p. 321
6.4. pH Adjustment Systems p. 321
6.4.2. Caustic Chemicals (Caustic Soda, Caustic Potash) p. 322
6.4.3. Soda / Potash p. 323
6.4.4. Aeration Systems p. 324
6.4.5. Calcium Carbonate Precipitation – Limestone
Contactors, Calcite and/or Corosex Filters p. 325
6.5. Alkalinity Adjustment p. 327
6.5.1. Alkalinity, Scaling and Red Water p. 327

viii

6.5.2. Alkalinity Adjustment (Bicarbonate Stabilization – HCO3) p. 328
6.6. DIC (Dissolved Inorganic Carbon) Adjustment Systems p. 329
6.7. Water Hardness Increase p. 330
6.7.2. Remineralization Methods of Desalted Seawater p. 331
6.7.3. Soft or Desalted Water Reminerization by Limestone Dilution p. 333
6.7.4. Marble Filtration p. 333
6.7.5. Point of Use Calcium and Magnesium Addition by
Under-counter Devices p. 334
6.7.6. Target Values for Added Calcium p. 334
6.8. Addition of Chemical Corrosion Inhibitors p. 335
6.8.1. Phosphate Addition p. 335
6.8.2. Silicate p. 337
6.9. Water Corrosiveness Indexes p. 338
6.9.2. Summary p. 339
6.9.3. Misconceptions p. 339
6.9.4. Relevance p. 339
6.9.5. Langlier Saturation Index (LSI) p. 341
6.9.6. Stiff Davis Saturation Index (SDSI) p. 343
6.9.7. Ryznar Stability Index (RSI) p. 343
6.9.8. Calcium Carbonate Precipitation Potential (CCPP) p. 344
6.9.9. Larson Index p. 348
6.9.10. Conclusions p. 348
6.10. Product Water Disinfection p. 349
6.10.2. Use of Ultra-Violet Lamps for Water Disinfection p. 355
6.10.2.2. Arc Lamps for Water Treatment p. 356
ANNEX DIC p. 376

CHAPTER 7

CASE STUDY: DESIGN AND MANUFACTURING OF A SMALL-SCALE
BRACKISH WATER REVERSE OSMOSIS DESALINATION SYSTEM

7.1. Step 1: Basic System Parameters p. 383
7.2. Step 2: Recirculation p. 388
7.3. Step 3: Choice of the Membrane Elements type p. 388
7.4. Step 4: System Average Flux p. 391
7.5. Step 5: Elements Number p. 391
7.6. Step 6: System Analysis - Optimization p. 391
7.7. Choice of High Pressure Pump and Driving Motor p. 398
ix

7.8. Low Pressure (Feed) Pump p. 403
7.9. Antiscalant Injection Metering Pump p. 404
7.10. Display Control Instruments p. 407
7.11. Valves p. 408
7.12. Protection Switches p. 409
7.13. System Flowchart p. 410
7.14. System Operation Control Microcomputer p. 411
7.14.1. Controller Display Panel p. 412
7.14.2. Controller Terminals – Rear Side p. 415
7.14.3. Controller Operations Sequence p. 417
7.14.4. Electrical Panel p. 418
7.15. End R.O. System Control Panel p. 419
7.16. View of the End Product R.O. System p. 420
7.17. R.O. System Operation Results p. 423
7.18. Feasibility Analysis p. 424
ANNEX
Conductivity Conversion Factor based on the Temperature Value p. 430

CHAPTER 8

CONCLUSIONS - SUGGESTIONS

8.1. Conclusions p. 431
8.2. Suggestions for Future Research p. 433

ANNEX

Desalination Terms Definitions

x

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