N A Z I H K . S H A M M A S L A W R E N C E K . W A N G

Hydraulics, Distribution and Treatment

WATER ENGINEERING

Water Engineering

Water EngineeringHydraulics, Distribution and Treatment

First Edition

Nazih K. ShammasUniversity of Michigan, Ann Arbor, MI, USA (Ph.D.)N.K.Shammas@Gmail.com

Lawrence K. WangRutgers University, New Brunswick, NJ, USA (Ph.D.)LawrenceKWang@Gmail.com

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Library of Congress Cataloging-in-Publication Data:

Shammas, Nazih K.Water engineering : hydraulics, distribution, and treatment / Nazih K. Shammas, Lawrence K. Wang.

pages cmIncludes bibliographical references and index.ISBN 978-0-470-39098-6 (hardback)

1. Waterworks. 2. Drinking water. I. Wang, Lawrence K. II. Title. III. Title: Water and wastewaterengineering.

TD485.W36 2015363.6′1–dc23

2014041853

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

Contents

PREFACE XVII

ACKNOWLEDGMENTS XIX

1 Introduction to Water Systems 1

1.1 Components of Water Systems 21.2 Required Capacity 21.3 Sources of Water Supply 31.4 Rainwater 41.5 Surface Water 5

1.5.1 Continuous Draft 51.5.2 Selective Draft 51.5.3 Impoundage 5

1.6 Groundwater 61.6.1 Springs 81.6.2 Wells 81.6.3 Infiltration Galleries 81.6.4 Recharging Devices 9

1.7 Purification Works 91.8 Transmission Works 121.9 Distribution Works 12

1.9.1 High and Low Services 141.9.2 Fire Supplies 141.9.3 Pressures 151.9.4 Capacity 151.9.5 Service to Premises 15

1.10 Water Systems Management 151.10.1 Municipal Supplies 151.10.2 Individual Small Supplies 16

1.11 Individual Water Systems 17Problems/Questions 18References 19

2 Water Sources: Surface Water 21

2.1 Sources of Surface Water 212.2 Safe Yield of Streams 242.3 Storage as a Function of Draft and

Runoff 242.4 Design Storage 252.5 Loss by Evaporation, Seepage, and

Silting 272.5.1 Water-Surface Response 272.5.2 Seepage 292.5.3 Silting 29

2.6 Area and Volume of Reservoirs 312.7 Management of Catchment Areas 32

2.7.1 Upland Areas 322.7.2 Lowland Areas 322.7.3 Quality Control 322.7.4 Swamp Drainage 32

2.8 Reservoir Siting 332.9 Reservoir Management 33

2.9.1 Quality Control 342.9.2 Evaporation Control 34

2.10 Dams and Dikes 342.10.1 Embankment Dams 342.10.2 Masonry Dams 35

2.11 Spillways 362.12 Intakes 37

2.12.1 River Intakes 372.12.2 Lake and Reservoir Intakes 372.12.3 Submerged and Exposed

Intakes 382.12.4 Intake Velocities and Depths 382.12.5 Intake Conduits and Pumping

Stations 382.13 Diversion Works 382.14 Collection of Rainwater 39

Problems/Questions 41References 42

3 Water Sources: Groundwater 45

3.1 Porosity and Effective Porosity 453.2 Permeability 473.3 Groundwater Geology 473.4 Groundwater Situation in The United

States 483.5 Types of Aquifers 483.6 Groundwater Movement 493.7 Darcy’s Law 493.8 Aquifer Characteristics 503.9 Well Hydraulics 523.10 Nonsteady Radial Flow 52

3.10.1 Confined Aquifers 523.10.2 Semilogarithmic

Approximation 563.10.3 Recovery Method 583.10.4 Unconfined Aquifers 593.10.5 Leaky Aquifers 59

v

vi Contents

3.11 Prediction of Drawdown 603.11.1 Constant Discharge 603.11.2 Variable Discharge 613.11.3 Intermittent Discharge 61

3.12 Multiple-Well Systems 633.13 Aquifer Boundaries 67

3.13.1 Recharge Boundaries 673.13.2 Location of Aquifer

Boundaries 693.14 Characteristics of Wells 70

3.14.1 Specific Capacity of a Well 703.14.2 Partial Penetration 703.14.3 Effective Well Radius 703.14.4 Measurement of Well

Characteristics 713.15 Yield of a Well 71

3.15.1 Maximum AvailableDrawdown 71

3.15.2 Specific Capacity–DrawdownCurve 72

3.15.3 Maximum Yield 723.16 Well Design 733.17 Well Construction 74

3.17.1 Dug Wells 753.17.2 Driven and Jetted Wells 753.17.3 Bored Wells 753.17.4 Drilled Wells 753.17.5 Collector Wells 753.17.6 Pumps 753.17.7 Development 763.17.8 Testing 763.17.9 Sanitary Protection of Wells 763.17.10 Maintenance 76

3.18 Evaluation of Aquifer Behavior 773.18.1 Hydrologic Equation 773.18.2 Safe Yield of an Aquifer 773.18.3 Water Budget (Hydrologic

Budget) 773.19 Groundwater Quality Management 78

3.19.1 Biological Contamination 783.19.2 Subsurface Disposal of

Liquid Wastes 793.20 Groundwater Under the Direct Influence

of Surface Water 793.20.1 GWUDI Determination:

Source Screening Phase 793.20.2 GWUDI Determination:

Detailed Evaluation Phase 813.20.3 Hydrogeologic Assessment 813.20.4 Water Quality Assessment 823.20.5 Microscopic Particulate

Analyses 82Problems/Questions 84References 85

4 Quantities of Water Demand 87

4.1 Design Period 874.2 Design Population 88

4.2.1 Population Data 884.2.2 Population Growth 884.2.3 Short-Term Population Estimates 904.2.4 Long-Range Population Forecasts 914.2.5 Simplified Method for Population

Forecasts 924.2.6 Population Distribution and Area

Density 924.3 Water Consumption 92

4.3.1 Domestic Consumption 934.3.2 General Urban Water Demands 944.3.3 Industrial Water Consumption 954.3.4 Rural Water Consumption 96

4.4 Variations or Patterns of Water Demand 964.4.1 Domestic Variations 974.4.2 Fire Demands 98

4.5 Demand and Drainage Loads ofBuildings 104Problems/Questions 106References 106

5 Water Hydraulics, Transmission, andAppurtenances 109

5.1 Fluid Mechanics, Hydraulics, and WaterTransmission 1095.1.1 Fluid Mechanics and Hydraulics 1095.1.2 Transmission Systems 120

5.2 Fluid Transport 1215.2.1 Rational Equation for Surface

Resistance 1215.2.2 Exponential Equation for Surface

Resistance 1345.2.3 Form Resistance 1455.2.4 Hydraulic Transients 152

5.3 Capacity and Size of Conduits 1525.4 Multiple Lines 1545.5 Cross-Sections 1555.6 Structural Requirements 1555.7 Location 156

5.7.1 Line and Grade 1565.7.2 Vertical and Horizontal Curves 1575.7.3 Depth of Cover 157

5.8 Materials of Construction 1595.8.1 Carrying Capacity 1595.8.2 Strength 1595.8.3 Durability 1605.8.4 Transportation 1605.8.5 Safety 160

Contents vii

5.8.6 Maintenance 1605.8.7 Leakage 160

5.9 Appurtenances 1605.9.1 Gate Valves 1605.9.2 Blowoffs 1625.9.3 Air Valves 1625.9.4 Check Valves 1625.9.5 Pressure-Reducing Valves 1625.9.6 Pressure-Sustaining Valves 1635.9.7 Pressure Breaker Valves 1635.9.8 Flow Control Valves 1635.9.9 Throttle Control Valves 1635.9.10 Manholes 1635.9.11 Insulation Joints 1635.9.12 Expansion Joints 1635.9.13 Anchorages 1635.9.14 Other Appurtenances 163

5.10 Additional Hydraulics Topics 1645.10.1 Measurement of Fluid Flow

and Hydraulic Coefficients 1645.10.2 Forces Developed by Moving

Fluids 1665.10.3 Impulse–Momentum

Principles 1695.10.4 Drag and Lift Forces 171Problems/Questions 172References 178

6 Water Distribution Systems: Components,Design, and Operation 181

6.1 Distribution Systems 1816.1.1 One- and Two-Directional

Flow 1816.1.2 Distribution Patterns 1816.1.3 Pipe Grids 1816.1.4 High and Low Services 1816.1.5 Service to Premises 182

6.2 System Components 1836.3 System Capacity 1856.4 System Pressure 1856.5 Field Performance of Existing Systems 1866.6 Office Studies of Pipe Networks 187

6.6.1 Sectioning 1876.6.2 Relaxation (Hardy Cross) 1906.6.3 Pipe Equivalence 1946.6.4 Computer Programming 197

6.7 Industrial Water Systems 1976.8 Management, Operation, and

Maintenance of Distribution Systems 1976.8.1 General Maintenance Person

Asphyxiated While Attemptingto Repair Water Leak 198

6.8.2 Plumber Repairing a WaterLine Killed When Struck by aBackhoe Bucket 199

6.8.3 Welder Killed Following a100 ft (30 m) Fall from a WaterTower 201

6.9 Practical Design and Analysis of WaterDistribution Systems 2026.9.1 Minimum Design Period

Requirements 2026.9.2 Water Pressure Requirements 2026.9.3 Minimum Size Requirements 2026.9.4 Velocity Requirements 2036.9.5 Pipes and Valves Spacing

Requirements 2036.9.6 Hydrant Spacing, Location,

and Fire Flow Requirements 2036.9.7 Air Relief Valve Requirements 2036.9.8 Depth of Cover Requirements 2036.9.9 Separation of Water Mains

from Sources ofContamination 203

6.9.10 Head Loss of Water SystemFittings 204

Problems/Questions 205References 210

7 Water Distribution Systems: Modeling andComputer Applications 213

7.1 Watergems Software 2137.2 Water Demand Patterns 2137.3 Energy Losses and Gains 2147.4 Pipe Networks 215

7.4.1 Conservation of Mass 2157.4.2 Conservation of Energy 215

7.5 Network Analysis 2167.5.1 Steady-State Network

Hydraulics 2167.5.2 Extended-Period Simulation 216

7.6 Water Quality Modeling 2167.6.1 Age Modeling 2167.6.2 Trace Modeling 2177.6.3 Constituents Modeling 2177.6.4 Initial Conditions 2177.6.5 Numerical Methods 2177.6.6 Discrete Volume Method 2177.6.7 Time-Driven Method 218

7.7 Automated Optimization 2187.7.1 Model Calibration 2187.7.2 System Design 219

viii Contents

7.8 Practical Applications ofComputer-Aided Water Supply SystemAnalysis 232Problems/Questions 233References 240

8 Pumping, Storage, and Dual WaterSystems 241

8.1 Pumps and Pumping Stations 2418.2 Pump Characteristics 241

8.2.1 Power Requirements andEfficiencies of Pumps 244

8.2.2 Cavitation 2458.2.3 Performance Characteristics 246

8.3 Service Storage 2488.3.1 Equalizing, or Operating,

Storage 2488.3.2 Fire Reserve 2498.3.3 Emergency Reserve 2498.3.4 Total Storage 249

8.4 Location of Storage 2518.5 Elevation of Storage 2518.6 Types of Distributing Reservoirs 2518.7 Dual Water Supply Systems 257

8.7.1 Background 2588.7.2 The Nature of the Problems with

Drinking Water Quality 2588.7.3 The Pipes in the Distribution

Systems 2588.7.4 Biofilms and the Problems They

Cause 2598.7.5 The Proposed System 259

8.8 Raw Water Intake Structures and RawWater Pumping Wells 260Problems/Questions 262References 266

9 Cross-Connection Control 267

9.1 Introduction 2679.2 Public Health Significance of

Cross-Connections 2689.2.1 Human Blood in the Water

System 2689.2.2 Sodium Hydroxide in the Water

Main 2689.2.3 Heating System Antifreeze in

Potable Water 2689.2.4 Salt Water Pumped into

Freshwater Line 2699.2.5 Paraquat in the Water System 269

9.2.6 Propane Gas in the WaterMains 270

9.2.7 Chlordane and Heptachlor ata Housing Authority 271

9.2.8 Boiler Water Entered HighSchool Drinking Water 271

9.2.9 Car Wash Water in the StreetWater Main 272

9.2.10 Health Problems Due toCross-Connection in anOffice Building 275

9.3 Theory of Backflow andBacksiphonage 2769.3.1 Water Pressure 2769.3.2 Siphon Theory 2779.3.3 Backflow 280

9.4 Methods and Devices for thePrevention of Backflow andBacksiphonage 2809.4.1 Air Gap 2819.4.2 Barometric Loops 2819.4.3 Atmospheric Vacuum

Breakers 2819.4.4 Hose Bib Vacuum Breakers 2829.4.5 Pressure Vacuum Breakers 2839.4.6 Double Check Valves with an

Intermediate AtmosphericVent 283

9.4.7 Double Check Valves 2849.4.8 Double Check Detector

Check 2849.4.9 Residential Dual Check 285

9.5 Reduced Pressure Principle BackflowPreventer 285

9.6 Administration of a Cross-ConnectionControl Program 2899.6.1 Responsibility 2899.6.2 Dedicated Line 2909.6.3 Method of Action 290

9.7 Pressure and Leakage Tests of WaterMains 2919.7.1 Preparation for Pressure and

Leakage Tests 2919.7.2 Pressure and Leakage Tests 292Problems/Questions 293References 295

10 Water Quality Characteristics andDrinking Water Standards 297

10.1 Objectives of Water-QualityManagement 297

10.2 Natural Available Water Resources 297

Contents ix

10.3 Public Health Issues and DrinkingWater Treatment 298

10.4 Physical Characteristics andConstituents 30010.4.1 Color 30010.4.2 Turbidity and Particle

Count 30010.4.3 Taste and Odor 30110.4.4 Temperature 30110.4.5 Foamability 301

10.5 Chemical Characteristics andConstituents 30110.5.1 Metals 30210.5.2 Anions 30310.5.3 Alkalinity and pH 30410.5.4 Hardness, Calcium and

Magnesium, Carbonate andBicarbonate 304

10.5.5 Total Dissolved Solids andConductivity 305

10.5.6 Dissolved Oxygen 30510.5.7 Pesticides 30510.5.8 PCBs, CFCs, and Dioxin 30510.5.9 Asbestos 30610.5.10 Residual Disinfectants 30610.5.11 Disinfectant By-products 30610.5.12 Other Organic and

Inorganic Contaminants 30610.6 Biological Characteristics and

Constituents 30710.6.1 Bacteria 30710.6.2 Protozoa (Including

Cryptosporidium andGiardia lamblia) 307

10.6.3 Worms 30810.6.4 Viruses, Fungi, and Algae 30810.6.5 Coliform Indicator

Parameter 30810.6.6 Heterotrophic Plate Count

(HPC) 30910.6.7 Infections from

Water-Related Sources 31010.6.8 Reduction of Infections by

Water QualityManagement 310

10.7 Radiological Characteristics andConstituents 310

10.8 Drinking Water Quality Standards 31110.9 Industrial Water Quality Standards 31310.10 Bathing Waters 31710.11 Fishing and Shellfish Waters 31710.12 Irrigation Waters 31910.13 Quality of Water from Various

Sources 31910.14 Good Quality Water 32010.15 Self-Purification and Storage 320

10.16 Objectives of Water Examination 32110.17 Methods of Examination 32110.18 Standard Tests 32210.19 Expression of Analytical Results 32210.20 Tapping a Source of Water 322

Problems/Questions 323References 323

11 Water Treatment Systems 325

11.1 Purpose of Water Treatment 32511.2 Treatment of Raw Water 32511.3 Unit Operations and Unit Processes 32811.4 Gas Transfer 33011.5 Ion Transfer 330

11.5.1 Chemical Coagulation 33011.5.2 Chemical Precipitation 33111.5.3 Ion Exchange 33111.5.4 Adsorption 332

11.6 Solute Stabilization 33311.7 Solids Transfer 333

11.7.1 Straining 33311.7.2 Sedimentation 33311.7.3 Flotation 33411.7.4 Filtration 337

11.8 Nutrient or Molecular Transfer andInterfacial Contact 338

11.9 Disinfection 33911.10 Miscellaneous Operations/Processes 34011.11 Coordination of Unit

Operations/Processes 34011.12 Selection of Water Treatment

Technologies 34111.12.1 Treated Water

Requirements and InfluentCharacteristics 341

11.12.2 Existing SystemConfiguration 341

11.12.3 Water Treatment Costs 34111.12.4 Operation Requirements 34111.12.5 Pretreatment and

Posttreatment Processes 34111.12.6 Waste Management 34211.12.7 Future Service Area Needs 342

11.13 Control of Turbidity, Color, andBiological Contamination 342

11.14 Organic Contaminant Removal 34311.15 Inorganic Contaminant Removal and

Control 34511.15.1 Corrosion Controls 34511.15.2 Inorganic Contaminant

Removal 34511.15.3 Radionuclides Removal

and Risk Control 345

x Contents

11.16 Water Renovation 34811.17 Treatment Kinetics 35011.18 Monitoring Water Quality 35111.19 Distribution to Customers 35211.20 Glossary of Water Treatment

Systems 352Problems/Questions 359References 360

12 Chemicals Feeding, Mixing, andFlocculation 363

12.1 Introduction 36312.2 Handling, Storing, and Feeding

Chemicals 36312.2.1 Points of Chemical

Addition 36412.2.2 Chemical Metering

Equipment 36412.3 Rapid Mixing 367

12.3.1 Mechanical Mixers 36912.3.2 In-Line Static Mixers 37012.3.3 In-Line Mechanical

Blenders 37112.3.4 Jet Injection Blending 37112.3.5 Coagulant Diffusers 37212.3.6 Hydraulic Jumps 372

12.4 Rapid Mixing and Slow Flocculation 37212.5 Flocculation 37312.6 Mixing and Stirring Devices 373

12.6.1 Baffled Channels 37312.6.2 Pneumatic Mixing and

Stirring 37412.6.3 Mechanical Mixing and

Stirring 37412.7 Flocculator Performance 391

12.7.1 Mixing 39112.7.2 Flocculator Inlet and Outlet

Structures 39212.7.3 Improving Basin Circulation

with Baffles 39212.8 Costs 393

Problems/Questions 394References 395

13 Aeration, Gas Transfer, andOxidation 397

13.1 Sources of Gases in Water 39713.2 Objectives of Gas Transfer 39713.3 Absorption and Desorption of Gases 398

13.4 Rates of Gas Absorption andDesorption 400

13.5 Types of Aerators 40213.5.1 Gravity Aerators 40213.5.2 Spray Aerators 40213.5.3 Air Diffusers 40213.5.4 Mechanical Aerators 404

13.6 Factors Governing Gas Transfer 40513.7 Design of Gravity Aerators 40513.8 Design of Fixed-Spray Aerators 40613.9 Design of Movable-Spray Aerators 40613.10 Design of Injection Aerators 40713.11 Mechanical Aerators 40813.12 Oxidation for Removal of Dissolved

Iron and Manganese 40813.12.1 Solubility of Fe and Mn 40813.12.2 Redox Reactions of Fe and

Mn 40913.12.3 Precipitation of Fe and Mn 40913.12.4 Kinetics of Oxygenation 40913.12.5 Engineering Management

of Oxidative Removal ofIron and Manganese 409

13.13 Removal of Specific Gases 41113.13.1 Methane 41113.13.2 Carbon Dioxide 41113.13.3 Hydrogen Sulfide 411

13.14 Removal of Odors and Tastes 414Problems/Questions 414References 415

14 Coagulation 417

14.1 Introduction 41714.2 The Colloidal State 417

14.2.1 Electrokinetic Properties ofColloids 417

14.2.2 Hydration 41814.2.3 Tyndall Effect 41814.2.4 Brownian Movement 41814.2.5 Filterability 418

14.3 Colloidal Structure and Stability ofColloids 418

14.4 Destabilization of Colloids 42114.4.1 Double-Layer

Compression 42114.4.2 Adsorption and Charge

Neutralization 42214.4.3 Entrapment of Particles in

Precipitate 42214.4.4 Adsorption and Bridging

between Particles 422

Contents xi

14.5 Influencing Factors 42314.5.1 Colloid Concentration 42314.5.2 Alkalinity and pH 42314.5.3 Coagulant Dosage and pH 42314.5.4 Zeta Potential 42414.5.5 Affinity of Colloids for Water 42414.5.6 Anions in Solution 42514.5.7 Cations in Solution 42514.5.8 Temperature 425

14.6 Coagulants 42514.6.1 Aluminum Salts 42614.6.2 Iron Salts 42714.6.3 Sodium Aluminate 43014.6.4 Magnesium Coagulant 43014.6.5 Polymeric Inorganic Salts 43014.6.6 Organic Polymers 43114.6.7 Coagulant Aids 432

14.7 Coagulation Control 43214.7.1 Jar Test 43314.7.2 Zetameter 43314.7.3 Streaming Current Detector 43414.7.4 Colloid Titration for

Polyelectrolyte Determinationand Coagulation Control 434

Problems/Questions 435Special Reference 436References 436

15 Screening, Sedimentation, andFlotation 439

15.1 Treatment Objectives 43915.2 Screening 43915.3 Sedimentation 43915.4 Types of Sedimentation 439

15.4.1 Settling Velocities of DiscreteParticles—Class 1Clarification 440

15.4.2 Hindered Settling of DiscreteParticles—Class 2Clarification 443

15.4.3 Settling of FlocculentSuspensions—Zone Settling 445

15.4.4 Compression Settling 44615.5 Settling Basins 447

15.5.1 Efficiency of Ideal SettlingBasins 447

15.5.2 Reduction in SettlingEfficiency by Currents 448

15.5.3 Short-Circuiting and BasinStability 449

15.5.4 Scour of Bottom Deposits 45015.5.5 Elements of Tank Design 451

15.6 Upflow Clarification 45115.7 General Dimensions of Settling

Tanks 45515.8 Sludge Removal 45615.9 Inlet Hydraulics 45615.10 Outlet Hydraulics 45915.11 Sedimentation Tank Loading,

Detention, And Performance 45915.11.1 Sedimentation Tank

Performance 45915.11.2 Regulations and Standards 460

15.12 Shallow Depth Settlers 46215.12.1 Theory of Shallow Depth

Settling 46215.12.2 Tube Settlers 46315.12.3 Lamella Separator 464

15.13 Gravity Thickening of Sludge 46415.14 Natural Flotation 46715.15 Dissolved Air Flotation Process 468

15.15.1 Process Description 46815.15.2 Process Configurations 46815.15.3 Factors Affecting

Dissolved Air Flotation 46915.15.4 Dissolved Air Flotation

Theory 46915.15.5 Flotation Design,

Operation, andPerformance 474

15.15.6 Municipal Potable WaterPlants 475

Problems/Questions 480References 482

16 Conventional Filtration 485

16.1 Granular Water Filters 48516.2 Granular Wastewater Filters 48716.3 Granular Filtering Materials 488

16.3.1 Grain Size and SizeDistribution 488

16.3.2 Grain Shape and ShapeVariation 489

16.4 Preparation of Filter Sand 49016.5 Hydraulics of Filtration 491

16.5.1 Hydraulics of StratifiedBeds 492

16.5.2 Hydraulics of UnstratifiedBeds 493

16.6 Hydraulics of Fluidized Beds—FilterBackwashing 494

16.7 Removal of Impurities 49716.8 Kinetics of Filtration 497

xii Contents

16.9 Filter Design 49816.9.1 Bed Depth 49816.9.2 Underdrainage Systems 50016.9.3 Scour Intensification 50316.9.4 Washwater Troughs 50316.9.5 Filter and Conduit

Dimensions 50516.10 Filter Appurtenances and Rate

Control 50516.11 Length of Filter Run 50616.12 Filter Troubles 50716.13 Plant Performance 508

16.13.1 Bacterial Efficiency 50816.13.2 Removal of Color,

Turbidity, and Iron 50916.13.3 Removal of Large

Organisms 50916.13.4 Oxidation of Organic

Matter 509Problems/Questions 509References 510

17 Alternative and MembraneFiltration Technologies 513

17.1 Introduction of FiltrationTechnologies 51317.1.1 Filtration Overview 51317.1.2 Filtration Applications 513

17.2 Direct Filtration 51417.2.1 Process Description 51417.2.2 System Performance 516

17.3 Slow Sand Filtration 51617.3.1 Process Description 51617.3.2 System Performance 51617.3.3 System Design

Considerations 51717.3.4 Operation and

Maintenance 51817.4 Package Plant Filtration 518

17.4.1 General ProcessDescription 518

17.4.2 Conventional FiltrationPackage Plants 519

17.4.3 Tube-Type ClarifierPackage Plants 519

17.4.4 Adsorption Clarifier-FilterPackage Plant 519

17.4.5 Dissolved AirFlotation-FiltrationPackage Plant 520

17.4.6 Operation and Maintenanceof Package Plants 522

17.4.7 General System Performanceof Package Plants 522

17.5 Diatomaceous Earth Filtration 52417.5.1 Process Description 52417.5.2 Operation and Maintenance 525

17.6 Cartridge Filtration 52617.6.1 Cartridge Filtration

Applications 52617.6.2 Operation and Maintenance

of Cartridge Filtration 52617.7 Membrane Filtration 527

17.7.1 Process Description 52717.7.2 System Design

Considerations 52717.7.3 Operation of Membrane

Filtration 53117.7.4 Maintenance of Membrane

Filtration Systems 53717.7.5 Membrane Filtration

Applications 53817.7.6 System Performance of

Membrane Filtration 53917.7.7 Potential Problems of

Membrane Filtration 54017.8 Selecting the Appropriate Filtration

Treatment System 54017.8.1 Steps in an Evaluation 54017.8.2 Need for Pilot Studies 54017.8.3 Flocculation, Sedimentation,

and Flotation Studies 54117.8.4 Filtration Studies 541Problems/Questions 541References 542

18 Disinfection and Disinfection By-productsControl 545

18.1 Purpose of Disinfection 54518.2 Pathogens, Disinfection, and

Disinfectants 54518.3 Disinfection by Heat 54618.4 Disinfection by Ultraviolet Light 54618.5 Disinfection by Chemicals 546

18.5.1 Oxidizing Chemicals 54618.5.2 Metal Ions 54718.5.3 Alkalis and Acids 54718.5.4 Surface-Active Chemicals 54718.5.5 Advanced Oxidation

Processes 54718.6 Theory of Chemical Disinfection 54818.7 Kinetics of Chemical Disinfection 549

18.7.1 Time of Contact 54918.7.2 Concentration of

Disinfectant 551

Contents xiii

18.7.3 Temperature ofDisinfection 551

18.7.4 Ct Values for DisinfectionProcess Control 552

18.8 Disinfection by Ozone 55418.9 Disinfection by Chlorine 55618.10 Free Available Chlorine and Free

Chlorination 55618.11 Combined Available Chlorine and

Chloramination 55818.12 Breakpoint Reactions of Ammonia 55918.13 Dechlorination 55918.14 Disinfection by-Products 560

18.14.1 Formation of DisinfectionBy-products 560

18.14.2 Strategies for ControllingDisinfection By-products 560

18.15 Chemical Technology ofDisinfection 562

18.16 Operational Technology ofChlorination 56218.16.1 Water Chlorination

Applications 56418.16.2 Additional Chlorination

Applications 56618.16.3 Manageable Variables in

Halogenation 56618.17 Operational Technology of Sodium

Hypochlorination 56718.17.1 Equipment Costs 56718.17.2 Operating and Maintenance

Costs 56718.17.3 Chemical Costs 568

18.18 Operational Technology of CalciumHypochlorination 570

18.19 Operational Technology of ChlorineDioxide Disinfection 570

18.20 Operational Technology ofOzonation 57118.20.1 Process Description 57218.20.2 System Design

Considerations 57318.21 Operational Technology of UV

Disinfection 57418.21.1 UV Disinfection System

Design Considerations 57418.21.2 UV Lamp Designs 57518.21.3 Factors Affecting the

Design of the UVDisinfection System 576

18.21.4 UV Transmittance 57718.21.5 UV Equipment

Configuration 57718.21.6 UV Lamp Age and Quartz

Sleeve Fouling 577

18.21.7 UV System Operating andMaintenanceConsiderations 577

18.21.8 Operation and Maintenanceof UV Lamps 578

18.21.9 Operation and Maintenanceof the Reactor 578

18.22 Recent Developments in DisinfectionManagement—Log Removal/Inactivation Credits of DrinkingWater Treatment Processes 58218.22.1 Introduction 58218.22.2 Surface Water Treatment

Rule and Long Term 2Enhanced Surface WaterTreatment Rule 582

18.22.3 Ground Water Rule andTotal Coliform Rule 588

Problems/Questons 589References 591

19 Chemical Precipitation and WaterSoftening 593

19.1 Chemical Precipitation 59319.2 Description of Precipitation Process 593

19.2.1 Metals Removal 59319.2.2 Removal of Fats, Oils, and

Greases 59419.2.3 Phosphorus Removal 59419.2.4 Removal of Suspended

Solids 59519.2.5 Additional Considerations 595

19.3 Applicability 59619.4 Advantages and Disadvantages 59619.5 Design Criteria 59619.6 Performance—Jar Testing 59719.7 Operation and Maintenance 59719.8 Costs 59819.9 Precipitation of Hardness and

Carbonates—Water Softening 59819.10 Recarbonation After Water Softening 60219.11 Recovering Lime After Water

Softening 602Problems/Questions 603References 603

20 Adsorption and Ion Exchange 605

20.1 Adsorption Processes 60520.2 Adsorption Kinetics and Equilibria 605

20.2.1 Adsorption Kinetics 605

xiv Contents

20.2.2 Conditions of Equilibrium 60620.2.3 Interpretation of Adsorption

Isotherms 60820.3 Characteristics of Adsorbents 608

20.3.1 Silica Gel 60820.3.2 Activated Carbon 60820.3.3 Polymeric Adsorbents 60920.3.4 Carbon Properties Relating

to Adsorption 60920.4 Adsorption of Odors and Tastes 61020.5 Pilot Carbon Column Tests 61220.6 Breakthrough Curve 61320.7 Process Technology 614

20.7.1 Types of Contact Beds 61420.7.2 Design Criteria of Carbon

Beds 61520.7.3 Design of an Adsorption

Bed 61720.7.4 Carbon Regeneration

Systems 62220.8 Ion Exchange 624

20.8.1 Advantages andDisadvantages of IonExchange 624

20.8.2 System Performance 62520.9 Ion Exchangers 626

20.9.1 Synthetic Ion Exchangers 62620.9.2 Activated Alumina and

Zeolite 62620.10 The Ion Exchange Process 62820.11 Ion Selectivity 63020.12 Kinetics of Ion Exchange 63120.13 Ion Exchange Technology 63220.14 Water Softening by Ion Exchange 63320.15 Demineralization 63420.16 Concentration of Ions 63520.17 Ion Exchange Membranes and

Dialysis 63520.18 Modular Treatment Units for

Removal of Radionuclides 63620.19 Case Study I: Nitrate Removal:

McFarland, CA 63620.20 Case Study II: Fluoride Removal in

Gila Bend, AZ 637Problems/Questions 637References 639

21 Chemical Stabilization and Control ofCorrosion and Biofilms 641

21.1 Chemical Stabilization 64121.2 Corrosion 643

21.3 The Corrosion Reaction 64421.3.1 Factors Affecting Corrosion 64621.3.2 Corrosion Indices 64621.3.3 Consumer Complaints 64721.3.4 Scale or Pipe Surface

Examination 64721.3.5 Measurement of Corrosion

Rate 64721.4 Control of Corrosion 64821.5 Lead and Copper Corrosion 650

21.5.1 Health Effects 65021.5.2 Occurrence as a Corrosion

By-product 65021.5.3 Diagnosing and Evaluating

the Problem 65121.5.4 Sampling and Chemical

Analysis 65121.6 Lead Corrosion Control 651

21.6.1 Distribution and PlumbingSystem DesignConsiderations 652

21.6.2 Water Quality Modifications 65221.6.3 Corrosion Inhibitors 65421.6.4 Cathodic Protection 65521.6.5 Coatings and Linings 655

21.7 Biofilm Control 65521.7.1 Factors That Favor Biofilm

Growth 65721.7.2 Biofilm Control Strategies 657Problems/Questions 659References 660

22 Residues Management, Safety, andEmergency Response 661

22.1 Management of Residues 66122.2 Types of Residuals 66222.3 Applicable Regulations 66322.4 Residual Solids Treatment 66322.5 Residuals Disposal 664

22.5.1 Underground Injection 66422.5.2 Direct Discharge to Surface

Waters 66422.5.3 Discharge to Sewers and

WWTP 66422.5.4 Landfilling 66522.5.5 Land Application 665

22.6 Selection of Management Plans 66622.7 Safety and Accident Prevention 670

22.7.1 Safety in Valve Vault Design 67022.7.2 Safety in Chemical Handling 67122.7.3 Safety in the Placement of

Valves 671

Contents xv

22.7.4 Safety in Water SystemPerimeter Fall Protection 672

22.8 Emergency Response Plan 67322.9 Actions Prior to Developing an ERP 67422.10 Emergency Response Plan Core

Elements 67522.10.1 System-Specific

Information 67522.10.2 CWS Roles and

Responsibilities 67522.10.3 Communication

Procedures (Who, What,and When) 675

22.10.4 Personnel Safety 67622.10.5 Identification of Alternate

Water Sources 67622.10.6 Replacement Equipment

and Chemical Supplies 67722.10.7 Property Protection 67722.10.8 Water Sampling and

Monitoring 67722.11 Putting the ERP Together and ERP

Activation 67722.12 Action Plans 67822.13 Next Steps 681

Problems/Questions 681References 682

23 Prevention through Design and SystemSafety 683

23.1 Introduction to System Safety 68323.2 Nature and Magnitude of Safety and

Health Problems 68523.3 Risk Assessment Matrix 687

23.3.1 Description 68723.3.2 Procedures 68823.3.3 Advantages and

Limitations of the RiskMatrix 693

23.4 Failure Modes, Effects, andCriticality Analysis 69323.4.1 Description 69323.4.2 Application 69323.4.3 Procedures 69323.4.4 Advantages and

Limitations 69823.5 Engineering and Design for Safe

Construction 69823.5.1 Construction Failures 69823.5.2 Causes of Construction

Failures 699

23.5.3 Classification of CausalFactors 699

23.6 Construction Safety and HealthManagement 70323.6.1 Safety and Health Program

Elements 70323.6.2 Project Safety Rules 70423.6.3 Training and Worker

Orientation 70423.6.4 New Worker Orientation 70423.6.5 Accident Investigation and

Recordkeeping 70623.6.6 Safety Budget and Audits 706

23.7 Requirements for Safety inConstruction Projects 70623.7.1 Falls 70623.7.2 Excavation and Trenching 70723.7.3 Confined Space Entry 70823.7.4 Heavy Construction

Equipment 70923.8 Occupational Diseases 710

23.8.1 System Approach 71023.8.2 Complexity of the Issues 71123.8.3 Scientific Factors 71123.8.4 Occupational Disease as a

Process 71223.8.5 Potential Hazards 71223.8.6 Modes of Entry 71223.8.7 Body Processes and

Defenses 71323.8.8 Elimination 714

23.9 Ergonomics 71423.9.1 The Worker and Work 71423.9.2 Adverse Effects Caused by

Workplace Conditions 715Problems/Questions 715References 716

24 Engineering Projects Management 717

24.1 Role of Engineers 71724.2 Steps in Project Development 717

24.2.1 Community Action 71724.2.2 Engineering Response 718

24.3 The Engineering Report 71824.4 Feasibility Studies 71924.5 Alternatives 71924.6 Plans and Specifications 72024.7 Sources of Information 72024.8 Standards 72024.9 Design Specifications 72124.10 Project Construction 721

24.10.1 Notice to Bidders 721

xvi Contents

24.10.2 General Conditions 72124.10.3 Special Provisions 72224.10.4 Detailed Specifications 72224.10.5 The Proposal 72224.10.6 The Contract 722

24.11 Project Financing 72324.12 Methods of Borrowing 725

24.12.1 General Obligation Bonds 72524.12.2 Revenue Bonds 72524.12.3 Special Assessment Bonds 725

24.13 Rate Making 725

24.13.1 Water Rates 72524.13.2 Fire Protection 72624.13.3 Peak-Flow Demands 72624.13.4 Sewer Service Charges 726

24.14 Systems Management 726Problems/Questions 727References 727

APPENDIXES 729

INDEX 797

Preface

History of this Book Series: Water andWastewater Engineering

This book, Water Engineering, is the second textbook in theWater and Wastewater Engineering series, which is a revisionof the classic text, originally authored by Professors GordonM. Fair (Harvard University), John C. Geyer (John HopkinsUniversity), and Daniel A. Okun (University of North Car-olina). Professors Daniel A. Okun and Marvin L. Granstorm(Rutger University) were the driving forces of this new globaledition that includes both US and SI design equations andexamples. The current authors, Professors Nazih K. Sham-mas and Lawrence K. Wang were the students of ProfessorOkun, and Professor Granstorm, respectively. Just beforebeginning the preparation of this new edition of Water andWastewater Engineering, the last surviving member of theoriginal authors, Professor Daniel A. Okun, died on Decem-ber 10, 2007. In the normal course of events Professor Okunwould have been with the current authors in preparing thisbook series. This new book series is dedicated to the memoryof Professors Fair, Geyer, Okun, and Granstrom.

Goals of this Book: Water Engineering

Today, effective design and efficient operation of water engi-neering works ask, above all, for a fuller understanding andapplication of scientific principles. Thus, the results of scien-tific research are being incorporated with remarkable successin new designs and new operating procedures. Like otherfields of engineering, water engineering has its science andits art. To reach the audience to which this book is addressed,the science of water engineering is given principal empha-sis. However, the art of water engineering is not neglected.Enough elements of water engineering practice, experience,common sense, and rules of thumb are included to keep thereader aware of the water environment and constructions thatplace water at the service of cities and towns, and of villagesand homesteads.

Further Study in Addition to Classroom Education

The study of scientific principles is best accomplished in theclassroom; the application of these principles follows as amatter of practice. To further bridge the way from princi-ple to practice, we suggest that the study of these textbooksbe supplemented by (1) visits to water works, (2) examina-tion of plans and specifications of existing water systems,(3) readings in the environmental science and engineeringperiodicals, (4) study of the data and handbook editions of

trade journals, (5) examination of the catalogs and bulletinsof equipment manufacturers, and (6) searching for the latestwater engineering developments from the Internet.

Intended Audience

Like its forerunners, this new book, Water Engineering, isintended for students of civil and environmental engineering,no matter whether they belong to the student body of a uni-versity or are already established in their profession. Specif-ically, the target audience is engineering students who havehad introductory calculus, chemistry and fluid mechanics,typically civil, environmental and water resources engineer-ing majors. Several chapters of the book contain introduc-tory material appropriate for juniors as well as more advancedmaterial that might only be appropriate for upper-level under-graduate engineering students. Specifically, applied hydrol-ogy, hydraulics, and pertinent physical, chemical, and bio-logical properties of water are reviewed. The inclusion ofthis material makes this book important also to physical andinvestment planners of urban and regional developments.In this sense, too, this book and other books in the newseries should be of interest to chemical engineers, geologists,chemists, and biologists who are collaborators of the waterenvironment.

Course Suggestions

The book is comprehensive and covers all aspects of waterincluding its quality, sources, supply, drinking water stan-dards, treatment, transmission, storage, and distribution.This comprehensive coverage gives faculty the flexibilityof choosing the material as they find fit for their courses,and this wide coverage is helpful to water engineers in theireveryday practice.

Courses where this book may be used include

1. Water engineering

2. Water supply, transmission and distribution system

3. Water treatment

4. Design of water treatment plants

5. Design of water distribution networks

6. Civil and sanitary engineering design

7. Environmental engineering design

8. Hydraulics

9. Water resources engineering

xvii

xviii Preface

Key Features of This Book

Several items unique to this textbook include

1. Solved problems. A reliable problem-solving expe-rience for students is carried out throughout the textand demonstrated in every example problem to rein-force best practices.

2. Photos and illustrations. Photos and illustrationsare used throughout the text to clarify water engi-neering infrastructure systems and show examplesof built and constructed water supply, transmission,treatment, storage and distribution facilities.

3. Current water treatment and infrastructureissues. Current infrastructure and global issues areaddressed in the text. Examples of such issuesinclude (a) established water treatment technologies;(b) conventional and new pathogenic microorgan-isms and impurities; (c) Cryptosporidium, volatileorganic compounds, heavy metals, and disinfectionby-products control; (d) flotation, membrane filtra-tion, and UV; (e) groundwater under the direct influ-ence of surface water; (f) dual water systems; (g)cross-connections control and backflow prevention;(h) design nomograms for fast water infrastructureanalysis; (i) computer-aided water distribution sys-tem modeling and analysis; (j) water safety and emer-gency response.

4. Engineering equations and example problemswith both US and SI Units for training engineers towork globally. The text has a multitude of examplesand problems. Such problems incorporate both SI andthe more customary US unit systems. We feel thatmost other texts fall short in both these areas by notproviding students with examples that help explaindifficult technical concepts and by only focusing onone system of units.

5. Applied hydraulics. Hydraulics concepts are criticalfor the civil, environmental and water resources engi-neering professionals, and thus the readers. Appliedhydraulics topics such as pumps, weirs, pressurizedpipe flow, gravity flow, head losses are reviewedin this book for practical design of water-handlingfacilities.

6. Prevention through design, residuals manage-ment, and water system safety. Chapter 23 is ded-icated to prevention through design (PtD), as it isimportant for readers to learn about this new strat-egy. NIOSH is promoting the inclusion of PtD in

undergraduate engineering education, has reviewedthis chapter and provided the illustrative case studiesdescribed in Chapter 6, Water Distribution Systems:Components, Design, and Operation, and Chapter22, Residues Management, Safety, and EmergencyResponse. Other water engineering texts do notaddress these important topics.

Instructor Resources

The following resources are available to instructors on thebook website at:

1. Solutions manual. Complete solutions for everyhomework problem and answers to all discussionquestions in the text will be available to instructors.

2. Image gallery. Images from the text in electronicformat, for preparation of lecture PowerPoint slides.

3. Access to student resources. Instructors will alsohave access to all the student resources.

The instructor resources are password protected, and willbe made available to instructors who have adopted the textfor their course. Visit the instructor section of the website toregister for a password.

Student Resources

The following resources are available to students on the bookwebsite at:

1. Data sets. Data sets for all examples and homeworkexercises in the text will be provided, so that studentsmay perform what-if scenarios, and to avoid errorsdue to data entry during problem solving.

2. Access to design software. Included with the text, sostudents may download the software from an onlinesource.

Software

Included with this text is access to the software HaestadMethods Water Solutions by Bentley. Software exhibited inthe text, include WaterGEMS that is used to illustrate theapplication of various available software programs in helpingcivil and environmental engineers design and analyze waterdistribution systems. It is also used by water utility managersas a tool for the efficient operation of distribution systems.See Chapter 7, Water Distribution Systems: Modeling andComputer Applications.

Acknowledgments

Books do not come off the press through the efforts ofauthors alone. Their preparation passes successively througheditorial and production stages. The authors would liketo thank our colleagues, mentors, Wiley editors/reviewersMichael Leventhal and Bob Esposito, and the resourceproviders and designers who have guided our efforts alongthese ways.

Sincere appreciations are extended to the families of Pro-fessors Fair, Geyer, Okun, and Granstrom, and the review-ers whose suggestions and comments have significantlyimproved the overall quality of this book series.

We also thank Dr. Richard Rinehart, Prevention throughDesign National Initiative at NIOSH, who reviewed PtD(Chapter 23), and Dr. Carolyn M. Jones (SFPUC Health andSafety Program Manager at NIOSH), who provided the casestudies included in Chapters 6 and 22.

A book is not written in long evenings and on holidayswithout the consent, encouragement, and cooperation of thewriters’ families. This, too, should be a matter of record.

Nazih K. ShammasAmerican University of Beirut, Lebanon (BE)University of North Carolina at Chapel Hill, NC, USA

(MSSE)University of Michigan, Ann Arbor, MI, USA (PhD)

Lawrence K. WangNational Cheng Kung University, Tainan, Taiwan, ROC

(BSCE)Missouri University of Science and Technology, Rolla, MO,

USA (MSCE)University of Rhode Island, Kingston, RI, USA (MS)Rutgers University, New Brunswick, NJ, USA (PhD)

xix

Chapter 1

Introduction to Water Systems

The right to water is an implicit part of the right to an ade-quate standard of living and the right to the highest attainablestandard of physical and mental health, both of which areprotected by the United Nations’ International Covenant onEconomic, Social and Cultural Rights, which was establishedin 1976. However, some countries continue to deny the legit-imacy of this right. In light of this fact and because of thewidespread noncompliance of states with their obligationsregarding the right to water, the United Nations’ Committeeon Economic, Social and Cultural Rights confirmed and fur-ther defined the right to water in its General Comment No.15 in 2002. The comment clearly states that the right to wateremanates from and is indispensable for an adequate standardof living as it is one of the most fundamental conditions forsurvival:

The human right to water entitles everyone tosufficient, safe, acceptable, physically accessibleand affordable water for personal and domesticuses. An adequate amount of safe water is neces-sary to prevent death from dehydration, reducethe risk of water-related disease and provide forconsumption, cooking, personal and domestichygienic requirements.

According to the World Health Organization (WHO),1.1 billion people (17% of the global population) lack accessto safe drinking water, meaning that they have to revert tounprotected wells or springs, canals, lakes, or rivers to fetchwater; 2.6 billion people lack adequate sanitation; and 1.8million people die every year from diarrheal diseases, includ-ing 90% of children under age 5. This situation is no longerbearable. To meet the WHO’s Water for Life Decade (2005–2015), an additional 260,000 people per day need to gainaccess to improved water sources.

In 2004 about 3.5 billion people worldwide (54% of theglobal population) had access to piped water supply throughhouse connections. Another 1.3 billion (20%) had accessto safe water through other means than house connections,including standpipes, “water kiosks,” protected springs, andprotected wells.

In the United States 95% of the population that is servedby community water systems receives drinking water thatmeets all applicable health-based drinking water standardsthrough effective treatment and source water protection. In2007, approximately 156,000 US public drinking water sys-tems served more than 306 million people. Each of these sys-tems regularly supplied drinking water to at least 25 peopleor 15 service connections. Beyond their common purpose,the 156,000 systems vary widely. Table 1.1 groups watersystems into categories that show their similarities and dif-ferences. For example, the table shows that most people in theUnited States (286 million) get their water from a commu-nity water system. Of the approximately 52,000 communitywater systems, just 8% of those systems (4048) serve 82%of the people.

Water is used in population centers for many purposes:(a) for drinking and culinary uses; (b) for washing, bathing,and laundering; (c) for cleaning windows, walls, and floors;(d) for heating and air conditioning; (e) for watering lawnsand gardens; (f) for sprinkling and cleaning streets; (g) forfilling swimming and wading pools; (h) for display in foun-tains and cascades; (i) for producing hydraulic and steampower; (j) for employment in numerous and varied industrialprocesses; (k) for protecting life and property against fire; and(l) for removing offensive and potentially dangerous wastesfrom households, commercial establishments, and industries.To provide for these varying uses, which total about 100 gal-lons per capita per day (gpcd) or 378 liters per capita perday (Lpcd) in average North American residential commu-nities and 150 gpcd (568 Lpcd) or more in large industrialcities, the supply of water must be satisfactory in quality andadequate in quantity, readily available to the user, relativelycheap, and easily disposed of after it has served its manypurposes. Necessary engineering works are waterworks, orwater supply systems, and wastewater works, or wastewatermanagement systems.

Waterworks withdraw water from natural sources ofsupply, purify it if necessary, and deliver it to the con-sumer. Wastewater works collect the spent water of thecommunity—about 70% of the water supplied—togetherwith varying amounts of entering ground and surface waters.

Water Engineering: Hydraulics, Distribution and Treatment, First Edition. Nazih K. Shammas and Lawrence K. Wang.© 2016 John Wiley & Sons, Inc. Published 2016 by John Wiley & Sons, Inc.

1

2 Chapter 1 Introduction to Water Systems

Table 1.1 US public water systems size by population served in 2007

Very small Small Medium Large Very largeWater system (500 or less) (501–3,300) (3,301–10,000) (10,001–100,000) (>100,000) Total

Communitywater systema

No. of systems 29,282 13,906 4,822 3,702 398 52,110Population

served4,857,007 19,848,329 27,942,486 105,195,727 128,607,655 286,451,204

Percentage ofsystems

56 27 9 7 1 100

Percentage ofpopulation

2 7 10 37 45 100

Nontransientnoncommunitywater systemb

No. of systems 16,034 2,662 120 22 1 18,839Population

served2,247,556 2,710,330 639,561 533,845 203,000 6,334,292

Percentage ofsystems

85 14 1 0 0 100

Percentage ofpopulation

35 43 10 8 3 100

Transientnoncommunitywater systemc

No. of systems 81,873 2,751 102 15 3 84,744Population

served7,230,344 2,681,373 546,481 424,662 2,869,000 13,751,860

Percentage ofsystems

97 3 0 0 0 100

Percentage ofpopulation

53 19 4 3 21 100

Total no. of systems 127,189 19,319 5,044 3,739 402 155,693

Source: Courtesy US Environmental Protection Agency.aCommunity water system: a public water system that supplies water to the same population year-round.bNontransient noncommunity water system: a public water system that regularly supplies water to at least 25 of the same people at least 6 months per year,but not year-round. Some examples are schools, factories, office buildings, and hospitals that have their own water systems.cTransient noncommunity water system: a public water system that provides water in a place such as a gas station or campground where people do notremain for long periods of time.

The collected wastewaters are treated and reused or dis-charged, usually into a natural water body, more rarely ontoland. Often the receiving body of water continues to servealso as a source of important water supplies for many pur-poses. It is this multiple use of natural waters that creates themost impelling reasons for sound water quality management.

1.1 COMPONENTS OF WATER SYSTEMS

Each section of this chapter offers, in a sense, a preview ofmatters discussed at length in later parts of this book. Therethey are dealt with as isolated topics to be mastered in detail.Here they appear in sequence as parts of the whole so thattheir general purpose and significance in the scheme of thingsmay be understood and may give reason for closer study.

Municipal water systems generally comprise (a)collection works, (b) purification works, (c) transmissionworks, and (d) distribution works. The relative functions andpositions of these components in a surface water supply aresketched in Fig. 1.1. Collection works either tap a sourcecontinuously adequate in volume for present and reasonablefuture demands or convert an intermittently insufficientsource into a continuously adequate supply. To ensure

adequacy, seasonal and, in large developments, even annualsurpluses must be stored for use in times of insufficiency.When the quality of the water collected is not satisfactory,purification works are introduced to render it suitable forthe purposes it must serve: contaminated water is disin-fected; aesthetically displeasing water made attractive andpalatable; water containing iron or manganese deferrized ordemanganized; corrosive water deactivated; and hard watersoftened. Transmission works convey the collected andpurified supply to the community, where distribution worksdispense it to consumers in wanted volume at adequatepressure. Ordinarily, the water delivered is metered so thatan equitable charge can be made for its use and, often, alsofor its disposal after use.

1.2 REQUIRED CAPACITY

Water supply systems are designed to meet population needsfor a reasonable number of years in the future. The rate ofconsumption is normally expressed as the mean annual usein gpcd or Lpcd, and seasonal, monthly, daily, and hourlydepartures in rate are given in percentages of the mean. InNorth America the spread in consumption is large: from

1.3 Sources of Water Supply 3

Divide

Yield

Reservoir

Filters

Reservoir and dam

Collection system

Water shed, catchmentarea, or drainage area

100 mi2

Purification works

Distribution system

Distributionsystem

Pipeline

Pipeline Servicereservoir

Municipality

Area = 1 mi2

Rainfall = 40 in./yrEvaporation = 20 in./yrStream flow or runoff = 20 in./yr = 348 MG/yr/mi2

= 952,000 gpd/mi2

Water surface = 4.3 mi2

Average depth = 15 ftStorage = 13.5 billion gal = 180 days of draft

Population = 500,000Consumption = 150 gpcd = 75 MGD = 750,000 gpd/mi2

= 79% of mean annual rainfall

Figure 1.1 Rainfall, runoff, storage,and draft relations in thedevelopment of surface water(conversion factors:1 mi2 = 2.59 km2;1 in.∕yr = 25.4 mm∕yr;1 ft = 0.3048 m;1 MG∕yr∕mi2 = 1.46 ML∕yr∕km2;1 gpd∕mi2 = 1.461 L∕d∕km2;1 billion gal = 1 BG =3.785 billion L = 3.785 BL;1 gpcd = 3.785 Lpcd;1 MGD = 3.785 MLD).

35 to 500 gpcd (132–1890 Lpcd), varying radically withindustrial water demands. Average rates between 100 and200 gpcd (378–757 Lpcd) are common, and a generalizedaverage of 150 gpcd (568 Lpcd) is a useful guide to normalrequirements.

The capacity of individual system components is set bywhat is expected of them. Distribution systems, for example,must be large enough to combat and control serious con-flagrations without failing to supply maximum coincidentdomestic and industrial drafts. Fire demands vary with sizeand value of properties to be protected and are normally afunction of the gross size of the community. The distribu-tion system leading to the high-value district of an averageAmerican city of 100,000 people, for example, must have anexcess of fire standby capacity equal in itself to the averagerate of draft. For smaller or larger American communities,the standby capacity falls or rises, within certain limits, moreor less in proportion to the square root of the population.

1.3 SOURCES OF WATER SUPPLY

The source of water commonly determines the nature of thecollection, purification, transmission, and distribution works.Common sources of freshwater and their development are asfollows:

1. Rainwater:

(a) From roofs, stored in cisterns, for small individ-ual supplies.

(b) From larger, prepared watersheds, or catches,stored in reservoirs, for large communal supplies.

2. Surface water:

(a) From streams, natural ponds, and lakes of suffi-cient size, by continuous draft.

(b) From streams with adequate flood flows, by inter-mittent, seasonal, or selective draft of clean flood-waters, and their storage in reservoirs adjacent tothe streams, or otherwise readily accessible fromthem.

(c) From streams with low dry-weather flows butsufficient annual discharge, by continuous draftthrough storage of necessary flows in excess ofdaily use in one or more reservoirs impoundedby dams thrown across the stream valleys.

(d) From brackish and seawater by desalination.Desalination is an artificial process by whichsaline water is converted to freshwater. The mostcommon desalination processes are distillationand reverse osmosis. Desalination is currentlyexpensive compared to most alternative sourcesof water, and only a small fraction of total humanuse is satisfied by desalination. It is only eco-nomically practical for high-valued uses (suchas household and industrial uses) in arid areas.The most extensive use is in the Persian (Ara-bian) Gulf. Mildly saline waters (brackish) aredesalted most economically by reverse osmosis;

4 Chapter 1 Introduction to Water Systems

strongly saline waters by evaporation and con-densation.

3. Groundwater:

(a) From natural springs.

(b) From wells.

(c) From infiltration galleries, basins, or cribs.

(d) From wells, galleries, and, possibly, springs, withflows augmented from some other source (i)spread on the surface of the gathering ground,(ii) carried into charging basins or ditches, or (iii)led into diffusion galleries or wells.

(e) From wells or galleries with flows maintainedby returning to the ground the water previouslywithdrawn from the same aquifer for cooling orsimilar purposes.

Several schemes have been proposed to make use oficebergs as a water source; to date, however, this has onlybeen done for novelty purposes. One of the serious movestoward the practical use of icebergs is the formation of anArabian–American investment group to search for the opti-mal way to transport and melt icebergs for use as a source ofdrinking water supply without the need for on-land storage.Glacier runoff is considered to be surface water.

An iceberg is a large piece of freshwater ice that hasbroken off from a snow-formed glacier or ice shelf and isfloating in open water. Because the density of pure ice isabout 920 kg/m3 and that of sea water about 1025 kg/m3,typically only one-tenth of the volume of an iceberg is abovewater. The shape of the rest of the iceberg under the water canbe difficult to surmise from looking at what is visible abovethe surface. Icebergs generally range from 1 to 75 m (about3–250 ft) above sea level and weigh 100,000–200,000 metrictonne (about 110,000–220,000 short ton). The tallest known

iceberg in the North Atlantic was 168 m (about 551 ft) abovesea level, making it the height of a 55 story building. Despitetheir size, icebergs move an average of 17 km (about 10 mi)a day. These icebergs originate from glaciers and may havean interior temperature of –15◦C to −20◦C (5◦F to − 4◦F).

Municipal supplies may be derived from more thanone source, the yields of available sources ordinarilybeing combined before distribution. Dual public water sup-plies (see Chapter 8) of unequal quality are unusual inNorth America. However, they do exist, for example, as ahigh-grade supply for general municipal uses and a low-grade supply for specific industrial purposes or firefighting.Unless the low-grade (nonpotable) supply is rigorously dis-infected, its existence is frowned on by health authoritiesbecause it may be cross-connected, wittingly or unwittingly,with the high-grade (potable) supply. A cross-connection isdefined as a junction between water supply systems throughwhich water from doubtful or unsafe sources may enter anotherwise safe supply.

1.4 RAINWATER

Rain is rarely the immediate provenance of municipal watersupplies. Instead, the capture of rainwater is confined to farmsand rural settlements usually in semiarid regions devoid ofsatisfactory ground or surface waters. On homesteads, rain-water running off roofs is led through gutters and downspoutsto rain barrels or cisterns situated on or in the ground. Storagetransforms the intermittent rainfall into a continuous supply.For municipal service, sheds or catches on ground that isnaturally impervious or made tight by grouting, cementing,paving, or similar means must usually be added.

The gross yield of rainwater is proportional to the receiv-ing area and the amount of precipitation. However, some rain

EXAMPLE 1.1 CALCULATING THE VOLUME OF RAINFALL THAT CAN BE COLLECTED FROM ABUILDING ROOF

Make a rough estimate of the volume in gallons or liters of water that can be caught by 3,000 ft2 (278.7 m2) of horizontally projectedroof area (the average area of American farm buildings) in a region where the mean annual rainfall is 15 in. (38.1 cm).

Solution 1 (US Customary System):

Gross yield = 3,000 ft2 × (15∕12 ft) × 7.48 gal∕ft3 = 28,100 gal annually = 28,100 gal∕365 days= 77 gpd.

Net yield approximates two-thirds gross yield = 18,800 gal annually = 51 gpd.

About half the net annual yield, or 9,400 gal = 1,250 ft3, must normally be stored to tide the supply over dry spells.

Solution 2 (SI System):

Gross yield = (278.7 m2)(38.1∕100 m)(1,000 L∕m3) = 106,178 L annually = 291 L∕day= 291 L∕d.

Net yield approximates two-thirds gross yield = 291 L∕d (2∕3) = 194 L∕d = 70,790 L∕year.

About half the net annual yield = 0.5 (70,790 L∕year) = 35,395 L = 35.4 m3 must be stored to tide the supply over dry spells.

1.5 Surface Water 5

is blown off the roof, evaporated, or lost in wetting the col-lecting surfaces and conduits and in filling depressions orimproperly pitched gutters. Also, the first flush of water mayhave to be wasted because it contains dust, bird droppings,and other unwanted materials. The combined loss may behigh. A cutoff, switch, or deflector in the downspout permitsselective diversion of unwanted water from the system. Sandfilters will cleanse the water as it enters the cistern and preventits deterioration via the growth of undesirable organisms andconsequent tastes, odors, and other changes in attractivenessand palatability.

The storage to be provided in cisterns depends on thedistribution of rainfall. Storage varies with the length of dryspells and commonly approximates one-third to one-half theannual consumption. If rainfalls of high intensity are to becaptured, standby capacity must exist in advance of filtration.Because their area is small, roofs seldom yield much water.A careful analysis of storm rainfalls and seasonal variationsin precipitation is, therefore, required.

1.5 SURFACE WATER

In North America by far the largest volumes of municipalwater are collected from surface sources. The quantities thatcan be gathered vary directly with the size of the catch-ment area, or watershed, and with the difference betweenthe amounts of water falling on it and the amounts lost byevapotranspiration. The significance of these relationships towater supply is illustrated in Fig. 1.1. Where surface waterand groundwater sheds do not coincide, some groundwatermay enter from neighboring catchment areas or escape tothem.

1.5.1 Continuous Draft

Communities on or near streams, ponds, or lakes may taketheir supplies from them by continuous draft if stream flowand pond or lake capacity are high enough at all seasons ofthe year to furnish requisite water volumes. Collecting worksordinarily include (a) an intake crib, gatehouse, or tower; (b)an intake conduit; and (c) in many places, a pumping station.On small streams serving communities of moderate size, anintake or diversion dam may create sufficient depth of waterto submerge the intake pipe and protect it against ice. Fromintakes close to the community the water must generally belifted to purification works and thence to the distributionsystem.

Most large streams are polluted by wastes from upstreamcommunities and industries. Purification of their waters isthen a necessity. Cities on large lakes usually guard their sup-plies against their own and their neighbor’s wastewater andspent industrial-process waters by moving their intakes faraway from shore and purifying both their water and wastew-ater. Diversion of wastewater from lakes will retard the lakes’eutrophication.

1.5.2 Selective Draft

Low stream flows are often left untouched. They may bewanted for other downstream purposes or they may be toohighly polluted for reasonable use. Only clean floodwatersare then diverted into reservoirs constructed in meadow landsadjacent to the stream or otherwise conveniently available.The amount of water so stored must supply demands duringseasons of unavailable stream flow. If draft is confined to aquarter year, for example, the reservoir must hold at leastthree-fourths of the annual supply. In spite of its selectionand long storage, the water may have to be purified.

1.5.3 Impoundage

In their search for clean water and water that can be broughtand distributed to the community by gravity, engineers havedeveloped supplies from upland streams. Most of them aretapped near their source in high and sparsely settled regions.To be of use, their annual discharge must equal or exceedthe demands of the community they serve for a reasonablenumber of years in the future. Because their dry season flowsgenerally fall short of concurrent municipal requirements,their floodwaters must usually be stored in sufficient vol-ume to ensure an adequate supply. Necessary reservoirs areimpounded by throwing dams across the stream valley. In thisway, amounts up to the mean annual flow can be utilized. Thearea draining to an impoundment is known as the catchmentarea or watershed. Its economical development depends onthe value of water in the region, but it is a function, too,of runoff and its variation, accessibility of catchment areas,interference with existing water rights, and costs of construc-tion. Allowances must be made for evaporation from newwater surfaces generated by the impoundage (Fig. 1.2) andalso often for release of agreed-on flows to the valley belowthe dam (compensating water). Increased ground storage inthe flooded area and the gradual diminution of reservoir vol-umes by siltation must also be considered.

Intake structures are incorporated in impounding damsor kept separate. Other important components of impoundingreservoirs are (a) spillways safely passing floods in excess ofreservoir capacity and (b) diversion conduits safely carryingthe stream past the construction site until the reservoir hasbeen completed and its spillway can go into action. Analysisof flood records enters into the design of these ancillarystructures.

Some impounded supplies are sufficiently safe, attrac-tive, and palatable to be used without treatment other thanprotective disinfection. However, it may be necessary toremove high color imparted to the stored water by the decom-position of organic matter in swamps and on the floodedvalley bottom; odors and tastes generated in the decomposi-tion or growth of algae, especially during the first years afterfilling; and turbidity (finely divided clay or silt) carried intostreams or reservoirs by surface wash, wave action, or bank

6 Chapter 1 Introduction to Water Systems

Figure 1.2 A watershed lake in Western Missouri provides watersupply (Courtesy of the National Resources Conservation Serviceand USDA).

erosion. Recreational uses of watersheds and reservoirs maycall for treatment of the flows withdrawn from storage.

Much of the water in streams, ponds, lakes, and reser-voirs in times of drought, or when precipitation is frozen, isseepage from the soil. Nevertheless, it is classified as surface

runoff rather than groundwater. Water seeps from the groundwhen surface streams are low and to the ground when sur-face streams are high. Release of water from ground storageor from accumulations of snow in high mountains is a deter-mining factor in the yield of some catchment areas. Althoughsurface waters are derived ultimately from precipitation, therelations between precipitation, runoff, infiltration, evapora-tion, and transpiration are so complex that engineers rightlyprefer to base calculations of yield on available stream gaug-ings. For adequate information, gaugings must extend over aconsiderable number of years.

1.6 GROUNDWATER

Smaller in daily delivery, but many times more numerousthan surface water supplies, are the municipal and privategroundwater supplies of North America. Groundwater isdrawn from many different geological formations: (a) fromthe pores of alluvial (water-borne), glacial, or aeolian (wind-blown) deposits of granular, unconsolidated materials suchas sand and gravel, and from consolidated materials such assandstone; (b) from the solution passages, caverns, and cleav-age planes of sedimentary rocks such as limestone, slate, andshale; (c) from the fractures and fissures of igneous rocks;and (d) from combinations of these unconsolidated and con-solidated geological formations. Groundwater sources, too,have an intake or catchment area, but the catch, or recharge,is by infiltration into soil openings rather than by runoff overits surface. The intake area may be nearby or a considerabledistance away, especially when flow is confined within awater-bearing stratum or aquifer (from Latin aqua, “water,”and ferre, “to bear”) underlying an impervious stratum oraquiclude (from Latin aqua, “water,” and cludere, “to shut”or “to close out”).

EXAMPLE 1.2 ESTIMATES OF YIELDS FROM WATERSHEDS AND STORAGE REQUIREMENTS

Certain rough estimates of the yield of surface watersheds and storage requirements are shown in Fig. 1.1. Rainfall is used as thepoint of departure, merely to identify the dimensions of possible rainfall–runoff relationships. Determine

1. The yields from the watersheds,

2. The storage requirements,

3. The number of people who can be supported by a drainage area of 100 mi2 (259 km2) if there is adequate impoundage forwater storage, and

4. The number of people who can be supported by a drainage area of 100 mi2 (259 km2) if there is no impoundage for waterstorage.

The following assumptions are made: (a) rainfall = 20 in.∕km2 annually = 19.6 cm∕km2, (b) a stream flow of about 1 MGD/km2

(million gallons per day per square mile) or (1.547 ft3/s)/km2 [or 1.46 MLD/km2 (million liters per day per square kilometer)] is a goodaverage for the well-watered sections of North America, (c) for 75% development (0.75 × 1 MGD∕km2 or 0.75 × 1.46 MLD∕km2),about half a year’s supply must generally be stored. In semiarid regions storage of three times the mean annual stream flow isnot uncommon, that is, water is held over from wet years to supply demands during dry years, (d) average water consumption =150 gpcd = 567.8 Lpcd, (e) for water supply by continuous draft, low water flows rather than average annual yields govern. Inwell-watered sections of North America, these approximate 0.1 ft3/s or 64,600 gpd/km2 (or 28.32 L/s, or 0.094316 MLD/km2).

1.6 Groundwater 7

Solution 1 (US Customary System):

1. The following conversion factors and approximations are being employed:

1 in. rainfall∕km2 = 17.378 MG

Hence, 20 in.∕km2 annually = 20 × 17.378 = 348 MG or 348∕365 = 0.952 MGD.

2. A stream flow of about 1 MGD/km2 is a good average for the well-watered sections of North America. Not all of it can beadduced economically by storage.

For 75% development (0.75 MGD/km2, or 750,000 gpd/km2), about half a year’s supply must generally be stored. Fora catchment area of 100 km2, therefore

Storage = (0.75 MGD∕km2)(100 km2) × (0.5 × 365 days) = 13,688 MG = 13.5 BG (billion gallons) approximately.

In semiarid regions storage of three times the mean annual stream flow is not uncommon, that is, water is held over from wetyears to supply demands during dry years.

3. For an average consumption of 150 gpcd, the drainage area of 100 km2 and impoundage of 13.5 BG will supply a populationof 100 × 750,000∕150 = 500,000 persons.

4. For water supply by continuous draft, low water flows rather than average annual yields govern.In well-watered sections of North America, these approximate 0.1 ft3/s or 64,600 gpd/km2.A catchment area of 100 km2, therefore, can supply without storage

100 × 64,600∕150 = 43,000 people.

This is compared against 500,000 people in the presence of proper storage.

Solution 2 (SI System):

1. The following conversion factors and approximations are being employed:

1 cm∕km2 = 67.12 ML (million liters)

Hence, 19.6 cm/km2 annually = 19.6 × 67.12 = 1315.6 ML annually = 3.6 MLD.

2. A stream flow of about 1.46 MLD/km2 is a good average for the well-watered sections of North America. Not all of it canbe adduced economically by storage.

For 75% development (0.75 × 1.46 MLD∕km2), about half a year’s supply must generally be stored.For a catchment area of 259 km2, therefore

Storage = 0.75(1.46 MLD∕km2)(259 km2)(0.5 × 365) = 51,758 ML = 51.758 BL (billion liters).

In semiarid regions storage of three times the mean annual stream flow is not uncommon, that is, water is held over from wetyears to supply demands during dry years.

3. For an average consumption of 567.8 Lpcd, the drainage area of 259 km2 and impoundage of 51.758 BL will supply apopulation of

(0.75 × 1.46 MLD∕km2)(259 km2)(1,000,000 L∕ML)∕(567.8 Lpcd) = 500,000 persons.

4. For water supply by continuous draft, low water flows rather than average annual yields govern. In well-watered sections ofNorth America these approximate 28.32 L/s or 0.094316 MLD/km2.

A catchment area of 259 km2, therefore, can supply without storage

(259 km2)(0.094316 MLD∕km2)(1,000,000 L∕ML)∕(567.8 Lpcd) = 43,000 people.

This is compared against 500,000 people in the presence of proper storage.

8 Chapter 1 Introduction to Water Systems

The maximum yield of groundwater is directly propor-tional to the size of the intake area and to the differencebetween precipitation and the sum of evapotranspiration andstorm runoff. Laterally, flow extends across the width of theaquifer; vertically, it is as deep as the zone of open poresand passages in Earth’s crust and as shallow as the ground-water table. When the water surface rises and falls withseasonal changes in recharge, flow is unconfined or free, andthe groundwater table slopes downward more or less parallelto the ground surface. Flow then moves at right angles tothe water table contours. If a porous stratum dips beneathan impervious layer, flow is confined as in a pipe droppingbelow the hydraulic grade line. When this kind of aquifer istapped, artesian water rises from it under pressure, in somegeological situations, even in free-flowing fountains. In othergeological formations, water is perched on a lens of imper-vious material above the true groundwater table.

Groundwater reaches daylight through springs when (a)the ground surface drops sharply below the normal ground-water table (depression springs); (b) a geological obstructionimpounds soil water behind it and forces it to the surface(contact springs); and (c) a fault in an impervious stratumlets artesian water escape from confinement (also contactsprings). A cutoff wall carried to bedrock will hold backsubsurface as well as surface flows behind an impoundingdam and so put the full capacity of the catchment area touse unless there is lateral leakage through the sides of thereservoir or around the abutments of the dam.

The rate of flow through the substantially vertical cross-section of ground at right angles to the direction of flowis not great. Because of the high resistance of the normallynarrow pores of the soil, the water moves forward only slowly,traveling about as far in a year as stream flow does in anhour. Natural rates of flow are seldom more than a few feetper hour (or meters per hour); nor are they less than a fewfeet per day (or meters per day) in aquifers delivering usefulwater supplies. However, if a well is sunk into the groundand the level of water in it is lowered by pumping, water isdischarged into the well not only from the direction of naturalflow but from all directions. That is why wells can be spacedmany times their own diameter apart and yet intercept mostof the water escaping through the intervening space.

1.6.1 Springs

Springs are usually developed to capture the natural flowof an aquifer. In favorable circumstances their yield canbe increased by driving collecting pipes or galleries, moreor less horizontally, into the water-bearing formations thatfeed them. Pollution generally originates close to the pointof capture. It is prevented by (a) excluding shallow seep-age waters through encircling the spring with a watertightchamber penetrating a safe distance into the aquifer and (b)diverting surface runoff away from the immediate vicinity.Some springs yield less than 1 gpm (3.78 L/min); a few yield

Figure 1.3 A well provides about 1.5 MGD (5.68 MLD) of waterto Central Maui, HI (Courtesy of the Department of Water Supply,Maui County, HI).

more than 50 MGD (189 MLD). Some are perennial; othersare periodically or seasonally intermittent.

1.6.2 Wells

Depending on the geological formations through which theypass and on their depth, wells are dug, driven, bored, ordrilled into the ground. A well and its pumping equipmentare shown in Fig. 1.3. Dug and driven wells are usuallyconfined to soft ground, sand, and gravel at depths normallyless than 100 ft (30 m). Hard ground and rock generally callfor bored and drilled wells sunk to depths of hundreds andeven thousands of feet. In well-watered regions successfulwells of moderate depth and diameter yield 1–50 gpm (4–190 L/min) in hard rock and 50–500 gpm (190–1900 L/min)in coarse sand and gravel as well as coarse sandstone. Wellsin deep aquifers may yield 100 gpm (400 L/min) or more.

Except in hard rock, particularly limestone, without sandor gravel cover, wells are generally not polluted by lateralseepage but by vertical entrance of pollution at or near theground surface. Pollution is excluded by watertight casings orseals extending into the aquifer and at least 10 ft (3 m) belowthe ground surface, together with diversion of surface runofffrom the well area and its protection against inundation bynearby streams.

1.6.3 Infiltration Galleries

Groundwater traveling toward streams or lakes from neigh-boring uplands can be intercepted by infiltration gallerieslaid more or less at right angles to the direction of flow andcarrying entrant water to pumping stations. Water is drawninto more or less horizontal conduits from both sides, or theriverside is blanked off to exclude the often less satisfac-tory water seeping in from the river itself. Infiltration basins