Water Softening with Potassium Chloride: Process, Health, and Environmental Benefits

PREFACE xi

ACKNOWLEDGMENTS xiii

1 WHAT IS POTASSIUM CHLORIDE? 1

Saskatchewan Potash History 2

Potash Mining 3

Solution Mining 9

Processing Potash Ore 13

Storage, Transportation, and Distribution of Potash 27

Potash Products 29

2 WHAT IS HARD WATER? 34

Definition of Hard Water 34

How Hard Water is Created 35

Problems Associated With Hard Water 37

How Hard Water is Measured 39

Uniform Degrees of Hardness 40

Types of Hardness 40

3 LOWERING WATER HARDNESS 43

Ion Exchange 44

Deionization or Demineralization 45

Reverse Osmosis 47

Distillation 49

Precipitation 50

4 THE ION EXCHANGE PROCESS 54

Synthesis and Structure of Ion Exchange Resins 55

Types of Ion Exchange Resins 56

Household Water Softening 57

Typical Household Water Softeners 59

Cocurrent and Countercurrent Regeneration 64

Mathematical Treatment of Ion Exchange Equilibria 66

Selectivity of Ion Exchange Reactions 75

5 BASIC CHEMISTRY OF ION EXCHANGE 78

The Building Blocks of Matter 78

Atomic and Molecular Weights 80

Cations and Anions 83

Chemical Reactions 84

6 OPERATION AND TYPES OF WATER SOFTENERS 86

Historical Methods of Regeneration 86

Operation of a Typical Water Softener 87

Common Sequences of Cycles 93

Types of Water Softeners 93

Sizing a Water Softener 96

7 POTASSIUM CHLORIDE REGENERANT FOR WATER SOFTENING 99

Alternate Regenerants 99

Potassium Chloride Regenerant 101

Initial Comparison of KCl and NaCl 102

Challenges When Using KCl as a Regenerant 110

Frequently Asked Questions 112

8 COMPARISON OF KCl AND NaCl AS REGENERANT 115

Definition of Terms 115

Theoretical Capacities of KCl and NaCl Regenerants 118

Calculation of Regeneration Efficiency 120

Sizing a Softener for Salt Efficiency 121

Implications for Salt Consumption 123

Total Salt Released to the Environment 127

Comparison of KCl and NaCl: Solubility 129

Comparison of KCl and NaCl: Speed of Dissolution 130

Comparison of KCl and NaCl: Capacity 132

Comparison of KCl and NaCl: Used and Unused Regenerant 135

Comparison of KCl and NaCl: Release of Chlorides to the Environment 138

Comparison of KCl and NaCl: Taste 139

Comparison of KCl and NaCl: Generation of Fines 144

Comparison of KCl and NaCl: Sodium Content of Softened Water 145

Comparison of KCl and NaCl: Potassium Content of Softened Water 154

Comparison of KCl and NaCl: Total Dissolved Solids 154

9 ENVIRONMENTAL CONSIDERATIONS 157

Potassium versus Sodium: Impact on Soil 159

Potassium versus Sodium: Impact on Septic Systems 162

Potassium versus Sodium: Impact on Sewage Treatment Systems 164

Potassium versus Sodium: Sewage Sludge 166

Potassium versus Sodium: Algae Growth 166

Potassium versus Sodium: Impact on Plants and Animals 169

Potassium versus Sodium: Use of Recycled Graywater 170

Recycling Regenerant Wastewater 171

Use of Regenerant Wastewater Studies at University of California, Davis 172

In Conclusion 177

10 POTASSIUM AND HUMAN HEALTH 183

Overview 183

Introduction 184

Cellular Physiology of Potassium 184

Potassium Balance 186

Defects in Potassium Elimination 188

Medical Conditions Related to Potassium Excess 189

Medical Conditions Related to Potassium Deficit 191

Indirect Role of Potassium in Health 199

Summary 200

11 ONGOING RESEARCH 209

Iron and Manganese Removal 209

Grade of KCl Regenerant 213

Cocurrent versus Countercurrent Regeneration 215

Portable Exchange Tanks 217

Research into Alternate Regenerants 220

APPENDIX 1 STANDARD TEST PROTOCOL FOR COMPARISON OF KCl AND NaCl REGENERANTS 223

Protocol Development 223

Standard Test Protocol 226

APPENDIX 2 LABORATORY DATA OBTAINED WITH THE STANDARD TEST PROTOCOL 233

APPENDIX 3 ACCELERATED MUSH TEST 243

Apparatus 243

Method 244

INDEX 245