WATER SOFTENING WITH POTASSIUM CHLORIDE

WATER SOFTENING WITH POTASSIUM CHLORIDE

WATER SOFTENING WITH POTASSIUM CHLORIDE Process, Health, and Environmental Benefi ts William Wist Jay H. Lehr Rod McEachern A JOHN WILEY & SONS, INC., PUBLICATION

Copyright 2009 by John Wiley & Sons, Inc. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability of fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www.wiley.com. Library of Congress Cataloging-in-Publication Data: Wist, William (1945 2007) Water softening with potassium chloride : process, health, and environmental benefits / William Wist, Jay H. Lehr, Rod McEachern. p. cm. Includes index. ISBN 978-0-470-08713-8 (cloth) 1. Water Softening. 2. Potassium chloride Environmental aspects. 3. Water Purification. 4. Ion exchange. I. McEachern, Rod, 1958 II. Lehr, Jay H., 1936 III. Title. TD466.W57 2009 628.1 666 dc22 2009013333 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1

This book is dedicated to the memory of Bill Wist, for the devotion and love he gave to his family, his research, and his many friends.

CONTENTS PREFACE ACKNOWLEDGMENTS xi 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 vii

viii CONTENTS 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

CONTENTS ix 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

x CONTENTS 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

PREFACE Practical problems associated with hard water, including scale buildup and the precipitation of soap films, have plagued humanity for thousands of years. The introduction of ion exchange resins in the early 1900s offered the first practical means of reducing water hardness, and water softening with cation exchange resins quickly became widespread. The introduction in 1944 of ion exchange resins based on the copolymerization of polystyrene and divinylbenzene (DVB) brought water softening technology to a state of maturity, and use of this resin became the standard method of water softening worldwide. One common feature of water softening by ion exchange was the use of common salt (sodium chloride, NaCl) as regenerant. For many years, sodium chloride was the preferred material for this purpose because of its effectiveness and low cost. However, as the use of home and industrial water softeners spread, the large quantities of spent regenerant released to the environment became a concern. Research was therefore initiated to evaluate the potential use of potash (potassium chloride, KCl) as an alternative to sodium chloride for use as a regenerant in softening applications. Potassium chloride is widely used as a fertilizer, so its use in softening offered the potential of a win - win situation in which the release of sodium to the environment was reduced, while simultaneously providing an effluent that could be used as a fertilizer. At PotashCorp, a research project to evaluate application of potassium chloride as a regenerant was initiated in the late 1980s. Research xi

xii PREFACE performed by Bill Wist showed the effectiveness of KCl as a regenerant and compared its performance to NaCl in critical areas such as solubility, capacity, solubility speed and cycle times. The high quality research patiently done by Bill over many years led to the successful commercialization of KCl as a water softening regenerant under the trade name SoftTouch. Throughout the research and development phase of the SoftTouch project, Bill Wist was the project leader. Bill provided the technical leadership, developed the test protocols, performed the tests, and effectively communicated the results to PotashCorp sales staff, water quality specialists, and the public. As testament to his dedication, Bill even installed a softener with KCl regenerant in his own home, and performed household water softening experiments as part of the test program. As the use of KCl in water softening spread, Bill answered many technical questions for water softening dealers and service people; he also communicated directly with customers. Bill s unique expertise in this field, his practical problem solving abilities, along with his easy - going personality earned him the reputation as the go - to person in the field of KCl for water softening. In his retirement, Bill Wist initiated the idea for this book, as a means of educating the public about the technology of water softening and the effectiveness and environmental benefits of the use of KCl as a regenerant. In addition to his work as researcher, Bill also organized the entire text and wrote several of the chapters. We hope that you find this text interesting and useful as a reference for water softening applications. This text, along with the widespread use of KCl as a regenerant, stands as a legacy to the patient hard work and innovative research performed by Bill Wist.

ACKNOWLEDGMENTS The research and development described in this text was performed while I was employed at the PotashCorp Technical Services pilot plant. I would like to thank PotashCorp management, who supported the SoftTouch project through the many years of research, development, and customer support. Specifically, the interest, support, and technical leadership of Rick Lacroix (VP of Technical Services), Graeme Strathdee (Director of R & D), and Al Mulhall (Manager of R &D) is appreciated. One of the more gratifying results of the KCl research was to witness the emerging use of spent regenerant solutions as graywater for irrigation. The KCl content of this water provides nutrition for plants, which is superior to the past practice of disposing of the NaCl waste to the environment. The contributions of Kim Polizotto to understanding the agronomy and soil science associated with the use of KCl - rich graywater is appreciated. Kim, along with Sid Blair, should also be recognized as key members of the team that helped to spread the word on the use of KCl regenerant. Thanks are also extended to Jay Lehr and Rod McEachern for their contributions to the completion of this book. The excellent technical work on the illustrations done by Patrick Breton, and the support of Creative Fire are gratefully appreciated. xiii

xiv ACKNOWLEDGMENTS The many years of research required thousands of chemical analyses, all of which were performed by Jana Nguyen. The hard work, dedication, and always - positive attitude of Jana is gratefully acknowledged. Finally, I am grateful to my wife Donna, and our children, Darin, Kelly, and Jolene, along with our grandchildren and other family members, whose love and support meant so much to me during the many years of research described in this text. B ill W ist June 25, 2007