The purpose of this handbook is to provide drinking water and water reuse professionals with information that can be used to answer the question, "If my system has a contaminant approaching or above the maximum contaminant level, is ion exchange a feasible technology and if so, what would be the basic characteristics of the ion exchange system?" This handbook provides information regarding the selection and design of ion exchange processes for water treatment. Additionally, it aims to enhance the understanding of the "package-type systems" that have become so common throughout the industry. To accomplish this goal, information on the resin composition along with a description of the operation of ion exchange systems is described. A fundamental component of this handbook is the use of design examples and calculations provided at the end of many of the chapters. The goal of these examples is to provide insight into the sizing of the process components and enable the user to assess potential impacts on changes to design criteria. Along with these design examples, several case studies are included.