This course is targeted at engineers who would like to know about the ion exchange system. The ion exchange system is used to remove hardness and reduce Total Dissolved solids. At the end of this course, one would be able to define resin and classify resins. Also, the usage of resin would be explained and one would be able to decide the treatment scheme of the ion exchange system based on the wastewater characteristics. Preparation of the ion exchange resins is also covered in this course. The different types of resins based on both structure and functional groups are explained. The two ways in which these ion exchange systems can be regenerated are also explained. Design exchange capacity would be defined and the exchange capacity of the resins is also given. Also, concepts like pK values are discussed in order to understand why certain acids are weak and certain acids are strong. The process flow diagram and the process instrumentation diagrams are provided to understand the mechanical equipment and the instruments involved in this process. The formulae to calculate the resin volume, regenerate volume, the flow of water wasted during backwash, etc. are covered in this course. At the end of this course, one would be able to design an ion exchange system completely.