Membrane classification and different membrane technologies will be covered in this. The classification of water based on TDS along with the flux range for each of the source will be discussed. Pre-treatment technologies such as activated carbon filter,dual media filter(DMF) and chemical pre-treatment is discussed in detail. Ultrafiltration(UF) is explained as a pretreatment as well as a membrane filtration technology. The design equations and the process flow diagram (filtration,backwashing and cleaning process) of the Ultrafiltration system is discussed. The pass and stage wise Reverse Osmosis (RO) system is discussed.The design equations and the process and instrumentation diagram of the Reverse Osmosis system is also discussed. Case studies involving the design of DMF,UF and RO system is discussed. The design of RO system with the aid of ROSA software is also discussed.