Depending on the waste water composition, pre concentrating using a membrane system can dramatically reduce the sizing requirement of the backend evaporations system and thus the system capital and operating cost. To reach high recoveries in a waste water membrane system, appropriate pre-treatment such as softening and pH adjustment is often required. The technologies used in ZLD are sedimentation, dissolved air floatation, biological treatment, media filtration, activated carbon filtration reverse osmosis, and ultrafiltration. Removing the coarse particles and sediments from the wastewater is the first and crucial step. This helps in protecting the membrane and other equipment by preventing its fouling due to coarse particles. In sedimentation, the suspended solids get settled at the bottom due to the gravity principle. Dissolved air flotation helps in the removal of various colloidal materials and dispersed particles. The water then left is used to remove solids that remain after the floatation stage. The dissolved organic material is ultimately disposed of and completed with the help of activated carbon filtration followed by ultrafiltration. The last step of the ZLD process ensures that the residual suspended solids, colloids, and organic matter, including bacteria, viruses. They are treated before the water passes through the reverse osmosis unit. The final process remains to check whether dissolved solids and metals are removed from the water or not. It is to be noted that it would not be possible to reuse the water until released.