The population of the world is increasing day by day and natural water resources have been found insufficient to meet the demand for freshwater. Water scarcity could be the global risk for the next decades if steps will not be taken for the reclamation of wastewater. The methods of wastewater treatment are chemical coagulation, biological degradation, electrochemical methods, adsorption, membrane.The book has been divided into three chapters based on MBRs,ED and adsorption and all the basic principle of these techniques and their mechanisms for waste water treatment have been summarized in the form of review.