In the industry, membrane technology can be used for instance for recycling chemicals, cleaning total effluent, or membranes can be used as a 'kidney' in the industry to eliminate contaminants from the water circulation system. The membrane separation processes can be tailored according to the required degree of purification by choosing the convenient membrane. Disposal of concentrate (retentate) obtained from membrane filtration effluent from industry, is a major problem. Many attempts have been made for treatment/disposal of concentrate using conventional biological treatment or land filling. The book discusses principles of membrane separation process (UF, NF and RO) with actual example of its application in paper industry. This book also discusses membrane performance with respect to different process variables. In addition, environmentally and economically beneficial management of membrane concentrate (highly polluted) is also discussed. This book should be useful for graduate and undergraduate students, engineers, researchers, consultants, managers and other professionals working in the environmental engineering and science field.