The success of two membrane processes, reverse osmosis and ultrafiltration, has helped make membrane processes a central technique in solving separation problems for fluid systems. This book discusses the various applications and developments in membrane technology and shows how accurate membrane processes can be designed. Starting with the local transport phenomena, the behavior of individual elements such as tube or plate membranes and the behavior of the technical unit----the module----are discussed in detail. The book goes on to demonstrate the most effective ways of arranging modules for forming an optimal plant.