This book discusses recent developments and future directions in the field of membrane separation systems. It describes research needed to bring energy-saving membrane separation processes to technical and commercial readiness for commercial acceptance within the next 5 to 20 years. The assessment was conducted by a group of six internationally known membrane separations experts who examined the worldwide status of research in the seven major membrane areas. This encompassed four mature technology areas: reverse osmosis, microfiltration, ultrafiltration, and electrodialysis; two developing areas: gas separation and pervaporation; and one emerging technology: facilitated transport. Membrane based separation technology, a relative newcomer on the separation scene, has demonstrated the potential of saving enormous amounts of energy in the processing industries if substituted for conventional separation systems. It has been estimated that over 1 quad annually, out of 2.6, can possibly be saved in liquid-to-gas separations, alone, if membrane separation systems gain wider acceptance. In recent years great strides have been made in the field and even greater future energy savings should be available when these systems are substituted for such conventional separation techniques as distillation, evaporation, filtration, sedimentation, and absorption. The book pays particular attention to identifying currently emerging innovative processes, and to further improvements which could gain even wider acceptance for the more mature membrane technologies. In all, 38 priority research areas were selected and ranked in order of priority, according to their relevance, likelihood of success, and overall impact. Rationale was presented for all the final selections; and the study was peer reviewed by additional ten experts. The topics that were pointed out as having the greatest research emphasis are pervaporation for organic-organic separations; gas separations; microfiltration; an oxidant-resistant reverse osmosis membrane; and a fouling-resistant ultrafiltration membrane.