An integrated membrane operation in seawater and brackish water desalination

The "water problem" has been gaining consistent attention since some decades, but in the last years the problem of water shortage has become a global issue. Limited amount of freshwater is caused by inaccessibility to or over-exploitation of sources; increasing demand due to an increasing grow of populations, in particular in that Countries where the "water problem" is already dramatic; the global warming; restriction of water desalination in that regions where energy costs are still affordable. If on the one hand human society must face this problem in order to answer to the society demands, on the other hand environmental protection impose big attention to the adopted solutions. Brackish and sea water desalination; surface water potabilization; industrial water purification, recycle and reuse, are becoming obligatory way to follow!. In this respect, approaches based on the concepts of the process intensification strategy are supposed to offer the better solution even for the "water problem". When thinking to water desalination, water purification by removal of particulates, micro-organisms and polluting substances, and water recycling and reuse in industrial processes by eliminating specific molecules, membrane technology represent the most realistic and straightforward solution. Indeed, membrane operations are characterized by intrinsic efficiency and operational simplicity, high selectivity and permeability for the transport of specific components, compatibility between different membrane operations in integrated systems, low energetic requirement, good stability under operating conditions and environment compatibility, easy control and scale-up, and large operational flexibility, thus representing an important answer for the rationalization of water treatment operations (Drioli and Romano, 2001; Drioli et al., 2004a). Highly integrated membrane systems for water desalination/purification by traditional pressure driven membrane operations and membrane contactors devices, and the redesigning of industrial production cycles by combining various membrane operations suitable for separation, recovering and recycling, is an attractive opportunity because of the synergic effects that can be attained. In this paper is presented an overview of the current technologies for seawater desalination with the motivations of the recent dominant role of the membrane technology, in particular reverse osmosis, in this field; a summary on the other membrane operations used in water desalination and industrial wastewater treatment, with particular attention to that sectors of the industrial world where huge amount of fresh water are used and comparable amount of wastewaters to be disposed-off are produced, such as the textile and leather as well as the food industry, is even reported.