Overview of Desalination Techniques

The objective of this chapter is to present an overview of current and future technologies applied to the desalination of brackish and seawater to produce freshwater for supplementing drinking water supplies. Discussion of detailed design concepts and processes of desalination and applications to other impure waters such as wastewater is beyond the scope of this chapter. Where appropriate, references for further reading are introduced. There are three basic categories of water purification technologies that are used for desalination: membrane technologies, distillation processes (thermal technologies), and chemical approaches. Some water purification plants use a combination of these technologies. Membrane technologies are the most common technology of desalination in the United States, while thermal technologies are not widely used in the United States. A brief overview of thermal technologies is included in this chapter. Chemical approaches include processes such as ion exchange, which is considered impractical for treating waters with high levels of dissolved solids. The chapter also includes a summary of new technologies under research and development for possible applications to desalination.