Colloid—Suspended solid with a diameter less than 1 micron that can not be removed by sedimentation alone.

Concentrate—The water containing the dissolved solids removed during desalination.

Concentrate management—The handling and disposal or reuse of waste residuals from the desalination system.

Concentration polarization—A phenomenon in which solutes form a dense, polarized layer next to a membrane surface which eventually restricts flow through the membrane.

Consumptive use—Water withdrawn from a source and made unavailable for reuse in the same basin, such as through conversion to steam, losses to evaporation or transpiration, seepage to a saline sink, or contamination. Also referred to as irretrievable or irrecoverable loss.

Deaeration—Removal of oxygen. A pretreatment process in desalination plants to reduce corrosion.

Demand—An economic concept that is used to describe a want for water backed up by a willingness to pay.

Demand schedule (or curve)—A summarization of the quantities and qualities of water that consumers are willing to take at different prices.

Desalination—The process that removes dissolved solids, primarily salts and other inorganic constituents, from a saline water source.

Design-Build (DB)—A delivery approach characterized by a single contractual relationship between the public water provider and a contractor, who develops the project design and oversees its construction. The project is then operated by the owner or contract operator.

Design-Build-Operate (DBO)—A delivery approach involving a single contractor for design, construction, and operation.

Design-Build-Own-Operate-Transfer (DBOOT)—An expansion of the DBO concept in which the contractor also finances the project and initially owns the facility.

Development—Systematic application of knowledge or understanding, directed toward the production of useful materials, devices, and systems or methods, including design, development, and improvement of prototypes and new processes to meet specific requirements.

Dewvaporation—A desalination method where a stream of air is humidified by a falling film of saline water along one side of a heat transfer surface. The air is partially heated by an external source (e.g., solar, waste heat). The heated air then is swept along the condensing side of heat transfer films, where the vapor condenses to a liquid, which is collected as product water

Diffusion—The movement of suspended or dissolved particles or molecules from a more concentrated to a less concentrated area.