dechlorination - The removal of chlorine residual.
deionization - The removal of all ionized minerals and salts from a solution by a two-phase ion exchange process. First, positively charged ions are removed by a cation exchange resin in exchange for a chemically equivalent amount of hydrogen ions. Second, negatively charged ions are removed by an anion exchange resin for a chemically equivalent amount of hydroxide ions. The hydrogen and hydroxide ions introduced in this process unite to form water molecules. The term, commonly abbreviated as DI, is often used interchangeably with demineralization. (See demineralization, ion exchange.)
demineralization - The removal of ionized minerals and salts from a solution by a two-phase ion exchange procedure, similar to deionization, and the two terms are often used interchangeably. (See deionization, ion exchange.)
detergent - Any material with cleaning powers, including soaps, synthetic detergents, many alkaline materials and solvents, and abrasives. In popular usage the term is often used to mean the synthetic detergents such as ABS of LAS. (See alkyl benzene sulfonate, linear alkyl sulfonate, soap.)
diatomaceous earth - A processed natural material, the skeletons of diatoms, used as a filter medium.
disinfection - A process in which vegetative bacteria are killed; may involve disinfecting agents such as chlorine, or physical processes such as heating. (See aerobic, anaerobic.)
dissolved solids - The weight of matter in true solution in a stated volume of water; includes both inorganic and organic matter; usually determined by weighing the residue after evaporation of the water at 105 or 180C.
distillation - The process in which a liquid, such as water, is converted into its vapor state by heating, and the vapor cooled and condensed to the liquid state and collected; used to remove solids and other impurities from water; multiple distillations are required for extreme purity.
distributor - A device or system designed to produce even flow through all sections of an ion exchanger or filter bed, and to retain the media in the tank or vessel; usually installed at the top and bottom of loose media systems. (See collector.)
dolomite - A specific form of limestone containing chemically equivalent concentrations of calcium and magnesium carbonates; the term is sometimes applied to limestones with compositions similar to true dolomite.
domestic - A term sometimes applied to water conditioning equipment designed for household use.
downflow - A term designating the direction (down) in which water or a regenerant flows through an ion exchanger or filter during any phase of the operating cycle.
drain - A pipe or conduit in a building plumbing system which carries liquids to waste by gravity; sometimes the term is limited to liquids other than sewage.
drain line - A tube or pipe from a water conditioning unit that carries backwash water, regeneration wastes and/or rinse water to a drain or waste system.
