D.I. - abbreviation for "deionization"
Deionization - the removal of all ionized minerals and salts (both organic and inorganic) from a solution by a two stage ion exchange procedure. First, positively charged for a chemically equivalent amount of hydrogen ions. Second, negatively charged ions are removed by an ion exchange resin for a chemically equivalent amount of hydroxide ions. The hydrogen and hydroxide ions are introduced in this process unite to form water molecules. The term is often used interchangeably with demineralization.
Demineralization - the removal of ionized inorganic minerals and salts (not organic materials)from a solution by a two phase ion exchange procedure, similar to deionization, and the two terms are often used interchangeably.
Dialysis - the separation of components of a solution by diffusion through a semi-permeable membrane which is capable of passing certain ions or molecules while rejecting others.
Differential Pressure - the difference in pressure at two points in a water system, may be due to differences in elevation or to friction losses or pressure drops due to resistance to flow in pipes, softeners, filters or other devices.
Disinfection - a process in which pathogenic (disease producing bacteria) are killed; may involve disinfecting agents such as chlorine, or physical processes such as heating.
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 or180c.
Distillation - the process in which a liquid, such as water, is converted into its vapor state and collected; used to remove solids and other impurities from water; multiple distillations are required for extreme purity.