Glossary Of Water Treatment Industry Terms . . . "I"

indicator- A material which can be used to show the endpoint of a chemical reaction, usually by a color change, or a chemical concentration by a depth or shade of color.

influent- The stream entering a unit, stream or process, such as the hard water entering an ion exchange water softener.

inorganic matter - Matter which is not derived from living organisms and contains no organically produced carbon; includes rocks, minerals and metals.

installation- The process in which water conditioning equipment is connected into the water system, and a drain line provided where necessary. The term is also used to refer to the complete assembly of piping, valves, drain line, water conditioning unit and related equipment.

intermittent flow - The term usually applied to the interrupted patterns of water usage; also used in reference to specific on-off flow patterns selected to test the performance of water conditioning equipment under standard conditions, which may or may not be similar to actual patterns of use of installed equipment.

ion - An atom or group of atoms which function as a unit, and have a positive (cation) or negative (anion) electrical charge, due to the gain or loss of one or more electrons. (See ionization.)

ion exchange- A reversible process in which ions are released from an insoluble permanent material in exchange for other ions in a surrounding solution; the direction of the exchange depends upon the affinities of the ion exchanger for the ions present, and the concentrations of the ions in the solution. (See base exchange.)

ion exchanger - A permanent, insoluble material which contains ions that will exchange reversibly with other ions in a surrounding solution. Both cation and anion exchangers are used in water conditioning. (See anion, cation, ion.)

ionization - The process in which atoms gain or lose electrons; sometimes used as synonymous with dissociation, the separation of molecules into charged ions in solution.

ionization constant - A constant specific for each partially ionizable chemical compound to express the ratio of the concentration of ions from the compound to the concentration of un-ionized compound.

iron - An element often found in ground water. It is objectionable in water supplies because of the staining caused after oxidation (bleach) and precipitation, tastes, and unsightly colors produced when iron reacts with tannin in beverages such as coffee and tea.

iron bacteria- Microorganisms which are capable of utilizing ferrous iron, either from the water or from steel pipe, in their metabolism, and precipating ferric hydroxide in the sheaths and gelatinous deposits. These organisms tend to collect in pipe lines and tanks during periods of low flow, and to break loose in slugs of turbid water to create staining, taste and odor problems. (See Crenothrix polyspora, Gallionella ferruginea.)