Grain (gr) – A unit of weight equal to 1/7000 of a pound or 0.0648 gram.
Grain per Gallon (gpg) – A common basis for reporting water analysis in the United States and Canada. One grain per U.S. gallon equals 17.12 milligrams per liter (mg/l) or parts per million (ppm). One grain per British (Imperial) gallon equals 14.3 mg/l or ppm.
Greensand – A natural mineral, primarily composed of complex silicates, which can be coated with manganese oxide to form a catalytic absorptive surface. This surface is used to attract ferrous iron and manganese as well as to absorb dissolved oxygen which is used to oxidize iron, manganese or hydrogen sulfide.
Hardness – A characteristic of natural water due to the presence of dissolved calcium and magnesium. Water hardness is responsible for most scale formation in pipes and water heaters and forms insoluble “curd” when it reacts with soaps. Hardness is usually expressed in grains per gallon (gpg), parts per million (ppm) or milligrams per liter (mg/l), all as calcium carbonate equivalent.
Hard Water – Water with a total hardness of 1 gpg or more as calcium carbonate equivalent.
Hydrologic Cycle – The natural water cycle, including precipitation of water from the atmosphere as rain or snow, flow of water over or through the earth, and evaporation or transpiration to water vapor in the atmosphere.
Hydrogen Sulfide (H2S) – A gas characterized by an offensive odor, commonly referred to as “rotten egg” odor. Flammable and poisonous in high concentrations, corrosive to most metals and can even tarnish silver. Detectable by most people in concentrations as low as 0.5 ppm.
Hydrocharger – Trade name of a particular type of air induction or injector valve.
Hydrolysis – The chemical degradation of an R.O. membrane in water due to certain conditions such as high pH. Cellulose based membranes are quite susceptible to hydrolysis while the TFC type are virtually immune.
Influent – The stream entering a unit, stream or process, such as the hard water entering an ion exchange water softener.
Ion – An atom, or group of atoms, which function as a unit and have a positive or negative electrical charge due to the gain or loss of one or more electrons.
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.
Iron (Fe) – An element often found dissolved in ground water (in the form of ferrous iron) in concentrations usually ranging from 0-10 ppm (mg/l). It is objectionable in water supplies because of the staining caused after oxidation and precipitation (as ferric hydroxide); because of the tastes; and because of unsightly colors produced when iron reacts with tannins in beverages such as coffee and tea.
Iron Bacteria – Organisms which are capable of utilizing ferrous iron from the water or from steel pipe in their metabolism precipitating ferric hydroxide in their sheaths and gelatinous deposits. These organisms tend to collect in pipelines and tanks during periods of low flow and to break loose in slugs of turbid water to create staining, taste and odor problems.
Magnesium (Mg) – One of the elements making up the earth’s crust, the compounds of which, when dissolved in water, make water hard. The presence of magnesium in water is a factor contributing to the formation of scale and insoluble soap curds.
Manganese (Mn) – An element sometimes found dissolved in ground water, usually with dissolved iron but in lower concentration. Causes black stains and other problems similar to iron.
Manganese Greensand – Greensand which as been processed to incorporate in its pores and on its surface the higher oxides of manganese. The product has a mild oxidizing power and is often used in the oxidation and precipitation of iron, manganese and/or hydrogen sulfide and their removal from water.
Mechanical Filtration – The process of removing suspended particles from water by a straining action. The finest mechanical filters can remove bacteria as small as 0.2 microns.
Media –The selected materials in a filter that form the barrier to the passage of certain suspended solids or dissolved minerals. (Singular of media is medium).
Milligrams per Liter (mg/l) – A unit concentration of matter used in reporting the results of water and wastewater analysis. In dilute water solutions, it is practically equal to parts per million but varies from the ppm in concentrated solutions such as brine. As most analysis are performed on measured volumes of water, the mg/l is a more accurate expression of the concentration and is the preferred unit of measure.
Micron – A linear measure equal to one millionth of a meter or 0.0003937 inches. The symbol for the micron is the Greek letter µ.
Micron Rating – The term applied to a filter or filter medium to describe the particle size above which all suspended solids will be removed throughout the rated capacity. As used in industry standards, this is an “absolute” not “nominal” rating. (Refer to S-200, Recommended Industry Standards for Household & Commercial Water Filters.)
Mineral – A term applied to inorganic substances such as rocks and other matter found in the earth strata, as opposed to organic substances such as plant and animal matter. Minerals normally have definite chemical composition and crystal structure. The term is also applied to matter derived from minerals such as the inorganic ions found in water. The term has been incorrectly applied to ion exchangers, even though most of the modern materials are organic ion exchange resins.
Mineral Salts – The form in which mineral from dissolved rock exist in water. Same as Total Dissolved Solids. This is the so-called inorganic form of minerals. In excess, they cause water to have a disagreeable taste. Some are harmful to human health.
Molecular Weight – The sum of the atomic weights of the individual atoms (from a periodic chart) that make up a molecule of a particular substance (e.g. H2O) H=1 atomic weight, 0=16 atomic weight, therefore, molecular weight = 2 + 16 = 18).
Nanometer – A measure of a wavelength in the electromagnetic spectrum. One nanometer equals 109 meter.
Neutralization – In general, the addition of either an acid or a base to a solution as required to produce a neutral solution. The use of alkaline or basic materials to neutralize the acidity of some water is common practice in water conditioning.
Organic Iron – A ferrous iron molecule which is enveloped in an organically complex molecule that resists oxidation. May be present in water that contains a great deal of colored colloidal turbidity.
Organics – Any of the compounds whose chemical structure is based on carbon (e.g. carbon dioxide, wood, sugar, protein, plastics, methane, THM, TCE, etc.).
Osmosis – A process of diffusion of a solvent, such as water through a semi-permeable membrane, which will transmit the solvent but impede most dissolved substances. The normal flow of solvent is from the dilute solution to the concentrated solution. (See Reverse Osmosis.)
Osmotic Pressure – The pressure created by the tendency of water to flow in osmosis. Every 100 ppm of TDS generates about 1 pound per square inch (psi) of osmotic pressure. This osmotic pressure must first be overcome by the water pressure for the reverse osmosis membrane to be effective.
Oxidation – A chemical process in which electrons are removed from an atom, ion or compound. The addition of oxygen is a specific form of oxidation. Combustion is an extremely rapid form of oxidation while the rusting of iron is a slow form.
Oxidizing Agents – Any substance that oxidizes another substance and is itself reduced in the process. Common examples include: oxygen, chlorine, potassium permanganate, hydrogen peroxide, iodine and ozone.
Ozone (O3) – An unstable form of oxygen occurring naturally in the upper atmosphere or artificially produced because of its strong oxidizing or disinfection characteristics.