Action Level: The level of lead or copper which, if exceeded, triggers treatment or other requirements that a water system must follow.
Activated Carbon: A water treatment medium, found in block, granulated, or powdered form, which is produced by heating carbonaceous materials, such as coal, wood, or coconut shells, in the absence of air, creating a highly porous adsorbent material. Activated carbon is commonly used for dechlorination, organic chemical reduction and radon reduction, and is recognized by the US EPA as the best available technology for reduction of organic chemicals from drinking water.
Acute Health Effect: An immediate (i.e. within hours or days) effect that may result from exposure to certain drinking water contaminants (e.g., pathogens).
Alkalinity: The quantitative capacity of water to neutralize an acid; that is, the measure of how much acid can be added to a liquid without causing a significant change in pH. Alkalinity is not the same as pH because water does not have to be strongly basic (high pH) to have high alkalinity. In the water industry, alkalinity is expressed in mg/l of equivalent calcium carbonate. There are three kinds of alkalinity: carbonate, bicarbonate, and hydroxide alkalinity. Total alkalinity is the sum of all three kinds of alkalinity. Different tests are used to determine the quantity of the different kinds of alkalinities present in water.
Amoeba: A single celled protozoan that is widely found in fresh and salt water. Some types of amoebas cause diseases such as amoebic dysentery.
Aquifer: A natural underground layer, often of sand or gravel, that contains water.
Automatic water softener (or Automatic Filter): A water softener (or filter) that is equipped with a clock timer, meter, or sensor which automatically initiates the backwash and/or regeneration process at the preset intervals of time. A predetermined number of gallons of water usage or as determined by a sensor. All operations, including bypass of treated or untreated water (depending upon design), backwashing, brining, rinsing, and returning the unit to service are performed automatically.
Bacteria: Unicellular microorganisms which typically reproduce by cell division. Although usually classed as plants, bacteria contain no chlorophyll. Many different types of bacterial organisms are often found in drinking water.
Barrier Layer: This refers to the active layer of membrane material that actually separates the impurities from the product stream or permeate. This barrier layer is supported by a micro-porous support layer, usually made from polysulfone, which is cast on a non-woven support material.
Best Available Technology: The water treatment(s) that EPA certifies to be the most effective for removing a contaminant.
Brine: A strong solution of salt(s), such as the sodium chloride or potassium brine used in the regeneration of ion exchange water softeners, but also applied to the mixed sodium, calcium and magnesium chloride waste solution from regeneration.
Brine Tank: A tank which sits beside the softening unit and acts as a salt storage and brine supply.
Cartridge Filter: Cartridge filters are a widely used and have been utilized for water treatment for many decades. Cartridges are usually rated in microns. 40 microns is considered the largest particle visible to the human eye. Typical prefiltration requirements for reverse osmosis systems are around 5 microns.
Chemical Feeder: A mechanical device designed to introduce chemicals into a water system, more or less accurately in proportion to water flow.
Chronic Health Effect: The possible result of exposure over many years to a drinking water contaminant at levels above its MCL.
Coliform Bacteria: A group of related bacteria whose presence in drinking water may indicate contamination by disease-causing microorganisms.
Contaminant: Anything found in water (including microorganisms, minerals, chemicals, radionuclides, etc.) which may be harmful to human health.
Contamination: The addition of any physical, chemical, biological or radiological substance to water which reduces the value of the water, or interferes with its intended use.
Cryptosporidium: A microorganism commonly found in lakes and rivers which is highly resistant to disinfection. Cryptosporidium has caused several large outbreaks of gastrointestinal illness, with symptoms that include diarrhea, nausea, and/or stomach cramps. People with severely weakened immune systems (that is, severely immuno-compromised) are likely to have more severe and more persistent symptoms than healthy individuals.
Cycle: A complete course of ion exchange operation. For instance, a complete cycle of cation exchange would involve: regeneration of the resin, rinse to remove excess regenerant, exhaustion, backwash, and finally regeneration again.
Dealkalization: A process for the reduction of alkalinity in a water supply. It is generally accomplished by a chemical feed processor combined cation and anion exchange systems.
Dechlorination: The removal of excess or free chlorine from a water supply by adsorption with activated carbon or by catalytic type filter media.
Deionization: The removal of ionized minerals and salts from a solution using a two-phase ion exchange procedure.
Desalination: The removal of dissolved inorganic solids (salts) from a solution to make it free of dissolved salts.
Disinfectant: A chemical or physical process that kills microorganisms such as bacteria, viruses, and protozoa.
Distribution System: A network of pipes leading from a treatment plant to customers’ plumbing systems.
Feed Water: The incoming water of a water treatment system that has not yet been treated.
Filter: A device used to clean water by removing contaminants before it is fed into the softener or supply lines.
Filtration: The process of passing water through a porous substance to remove solids in suspension.
Flow Rate: The volume of solution which passes through a given quantity of resin within a given time.
Giardia lamblia: A common protozoan found in water that can cause contagious waterborne disease.
Greensand: A natural mineral that possesses ion exchange properties, used in water softeners.
Ground Water: Water pumped and treated from aquifers below the earth’s surface.
Hard Water: Water with a total hardness of one grain per gallon or more, as calcium carbonate equivalent.
Hardness: A characteristic of natural water due to the presence of dissolved calcium and magnesium.
Influent: The water entering a water treatment device.
Inorganic Contaminants: Mineral-based compounds such as metals, nitrates, and asbestos, occurring naturally or due to human activity.
Inorganic Matter: Matter not derived from living organisms and contains no organically produced carbon.
Ion: An atom or group of atoms in a solution with a positive or negative charge due to electron gain or loss.
Ion Exchange: A reversible process where ions are exchanged between an insoluble medium and a solution.
Ionization: The dissociation of molecules into charged particles.
Lime: The common name for calcium oxide (CaO); hydrated lime is calcium hydroxide, Ca(OH)2.
Lime Scale: Hard water scale containing a high percentage of calcium carbonate.
Manganese: An element sometimes found in groundwater, causing black stains in laundry and fixtures.
Maximum Contaminant Level (MCL): The highest level of a contaminant that EPA allows in drinking water.
Maximum Contaminant Level Goal (MCLG): The level of a contaminant at which there would be no risk to human health.
Mechanical Filter: A filter designed for removing suspended solid particles.
Media (or Multi-Media) Filter: A filtration device using various media types to remove large quantities of suspended particles.
Membrane: A barrier layer used in membrane separation devices for water treatment.
Micro-Filtration: A membrane-based treatment technology with larger pore size than ultrafiltration.
Micron: A measure equal to one millionth of a meter.
Micron Rating: The particle size above which all suspended solids will be removed.
Microorganisms: Tiny living organisms that can cause health issues when consumed in drinking water.
Mineral: An inorganic substance found in the earth’s strata and water.
Nano-Filtration (N/F): A membrane treatment method with lower rejection rates than reverse osmosis.
Operating Pressure: The pressure range over which a water conditioning device functions.
Organic Contaminants: Carbon-based chemicals such as solvents and pesticides in water.
Osmosis: The diffusion of a solvent through a semi-permeable membrane.
Osmotic Pressure: The pressure differential developed due to dissolved solids in water.
Oxidizing Filter: A filter that changes the valence state of dissolved molecules, making them filterable.
Particulate: Visible sediment particles in water.
Parts per Billion / ppb: A measurement unit for reporting water contaminants (one microgram per liter).
Parts per Million / ppm: A measurement unit for water contaminants (one milligram per liter).
Pathogen: A disease-causing organism.
Permeate: Water produced by a membrane process.
pH (potential of Hydrogen): A measure of acidity or alkalinity in water.
Point of Entry: A water treatment device installed at the main inlet of a building.
Point of Use: A water treatment system designed to connect at the actual point of use.
PPM (Parts per Million): A unit of concentration equivalent to milligrams per liter.
Pre-Treatment: Processes used to prepare water for treatment systems.
Pressure Vessel: A container holding membrane elements in water treatment.
Product Water: Treated or purified water produced by a treatment system.
Protozoa: Microscopic one-celled animals living in water, some of which are parasitic.
Radionuclides: Elements emitting radiation that may cause cancer after long-term exposure.
Raw Water: Water in its natural state, prior to any treatment.
Regeneration: The process of returning sodium ions to a water softener mineral bed.
Reject: The water that does not pass through the membrane and is more concentrated.
Rejection Rate: The percentage of dissolved solids prevented from passing through a membrane.
Resin: Synthetic organic ion exchange material used in water softeners.
Reverse Osmosis (R/O): A membrane process to remove dissolved minerals from water.
Softened Water: Water treated to reduce hardness minerals to 1.0 GPG or less.
Sole Source Aquifer: An aquifer that supplies 50 percent or more of an area’s drinking water.
Solvent: A liquid in which other materials dissolve.
Source Water: Water in its natural state before treatment.
Sub-Micronic Filtration: Filtration technology using small pore sizes to remove contaminants.
Surface Water: Water obtained from rivers, lakes, and reservoirs.
TDS (Total Dissolved Solids): A measure of the concentration of all minerals dissolved in water.
Total Hardness: The total hardness components in water, expressed as calcium carbonate equivalent.
Treatment: A required process to reduce the level of a contaminant in drinking water.
Turbidity: The cloudy appearance of water due to suspended particles.
Ultra-Filtration (U/F): A membrane treatment system rejecting large molecules but allowing smaller ones.
Watershed: The land area from which water drains into a stream or reservoir.
Wellhead Protection Area: A protected area surrounding a drinking water well to prevent contamination.