Activated Carbon – Adsorptive particles or granules of carbon usually obtained by heating carbon (such as wood). These particles or granules have a high capacity to selectively remove certain trace and soluble materials from water.

Acute Health Effect – An immediate effect, within hours or days, that results from exposure to certain drinking water contaminants.

Aeration – The process of adding air to water. Air can be added to water by passing air through water or passing water through air.

Algae – Microscopic plants that contain chlorophyll and either floating or suspended in water. They may also be attached to structures, rocks or other submerged surfaces.

Alkalinity – The quantitative capacity of water to neutralize an acid. Generally measured in mg/l, as CaCO3.

Ambient Temperature – Temperature of the surrounding air, or other medium.

Artesian Water – Bottled water from a well, tapping a confined aquifer, in which the water level stands at some height above the top of the aquifer.

Aquifer – A natural underground layer, often of sand or gravel, which contains water.


Bacteria – Singular term for bacterium. Microscopic living organisms usually consisting of a single cell.

Best Available Technology – The water treatment(s) that EPA certifies to be the most effective for removing a contaminant.

Biochemical Oxygen Demand (BOD) – The amount of oxygen consumed by microorganisms, mainly bacteria, and by chemical reactions in the biodegradation of organic matter.

Blank – A bottle containing only dilution water or distilled water, to which the sample being tested is not added. Tests are frequently run on a sample and a blank, and the differences are compared.

Bottled Water – Water that is intended for human consumption, sealed in bottles or other containers, with no added ingredients. It may optionally contain safe and suitable anti-microbial agents. Fluoride may be optionally added within the limitations established in 21 CFR section 165.110(b)(4)(ii).

Buffer – A solution of liquid whose chemical makeup neutralizes acids or bases without a great change in pH.


Calcium Carbonate (CACO3) equivalent – An expression of the concentration of specified constituents in water, in terms of their equivalent value to calcium carbonate. For example, the hardness in water, (which is caused by calcium, magnesium and other ions) is usually described as calcium carbonate equivalent.

Calibration – A procedure that checks or adjusts an instruments accuracy by comparison with a standard or reference.

Candidate Contaminant List (CCL) – The primary source of priority contaminants under evaluation by EPA’s drinking water program for potential future regulation. This evaluation includes research on health impacts, analytical methods, treatment technologies, effectiveness, costs and occurrence for drinking water.

CAS Registration Number – A number assigned by the Chemical Abstracts Service to identify a chemical.

Catalyst – A substance that changes the speed or yield of a chemical reaction without being consumed or chemically changed by the chemical reaction.

Cation – A positively charged ion in an electrolyte solution, attracted to the cathode under the influence of a difference in electrical potential. Sodium ion (NA+) is a cation.

Chemical Oxygen Demand – An indirect measure of the amount of oxygen used by inorganic and organic matter in water. The measure is a laboratory test based upon a chemical oxidant, and therefore does not necessarily correlate with biochemical oxygen demand

Chronic Health Effect – The possible result of exposure over many years, to a drinking water contaminant at levels above its MCL.

Coagulants – Chemicals that cause very fine particles to clump together into larger particles. This makes it easier to separate the solids from the water by settling, skimming, draining or filtering.

Code of Federal Register (CFR) – The codification of the general and permanent rules published in the Federal Register by the executive departments and agencies of the Federal Government. The CFR include FDA regulations regarding food production as found in 21 CFR, as well as EPA regulations, found in 40 CFR, governing drinking water produced by water systems.

Coliform – A group of related bacteria whose presence in drinking water may indicate contamination by disease-causing microorganisms.

Compliance – The act of meeting all applicable regulations.

Conductance – A rapid method of estimating the dissolved solids content of a water supply. The measurement indicates the capacity of a sample of water to carry an electrical current, which is related to the concentration of ionized substances in the water. Also called Specific Conductance.

Conductivity – A measure of the ability of a solution, such as water, to carry an electric current.

Cone of Depression – The depression, roughly conical in shape, produced in the water table by the pumping of water from a well.

Confluent Growth – A continuous bacteria growth covering the entire filtration area of a membrane filter, or a portion thereof, in which the bacterial colonies are not discrete.

Consumptive Use – Water removed from available supplies, without direct return to a water resource system, for uses such as manufacturing, agriculture, and food preparation.

Contaminant – Anything found in water (including microorganisms, minerals, chemicals, radionuclides, etc.) that may be harmful to human health.

Corrosivity – The measurement of corrosion potential of a given water (reported using the Langelier Index Scale).

Cryptosporidium – A microorganism commonly found in lakes and rivers that is highly resistant to disinfection and has caused several large outbreaks of gastrointestinal illness.

Curie – A measure of radioactivity. One Curie of radioactivity is equivalent to 3.7 X 1010 or 37,000,000,000 nuclear disintegrations per second.


Degradation – Chemical or biological breakdown of a complex compound into simpler compounds.

Demineralized Water – Water produced by distillation, deionization, reverse osmosis, or other suitable process that meets the definition of purified water in the United States Pharmacopoeia, 23rd revision, January 1, 1995.

Deionized Water – Water that has been produced by a process of deionization and that meets the definition of purified water in the United States Pharmacopoeia, 23rd Revision, January 1, 1995.

Disinfectant – A chemical, such as chlorine, chloramine, chlorine dioxide, or ozone, or physical process such as ultraviolet light, that kills microorganisms like bacteria, viruses, and protozoa.

Disinfection By-Product – A compound formed by the reaction of a disinfectant, such as chlorine, with organic material in the water supply.

Distilled Water – Water that has been produced by a process of distillation that meets the definition of purified water in the United States Pharmacopoeia, 23rd Revision, January 1, 1995.

Drinking Water – Water that is intended for human consumption, that is sealed in bottles or other containers, with no added ingredients except that it may optionally contain safe and suitable anti-microbial agents. Fluoride may be optionally added within the limitations established in 21 CFR Section 165.110(b)(4)(ii)


Electron – An extremely small, negatively charged particle. It is the part of an atom that determines its chemical properties.

Element – A substance which cannot be separated into its constituent parts and still retain its chemical identity. For example, sodium (Na) is an element.

Enteric – Of intestinal origin, especially applied to wastes or bacteria.

EPA – Abbreviation for the United States Environmental Protection Agency

Exemption – The condition of EPA permission, for a water system, not to meet a certain drinking water standard.


FDA Standard of Quality (FDA SOQ) – The maximum acceptable level of a contaminant as determined by the Food and Drug Administration for bottled water. FDA Standards of Quality are located in the 21 CFR Part 165.110.

Fecal Coliform Bacteria – Bacteria found in the intestinal tracts of animals. Its presence in water is an indicator of pollution and possible contamination by pathogens.

Filtration – A process for removing particulate matter from water, via passage through porous media.

Flocculation – The gathering together of fine particles in water by gentle mixing, after the addition of coagulant chemicals, to form larger particles.

Fluoridation – The addition of a chemical to increase the concentration of fluoride ions in drinking water to a predetermined optimum limit to reduce the incidence of dental caries (tooth decay) in children.

Fungi – Mushrooms, molds, mildews, rusts, and smuts, that are small, non-chlorophyll-bearing plants that lack roots, stems and leaves. They occur in natural waters and grow best in the absence of light. Their decomposition may cause objectionable tastes and odors in water.


Giardia Lamblia – A microorganism frequently found in rivers and lakes, if not treated properly, may cause diarrhea, fatigue, and cramps after ingestion.

Grains per Gallon (gpg) – measurement sometimes used to express hardness. One grain per gallon is equivalent to 17.1 mg/l.

Gravimetry – A means of measuring unknown concentrations of water quality indicators in a sample, by weighing a precipitate or residue of the sample.

Ground Water – Water from a subsurface, saturated zone that is under a pressure equal to or greater than atmospheric pressure.

Gross Alpha Particle Activity – Total radioactivity, due to alpha particle emission, as inferred from measurement on a dry sample.

Gross Beta Particle Activity – Total radioactivity, due to beta particle emissions, as inferred from measurement on a dry sample.


Half-Life – The length of time required for the mass, concentration, or activity, of a chemical or physical agent, to be reduced by one-half.

Hardness – The soap-consuming capacity of water which is mostly due to calcium (Ca) and Magnesium (Mg). Typically expressed in mg/l (as CaCO3) or grains per gallon (gpg)

Health Advisory – An EPA document that provides guidance and information on contaminants that can affect human health and that may occur in drinking water, but which EPA does not currently regulate in drinking water.

Heavy Metals – Metallic elements with high atomic weights, such as; mercury, chromium, cadmium, arsenic, and lead. They can damage living things at low concentrations and tend to accumulate in the food chain.

Herbicide – A compound, usually a man-made organic chemical, used to kill or control plant growth.

Heterotrophic Plate Count (HPC) – The number of colonies of heterotrophic bacteria grown on selected solid media at a given temperature and incubation period, usually expressed in: number of bacteria per milliliter of sample.

Hydrogeology – The study of the occurrence, distribution and circulation of the natural waters of the earth.

Hypochlorite – Chemical compounds containing available chlorine, used for disinfection. They are available as liquids, such as bleach, or solids such as powder, granules and pellets.


IBWA Model Code – Document containing industry code of practice as established by the International Bottled Water Association. All IBWA members are audited for compliance against the Model Code annually, during unannounced plant inspections performed by approved third party auditors.

IBWA Standard of Quality (IBWA SOQ) – The maximum acceptable level of a contaminant as determined by the International Bottled Water Association.

Indicator – A substance that gives a visible change, usually of color, at a desired point in a chemical reaction. It is generally at a specified end point.

Inorganic Chemicals – Elemental metals and chemical substances that do not contain carbon or hydrogen, such as calcium and iron.

International Bottled Water Association (IBWA) – The trade association representing the bottled water industry. Founded in 1958, IBWAs membership includes U.S. and international bottlers, distributors and suppliers.


Langelier Index (L.I.) – An index reflecting the equilibrium pH of water with respect to calcium and alkalinity.

Leaching – The process by which substances are dissolved and transported down the soil by re-charge.

Legionella – A genus of bacteria. Some species of which have caused a type of pneumonia called Legionnaires Disease.

Lifetime Exposure – usually assumed to be 70 years, the total amount of exposure to a substance that a human would receive in a lifetime.

Lowest-observed-adverse-effect level (LOAEL) – The lowest dose in an experiment that produced an observable adverse effect.


Man-Made Beta Particle and Photon Emitting – Terms to describe all radionuclides and emitting beta particles and/or photons listed in Maximum Permissible Body Burdens and Maximum Permissible Concentration of Radionuclides in Air or Water for Occupational Exposure, NBS Handbook 69. Exceptions are the daughter products of thorium-232, uranium-235, and uranium-238.

Maximum Contaminant Level Goal (MCLG) – The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.

Maximum Contaminant Level (MCL) – The highest level of a contaminant that is allowed in drinking water as established by the EPA. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.

Maximum Residual Disinfectant Level Goal (MRDLG) – The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLG?s do not reflect the benefits of the use of disinfectants to control microbial contaminants.

Maximum Residual Disinfectant Level (MRDL) – The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

Meniscus – The curved top of a column of liquid, such as water, oil, or mercury, in a small tube.

Methylene-Blue-Active Substances (MBAS) – These substances are used in surfactants or detergents.

Metabolism – The sum of the chemical reactions occurring within a cell or whole organism; including the energy-releasing breakdown of molecules (catabolism) and the synthesis of new molecules (anabolism).

Methyl Orange Alkalinity – A measure of the total alkalinity in a water sample. The alkalinity is measured by the amount of standard sulfuric acid required to lower the pH of the water to 4.5, as indicated by the change in methyl orange from orange color to pink color. Methyl orange alkalinity is expressed as milligrams per liter equivalent to calcium carbonate.

Microbial Growth – The activity and growth of microorganisms such as bacteria, algae, diatoms, plankton and fungi.

Microbiological – Microscopic living organisms, such as bacteria, yeasts, viruses, molds, cysts and algae.

Micrograms per liter (mg/l) – A measure of concentration of a dissolved substance. One microgram per liter (mg/l) is equivalent to one one-thousandth of a milligram of a substance, in a liter of water. One mg/l is equivalent to one part per billion (ppb).

Micron – A unit of length. One millionth of a meter or one thousandth of a millimeter. One micron equals 0.00004 of an inch.

Milligrams per liter (mg/l) – A measure of concentration of a dissolved substance. One milligram per liter (mg/l) is equivalent to one milligram of a substance dissolved in a liter of water. One mg/l is also equivalent to one part per million (1 ppm)

Mineral Water – Water containing not less than 250 parts per million (ppm) total dissolved solids (TDS), coming from a source tapped at one or more boreholes or springs, that originates from a geologically and physically protected underground water source.

Molecular Weight – The molecular weight of a compound in grams is the sum of the atomic weights of the elements in the compound.

Molecule – The smallest division of a compound that still retains or exhibits all the properties of a substance.

Most Probable Number (MPN) – The most probable number of coliform-group organisms per unit volume of sample water. MPN is expressed as the number of organisms per 100 mL of sample water.


No-Observed-Adverse-Effect Level (NOAEL) – The highest dose in an experiment that did not produce an observable adverse effect.

Non-Potable – Water that may contain objectionable pollution, contamination, minerals, or infective agents and is considered unsafe and/or unpalatable for drinking.


Odor Threshold – The minimum odor of a water sample that can just be detected after successive dilutions with odorless water, also called Threshold Odor.

Organic – Substances that come from animal or plant sources. Organic substances always contain carbon.

Organic Chemicals – Compounds with a carbon-hydrogen structure.

Orifice – An opening, or hole, in a plate, wall or partition.

Oxidation-Reduction Potential – The electrical potential required to transfer electrons from one compound or element, the oxidant, to another compound or element, the reductant; used as a qualitative measure of the state of oxidation in water treatment systems.

OSHA – Refers to the Williams-Steger Occupational Safety and Health Act of 1970, a law designed to protect the health and safety of industrial workers and operators of water supply systems or treatment plants. OSHA also refers to the federal and state agencies which administrator the OSHA regulations.

Osmosis – The passage of a liquid from weak solution to a more concentrated solution across a semi-permeable membrane. The membrane allows the passage of the solvent (water) but not the dissolved solids (solutes). This process tends to equalize the conditions on either side of the membrane.

Oxidation – The addition of oxygen, removal of hydrogen, or the removal of electrons from an element or compound.

Ozonation – The application of ozone to water for disinfection or taste and odor control.


Parts Per Billion (PPB) – m/l, a measurement of concentration on a weight or volume basis. This term is equivalent to micrograms per liter.

Parts Per Million (PPM) – A measurement of concentration on a weight or volume basis. This term is equivalent to milligrams per liter (mg/l).

Pathogen – A disease-causing organism.

Performance Evaluation Sample (PE) – A reference sample provided to a laboratory for the purpose of demonstrating that the laboratory can successfully analyze the sample within limits of performance specified by the evaluating agency. The true value, of the concentration of the reference material, is unknown to the laboratory at the time of the analysis.

Permeability – A term referring to the ability of one material to allow another to penetrate and pass through.

Pesticide – Any substance or chemical designed & formulated to kill or control weeds and animal pests. Examples include: algaecide, herbicide, and rodenticide.

pH – The measure of acidity or causticity of a solution. A measurement of 7 is a neutral solution. A measurement of less than 7 is an acidic solution and a measurement of greater than 7 is a basic solution.

Physical Qualities – Characteristics of water such as TDS, Hardness, and pH.

Pico – A prefix used in the metric system and other scientific systems of measurement meaning 10 -12 or 0.00000000001.

Pico curie (pCi) – A measure of radioactivity. One Pico curie of radioactivity is equivalent to 0.037 nuclear disintegrations per second.

Point of Use Treatment Device – A treatment device applied to a single tap used for the purpose of reducing contaminants in drinking water at that one tap.

Potable Water – Water that is safe and satisfactory for drinking and cooking.

Precipitate – An insoluble, finely divided substance that is a product of a chemical reaction within a liquid; or the separation, from a solution, of an insoluble substance.

Primacy – The responsibility for ensuring that a law is implemented, and the authority to enforce a law and its related regulations.

Product Water – Water that has passed through a water treatment plant. All treatment processes are completed or finished.

Public Health Goal – The level of a contaminant in drinking water, below which there is no known or expected risk to health.

Purified Water – Bottled water produced by distillation, deionization, reverse osmosis, or other suitable process, and meets USP criteria.


Qualitative – Describes: kind, type or direction.

Quantitative – Describes: size, magnitude or degree.


Radionuclides – Naturally occurring and man-made elements that emit atomic energy generally in the form of alpha and beta rays, like uranium, radon and radium.

Raw Water – Water in its natural state, prior to any treatment for drinking.

Reagent – A pure chemical substance used to make new products, or in chemical tests, to measure, detect, or examine other substances.

Reverse Osmosis – The application of pressure to a concentrated solution, causing the passage of a liquid from the concentrated solution to a weaker solution, across a semipermeable membrane. The membrane allows the passage of the solvent (water) but not the dissolved solids (solutes).

Reverse Osmosis Water – Water that is produced by a process of reverse osmosis, meeting the definition of purified water in the United States Pharmacopoeia, 23rd Revision, January 1, 1995.

Reference Dose (RD) – The daily exposure level during an entire lifetime of a human, that appears to be without appreciable risk on the basis of all facts known at the time. Same as ADI.

Riparian Rights – A doctrine of state water law, under which a landowner is entitled to use the water on or bordering his property, including the right to prevent diversion or misuse of upstream waters.

Risk Assessment – A qualitative or quantitative evaluation of the environmental, and/or health risk, resulting from exposure to a chemical or physical agent (pollutant); combines exposure assessment results with toxicity assessment results to estimate risk.


Safe Drinking Water ct (SDWA) – The national legislation which directs the U.S. Environmental Protection Agency to promulgate and enforce standards for safe drinking water, necessary to protect public health at public water systems that service 25 or more people, for an average of 60 days per year.

Sample – Water taken from a specific location, at a specific time, that is analyzed for the presence of contaminants.

Sand Filters – Devices that remove some suspended solids from sewage. Air and bacteria decompose additional wastes filtering through, so that cleaner water drains from the bed.

Secondary Drinking Water Standards – Non-enforceable federal guidelines regarding cosmetic effects (such as tooth or skin discoloration) or aesthetic effects (such as taste, odor, or color) of drinking water.

Solution – A liquid mixture of dissolved substances. In a solution it is impossible to see all the separate parts.

Source Water – Water in its natural state, prior to any treatment for drinking.

Sparkling Bottled Water – Bottled water that, after treatment and possible replacement of carbon dioxide, contains the same amount of carbon dioxide that it had at the emergence from the source. Manufacturers may add carbonation to previously noncarbonated bottled water products and label such water appropriately (e.g., sparkling spring water).

Specific Conductance – See: Conductance.

Spore – The reproductive body of an organism, capable of giving rise to a new organism, either directly or indirectly. A spore is usually more resistant to disinfectants and heat than most organisms.

Spring Water – Water derived from an underground formation, from which water flows naturally to the surface of the earth.

Standard Methods for the Examination of Water and Wastewater – A joint publication of the American Public Health Association, American Water Works Association, and the Water Pollution Control Federation outlining the procedures used to analyze the impurities in water and wastewater.

Sterile Water – Water that meets the requirements under Sterility Tests USP 71 in the United States Pharmacopoeia, 23rd Revision, January 1, 1995.

Surfactant – Abbreviation for surface-active agent. It is the active agent in detergents that possesses a high cleaning ability.

Surface Water – Water that originates from sources open to the atmosphere, like rivers, lakes, and reservoirs.

Suspended Solids – Solids that either float on the surface of water, or are suspended in water or other liquids. They are largely removable by laboratory filtering.


Titrate – Titration is the process of adding the chemical reagent in the increments until completion of the reaction, as signaled by the end point. A chemical solution of known strength is added on a drop-by-drop basis until a certain color change, precipitate, or pH change in the sample is observed.

Too Numerous to Count – The total number of bacterial colonies exceeds 200 on a 47-nun diameter membrane filter used for coliform detection.

Total Dissolved Solids (TDS) – The total weight of the solids dissolved in water.

Treatment Technique (TT) – A required process intended to reduce the level of a contaminant in drinking water.

Turbidity – The measurement of the amount of scattering and absorption of light rays, caused by small particles of solid matter, suspended in water.


United States Pharmacopeia (USP) – The official publication for drug product standards, including six water quality standards for pharmaceutical uses.


Virus – The smallest form of microorganisms capable of causing disease, especially a virus of fecal origin, infectious to humans by waterborne transmission.


Watershed – The land area from which water drains into a stream, river, or reservoir.

Well Water – Water from a hole bored, drilled, or otherwise constructed in the ground, tapping the water of an aquifer.

Wet Chemistry – Laboratory procedures used to analyze a sample of water using liquid chemical solutions instead of, or in addition to, laboratory instruments.


International Bottled Water Association (2005, March) Model Code: Bottled Water Code of Practice

US EPA (2005, January) Drinking Water Glossary: A dictionary of Technical and Legal Terms Related to Drinking Water

Water Quality Association Glossary of Terms

National Testing Laboratories, LTD.