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Glossary of Water Terms


Absorption - The physiological process by which substances pass body membranes and enter the bloodstream or other body components from the site of exposure.

Acceptable standards - Guidelines for safe drinking water have been established by the EPA (Environmental Protection Agency), which provide levels for maximum contaminant level (MCL). As well, there are goals for even higher levels of purity for water, called the MCLG (MCL goal).

Acenaphthene - EPA priority pollutant

Acenaphthylene - EPA priority pollutant

Acequia - gravity-driven waterways, can be a simple ditch or be lined with concrete; often used in agricultural systems in the southwest.

Acetaldehydeon CA prop 65 list; toxicity potential: cancer

Acetochlor - on CA prop 65 list; toxicity potential: cancer

Acid - substance with a pH less than 7.0 in water; an in-home example is vinegar or lemon juice

Acid rain - unusually acidic rainfall, generally resulting from nitrogen oxide and sulfur dioxide emissions, which then react with air-borne water.

Acre-foot (acre-ft) - Volume of water required to cover 1 acre of land (43,560 square feet) to a depth of 1 foot. Equal to 325,851 gallons or 1,233 cubic meters.

Acrolein - EPA priority pollutant

Acrylamide - on CA prop 65 list; origin: sewage/wastewater treatment additive; toxicity potential: increased risk of cancer, blood/nervous system problems, male developmental issues; MCL = 0

Acrylonitrile-EPA priority pollutant; on CA prop 65 list; toxicity potential: cancer

Activated carbon - carbon that has been treated to produce many small pores, increasing the available surface area for subsequent adsorption <

Adsorption - binding or adhering of a substance to a surface; in water purification generally refers to the use of Carbon in filtration system, where impurity adsorbs to the carbon surface. Hence, carbon surface area is important for efficiency.

Alachlor - CA Prop 65 list; origin: herbicide runoff; toxicity potential: cancer; MCL= 0-0.002 mg/L

Aldrin - EPA priority pollutant

Alkalinity - another term for the pH of water, meaning that the pH is over 7.0; this can be caused by the presence of limestone in the area, with dissolved carbonates, bicarbonates, and hydroxides

Alluvium – gravel, clay, sand, silt deposit(s) left by flowing water in delta or river valley

Alpha-BHC - EPA priority pollutant, also Beta-BHC, Gamma-BHC, Delta-BHC; Lindane

Alpha emitters – origin:emission from radioactive minerals called alpha radiation; Certain minerals are radioactive and may emit a form of radiation known as alpha radiation. Toxicity potential: increased risk of getting cancer.

Alpha-endosulfan - EPA priority pollutant

Aluminum (Al) - metallic element, non-magnetic; origin: commonly found in nature, possibly implicated in Alzheimer's disease, although data are contradictory.Aluminum is difficult/expensive to extract from bauxite ore, using considerable energy; hence recycling aluminum cans (beer, soda, catfood, etc.) is an appropriate choice, and many town recycle centers will pay for aluminum. Test cans with a magnet - because aluminum is non-magnetic, the magnet will not adhere.

Amoebae - A unicellular organism that can change its shape, and is commonly found in water and/or soil. Also called FLA (free-living amoebae); amoebae may vary in size from 0.25 - 2.5 mm, and may be found in un-purified household water. Hartmannella, Acanthamoeba, orVahlkampfia are most commonly found in households.

Animal waste - excrement and urine from animals such as pets and livestock; not normally found in 'potable' drinking water unless by contamination; may be in unfiltered stream or river water.

Anion – negatively charged ion, like Cl-‑‑, CO3-2

Anion Exchange - see ion exchange, process that separates ions in water filtration that uses anion exchange resins to facilitate deionization and demineralization.

Anthracene - EPA priority pollutant

Anthropogenic pollution - pollution caused by humans

Antimicrobial - Agent that kills microbial growth. See disinfectant, sanitizer, and sterilizer.

Antimony (Sb) - metallic element; EPA priority pollutant; origin: metal contaminant from solder, ceramics, electronics, petroleum refineries; toxicity potential: symptoms include increase in cholesterol & decrease in blood sugar; MCL = 0.006 mg/L

Aquifers - underground water, either non-confined or confined; tapped for use in wells and irrigation.

Arochlor - (PCB Arochlor) - EPA priority pollutants; polychlorinated biphenyl (PCB) group of industrial chemicals; includes Arochlor 1016, 1221, 1232, 1242, 1248, 1254, 1260; origin: leaching from landfills or other waste deposits; toxicity potential: potentially cancer-causing; MCL = 0- 0.05 mg/L

Arsenic (As) - element; EPA priority pollutant; origin: naturally found in soil, occurs in water due to erosion & runoff; contaminant from electronic processing; toxicity potential: poisonous, can also cause long-term health effects when consumed. No presently known beneficial uses in human body. MCL: 0.10 mg/L

Arsenic (As) filters – because arsenic, As, is not easily dissolved in water, when found in a water supply it usually comes from mining, metallurgical operations, or agricultural runoff. As in water has no color, taste or odor, so it can only detected via arsenic-specific water tests. As is potentially quite toxic, and EPA levels are only 0.10 parts per million (10 parts per billion). The common way to remove arsenic from water is a specialized, arsenic selective resin - a strongly basic hybrid Anion Exchange Resin. This is a proprietary resin that has been certified to NSF/ANSI standard 61.

Asbestos (fiber) - EPA priority pollutant; origin: found in water due to erosion or decay of water mains; toxicity potential benign intestinal polyps; MCL: 7 million fibers/L

ASTM - American Society for Testing and Materials.

Atrazineorigin: herbicide runoff; toxicity potential: reproductive or cardiovascular issues; MCL= 0.003mg/L


Bacteria - tiny living organisms, found throughout the planet; some are unhealthy for human when ingested in water; these are removed by water purification methods

Bacterial contamination - for water, this means that bacteria are present, and need to be removed; generally these may be species such as the coliforms or giardia.

Barium (Ba) –origin: found in water due to erosion, discharge of drilling wastes; toxicity potential: increase in blood pressure; MCL: 2 mg/L

Base - (basic) a substance, that has a pH over 7.0; a home example is sodium bicarbonate in water

Benzene - EPA priority pollutant; can act as a pre-carcinogen; origin: factory discharge, leaking of landfills and gas storage tanks; toxicity potential: increased risk of cancer, anemia; MCL = 0 - 0.005

Benzidine - EPA priority pollutant

Benzo(a) anthracene - EPA priority pollutant

Benzo(ghi) perylene - EPA priority pollutant

Benzo(a)pyrene (PAHs) - EPA priority pollutant; origin: leachate from water storage tanks; toxicity potential: increased risk of cancer; reproductive difficulties; MCL = 0 -0.0002

Benzo(b) fluoranthene - EPA priority pollutant

Benzo(k) fluoranthene - EPA priority pollutant

Beryllium (Be) - element; EPA priority pollutant; origin: waste from factories such as aerospace, electrical, metal refineries, coal-burning; toxicity potential: intestinal lesions; MCL = 0.004 mg/L

Beta-BHC - EPA priority pollutant [also Alpha-BHC, Gamma-BHC, Delta-BHC]; Lindane

Beta-endosulfan - EPA priority pollutant

Bicarbonate (HCO3-) - occurs naturally in water due to photosynthesis; non-harmful unless present at very high concentrations

Biocide - substance used to kill some living organisms, such as chlorine used in water purification

Biofilm - a surface layer of microorganisms.

Biological Contaminants - Living organisms, or material derived from living organisms; Agents derived from or that are living organisms (e.g., viruses, bacteria, fungi, and mammal and bird antigens) that can be inhaled and can cause many types of health effects including allergic reactions, respiratory disorders, hypersensitivity diseases, and infectious diseases. Also referred to as microbiologicals or microbials.

Bis (2-chloroethoxy) methane - EPA priority pollutant

Bis (2-chloroethyl) ether - EPA priority pollutant

Bis (2-chloroisopropyl) ether - EPA priority pollutant

Bis (2-ethylhexyl) phthalate -EPA priority pollutant

Bodily wastes - human and animal excretion products such as urine and feces

Body Hydration – The first sign of dehydration is thirst. Recommended minimum water uptake is 8-10 cups (eight oz) of water daily to maintain proper hydration and body function. Symptoms of Dehydration

Brine - A strong solution of salt (s), such as the sodium chloride 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.

Bromate (BrO3-) - origin: byproduct of water disinfection or due to ozonation of naturally occuring bromide; toxicity potential: suspected human carcinogen; MCL: 0.0 - 0.010

Bromoform - EPA priority pollutant

4-bromophenyl phenyl ether - EPA priority pollutant

Budget whole house water filters – smaller water filters that use one to many replacement cartridges in order to filter water Budget Whole House Systems


Butyl benzyl phthalate -EPA priority pollutant


Cadmium (Cd) - element; EPA priority pollutant; origin: found in water due to natural erosion, galvanized pipe corrosion, metal refinery discharge, runoff from battery & paint waste; toxicity potential: kidney damage; MCL = 0.005 mg/L

Calcium (Ca) - Element found in limestone and also in the human body in bones and as an important cellular component. No MCL = non-toxic

Ca2+ - Positively charged calcium ions (cations) present in "hard water". No MCL = non-toxic.

Calibration - The comparison of an instrument response to known values of a parameter being measured.

Cancer - disease state that includes uncontrolled cellular growth; can occur in a variety of different human/animal organs; may arise from prolonged exposure to some environmental contaminants

Carbofuranorigin: leaching from agricultural use; toxicity potential: reproductive, nervous, blood system issues; MCL = 0.4

Carbon absorption - the element carbon, found for example as charcoal, can be used to absorb and remove contaminants from water during purification.

Carbon adsorption - carbon filtration material is used to adsorb or bind, contaminants.

Carbonate (CO3-2) – anion that can occur in water from flow through minerals

Carbon filters - Activated Carbon and Carbon Block Water Filters: Carbon is a very powerful absorbant; several forms are commonly used in water filtration such as Granular Activated Carbon (GAC), and Carbon Block. <>

Carbon Block Water Filters - Generally, Carbon Block Filters ( or "charcoal water filters" ) have higher contaminant removal capability than GAC filters, and they usually have a higher cost.

Activated Carbon and "Block" Filters are rated by size of the particles they can remove.

Carbon Tetrachloride - EPA priority pollutant; originL industrial discharge; toxicity potential: increased risk of cancer; MCL= 0-0.005

Carcinogen - A substance capable of producing cancer in a living organism.

Cation – positively charged ion, like Na+, Ca+2

Cellular toxicant - A chemical which acts as a poison by temperature to meet heating and cooling needs.

Chemical sensitivity - Health problems characterized by effects such as dizziness, eye and throat irritation, chest tightness, and nasal congestion that appear whenever individuals are exposed to certain chemicals. People may react to even trace amounts of chemicals to which they have become sensitized.

Chloraminesorigin: present in water as microbial control agents; toxicity potential: excess levels may result in stomach upset, nasal/eye irritation, anemia; MCL = 4.0 mg/L

Chlordanes - EPA Priority Pollutant; (also alpha- & gamma- chlordanes); origin: residues from banned pesticide; toxicity potential: increased risk of cancer; MCL = 0 - 0.002

Chloride (Cl-) - anionic chlorine, found in table salt; not known to be harmful to humans/animals

Chlorination - process of using chlorine for bacterial remediation in water

Chlorination by-products - chemicals formed in large scale water-purification as a side-product of bacterial remediation/disinfection

Chlorine (Cl2) –origin: present in water to control microbes; toxicity potential: stomach upset; irritation of nose/eye; MCL = 4.0 mg/L

Chlorine dioxide (ClO2)origin: present in water to control microbes; toxicity potential: can result in anemia and nervous system symptoms; infants/children/elderly at risk; MCL = 0.8 mg/L

Chlorine shower filters - Shower Filters provide a lot of benefits, the most important of which is Chlorine Removal. But there are many other advantages of having a shower filter, such as reduction of soap scum, prevention of dry skin and hair, and odor removal. Many chlorine shower filters (sometimes called filtered shower heads ) also remove or greatly reduce synthetic chemicals and organic compounds that can be absorbed through skin. <>

Chlorite (ClO2-) - origin: chemical by-product of disinfection process; toxicity potential: excess may lead to anaemia and nervous system effects; MCL: 0.8-1.0 mg/L

Chlorobenzene - EPA priority pollutant; origin: factory discharge; toxicity potential: liver or kidney issues; MCL = 0-0.1

Chlorodibromomethane - EPA priority pollutant

Chloroethane - EPA priority pollutant

2-chloroethyl vinyl ethers - EPA priority pollutants

ChloroformEPA priority contaminant

2-Chloronaphthalene - EPA priority pollutant

2-Chlorophenol -EPA priority pollutant

4-Chlorophenyl phenyl ether - EPA priority pollutant

Chromium (Cr) - elemental metal; EPA priority pollutant; origin: natural erosion, discharge from pulp & steel mills; toxicity potential: allergic dermatitis; MCL = 0.1 mg/L. The EPA's MCL levels for Chromium include those for both Cr+3 (called Cr-3 and generally safe) and Cr+6 (called Cr-6, and potentially resulting in skin issues as above).

Chronic - longer term health effects, such as diabetes (as compared to 'acute' or short-term)

Chronic effects - Those occurring after repeated long-term exposure and are seen months or years after initiation of exposure.

Chrysene - EPA priority pollutant

Clean Water Act (CWA) – United States federal law governing water pollution (1972), with goal to maintain and restore biological/chemical/physical integrity of waters throughout the nation.

Clean - visually free of sludge, sediment, slime, algae, fungi, rust and scale.

Clean drinking water - our goal; healthful, 'pure' water free of bacteria/contaminants; metals; harmful chemicals; negative tastes or odors

Cleaning - physical and/or chemical removal of scale, corrosion, biofilm, sludge, sediment and extraneous matter.

Clean Drinking water – water from which as many contaminants as possible have been removed; this includes removal of minerals, organic chemicals (such as pesticides), bacteria, and particulates. <>

Coliform bacteria - see Total Coliforms

Colony Forming Unit (cfu) - a colony arising from a viable unit of one bacterium or more in a clump. For statistical significance, only those plates with 30 to 300 cfu's are selected for counting

Colors - contaminants in water can alter the color; these may be diagnostic for types of impurities

Commercial water filtration systems - water filtration systems available for purchase, covering many uses, from pitcher to faucet to refrigerator to shower, and/or whole house systems; also includes specialized systems to remove contaminants such as arsenic, fluoride, iron, lead, organics, and etc.


Commercial water use - Water used for motels, hotels, restaurants, office buildings, other commercial facilities, and institutions. Water for commercial uses comes both from public-supplied sources, such as a county water department, and self-supplied sources, such as local wells.

Compromised immune systems - individuals who are infants, babies, elderly, or who are undergoing clinical/medical treatments such as chemotherapy; may relate to illnesses such as HIV/AIDS that impair the human immune system or render it less efficient.

Conductivity - the ability of water to conduct electricity. Conductivity measurement is used for estimating the amount of total dissolved solids in water.

Contaminants - substance that is unwanted and potentially harmful; for water this includes disinfectants, disinfection byproducts, inorganic chemicals, microorganisms, organic chemicals, radionuclides

Copper (Cu) - elemental metal; EPA priority pollutant; origin: natural erosion and plumbing corrosion; toxicity potential: both long- & short-term effects; caution for person's with Wilson's disease; MCL = 1.3 mg/L

CPSC - Consumer Product Safety Commission.

Countertop filters - water filtration system that is on the 'countertop', usually kitchen, instead of under the sink, or other placement <>

Cryptosporidium- type of organism found in impure water that can cause gastrointestinal distress; may be associated with oocysts; may indicate fecal contamination; removed by appropriate water filtration

Cyanide (CN-) - free cyanide; EPA priority pollutant; origin: fertilizer, plastic, metal/steel factory discharge; toxicity potential: thyroid problems, nerve damage; MCL = 0.2 mg/L

Cyclic patterns of symptoms - One or more symptoms which occur at regular intervals (e.g., every morning).

Cyst - may refer to oocysts of cryptosporidium


2,4-D – origin: herbicidal runoff; toxicity potential: adrenal, kidney, liver disorders; MCL = 0.07

Dalapon – origin: runoff from herbicide used on roadsides; toxicity potential: minor kidney issues; MCL =0.2

4,4-DDD -also known as para-para DDD - EPA priority pollutant

4,4-DDE -also known as para-para DDE - EPA priority pollutant

4,4-DDT - also known as p,p';para-para-DDT - EPA priority pollutant

Debris - trash, particulates

Decaying vegetation - leaf rot, etc., from gardens and/or farms, forests, etc. that may contaminate water

Dehydration – in humans, dehydration occurs when our water intake is too low; this can be serious, and is a particular health concern in particularly hot climates, as severe dehydration can be fatal.<>

Delta-BHC - EPA priority pollutant [also Alpha-BHC, Beta-BHC, Gamma-BHC]; Lindane

Depth filtration - types of water filters that enable water to capture more particulates before clogging or becoming unusable

Detergent - a cleansing agent capable of penetrating biological films, sludge and sediment and having the ability to emulsify oil and hold materials in suspension. Water treatment specialist have developed detergent formulations which are capable of thoroughly cleaning components which are difficult to access and inspect, such as cooling tower fill.

Dibenzo(a,h) anthracene - EPA priority pollutant

1,2-Dibromo-3-chloropropane (DPCP) –origin: orchard/agricultural runoff; toxicity potential: increased risk of cancer; MCL= 0 - 0.0002

1,2-dichlorobenzene, 1,3-dichlorobenzene & 1,4-dichlorobenzene - EPA priority pollutants

o-Dichlorobenzene/p-dichlorobenzene - EPA priority pollutant; origin: discharge from industrial chemical factories; toxicity potential: health risks include changes in blood, liver/kidney/reproductive issues; MCL = 0.6 for o-dichlorobenzene; MCL = 0.075 for p-dichlorobenzene

Dichlorobromomethane - EPA priority pollutant

1,1-Dichloroethane & 1,2-dichloroethane (ethylene dichloride- EPA priority pollutants

1,1-Dichloroethylene -EPA priority pollutant; origin: discharge from industrial chemical factories; toxicity potential: liver problems; MCL = 0.007

cis-1,2 Dichloroethylene –origin: discharge from chemical industrial factories; toxicity potential: liver problems; MCL= 0.07

trans-1,2 Dichloroethylene - EPA priority pollutant; origin: discharge from chemical industrial factories;toxicity potential: liver problems; MCL = 0.1

Dichloromethane- origin: factory discharge; toxicity potential: increased risk of cancer, liver problems; MCL= 0=0.005

2,4-Dichlorophenol - EPA priority pollutant

1,2-Dichloropropane -EPA priority pollutant; origin: factory discharge; toxicity potential: increased risk of cancer; MCL= 0-0.005

1,3-Dichloropropylene - EPA priority pollutant

Diclofop (diclofop methyl)origin: herbicide restricted for use on golf courses (turf), barley, and wheat; potential runoff into water; on California Prop 65 list of known carcinogens; no longer made by Bayer.

Dieldrin - EPA priority pollutant

Di-(2-ethylhexyl) adipate –origin: discharge from chemical factories; toxicity potential: weight loss, liver problems, possible reproductive issues; MCL = 0.4

Di- (2-ethylhexyl) phthalateorigin: factory discharge; toxicity potential: increased risk of cancer; MCL=0 - 0.006

Diethyl Phthalate - EPA priority pollutant

Diffusion - Movement of molecules (gases and some liquids) from a region of higher concentration to a region of lower concentration.

2,4 - Dimethylphenol - EPA priority pollutant

Dimethyl phthalate - EPA priority pollutant

Di-n-Butyl Phthalate- EPA priority pollutant

4,6-Dinitro-o-cresol - EPA priority pollutant

2,4 - Dinitrophenol - EPA priority pollutant

2,4 - Dinitrotoluene & 2,6- Dinitrotoluene EPA priority pollutants

Di-n-octyl phthalate -EPA priority pollutant

Dinoseb– origin: herbicide runoff;toxicity potential: reproductive difficulties; MCL= 0.007

Dioxin (2,3,7,8-TCDD)origin: discharge from factories, emissions from combustion; toxicity potential: increased risk of cancer, reproductive issues; MCL = 0 – 0.00000003

1, 2 - Diphenylhydrazine - EPA priority pollutant

Diposlide - a glass or plastic slide coated with culture media on which microorganisms can be grown and estimated. Legionella does not grow on these media.

Diquat - herbicide runoff; cataracts; MCL = 0.02

Disease causing agents - any biological, chemical, or pharmaceutical substance that may result in known health effects

Disinfectants - One of three groups of anti-microbials registered by EPA for public health uses. EPA considers an antimicrobial to be a disinfectant when it destroys or irreversibly inactivates infectious or other undesirable organisms, but not necessarily their spores. EPA registers three types of disinfectant products based upon submitted efficacy data: limited, general or broad spectrum, and hospital disinfectant.

Dissolved oxygen (O2) - the amount of oxygen gas dissolved in water; cold water holds more dissolved oxygen than does hot water; this is why using freshwater to make tea and/or coffee is recommended, as the dissolved oxygen adds a subtle 'flavour'

Distillation - purification of water by boiling, followed by capturing the 'pure steam' fraction; most contaminants are removed but same may be 'carry-overs' if the boil slightly before or along with the water.

DOE - Department of Energy

Dose - The amount of a pollutant absorbed by the body, usually expressed as an amount per unit of body weight.

Dose-response relationship - The effect of a substance on a body increases as the dose increases; theoretically, the body may respond differently at different dose levels of a given substance.

DPD Test Kit - a kit for measuring free, combined and total chlroine residuals using the reagent DPD (N, N-diethyl-p-phenylene diamine). Many test kits available from swimming pool suppliers measure only total chlorine not free chlorine and consequently should not be used. Free chlorine residuals in excess of 10 mg/L 10 ppm) are capable of bleaching the indicator colour, rendering the test invalid. Samples of water may have to be diluted with distilled water, or other water which does not interfere with the test, to bring the sample within the range of the kit. Allowance must be made for the sample dilution factor when determining the free chlorine residual in the original sample.

Drain tile loop - a continuous length of drain tile or perforated pipe extending around all or part of the internal or external perimeter of a basement or crawlspace footing.

Drain trap - a dip in the drain pipe of sinks, toilets, floor drains, etc., which is designed to stay filled with water, thereby preventing sewer gases from escaping into the room.

Drinking Water Hotline: 1-800-426-4791