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Water Dictionary - Letters O-Z


Occupational Standards - Maximum pollutant concentration levels, usually set by the Occupational Safety and Health Administration (OSHA).

o-Cresol (2-methyl-phenol)- CCL-1 EPA contaminant candidate

Odor - '3 threshold odor number'

Organic compounds - Chemicals that contain carbon (as opposed to inorganic or 'mineral' compounds). Volatile organic compounds (VOC) vaporize at room temperature and pressure and are found in many indoor sources.

Organotins – CCL-1 EPA contaminant candidate

OSHA - Acronym for the Occupational Safety and Health Administration, a part of the U.S. Department of Labor responsible for determining whether employers are providing working conditions that are safe for employees.

o-Toluidine – CCL-3 EPA contaminant candidate;origin: used in manufacture of dyes, rubber, pharmaceuticals and pesticides.

Oxamyl (Vydate) – origin: leaching/runoff from insecticide used on apples, potatoes, and tomatoes; toxicity potential: slight nervous system effects; MCL = 0.2

Oxirane, methyl- CCL-3 EPA contaminant candidate; origin: industrial chemical.

Oxydemeton-methyl – CCL-3 EPA contaminant candidate; origin: insecticide.

Oxyfluorfen – CCL-3 EPA contaminant candidate; origin: herbicide.


Parachlorometa cresol - EPA priority pollutant

parts per million (ppm) - parts of a dissolved/suspended constituent, per million parts of water or other solvent; one part per million is approximately equal to one milligram per liter (mg/L).

PCBs - poly-chlorinated biphenyls (Arochlors): 1016, 1221; 1232; 1242, 1248; 1254; 1260 -EPA priority pollutants; origin: runoff from landfills, discharge of waste chemicals; toxicity potential: cancer; MCL = 0 – 0.0005

Pentachlorophenol – EPA priority pollutant; origins: discharge from wood preserving factories; toxicity potential: cancer; MCL= 0 – 0.001

Perchlorate – CCL-1 & CCL-3 EPA contaminant candidate; origin: naturally occuring and laboratory chemical, used in fireworks, flares, explosives.

Perfluorooctane sulfonic acid (PFOS) – CCL-3 EPA contaminant candidate; origin: fire-fighting foams, few alternative chemical choices.

Perfluorooctanoic acid (PFOA) - CCL-3 EPA contaminant candidate; origin: manufacture of non-stick cookware and waterproof clothing

Permethrin – CCL-3 EPA contaminant candidate; origin: insecticide.

pH - a term used to describe the hydrogen ion activity of a water system. A solution of pH 0 to 7 is acidic; pH of 7.0 is neutral; pH 7 to 14 is alkaline; National Secondary Drinking Water Regulations suggest range for pH 6.5 - 8.5

Phenanthrene - EPA priority pollutant

Phenols - EPA priority pollutants

Picloram – origin: herbicide runoff; toxicity potential: liver issues; MCL = 0.5

Poison - Any agent capable of producing a deleterious response in a biologic system, seriously injuring function, or producing death.

Polychlorinated biphenyls (PCBs) origin: runoff from landfills, discharge of waste chemicals; toxicity potential: skin changes; thymus gland problems; immune deficiencies; reproductive or nervous system difficulties; increased risk of cancer; MCL = 0 – 0.0005

Portable filters: Portable Water Filters and Personal Filters provide clean safe drinking water on the go no matter where you are - in the office, on the road, in the car, in the RV, or backpacking through a remote jungle. A portable water purification ystem is something that any traveler can use; this methodology features proven advanced filtration technologies. < < ahref="">>

ppm - The abbreviation for "part per million".

Precipitate – can be noun – solid particles in liquid that can be removed by filtration; or verb – cause substance to settle. The term also refers to weather such as snow or rain.

Preventive Maintenance - Regular and systematic inspection, cleaning, and replacement of worn parts, materials, and systems. Preventive maintenance helps to prevent parts, material, and systems failure by ensuring that parts, materials and systems are in good working order. they are imagining symptoms.

Profenofos – CCL-3 EPA contaminant candidate; origin: insecticide.

Prometon – CCL-1 EPA contaminant candidate

2-Propene-1-ol – CCL-3 EPA contaminant candidate

Pyrene - EPA priority pollutant


QA/QC - Quality Assurance/Quality Control procedures are used to assess method performance, accuracy, and precision.

Quinoline – CCL-3 EPA contaminant candidate; origin: pharmaceutical and chemical production, anti-malarial drug, flavoring agent.


Radiologicalcontaminants - chemical elements for which the number of neutrons and protons is unbalanced, causing instability and the possible emission of ionizing radiation. Examples include: uranium, cesium, and plutonium. <> [Accessed 31 January 2015]

Radionuclides – CA Prop65 List of Chemicals; origin: radioactive isotopes of certain elements – may emit alpha-, or beta- particles, or gamma rays, called ionizing radiation. Excess exposure can cause cancer(s).

Radium (Ra) – radioactive element- Combined Ra226, Ra228. The total amount of allowed radium in drinking water is very low; origin: erosion of natural deposits; toxicity potential: cancer; MCL = 5 pCi/L

RDX (Hexahydro-1,3,5-trinitro-1,3,5-triazine) - CCL1- EPA contaminant candidate; explosive

Refrigerator filters (inline)Designed to fit any fridge, these high quality in-line filters attach to water line, remove hundreds of water contaminants and provide great tasting water. <>

Reverse Osmosis – water purification method, also called hyperfiltration; the finest filtration method known. Reverse osmosis uses a semi-permeable membrane, allowing fluid that is being purified to pass through it, while rejecting the contaminants that remain. Removes: Lead, Sulfate, Calcium, Magnesium, Sodium, Potassium, Manganese, Aluminum, Chloride, Nitrate, Fluoride Boron, Most Microorganisms, Organic Chemicals. Advantages: Removes nearly all contaminants of all types to some extent. Requires little maintenance; Disadvantages: Requires large volumes of water - as much as 3 to 5 gallons of water to recover 1 gallon of usable water. Flow rate is limited to a certain amount of gallons per day. <Reverse Osmosis Systems>

Risk Assessment - the scientific analysis of the toxic properties of a substance and its potential toxicity upon human exposure.


Salmonella entericaCCL-3,EPA contaminant candidate; origin: human or animal fecal contamination; removed by anti-microbial (anti-bacterial) filtration methods

Sanitizer - One of three groups of antimicrobial agents registered by EPA for public health uses. EPA considers an antimicrobial to be a sanitizer when it decreases, but does not necessarily eliminate, all the microorganisms on a treated surface. To be an EPA-registered sanitizer, the test results for a product must show a reduction of at least 99.9% in the number of each test microorganisms vs. the parallel control.

Scientific Method - Systematic, step-by-step approach to problem solving.

Sec-Butylbenzene – CCL-3, EPA contaminant candidate; origin: solvent

Sediment water filters - used to reduce or remove physical particles that are larger than a particular size from source water. Typical sediment filter is rated at 20 micron (ok), 10 micron (better), 5-1 micron (better yet) , or sub-micron (less than 1 micron, best but the slowest). A micron rating means that all particles larger than that will be trapped by a filter. Commonly used Sediment Water Filters are spun or pleated. Spun filters use polypropylene, cellulose or similar material that is spun to produce a filter. They are cheaper and will wear out faster. Pleated filters have more dirt holding capacity, some of them can be washed, and they last longer. <>

Selenium (Se) – element; origin: erosion of natural deposits, refinery and mine discharge; toxicity potential: ciculatory problems; MCL = 0.05

Shigella sonnei– CCL-3, EPA contaminant candidate; toxicity potential: mild gastrointestinal illness

Shower filters (also chlorine filters) - Shower filters remove chlorine as well as providing additional benefits such as reduction of soap scum, prevention of dry skin and hair, and odor removal. Also called filtered shower heads, shower filters greatly reduce and/or remove synthetic chemicals and organic compounds that can be absorbed through skin. These devices primarily use Granular Activated Carbon, and KDF methods. <

Simazineorigin: herbicide runoff; toxicity potential: blood problems; MCL = 0.004

Silver (Ag) – element; EPA secondary standards = 0.1 mg/L

Sodium (Na) – element; EPA contaminant candidate

Sodium Hypochlorite - a chlorine-releasing material used for disinfection. The strength of sodium hypochlorite solution decreases on storage.

Sorbent - A substance used for either absorption or adsorption.

Specialty Water Filters – Filters designed to eliminate specific water problems, such as contaminants commonly found in drinking water, including low or high pH level, Nitrates, Arsenic, Tannin, Sediment, Fluoride, Iron and Manganese, Hydrogen Sulfide and etc. <>

Staged Approach - A systematic, step-wise approach to investigation providing built-in decision points at which progress is assessed, and the investigation is redirected as necessary.

Sterilizer - One of three groups of antimicrobial agents registered for public health uses. EPA considers an antimicrobial to be a sterilizer when it destroys or eliminates all forms of bacteria, fungi, viruses, and their spores. Because spores are considered the most difficult form of a microorganism to destroy, EPA considers the term sporicide to be synonymous with sterilizer.

Strontium (Sr) – element; CCL-3 EPA contaminant candidate;origin:pyrotechnics, steel production

Styrene – VOC; origin: discharge from factories or leaching from landfills; toxicity potential: liver, kidney or circulatory problems; MCL = 0.1

Sulfate(SO4-2) - EPA secondary standards = 250 mg/L; EPA contaminant candidate

Surfactant - a soluble surface acting agent that reduces surface tension between particulate matter and water.


2,3,7,8-TCDD – EPA priority pollutant

TEAM Studies - Acronym for Total Exposure Assessment Methodology Studies. The goal of these long-term series of EPA-conducted studies is to determine the actual exposure of people to a substance or substances

Tebuconazole – CCL-3, EPA contaminant candidate; origin: fungicide

Tebufenozide – CCL-3, EPA contaminant candidate,origin: insecticide

Tellurium (Te) – element; CCL-3 EPA contaminant candidate

Terbacil – CCL1- EPA contaminant candidate

Terbufos (Terbufos sulfone) – CCL1 and CCL-3 – EPA contaminant candidates; origin: insecticide & breakdown product

1,1,2,2-tetrachloroethane - EPA priority pollutant; CCL-1 EPA contaminant candidate

Tetrachloroethylene - EPA priority pollutant; origin: discharge from factories and dry cleaners; toxicity potential: cancer; MCL = 0-0.005

Thallium (Tl) – element; EPA priority pollutant; origin: leaching from ore-processing, factory discharge; toxic potential: hair loss; MCL = 0.0005 – 0.002

Thidicarb – CCL-3 EPA contaminant candidate; origin: insecticide

Thiophanate-methyl – CCL-3 EPA contaminant candidate

Threshold - The lowest dose of a chemical at which a specific measurable effect is observed. Below this dose, the effect is not observed.

Toluene - EPA priority pollutant; origin: discharge from petroleum factories; toxicity potential: nervous system, kidney or liver problems; MCL = 1

Toluene diisocyanate – CCL-3 EPA contaminant candidate; origin: plastic manufacture

Total Bacteria Count (TBC) - an estimate of the number of viable units of bacteria per milliliter of water under the conditions of testing. Note that no single method, culture medium or conditions of incubation can satisgy the growth requirements of all bacteria in a water sample.

Total Coliforms (including fecal coliform and E. Coli)measurement to determine if fecal bacteria are present in water; MCL = 0

Total dissolved solids - the total weight of dissolved substances in water, including those which are capable of conducting electricity and those which are not. EPA secondary standards = 500 mg/L

Total trihalomethanes (TTHMs) - origin: byproduct of drinking water disinfection; toxicity potential: cancer; MCL = 0.080

Toxaphene - EPA priority pollutant; origin: runoff or leaching from insecticide; toxicity potential:cancer; MCL = 0 – 0.003

Toxic - Harmful, poisonous, dangerous to health; can cause or induce a variety of health risks; at worst can be fatal.

Toxicant - A poison.

Toxicity - The innate ability of a contaminant to cause injury to biological tissue.

Toxicology - The study of the adverse effects of chemicals on living organisms.

2,4,5 -TP (Silvex) –origin: runoff or leaching frominsecticide; toxicity potential: cancer; MCL = 0.5

Triazines (and degradation products) - CCL-1 EPA contaminant candidates

Tribufos – CCL-3 EPA contaminant candidate; origin: insecticide

1,2,4-Trichlorobenzene – EPA priority pollutant; origin: discharge from textile factories; toxicity potential: adrenal glands; MCL = 0.7

Trichloroethane (1,1,1-or 1,1,2-) - EPA priority pollutant; origin: factory discharge; toxicity potential: liver or circulatory issues; MCL = 0.20 for 1,1,1-tce; MCL = 0.003-0.005 for 1,1,2-tce

Trichloroethylene - EPA priority pollutant; origin: factories; toxicity potential: cancer; MCL = 0-0.005

2,4,6-trichlorophenol - CCL-1, EPA contaminant candidate

1,2,3-Trichloropropane – CCL-3 EPA contaminant candidate; origin: paint manufacture

triethylamine – CCL3- EPA contaminant candidate; origin: many industries

1,2,4-trimethylbenzene – CCL-1, EPA contaminant candidate

Triphenyltin hydroxide (TPTH) – CCL3-, EPA contaminant candidate; origin: pesticide

TSCA - Toxic Substances Control Act.

Turbidity - a cloudy appearance in water that is caused by a suspension of colloidal or particulate matter.

TVOCs - Total volatile organic compounds: these are compounds that evaporate readily and have low solubilities in water; generally man-made in origin, their presence in water is a sign of local contamination issue – such as factory run-off. Two VOCs that may be found in unpurified drinking water are Benzene and MTBE.


Ultrafiltration – similar to micro-filtration, ultra filtration systems remove impurities from water by passing it through a "screen". The screen in this case is a semi-permeable membrane that effectively separates molecules in water, allowing certain molecules to pass through it while retaining others. Removes: Sediments and extremely fine particles, microorganisms. Advantages: Highest quality water for lowest energy investment; Disadvantages: May clog. Can be expensive if large amounts of sediment exist. Does not remove dissolved particles. <>

Ultraviolet Radiation (Water Purification Method) - Low level ultraviolet light kills bacterial and viral pathogens. The amount of radiation produced is negligible, and it leaves no trace. A typical UV sterilizer looks like a stainless cylinder with water inlet on one end, and a water outlet on the other. Water passes through a chamber that has a quartz lamp which performs disinfection. Removes:
Bacteria, Viruses; Advantages: Sanitizes water; Disadvantages: Does not remove suspended particles, ions, organic chemicals, heavy metals, or ions. <Water Purification Technologies: Water Guide>

Under Sink and UnderCounter Water Filters – Point of use systems for filtering tap water in the kitchen; generally have a separate faucet. <>

Uranium (U) – element; origin: erosion of natural deposits; toxicity potential: cancer; MCL = 0

Urethane – CCL3- EPA contaminant candidate; origin: paint ingredient


Vanadium (V) – element; CCL-1 EPA contaminant candidate; origin: industrial ingredient

Vinclozolin – CCL-3, EPA contaminant candidate; orgin: fungicide

Vinyl chlorideEPA priority pollutant; MCL = 0 – 0.002; origin: factory discharge, pvc leachate; toxicity potential: cancer

Viruses – enteric; the smallest of all 'life forms' containing either RNA or DNA; toxicity potential: gastrointestinal distress (vomiting, diarrhea, cramps); MCL = 0

VOCs - See Volatile Organic Compounds.

Volatile Organic Compounds (VOCs) – compounds that evaporate readily so are 'volatile', and have low solubility in water <>. Origin: chemical industry (and some natural origins); toxicity potential: some VOC's may cause cancers. Often best removed via activated carbon filtration <> or reverse osmosis <>


Water coolers (POU) – point of use water coolers, P\plumbed directly into your cold water line and use advanced water filtration systems. <>

Water filters – A variety of filtration devices used for water purification, <>

Water filter cartridges – replacement filter system inserts for water purification are called cartridges; see Sediment Filters and/or Carbon Filters <>

Water filtration – method for purification of drinking water; varies in terms of type of contaminant requiring removal <>

Water ionizers - Water ionizers use a process that is different from standard mechanical or chemical water filtration. Along with regular water filters, ionizers rely on a process of electrolysis, or ionization. This allows water ionizers to produce water of higher (and some machines - of lower) pH levels, even much higher than normal "neutral" pH levels of 7 to 7.5 (not to be confused with skin pH, which is 5). Increasing scientific evidence suggests health benefits from drinking higher pH, or alkalinized water <>

Water pollution – has many sources, both natural and man-made. As shown in the figure at <> they range from atmospheric deposition to fertilizers and pesticides to industrial deposition, and runoff from rural and urban sources <>.

Water purification technologies - There are many methods used to remove impurities and contaminants from water. Each of the water purification technologies is best at removing one type of contaminant from water, and may not be effective at all for others. <Water Purification Technologies>

Water purification – technologies for removal of contaminants <>

Water softeners - <>

Water test kits – in-home water test kits as well as Science Fair, and laboratory water test kits. Check your drinking water with complete test kits, drinking water test kits, bacteria check tests and more. <>

WHO - Acronym for the World Health Organization.

Whole house filters – variety of systems for homes, apartments, and small businesses. Three categories include Budget water filters, Large residential home water filters, and Specialty and Well water filters. Whole House Filter Systems>

WQA - Acronym for the Water Quality Association.

Water Softening -


Xylenes (total = meta- ortho-, para-) -origin: factory discharge; toxicity potential: nervous system damage; MCL= 10


none listed


Zinc (Zn) – element; EPA secondary standards = 5 mg/L

Ziram – CCL-3, EPA contaminant candidate; origin: fungicide


[1] The majority of compounds listed are from the EPA list of drinking water contaminants <> [accessed 29 January 2015]

[2] Data for MCL values from <> (Accessed Dec 2014)

[3] Toxicity potentials for all compounds having MCL values from <> (Accessed Dec 2014)

[4] EPA contaminant candidates from lists below accessed December 2014 & January 2015

CCL-1 <>

CCL-2 <>

CCL-3 <>

CCL-4 <>

[5] EPA priority pollutants <>

Definitions: "The Priority Pollutants are a set of chemical pollutants EPA regulates, and for which EPA has published analytical test methods... The pollutant had to have been reported as found in water with a frequency of occurrence of at least 2.5%." [accessed12/31/2014]