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Home Water Testing: Glossary


acid-neutralizing filters - used to reduce water acidity. They contain some form of crushed calcite or other carbonate-based mineral. Like all filters, they must be replaced periodically.

acidity - the total amount of acid and acid-forming substances in water. Water with a pH below 7 is considered acidic.

ADEQ - Arizona Department of Environmental Quality. It administers all of Arizona's EPA programs and regulates public water systems that have at least 15 service connections or serve 25 or more people.

aeration - air stripping; a water treatment process that uses forced air to remove volatile contaminants from water.

aggressive - Aggressive water refers to low (DS) mineral or mineral-free water. It easily dissolves minerals from pipes, including scale deposits and metal pipes. Aggressive water is also corrosive. Only plastic piping and containers are recommended to transport mineral-free water.

alkalinity - the total amount of bicarbonate and carbonate ions present in water, reported in mg/L of calcium carbonate (CaCO3). Water alkalinity helps protect against abrupt pH changes, limiting its range to between 7.5 and 8.5. Alkalinity and hardness also control pipe scale formation. There is no drinking water standard for alkalinity.

anion - a negatively charged ion. Examples: chloride and sulfate.

benzene - a volatile organic chemical used as an industrial solvent and a major component of gasoline.

BDL - below detection limits; a term used in laboratory reports to indicate non-detected contaminants.

cation - a positively charged ion. Examples are sodium and calcium.

coliform bacteria - Routine water testing for coliform bacteria is used as an indicator of animal or human fecal contamination. Positive results may indicate the presence of pathogens such as bacteria, viruses, and parasites (present in surface waters only) in the water.

colloidal - Colloidal materials are very fine particles like clay minerals that stay in suspension in water for very long periods and make water cloudy.

contaminant - a foreign substance (such as chemical, microbial, and plant or mineral particulate matter) found in water. Contaminants may or may not be harmful to human health.

corrosion - Corrosion in metal pipes occurs spontaneously by the presence of oxygen in water. Pipe corrosion is accelerated by corrosive water, high TDS, low (acidic) pH, low alkalinity, and high concentrations of chloride and sulfate ions. Iron metal pipes corrode the most, followed by zinc (galvanized iron) and copper metal pipes. Modern plastic pipes used in home construction do not corrode.

detection limit - the value below which measurement or detection of a chemical is not possible. Laboratories report pollutants not detected as being below detection limits.

disinfection - Disinfection of potable water to kill or inactivate pathogens is commonly done by public water systems with chlorine chemicals and ozone (O3) gas. These include chlorine gas (most common), chloramines, and chlorine dioxide gas. Residual chlorine is added to prevent pathogen recontamination, (usually 0.1 to 0.4 mg/L chlorine or chloramines is needed in potable water that is delivered through the distribution system to homes). The use of these chemicals at home is not recommended or allowed. However, safe disinfection systems are available for home use.

disinfection byproducts - organic chemicals such as chloroform that can form during water disinfection using chlorine-based chemicals. Their concentrations are regulated under the NPDWS.

dissolution - Dissolution of minerals in water means that water separates and surrounds each mineral component (atoms or molecules) and holds them in solution.

endocrine disruptors - a class of water pollutants that affect the human endocrine system. These include pesticides and emerging contaminants like pharmaceuticals and surfactants.

flash pasteurization - treatment that uses high termperature for a short time (160 degrees F for 15 seconds) to disinfect water.

flocculation - a treatment process usually done before sedimentation. It involves the addition of flocculants and coagulants (chemicals) to form large particles (aggregates) from the fine solids suspended in water so they can settle quickly or be filtered faster.

groundwater - water stored below the Earth's surface inside the pores (void space) of geologic materials called aquifers. Groundwater may be fresh or saline.

hardness - Hardness is the total amount of calcium and magnesium ions found in water. Hard water affects detergents (by limiting suds formation). Scale formation in pipes is accelerated with hard water. Some scale formation is desirable to protect pipes from corrosion. Excessive scaling clogs pipes and can shorten the life of home appliances. There is no drinking water standard for hardness, and it is usually reported in mg/L of calcite.

hydrogen sulfide - a toxic, rotten egg-smelling gas that occurs naturally in aquifers and sediments.

ions - chemicals (i.e., atoms or molecules) with positive charges (cations) or negative charges (anions). common ions found in fresh water include: sodium (Na+), chloride (Cl-), sulfate (SO4-), carbonates (HCO3-, CO3-) and nitrate (NO3-).

MCL - maximum contaminant level or maximum concentration of a contaminant allowed in drinking water.

microorganism - an organic carbon-based organism that are not visible with the naked eye; this includes bacteria and viruses.

minerals - natural crystalline materials found in rocks (such as granite, marble, and sandstone) and soils (as sand silt and clays). Minerals are composed of chemical elements like oxygen, silicon, aluminum, iron, and many other elements.

NOM - natural organic matter (mostly from plant and animal tissue decay) present most often in surface water sources and contaminated groundwater. Colored water usually has high concentrations of NOM.

NPDWS - National Primary Drinking Water Standards - set by the Environmental Protection Agency, based on current scientific data, availability of technologies for the detection and removal of contaminants, the occurrence or extent of contamination of a chemical in the environment, the level of human exposure, potential health effects, and the economic cost of water treatment. Public water systems may not provide water to their customers that exceeds the MCL of any listed contaminant. The most current list is available on the EPA website.

NSDWS - National Secondary Drinking Water Standards - set by the Environmental Protection Agency as guidelines for water utilities regarding aesthetic (taste and odor), cosmetic (skin and tooth discoloration), and technical (water delivery) standards. The current list of guidelines is available on the EPA website.

oxidizing filters - These filters can reduce both ferric (yellow cloudy) and ferrous (green clear) iron, manganese, and hydrogen sulfide gas from well waters. Note that oxidizing filters require periodic backwashing to flush particulates and restore flow and regeneration with potassium permanganate to restore oxidizing properties.

ozonation - the use of ozone gas to disinfect water.

particle filtration - a process that removes particulates from water, including soil minerals (such as sand, silt, and clay), asbestos, sediments, plant matter, and parasitic pathogens.

pathogen - Pathogens or germs are microorganisms that produce diseases. Common pathogens regulated in drinking water include bacteria (such as Salmonella) and protozoan parasites (such as Giardia and Cryptosporidium). Other pathogens (such as enteric [intestinal] viruses) are controlled in drinking water and associated with turbidity. Note that water sources are commonly tested for the possible presence of pathogens by measuring total coliform bacteria.

POE - point-of-entry; refers to a device that treats all or most of the water entering a home.

pollutant - an unwanted contaminant or pathogen of anthropogenic origin that can be found in water, soil, and air. Pollutants are chemicals and organisms that have been associated with adverse environmental and health effects.

POU - point-of-use; refers to a device that treats water at a particular tap source.

ppm - parts per million: one gram (gr) of a chemical lin a million grams of water is similar to 1 gr/metric ton of water or 1 mg/L of water.

precipitation - in reference to a mineral, this is the opposite of dissolution. That is, the mineral crystallizes and forms a solid again.

purified water - a vague and misused term, subject to misinterpretation. Usually implies that levels of contaminants (salts, metals, etc.) have been reduced but not completely eliminated. The NSF website defines it as "A type of water which has been produced by distillation, deionization, reverse osmosis, or other suitable processes. Purified water may also be referred to as 'demineralized water.' It meets the definition of 'purified water' in the United State Pharmacopoeia."

radon gas - Radon is a colorless and odorless radioactive gas that may be present in groundwater sources that come into contact with uranium-rich minerals.

salinity - a measure of the quantity of dissolved salts (minerals) in water. Saline water exceeds 1000 mg/L TDS or salts. This means that it contains 0.1% total salts or ~2/3 teaspoons per gallon. Moderate and highly saline waters (such as seawater) contain from 3,000 to 35,000 mg/L of salts (0.3 to 3.5% total salts). Moderately saline water is often referred to as brackish or briny.

scale - hard residues that coat the inside of water pipes and appliances and are the result of the precipitation of minerals composed of calcium and magnesium carbonates. Hot water helps form scale.

sedimentation - Sedimentation, or clarification, is a particle filtration process that requires special chemicals (called flocculants and coagulants) and water holding tanks. This filtration process is complex and expensive, and is used to treat large volumes of surface water high in sediments and soil particles like silt and clay.

shock chlorination - the circulation of a strong chlorine-based (bleach) solution through the well casing and house plumbing

soft water - water that contains mostly sodium or potassium ions. Hard water can be "softened" by replacing calcium and magnesium for sodium or potassium ions using a water softener system. Water naturally low in TDS is also called soft water.

TCE - trichloroethylene, the volatile industrial solvent that is notorious for industrial groundwater contamination.

TDS - total dissolved solids - TDS values are in milligrams per liter (mg/L) or parts per million (ppm). For example, a TDS of 500 mg/L (or 500 ppm) is equal to 0.5 gr/L or ~1/3 teaspoon per gallon of water. See also discussion of TDS in Arizona waters.

turbidity - a measure of the amount of suspended solids (particles) in water.

VOCs - volatile organic compounds: A class of liquid organic compounds that volatize (vaporize/evaporate) at room temperature. VOCs are made as secondary petrochemicals, and include light alcohols, acetone, trichloroethylene, percholoroethylene, dichloroethylene, benzene, vinyl chloride, toluene, and methylene chloride. These potentially toxic chemicals are used as solvents, degreasers, paints, thinners, and fuels. Because of their volatile nature, they readily evaporate into the air, increasing the potential exposure to humans. Due to their low water solubility, environmental persistence, and widespread industrial use, they are commonly found in soil and groundwater.

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