Glossary of Terms

Glossary of Terms - M

A :B :C :D :E :F :G :H :I :J :K :L :M :N :O :P :Q :R :S :T :U :V :W :X :Y :Z :

SEE alkalinity tests
A special grade of ion exchange resins which have large pores and a higher resistance to oxidation and organic fouling.

They were developed to provide increased surface area for reactions with organic matter with large molecular weights.

Macroporous resins are manufactured with a third ingredient that is soluble in the styrene and divinylbenzene monomers but becomes insoluble in the polymer structure as it is formed. The third ingredient is then removed from the resin structure by a solvent leaving a resin bead that has both a continuous resin phase and a continuous pore phase, resulting in considerable net porosity and internal surface area.

Macroporous resins, which are produced in both anion and cation versions, contain higher levels (12% or more) of divinylbenzene cross-linking, which reduces the swelling of the polymer resin in water.

Also called macroreticular resin.

SEE macroporous resin
Organisms big enough to be seen by the eye without the aid of a microscope.
Magnesium oxide (MgO) that has been specially processed.

Magnesia water treatment can be used for pH modification of water.

One of the elements (Mg) making up the earth's crust, the compounds of which when dissolved in water make the water hard. The presence of magnesium in water is a factor contributing to the formation of scale and insoluble soap curds.
(Fe3O4) A black magnetic oxide of iron that is extremely dense and used as a coagulant and filter medium in water treatment.

Magnetite is readily recognized by its strong attraction to magnets.

Also called lodestone.

Treated water added to the water loop of a boiler circuit or cooling tower to make up for the water lost by steam leaks or evaporation.
Very dangerous or virulent, causing or likely to cause death.
All radionuclides emitting beta particles and/or photons listed in Maximum Permissible Body Burdens and Maximum Permissible Concentration of Radionuclides in Air or Water for Occupation Exposure, NBS Handbook 69, except the daughter products of thorium-232, uranium-235, and uranium-238.
Methods of nonpoint source pollution control that are derived from managerial decisions, such as changes in application times or rates for agrochemicals.
An element (Mn) sometimes found dissolved in groundwater, usually with dissolved iron but in lower concentrations. Causes black stains and other problems similar to iron.
An oxidizing catalyst medium used to remove iron and manganese.

The manganese is sacrificial.

(MnO2) A dark brown or gray-black insoluble compound found in nature as pyrolusite, made synthetically, and used as an oxidizing agent in water treatment and as a starting material for permanganate compounds such as potassium permanganate.
Greensand which has been processed to incorporate in it pores and on its surface the higher oxides of manganee. The product has a mild oxidizing power and is often used in the oxidation and precipitation of iron, manganese and/or hydrogen sulfide, and their removal from water.
Synthetic gel zeolite which has been processed in the same manner as manganese greensand and used for similar purposes.
A form of manganese ore, consisting of manganic hydroxide, which is used in filters designed to reduce iron, manganese, and/or hydrogen sulfide and requires a very high backwash rate because of its very high density (specific gravity 4.3).

Similar to pyrolusite.

A large pipe to which a series of smaller pipes are connected.

Also called a header.

An instrument for measuring pressure.

Usually, a manometer is a glass tube filled with a liquid that is used to measure the difference in pressure across a flow-measuring device such as an orifice or Venturi meter.

The instrument used to measure blood pressure is a type of manometer.

Maximum amount of exposure producing no measurable effect in animals (or studied humans) divided by the actual amount of human exposure in a population.
An early chemical name for salt, partly because of its source.
The movement of molecules of a substance to and across an interface from one phase to another. For example, the amount (mass) of ozone that transfers from air, across the air-water interface and into water; or the amount of organic material that transfers from water to a solid adsorption surface.

The rate and amount of mass transfer can be increased by:

1. enlarging the interface boundary by increasing the area of the interface or by rapid renewal or clearance of the interface; 2. increasing the concentration difference (which is the driving force) across the interface boundary, and/or; 3. increasing the length of time (contact time) the interface boundary exists.

The region in a treatment unit where mass transfer is taking place.

For example, the region of an adsorption column in which adsorption is taking place.

Model used during risk assessment to perform extrapolations.
SEE drinking water standards
SEE drinking water standards
The maximum concentration of total trihalomethanes produced in a given water containing a disinfectant residual, after seven days at 25 degrees C or above.
These substances are used in surfactants or detergents.
Abbreviation for "Maximum Contaminant Level", the maximum allowable concentration of a contaminant in water as established in the U.S. EPA Drinking Water Regulations.
maximum contaminant level.
maximum contaminant level goal.
A characteristic or component part that is sensed and quantified (reduced to a reading of some kind) by a primary element or sensor.
A filter primarily designed for the removal of suspended solid particles as opposed to filters with additional capabilities.
A flexible device that joins pipes or fittings together by the use of lugs and bolts.
The selected materials in a filter that form the barrier to the passage of certain suspended solids or dissolved molecules.
Singular form of media.
A public water system that serves greater than 3,300 and less than or equal to 50,000 persons.
Abbreviation for megohm. Meg means one million.
1. A prefix meaning large; 2. A million of; or multiplied by one million.

2. a million of, or multiplied by one million.

A unit of electrical resistance equal to one million ohms.
A thin sheet or surface film, either natural or man-made, of microporous structure that performs as an efficient filter of particles down to the size range of chemical molecules and ions.

Such membranes are termed "semipermeable" because some substances will pass through but others will not. Usually small ions, water, solvents, gases, and other very small molecules can pass through a membrane, but other ions and macromolecules such as proteins and colloids are barred from passage.

Man-made (synthetic) membranes are highly engineered polymer films about 100 angstroms thick and with controlled distributions of pores ranging from 5 to 5,000 angstroms in diameter.

Membranes are used in reverse osmosis, electrodialysis, nanofiltration, ultrafiltration, and as pleated final filter cartridges in water treatment.

SEE ALSO cellulose acetate (CA); cellulose triacetate (CTA); charged polysulfone membrane.

A laboratory analytical technique for the quantitative and qualitative analysis of bacterial or particulate matter in a water sample.

Upon filtering through a membrane of specified pore size (e.g., 0.45 micron), bacteria and particles of larger size are separated from the water sample and are retained on the filter. Then by incubation with a suitable nutrient and temperature, the captured bacteria will grow to visible colonies that can be counted; or by careful weighing, the amount of suspended particulate solids can be determined in the water sample.

SEE nanofiltration
SEE ion exchange membrane
The curved top of a column of liquid (water, oil, mercury) in a small tube.

When the liquid wets the sides of the container (as with water), the curve forms a valley. When the confining sides are not wetted (as with mercury), the curve forms a hill or upward bulge.

The ultraviolet light given off as the result of an electron flow through an ionized mercury vapor between electrodes in an ultraviolet lamp. The mercury vapor UV wavelength, which is most destructive to microorganisms in water, is 254 nanometers.
Mesh is the number of openings in a square inch of a screen or sieve.

It is equal to the square of the number of strands of metal or plastic screening per lineal inch. Ion exchange and filter media are graded by U.S. mesh or screen sizes according to the percent of the medium's particles that will pass through or be retained on certain mesh screens.

Standard U.S. mesh screen #16 equates to a 1.19 millimeter particle diameter; mesh size #40 is 0.42 millimeters. Therefore, media rated as 95 percent -16+40 U.S. mesh would have 95 percent or more of the media particles with sizes between 0.42 and 1.19 mm in diameter.

Reservoirs and lakes which contain moderate quantities of nutrients and are moderately productive in terms of aquatic animal and plant life.
The sum of the chemical reactions occurring within a cell or a whole organism; includes the energy-releasing breakdown of molecules (catabolism) and the synthesis of new molecules (anabolism).
Any product of metabolism, especially a transformed chemical.
The middle layer in a thermally stratified lake or reservoir. In this layer, there is a rapid decrease in temperatures with depth.

Also called the thermocline.

Pertaining to the transfer of disease from one organ or part to another not directly connected with it.
A colorless, odorless, flammable gas consisting of the hydrocarbon (CH4) and resulting from the decay of vegetable matter or manure due to the action of anaerobic bacteria in swampy land, closed landfills, or sewage disposal plants.

Methane is also known as biogas and it is called swamp gas when produced in marshy land. Coal miners know methane as one of the main components of fire-damp and also of coal-gas.

Methane dissolved in water gives the water a milky cast, and since it is flammable, methane must be safely aerated and vented to the atmosphere during removal.

A serious condition, found mostly in young infants under six months of age (or newborn animals), in which the oxygen-carrying capacity of the blood is reduced as a result of a reaction with nitrite (NO2-), which changes the healthy hemoglobin to an inactive methemoglobin form.

As a result of the higher pH conditions in the gastrointestinal tract of infants and newborn animals, nitrate (NO3-), which is consumed in food or water, can be transformed into nitrite more readily than would occur with adults.

A pesticide which causes adverse health effects in domestic water supplies and is also toxic to freshwater and marine aquatic life.

The chemical name for methoxychlor is 2,2-bis (p-methoxyphenol)-1,1,1-trichloroethane.

An acid-base indicator that turns red in a solution below three on the pH scale and yellow between pH of 4.4 and 7.0.

See Also: Base Alkali Alkalinity Alkalinity Tests Hydroxide Alkalinity Detergent Methyl Orange Alkalinity Phenolphthalein Phosphate Soap Alkalinity Methyl Orange Alkalinity Phenolphthalein

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 a pH level of 4.5, as indicated by the change in color of methyl orange from orange to pink.

Methyl orange alkalinity is expressed as milligrams per liter equivalent calcium carbonate.

See Also: Base Alkali Alkalinity Alkalinity Tests Hydroxide Alkalinity Detergent Methyl Orange Phenolphthalein Phosphate Soap Alkalinity Methyl Orange Phenolphthalein

Since MTBE was incorporated in the mid-1980s into gasoline mixtures as an antiknock replacement for aromatics and as an "oxygenator" to reduce carbon monoxide emissions, it has increasingly appeared in groundwater due to spills of reformulated gasoline and leaking underground storage tanks at gasoline stations. It is highly water soluble and its appearance typically marks the leading front of a contamination plume. The molecular weight of MTBE (C5H12O) is 88.15.

In terms of noncarcinogenic effects, it has low oral toxicity, but at the gasoline pump and in the automobile, symptoms such as airway and eye irritation have been reported. In water, MTBE has a noticeable odor at 20 to 40 µg/L (U.S. Environmental Protection Agency, 1997). Though MTBE is not mutagenic/genotoxic, exposure to high levels by inhalation (8000 ppm) or by ingestion (1000 mg/kg) was associated with the development of lymphoma and leukemia, as well as liver, renal, and testicular cancers in rodents (Burleigh-Flayer et al., 1992; Belpoggi et al., 1995).

The relevance of these cancers to human health is not clear, but "weight of evidence suggests that MTBE is an animal carcinogen." "Concentrations in the range of 20 to 40 µg/L are about 20,000 to 100,000 (or more) times lower than the range of exposure levels in which cancer or non-cancer effects were observed in rodent tests." (U.S. Environmental Protection Agency, 1997). Thus, the USEPA says "protection of the water source from unpleasant taste and odor will also protect consumers from potential (MTBE) health effects."

MTBE is adsorbed onto activated carbon similar to chloroform, but with a use rate of 2-3 times that of chloroform, i.e., the life of the activated carbon may be only 1/2 to 1/3 of that for chloroform when MTBE will begin to break through. For concentrations of MTBE greater than 100 µg/L or parts per billion, pretreatment with an atmospheric air stripping system with repressurization is recommended prior to activated carbon adsorption.

The abbreviation for milligrams per liter.
(Backward spelling of ohm)

A unit of conductance equal to the reciprocal of the ohm. Also called siemens.

See Also: Microsiemens

The activity and growth of microorganisms such as bacteria, algae, diatoms, plankton, and fungi.
Similar to biocide but does not necessarily kill macroscopic and multicelled organisms.

See Also: Sporicide Sterilize

Water that (1) is known to contain disease-causing bacteria, viruses, protozoa or other disease-causing microbiological agents, or (2) shows a positive test for an indicator orgaism such as coliform, fecal coliform, or E. coli bacteria, or (3) is determined unsafe by an appropriate health or regulatory agency.
The separation or removal of particulates of more than 0.02 mm or 10.0 mm size from liquids.
One-millionth of a gram (3.5 X 10E-8 oz. = 0.000000035 oz.).
One microgram of a substance dissolved in each liter of water.

This unit is equal to parts per billion (ppb) since one liter of water is equal in weight to one billion micrograms.

One millionth of an ohm.

The unit of measurement for testing the electrical resistance of water to determine its purity. The closer water comes to absolute purity, the greater its resistance to conducting an electric current.

Absolutely pure water has a specific resistance over 18 million ohms across one centimeter at a temperature of 78 degrees F (25 degrees C).

A linear measure equal to one millionth of a meter, or .00003937 inch. The symbol for the micron is the Greek letter "m".
The term applied to a filter or filter medium to indicate the particle size above which all suspended solids will be removed throughout the rated capacity. As used in industry standards, this is an "absolute", not "nominal" rating.
A living organism invisible or barely visible to the naked eye and generally observable only through a microscope. Also called a microbe. Microorganisms are generally considered to include algae, bacteria, fungi, protozoa, and viruses.

Microorganisms are generally considered to include algae, bacteria, fungi, protozoa, and viruses.

Ion exchange resin with low porosity, usually polystyrene cross-linked typically with about three percent divinylbenzene.

The lower cross-linking means microporous resins also have less strength and less resistance to degradation, swelling, and mushing.

One millionth of a watt.
A unit of measurement of intensity and retention or contact time in the operation of ultraviolet systems.
The point at or near the middle of a scale or set of experimental results data in scientific analyses.
The lateral (horizontal) distribution system located at the interface where stratified anion and cation beds in a mixed bed ion exchange deionizer meet.
One thousandth of an inch
The prefix used with units of measure to indicate one thousandth of the unit. Example: a milliliter is one thousandth of a liter.
One-thousandth of a gram (3.5 X 10-5 oz. = 0.000035 oz.).
A unit concentration of matter used in reporting the results of water and wastewater analyses. In dilute water solutions, it is practically equal to the part per million, but varies from the ppm in concentrated solutions such as brine. As most analyses are performed on measured volumes of water, the mg/L is a more accurate expression of the concentration and is the preferred unit of measure.
A unit of volume measure equal to 1/1000 liter (or one cubic centimeter); the volume occupied by one gram of pure water at 4 degrees C at 760 mm of pressure or standard atmospheric pressure.
A unit of length equal to one thousandth of a micron often used to express the wavelength of colors of visible light in colorimetric analytical procedures. The symbol for the millimicron is "mm".
A measure of water flow.
A term applied to inorganic substances, such as rocks and similar matter found in the earth strata, as opposed to organic substances such as plant and animal matter. Minerals normally have definite chemical composition and crystal structure. The term also is applied to matter derived from minerals, such as the inorganic ions found in water. The term has been incorrectly applied to ion exchangers, even though most of the modern materials are organic ion exchange resins.
Acidity due to the presence of inorganic acids such as hydrochloric, sulfuric, and nitric acid, as opposed to acidity due to carbonic acid or organic acids.
A chemical compound formed by the combination of a mineral acid and a base.

Minerals from dissolved rock exist in water in the form of dissolved mineral salts. An excess of mineral salts can give water a disagreeable taste or even be harmful to human health.

Water which is naturally or artificially impregnated with mineral salts or gases (carbon dioxide).

The term is also used to designate bottled water that contains no less than 250 ppm total dissolved solids (TDS) and originates from a protected groundwater source.

Water produced by either distillation or deionization.

This term is sometimes found on labels of bottled water as a substitute term for distilled or deionized water.

Another name for mined rock salt.
Able to be mixed together or dissolved into each other to produce a homogenous substance.
The intermix of two or more filter or ion exchange products in the same vessel during a service run.

The most common use is in ion exchange systems having a 40/60 percent cation to anion resin bed such as that for a deionization polisher unit. In filtration, there may be an intermix of two or more media in a single tank with each stratified into separate layers.

See Also: Dose

A mixture of activated sludge and waters containing organic matter undergoing activated sludge treatment in the aeration tank of a waste water treatment system.
The use of two or more media products in a single filtration loose media bed where the products are intermixed--rather than in stratified layers.

For example, the intermix use of calcite and magnesia in pH modification.

Use of mathematical equations to simulate and predict real events and processes.
The membrane element and its housing in a reverse osmosis unit.
A molar solution consists of one gram molecular weight of a compound dissolved in enough water to make one liter of solution.

A gram molecular weight is the molecular weight of a compound in grams. For example, the molecular weight of sulfuric acid (H2SO4) is 98. A one M solution of sulfuric acid would consist of 98 grams of H2SO4 dissolved in enough distilled water to make one liter of solution.

The molecular weight of a chemical compound expressed in grams.
The molecular weight of a compound in grams is the sum of the atomic weights of the elements in the compound.

For example, the molecular weight of sulfuric acid (H2SO) in grams is 98.

The simplest combination of atoms that will form a specific chemical compound; the smallest particle of a substance which will still retain the essential composition and properties of that substance and which can be broken down only into atoms and simpler substances.
Trade name for a series of corrosion resistant alloys made of nickel and copper.
Measuring concentrations of substances in environmental media or in human or other biological tissues.
An indicator light, electrically or electronically activated, which is positioned in the effluent (product water) stream of a piece of water treatment equipment (deionizer, distiller, reverse osmosis unit, or electrodialysis unit) to detect and signal changes in the water quality which might indicate malfunction of the equipment.

Some lights remain on while water quality is within the desired range and go out if the quality of the water falls into the unacceptable range. Other sensors use red and green light signals.

See Also: Sensor Sensor Sensor

Wells used to collect groundwater samples for analysis to determine the amount, type, and spread of contaminants in groundwater.
A product trade name for a fully regenerated ion exchange mixed bed (strong acid cation H+ and strong base anion OH-).
Consisting of radiation or rays, such as ultraviolet rays, of a single wave length or of a very small range of wave lengths.
A molecule of low molecular weight capable of reacting with identical or different monomers to form polymers.
Lakes and reservoirs which are relatively deep, do not freeze over during the winter months, and undergo a single stratification and mixing cycle during the year.

These lakes and reservoirs usually become destratified during the mixing cycle, usually in the fall of the year.

Having a valence of one, such as the cuprous (copper) ion, Cu+.

Also called univalent.

The term used to indicate the number of organisms which, according to statistical theory, would be most likely to produce the results observed in certain bacteriological tests: usually expressed as a number per 100ml of water.
1. Residual brines, containing chiefly calcium and magnesium chlorides, obtained after the salt has been crystallized and removed from solution. The term "mother liquor" is widely used when salt is produced by use of vacuum pan and gainer operations. In the solar salt evaporation process, the term "bitterns" is often used in place of the term "mother liquor".

2.A solution substantially freed from undissolved matter by a solid/liquid separation process, such as filtration or decanting.

Capable of self-propelled movement.

A term that is sometimes used to distinguish between certain types of organisms found in water.

The water flow rate (e.g., gallons per minute) through a venturi injector that provides the suction at the injection port of the injector to induce the flow of another liquid (such as a regenerant) or gas (such as air or ozone) into the flow of water.

See Also: Eductor

The ratio of energy delivered by a motor to the energy supplied to it during a fixed period or cycle.

Motor efficiency ratings will vary depending upon motor manufacturer and usually will range from 88.9 to 90.0 percent.

Most probable number.
Maximum tolerated dose, the dose that an animal species can tolerate for a major portion of its lifetime without significant impairment or toxic effect other than carcinogenicity.
Material that is approximately round in shape and varies from pea-sized up to two or more inches in diameter.

This material forms in filters and gradually increases in size when not removed by the backwashing process.

Any substance spread or allowed to remain on the soil surface to conserve soil moisture and shield soil particles from the erosive forces of raindrops and runoff.
A single filter or ion exchange medium used to treat water for the removal of more than one constituent. Examples are activated carbon for chlorine removal and sediment filtration, calcite for pH modification and filtering of precipitated iron, or cation resin for reduction of dissolved iron as well as hardness removal.
A media bed in which more than one filter or ion exchange medium is used in the same vessel, with each medium retaining its stratified position as a layer - even after specified backwashing is performed - due to differences in media densities.
Use of land for more than one purpose; i.e., grazing of livestock, wildlife production, recreation, watershed, and timber production.

Could also apply to use of bodies of water for recreational purposes, fishing, and water supply.

A master control valve used in a filter, deionizer, or water softener to control all the necessary steps in the regeneration process or the backwashing and rinse down of filters.

Term originated by the Permutit Company of New York.

Mathematical model based on the multistage theory of the carcinogenic process, which yields risk estimates either equal to or less than the one-hit model.
A pump that has more than one impeller.

A single-stage pump has one impeller.

Wastes (mostly liquid) originating from a community; may be composed of domestic waste waters and/or industrial waste waters.
Mushing of water softener salt occurs when salt pellets break down into their crystallized form.

If a water softener brine tank is caked with salt or if a ridge of salt appears in the unit, the salt has either mushed or bridged, or both. Both salt mushing and salt bridging conditions prevent proper circulation of salt in the unit and require that the brine system be cleaned.

See Also: Salt Bridging

An agent that causes a permanent genetic change in a cell other than that which occurs during a normal genetic recombination.
The capacity of a chemical or physical agent to cause permanent alteration of the genetic material within living cell.