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M

M³ Cubic meter; a metric measure of volume, about 35.3 cubic feet or 1.3 cubic yards.

MACROFLORA All living entities within a system that are larger than bacteria, including algae clumps and large protozoa.

MACROGRAPH Photographic reproduction not magnified more than ten times.

MACRORETICULAR A term used to describe resins that have a rigid polymer porous network in which there exists a pore structure even after drying. Their pores are larger than atomic distances and are not part of the gel structure.

MAGMA Soft mass of solids in the lime slurry tank.

MAGNESIUM: Mg (chemical symbol) An element or ion present in most water supplies by usually in lesser quantities than calcium, both of which cause hardness.

MAGNESIUM HARDNESS Water hardness due to soluble magnesium in a water.

MAGNESIUM SALTS Any simple magnesium compounds.

MAGNETITE The common form of iron oxide found in a boiler as a thin (0.2 - 0.7 mils), dense and protective layer on the boiler tube wall or as unwanted porous deposits due to iron intrusion from the preboiler system.

MAINTENANCE DOSE A maintenance chemical dose is the chemical dosage which must constantly be added to a system each time bleedoff occurs in order to maintain a constant chemical concentration.

MAKEDOWN Diluting a polymer with influent plant water.

MAKEDOWN TANK A tank in which a polymer is mixed with water.

MAKEUP Replacement of water lost to the system by process and system leaks, drift, evaporation, and blowdown.

MAKEUP WATER Water that replaces plant water lost through evaporation, leaks and other causes.

MALLEABILITY Capability of forming a metal by rolling or hammering. The more malleable the metals are, the more easily they can be hammered or rolled into a thin sheet.

MANIFOLD The main header pipe in a Crossflow Tower.

MANGANESE GREENSAND A naturally occurring zeolite mineral with ion exchange properties.

MANGANESE: Mn (chemical symbol) Has almost the same properties as iron in water but is usually present in lesser quantities.

MANOMETER Instrument for measuring pressure of gases and vapors. Gas pressure is balanced against column of liquid such as mercury, in U-shaped tube.

MANUAL BLOWDOWN Intermittent manual blowdown is designed to remove any sludge formed in the boiler water and maintains boiler water balances within design limits.

MARTENSITE Unstable constituent in quenched steel, formed only during rapid cooling to below a certain temperature. The structure is characterized by its acicular appearance on a polished and etched specimen. Martensite is the hardest of the transformation products of austenite. Quenched structures in ruptured boiler tubes are occasionally martensitic.

MATRIX Base metal in which another constituent is present.

MECHANICAL DRAFT Design whereby airflow is constantly being generated by fans or rotor, either induced by the fans on top or forced draft by impellers located at bottom of air inlet.

MECHANICAL DRAFT COOLING TOWER A cooling system that uses fans to move air through a tower.

MECHANICAL EQUIPMENT Refers to air moving devices only. Induced draft normally consists of fan blades mounted on a hub attached to vertical shaft of gear reducer box with a flexible coupling fixed to the horizontal (or input shaft of gear box) and transmission shaft with another flexible coupling joining shaft to motor shaft. Forced draft towers normally are belt driven from motor pulling to fan sheave which is keyed to Rotor Fan (or squirrel cage) shaft. Some fan designs are direct coupled to motor.

MECHANICAL EQUIPMENT SUPPORT Members which comprise the primary support for the fan drive assembly.

MECHANICAL EXHAUST A powered device, such as a motor-driven fan or air/stream venturi tube, for exhausting contaminants from a work place, vessel, or enclosure.

MEDIA Physical materials used for filtering.

MELTING POINT For a given pressure, the temperature at which the solid and liquid phases of a substance are in equilibrium.

MEMBRANE A barrier, usually thin, that permits the passage only of particles up to a certain size or of special nature.

MERKEL’S THEORY The total heat theory which has been almost universally adopted to calculations of tower performance. All heat transfer taking place at any position in the cooling tower is proportional to the difference between the total heat of the air at that point in the tower and a total of air saturated at the temperature of the water at that point in the tower.

MESENTERIES The tissue lining the body cavities and from which the organs are suspended.

METABOLIZE To convert food, such as soluble organic matter, to cellular matter and gaseous by-products by a biological process.

METALLOGRAPHY Branch of metallurgy dealing with the constitution and structure of solid metals and alloys.

METER Metric unit of linear measurement equal to 39.37 inches.

METHYL CHLORIDE (R-40) A chemical once commonly used as a refrigerant. The chemical formula is CH₃Cl. Cylinder color code is orange. The boiling point at atmospheric pressure is - 10.4 F.

METHYL ORANGE An indicator dye used to determine total alkalinity. Color change at end point (pH 4.3) from yellow to salmon pink when the solution is acid.

METHYL PURPLE An indicator dye used to determine total alkalinity. End point color change is from green to purple (acid) at (pH 4.3). Equivalent in purpose to Methyl Orange but with more easily discerned color change.

METRIC SYSTEM A decimal system of measures and weights, based on the meter and gram. Length of one meter, 39.37. in.

mg Milligram; a metric unit of weight. There are 1,000 milligrams in one gram (g) of a substance.

mg/kg The weight in milligrams of a substance per kilogram of body weight. 50 mg/kg is equivalent to approximately 1 teaspoon swallowed by a 150-pound adult.

mg/l Milligrams per liter; approximately equal parts per million; a term used to indicate concentration of materials in water.

mg/m³ The weight in milligrams of a substance per cubic meter in air. 500 mg/m³ is equivalent to approximately 1 tablespoon of dust in the air of a room which measures 9x12 feet with an 8-foot ceiling.

MGD Million gallons per day.

MICROBIALS The total population of all living organisms in a system, including bacteria, algae and protozoa.

MICROBIOCIDE A toxic chemical used to control the population of living microscopic organisms.

MICROBIOLOGICAL Referring to biological organisms of microscopic size.

MICROBIOLOGICALLY INDUCED CORROSION (MIC) Bacteria growth on a metal surface that causes corrosion. Metal becomes weakened at the site of the bacterial growth and becomes corroded.

MICROMHO A basic unit of electrical conductance (.001 mho/cm).

MICRON Unit of length in metric system; a thousandth part of one millimeter.

MICROORGANISMS Tiny living organisms which usually require the use of a microscope for detection.

MICROPROCESSOR The central processor of a computer fabricated as an integrated circuit, capable of semi-intelligent functions based on instructions in a software program.

MICROPROCESSOR CONTROL Chemical feed is based on a combination of timer and demand type devices.

MICROPROCESSOR CONTROL SYSTEM The Chemonitor ALPHA Control System provides flexibility in feeding different treatment solutions from one control center.

MICROSEIMEN A basic unit of electical conductance. Same as micromho.

MICROSTRAINER/MICROSCREEN A mechanical filter consisting of a cylindrical surface of metal filter fabric with openings of 20-60 micrometers in size.

MICROSTRUCTURE Crystalline structure of polished and etched metal and alloy specimens as revealed by a microscope.

MIL A measure of thickness or depth equal to 0.001 inch. Terms used in water treatment to express of metal loss due to corrosion.

MILS PER YEAR Corrosion rate of a metal corresponding to thousandths of an inch penetration per year.

MILL SCALE A heavy oxide on metal, usually iron or steel, resulting from its heat treatment.

MILLI A combining form denoting one thousandth; example, millivolt, one thousandth of a volt.

MILLIGRAMS PER LITER The number of milligrams of a solute present in on one liter of the solution. Written as mg/L.

MILLIMHOS A basic unit of electrical conductance.

MILLISEIMEN A basic unit of electrical conductance. Same as millimho.

MILT Reproductive organ (testes) of male fish.

MINERAL A natural inorganic substance having a definite chemical composition and structure.

MINERALS Generally refers to any simple inorganic compounds. In cooling water, these will be soluble form in water.

MIST An aerosol with liquids as the dispersed colloids.

MIXED BED The use of a mixture of cation and anion resin in the same unit to produce a water of extremely high purity.

MIXED INHIBITOR A corrosion inhibitor that suppresses the metal dissolution reaction at the node and interferes with the oxygen reduction process at the cathode.

MIXED LIQUOR The name given the effluent that comes from the aeration tank after the sewage has been mixed with activated sludge and air.

MIXTURE Any combination of two or more chemicals if the combination is not, in whole or in part, the result of a chemical reaction.

ml Milliliter; a metric unit of capacity, equal in volume to one cubic centimeter (cc), or about 1/16 of a cubic inch. There are 1,000 milliliters in one (1) liter.

mmHg Millimeters (mm) of mecury (Hg), a unit of measurement for low pressures or partial vacuums.

MO READING Titration of a 100 ml water sample with N/30 acid to a bromcresol green/methyl red end point.

MODEM A device that converts digital signals to analog signals with the telephone voice band for transmitting data over standard voice grade telephone lines.

MODULATING CONTROL A varying of amplitude, intensity or frequency of a control signal in response to need. Such as pH controller adjusting the output of an acid metering pump by supplying a 4 - 20 mA output proportional to the pH level.

MOISTURE DETERMINATION An action using instruments and calculations to measure the relative or absolute moisture in an air conditioned space.

MOISTURE INDICATOR Instrument used to measure moisture content of a refrigerant.

MOLARITY The number of moles of solute present in one liter of solution.

MOLE 6.02 x 10²³ atoms of an element or molecules of a compound. A unit weight or volume of a chemical corresponding to its molecular weight. A mole of water weighs 18 g, and its vapor occupies 22.4 liters at standard temperature and pressure.

MOLECULAR CONFIGURATION A molecule’s shape.

MOLECULAR WEIGHT Sum of the atomic weights of all elements in one molecule.

MONOMER A molecule, usually an organic compound, having the ability to join with a number of identical molecules to form a polymer.

MONOMOLECULAR A descriptive term used with thin films to indicate dimensional thickness that does not exceed one molecular diameter of the film.

MOTHER BOARD The main circuit board of a system, containing edge connectors, or sockets, so other printed circuit boards (daughter boards) can be plugged into it.

MOTOR RATED HORSEPOWER Horsepower rating inscribed on nameplate of the motor driving the fan.

mppcf Million Particles Per Cubic Foot; a unit for measuring particles of a substance suspended in air. Exposure limits for mineral dust (silica, graphite, Portland cement, nuisance dusts, and others), formerly expressed as mppcf, are now more commonly quoted in mg/u.c.M³.

MSDS Material Safety Data Sheet.

MSHA The Mine Safety and Health Administration of the U.S. Department of the Interior; federal agency with safety and health regulatory and enforcement authorities for mining industry. Also see "OSHA."

MUD BALLS Compacted surface sludge created by channeling during filtration.

MUD DRUM Lower drum in a boiler circuit that acts as a point of recirculation and collects deposits for ultimate removal.

MUFFLER, COMPRESSOR Sound absorber chamber in refrigeration system used to reduce sound of gas pulsations.

MULTIPLE SYSTEM Refrigerating mechanism in which several evaporators are connected to one condensing unit.

MULTIPORT VALUE Any softener control value which combines, in one casting, the three or four steps of manual or automaticc regeneration.

MUNICIPAL TREATMENT A city or community-owned waste treatment plant for municipal and, possibly, industrial waste treatment.

MUTAGEN A physical or chemical agent that is capable of causing chromosomal damage in living organisms.

MUTATION Chromosomal damage to living tissue which can be inherited.

MYCELIUM The collective vegetative portion of the fungus. It is composed of many separate fungus hyphae.

N

N₂ Nitrogen, a colorless, odorless, and tasteless gas that will not burn and will not support combustion. The earth’s atmosphere (air) is about 78 percent nitrogen; a higher concentration, nitrogen can displace oxygen and become a lethal asphyxiant. See "Asxphyxiant."

NaOH Sodium hydroxide, or caustic soda.

NARCOSIS A loss of consciousness.

NASCENT HYDROGEN Atomic hydrogen formed during corrosion that diffuses into steel.

NATURAL CIRCULATION BOILERS Boilers that use the properties of force, weight, and resistance to maintain circulation.

NATURAL CONVECTION Movement of a fluid caused by temperature differences (density changes).

NATURAL DRAFT WATER COOLING TOWER One in which air movement is dependent upon the difference in density between the entering air and internal air. As the heat of the water is transferred to the air passing through the tower, the warmed air tends to rise and draw in fresh air at the base of the tower.

NATURAL FORCES OF MASS ATTRACTION Weak forces that draw two masses together.

NATURAL IMMUNITY A state of being that allows a species to proliferate under conditions that may be stressful to other organisms. Some bacterial species are naturally immune to -cide programs used for controlling biofilms.

NBUAC, OR n=BuAc Normal butyl acetate. See "evaporation rate."

NEAT Free from admixture or dilution.

NEGATIVE CHARGE The electrical potential which an atom acquires when it gains one or more electrons; a characteristic of an anion.

NEMA 1 Indoor protection from dirt. Cover has not seal.

NEMA 2 Indoor protection from dirt and falling water.

NEMA 3 Outdoor protection from rain, sleet, dust and external ice.

NEMA 3R Outdoor protection from rain, sleet and external ice.

NEMA 3S Outdoor protection from rain, sleet, windblown dust and ice lading.

NEMA 4 Indoor/outdoor protection from windblown dust and rain, splashing, hose directed water and external ice.

NEMA 4X Same as NEMA 4 plus corrosion protection. Enclosures are typically Stainless Steel or Fiberglass.

NEMA 5 Indoor protection from airborne dust, falling dirt and dripping liquids

NEMA 6 Indoor/outdoor protection from hose directed water, occasional submersion and external ice.

NEMA 6P Same as NEMA 6 plus prolonged submersion.

NEMA 7 Indoor protection Class I, Group A, B, C and D.

NEMA 8 Indoor/outdoor protection Class I, Group A, B, C and D.

NEMA 9 Indoor protection Class II, Group E, F and G.

NEMA 10 (Mine Safety and Health Administration)

NEMA 12 Indoor protection from circulating dust, falling dirt and dripping liquids.

NEMA 12X Same as NEMA 12 but with knockouts.

NEMA 13S Indoor protection from dust, spraying of water, oil and non-corrosive coolant.

NEOPRENE A synthetic rubber which is resistant to hydrocarbon oil and gas.

NEPHELOMETRIC TURBIDITY An empirical measure of turbidity based on a measurement of the light scattering characteristics (Tyndall effect) of the particulate matter in the water.

NEPHROTOXIN Chemicals which may damage the kidney.

NERVOUS SYSTEM TOXIN A chemical that produces toxic effect on the nervous system. Effects range from narcosis, behavioral changes and decrease in motor function to degeneration of nerve tissue. Technically called a neurtoxin.

NEUROTOXINS Chemicals which may affect the nervous system.

NET EFFECTIVE VOLUME That portion of the total structural volume within which space the circulating water is in intimate contact with the airflow through the tower. Unit: cu. ft.

NETWORK 1. Any interconnection of components, devices, circuits, or systems. 2. A number of points interconnected for communication.

NEUTRAL pH A hydrogen ion concentration of 10^-7 grams per liter of water, or a pH of 7.

NEUTRALIZATION (pH) Addition of an acid or base to an aqueous solution in order to adjust the pH of the solution 7.0. pH 7 is an arbitrary value indicating a neutral condition, neither acidic nor basic, on a pH scale of 1 to 14.

NEUTRALIZING AMINES Inhibitors used to prevent afterboiler corrosion caused by low pH. These amines neutralize carbonic acid and raise condensate pH.

NFPA National Fire Protection Association. Technically applies to pure chemicals under fire conditions. It is, however, commonly applied to mixtures. The ratings are as follows:

NIOSH National Institute of Occupational Safety & Health.

NITRIFICATION The process of oxidizing ammonia by bacteria into nitrites and nitrates.

NITRITES Common term for sodium nitrite which is used for its corrosion inhibitory power in water solutions.

No_x Oxides of nitrogen; undesirable air pollutants. NO_x emissions are regulated by U.S. EPA under the Clean Air Act.

NODE Any point in a network where one or more units are linked to a network.

NOMINAL SIZE TUBING Tubing measurement which has an inside diameter the same as iron pipe of the same stated size.

NOMINAL TOWER DIMENSIONS Width and length measured from and to column center lines; height measured from top of basin curb to top of fan deck (counterflow design) or to top of distribution basin (crossflow design).

NON-CONDENSING TURBINE Turbine that exhausts steam at greater than atmospheric pressure.

NON-CONTACT COOLING The use of water to remove heat from a unit process without the water directly contacting the finished product.

NONCARBONATE HARDNESS Hardness in water caused by chlorides, sulfates, and nitrates of calcium and magnesium.

NONCONDENSABLE GAS Gas which does not change into a liquid at operating temperatures and pressures.

NONCONDENSIBLES Gaseous material not liquefied when associated water vapor is condensed in the same environment.

NONFERROUS Group of metals and metal alloys which contain no iron.

NONFROSTING EVAPORATOR An evaporator which never collects frost or ice on its surface.

NONIONIC An non-ionized molecule in solution such as sugar, or a colloidal particle without a surface charge.

NONOXIDIZING BIOCIDE A biocide whose effectiveness depends upon some property other than its ability to oxidize organic material. For example, systemic poisons and surface active agents.

NORMALITY The number of equivalents of solute present in a solution.

NOSOCOMIAL An illness acquired as a result of a visit to a health care facility.

NOZZLE A metal or plastic device located in a softener underdrain with many small openings designed so that resin beads will not pass.

NPDES PERMIT The National Pollution Discharge Elimination System permit required by and issued by EPA.

NPSH Net Positive Suction Head. Defined as the total suction head in feet of liquid (absolute at the pump centerline or impeller eye) less the absolute vapor pressure (in feet) of the liquid being pumped.

NPT National Pipe Thread (U.S. Standard Pipe Thread)

NRC National Response Center; a notification center in the Coast Guard Building in Washington, D.C., with a toll-free Telephone Number (1-800-424-8802) which must be called when significant oil or chemical spills or other environmentally-related accidents occur.

NSSC The neutral sulfite, semichemical pulping process.

NTA Nitrilotriacetic acid, a chelant with the sodium salt being the usual form.

NTP National Toxicology Program.

NTU (Nephelometric Turbidity Units) An empirical measure of turbidity based on a measurement of the light scattering characteristics (Tyndall Effect) of the particulate matter in water.

NUCLEATE BOILING Formation and release of steam bubbles at a generating tube surface with water alternately wetting the tube surface. This is the preferred mode in an operating boiler, as opposed to film boiling.

NUISANCE PARTICULATES Dusts or other fine solids that are nuisances to the respiratory tract.

NUMBER OF EQUIVALENTS The weight of a compound divided by its equivalent weight.

NUTRIENT PLATES See Petri Dish.

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