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Glossary

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

A

  • Absorption
    The passage of one substance into or through another; e.g., an operation in which one or more soluble components of a gas mixture are dissolved in a liquid.
  • Acclimatization
    The physiological and behavioral adjustments of an organism to changes in its environment.
  • Acid
    A substance which releases hydrogen ions when dissolved in water. Most acids will dissolve the common metals, and will react with a base to form a neutral salt and water.
  • Acid Deposition/Acid Rain
    A complex chemical and atmospheric phenomenon that occurs when emissions of sulfur and nitrogen compounds and other substances are transformed by chemical processes in the atmosphere, often far from the original sources, and then deposited on Earth in either a wet or dry form. The wet forms, popularly called “acid rain,” can fall as rain, snow, or fog. The dry forms are acidic gases or particulates.
  • Activated Carbon
    A granular material usually produced by the roasting of cellulose base substances, such as wood or coconut shells, in the absence of air. It has a very porous structure and is used in water conditioning as an adsorbent for organic matter and certain dissolved gases. Sometimes called “activated charcoal.”
  • Adhesion
    Molecular attraction which holds the surfaces of two substances in contact.
  • Adsorbent
    The process in which matter adheres to the surface of an adsorbent.
  • Adsorption
    1. Adhesion of molecules of gas, liquid, or dissolved solids to a surface.
    2. An advanced method of treating wastes in which activated carbon removes organic matter from wastewater.
  • Advanced Waste Water Treatment
    Any treatment of sewage that goes beyond the secondary or biological water treatment stage and includes the removal of nutrients such as phosphorus and nitrogen and a high percentage of suspended solids.
  • Aeration Tank
    A chamber used to inject air into water.
  • Aeration
    A process which promotes biological degradation of organic water. The process may be passive (as when waste is exposed to air), or active (as when a mixing or bubbling device introduces the air).
  • Agglomeration
    The process by which precipitation particles grow larger by collision or contact with cloud particles or other precipitation particles.
  • Algae
    Simple rootless plants that grow in sunlit waters in relative proportion to the amounts of nutrients available. They can affect water quality adversely by lowering the dissolved oxygen in the water. They are food for fish and small aquatic animals.
  • Alkalinity
    The quantitative capacity of a water or water solution to neutralize an acid. It is usually measured by titration with a standard acid solution of sulfuric acid, and expressed in terms of its calcium carbonate equivalent.
  • Anaerobic
    A life or process that occurs in, or is not destroyed by, the absence of oxygen.
  • Anion
    A negatively charged ion in solution, such as bicarbonate, chloride or sulfate.
  • Anion Exchange
    An ion exchange process in which anions in solution are exchanged for other anions from an ion exchanger. In demineralization, for example, bicarbonate, chloride and sulfate anions are removed from solution in exchange for a chemically equivalent number of hydroxide anions from the anion exchange resin.
  • Activated Sludge Process
    The activated sludge process is a type of wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa.
  • Aeration
    To put air or a gas into liquid.

B

  • Backwash
    The process in which beds of filter or ion exchange media are subjected to flow opposite to the service flow direction to loosen the bed and to flush suspended matter, collected during the service run, to waste.
  • Bacteria
    (Singular: bacterium) Microscopic living organisms which can aid in pollution control by consuming or breaking down organic matter in sewage. Or by similarly acting on oil spills or other water pollutants. Bacteria in soil, water or air can also cause human, animal and plant health problems.
  • Baghouse Filter
    Large fabric bag, usually made of glass fibers, used to eliminate intermediate and large (greater than 20 microns in diameter) particles. This device operates in a way similar to the bag of an electric vacuum cleaner, passing the air and smaller particulate matter, while entrapping the larger particulates.
  • Bar Screen
    In wastewater treatment, a device used to remove large solids.
  • Base
    A substance which releases hydroxyl ions when dissolved in water. Bases react with acids to form a neutral salt and water.
  • Bed
    The exchange or filter media in a column or other tank or operational vessel.
  • Bed Depth
    The height of the ion exchange or filter media in the vessel after preparation for service.
  • Biochemical Oxygen Demand (BOD)
    A measure of the amount of oxygen consumed in the biological processes that break down organic matter in water. The greater the BOD, the greater the degree of pollution.
  • Biodegradable
    The ability to break down or decompose rapidly under natural conditions and processes.
  • Biological Control
    In pest control, the use of animals and organisms that eat or otherwise kill or out-compete pests.
  • Brackish Water
    A mixture of fresh and salt water.
  • 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.
  • Brackish
    Salty.
  • Bacteria
    Any one of a group of very small living things that often cause disease.
  • Biodegradation
    Capable of being slowly destroyed and broken down into very small parts by natural processes, bacteria, etc.

C

  • Cadmium (Cd)
    A heavy metal element that accumulates in the environment.
  • Calcium
    One of the principal elements making up the earth’s crust, the compounds of which when dissolved make the water hard. The presence of calcium in water is a factor contributing to the formation of scale and insoluble soap curd which are a means of clearly identifying hard water.
  • Capacity
    An expression of the quantity of an undesirable material which can be removed by a water conditioner between cleaning regeneration or replacement, as determined under standard test conditions. For ion exchange water softeners, the capacity is expressed in grains of hardness removal between successive regenerations and is related to the pound of salt used in regeneration. For filters, the capacity may be expressed in the length of time or total gallons delivered between servicing.
  • Carbon Adsorber
    An add-on control device which uses activated carbon to absorb volatile organic compounds from a gas stream. The VOCs are later recovered from the carbon.
  • Carbon Dioxide
    A gas present in the atmosphere and formed by the decay of organic matter; the gas in carbonated beverages; in water it forms carbonic acid.
  • Carbon Monoxide (CO)
    A colorless, odorless, poisonous gas produced by incomplete fossil fuel combustion.
  • Carcinogen
    Any substance that can cause or contribute to the production of cancer.
  • Carcinogenic
    Cancer-producing.
  • Cathodic Protection
    A technique to prevent corrosion of a metal surface by making that surface the cathode of an electrochemical cell.
  • Cation
    An ion with a positive electrical charge, such as calcium, magnesium and sodium.
  • Cation Exchange
    Ion exchange process in which cations in solution are exchanged for other cations from an ion exchanger.
  • Caustic
    Any substance capable of burning or destroying animal flesh or tissue.
  • Caustic Soda
    Sodium hydroxide, a strong alkaline substance used as the cleaning agent in some detergents.
  • Cesium (Cs)
    A silver-white, soft ductile element of the alkali metal group that is the most electropositive element known. Used especially in photoelectric cells.
  • Chelate
    To form a complex chemical compound in which an ion, usually metallic, is bound into a stable ring structure.
  • Chemical Oxygen Demand (COD)
    A measure of the oxygen required to oxidize all compounds in water, both organic and inorganic.
  • Chemical Treatment
    Any one of a variety of technologies that use chemicals or a variety of chemical processes to treat waste.
  • Chlorination
    The application of chlorine to drinking water, sewage, or industrial waste to disinfect or to oxidize undesirable compounds.
  • Chlorinator
    A device that adds chlorine, in gas or liquid form, to water or sewage to kill infectious bacteria.
  • Chlorine
    A gas, Cl2, widely used in the disinfection of water and an oxidizing agent for organic matter, iron, etc.
  • Chlorine-Contact Chamber
    That part of a water treatment plant where effluent is disinfected by chlorine.
  • Chlorofluorocarbons (CFCs)
    A family of inert, nontoxic, and easily liquified chemicals used in refrigeration, air conditioning, packaging, insulation, or as solvents and aerosol propellants. Because CFCs are not destroyed in the lower atmosphere they drift into the upper atmosphere where their chlorine components destroy ozone.
  • Clarification
    Clearing action that occurs during wastewater treatment when solids settle out. This is often aided by centrifugal action and chemically induced coagulation in wastewater.
  • Clarifier
    A tank in which solids are settled to the bottom and are subsequently removed as sludge.
  • Coagulant
    A material, such as alum, which will form a gelatinous precipitate in water, and cause the agglomeration of finely divided particles into larger particles which can then be removed by settling and/or filtration.
  • Coagulation
    A clumping of particles in wastewater to settle out impurities. It is often induced by chemicals, such as lime, alum, and iron salts.
  • Coliform Index
    A rating of the purity of water based on a count of fecal bacteria.
  • Coliform Organism
    Microorganisms found in the intestinal tract of humans and animals. Their presence in water indicates fecal pollution and potentially dangerous bacterial contamination by disease-causing microorganisms.
  • Conductance
    A measure of the ability of a solution to carry electricity; the reciprocal of the electrical resistance. The unit of conductance is the ohm (reciprocal ohm).
  • Conductivity
    The quality or power to carry electrical current; in water, the conductivity is related to the concentration of ions capable of carrying electrical current.
  • Coolant
    A liquid or gas used to reduce the heat generated by power production in nuclear reactors, electric generators, various industrial and mechanical processes, and automobile engines.
  • Cooling Tower
    A structure that helps remove heat from water used as a coolant; e.g., in electric power generating plants.
  • Corrosion
    The dissolving and wearing away of metal caused by a chemical reaction such as between water and the pipes that the water contacts, chemicals touching a metal surface, or contact between two metals.
  • Cubic Feet Per Minute (CFM)
    A measure of the volume of a substance flowing through air within a fixed period of time. With regard to indoor air, refers to the amount of air, in cubic feet, that is exchanged with indoor air in a minute’s time, or an air exchange rate.
  • Cycle
    A series of events or steps which ultimately lead back to the starting point, such as the exhaustion–regeneration cycle of an ion exchange system; sometimes incorrectly used in reference to a single step of a complete cycle.
  • Cellulose Acetate
    Any of several compounds insoluble in water that are formed especially by the action of acetic acid, anhydride of acetic acid, and sulphuric acid on cellulose and are used for making textile fibers, packaging sheets, photographic films, and varnishes.
  • Colloids
    A substance that consists of particles dispersed throughout another substance which are too small for resolution with an ordinary light microscope but are incapable of passing through a semi-permeable membrane.
  • Clarifiers
    Clarifiers are settling tanks built with mechanical means for continuous removal of solids being deposited by sedimentation. A clarifier is generally used to remove solid particulates or suspended solids from liquid for clarification and/or thickening.
  • Contaminants
    Something that makes a place or a substance (such as water, air, or food) no longer suitable for use.

D

  • D.I. or DI
    Abbreviation for “deionization”.
  • Dechlorination
    Removal of chlorine from a substance by chemically replacing it with hydrogen or hydroxide ions in order to detoxify the substances involved.
  • DEIONIZATION
    The removal of all ionized minerals and salts (both cationic and anionic) from a solution by a two-phase ion exchange procedure. First, positively charged ions are removed by a cation exchange resin for a chemically equivalent amount of hydrogen ions. Second, negatively charged ions are removed by an anion exchange resin for a chemically equivalent amount of hydroxide ions. The hydrogen and hydroxide ions introduced in this process unite to form water molecules. The term is often used interchangeably with demineralization.
  • DEMINERALIZATION
    The removal of ionized inorganic minerals and salts (not organic materials) from a solution by a two-phase ion exchange procedure; similar to deionization, and the two terms are often used interchangeably.
  • Denitrification
    The anaerobic biological reduction of nitrate nitrogen to nitrogen gas.
  • Desalinization
    Removing salt from ocean or brackish water.
  • Digester
    In wastewater treatment, a closed tank; in solid waste conversion, a unit in which bacterial action is induced and accelerated in order to break down organic matter and establish the proper carbon to nitrogen ratio.
  • Digestion
    The biochemical decomposition of organic matter, resulting in partial gasification, liquefaction, and mineralization of pollutants.
  • Disinfectant
    A chemical or physical process that kills pathogenic organisms in water. Chlorine is often used to disinfect sewage treatment effluent, water supplies, wells, and swimming pools.
  • DISINFECTION
    To clean (something) especially by using a chemical substance that kills all germs and bacteria.
  • Dispersant
    A chemical agent used to break up concentrations of organic material such as spilled oil.
  • Disposal
    Final placement or destruction of toxic, radioactive, or other wastes; surplus or banned pesticides or other chemicals; polluted soils; and drums containing hazardous materials from removal actions or accidental releases. Disposal may be accomplished through use of approved secure landfills, surface impoundments, land farming, deep well injection, ocean dumping, or incineration.
  • Dissolved Oxygen (DO)
    The oxygen freely available in water. Dissolved oxygen is vital to fish and other aquatic life and for the prevention of odors. Traditionally, the level of dissolved oxygen has been accepted as the single most important indicator of a water body’s ability to support desirable aquatic life. Secondary and advanced waste treatment are generally designed to protect DO in waste-receiving waters.
  • DISSOLVED SOLIDS
    The weight of matter in true solution in a stated volume of water; includes both inorganic and organic matter; usually determined by weighing the residue after evaporation of the water at 105 or 180 Degrees Celsius.
  • DISTILLATION
    The process in which a liquid, such as water, is converted into its vapor state by heating, and the vapor cooled and condensed to the liquid state and collected; used to remove solids and other impurities from water. Multiple distillations are required for extreme purity.
  • Demineralisation
    The process of removal of minerals or salts from water.

E

  • Ecology
    The relationship of living things to one another and their environment, or the study of such relationships.
  • Effluent
    Liquid (such as sewage or industrial chemicals) that is released as waste.
  • Electrodialysis
    A process that uses electrical current applied to permeable membranes to remove minerals from water. Often used to desalinize salty or brackish water.
  • Electrostatic Precipitator (ESP)
    An air pollution control device that removes particles from a gas stream (smoke) after combustion occurs. The ESP imparts an electrical charge to the particles, causing them to adhere to metal plates inside the precipitator. Rapping on the plates causes the particles to fall into a hopper for disposal.
  • EQUIVALENT PER MILLION
    A unit of concentration used in chemical calculations, calculated by dividing the concentration in ppm or mg/l by the equivalent weight.
  • Erosion
    The wearing away of land surface by wind or water. Erosion occurs naturally from weather or runoff but can be intensified by land-clearing practices related to farming, residential or industrial development, road building, or timber-cutting.
  • Evaporation Ponds
    Areas where sewage sludge is dumped and allowed to dry out.
  • EXHAUSTION
    The state of an ion exchange material in which it is no longer capable of effective function due to the depletion of the initial supply of exchangeable ions; the exhaustion point may be defined in terms of a limiting concentration of matter in the effluent, or in the case of demineralization, in terms of electrical conductivity.

F

  • FILTER
    Specifically, a device or system for the removal of solid particles (suspended solids); in general, includes mechanical, adsorptive, oxidizing and neutralizing filters.
  • Filtration
    The act or process of removing something unwanted from a liquid, gas, etc., by using a filter.
  • Floc
    A clump of solids formed in sewage by biological or chemical action.
  • FLOCCULATION
    The agglomeration of finely divided suspended solids into larger, usually gelatinous particles; the development of a “floc” after treatment with a coagulant by gentle stirring or mixing.
  • FLOW CONTROL
    A device designed to limit the flow of water or regenerant to a predetermined value over a broad range of inlet water pressures.
  • FLOW RATE
    The quantity of water or regenerant which passes a given point in a specified unit of time, often expressed in gallons per minute.
  • Flowmeter
    A gauge that shows the speed of wastewater moving through a treatment plant. Also used to measure the speed of liquids moving through various industrial processes.
  • FLUORIDATION
    The addition of a fluoride compound to a water supply to produce the concentration desired for the reduction in incidence of dental caries.
  • Fluorides
    Gaseous, solid, or dissolved compounds containing fluorine that result from industrial processes. Excessive amounts in food can lead to fluor.
  • Fluorocarbon (FCs)
    Any of a number of organic compounds analogous to hydrocarbons in which one or more hydrogen atoms are replaced by fluorine. Once used in the United States as a propellant in aerosols, they are now primarily used in coolants and some industrial processes. FCs containing chlorine are called chlorofluorocarbons (CFCs). They are believed to be modifying the ozone layer in the stratosphere, thereby allowing more harmful solar radiation to reach the Earth’s surface.
  • Fluorosis
    An abnormal condition caused by excessive intake of fluorine, characterized chiefly by mottling of the teeth.
  • Formaldehyde
    A colorless, pungent, irritating gas, CH₂O, used chiefly as a disinfectant and preservative and in synthesizing other compounds and resins.
  • FOULING
    The process in which undesirable foreign matter accumulates in a bed of filter media or ion exchanger, clogging pores and coating surfaces and thus inhibiting or retarding the proper operation of the bed.
  • FREEBOARD
    The vertical distance between a bed of filter media or ion exchange material and the overflow or collector for backwash water; the height above the bed of granular media available for bed expansion during backwashing; may be expressed either as a linear distance or a percentage of bed depth.
  • Fresh Water
    Water that generally contains less than 1,000 milligrams-per-liter of dissolved solids.
  • Fungi
    (Singular, Fungus) Molds, mildews, yeasts, mushrooms, and puff-balls — a group of organisms that lack chlorophyll (i.e., are not photosynthetic) and which are usually non-mobile, filamentous, and multicellular. Some grow in the ground, others attach themselves to decaying trees and other plants, getting their nutrition from decomposing organic matter. Some cause disease, others stabilize sewage and break down solid wastes in composting.
  • Fungicide
    Pesticides which are used to control, prevent, or destroy fungi.

G

  • Germicide
    A compound that kills disease-causing microorganisms.
  • GPG
    Abbreviation for “grain per gallon”.
  • GRAIN
    (gr.) A unit of weight equal to 1/7000th of a pound, or 0.0648 gram.
  • GRAIN PER GALLON
    (gpg) A common basis for reporting water analyses in the United States and Canada; one grain per U.S. gallon equals 17.12 milligrams per liter (mg/l) or parts per million (ppm).
  • GRAM
    (g) The basic unit of weight (mass) of the metric system, originally intended to be the weight of 1 cubic centimeter of water at 4°C.
  • Granular Activated Carbon Treatment
    A filtering system often used in small water systems and individual homes to remove organics. GAC can be highly effective in removing elevated levels of radon from water.
  • Gray Water
    The term given to domestic wastewater composed of washwater from sinks, kitchen sinks, bathroom sinks and tubs, and laundry tubs.
  • Greenhouse Effect
    The warming of the Earth’s atmosphere caused by a build-up of carbon dioxide or other trace gases. It is believed by many scientists that this build-up allows light from the sun to heat the Earth but prevents a counterbalancing loss of heat.
  • GREENSAND
    A natural mineral, primarily composed of complex silicates, which possess ion exchange properties.

H

  • HARD WATER
    Water with a total hardness of one grain per gallon or more, as calcium carbonate equivalent.
  • HARDNESS
    A characteristic of natural water due to the presence of dissolved calcium and magnesium; water hardness is responsible for most scale formation in pipes and water heaters, and forms insoluble “curd” when it reacts with soaps. Hardness is usually expressed in grains per gallon, parts per million, or milligrams per liter, all as calcium carbonate equivalent.
  • Heavy Metals
    Metallic elements with high atomic weights, e.g., mercury, chromium, cadmium, arsenic, and lead. They can damage living things at low concentrations and tend to accumulate in the food chain.
  • HYDROLOGIC CYCLE
    The water cycle, including precipitation of water from the atmosphere as rain or snow, flow of water over or through the earth, and evaporation or transpiration to water vapor in the atmosphere.
  • Hydrostatic Pressure
    Fluid statics or hydrostatics is the branch of fluid mechanics that studies fluids at rest and the pressure in a fluid or exerted by a fluid on an immersed body.

I

  • Infiltration
    1. The penetration of water through the ground surface into sub-surface soil or the penetration of water from the soil into sewer or other pipes through defective joints, connections, or manhole walls.
    2. A land application technique where large volumes of wastewater are applied to land, allowed to penetrate the surface and percolate through the underlying soil.
  • Inflow
    Entry of extraneous rainwater into a sewer system from sources other than infiltration, such as basement drains, manholes, storm drains, and street washing.
  • Influent
    Water, wastewater, or other liquid flowing into a reservoir, basin, or treatment plant.
  • Insecticide
    A pesticide compound specifically used to kill or control the growth of insects.
  • ION EXCHANGE
    A reversible process in which ions are released from an insoluble permanent material in exchange for other ions in a surrounding solution. The exchange direction depends upon the affinities of the ion exchanger for the ions present and their concentrations.
  • Ion Exchange Treatment
    A common water softening method often found in large-scale water purification plants that remove some organics and radium by adding calcium oxide or calcium hydroxide to increase the pH, causing metals to precipitate out.
  • ION EXCHANGER
    A permanent, insoluble material that contains ions which will exchange reversibly with other ions in a surrounding solution. Both cation and anion exchangers are used in water conditioning.
  • Ion
    An electrically charged atom or group of atoms which can be drawn from wastewater during electrodialysis.
  • IONIZATION
    The process in which atoms gain or lose electrons and become positively or negatively charged ions; sometimes used synonymously with dissociation.
  • IRON
    An element often found dissolved in groundwater (as ferrous iron) in concentrations usually ranging from 0 to 10 ppm (mg/L). It is objectionable due to staining, taste issues, and color formation when reacting with beverages such as coffee and tea.
  • IRON BACTERIA
    Organisms capable of utilizing ferrous iron in their metabolism and precipitating ferric hydroxide in gelatinous deposits. They collect in pipelines and tanks, causing staining, odor, and water quality issues.
  • Impermeable
    Not allowing substances such as liquids to pass through.
  • Ionic
    Relating to or characterized by ions.
  • Ion Exchange
    A reversible interchange of ions on an insoluble solid with like-charged ions in a surrounding solution; widely used for softening or demineralizing water.
  • Ions
    An atom or group of atoms that has a positive or negative electric charge by losing or gaining electrons.

L

  • Lagoon
    (1) A shallow pond where sunlight, bacterial action, and oxygen work to purify wastewater; also used for storage of wastewaters or spent nuclear fuel rods. (2) A shallow body of water often separated from the sea by coral reefs or sandbars.
  • LANGELIER’S INDEX
    A calculated number used to predict whether a water will precipitate, be in equilibrium with, or dissolve calcium carbonate. It is sometimes incorrectly assumed that any water capable of dissolving calcium carbonate is automatically corrosive.
  • Leachate Collection System
    A system designed to gather leachate and pump it to the surface for treatment.
  • Leachate
    A liquid formed when water collects contaminants while trickling through wastes, agricultural pesticides, or fertilizers. Leaching can occur in farming areas, feedlots, and landfills, and can result in hazardous substances entering surface water, groundwater, or soil.
  • LIME
    The common name for calcium oxide (CaO); hydrated lime is calcium hydroxide [Ca(OH)₂].

M

  • MAGNESIUM
    One of the elements making up the earth’s crust, the compounds of which when dissolved in water make the water hard. The presence of magnesium in water contributes to the formation of scale and insoluble soap curds.
  • MANGANESE
    An element sometimes found dissolved in groundwater, usually along with dissolved iron but in lower concentrations; causes black stains and other problems similar to iron.
  • MANGANESE GREENSAND
    Greensand that has been processed to incorporate higher oxides of manganese in its pores and on its surface. It has mild oxidizing power and is used for oxidation and precipitation of iron, manganese, and/or hydrogen sulfide to remove them from water.
  • Mechanical Aeration
    The use of mechanical energy to inject air into water to enable a waste stream to absorb oxygen.
  • Mechanical Turbulence
    Random irregularities of fluid motion in air caused by buildings or mechanical, non-thermal processes.
  • Mercury
    A heavy metal that can accumulate in the environment and is highly toxic if breathed or swallowed.
  • Methane
    A colorless, non-poisonous, flammable gas created by anaerobic decomposition of organic compounds.
  • MICRON
    A linear measure equal to one millionth of a meter.
  • MINERAL
    An inorganic substance such as rocks or similar matter found in the earth’s strata; normally has definite chemical composition and crystal structure. The term also refers to inorganic matter derived from minerals, such as ions found in water.
  • Macromolecules
    A very large molecule, such as a protein or rubber.
  • Microbes
    An extremely small living organism that can be seen only with a microscope.
  • Microfiltration
    A filtration process used to separate colloidal and other fine particles with linear dimensions of approximately 0.02 µm to 10 µm.
  • Monovalent
    Having a valence of one.

N

  • NEGATIVE CHARGE
    The electrical charge on an electrode or ion in solution due to the presence of an excess of electrons.
  • Nitrate
    A compound containing nitrogen that can exist in the atmosphere or dissolved in water, and may have harmful effects on humans and animals. Nitrates in water can cause severe illness in infants and cows.
  • NONCARBONATE HARDNESS
    Water hardness caused by compounds such as calcium and magnesium chlorides, sulfates, or nitrates; it is the portion of total hardness that exceeds total alkalinity.
  • Nutrient
    Any substance assimilated by living organisms that promotes growth. The term generally refers to nitrogen and phosphorus in wastewater, but may also include other essential and trace elements.

O

  • Operation And Maintenance
    1. Activities conducted at a site after a Superfund action is completed to ensure that the action remains effective. 2. Actions taken after construction to ensure wastewater treatment facilities are properly operated, maintained, and managed to achieve efficiency and comply with effluent limits.
  • OPERATION PRESSURE
    The range of pressure, usually expressed in pounds per square inch (psi), over which a water conditioning device or system is designed to function.
  • Organic Chemicals/Compounds
    Substances produced by plants or animals that contain mainly carbon, hydrogen, and oxygen.
  • Organic Matter
    Carbonaceous waste from plant or animal material originating from domestic or industrial sources.
  • Organic
    1. Referring to or derived from living organisms. 2. In chemistry, any compound containing carbon.
  • Organism
    Any living thing.
  • Organophosphates
    Pesticide chemicals that contain phosphorus and are used to control insects. They are short-lived but may be toxic when initially applied.
  • OSMOSIS
    The diffusion of a solvent (such as water) through a semi-permeable membrane that allows the solvent to pass but blocks most dissolved substances, normally flowing from a dilute to a concentrated solution.
  • Overturn
    The mixing of water layers from top to bottom, occurring in spring, fall, or after storms, resulting in uniform physical and chemical water properties at all depths.
  • Oxidant
    A substance containing oxygen that chemically reacts to produce a new substance; a major ingredient of photochemical smog.
  • OXIDATION
    A chemical reaction in which electrons are removed from an atom, ion, or compound. It includes processes such as the addition of oxygen, combustion, and the slow rusting of iron.
  • Oxidation Pond
    A man-made body of water where waste is consumed by bacteria; used frequently alongside other wastewater treatment processes. Similar to a sewage lagoon.
  • Oxidation
    1. The addition of oxygen to break down organic waste or chemicals in sewage. 2. Oxygen combining with other elements. 3. A chemical process in which electrons are removed from a molecule.
  • Ozonator
    A device used to add ozone to water.
  • Ozone (O₃)
    A form of oxygen found in the stratosphere and troposphere. In the stratosphere, it forms a protective layer shielding Earth from ultraviolet radiation. In the troposphere, it is a harmful pollutant and a major component of photochemical smog, affecting the human respiratory system.
  • Ozone Depletion
    Destruction of the stratospheric ozone layer caused by chlorine- and bromine-bearing compounds (e.g., CFCs and halons) that break down ozone molecules when they reach the upper atmosphere.
  • Osmotic Pressure
    The pressure produced by or associated with osmosis, dependent on solute concentration and temperature.

P

  • Packed Tower
    A pollution control device that forces dirty air through a tower packed with crushed rock or wood chips while liquid is sprayed over the packing material. The pollutants in the air stream either dissolve or chemically react with the liquid.
  • PARTS PER MILLION (PPM)
    A common basis for reporting the results of water and wastewater analysis, indicating the number of parts by weight of a dissolved or suspended constituent, per million parts by weight of water or other solvent. In dilute water solutions, one part per million is practically equal to one milligram per liter, which is the preferred unit.
  • Pathogens
    Microorganisms that can cause disease in other organisms or in humans, animals, and plants. They may be bacteria, viruses, or parasites and are found in sewage, in runoff from animal farms or rural areas populated with domestic and/or wild animals, and in water used for swimming. Fish and shellfish contaminated by pathogens, or the contaminated water itself, can cause serious illnesses.
  • Percolation
    The movement of water downward and radially through the sub-surface soil layers, usually continuing downward to the ground water.
  • Permeability
    The rate at which liquids pass through soil or other materials in a specified direction.
  • pH
    Stands for “potenz hydrogen”, German for “potential of hydrogen”. In water chemistry, pH is expressed as the concentration of hydrogen ions to hydroxyl ions. The pH scale is a logarithmic scale from 1 to 14, with 7 being neutral; above 7, more alkaline; and below 7 more acidic.
  • Plankton
    Tiny plants and animals that live in water.
  • Pollution
    Generally, the presence of matter or energy whose nature, location, or quantity produces undesired environmental effects. Under the Clean Water Act, for example, the term is defined as the man-made or man-induced alteration of the physical, biological, and radiological integrity of water.
  • Polyelectrolytes
    Synthetic chemicals that help solids to clump during sewage treatment.
  • Polymer
    Basic molecular ingredients in plastic.
  • Polyvinyl Chloride (PVC)
    A tough, environmentally indestructible plastic that releases hydrochloric acid when burned.
  • Potable Water
    Water that is safe for drinking and cooking.
  • PPM
    The abbreviation for “part per million”.
  • PPM/PPB
    Parts per million/parts per billion, a way of expressing tiny concentrations of pollutants in air, water, soil, human tissue, food, or other products.
  • PRECIPITATE
    To cause a dissolved substance to form a solid particle which can be removed by settling or filtering, such as in the removal of dissolved iron by oxidation, precipitation, and filtration. The term is also used to refer to the solid formed, and to the condensation of water in the atmosphere to form rain or snow.
  • Precipitate
    A solid that separates from a solution because of some chemical or physical change.
  • Precipitation
    Removal of solids from liquid waste so that the hazardous solid portion can be disposed of safely; removal of particles from airborne emissions.
  • Precipitators
    Air pollution control devices that collect particles from emissions.
  • Pretreatment
    Processes used to reduce, eliminate, or alter the nature of wastewater pollutants from non-domestic sources before they are discharged into publicly owned treatment works.
  • Primary Waste Treatment
    First steps in wastewater treatment; screens and sedimentation tanks are used to remove most materials that float or will settle. Primary treatment results in the removal of about 30 percent of carbonaceous biochemical oxygen demand from domestic sewage.
  • Permeable
    Allowing liquids and gases to pass through.
  • Pore Size
    The ability of a filter media to obstruct particles which are greater than the pore size of the media. It is measured in microns.
  • Purification
    The process of eliminating impurities from any matter.
  • Pyrogen
    A fever-producing substance.
  • PVDF
    Polyvinylidene fluoride is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride. PVDF is a specialty plastic used in applications requiring the highest purity, as well as resistance to solvents, acids, and hydrocarbons.
  • Pollutants
    Substances that lead to contamination of the environment.

R

  • RAW WATER
    Untreated water, or any water before it reaches a specific water treatment device or process.
  • Receiving Waters
    A river, lake, ocean, stream, or other watercourse into which wastewater or treated effluent is discharged.
  • Recharge Area
    A land area in which water reaches the zone of saturation from surface infiltration, e.g., an area where rainwater soaks through the earth to reach an aquifer.
  • Recharge
    The process by which water is added to a zone of saturation, usually by percolation from the soil surface, e.g., the recharge of an aquifer.
  • REGENERANT
    A solution of a chemical compound used to restore the capacity of an ion exchange system. Sodium chloride brine is used as a regenerant for ion exchange water softeners, and acids and bases are used as regenerants for the cation and anion resins used in demineralization.
  • Regeneration
    Manipulation of individual cells or masses of cells to cause them to develop into whole plants.
  • RESIN
    Synthetic organic ion exchange material, such as the high capacity cation exchange resin widely used in water softeners.
  • Resistance
    For plants and animals, the ability to withstand poor environmental conditions and/or attacks by chemicals or disease. The ability may be inborn or developed.
  • Reverse Osmosis
    A water treatment process used in small water systems by adding pressure to force water through a semi-permeable membrane. Reverse osmosis removes most drinking water contaminants. Also used in wastewater treatment. Large-scale reverse osmosis plants are now being developed.
  • Reinforced
    To strengthen by adding more material for support.

S

  • SALINE WATER
    Water containing an excessive amount of dissolved salts, usually over 10,000 mg/l.
  • Salinity
    The degree of salt in water.
  • SALT
    The common name for the specific chemical compound sodium chloride used in the regeneration of ion exchange water softeners. In chemistry, the term is applied to a class of chemical compounds formed by neutralization of an acid with a base.
  • Salt Water Intrusion
    The invasion of fresh surface or groundwater by salt water. If the salt water comes from the ocean, it may be called seawater intrusion.
  • Sand Filters
    Devices that remove some suspended solids from sewage. Air and bacteria decompose additional wastes filtering through the sand so that cleaner water drains from the bed.
  • Secondary Treatment
    The second step in most publicly owned waste treatment systems in which bacteria consume the organic parts of the waste. This treatment removes floating and settleable solids and about 90% of oxygen-demanding substances and suspended solids. Disinfection is the final stage.
  • Sediments
    Soil, sand, and minerals washed from land into water usually after rain. They pile up in reservoirs, rivers, and harbors, destroying fish-nesting areas and clouding water, limiting sunlight to aquatic plants.
  • SEQUESTER
    A chemical reaction in which certain ions are bound into a stable, water-soluble compound, preventing undesirable actions by the ions.
  • SEQUESTERING AGENT
    A chemical compound sometimes added to water to tie up undesirable ions, keep them in solution, and reduce their normal effects. For example, polyphosphates can sequester hardness and prevent reaction with soap.
  • Silt
    Fine particles of sand or rock that can be carried by air or water and deposited as sediment.
  • Slow Sand Filtration
    A treatment process involving passage of raw water through a bed of sand at low velocity, resulting in substantial removal of chemical and biological contaminants.
  • Sludge
    A semi-solid residue from air or water treatment processes. Sludge can be a hazardous waste.
  • SODA ASH
    The common name for sodium carbonate, a chemical compound used as an alkaline builder in soap and detergent formulations, to neutralize acid water, and in lime-soda ash water treatment processes.
  • SODIUM
    An ion found in natural water supplies and introduced during ion exchange water softening. Sodium compounds are highly soluble and do not react with soaps or detergents.
  • SODIUM CHLORIDE
    The chemical name for common salt, widely used in the regeneration of ion exchange water softeners.
  • Soft Detergents
    Cleaning agents that break down naturally in the environment.
  • Soft Water
    Any water that is not “hard,” i.e., does not contain significant amounts of dissolved minerals such as calcium or magnesium salts.
  • Soot
    Carbon dust formed by incomplete combustion.
  • Sorption
    The action of soaking up or attracting substances. Used in many pollution control systems.
  • SPECIFIC GRAVITY
    The ratio of the weight of a specific volume of a substance to the weight of the same volume of pure water at 4°C.
  • Sterilization
    1. In pest control, use of radiation or chemicals to damage reproductive cells. 2. Destruction of all living organisms in water or on surfaces. Disinfection destroys most organisms but not all.
  • SULFATE-REDUCING BACTERIA
    Bacteria capable of reducing sulfates in water to hydrogen sulfide gas, producing unpleasant tastes and odors. They are nuisance organisms with no sanitary significance.
  • SULFUR
    A yellow solid element. Also used as a slang term for water containing hydrogen sulfide gas.
  • Sulfur Dioxide (SO2)
    A heavy, pungent, colorless gaseous air pollutant formed primarily by combustion of fossil fuels.
  • Surfactant
    A surface-active agent used in detergents to cause lathering.
  • Suspended Solids
    Small solid pollutants floating on the surface or suspended in liquids, resisting removal by conventional means. Also used as an indicator of water quality.
  • Semi-permeable
    Permeable to some small molecules but not to larger particles.
  • Substrate
    The base on which an organism lives.
  • Sewage
    Waste material carried away from homes and buildings through a pipe system.
  • Sedimentation
    The natural process where material such as sand or stones settles to the bottom of a body of water, forming a solid layer.
  • Scour
    To clean foreign matter or impurities, typically by washing.
  • Synthetic Carbon
    Any chemically synthesized form of carbon.

T

  • TDS
    The abbreviation for “total dissolved solids”.
  • Tertiary Treatment
    Advanced cleaning of wastewater that goes beyond the secondary or biological stage. It removes nutrients such as phosphorus and nitrogen and most BOD and suspended solids. Federal regulations guide site determinations under programs like Superfund and spill prevention/control.
  • TOTAL ACIDITY
    The total of all forms of acidity, including mineral acidity, carbon dioxide, and acid salts. Usually determined by titration with a standard base solution to the phenolphthalein endpoint (pH 8.3).
  • TOTAL ALKALINITY
    The alkalinity of water determined by titration with standard acid solution to the methyl orange endpoint (pH ~4.5); sometimes called “M alkalinity”. Includes hydroxides, carbonates, and bicarbonates.
  • TOTAL DISSOLVED SOLIDS
    The weight of solids per unit volume of water in true solution, usually determined by evaporating a measured volume of filtered water and weighing the residue.
  • TOTAL HARDNESS
    The sum of all hardness constituents in water, expressed as equivalent concentration of calcium carbonate. Mainly due to calcium and magnesium, but may include small amounts of metals like iron.
  • TOTAL SOLIDS
    The weight of all solids, dissolved and suspended, organic and inorganic, per unit volume of water, usually determined by evaporation at 105°C in a pre-weighed dish.
  • Total Suspended Solids (TSS)
    A measure of suspended solids in wastewater, effluent, or water bodies, determined by tests for total suspended non-filterable solids.
  • Trickling Filter
    A coarse biological treatment system in which wastewater is trickled over a bed of stones or other material covered with bacterial growth. The bacteria break down the organic matter.
  • TURBIDITY
    A measure of the amount of finely divided suspended matter in water, causing scattering and absorption of light rays.
  • Thin Film Composite
    Semipermeable membranes manufactured principally for use in water purification or desalination systems.

U

  • ULTRAFILTRATION
    A method of crossflow filtration (similar to reverse osmosis but using lower pressures) which uses a membrane to separate small colloids and large molecules from water and other liquids. Removes particles in the 0.002 to 0.1 micron range, rejecting organics over 1,000 molecular weight while passing ions and smaller organics.
  • ULTRAPURE WATER
    Highly-treated water that is deionized and mineral-free with high resistivity and no organics; commonly used in semiconductor and pharmaceutical industries. Not considered biologically pure or sterile.
  • ULTRAVIOLET (UV)
    Pertaining to ultraviolet light.
  • ULTRAVIOLET (UV) LIGHT
    Radiation having a wavelength shorter than 3900 angstroms and longer than 100 angstroms. Used as a disinfectant; invisible violet end of the light spectrum.
  • ULTRAVIOLET ABSORBER
    Substances that absorb ultraviolet radiation. Added to plastics and rubber to prevent decay from UV rays.
  • ULTRAVIOLET CHAMBER
    The area where water is irradiated with ultraviolet rays.
  • ULTRAVIOLET DEMAND
    The amount of ultraviolet rays required to inactivate certain microorganisms.
  • ULTRAVIOLET DOSAGE
    The amount of disinfectant ultraviolet rays delivered to organisms in the water. Dosage = UV intensity × contact time; measured in watt-seconds per square centimeter.
  • Ultraviolet Rays
    Radiation from the sun. Can be useful for plants and medical procedures, but harmful UV exposure can cause skin cancer or tissue damage. Ozone layer limits harmful rays.
  • UNIFORMITY COEFFICIENT
    Measure of variation in particle sizes of filter and ion exchange media. Ratio of sieve size allowing 60% passage to sieve size allowing 10% passage. 1.00 = uniform particles; higher numbers = less uniformity.
  • UNIVALENT
    Having a valence of one. Also called monovalent.
  • UPFLOW
    Water flow pattern where water enters at the bottom of a vessel or column and exits at the top. Describes ion exchange flow or filter media flow. Can have upflow during treatment and downflow during regeneration (countercurrent flow).
  • UPFLOW SOFTENING
    Water flows upward through the ion exchange bed; media movement restricted. Regeneration brine flows downward. Achieves higher operating efficiency.
  • UPPER DISTRIBUTOR
    Piping at the top of softeners or filters to uniformly distribute incoming water over resin or filter media. In small units, also distributes brine for regeneration.
  • URANIUM (U)
    A radioactive metallic element found naturally only in combination with other substances. Commonly U-238; ~0.7% as U-235, fissionable. Exists in water as anionic complexes UO2(CO3)22- and UO2(CO3)34-.

V

  • VACUUM BREAKER
    A mechanical device that automatically vents a water line to the atmosphere when subject to a partial vacuum, preventing back siphonage.
  • VALIDATION
    1. (Water treatment) Determination that a representative sample of equipment meets specified standards. 2. (Pharmaceutical) Quality control testing and record-keeping to ensure compliance with both quality and prescribed procedures.
  • VIRUS
    A parasitic infectious microbe, composed mainly of protein and nucleic acids, causing diseases in humans. Size: 0.004–0.1 microns; reproduces only within living cells; ~100 times smaller than bacteria.
  • VISCOSITY
    The tendency of a fluid to resist flowing due to internal forces (molecular cohesion or friction). Varies with water temperature.
  • VOCs
    Volatile organic chemicals.
  • VOID VOLUME
    The volume occupied by interstitial spaces between particles of ion exchangers, filter media, or other granular materials in a bed/column. Often expressed as a percent of total bed volume.
  • VOLATILE
    Capable of becoming vapor at relatively low temperatures.
  • VOLATILE ORGANIC CHEMICALS (VOCs)
    Organic chemicals that vaporize at relatively low temperatures.
  • Volatile Organic Compound (VOC)
    Any organic compound participating in atmospheric photochemical reactions, except those designated by the EPA as having negligible photochemical reactivity.
  • Viruses
    Sub-microscopic infective agents with a protein coat surrounding RNA or DNA, lacking a semi-permeable membrane. Grow and multiply only in living cells; cause diseases in humans, animals, and plants.

W

  • Waste Treatment Plant
    A facility containing a series of tanks, screens, filters, and other processes by which pollutants are removed from water.
  • Waste Treatment Stream
    The continuous movement of waste from generator to treater and disposer.
  • WASTE WATER
    Water that has been used. Includes reject water from RO/ultrafiltration/electrodialysis, spent water from ion exchange/filtration backwash, and residential or industrial used water flowing to treatment systems. Storm, surface, and groundwater infiltration may also be included. Term “sewage” is being replaced by “waste water”.
  • WATER (H2O)
    An odorless, colorless, tasteless liquid, existing as ice in solid form and steam in vapor form. Freezes at 0°C and boils at 100°C. Water is polar, a weak electrolyte, slightly compressible, and a major constituent of all living matter. Also called H2O or HOH.
  • WATER RETENTION
    The amount of water, expressed as a percent of wet weight of an ion exchanger, retained within the resin bead and on the surface of fully swollen and drained ion exchange media. Also called water regain.
  • WATER SOFTENER (CHEMICAL)
    A compound added to water to counteract the effects of hard water minerals (calcium and magnesium) and produce softened water, e.g., detergent additives and polyphosphates.
  • WATER SOFTENER (MECHANICAL)
    A pressurized device where hard water passes through cation exchange media to exchange calcium and magnesium ions for sodium or potassium ions, producing softened water. Modern softeners use sulfonated bead styrene/divinylbenzene cation resins.
  • WATER SOFTENER SALT
    Salt used to regenerate residential and commercial cation exchange water softeners. Most commonly sodium chloride (NaCl) in crystal or pellet form; potassium chloride (KCl) may also be used.
  • WATER SOFTENING
    The reduction/removal of calcium and magnesium ions (hardness) from water. Residential/commercial: cation exchange; municipal/industrial: lime softening or lime-soda softening.
  • WATER TREATMENT DEVICE
    Any point-of-use or point-of-entry device sold or leased for residential use to improve water quality by filtration, distillation, adsorption, ion exchange, reverse osmosis, or other treatment.
  • WBA
    Weak base anion exchanger.
  • WEAK ACID CATION EXCHANGERS
    Cation exchange products with functional groups that in hydrogen form cannot split neutral salts to form free acids. High regeneration efficiency but limited to cations associated with alkalinity; can soften water with carbonate/noncarbonate hardness when in sodium form.
  • WEAK BASE ANION EXCHANGERS
    Anion exchange products that cannot split neutral salts to form free bases. High regeneration efficiency but only exchange mineral acid anions (sulfate, chloride, nitrate); cannot remove anions of weak acids (carbonates, bicarbonates, silicates, organics).
  • WEIR
    1. Dam-like wall or plate in an open channel to measure water flow. 2. Wall/obstruction in settling tanks or clarifiers to control flow and prevent short-circuiting.
  • WFI
    Water for Injection.
  • WHO
    World Health Organization.

Y

  • YIELD
    1. The amount of product water produced by a water treatment process. 2. The quantity of water (expressed as a rate of flow—GPM, GPH, GPD, or total quantity per year) that can be collected for a given use from surface or groundwater sources. Yield may vary depending on the proposed use, development plan, and economic considerations.

Z

  • ZEOLITE SOFTENING
    A term formerly used for the removal of calcium and magnesium hardness from water by base exchange using natural or synthetic zeolites. Since the introduction of synthetic organic cation exchange resins, the more correct term is cation exchange softening. Zeolite softening was also called base exchange.
  • ZEOLITES
    Hydrated sodium alumina silicates, either naturally-occurring mined products or synthetic products, with ion exchange properties. Zeolites were formerly used extensively for residential and commercial water softening but have been largely replaced by synthetic organic cation resin ion exchangers of polystyrene divinylbenzene substrate. Modified zeolites such as manganese greensand and synthetic manganese zeolites are still used as catalyst/oxidizing filters for the removal of iron, hydrogen sulfide, and manganese.
  • ZERO DISCHARGE WATER
    A discharge limit applied to manufacturing and commercial establishments in which only normal human sanitary waste waters may be discharged to the municipal sewerage system. All other types of waste water, such as that used in manufacturing processes, must be recycled, and the resulting waste product must be taken to an alternate and approved disposal facility.
  • ZERO SOFT WATER
    Water produced by the cation exchange process and measuring less than 1.0 grain per U.S. gallon (17.1 ppm or 17.1 mg/L) as calcium carbonate. Zeta potential: the electrical potential existing across the interface of solids and liquids, representing the voltage difference between the surface of the diffuse layer surrounding a colloidal particle and the bulk liquid. Also known as electrokinetic potential.
  • ZONE OF AERATION
    The comparatively dry soil or rock located between the ground surface and the top of the water table.
  • ZONE OF SATURATION
    The layer in the ground in which all available interstitial voids (cracks, crevices, holes) are filled with water. The top of this zone is the water table. SEE ALSO water table.
  • ZOOPLANKTON
    Small, usually microscopic animals (such as protozoans), found in lakes and reservoirs.
  • Zooplankton
    Tiny aquatic animals eaten by fish.
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