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• . See “Angstrom (.).”
• A&I Alternative and Innovative.
• A/O® Wastewater treatment process for biological removal of nitrogen by USFil­ter/Krüger.
• A2/O® Biological treatment process for phosphorus and nitrogen removal by USFil­ter/Krüger.
• A2C™ Biological wastewater treatment system by Baker Process — Municipal Division.
• A•I•R Photocatalytic process to destroy VOCs by Trojan Technologies, Inc.
• AA See “atomic absorption spectrophotometry (AA).”
• AAEE American Academy of Environmental Engineers.
• AAP Asbestos Action Program.
• AAPCO American Association of Pesticide Control Of.cials.
• AAQS Ambient air quality standards.
• AARC Alliance for Acid Rain Control.
• AAS American Association for the Advancement of Science.
• ABA1000® Alumina oxide for phosphate reduction by Selecto, Inc.
• ABA2000® Alumina oxide for lead and heavy metals removal by Selecto, Inc.
• ABA8000® Alumina oxide for .uoride removal by Selecto, Inc.
• abandoned well A well whose use has been permanently discontinued or which is in a state of such disrepair that it cannot be used for its intended purpose.
• abatement Reducing the degree or intensity of, or eliminating, pollution.
• abattoir A place where animals are slaughtered for their meat and meat byproducts.
• ABC Filter™ Automatic backwashable cartridge .lter by USFilter/Rockford.
• Abcor® Ultra.ltration membrane product by Koch Membrane Systems, Inc.
• ABF Activated bio-.ltration wastewater treatment system by In.lco Degremont, Inc.
• ABF Traveling bridge type automatic backwashing gravity sand .lter by Aqua-Aerobic Systems, Inc.
• abiocoen All of the geologic, climatic, and other nonliving elements of an eco­system.
• abiotic Nonliving elements in the environment.
• ABJ™ ABJ product group of Sanitaire Corp.
• ablation The combined processes of glacial melting and evaporation which results in a net loss of ice.
• ablation zone The lower part of a glacier where the net loss of ice exceeds the net gain.
• ABS (1) Acrylonitrile-butadiene-styrene. A black plastic material, used in the man­ufacture of pipes and other components. (2) Alkyl-benzene-sulfonate. A sur­factant formerly used in synthetic detergents that resisted biological breakdown.

• absolute .lter rating A .lter rating which indicates that 99.9% of the particles larger than a speci.ed size will be removed by the .lter.
• absolute humidity The total amount of water vapor present in the air, measured in grams per cubic meter.
• absolute pressure The total pressure in a system, equal to the sum of the gage pressure and atmospheric pressure.
• absolute purity water Water with a speci.c resistance of 18.3 megohm-cm at 25°C.
• absolute zero The lowest temperature possible; 0° on the Kelvin scale or approx­imately –273°C (– 459.7°F).
• absorbate A substance used to soak up another substance.
• absorbed dose The amount of a chemical that enters the body of an exposed organism.
• absorbent Any substance that exhibits the properties of absorption.
• absorption The process of transferring molecules of gas, liquid, or a dissolved substance to the surface of a solid where it is bound by chemical or physical forces.
• absorption .eld A trench or pit .lled with gravel or loose rock designed to absorb septic tank ef.uent.
• ABW® Traveling bridge type gravity sand .lter by In.lco Degremont, Inc.
• abyssal zone A zone of deep oceanic waters, generally deeper than 2000 meters and between the hadal and bathyal zones where light does not penetrate.
• AC See “activated carbon.”
• AC® Industrial wastewater treatment unit by Colloid Environmental Technologies Co.
• ACA American Conservation Association.
• acaricide A pesticide used to kill spiders, ticks, or mites.
• ACBM Asbestos-containing building material.
• Accelapak® Modular water treatment plant by In.lco Degremont, Inc.
• Accelator® Solids contact clari.er with primary and secondary mixing zones by In.lco Degremont, Inc.
• Accelo Hi-Cap Filter underdrain block formerly offered by In.lco Degremont, Inc.
• Accelo-Biox® Modular wastewater treatment plant by In.lco Degremont, Inc.
• Accel-o-Fac™ Sewage treatment plant design by Lake Aid Systems.
• acceptable risk The level of risk associated with minimal adverse effects, usually determined by a risk analysis.
• Access Analytical Former name of IDEXX Laboratories, Inc.
• accessory species Species found in less than half but more than one quarter of the area covered by a plant community.
• accident site The location of an unexpected occurrence, failure or loss, either at a plant or along a transportation route, resulting in a release of hazardous materials.
• acclimatization The physiological and behavioral adjustments of an organism to changes in its environment.
• Acco.oc® Ion exchange media by Colloid Environmental Technologies Co.

• accretion The increase in size of an inorganic body by the addition or accumulation of particles.
• ACCU® Air sampler by Rupprecht & Patashnick.
• Accuguard™ Automated pH electrode cleaning and calibration module by BIF.
• Accu-Mag Electromagnetic .ow meter by USFilter/Wallace & Tiernan.
• accumulation zone The upper part of a glacier where net gain in ice exceeds the net loss.
• accumulator A tank installed in a circulating water system to allow for .uctuations in .ow, temperature, pressure, or other variations in operation.
• AccuPac® Cross-corrugated surface media for biological wastewater treatment by Brentwood Industries, Inc.
• Accura-.o® Flumes for measuring .ows by Composite Structures.
• Accu-Tab™ Tablet chlorination system by Hammonds and PPG Industries, Inc..
• Accuvac Chemical reagents in vacuum vials for chemical analysis of .uids by Hach Co.
• ACE rule See “Any Credible Evidence rule (ACE rule).”
• acetaldehyde An organic chemical formed during the disinfection of water, most commonly associated with the use of ozone as disinfectant. Chemical formula is CH3CHO.
• acetic acid A weak, organic acid contained in vinegar and used in the manufacture of organic chemicals and plastics. Also called “ethanoic acid.” Chemical for­mula is CH3COOH.
• acetone A colorless, volatile liquid used in organic synthesis and as a commercial solvent. Chemical formula is CH3COCH3.
• ACFM Actual cubic feet per minute.
• ACFTD Air cleaner .ne test dust. Dust used to calibrate particle counters.
• ACGIH American Conference of Governmental Industrial Hygienists.
• ACH (1) See “air changes per hour (ACH).” (2) See “aluminum chlorohydrate (ACH).”
• ACI American Concrete Institute.
• acid (1) A substance that can react with a base to form a salt. (2) A substance that can donate a hydrogen ion or proton.
• acid deposition See “acid rain.”
• acid mine drainage Drainage of water from areas that have been mined for coal or other mineral ores, usually having a low pH due to contact with sulfur-bearing material.
• acid neutralizing capacity (ANC) Measure of the ability of water or soil to resist changes in pH.
• acid rain Precipitation having an unusually low pH, generally attributed to the absorption of sulfur dioxide pollution in air. Also known as “acid deposition.”
• acid shock The biological disruption of an aquatic system that results from rapid acidi.cation.
• acid-forming bacteria Microbes that can metabolize complex organic compounds under anaerobic conditions, leading to the production of methane.
• acidic The condition of water or soil that contains a suf.cient amount of acid substances to lower the pH below 7.0.

• acidity The capacity of an aqueous solution to neutralize a base.
• acidophil (1) A cell or substance easily stained by acid dyes. (2) An organism that has an af.nity for, and grows in, an acidic environment. Also spelled “acidophile.”
• ACL Alternate concentration limit.
• ACM Asbestos-containing material.
• ACM® Thin .lm composite reverse osmosis membrane by TriSep Corp.
• Acme Former screening equipment manufacturer.
• ACM-LP™ Low pressure thin .lm composite reverse osmosis membrane by TriSep Corp.
• ACMS™ Seawater reverse osmosis membrane by TriSep Corp.
• ACoE U.S. Army Corps of Engineers.
• Acousticair® Low noise blowers by Tuthill Pneumatics Group.
• ACP Air Carcinogen Policy.
• acre-foot The volume of water that would cover a one acre area one foot deep. Equivalent to approximately 1233.6 cubic meters or 325,900 gallons.
• acrolein An aldehyde compound used as a microbiocide in the manufacture of organic chemicals.
• Acro-Pac® Packaged seawater reverse osmosis system by Aqua-Chem, Inc.
• ACS-Plus High purity chemicals for laboratory use by Hach Co.
• ACT-100® Double wall .berglass laminated steel underground tank by Steel Tank Institute.
• ACT™ Combined aeration technologies by Aeration Industries, Inc.
• Acticarbone® Activated carbon by Elf Atochem North America, Inc.
• Acti.l® Packing media for biological reactors by Sanitaire Corp.
• Acti.o® High rate sedimentation process for water and wastewater treatment by USFilter/Krüger.
• Acti.oc™ Modular, high-rate water treatment plant by USFilter/General Filter.
• Actinomycetes A group of bacteria that share some features with fungi, and recognized as a source of musty or earthy odors in drinking water.
• activated alumina A partially dehydrated form of aluminum oxide frequently used as an adsorbent. Chemical formula is Al2O3.
• Activated Bio.lm Method Fixed .lm wastewater treatment system by JDV Equip­ment Corp.
• activated bio.lter A .xed .lm biological wastewater treatment process where a portion of the secondary sludge is returned to the reactor in.uent.
• activated carbon (AC) A highly adsorbent form of carbon used to remove dis­solved organic matter from water and wastewater or odors and toxic substances from gaseous emissions.
• activated charcoal See “activated carbon.”
• activated sludge The biologically active solids in an activated sludge process wastewater treatment plant.
• activated sludge process A biological wastewater treatment process where a mix­ture of wastewater and biologically enriched sludge is mixed and aerated to facilitate aerobic decomposition by microbes.
• activation energy The energy required to initiate a process or reaction.
• Activator Package wastewater treatment plant by Pollution Control, Inc.

• activator A chemical added to a pesticide to increase its activity.
• Activator III Oil recovery product by Sybron Chemicals, Inc.
• active ingredient In any pesticide product, the component that kills, or otherwise controls, target pests.
• active life The period of operation of a facility that begins with initial receipt of a solid waste and ends at completion of closure activities.
• active portion Any area of a facility where treatment, storage, or disposal opera­tions continue to be conducted.
• active solar heating A heating system that derives heat from the sun’s rays and incorporates active devices such as pumps or blowers to move heat from the point of collection to the point of storage or use.
• Activol™ Wastewater grease emulsi.er by Probiotic Solutions.
• Acumem Reverse osmosis product formerly offered by USFilter.
• Acumer® Water treatment polymers by Rohm and Haas, Co.
• acute exposure A single exposure to a toxic substance, usually lasting no longer than a day, which results in severe biological harm or death.
• acute toxicity A poisonous effect produced by a single short-term exposure which results in severe biological harm or death.
• Acutec Gas detection system by USFilter/Wallace & Tiernan.
• ACWA American Clean Water Association.
• ACWM (1) Asbestos-containing waste material. (2) See “asbestos-containing waste materials (ACUM).”
• AD Dry blending and dilution system by Komax Systems, Inc.
• ADA American Desalting Association. Formerly “NWSIA.”
• ADAM Acryloyl ethyl dimethyl amine.
• adaptation Changes in an organism’s structure or habits which help it adjust to its surroundings.
• Adcat™ Oxidation catalyst systems for air pollution control by Goal Line Envi­ronmental Technologies.
• Addigest® Package extended aeration wastewater treatment plant by Smith & Love­less, Inc.
• additive A chemical substance incorporated into another substance to improve or preserve its quality.
• additive mortality The total mortality caused by different factors affecting a pop­ulation for a given period of time including predation, .re, or catastrophes.
• add-on control device An air pollution control device such as carbon absorber or incinerator that reduces the pollution in an exhaust gas.
• adenosine diphosphate (ADP) A compound involved in the mobilization of energy in cellular metabolism. Energy is stored by adding a phosphate group to ADP to produce ATP.
• adenosine triphosphate (ATP) A high-energy phosphate compound that serves as the prime energy carrier in living organisms. Energy is released when ATP is converted to ADP and phosphate.
• adenovirus A waterborne pathogen that causes upper respiratory infections and gastroenteritis.
• ADF See “average daily .ow (ADF).”

• adhesion The force of molecular attraction between unlike molecules.
• ADI Acceptable daily intake.
• adiabatic lapse rate The constant rate at which temperatures decrease as altitude increases. In a dry atmosphere the dry adiabatic lapse rate (DALR) is approx­imately –1.00°C/100 m rise.
• adit A horizontal passageway into a mine to provide access or drainage.
• AdjustAir® Adjustable coarse bubble air diffuser by USFilter/Diffused Air Prod­ucts Group.
• Adjust-O-Pitch Mixing propellers with adjustable pitch blades by Walker Process Equipment.
• administrative order An EPA-issued order directing an individual, business, or other entity to take corrective action or refrain from an activity.
• admixture (1) A material or substance added in mixing. (2) A substance other than cement, aggregate, or water that is mixed with concrete.
• Ad-Ox Polishing scrubber for odor abatement by Pura.l, Inc.
• ADP See “adenosine diphosphate (ADP).”
• Adpec Horizontal vacuum .lter by Komline-Sanderson Engineering Corp.
• ADR (1) Accidental rectal discharge. (2) Alternative dispute resolution.
• ADROWPU® Water puri.cation unit by Zenon Environmental, Inc.
• Adsep™ Chromatographic process for separating organic and inorganic com­pounds by USFilter/Rockford.
• Adsolv Activated carbon VOC control system by CSM Worldwide/RaySolv.
• adsorbable organic halides (AOX) The gross measurement of all chlorinated organic compounds in an ef.uent.
• adsorbate A material adsorbed on the surface of another.
• adsorbent A material used to adsorb substances to its surface.
• adsorption The process of transferring a substance from a liquid to the surface of a solid where it is bound by chemical or physical forces.
• Adsorption Clari.er™ Up.ow buoyant media .occulator/clari.er by USFil­ter/Micro.oc.
• adulterants Chemical impurities or substances that by law do not belong in a food or pesticide.
• adulterated (1) Any pesticide whose strength or purity falls below the quality stated on its label. (2) A food, feed, or product that contains illegal pesticide residues.
• Advance® Chlorine gas feeder systems by Capital Controls Co.
• Advanced Fluidized Composting™ A combined biological and chemical sludge treatment process by USFilter/Industrial Wastewater Systems.
• advanced oxidation process (AOP) A process using a combination of disinfec­tants such as ozone and hydrogen peroxide to oxidize toxic organic compounds to nontoxic form.
• advanced secondary treatment Secondary wastewater treatment with enhanced solids separation.
• advanced treatment plant (ATP) A treatment facility using processes that pro­vide treatment to levels greater than that of a conventional plant.
• advanced wastewater treatment (AWT) Treatment processes designed to remove pollutants such as phosphorus, nitrogen, and a high percentage of suspended solids which are not adequately removed by conventional secondary treatment

• processes.
• advection The transfer of heat by horizontal currents of air.
• Advent® Package water treatment plant by In.lco Degremont, Inc.
• advisory A nonregulatory document that communicates risk information to those who may have to make risk management decisions.
• AEM Acoustic emission monitoring.
• aeolian deposit Soil deposited by the wind.
• Aeralater® Packaged iron and manganese removal system by USFilter/General Filter.
• aerated pile composting A composting method where municipal wastewater sol­ids are mixed with a bulking material and the mixture placed over a forced air ventilation system.
• aeration The addition of air or oxygen to water or wastewater, usually by mechan­ical means, to increase dissolved oxygen levels and maintain aerobic conditions.
• Aeration Engineering Resources Corp. Former name of Aercor product group of Sanitaire Corp.
• Aeration Panel™ Fine bubble membrane diffuser panel by Parkson Corp.
• aerator A device used to introduce air or oxygen into water or wastewater.
• Aerators, Inc. Former name of USFilter/Aerator Products.
• Aercor Aeration and packing products by Sanitaire Corp.
• Aer-Degritter Aerated grit removal system by USFilter/Headworks Products.
• AerFlare Air diffuser by Walker Process Equipment.
• Aergrid™ Floor grid aeration system by Aeration Technologies, Inc.
• Aermax® Fine pore aeration diffuser by Aeration Technologies, Inc.
• Aero-Accelator® Circular, packaged activated sludge treatment plant by In.lco Degremont, Inc.
• aeroallergen An allergen transported by air.
• aerobe An organism that requires free oxygen for respiration.
• aerobic Condition characterized by the presence of free oxygen.
• aerobic digestion Sludge stabilization process involving direct oxidation of bio­degradable matter and oxidation of microbial cellular material.
• aerobic treatment Process by which microbes decompose complex organic com­pounds in the presence of oxygen and use the liberated energy for reproduction and growth.
• Aeroburn Wastewater treatment plant by Walker Process Equipment.
• Aerocleve Former manufacturer whose product line is now offered by Chemineer, Inc.
• Aeroductor Aerated grit removal system by Lakeside Equipment Corp.
• Aero-Filter Rotary distributor by Lakeside Equipment Corp.
• Aer-O-Flo Wastewater treatment equipment product line by Purestream, Inc.
• aerogel A substance formed by the suspension of small bubbles of gas in a liquid or solid.
• Aero-Max Tubular membrane diffuser by Aeration Research Company.
• Aero-Mod® Wastewater treatment product line by Waterlink/Aero-Mod Systems.
• Aeropure Activated carbon vapor .ltration system by American Norit Company, Inc.

• AeroScrub Flue gas scrubber by Aeropulse, Inc.
• Aerosep® Multi-stage aerosol separation system by Kimre, Inc.
• aerosols A suspension of collodial particles in air or another gas.
• Aero-Surf Air driven rotating biological contactor by USFilter/Envirex.
• Aero-Terra-Aqua ATA Technologies, Inc.
• Aerotherm In-vessel composting system by Fair.eld Service Co.
• AerResearch Aeration diffuser product line by Aeration Research Company.
• Aershear™ Coarse bubble diffuser by Aeration Technologies, Inc.
• Aertec™ Air diffuser product line by Aeration Technologies, Inc.
• Aertube™ Static tube aerators by Aeration Technologies, Inc.
• Aethalometer™ An aerosol black carbon monitor for measuring agricultural burning,

• diesel emissions and speciation of .ne particles by Andersen Instruments, Inc. AF Series™ Backwashable .lter and carbon treatment units by Asahi America. AFC™ Advanced .uidized composting process by USFilter/Industrial Wastewater
• Systems. AFD Adjustable frequency drive. affected public The people who live and/or work near a hazardous waste site. af.uent stream A stream or river .owing into a larger river or lake. afforestation The process of establishing a forest where one did not previously
• exist. AFO Air fail open. AFOs Animal feeding operations. AFPA American Forest and Paper Association. Also called “AF&PA.” AfterBlend Output booster for chemical feed system by USFilter/Stranco. afterburner A device used to reduce air emissions by incinerating organic matter
• in a gas stream. aftercondenser A condenser installed as the last stage of an evaporator venting system to minimize atmospheric steam discharge. aftergrowth The increase of bacterial density in treated distribution water caused by growth of bacteria released from pipewall bio.lm and sediments. aftershock Any seismic tremor following a main earthquake event and originating
• at or near the same place. AFX™ Ozone instrumentation products by IN USA, Inc. agar A gelatinous substance extracted from a red algae, commonly used as a
• medium for laboratory cultivation of bacteria. agar plate A circular glass plate, containing agar or another nutrient-medium,
• used to culture microorganisms. AGC Association of General Contractors of America. age tank A tank used to store a chemical solution of known concentration for feed
• to a chemical feeder. Also called a day tank. agent Any substance, organism, or active force that produces an effect or change. Agent Orange A dioxin-containing toxic herbicide used as a defoliant during the
• Vietnam War. aggessive water Water having corrosive qualities. agglomerate To gather .ne particles into a larger mass.

• aggrade To build up the level or slope of a river bed or valley by the deposit of sediment.
• AGI Acute gastrointestinal illnesses.
• Agidisc® Disc .lter with integrated agitation system by Baker Process.
• Agisac Sock-type screening sack by Copa Group.
• AGMA American Gear Manufacturers Association.
• agrichemical Any inorganic, arti.cial, or manufactured chemical substances used in agricultural processes, usually in the form of fertilizers, herbicides, and pesticides.
• agricultural pollution Farming wastes, including runoff and leaching of pesti­cides and fertilizers; erosion and dust from plowing; improper disposal of animal manure and carcasses; crop residues; and debris.
• agrochemical A substance such as a fertilizer or insecticide used in agriculture.
• agro-ecosystem Land used for crops, pasture, and livestock; the adjacent uncul­tivated land that supports other vegetation and wildlife; the associated atmo­sphere; and the underlying soils, groundwater, and drainage networks.
• agronomy Branch of agriculture that deals with the raising of crops and the care of the soil.
• AHERA Asbestos Hazard Emergency Response Act.
• AhlFloat™ Dissolved air .otation by USFilter/Industrial Wastewater Systems.
• Ahlstrom Aqua.ow Former name of wastewater equipment product group acquired by USFilter/Industrial Wastewater Systems.
• AhlSurf™ Surface aerator by USFilter/Industrial Wastewater Systems.
• A-horizon Topsoil, or the uppermost layer of soil, containing the highest accu­mulation of mineral and organic matter.
• AHS See “aquatic humic substances (AHS).”
• AIChE American Institute of Chemical Engineers.
• AIDS (Acquired Immune De.ciency Syndrome) A usually fatal disease in which the human body can no longer defend itself against infections. AIDS is caused by the HIV retrovirus which is transmitted by the exchange of body .uids.
• AIHA American Industrial Hygiene Association.
• air The mixture of gases, primarily oxygen and nitrogen, that surrounds the earth and forms its atmosphere.
• air binding (1) A condition where air enters .lter media and harms both the .ltration and backwash processes. (2) The obstruction of water .ow in a pipeline or pump due to the entrapment of air.
• air bound See “air binding.”
• air changes per hour (ACH) The movement of a volume of air in a given period of time; if a building has one air change per hour, it means that all of the air in the building will be replaced in a one-hour period.
• Air Comb® Coarse bubble diffuser by Amwell, Inc.
• air contaminant Smoke, dust, fume, gas, odor, mist, radioactive substance vapor, pollen, or any combination thereof.
• air curtain A vertical barrier of air bubbled upward through water to contain oil spills or discourage .sh from entering polluted water.

• air diffuser A device designed to transfer atmospheric oxygen into a liquid.
• air gap An open vertical gap or empty space that separates drinking water supply from another water system in a treatment plant or other location to protect it from contamination by back.ow or backsiphonage.
• Air Grid™ Sand .lter air scour system by Roberts Filter Group.
• air lock The condition that occurs when air accumlates in a high point of a pipeline, reducing or blocking the .ow of water.
• air mass A large body of air that has uniform properties such as temperature and humidity.
• air padding Pumping dry air into a container to assist with the withdrawal of liquid or to force a liqui.ed gas such as chlorine out of the container.
• air pollutant Airborne gases, liquids, or solids that may be hazardous to animal or plant life.
• air pollution The presence in the atmosphere of any airborne gases, liquids, or solids that may be hazardous to animal or plant life.
• air pollution episode A period of abnormally high concentration of air pollutants, often due to low winds and temperature inversion, that can cause illness and death.
• air purifying respirator (APR) A respirator that uses physical and/or chemical means to .lter air breathed by the user.
• Air Quality Control Region Federally designated area that is required to meet and maintain federal ambient air quality standards.
• air quality criteria The levels of pollution and lengths of exposure above which adverse health and welfare effects may occur.
• air quality related value (AQRV) A value referring to the reduction in visibility that may be caused by a new air emission.
• Air Quality Standards The level of pollutants prescribed by regulations that may not be exceeded during a given time in a de.ned area.
• air scour The agitation of granular .lter media with air during the .lter backwash cycle.
• Air Seal Coarse bubble diffuser by Jet, Inc.
• Air Shuttle Wastewater aeration system by Meurer Industries, Inc.
• air stripping The process of removing volatile and semivolatile contaminants from liquid by passing air and liquid countercurrently through a packed tower.
• air toxics Any air pollutant for which a NAAQS does not exist that may reasonably be anticipated to cause cancer, developmental effects, reproductive dysfunc­tions, neurological disorders, heritable gene mutations, or other serious or irreversible chronic or acute health effects in humans.
• Airamic® Air/gas diffuser by Ferro Corp.
• AiRanger Tank level measurement system by Milltronics, Inc.
• Airbeam™ Aluminum aeration basin cover by Enviroquip, Inc.
• Airbrush™ Rotor aerator by United Industries, Inc.
• AirCirc™ Assembly used to maintain the vortex within a wastewater degritter by Fluidyne Corp.
• Airco Former name of BOC Gases.
• Aircushion Flotation clari.er by Wil.ey Weber, Inc.

• Aire-O2 ® Propeller aspirator aerator by Aeration Industries, Inc.
• Air-Grit Aerated grit removal system by Walker Process Equipment.
• AirJection™ Aeration system by Mazzei Injector Corp.
• AirLance™ In-vessel composting technology by CBI Walker, Inc. (licensee) and American Bio Tech, Inc. (licensor).
• airlift A device for pumping liquid by injecting air near the bottom of a riser pipe submerged in the liquid to be pumped, lowering the speci.c gravity of the .uid mixture, and allowing it to rise up the riser pump.
• Airmaster Floating aerator by Airmaster Aerator.
• AirMASTER Wet particulate scubber by Fen-Tech Environmental, Inc.
• Air-Mix® Pulsed bed .lter surface cleaning process by USFilter/Zimpro.
• Airmizer Air diffuser by USFilter/Diffused Air Products Group.
• Airo.o™ Rotor aerator by S&N Airo.o, Inc.
• Air-O-Lator® Floating aerator by Air-O-Lator Corp.
• AiroPump Air lift pump by Walker Process Equipment.
• AirOXAL® Pure oxygen process by Air Liquide America.
• AirRaider™ MTBE pump and treat system by Product Level Control, Inc.
• AirRide Density contolling system for compost in-feed by the former Waste Solu­tions.
• Airsep Aerated grit collector system by USFilter/Aerator Products.
• AirSep® Pressure swing adsorption oxygen systems by AirSep Corp.
• AirTainer™ Tank cover by NuTech Environmental Corp.
• air-to-cloth ratio Bag house application criteria which is the ratio of the air .ow line to net cloth area.
• air-to-water ratio Air stripping application criteria indicating the volume of air required per volume of water to remove volatile contaminants.
• Airvac® Vacuum sewage collection system by Airvac, Inc.
• AISC American Institute of Steel Construction.
• AISI American Iron and Steel Institute.
• AIWPS Advanced Integrated Wastewater Pond System.
• Akta Klor Sodium chlorite solution by Vulcan Performance Chemicals.
• Aktivox Selective oxidant with speci.city for sul.des by Vulcan Performance Chemicals.
• AL Acceptable level.
• alabaster A compact, .ne-grained gypsum material.
• alachlor A herbicide used mainly to control weeds in corn and soybean .elds and marketed under the trade name Lasso.
• ALAPCO Association of Local Air Pollution Control Of.cers.
• Alar Trade name for a pesticide used primarily to make apples redder, .rmer, and less likely to fall off trees prematurely.
• ALARA As low as reasonably achievable.
• Albrivap High temperature additive for evaporators by Albright & Wilson Americas.
• Alco.x® Inorganic coagulant by Ciba Specialty Chemicals.
• alcohol A class of compounds containing the hydroxyl group OH.
• aldehyde A class of organic compounds produced by the oxidation of alcohols containing a CHO group including formaldehyde and acetylaldehyde.

• aldicarb An insecticide made from ethyl isocyanate and sold under the trade name Temik.
• aldrin An insecticide and suspected carcinogen which has been banned for agri­cultural use by the U.S. Environmental Protection Agency (EPA).
• alga The singular form of “algae.”
• algae Primitive, free-.oating, plant-like aquatic organisms whose biological activ­ity affect the pH and dissolved oxygen content in a water body.
• Algae Sweep Automation Automated clari.er algae sweep system by Ford Hall Co., Inc.
• AlgaeMonitor On-line .uorometer to monitor relative algae levels in a water system by Turner Designs.
• algal bloom A rapidly reproducing .oating colony of algae that may cover a stream, lake, or reservoir, creating a nuisance condition.
• AlgaSORB® Ion exchange medium for heavy metal removal by Bio-Recovery Systems, Inc.
• algicide Any substance used to kill algae. Also “algaecide.”
• aliphatic compounds Organic compounds with carbon atoms arranged in a straight or branched chain, rather than a ring.
• aliquot The amount of a sample used for analysis.
• Alizair® Fixed growth biotreat system for removal of odorous compounds from wastewater by USFilter/Krüger and OTV.
• alkali A substance with highly basic properties.
• alkali metals The elements lithium, sodium, potassium, rubidium, and cesium.
• alkaline Water containing suf.cient amounts of alkalinity to raise the pH above 7.0.
• alkaline soil Soil with a pH greater than 7.0.
• alkalinity The ability of a water to neutralize an acid due to the presence of carbonate, bicarbonate, and hydroxide ions.
• Alkalinity First™ Sodium bicarbonate by Church & Dwight Co. Inc.
• alkaloid Any of a group of organic compounds containing nitrogen and having alkaline properties including caffeine, cocaine, morphine, nicotine, and strychnine.
• alkalosis Abnormal condition in the body resulting from an excess alkalinity and an increased blood and tissue pH, often caused by exposure to low-oxygen air found at high altitudes.
• Alka-Pro® Process control system for biological wastewater treatment systems by USFilter/Davco.
• All Climate™ Field-erected package wastewater plant by USFilter/Davco.
• allergen A substance inducing an allergic state or reaction.
• allergy A hypersensitivity to a particular substance such as food, pollen, or dust that causes the immune system to overreact to the substance.
• Allied Colloids Former name of Ciba Specialty Chemicals.
• Allis-Chalmers Former name of A-C Compressor Corp.
• Allison Internally fed rotating drum screen by KRC (Hewitt) Inc.
• allotropy The ability of an element to exist naturally in different forms in the same solid, liquid, or gaseous state.

• alluvial soil Soil formed of material that was carried by .owing water before being deposited.
• alpha factor The ratio of oxygen transfer coef.cients for water and wastewater at the same temperature and pressure; used in the sizing of aeration equipment.
• alpha particle A positively charged atomic particle composed of two neutrons and two protons released by some atoms undergoing radioactive decay.
• alpha radiation A stream of positively charged particles released from radioactive isotopes.
• alpha ray A stream of particles emitting from the nucleus of a helium atom undergoing disintegration.
• alpine tundra An ecosystem found at high altitudes, above the timberline, char­acterized by mosses, lichens, and low-growing herbaceous plants.
• ALR Action leakage rate.
• alternative energy Energy obtained from sources other than traditional fossil fuels or nuclear energy, and which are usually renewable and nonpolluting. Alter­native energy sources include solar energy, wave power, wind power, geother­mal power, and biomass fuels.
• alum Common name for aluminum sulfate, frequently used as a coagulant in water and wastewater treatment. Chemical formula is Al2(SO4)3.
• alum sludge Sludge resulting from treatment process where alum is used as a coagulant.
• Alumadome Self supporting aluminum covers for circular tanks by Conservatek Industries, Inc.
• Alumavault Self supporting aluminum covers for rectangular tanks by Conser­vatek Industries, Inc.
• alumina A form of aluminum oxide, also called “corundum” or “emery.” Chemical formula is Al203.
• aluminum A lightweight, nonferrous metal with good corrosion resistance and electrical and thermal conductivity. Chemical symbol is Al.
• aluminum chlorohydrate (ACH) Water treatment coagulant.

• aluminum sulfate See “alum.”
• AlumStor Modular liquid storage tank and feed system by ModuTank, Inc.
• Alundum Porous diffuser dome by Sanitaire Corp.
• Alusil 70™ Custom-activated zeolites by Selecto, Inc.
• amalgam An alloy of mercury with one or more other metals. Silver amalgam is used as a dental .lling.
• Amazon™ Pulse jet baghouse .lter bags by W.L. Gore & Associates, Inc.
• Amberjet® Ion exchange resins by Rohm & Haas, Co.
• Amberlite® Ion exchange resins by Rohm & Haas, Co.
• Amberpack™ Ion exchange resins by Rohm & Haas, Co.
• Ambersomb® Carbonaceous adsorbent for VOC removal by Rohm & Haas Co.
• ambient air quality A general term used to describe the condition of the outdoor air.
• amendment Organic material or bulking agent such as wood chips or sawdust added to municipal solids in a composting operation to promote uniform air .ow.

• Amer.oc® Polyelectrolyte used to enhance liquid/solid separation by Ashland Chemical, Drew Industrial.
• America Norit Former name of Norit Americas Inc.
• American Well Works Former name of Amwell Inc.
• Ameroid Polyelectrolyte used to enhance liquid/solid separation by Ashland Chemical, Drew Division.
• Amersep® Coagulants and metal precipitants used in water and wastewater treat­ment by Ashland Chemical, Drew Industrial.
• amines A group of compounds that are derivatives of ammonia with a hydrocarbon group replacing one or more of the hydrogen atoms.
• amino acid A group of organic acids containing an amino group (NH2) and a carboxyl group (COOH) that link together to form the proteins necessary for all life.
• Aminodan™ Process Process water treatment and recovery process by Biothane Corp.
• AmmonAsorb™ Activated carbon product by Waterlink/Barnebey Sutcliffe.
• ammonia A compound of hydrogen and nitrogen that occurs extensively in nature. Chemical formula is NH3.
• ammonia nitrogen The quantity of elemental nitrogen present in the form of ammonia and the ammonium ion.
• ammoniator A device used to feed gaseous ammonia.
• ammoni.cation Bacterial decomposition of organic nitrogen to ammonia.
• ammonium ion A form of ammonia found in solution, the ion NH4+.
• ammonium nitrate A cystalline salt used as a source of nitrogen in the manufac­ture of some fertilizers and explosives. Chemical formula is NH4NO3.
• amoeba A single-celled protozoan microbe. Also spelled “ameba.”
• amoebiasis See “amoebic dysentery.” Also spelled “amebiases.”
• amoebic dysentery A form of dysentery caused by a protozoan parasite, usually resulting from poor sanitary conditions and transmitted by contaminated food or water. Also spelled “amebic dysentery.”
• amoebicide Any substance used to kill amoebas, either medicinally for treatment of amoebic dysentery or to sterilize water. Also spelled “amebicide.”
• amorphous Non-crystalline, having no de.nite shape or form.
• AMOS Air Management Oversight System.
• amperometric titrator Titration device containing an internal indicator or elec­trometric device to show when the reactions are complete.
• amphibian (1) A member of the Amphibia class of cold blooded, scaleless verte­brates which includes frogs and salamanders. (2) A plant or animal that can live both on land or in water.
• Amphidrome™ Fixed-.lm sequencing batch biological .lter by Tetra Process Technologies.
• Ampho-Mag™ Magnesia compound to absorb and buffer chemical spills by Pre­mier Chemicals.
• amphoteric Capable of reacting in water either as a weak acid or weak base.
• AMSA Association of Metropolitan Sewer(age) Agencies.

• anabatic wind A localized wind that .ows up valley or mountainous slopes, usually in the afternoon, caused by the replacement of cool valley air with the warmer, heated air above it.
• anabiosis A temporary state of suspended animation undergone by some aquatic organisms to survive periods of drought.
• anabolism The process in a plant or animal in which food is metabolized into complex compounds such as protein and living tissue.
• anaerobe An organism that can thrive in the absence of free oxygen.
• anaerobic Condition characterized by the absence of free oxygen.
• anaerobic digestion Sludge stabilization process where the organic material in biological sludges are converted to methane and carbon dioxide in an airtight reactor.
• Anaerobic Selector Process Biological system for phosphorus and BOD removal by USFilter/Davco.
• Analite Portable turbidimeters by Advanced Polymer Systems.
• analyte The chemical for which a sample is analyzed.
• ANC See “acid neutralizing capacity (ANC).”
• An-CAT® Polymer processing control unit by Norchem Industries.
• ancillary equipment Devices such as piping, .anges, valves, and pumps which are used in conjunction with treatment process or system.
• Anco Batch mixers by Enviropax, Inc.
• anemometer An instrument used to measure the force or velocity of wind.
• aneroid barometer An instrument used to measure atmospheric pressure which operates on the movement of a thin metal plate rather than the rise and fall of mercury.
• angle of repose The maximum angle the inclined surface of a loosely divided material can make with the horizontal.
• Angstrom (.) A unit of measure equivalent to one ten-thousandth of a micron.
• anhydride A chemical compound derived by the elimination of water.
• anhydrite See “calcium sulfate.”
• anhydrous A compound or substance that does not contain water.
• animal unit (AU) A unit for establishing grazing pressures from different kinds of grazing animals which consume similar kinds of forage, where 1AU is equivalent to the weight of 1 cow and 1 calf set at 454 kg.
• anion A negatively charged ion that migrates to the anode when an electrical potential is applied to a solution.
• anion exchange An ion exchange process in which anions in solution are exchanged for other anions bound to an ion exchange resin or medium.
• anionic polymer A polyelectrolyte with a net negative electrical charge.
• Anitron Biological .uidized bed wastewater treatment system by USFilter/Krüger.
• ANM™ Nano.ltration softening membrane by TriSep Corp.
• annelid A wormlike organism, including earthworms and leeches, which have long, segmented bodies.
• Annubar® Mass .ow monitoring system by Dieterich Standard.
• anode The positive electrode where current leaves an electrolytic solution.

• anodic protection Electrochemical corrosion protection achieved through the use of an anode having a higher electrode potential than the metal to be protected.
• anoxia A condition in which the blood oxygen level is less than normal.
• anoxic Condition characterized by the absence of free oxygen.
• ANOX-R Advanced treatment industrial wastewater treatment system by USFil­ter/Davco.
• ANPRM Advance Notice for Public Rulemaking. An EPA program for holding public forums for potential changes to the federal Water Quality Standard regulations.
• ANSI American National Standards Institute.
• antagonism Interference or inhibition of the effect of one chemical by the action of another.
• antarctic Characteristic of the region, climate, or vegetation south of the Antarctic Circle.
• Antarctic Circle An imaginary circle parallel to the equator at latitude 66°34. south.
• Anthozoa A class of saltwater polyps including corals and sea anemones.
• anthracite A hard, black coal containing a high percentage of .xed carbon, a low percentage of volatile matter, and burns with little or no smoke.
• anthracosis A lung disease more commonly known as “black lung disease.”
• Anthra.lt® Filter anthracite by Uni.lt Corp.
• anthropodust Fugitive dust generated from human activities.
• anthropogenic climate change Human-induced global warming caused primarily by carbon dioxide, methane, and nitrous oxide emissions from engine exhausts, as well as respiration of humans and animals.
• anthropogenic compounds Compounds created by human beings, often relatively resistant to biodegradation.
• antichlors Reagents such as sulfur dioxide, sodium bisul.te, and sodium thiosul­fate which can be used to remove excess chlorine residuals from water by conversion to an inert salt.
• anti-degradation clause See “prevention of signi.cant deterioration (PSD).”
• antifoam agent A surface active agent used to reduce or prevent foaming.
• antifoulant An additive or dispersant that prevents fouling and/or the formation of scale.
• antigen A substance capable of stimulating an immune response.
• antiknock additive A compound, usually tetraethyl lead, added to gasoline to minimize engine pre-ignition and its’ accompanying knocking or pinging. Pollution from the release of these compounds in auto emissions led to the introduction of nonleaded gasoline.
• antioxidant A substance that slows down or prevents oxidation of another substance.
• antiscalant An additive that prevents the formation of inorganic scale.
• Any Credible Evidence rule (ACE rule) Another name for EPA Clean Air Act “Credible Evidence rule.”
• AOB Ammonia-oxidizing bacteria.
• AOC See “assimilable organic carbon (AOC).”

• AOPs See “advanced oxidation processes (AOP).”
• AOT Advanced oxidation technologies.
• AOX See “adsorbable organic halides (AOX).”
• APCA Air Pollution Control Association.
• APER Air pollution emissions report.
• APF See “assigned protective factor (APF).”
• APHA American Public Health Association.
• API American Petroleum Institute.
• API gravity An index inversely related to speci.c gravity used to identify liquid hydrocarbons.
• API separator Rectangular basin in which wastewater .ows horizontally while free oil rises and is skimmed from the surface.
• APOVAC® Anti-pollution vacuum system for solvent recovery by Rosenmund, Inc.
• apparent color The color in water caused by the presence of suspended solids.
• approach velocity The average water velocity of .uid in a channel upstream of a screen or other obstruction.
• APR See “air purifying respirator (APR).”
• APTI Air Pollution Training Institute.
• APWA American Public Works Association.
• AQCCT Air-quality criteria and control techniques.
• AQCP Air Quality Control Program.
• AQCR Air Quality Control Region.
• AQRV See “air quality related value (AQRV).”
• AQTX Aquatic toxicity.
• Aqua Bear Medium density foam pipeline cleaners by Girard Industries, Inc.
• Aqua Criss Cross Medium density coated foam pipeline cleaners by Girard Indus­tries, Inc.
• Aqua Guard® Self cleaning bar screen by Parkson Corp.
• Aqua Pigs™ Polyurethane foam pipeline cleaners by Girard Industries, Inc.
• Aqua Swab Soft polyurethane pipeline cleaners by Girard Industries, Inc.
• Aqua UV™ Ultraviolet water disinfection systems by Trojan Technologies, Inc.
• Aqua-4™ Surface water treatment plant by Smith & Loveless, Inc.
• AquaABF™ Traveling bridge type automatic backwash package .lter by Aqua-Aerobic Systems, Inc.
• Aquabelt® Gravity belt thickener by Ashbrook Corp. (U.S.) Simon-Hartley, Ltd. (U.K.).
• AquaCalc Open channel .ow computer by JBS Instruments.
• AquaCAM-D Aerator/mixer/decanter for use in sequencing batch reactor by Aqua-Aerobic Systems, Inc.
• Aqua-Carb Activated carbon by USFilter/Westates.
• Aqua-Cat® Sul.de conversion process to control odors by USFilter/Gas Technol­ogies.
• Aqua-Cell™ Package water treatment plant by WesTech Engineering Inc.
• Aquaclaire™ Wastewater treatment systems by DAS International, Inc.
• Aquacode Membrane vessels by Spaulding Composites Co.

• aquaculture The managed production of .sh or shell.sh in a pond or lagoon.
• AquaDDM® Direct drive mixers by Aqua-Aerobics Systems, Inc.
• AquaDecant® Floating decanter by AquaTurbo Systems.
• Aquadene™ Corrosion and scale control products by Stiles-Kem Division, Met

• Pro Corp. AquaDisk™ Woven cloth tertiary .lter by Aqua-Aerobic Systems, Inc. Aquafeed® Reverse osmosis antiscalants by B.F. Goodrich Co. Aqua-Fer™ Well water treatment plant designed for iron removal by Smith &
• Loveless, Inc. Aqua-Fix™ Dissolved ionic contaminant removal system by ATA Technologies Corp. Aqua.ow Former name of product group acquired by USFilter/Industrial Waste­
• water Systems. Aqua-Jet® Direct drive aerators by Aqua-Aerobics Systems, Inc. Aqua-Lator® High speed .oating aerator by USFilter/Aerator Products. AquaLift® Screw pump by Parkson Corp. Aquamag® Magnesium hydroxide by Premier Chemicals. AquaMax™ Desalination evaporator antiscalant by BetzDearborn, Inc. Aquamite® Electrodialysis water treatment systems by Ionics, Inc. AquaMJA™ Manifold jet aerator by Aqua-Aerobic Systems, Inc. Aquaport® Seawater desalination system by Ambient Technologies, Inc. Aquaray® Ultraviolet disinfection system by In.lco Degremont, Inc. Aquaritrol® Coagulant control system using a programmable controller by USFil­
• ter/Micro.oc. Aquarius® Modular water treatment plant by USFilter/Micro.oc. AquaSBR® Sequencing batch reactor by Aqua-Aerobics Systems, Inc. Aquascan On-line VOC monitor by Sentex Systems, Inc. Aqua-Scrub™ Powdered activated carbon adsorption system by USFilter/Westates. AquaSEAL™ Sequencing extended aeration lagoon system by Aqua-Aerobics
• Systems, Inc. Aqua-Sensor Control system for water softener regeneration by Culligan Interna­
• tional Corp. Aquashade® Aquatic plant growth control by Applied Biochemists, Inc. Aqua-Shear Mixer by Flow Process Technologies, Inc. Aquasorb® Carbon adsorption treatment systems by Hadley Industries. Aquasource® Membrane system by In.lco Degremont, Inc. Aquaspir® Shaftless dewatering screw by Andritz-Ruthner, Inc. Aquastore® Storage tanks by A.O. Smith Engineered Storage Products. Aquatair Packaged biological wastewater treatment plant by BCA Industrial Con­
• trols, Ltd. Aquatec® Solid media contact .lter vessels by Colloid Environmental Technolo­
• gies Co. Aquatech Systems Former name of Aqualytics, Inc. aquatic humic substances (AHS) Humic substances in true solution that exhibit
• colloidal properties. Aquatreat™ Sequencing batch reactor by EnviroSystems Supply.

• Aqua-Trim™ Tray-type air stripper by Delta Cooling Towers, Inc.
• AquaTurbo® Surface aerator and mixer products by AquaTurbo Systems.
• Aquavap Vapor compression type evaporator by Licon, Inc.
• Aqua-View Particle measuring system by Particle Measuring Systems, Inc.
• Aquaward® Tablet feeder disinfection system by Exceltec International Corp.
• Aquazur V® Rapid sand gravity .lter by In.lco Degremont, Inc.
• aqueduct A conduit for carrying running water.
• aqueous Something made up of, similar to, or containing water.
• aqueous chlorine Term used to describe chlorine or chlorine compounds dis­
• solved in water, often mistakenly called “liquid chlorine.” aqueous solution A solution in which water is the solvent. aquiclude A low-permeability underground rock formation that absorbs water
• slowly but will not allow its free passage. aquifer A subsurface geological formation containing a large quantity of water. aquifuge An underground layer of impermeable rock that will not allow the free
• passage of groundwater. Aquilair® Oxidation process for removal of VOC compounds from wastewater by
• USFilter/Krüger (North America) and OTV. AQuit™ Sul.de control product by USFilter/Davis Process. Aquox™ Potassium permanganate by Nalon Chemical, distributed by American
• International Chemical, Inc. arable Land capable of being farmed. ARAR Applicable or relevant and appropriate requirements. Cleanup standards,
• control standards and other substantive environmental protection requirements,
• criteria, and limitations promulgated under federal, state, and local laws. Arc Screen™ Self cleaning curved bar screen by In.lco Degremont, Inc. ARCC American Rivers Conservation Council. Archimedes’ principle The principle of buoyancy which states that the force on
• a submerged body acts vertically upward through the center of gravity of the
• displaced .uid and is equal to the weight of the .uid displaced. Archimedes’ screw pump See “screw pump.” archipelago A group or chain of many islands. arctic Characteristic of the region, climate, or vegetation north of the Arctic Circle. Arctic Circle An imaginary circle parallel to the equator at latitude 66°34. north. Arcticaer High speed surface aerator with submersible motor by USFilter/Aerator
• Products.
• area source Any small source of non-natural air pollution that is released over a relatively small area but which cannot be classi.ed as a point source, including vehicles and other small engines, small businesses and household activities.
• Argo Scienti.c Former name of BetzDearborn-Argo District.
• ARI Sulfur recovery and odor control product line by USFilter/Gas Technologies.
• ARI See “average rainfall intensity (ARI).”
• Aria™ Water treatment system by Pall Corp.
• Aries™ Filtration air scour technology by Roberts Filter Group.
• arithmetic mean The sum of a set of observations divided by the number of

• observations.

• Arm & Hammer® Sodium bicarbonate by Church & Dwight Co. Inc.
• Armco Former sluice gate manufacturer acquired by Hydro Gate Corp.
• Arna® Ultraviolet disinfection system by Arlat, Inc.
• aromatics A group of hydrocarbon compounds, including benzene, containing a closed ring structure.
• array (1) A staged arrangement of membrane elements in a system. (2) A group of solar collection devices arranged in a suitable pattern to ef.ciently collect solar energy.
• Arro-Care® Reverse osmosis maintenance and support services by USFilter/Rock­ford.
• Arro-Cleaning® Membrane care services by USFilter/Rockford.
• Arrowhead® Water treatment product line by USFilter/Rockford.
• arroyo A stream or watercourse that is often dry.
• ARS™ Air regulated siphon by John Meunier, Inc.
• arsenic A naturally occurring element that is toxic to humans at very low levels. Chemical formula is As.
• arsenicals Pesticides containing arsenic.
• Artco Applied Regenerative Technologies Co.
• artesian water Bottled water from a well that taps a con.ned aquifer which is located above the normal water table.
• artesian well A well with suf.cient pressure to produce water without pumping.
• arthropod Any of the largest phylum of invertebrate animals including insects and crustaceans having segmented bodies, exoskeletons, and jointed legs occurring in pairs.
• Arus Andritz Former name of Andritz-Ruthner, Inc.
• ASA Algae sweep automation system by Ford Hall Co., Inc.
• ASB Aerated stabilization basin.
• asbestos A mineral .ber, positively identi.ed as a carcinogen, that does not con­duct heat or electricity and formerly in wide use in the building industry for thermal insulation, soundproo.ng, roo.ng, and electrical insulation.
• asbestos cement pipe Pipe manufactured of a mixture of asbestos .ber and Port­land cement.
• asbestos-containing material Construction materials that contain more than one percent asbestos.
• asbestos-containing waste materials (ACWM) Mill tailings or any waste that contains commercial asbestos and is generated by a source covered by the Clean Air Act Asbestos NESHAPS.
• asbestosis A chronic lung disease caused by exposure or inhalation of asbestos .bers.
• as-built drawings The original plans and speci.cations prepared for construction and corrected to re.ect how a facility was actually built or installed.
• A-scale sound level (dBA) A modi.cation of the decibel scale that approximates the sensitivity of the human ear used to note the instensity or annoyance of noise pollution.
• ASCE American Society of Civil Engineers.
• Asdor Former name of USFilter/Asdor.

• ASDWA Association of State Drinking Water Administrators.
• aseptic The state of being free of pathogenic organisms.
• ash The nonvolatile inorganic solids that remain after incineration.
• Ashaire Aerator product line by USFilter/Aerator Products.
• Ashbrook-Simon-Hartley Former name of Ashbrook Corp.
• Ash.x™ A process to stabilize heavy metals in sludge and ash by Ashland Chem­ical, Drew Industrial.
• ASHRAE American Society of Heating, Refrigeration, and Air Conditioning Engineers.
• Asiatic clam A fresh water clam originally found in Southeast Asia and introduced in the U.S. in 1938.
• ASME American Society of Mechanical Engineers.
• Aspergillus fumigatus Airborne fungi that may result from composting opera­tions which may cause human ear, lung, and sinus infections.
• asphalt-rubber A mixture of ground rubber and bituminous concrete used as a pavement interlayer to reduce stress and prevent cracking.
• asphyxiant A vapor or gas such as carbon monoxide that can cause unconscious­ness or death by suffocation.
• Aspi-Jet™ Aspirating aerator by Aqua-Aerobic Systems, Inc.
• aspirating aerator Aeration device using a motor driven propeller to draw atmo­spheric air into the turbulence caused by the propeller to cause the formation of small bubbles.
• aspirator A hydraulic device that creates a negative pressure by forcing liquid through a restriction and increasing the velocity head.
• ASQC American Society for Quality Control.
• ASR See “atmosphere supplying respirator (ASR).”
• assay A test for a particular chemical or effect.
• assigned protective factor (APF) Respirator designation indicating how much contaminant will be reduced with proper respiratory .t and wear. An APF of 5 indicates that if a cubic meter of air contains 10 mg of contaminant, the effective exposure would be 10/5 or 2 mg/cu m.
• assimilable organic carbon (AOC) The portion of dissolved organic carbon that is easily used by microbes as a carbon source.
• assimilation The ability of a body of water to purify itself of pollutants.
• assimilative capacity The ability of a water body to receive wastewater and toxic materials without deleterious effects on aquatic life or the humans who con­sume the water.
• AST Aboveground storage tanks.
• ASTM American Society for Testing and Materials.
• Astrasand® Continuously cleaned sand .lter by Astraco Water Engineering.
• Astraseparator® Inclined plate settler by Astraco Water Engineering.
• asymmetric membrane Membranes that are not reversible and can only desali­nate ef.ciently in one direction.
• Asymmetrix™ Membrane cartridge .lter by USFilter/Filtration & Separation.
• AT® Ozone generator by Ozonia North America.
• ATAD See “autothermal thermophilic aerobic digestion (ATAD).”

• Atara Former manufacturer of digester gas mixing equipment whose product line
• was acquired by In.lco Degremont, Inc. ATD™ Autotherm aerobic sludge digestion system by CBI Walker, Inc. Athos Wet air oxidation process by USFilter/Krüger (North America) and OTV. ATI Analytical Technology, Inc. ATL® Aero Tec Laboratories, Inc. Atlantes Chemical Systems Former name of Hof.and Environmental, Inc. ATLAS™ Advanced technology lagoon aeration system by Environmental
• Dynamics Inc. atm See “atmosphere.” atmometer An instrument used to measure the evaporative capacity of the air. atmosphere (1) The gaseous region that surrounds the earth. (2) A unit of pressure
• equal to 1.0333 kg/sq cm or 14.7 psi. Abbreviated “atm.” atmosphere supplying respirator (ASR) A respirator which supplies air or oxy­
• gen to the user. atmospheric corrosion Corrosion resulting from exposure to the atmosphere. atmospheric pressure The force exerted by the weight of the atmosphere above
• the point of measurement. At sea level, this pressure equals 101.3 kPa
• (14.7 psi), 760 mm (29.9 inches) of mercury column, or 10.3 m (33.9 feet) of
• water column. Atochem Former name of Elf Atochem North America, Inc. atoll A circular reef enclosing a shallow lagoon. atom The smallest unit of an element that retains the characteristics of that element. Atomerator® Pressure aerator for iron oxidation by USFilter/General Filter. atomic absorption spectrophotometry (AA) A highly sensitive instrumental
• technique for measuring trace quantities of elements in water. atomize To divide a liquid into extremely .ne particles. atomizer An instrument through which a liquid is sprayed to produce a .ne mist. ATP (1) Average transmembrane pressure. (2) See “adenosine triphosphate
• (ATP).” (3) See “advanced treatment plant (ATP).” ATP™ Aerobic thermophilic process sludge treatment system by CBI Walker, Inc. ATS™ Sorbent media product line by Engelhard Corp. ATSDR Agency for Toxic Substances and Disease Registry. attached growth process See “.xed .lm process.” attainment area A geographic area in which the levels of a criteria air pollutant
• meet the health-based National Ambient Air Quality Standard for that pollutant. attenuation The process by which a compound is reduced in concentration over time, through absorption, adsorption, degradation, dilution, and/or transformation. attractant A chemical or agent that lures insects or other pests by stimulating
• their sense of smell. AU See “animal unit (AU).” Auger Monster® Modular screen/grinder/solids removal unit for wastewater head-
• works system by JWC Environmental. Aurora UV™ Ultraviolet disinfection system by Calgon Carbon Corp. Austgen-Biojet Former name of ABJ product group of Sanitaire Corp. Auto5™ Stack sampling system by Andersen Instruments, Inc.

• AutoBelt Rotary vacuum .lter formerly offered by Walker Process Equipment. autochthonous A rock formation, organic matter, or substance that is produced
• or originates in the place where it is found. autoclave A device that sterilizes materials by exposure to pressurized steam. Auto-Clean Dissolved oxygen sensor by Analytical Technology, Inc. Auto-Cleanse Self-cleaning pump station with differential pressure activated .ush
• valve by ITT Flygt Corp. Autocon Product group integrated within USFilter/Control Systems. Auto-Dox Controlled aeration weir by Purestream, Inc. autogenous combustion Burning that occurs when the heat of combustion of a
• wet organic material or sludge is suf.cient to vaporize the water and maintain combustion without auxiliary fuel. autogenous temperature Equilibrium temperature in sludge combustion where the heat input from the fuel equals the heat losses, and combustion is self-supporting. autoignition temperature The minimum temperature at which a substance ignites
• without application of a .ame or spark. Auto-Jet® Pressure leaf .lter by USFilter/Whittier. Autojust Automatic feedwell gate controller for circular sludge collectors by
• USFilter/Aerator Products.
• automatic sampling Collecting samples of prescribed volume over a de.ned time period by an apparatus designed to operate remotely without direct manual control.
• auto-oxidation A self-induced oxidation process.
• Autopress High throughput automatic .lter press by USFilter/Dewatering Systems.
• Auto-Pulse™ Tubular backpulse .lter by USFilter/Whittier.
• Auto-Rake® Reciprocating rake bar screen by Franklin Miller, Inc.
• autoreactive A compound that is reactive under normal conditions and does not

• require heat, additional compounds, or a change in conditions. Auto-Retreat Automatic bar screen control system by In.lco Degremont, Inc. AutoSDI™ Portable, computer-based silt density index instrument by King Lee
• Technologies. Auto-Shell™ Granular media .lter by USFilter/Whittier. Auto-Shok™ Tube-type vertical pressure leaf .lter by USFilter/Whittier. Auto-Skimmer™ Skimmer used to remove .oating hydrocarbons from water wells
• by Science Application International Corp. AutoTherm™ Aerobic thermophilic digestion system by CBI Walker, Inc. autothermal thermophilic aerobic digestion (ATAD) A biological digestion sys­
• tem that converts soluble organics to lower-energy forms through anaerobic,
• fermentative, and aerobic processes at thermophilic temperatures. autothermic combustion See “autogenous combustion.” Autotravel Traveling bridge sludge collectors by Simon-Hartley, Ltd. Autotrol Rotating biological contactors product line by USFilter/Envirex. autotroph Organism that derives its cell carbon from carbon dioxide. Auto-Vac® Rotary drum .lter by Alar Engineering Corp. autoxidation A spontaneous process in which a compound is oxidized, usually in
• the presence of oxygen, but other compounds can act as electron acceptors.

• available chlorine A measure of the amount of chlorine available in chlorinated lime, hypochlorite compounds, and other materials used as a source of chlorine when compared with that of liquid or gaseous chlorine.
• average daily .ow (ADF) The total .ow past a point over a period of time divided by the number of days in that period.
• average .ow The arithmatic average of .ows measured at a given point.
• average rainfall intensity (ARI) A measurement of rainfall per unit of time.
• Avery Filter Recessed chamber .lter press by Komline-Sanderson, Engineering Corp.
• AVGF® Automatic valveless gravity .lter by USFilter/Warren.
• AWI Anthratech Western, Inc.
• AWS American Welding Society.
• AWT See “advanced wastewater treatment (AWT).”
• AWWA American Water Works Association.
• AWWARF American Water Works Association Research Foundation.
• axial .ow The .ow of .uid in the same direction as the axis of symmetry of a tank or basin.
• axial .ow pump A type of centrifugal pump in which .uid .ow remains parallel to the .ow path and develops most of its head by the lifting action of the vanes.
• Azenit Biological wastewater treatment process technology by USFilter/Krüger (North America) and OTV.
• azeotropic A liquid of two or more substances that behaves like a single substance in that the vapor produced by partial evaporation has the same composition as the liquid.
• Aztec® Chlorine/oxidant residual analyzer by Capital Controls Co

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