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Absolute The micron rating of a filter. It indicates that any particle larger than a specific size will be trapped within the filter.
Absolute Filter Rating Filter rating meaning that 99.9 % (or essentially all) of the particles larger than a specified micron rating will be trapped on or within the filter.
Absorption The process in which one substance penetrates into the body of another substance, termed the absorbent. An example is the absorption of water into soil.
Acequia Acequias are gravity-driven waterways, similar in concept to a flume. Most are simple ditches with dirt banks, but they can be lined with concrete. They were important forms of irrigation in the development of agriculture in the American Southwest. The proliferation of cotton, pecans and green chile as major agricultural staples owe their progress to the acequia system.
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. An acid is the opposite of an alkali, has a pH rating lower than 7.0, will turn litmus paper red, and has a sour taste. A substance that has a pH of less than 7, which is neutral. Specifically, an acid has more free hydrogen ions (H+) than hydroxyl ions (OH-).
Acid Aerosol Very small liquid or solid particles that are acidic and are small enough to become airborne.
Acid Neutralizing Capacity Measure of the buffering capacity of water; the ability of water to resist changes in pH.
Acid Rain A broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This can include rain, snow, fog, hail or even dust that is acidic. Acid rain results when sulfur dioxide (SO2) and nitrogen oxides (NOX) are emitted into the atmosphere and transported by wind and air currents. The SO2 and NOX react with water, oxygen and other chemicals to form sulfuric and nitric acids.
Acidic Deposition The transfer of acidic or acidifying substances from the atmosphere to the surface of the Earth or to objects on its surface. Transfer can be either by wet-deposition processes (rain, snow, dew, fog, frost, hail) or by dry deposition (gases, aerosols, or fine to coarse particles).
Acidic Water Water with a low pH, meaning that it's more likely to corrode metal pipes and leach metals out of exposed surfaces. Water that has a pH less than 6.5 could be acidic and corrosive. Acid water has the potential to leach metal ions, including iron, manganese, copper, lead, and zinc, from aquifers, plumbing fixtures, and piping. Because of its corrosive nature, this water could contain elevated levels of toxic metals, damage metal pipes. Many people also find that low pH water has a sour or metallic taste (because of the dissolved metals). It can also discolor laundry as well as plumbing fixtures.
Acidity The quantitative capacity of a water or water solution to neutralize an alkali or base. It is usually measured by titration with a standard solution of sodium hydroxide, and expressed in ppm or mg/L of its calcium carbonate equivalent.
Acre Foot (acre-ft.) - The volume of water needed to cover an acre of land to a depth of one foot; equivalent to 43,560 cubic feet or 325,851 gallons.
Acre-foot (acre-ft) The volume of water required to cover 1 acre of land (43,560 square feet) to a depth of 1 foot. Equal to 325,851 gallons or 1,233 cubic meters.
Activated Alumina A medium made by treating aluminum ore so that it becomes porous and highly adsorptive. Activated alumina will remove several contaminants including fluoride, arsenic, and selenium. It requires periodic cleaning with a regenerant such as alum, acid and/or caustic.
Activated Carbon A water treatment medium, found in block, granulated, or powdered form, which is produced by heating carbonaceous materials, such as coal, wood, or coconut shells, in the absence of air, creating a highly porous adsorbent material. Activated carbon is commonly used for dechlorination, organic chemical reduction and radon reduction, and is recognized by the US EPA as the best available technology for reduction of organic chemicals from drinking water.
Activated Coal This is the most commonly used adsorption medium, produced by heating carbonaceous substances or cellulose bases in the absence of air. It has a very porous structure and is commonly used to remove organic matter and dissolved gases from water. Its appearance is similar to coal or peat. Available in granular, powder or block form; in powder form it has the highest adsorption capacity.
Activated Silica A negatively charged colloidal substance generally formed by combining a dilute sodium silicate solution with a dilute acidic solution (or other activant). Generally used as a coagulant aid.
Activated Sludge Oxygen dependent biological process that serves to convert soluble organic matter to solid biomass, that is removable by gravity or filtration.
Active Groups Really fixed ions bolted on to the matrix of an ion exchanger. Each active group must always have a counter-ion of opposite charge near itself.
Adsorbate Any substance that is or can be adsorbed. The liquid, gas or solid substance which is adsorbed as molecules, atoms, or ions.
Adsorbent A water treatment medium, usually solid, capable of the adsorption of liquids, gases, and/or suspended matter. Activated alumina and activated carbon are common adsorbents used in water processing.
Adsorption The physical process occurring when liquids, gases, or suspended matters adhere to the surfaces of, or in the pores of, an adsorbent media such as activated carbon. Adsorption is a physical process which occurs without chemical reaction.
Advanced Oxidation Process One of several combination oxidation processes. Advanced chemical oxidation processes use (chemical) oxidants to reduce COD/BOD levels, and to remove both organic and oxidizable inorganic components. The processes can completely oxidize organic materials to carbon dioxide and water, although it is often not necessary to operate the processes to this level of treatment.
Advanced Wastewater Treatment Any treatment of sewage water that includes the removal of nutrients such as phosphorus and nitrogen and a high percentage of suspended solids.
Advanced Water Treatment The level of water treatment that requires an 85-percent reduction in pollutant concentration, also known as tertiary treatment.
Aerate To supply air to water, soil, or other media.
Aerated Lagoon A water treatment pond that speeds up biological decomposition of organic waste by stimulating the growth and activity of bacteria, which are responsible for the degradation.
Aeration The process in which air is brought into intimate contact with water, often by spraying water through air, or by bubbling air through water. Aeration may be used to add oxygen to the water for the oxidation of matter such as iron, or to cause the release of dissolved gases such as carbon dioxide or hydrogen sulfide from the water.
Aeration Tank A tank that is used to inject air into water.
Aerobic An action or process conducted in the presence of air, such as aerobic digestion of organic matter by bacteria. Pertaining to, taking place in, or caused by the presence of oxygen.
Aerosol Very small liquid or solid particles dispersed in air.
Affinity The keenness with which an ion exchanger takes up and holds on to a counter-ion. Affinities are very much affected by the concentration of the electrolyte surrounding the ion exchanger.
Agglomeration A process of bringing smaller particles together to form a larger mass.
Aggressive Water Water that is soft and acidic and can corrode plumbing, pipes and appliances.
Air Check A device which allows water, but not air, to pass through it. An air check is a typical component of a treatment system using a regenerant eductor.
Air Gap A clear vertical space through the free atmosphere between the lowest opening of any pipe or faucet conveying water or waste to a tank, plumbing fixture receptor, or other device and the flood level rim of the receptacle. An air gap is used to prevent cross connection between a water treatment device and a possible source of wastewater thereby preventing a reverse flow of water from the sewer into the water supply system. Without an air gap, such reverse flow could occur due to an increase in the pressure in the sewer system or the creation of a negative pressure in the water supply line. Local plumbing codes usually require the air gap to be twice the diameter of the inlet with a minimum width of 1 1/2 inches.
Algae Chlorophyll-bearing nonvascular, primarily aquatic species that have no true roots, stems, or leaves; most algae are microscopic, but some species can be as large asvascular plants.
Algal Bloom The rapid proliferation of passively floating, simple plant life, such as blue-green algae, in and on a body of water.
Aliquot A measured portion of a sample taken for analysis. One or more aliquots make up a sample.
Alkali A substance which creates a bitter taste and a slippery feel when dissolved in water and will turn red litmus paper blue. An alkali has a pH greater than seven and is the opposite of an acid. Highly alkaline waters tend to cause drying of the skin. Alkalis may include the soluble hydroxide, carbonate, and bicarbonate salts of calcium, magnesium, potassium, and sodium. A hydroxide alkali may also be called a base.
Alkaline Has a pH greater than 7; in common usage, a pH of water greater than 7.4. sometimes water or soils contain an amount of alkali (strongly basic) substances sufficient to raise the pH value above 7.0 and be harmful to the growth of crops.
Alkalinity The quantitative capacity of water to neutralize an acid; that is, the measure of how much acid can be added to a liquid without causing a significant change in pH. Alkalinity is not the same as pH because water does not have to be strongly basic (high pH) to have high alkalinity. In the water industry, alkalinity is expressed in mg/l of equivalent calcium carbonate. There are three kinds of alkalinity: carbonate, bicarbonate, and hydroxide alkalinity. Total alkalinity is the sum of all three kinds of alkalinity. Different tests are used to determine the quantity of the different kinds of alkalinities present in water.
Alluvial Aquifer A water-bearing deposit of unconsolidated material (sand and gravel) left behind by a river or other flowing water.
Alluvium General term for sediments of gravel, sand, silt, clay, or other particulate rock material deposited by flowing water, usually in the beds of rivers and streams, on a flood plain, on a delta, or at the base of a mountain.
Alpine Snow Glade A marshy clearing between slopes above the timberline in mountains.
Alternating System As in the pressure in the sewer system or the creation of a negative pressure in the water supply line. Local plumbing codes usually require the air gap to be twice the diameter of the inlet with a minimum width of 1 1/2 inches.
Alum The common name for aluminum sulfate [Al2 (SO4) x 14H2 O] which is often used as a coagulant in water treatment.
Amalgamation The dissolving or blending of a metal (commonly gold and silver) in mercury to separate it from its parent material.
Ammonia A compound of nitrogen and hydrogen (NH3) that is a common by-product of animal waste. Ammonia readily converts to nitrate in soils and streams.
Amoeba A single celled protozoan that is widely found in fresh and salt water. Some types of amoebas cause diseases such as amoebic dysentery.
Anadromous Fish Migratory species that are born in freshwater, live mostly in estuaries and ocean water, and return to freshwater to spawn.
Anaerobic Pertaining to, taking place in, or caused by the absence of oxygen.
Anaerobic Organism An organism that can thrive in the absence of oxygen (air), such as bacteria in a septic tank.
Angstrom Unit A unit of wavelength of light equal to .00001 millimeter or .0001 microns.
Anion A negatively charged ion in solution, such as bicarbonate, chloride, or sulfate. An anion [such as chloride (Cl-)] may result from the dissociation of a salt, acid, or alkali.
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.
Anode The positive pole of an electrolytic system. The metal which goes into solution in a galvanic cell. Anodes of metals such as magnesium and zinc are sometimes installed in water heaters or other tanks to deliberately establish galvanic cells to control corrosion of the tank through the sacrifice of the anode.
Anomalies As related to fish, externally visible skin or subcutaneous disorders, including deformities, eroded fins, lesions, and tumors.
ANSI Abbreviation for American National Standards Institute.
Anthropogenic Having to do with or caused by humans.
Anticline A fold in the Earth's crust, convex upward, whose core contains stratigraphically older rocks.
Appropriation Doctrine The system for allocating water to private individuals used in most Western states. The doctrine of Prior Appropriation was in common use throughout the arid west as early settlers and miners began to develop the land. The prior appropriation doctrine is based on the concept of First in Time, First in Right. The first person to take a quantity of water and put it to Beneficial Use has a higher priority of right than a subsequent user. Under drought conditions, higher priority users are satisfied before junior users receive water. Appropriative rights can be lost through nonuse; they can also be sold or transferred apart from the land. Contrasts with Riparian Water Rights.
Aquaculture Farming of plants and animals that live in water, such as fish, shellfish, and algae.
Aquatic Relating to water; living in or near water or taking place in surface water.
Aquatic Guidelines Specific levels of water quality which, if reached, may adversely affect aquatic life. These are nonenforceable guidelines issued by a governmental agency or other institution.
Aqueduct A pipe, conduit, or channel designed to transport water from a remote source, usually by gravity.
Aqueous Of or containing water, typically as a solvent or medium.
Aqueous Solubility The maximum concentration of a chemical that dissolves in a given amount of water.
Aquifer SA body of permeable rock which can contain or transmit groundwater.
Aquifer (confined) Soil or rock below the land surface that is saturated with water. There are layers of impermeable material both above and below it and it is under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer.
Aquifer (unconfined) An aquifer whose upper water surface (water table) is at atmospheric pressure, and thus is able to rise and fall.
Aromatics A type of hydrocarbon that contains a ring structure, such as benzene and toluene. They can be found for instance in gasoline.
Arroyo A small, deep, flat-floored channel or gully of anephemeralorintermittent stream, usually with nearly vertical banks cut, into unconsolidated material. A term commonly used in the arid and semiarid regions of the Southwestern United States.
Artesian Describes underground water trapped under pressure between layers of impermeable rock. An artesian well is one that taps artesian water.
Artesian Water Groundwater that is under pressure when tapped by a well and able to rise above the level at which it is first encountered. It may or may not flow out at ground level. The pressure in such an aquifer commonly is called artesian pressure, and the formation containing artesian water is an artesian aquifer or confined aquifer. See flowing well.
Artificial Recharge A process where water is put back into groundwater storage from surface-water supplies such as irrigation, or induced infiltration from streams or wells.
ASME Abbreviation for American Society of Mechanical Engineers.
Assimilation The ability of water to purify itself of pollutants.
Assimilative Capacity The capacity of natural water to receive wastewaters or toxic materials without negative effects and without damage to aquatic life or humans who consume the water.
Atmospheric Deposition The transfer of substances from the air to the surface of the Earth, either in wet form (rain, fog, snow, dew, frost, hail) or in dry form (gases, aerosols, particles).
Atmospheric Pressure The pressure exerted by the atmosphere on any surface beneath or within it; equal to 14.7 pounds per square inch at sea level.
Atom The smallest unit of matter that is unique to a particular element. They are the ultimate building blocks for all matter.
Atomic Number A specific number that differs for each element, equal to the number of protons in the nucleus of each of its atoms.
Attenuation The process of reduction of a compound's concentration over time. This can be through absorption, adsorption, degradation, dilution or transformation.
Attrition The action or process of gradually redusing the strength or effectiveness.
Automatic Water Softener (or Automatic Filter) A water softener (or filter) that is equipped with a clock timer, meter, or sensor which automatically initiates the backwash and/or regeneration process at the preset intervals of time. A predetermined number of gallons of water usage or as determined by a sensor. All operations, including bypass of treated or untreated water (depending upon design), backwashing, brining, rinsing, and returning the unit to service are performed automatically.
Available Chlorine A measure of the amount of chlorine available in chlorinated lime, hypochlorite compounds, and other materials.
Average Discharge As used by the U.S. Geological Survey, the arithmetic average of all complete water years of record of surface water discharge whether consecutive or not. The term average generally is reserved for average of record and mean is used for averages of shorter periods, namely, daily, monthly, or annual mean discharges.
AWWA Abbreviation for American Water Works Association. Most municipal water treatment plants hold membership in this association.