Water & Wastewater Engineering 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

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Abiotic environment
The part of an ecosystem that includes the nonliving surroundings.

Absolute
The micron rating of a filter. It indicates that any particle larger than a specific size will be trapped within the filter.

ABSORBENT
A substance which has the capacity to adsorb.

Absorption
When a solid takes up molecules into its structure.

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 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
Rain that has a flamboyantly low pH, due to contact with atmospheric pollutants such as sulphuric oxides.

ACIDITY
The quantitative capacity of water to neutralize a base, expressed in ppm or mg/L calcium carbonate equivalent. The number of hydrogen atoms that are present determines this. It is usually measured by titration with a standard solution of sodium hydroxide.

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."

ADSORPTION
The process in which matter adheres to the surface of an adsorbent.

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 oxidisable inorganic components. The processes can completely oxidise organic materials to carbon dioxide and water, although it is often not necessary to operate the processes to this level of treatment.
A wide variety of advanced oxidation processes are available:
- Chemical oxidation process using hydrogen peroxide, ozone, combined ozone & peroxide, hypochlorite, Fenton's reagent, etc.
- Ultra-violet (UV) enhanced oxidation such as UV/ ozone, UV/ hydrogen, UV/air
- Wet air oxidation and catalytic wet air oxidation (where air is used as the oxidant)

Advanced water treatment
The level of water treatment that requires an 85-percent reduction in pollutant concentration, also known as tertiary 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.

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
Technique that is used with water treatment that demands oxygen supply, commonly known as aerobic biological water purification. Either water is brought into contact with water droplets by spraying or air is brought into contact with water by means of aeration facilities. Air is pressed through a body of water by bubbling and the water is supplied with oxygen.

Aeration tank
A tank that is used to inject air into water.

Aerobic
A process that takes place in the presence of oxygen, such as the digestion of organic matter by bacteria in an oxidation pond.

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.

Alcohol
An organic compound with one or more hydroxyl "-OH" groups.

Aldehyde
An organic compound with a carbonyl at one end of a hydrocarbon group.

Algae
Single- or multi-celled organisms that are commonly found in surface water, such as duckweed. They produce their own food through photosynthesis. The algae population is divided up into green algae and blue algae, of which the blue algae are very damageable to human health. Excessive algae growth may cause the water to have undesirable odours or tastes. Decay of algae diminishes oxygen supplies in the water.

Algal blooms
Periods of enlarged algal growths that affect water quality. Algal blooms indicate potentially hazardous changes in the chemistry of water.

Aliquot
A measured portion of a sample taken for analysis. One or more aliquots make up a sample.

Alkalinity
Alkalinity means the buffering capacity of water; the capacity of the water to neutralize itself. It prevents the water pH levels from becoming too basic or acid. It also adds carbon to water. Alkalinity stabilizes water at pH levels around 7. However, when the acidity is high in water the alkalinity decreases, which can cause harmful conditions for aquatic life.
In water chemistry alkalinity is expressed in ppm or mg/L of equivalent calcium carbonate. Total alkalinity of water is the sum of all three sorts of alkalinity; carbonate, bicarbonate and hydroxide alkalinity.

Alluvium
Sediments deposited by erosion processes, usually by streams.

Amine
A functional group consisting of "-NH2."

Amino acid
A functional group which consists of a carbon with a carboxylic acid, "-COOH" and an amine, "-NH2." These compounds are the building blocks for proteins.

Anabolism Biosynthesis, the production of new cellular materials from other organic or inorganic chemicals.

Anaerobes
A group of organisms that do not require molecular oxygen. These organisms, as well as all known life forms, require oxygen. These organisms obtain their oxygen from inorganic ions such as nitrate or sulfate or from protein.

Anaerobic
A process that takes place in the absence of oxygen, such as the digestion of organic matter by bacteria in a UASB-reactor.

Anion
A negatively charged ion that results from the dissociation of salts, acids or alkali's in solution.

Anode
A site in electrolysis where metal goes into solution as a cation leaving behind an equivalent of electrons to be transferred to an opposite electrode, called a cathode.

Anoxic process
A process which occurs only at very low levels of molecular oxygen or in the absence of molecular oxygen.

Anthropogenic Of, made, or caused by human activity or actions.

Aquatic
Growing in water, living in water, or frequenting water.

Aqueous
Something made up of water.

Aqueous solubility
The maximum concentration of a chemical that dissolves in a given amount of water.

Aquifer
A layer in the soil that is capable of transporting a significant volume of groundwater.

Aromatics
A type of hydrocarbon that contains a ring structure, such as benzene and toluene. They can be found for instance in gasoline.

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.

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.

Attached growth reactor
A reactor in which the microorganisms are attached to engineered surfaces within the reactor. Examples of attached growth reactors are the trickling filter and the rotating biological contactor. See suspended growth reactor.

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 of one particle rubbing against the other in a filter media or ion exchange bed that can in time cause breakdown of the particles.

Autotrophic
Organisms which utilize inorganic carbon for synthesis of protoplasm. Ecologists narrow the definition further by requiring that autotrophs obtain their energy from the sun. In microbiologist parlance, this would be a photoautotroph. See photoautotrophic and chemoautotrophic.

Autotrophs
A group of organisms capable of obtaining carbon for synthesis from inorganic carbon sources such as carbon dioxide and its dissolved species (the carbonates). This group includes plants and algae.

Available chlorine
A measure of the amount of chlorine available in chlorinated lime, hypochlorite compounds, and other materials.

ALKALINITY
The quantitative capacity of 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. A moderate amount of Alkalinity in your water is desirable because it reduces the effect of corrosion. The EPA has not set a level for Alkalinity, but a level greater than 100 ppm is recommended.

ALUMINUM
Aluminum can be found as a natural forming mineral or as a by product of water that is corrosive or aggressive. Aluminum in the water may cause a discoloration or cloudy appearance. The EPA maximum contaminant level for aluminum in water is 0.2 ppm.

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.

AQUIFER
A layer or zone below the surface of the earth which is capable of yielding a significant volume of water.

ATOM
The smallest particle of an element that can exist either alone or in combination with similar particles of the same element or a different element.

ATTRITION
The process in which solids are worn down or ground down by friction, often between particles of the same material. Filter media and ion exchange materials are subject to attrition during backwashing, regeneration, and service.

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Backflow

The flow of water in a medium in a direction opposite to normal flow. Flow is often returned into the system by backflow, if the wastewater in a purification system is severely contaminated.
Back Pressure

Pressure that can cause water to backflow into the water supply when a user's waste water system is at a higher pressure than the public system.
Back siphonage

Reverse seepage of water in a distribution system.

Backwashing
Reversing the flow of water back through the filter media to remove entrapped solids.

Bacteria
Microscopically small single-cell organisms, that reproduce by fission of spores.

Bacterial water contamination
The introduction of unwanted bacteria into a water body.

Baghouse filter
A fabric filter device used to remove particulate air pollutants.

Base
An alkaline substance that has a pH that exceeds 7,5.

Bed Load
Sediment particles resting on or near the channel bottom that are pushed or rolled along by the flow of water.

Benthic zone
The lower region of a body of water including the bottom.

Bicarbonates
Salts containing the anion HCO3-. When acid is added, this ion breaks into H2O and CO2, and acts as a buffer.

Binder
Chemicals that hold short fibres together in a cartridge filter.

Bioaccumulantion
The increase in concentration of a substance in living organisms, as they take in contaminated air, water, or food, due to slow metabolization and excretion.

Biochemical Oxygen Demand (BOD)
The amount of oxygen (measured in mg/L) that is required for the decomposition of organic matter by single-cell organisms, under test conditions. It is used to measure the amount of organic pollution in wastewater.

Biocide
A chemical that is toxic to microrganisms. Biocides are often used to eliminate bacteria and other single-cell organisms from water.

Biodegradable pollutants
Pollutants that are capable of decomposing under natural conditions.

Biofilm
Population of various microrganisms, trapped in a layer of slime and excretion products, attached to a surface.

Biofilm - A film of microorganisms attached to a surface, such as that on a trickling filter, rotating biological contactor, or rocks in natural streams.

Biogeochemical cycle
The cycle of elements through the biotic and abiotic environment.

Biological contaminants
Living organisms such as viruses, bacteria, fungi, and mammal and bird antigens that can cause harmful health effects to humans.

Biologically activated carbon
Activated carbon that supports active microbial growth, in order to aid in the degradation of organics that have been absorbed on its surface and in its pores.

Biological oxidation
Decomposition of complex organic materials by microrganisms through oxidation.

Biomonitoring
The use of living organisms to test the suitability of effluents for discharge into receiving waters and to test the quality of such waters downstream from the discharge.

Bioremediation
The biological treatment of wastewater and sludge, by inducing the breakdown of organics and hydrocarbons to carbon dioxide and water.

Biota
All living organisms in a region or ecosystem.

Biosynthesis Catabolism,
the production of new cellular materials from other organic or inorganic chemicals.

Biotransformation
Conversion of a substance into other compounds by organisms; including biodegradation.

Blackwater
Water that contains waste of humans, animals or food.

Blind spots
Any place on a filter medium where fluids cannot flow through.

Blinding
A build-up of particles in a filter medium, that prevents fluids from flowing through.

BOD5
The amount of dissolved oxygen consumed in five days by bacteria that perform biological degradation of organic matter.

Boiling point
The temperature at which the vapour pressure of a liquid equals the pressure of its surface. The liquid will than vaporize If the pressure of the liquid varies, the actual boiling point varies. For water the boiling point is 100 degrees Celsius.

Bottled water
Water that is sold in plastic containers for drinking water and/ or domestic use.

Brackish water
Water that is neither falls in the category of salt water, nor in the category of fresh water. It holds the middle between either one of the categories.

Breakpoint chlorination
Addition of chlorine to water until there is enough chlorine present for disinfection of water.

Breakthrough
Crack or break in a filter bed that allows the passage of floc or particulate matter through a filter.

Brine
Highly salty and heavily mineralised water, containing heavy metal and organic contaminants.

Buffer
A substance that reacts with hydrogen or hydroxyl ions in a solution, in order to prevent a change in pH.

BACKWASH
The process in which beds of filter or ion exchange media are subjected to flow opposite to the service direction to loosen the bed and to flush suspended matter (collected during the service run) to waste.

BACTERIA
Unicellular micro-organisms which typically reproduce by cell division. Although usually classified as plants, bacteria contain no chlorophyll.

BASE
A substance which releases hydroxyl ions which when dissolved in water. Bases react with acids to form a neutral salt and water.

BED
The ion 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.

BICARBONATE ALKALINITY
The alkalinity of a water due to the presence of bicarbonate ions (HCO3 -).

BIOCHEMICAL OXYGEN DEMAND
The amount of oxygen consumed in the oxidation of organic matter by biological action under specific standard test conditions. Widely used as a measure of the strength of sewage and waste water.

BRINE
A strong solution of salts(s), such as the sodium chloride brine used in the regeneration of ion exchange water softeners; also applied to the mixed sodium, calcium, and magnesium chloride waste solution from regeneration.

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CALCIUM
One of the principal elements making up the earth's crust; its compounds, when dissolved, make the water hard. The presence of calcium in water is a factor contributing to the formation of scale and insoluble soap curds which are a means of clearly identifying hard water.

CALCIUM MAGNESIUM
Two of the principal elements making up the earth's crust; its compounds, when dissolved, make the water hard. The presence of calcium and magnesium in water is a factor contributing to the formation of scale and insoluble soap curds 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 servicing of the media (i.e., 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 regeneration's 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.

Carbonaceous biochemical oxygen demand (CBOD)
The amount of oxygen required to oxidize any carbon containing matter present in a water.

CARBONATE
The CO3- ion.

CARBONATE ALKALINITY
Alkalinity due to the presence of the carbonate ion.

CARBONATE HARDNESS
Hardness due to the presence of calcium and magnesium bicarbonates and carbonates in water; the smaller of the total hardness and the total alkalinity.

Carbonyl
A functional group with an oxygen atom double bonded to a carbon atom.

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.

Catabolism
The production of energy by the degradation of organic compounds.

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. The term is usually applied to strong bases.

CAUSTIC SODA
The common name for sodium hydroxide.

Cell
A unit of varying dimensions in a landfill which is isolated from the environment by 6 to 12 inches of soil cover. A cell is one day's waste or less. A cell is covered with soil at the end of each day.

CHELATE
To form a complex chemical compound in which an ion, usually metallic, is bound into a stable ring structure.

CHELATING AGENT
A chemical compound sometimes fed to water to tie up undesirable metal ions, keep them in solution, and eliminate or reduce the normal effects of the ion.

CHEMICAL OXYGEN DEMAND
The amount of matter, both organic and inorganic, in a water or waste water which can be oxidized by boiling with a strong oxidizing acid under standard test conditions and expressed as the equivalent amount of oxygen; often used as a measure of the strength of sewage and waste water; includes materials not oxidized in the BOD test, and thus does not correlate with BOD.

CHLORIDE
Chloride is a natural forming mineral found in water. High levels of chloride can impact taste and also be associated with corrosion or high Sodium content. Water with excessive amounts of chloride can be very toxic to most plants. The EPA maximum contaminant level for chloride is 250 ppm.

CHLORINE
A gas, C12, widely used in the disinfection of water and an oxidizing agent for organic matter, iron, etc.

CHLORINE CONTENT
Chlorine is added to water as a disinfectant to kill harmful organisms or bacteria. Even though Chlorine is used in providing safe drinking water, when it is in excess, it is the most common cause of taste and odor problems. Also when Chlorine is combined with ammonia as a disinfectant called chloramines, a byproduct as Trihalomethanes are formed, which cause cancer. The EPA does not have a level for Chlorine but a concentration of 0.1 to 0.2 ppm is recommended and a level of 1.0 or greater is considered very high.

CHLORINE DEMAND
A measure of the amount of chlorine which will be consumed by organic matter and other oxidizing substances in a water before a chlorine residual will be found; the difference between the total chlorine fed and the chlorine residual.

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.

COAGULANT AID
A material which is not a coagulant, but which improves the effectiveness of a coagulant, often by forming larger or heavier particles, speeding the reactions, or permitting reduced coagulant dosage.

COAGULATION
The process in which very small, finely divided solid particles, often colloidal in nature, are agglomerated into larger particles.

COLLOID
Very finely divided solid particles which will not settle out of a solution; intermediate between a true dissolved particle and a suspended solid which will settle out of solution. The removal of colloidal particles usually requires coagulation to form larger particles which may be removed by sedimentation and/or filtration.

COMPENSATED HARDNESS
A calculated value based on the total hardness, the magnesium to calcium ratio, and the sodium concentration of a water. It is used to correct for the reductions in hardness removal capacity caused by these factors in cation exchange water

CONDUCTANCE
A measure of the ability of a solution to carry electricity; the reciprocal of the electrical resistance. The unit of conductance is the mho (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.

COPPER
Copper in water is a common problem in many households. Copper is present due to the corrosion of plumbing materials from Acidic (low pH) or Aggressive water (low TDS). Common problems associated with copper due corrosion are leaks in the plumbing system or blue-green staining. High copper content can also cause some health concerns by effecting the stomach and intestines. The EPA has set a maximum contaminant level of 1.3 ppm.

CORROSION
The destructive disintegration of a metal by electrochemical means.

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.

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DE IONIZATION
The removal of all ionized minerals and salts (both organic and inorganic) from a solution by a two-phase ion exchange procedure. First, positively charged ions are exchanged 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.

D.I. OR DI
Abbreviation for de-ionization.

DIALYSIS
The separation of components of a solution by diffusion through a semi-permeable membrane which is capable of passing certain ions or molecules while rejecting others.

DIFFERENTIAL PRESSURE
The difference in pressures at two points in a water system; may be due to differences in elevation, or to friction losses or pressure drops due to resistance to flow in pipes, softeners, filters or other devices.

DISINFECTION
A process in which pathogenic (disease-producing) bacteria are killed; may involve disinfecting agents such as chlorine, or physical processes such as heating.

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 1800C.

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.

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EFFICIENCY
The ratio of output per unit input; the effectiveness of performance of a system; in an ion exchange system, often expressed as the amount of regenerant required to produce a unit of capacity, such as the pounds of salt per kilo grain of hardness removal.

ELECTRODIAYSIS
A process in which a direct current is applied to a cell to draw charged ions through ion-selective semi-permeable membranes, thus removing the ions from the solution.

ENDPOINT
The point at which a process is stopped because a predetermined value of a measurable variable is reached; the endpoint of an ion exchange water softener service run is the point at which the hardness of the softener effluent increases to a predefined concentration, often 1.0 grain per gallon; the endpoint of a filter service run may be the point at which the pressure drop across the filter reaches a predetermined value; the endpoint of a titration is the point at which the tit-rant produces predetermined color change, pH value, or other measurable characteristic.

EQUIVALENT PER MILLION
A unit of concentration used in chemical calculations, calculated by dividing the concentration in ppm or mg/1 by the equivalent weight.

EXHAUSTION
The state of an ion exchange material in which it is no longer capable of effective functioning 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.

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fecal coliform
the portion of the coliform bacteria group which is present in the intestinal tracts and feces of warm-blooded animals. A common pollutant in water.

fen
a type of wetland that accumulates peat deposits, but not as much as a bog. Fens are less acidic than bogs, deriving most of their water from groundwater rich in calcium and magnesium.

fermentation, anaerobic
process in which carbohydrates are converted in the absence of oxygen to hydrocarbons (such as methane).

field capacity
the amount of water held in soil against the pull of gravity.

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 mechanical process which removes particulate matter by separating water from solid material, usually by passing it through sand.

"first in time, first in right"
phrase indicating that older water rights have priority over more recent rights if there is not enough water to satisfy all rights.

fixed ground water
water held in saturated material that it is not available as a source of water for pumping.

FIXTURE UNIT
An arbitrary unit assigned to different types of plumbing fixtures, and used to estimate flow rate requirements and drain capacity requirements.

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.

FLUORIDATION
The quantity of water or regenerant which passes a given point in a specified unit of time, often expressed in gallons per minute.

FLUORIDE
Fluoride can be found in water as natural mineral or as an additive to public or municipal supplies. Fluoride can cause a discoloration or teeth known as Fluorosis when in excessive levels in water. The EPA maximum contaminant level for Fluoride in water is 2.0 ppm.

FLUSH TANK
A tank or chamber in which water is stored for rapid release to flush a toilet or water closet.

FLUSH VALVE
A self-closing valve designed to release a large volume of water when tripped, to flush a toilet or water closet.

FOULING
The process in which undesirable foreign matter accumulates in a bed of filter media or ion exchanger, clogging pores and coating surfaces, thus inhibiting or retarding the proper operation of the bed.

FREE AVAILABLE CHLORINE
The concentration of residual chlorine present as dissolved gas, hypochlorous avid or hypochlorite, not combined with ammonia or in other less readily available forms.

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.

free ground water
water in interconnected pore spaces in the zone of saturation down to the first impervious barrier, moving under the control of the water table slope.

freezing
the change of a liquid into a solid as temperature decreases. For water, the freezing point is 32 F or 0 C.

fresh water
water containing less than 1,000 parts per million (ppm) of dissolved solids of any type. Compare saline water.

fresh:salt water interface
the region where fresh water and salt water meet. In the Edwards region, it is commonly referred to as the "bad water line", although it is zone and not a line.

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gallon
A unit of volume. A U.S. gallon contains 231 cubic inches, 0.133 cubic feet, or 3.785 liters. One U.S. gallon of water weighs 8.3 lbs.

GPG
Abbreviation for grains per gallon.

grab sample
a sample taken at a given place and time. Compare composite sample.

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 analysis in the United States and Canada; one grain per U.S. gallon equals 17.12 milligrams per liter (mg/1) or parts per million (ppm). One grain per British (Imperial) gallon equals 14.3 milligrams per liter or parts per million.

GRAM
(g) The basic unit of weight (mass) of the metric system, originally intended to be the weight of one cubic centimeter of water at 4oC.

granular activated carbon
pure carbon heated to promote "active" sites which can adsorb pollutants. Used in some home water treatment systems to remove certain organic chemicals and radon.

GREEN SAND
A natural mineral, primarily composed of complex silicates, which possesses ion exchange properties.

greywater
wastewater from clothes washing machines, showers, bathtubs, handwashing, lavatories and sinks that are not used for disposal of chemical or chemical-biological ingredients.

groundwater
water within the earth that supplies wells and springs; water in the zone of saturation where all openings in rocks and soil are filled, the upper surface of which forms the water table.

groundwater hydrology
the branch of hydrology that deals with groundwater; its occurrence and movements, its replenishment and depletion, the properties of rocks that control groundwater movement and storage, and the methods of investigation and utilization of ground water.

groundwater law
the common law doctrine of riparian rights and the doctrine of prior appropriation as applied to ground water.

groundwater recharge
the inflow to a ground water reservoir.

groundwater reservoir
an aquifer or aquifer system in which ground water is stored. The water may be placed in the aquifer by artificial or natural means.

groundwater runoff
the portion of runoff which has passed into the ground, has become ground water, and has been discharged into a stream channel as spring or seepage water.

groundwater storage
the storage of water in groundwater reservoirs.

gully
a deeply eroded channel caused by the concentrated flow of water.

gully reclamation
use of small dams of manure and straw; earth, stone,or concrete to collect silt and gradually fill in channels of eroded soil.

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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.

HARDNESS CONTENT
Hardness is a measurement of naturally occurring dissolved minerals Calcium and Magnesium, hard water can inhibit the sudsing of detergents and soaps. Hard water can scale pipes and decrease the life of appliances such as washing machines, dishwashers, coffee makers. Hardness can also cause spotting of fixtures, tiles, dishes, or glassware. The EPA has not set a limit for hardness, but if your hardness is greater than 7 grains per gallon (gpg) then you should consider installing a water softener.

HARDNESS LEAKAGE
The presence of a consistent concentration of hardness in the effluent from an ion exchange water softener, often due to high concentrations of hardness or sodium in the water being treated (see Leakage).

HARD WATER
Water with a total hardness of one grain per gallon or more, as calcium carbonate equivalent.

HEAD
A measure of the pressure at a point tin a water system: expressed in pounds per square or in the height of a column of water which would produce the pressure.

HEAD LOSS
See Pressure Drop.

headgate
the gate that controls water flow into irrigation canals and ditches. A watermaster regulates the headgates during water distribution and posts headgate notices declaring official regulations.

heat of vaporization
the amount of heat necessary to convert a liquid (water) into vapor.

heavy water
water in which all the hydrogen atoms have been replaced by deuterium.

holding pond
a small basin or pond designed to hold sediment laden or contaminated water until it can be treated to meet water quality standards or be used in some other way.

HYDRAULIC
Referring to water or other fluids in motion.

HYDRAULIC CLASSIFICATION
A process in which particles of the same specific gravity may be graded according to size by backwashing or other relative upward flow of water; the smallest particles tending to rise to the top of the bed, and the largest particles tending to sink to the bottom, due to variations in weight to surface area ratios.

hydroelectric plant
electric power plant in which the energy of falling water is used to spin a turbine generator to produce electricity.

hydrograph
a chart that measures the amount of water flowing past a point as a function of time.

HYDROGEN CYCLE
The cation exchange cycle in which the cation exchanger is regenerated with acid, and cations are removed from the solution treated in exchanged for hydrogen ions.

HYDROGEN ION CONCENTRATION
The concentrations of hydrogen ions in moles per liter of solution; often expressed as pH (see pH).

hydroelectric plant
electric power plant in which the energy of falling water is used to spin a turbine generator to produce electricity.

hydrograph
a chart that measures the amount of water flowing past a point as a function of time.

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. (see Transpiration).

HYDROLYSIS
The reaction of a salt with water to form an acid and a base.

hydrometer
an instrument used to measure the density of a liquid.

hydropower
electrical energy produced by falling water.

hygroscopic nuclei
piece of dust or other particle around which water condenses in the atmophere. These tiny droplets then collide and coalesce, with as many as 10,000 nuclei contributing to formation of a raindrop.

hydrosphere
region that includes all the earth's liquid water, frozen water, floating ice, frozen upper layer of soil, and the small amounts of water vapor in the Earth's atmosphere.

hydrostatic head
a measure of pressure at a given point in a liquid in terms of the vertical height of a column of the same liquid which would produce the same pressure.

hydrostatic pressure
pressure exerted by or existing within a liquid at rest with respect to adjacent bodies.

hypolimnion
bottom layer of cold water in a lake. Compare epilimnion.

HYDROXIDE
A chemical compound of an element or elements with the hydroxyl (OH) anion. (see Hydroxyl).

HYDROXYL
The chemical group or ion (OH) which is neutral or positively charged.

HYPOCHLORITE
The "OC1" anion; calcium and sodium hypochlorites are commonly used as bleaches and disinfecting agents.

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ice
a solid form of water.

impermeable
material that does not permit fluids to pass through.

impervious
the quality or state of being impermeable; resisting penetration by water or plant roots. Impervious ground cover like concrete and asphalt affects quantity and quality of runoff.

impoundment
a body of water such as a pond, confined by a dam, dike, floodgate or other barrier. It is used to collect and store water for future use.

inchoate water right
an unperfected water right.

indicator organisms
microorganisms, such as coliforms, whose presence is indicative of pollution or of more harmful microorganism.

indicator tests
tests for a specific contaminant, group of contaminants, or constituent which signals the presence of something else (ex., coliforms indicate the presence of pathogenic bacteria).

inland freshwater wetlands
swamps, marshes, and bogs found inland beyond the coastal saltwater wetlands.

instream use
use of water that does not require withdrawal or diversion from its natural watercourse; for example, the use of water for navigation, recreation, and support of fish and wildlife.

interbasin transfer
the physical transfer of water from one watershed to another; regulated by the Texas Water Code.

intermittent stream
one that flows periodically. Compare perennial stream.

interstate water
according to law, interstate waters are defined as (1) rivers, lakes and other waters that flow across or form a part of state or international boundaries; (2) waters of the Great Lakes; (3) coastal waters whose scope has been defined to include ocean waters seaward to the territorial limits and waters along the coastline (including inland streams) influenced by the tide.

interstices
the void or empty portion of rock or soil occupied by air or water.

ION
An atom or group of atoms which functions as a unit, and has a positive or negative electrical charge, due to the gain or loss of one or more electrons. (see Ionization).

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 direction of the exchange depends upon the affinities of the ion exchanger for the ion present, and the concentrations of the ions in the solution. (see Base Exchange).

ION EXCHANGER
A permanent, insoluble material which contains ions that will exchange reversibly with other ions in a surrounding solution. Both cation and anion exchangers are used in water conditioning.

IONIZATION
The process in which atoms gain or lose electrons and thus become ions with positive or negative charges; sometimes used as a synonym for dissociation, the separation of molecules into charged ion in solution.

IONIZATION CONSTANT
A constant, specific for each partially ionizable chemical compound to express the ratio of the concentration of ions from the compound to the concentrate of un-ionized compound.

IRON
An element often found discolored in ground water (in the form of ferrous iron) in concentrations usually ranging from zero to 10 ppm (mg/1). It is objectionable in water supplies because it can effect water taste and cause unsightly colors produced when iron reacts with tannins in beverages such as coffee and tea. Iron causes staining after oxidation and precipitation, as ferric hydroxide (yellow, brown, and red on clothing, dishes, fixtures, and bathroom tile). Iron can also be found in a bacterial form which will appear as black or brown slime and can effect the odor of your water. Iron is a common water problem throughout the United States, it can be found in well water and municipal water. The EPA has set a maximum level for Iron of 0.3 ppm in water, iron concentrations at this level or higher can cause staining.

IRON BACTERIA
Organisms which are capable of utilizing ferrous iron (either from the water or from steel pipe) in their metabolism and precipitating both ferric hydroxide in their sheaths and gelatinous deposits. These organisms tend to collect in pipe lines and tanks during periods of low flow, and to break loose in slugs of turbid water to create staining, taste, and odor problems.

irrigation efficiency
the percentage of water applied, and which can be accounted for, in the soil moisture increase for consumptive use.

irrigation return flow
water which is not consumptively used by plants and returns to a surface or ground water supply. Under conditions of water right litigation, the definition may be restricted to measurable water returning to the stream from which it was diverted.

irrigation water
water which is applied to assist crops in areas or during times where rainfall is inadequate.

isotherm
line that connects points of equal temperature.

isohyet
line that connects points of equal rainfall.

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JACKSON TURBIDITY UNIT (JTU)
A quantitative unit of turbidity originally based on the comparison of a liquid (such as water) with a suspension of a specify type of silica, using the turbidity measure in a Jackson Candle Turbidimeter.

jet stream
a long narrow meandering current of high-speed winds near the tropopause blowing from a generally westerly direction and often exceeding a speed of 250 miles per hour.

jetteau
a jet of water.

jetter
one (as a geyser) that sends out a jet.

jetty
a structure (as a pier or mole of wood or stone) extending into a sea, lake, or river to influence the current or tide or to protect a harbor.

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kalema
a violent surf that occurs on the coast of the Guinea region, West Africa.

kame
a short ridge, hill, or mound of stratified drift deposited by glacial meltwater.

kame terrace
a terrace of stratified sand and and gravel deposited by streams between a glacier and an adjacent valley wall.

KILO: A prefix used to indicate 1000 of the succeeding unit. (Kilo is also sometimes used as an abbreviation for kilogram.)

KILO GRAIN (Kgr)
One thousand grains.

KILOGRAM (Kg)
One thousand grams.

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laboratory water
purified water used in the laboratory as a basis for making up solutions or making dilutions. Water devoid of interfering substances.

lag time
the time from the center of a unit storm to the peak discharge or center of volume of the corresponding unit hydrograph.

lagoon
a shallow pond where sunlight, bacterial action, and oxygen work to purify wastewater. Lagoons are typically used for the storage of wastewaters, sludges, liquid wastes, or spent nuclear fuel.

lake
an inland body of water, usually fresh water, formed by glaciers, river drainage etc. Usually larger than a pool or pond.

landscape impoundment
body of reclaimed water which is used for aesthetic enjoyment or which otherwise serves a function not intended to include contact recreation.

LANGE LIER'S INDEX
A calculated number used to predict whether or not a water will precipitate, be in equilibrium with, or dissolve calcium carbonate. It is sometimes erroneously assumed that any water which tends to dissolve calcium carbonate is automatically corrosive.

leachate
water containing contaminants which leaks from a disposal site such as a landfill or dump.

leaching
extraction or flushing out of dissolved or suspended materials from the soil, solid waste, or another medium by water or other liquids as they percolate down through the medium to groundwater.

LEAD
Lead in drinking water is a common problem, it comes from lead pipes, solder, and brass fittings. Water that has a low pH or Total Dissolved Solids will provide corrosive properties that can leach from your plumbing system. Lead can cause learning and physical disabilities in children and also Hypertension in adults. The EPA action level for Lead is 0.015 ppm.

LEAKAGE
The amount of contaminant or hardness remaining in water after filtering or other treatment.lentic system
a nonflowing or standing body of fresh water, such as a lake or pond. Compare lotic system.

levee
a natural or man-made earthen obstruction along the edge of a stream, lake, or river. Usually used to restrain the flow of water out of a river bank.

LIME
The common name for calcium oxide (Ca); hydrated lime is calcium hydroxide [Ca(OH)2].

LIME SCALE
Hard water scale containing a high percentage of calcium carbonate.

LIMESTONE
A sedimentary rock, largely calcium carbonate, usually also containing significant amounts of magnesium carbonate.

limiting factor
factor such as temperature, light, water, or a chemical that limits the existence, growth, abundance, or distribution of an organism.

limnology
scientific study of physical, chemical, and biological conditions in lakes, ponds, and streams.

liquid
a state of matter, neither gas nor solid, that flows and takes the shape of its container.

LITER
The basic metric unit of volume; 3.785 liters equals one U.S. gallon. One liter of water weighs 1000 grams.

littoral zone
area on or near the shore of a body of water.

lotic system
a flowing body of fresh water, such as a river or stream. Compare lentic system.

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MAGNESIUM
One of the elements making up the earth's crust. Magnesium compounds, when dissolved in water, make the water hard. The presence of magnesium in water is a factor contributing to the formation of scale and insoluble soap curds.

MANGANESE
An element sometimes found in ground water, usually with dissolved iron but in lower concentrations. Manganese is a typical natural occurring mineral found in municipal and well water. Manganese effects the taste and the color or water. Manganese can also cause staining of clothes and dishware and black stains and other problems similar to iron. The EPA has determined that concentrations greater than 0.05 ppm can cause these aesthetic problems.

MANGANESE GREEN SAND
Green sand which has been processed to incorporate in its pores and on its surface the higher oxides of manganese. The product has a mild oxidizing power, and is often used in the oxidation and precipitation of iron, manganese and/or hydrogen sulfide, and in their removal from water.

mariculture
cultivation of fish and shellfish in estuarine and coastal areas. Compare aquiculture.

marsh
an area periodically inundated and treeless and often characterized by grasses, cattails, and other monocotyledons

MCL - Maximum Contaminant Level
the maximum level of a contaminant allowed in water by federal law. Based on health effects and currently available treatment methods.

MEDIA
The selected materials in a filter that form the barrier to the passage of certain suspended solids or dissolved molecules.

median streamflow
the rate of discharge of a stream for which there are equal numbers of greater and lesser flow occurrences during a specified period.

MEDIUM
Singular form of media.

melting
the changing of a solid into a liquid.

meltwater
water that comes from the melting ice of a glacier or a snowbank.

meteoric water
new water derived from the atmosphere.

mermaid
a fabled marine creature usually represented as having the head, trunk, and arms of a woman and a lower part like the tail of a fish.

method blank
laboratory grade water taken through the entire analytical procedure to determine if samples are being accidentally contaminated by chemicals in the lab

MG/L
The abbreviation for milligrams per liter.

micrograms per liter - Ug/L
micrograms per liter of water. One thousands micrograms per liter is equivalent to 1 milligram per liter. This measure is equivalent to parts per billion (ppb)

MICRON
A linear measure equal to one millionth of a meter.

MICRON RATING
The term applied to a filter to indicate the particle size of suspended solids that will be removed. As used in industry standards, this is an "absolute" not nominal rating.

migration
the movement of oil, gas, contaminants, water, or other liquids through porous and permeable rock.

MILLIGRAM PER LITER (mg/l)
A unit concentration of matter used in reporting the results of water and waste water analysis. In diluted water solutions it is practically equal to the part per million, but varies from he ppm in concentrated solution such as brine. As most analysis are performed on measured volumes of water the mg/l is a more accurate expression of the concentration, and is the preferred unit of measure.

MILLI MICRON
A unit of length equal to one thousandth of a micron, often used to express the wavelengths of colors of visible light in colorimetric analytical procedures. The symbol for the millimicron is "mu".

MINERAL
A term applied to inorganic substances (such as rocks and similar matter) found in the earth strata, as opposed to organic substances such as plant and animal matter. Minerals normally have definite chemical composition and crystal structure. The term is also applied to matter derived from minerals, such as the inorganic ions found in water. The term has been incorrectly applied to ion exchangers, even though most of the modern materials are organic ion exchange resins.

MOLE
The molecular weight of a chemical compound expressed in grams.

MOLECULE
The simplest combination of atoms that will form a specific chemical compound; the smallest particle of a substance which will still retain the essential composition and properties of that substance, and which can be broken down only into atoms and simpler substances.

MOST PROBABLE NUMBER (MPN)
The term used to indicate the number of organisms which, according to statistical theory, would be most likely to produce the results observed in certain bacteriological tests; usually expressed as a number in 100 ml of water.

municipal sewage
sewage from a community which may be composed of domestic sewage, industrial wastes or both.

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natural flow
the rate of water movement past a specified point on a natural stream. The flow comes from a drainage area in which there has been no stream diversion caused by storage, import, export, return flow, or change in consumptive use caused by man-controlled modifications to land use. Natural flow rarely occurs in a developed country.

natural resource
any form of matter or energy obtained from the environment that meets human needs.

NEGATIVE CHARGE
The electrical charge on an electrode or ion in solution due to the presence of an excess of electrons.

NEUTRAL
In electrical systems, the term used to indicate neither an excess nor a lack of electrons; a condition of balance between positive and negative charges. In chemistry, the term used to indicate a balance between acids and bases; the neutral point on the pH scale is 7.0, indicating the presence of equal numbers of free hydrogen (acidic) and hydroxide (basic) ions.

NEUTRALIZATION
In general, the addition of either and acid or a base to a solution as required to produce a neutral solution. The use of alkaline or basic materials to neutralize the acidity of some waters is a common proactive in water conditioning.

NIPDWR
National Interim Primary Drinking Water Regulations.

NITRATE NITROGEN
Nitrates are commonly found in well water from agricultural areas. It comes from fertilizers, industrial wastes, septic systems, and animal wastes. High amounts of nitrate effect the bloods ability to carry oxygen. Most susceptible are infants where nitrate poisoning can cause death by a health diagnosis known as "The Blue Baby Syndrome." The EPA has a set maximum contaminant level of 10 ppm for Nitrate Nitrogen.

nitrogen
a plant nutrient that can cause an overabundance of bacteria and algae when high amounts are present, leading to a depletion of oxygen and fish kills. Several forms occur in water, including ammonia, nitrate, nitrite or elemental nitrogen. High levels of nitrogen in water are usually caused by agricultural runoff or improperly operating wastewater treatment plants. Also see phosphorous.

NON CARBONATE HARDNESS
Water hardness due to the presence of compounds such as calcium and magnesium chlorides, sulfates or nitrates; the excess of total hardness over total alkalinity.

nonconsumptive use
using water in a way that does not reduce the supply. Examples include hunting, fishing, boating, water-skiing, swimming, and some power production. Compare consumptive use.

noncontact recreation
recreational pursuits not involving a significant risk of water ingestion, including fishing, commercial and recreational boating, and limited body contact incidental to shoreline activity. Compare contact recreation.

nonporous
something which does not allow water to pass through it. Compare porous.

nonpoint source
source of pollution in which wastes are not released at one specific, identifiable point but from a number of points that are spread out and difficult to identify and control. Compare point source.

nonpotable
not suitable for drinking. Compare potable.

nonthreshold pollutant
substance or condition harmful to a particular organism at any level or concentration.

NPDES permit
permit issued under the National Pollutant Discharge Elimination System for companies discharging pollutants directly into the waters of the United States.

NTU
nephlometric turbidity units.

nutrient
as a pollutant, any element or compound, such as phosphorous or nitrogen, that fuels abnormally high organic growth in aquatic ecosystems. Also see eutrophic.

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oligotrophic
having a low supply of plant nutrients. Compare eutrophic.

open system
system in which energy and matter are exchanged between the system and its environment, for example, a living organism.

OPERATING PRESSURE
The range of pressure, usually expressed in pounds per square inch, over which a water conditioning device or water system is designed to function.

organic chemicals
chemicals containing carbon.

orogeny
period of mountain-building.

orographic precipitation
rainfall that occurs as a result of warm, humid air being forced to rise by topographic features such as mountains. Precipitation on the Edwards Plateau is slightly higher because of the orographic effect of the escarpment and hills.

OSMOSIS
A process of diffusion of a solvent (such as water ) through a semi-permeable membrane which will transmit the solvent but impede most dissolved substances. The normal flow of solvent is from the dilute solution to the concentrated solution.

outcrop
exposed at the surface. The Edwards limestone outcrops in its recharge zone.

outfall
the place where a wastewater treatment plant discharges treated water into the environment.

outwash
a deposit of sand and gravel formed by streams of meltwater flowing from a glacier.

oxygen demanding waste
organic water pollutants that are usually degraded by bacteria if there is sufficient dissolved oxygen (DO) in the water.

OXIDATION
A chemical process in which electrons are removed from an atom, ion or compound. The addition of oxygen is a specific form of oxidation. Combustion is an extremely rapid form of oxidation, while the rusting of iron is a slow form.

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PARTICLE SIZE
As used in industry standards, the size of a particle suspended in water as determined by its smallest dimension, usually expressed in microns.

PARTS PER MILLION (ppm)
A common basis for reporting the results of water and waste water analyses, indicating the number of parts by weight of a dissolved or suspended constituent, per million parts by weight or 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.

PATHOGEN
An organism which may cause disease.

peak flow
in a wastewater treatment plant, the highest flow expected to be encoutered under any operational conditions, including periods of high rainfall and prolonged periods of wet weather.

perched water table
groundwater standing unprotected over a confined zone.

percolation
the movement of water through the subsurface soil layers, usually continuing downward to the groundwater or water table reservoirs.

percolating waters
waters passing through the ground beneath the Earth's surface without a definite channel.

perfected water right
a water right which indicates that the uses anticipated by an applicant, and made under permit, were made for beneficial use. Usually it is irrevocable unless voluntarily canceled or forfeited due to several consecutive years of nonuse.

perennial stream
one that flows all year round. Compare intermittent stream.

PERMANENT HARDNESS
Water hardness due to the presence of the chlorides and sulfates of calcium and magnesium, which will not be precipitated by boiling. This term is largely replaced by "noncarbonate hardness."

permeability
the ability of a water bearing material to transmit water. It is measured by the quantity of water passing through a unit cross section, in a unit time, under 100 percent hydraulic gradient.

pH
The reciprocal of the logarithm of the hydrogen ion concentration. The pH scale is from zero to 14, and 7.0 is the neutral point, indicating the presence of equal concentrations of free hydrogen and hydroxide ions. pH values below 7.0 indicate increasing acidity, and pH values above 7.0 indicate increasing base concentrations.

phosphorous
a plant nutrient that can cause an overabundance of bacteria and algae when high amounts are present, leading to a depletion of oxygen and fish kills. High levels of phosphorous in water are usually caused by agricultural runoff or improperly operating wastewater treatment plants. Also see nitrogen.

phreatophytes
plants that send their roots into or below the capillary zone to use ground water.

physical weathering
breaking down of parent rock into bits and pieces by exposure to temperature and changes and the physical action of moving ice and water, growing roots, and human activities such as farming and construction. Compare chemical weathering.

phytoplankton
free-floating, mostly microscopic aquatic plants.

piezometroc surface
the imaginary surface to which groundwater rises under hydrostatic pressure in wells or springs.

plankton
microscopic floating plant and animal organisms of lakes, rivers, and oceans.

plate tectonics
refers to the folding and faulting of rock and flow of molten lava involving lithospheric plates in the earth's crust and upper mantle.

plug
cement, grout, or other material used to fill and seal a hole drilled for a water well.

plume
the area taken up by contaminant(s) in an aquifer.

pluvial
pertaining to precipitation.

point source
source of pollution that involves discharge of wastes from an identifiable point, such as a smokestack or sewage treatment plant. Compare nonpoint source.

pollution
undesireable change in the physical, chemical, or biological characteristics of the air, water, or land that can harmfully affect the health, survival, or activities of human or other living organisms.

pond
a body of water usually smaller than a lake and larger than a pool either naturally or artificially confined.

porous
something which allows water to pass through it. Compare nonporous.

PORTABLE EXCHANGE
A term applied to water softeners and filters which are designed for connection to a water system with special fittings, and disconnection and transport to a central station or plant for regeneration or servicing.

POSITIVE CHARGE
The electrical charge on an electrode or ion in solution due to the removal of electrons.

potable
suitable, safe, or prepared for drinking. Compare non-potable.

ppb - parts per billion
number of parts of a chemical found in one billion parts of a solid, liquid, or gaseous mixture. Equivalent to micrograms per liter (Ug/L).

PPM
The abbreviation for part per million.

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.

preservative
a chemical added to a water sample to keep it stable and prevent compounds in it from changing to other forms or to prevent microorganism densities from changing prior to analysis.

PRESSURE DIFFERENTIAL
The difference in pressure between two points in a system due to differences in elevation and/or pressure drop due to flow.

PRESSURE DROP
A decrease in water pressure during flow due to internal friction between molecules of water, and external friction due to irregularities or roughness in surfaces past which the water flows.

price at equilibrium
where supply and demand curves intersect. The price at equilibrium is what allocates resources.

primary treatment
mechanical treatment in which large solids are screened out and suspended solids in the sewage settle out as sludge. Compare secondary treatment, tertiary treatment.

priority date
the date of establishment of a water right. It is determined by adjudication of rights established before the passage of the Water Code. The rights established by application have the application date as the date of priority.

profundal zone
a lake's deep-water region that is not penetrated by sunlight.

puddle
a small pool of water, usually a few inches in depth and from several inches to several feet in its greatest dimension.

pump
a device which moves, compresses, or alters the pressure of a fluid, such as water or air, being conveyed through a natural or artificial channel.

pumped hydroelectric storage
storing water for future use in generating electricity. Excess electrical energy produced during a period of low demand is used to pump water up to a reservoir. When demand is high, the water is released to operate a hydroelectric generator.

purge
to force a gas through a water sample to liberate volatile chemicals or other gases from the water so their level can be measured.

purgeable organics
volatile organic chemicals which can be forced out of the water sample with relative ease through purging.

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q uarry water
the moisture content of freshly quarried stone, esp. if porous.

quicksilver water
a solution of mercury nitrate used in gilding.

quickwater
the part of a stream that has a strong current; an artificial current or bubbling patch of water just astern of a moving boat.

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rain
water drops which fall to the earth from the air.

rain gage
any instrument used for recording and measuring time, distribution, and the amount of rainfall.

RATED CAPACITY
The basis for calculating the number of gallons delivered by a water softener between regeneration's, or amount of time between servicing of a filter, as determined under specific test conditions.

RATED PRESSURE DROP
The pressure drop of a freshly regenerated and/or backwashed water softener or filter at the rated service flow, with clean water at a temperature of 60 F, as determined under standard test conditions.

RATED SERVICE FLOW
The manufacturer's specified maximum flow rate at which a water softener will deliver soft water, or a filter will deliver quality water (as specified for its type) as determined under standard test conditions. A manufacturer may also specify a minimum flow rate or a range of service flows.

RATED SOFTENER CAPACITY
A water softener capacity rating based on grains of hardness removed while producing soft water between successive regeneration's, and related to the pounds of salt required for each regeneration as determined under standard test conditions.

RAW WATER
Untreated water, or any water before it reaches a specific water treatment device or process.

RCRA
Resource Conservation and Recovery Act - federal legislation requiring that hazardous waste be tracked from "cradle" (generation) to "grave" (disposal).

receiving waters
a river, ocean, stream, or other watercourse into which wastewater or treated effluent is discharged.

recharge
refers to water entering an underground aquifer through faults, fractures, or direct absorption.

recharge zone
the area where a formation allows available water to enter the aquifer. Generally, that area where the Edwards Aquifer and associated limestones crop out in Kinney, Uvalde, Medina, Bexar, Comal, Hays, Travis, and Williamson counties and the outcrops of other formations in proximity to the Edwards limestone, where faulting and fracturing may allow recharge of the surface waters to the Edwards Aquifer.

reclaimed water
domestic wastewater that is under the direct control of a treatment plant owner/operator which has been treated to a quality suitable for a beneficial use.

recurrence interval
average amount of time between events of a given magnitude. For example, there is a 1% chance that a 100-year flood will occur in any given year.

REDUCTION
A chemical process in which electrons are added to an atom, ion or compound.

RED WATER
Water which has a reddish or brownish appearance due to the presence of precipitated iron and/or iron bacteria.

REGENERANT
A solution of chemical compound used to restore the capacity of an ion exchange system. Sodium chloride brine is used as a regenerate for ion exchange water softeners; acids and bases are used as regenerants for the cation and anion resins used in demineralization.

REGENERATION
In general, includes the backwash, brine, and fresh water rinse steps necessary to prepare a water softener exchange bed for service after exhaustion. Specifically, the term may be applied to the "brine" step in which the sodium chloride solution is passed through the exchanger bed. The term may also be used for similar operations relating to demineralizers and certain filters.

REGENERATION LEVEL
The quantity of regenerant used in regeneration of an ion exchange unit or system, usually expressed in pounds per regeneration and/or pounds per regeneration per cubic foot of ion exchange.

reserves
amount of a particular resource in known locations that can be extracted at a profit with present technology and prices.

reservoir
a pond, lake, tank, or basin (natural or human made) where water is collected and used for storage. Large bodies of groundwater are called groundwater reservoirs; water behind a dam is also called a reservoir of water.

RESIDUAL
The amount of a specific material remaining in the water following a water treatment process. May refer to material remaining as a result of incomplete removal (see Leakage) or to material meant to remain in the treated water (see Residual Chlorine).

RESIDUAL CHLORINE
The amount of chlorine found in the water after treatment.

RESIN
Synthetic organic ion exchange material, such as the high capacity cation exchange resin widely used in water softeners.

REVERSE DEIONIZATION
The use of the anion exchange resin ahead of the cation exchange resin (the reverse of the usual order ) in a deionization system.

REVERSE OSMOSIS
A process for the removal of dissolved ions from water, in which pressure is used to force the water through a semi-permeable membrane, which will transmit the water by reject most other dissolved materials.

right of free capture
the idea that the water under a person's land belongs to that person and they are free to capture and use as much as they want. Also called the "law of the biggest pump".

riparian water right
the legal right held by an owner of land contiguous to or bordering on a natural stream or lake, to take water from the source for use on the contiguous land.

riparian zone
a stream and all the vegetation on its banks.

river
a natural stream of water of considerable volume.

river basin
the area drained by a river and its tributaries.

runoff
surface water entering rivers, freshwater lakes, or reservoirs.

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SALINE WATER
Water containing an excessive amount of dissolved salts, usually over 10,000 mg/1.

salinity
amount of dissolved salts in a given volume of 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 which can be formed by the neutralization of an acid with a base.

sanitary landfill
landfill that is lined with plastic or concrete or located in clay-rich soils to prevent hazardous substances from leaking into the environment.

saturation
the condition of a liquid when it has taken into solution the maximum possible quantity of a given substance at a given temperature and pressure.

seal
the impermeable material, such as cement grout bentonite, or puddling clay placed in the annular space between the borehole wall and the casing of a water well to prevent the downhole movement of surface water or the vertical mixing of artestian waters.

secondary treatment
second step in most waste treatment systems, in which bacteria break down the organic parts of sewage wastes; usually accomplished by bringing the sewage and bacteria together in trickling filters or in the activated sludge process. Compare primary treatment, tertiary treatment. Compare primary treatment, tertiary treatment.

sediment
soil particles, sand, and minerals washed from the land into aquatic systems as a result of natural and human activities.

sedimentary cycle
biogeochemical cycle in which materials primarily are moved from land to sea and back again.

sedimentation
a large scale water treatment process where heavy solids settle out to the bottom of the treatment tank after flocculation.

seep
a spot where water contained in the ground oozes slowly to the surface and often forms a pool; a small spring.

separate sewer
a sewer system that carries only sanitary sewage, not stormwater runoff. When a sewer is constructed this way, wastewater treatment plants can be sized to treat sanitary wastes only and all of the water entering the plant receives complete treatment at all times. Compare combined sewer.

septic tank
underground receptacle for wastewater from a home. The bacteria in the sewage decopose the organic wastes, and the sludge settles to the bottom of the tank. The effluent flows out of the tank into the ground through drains.

SEQUESTER
A chemical reaction in which certain ions are bound into a stable, water soluble compound, thus preventing undesirable action by the ions.

SEQUESTERING AGENT
A chemical compound sometimes fed into water to tie up undesirable ions, keep them in solution, and eliminate or reduce the normal effects of the ions. For example, polyphosphates can sequester hardness and prevent reactions with soap.

settleable solids
in sewage, suspended solids that will settle when the sewage is brought to a quiet state for a reasonable length of time, usually two hours.

SILICA
Silica can be found in water as a natural forming mineral or an additive to public water supplies. Silica is not regulated by the EPA and does not cause any health concerns. However, silica can cause spotting of glassware, fixtures, and automobiles during the cleaning process.

siltation
the deposition of finely divided soil and rock particles upon the bottom of stream and river beds and reservoirs.

sleet
precipitation which is a mixture of rain and ice.

slickensides
a smooth striated polished surface produced on rock by movement along a fault.

sludge
solid matter that settles to the bottom of sedimentation tanks in a sewage treatment plant and must be disposed of by digestion or other methods or recycled to the land.

snow
precipitation in the form of branched hexagonal crystals, often mixed with simple ice crystals, which fall more or less continuously from a solid cloud sheet. These crystals may fall either separately or in cohesive clusters forming snowflakes.

SOAP
One of a class of chemical compounds which possesses cleaning properties, formed by the reaction of a fatty acid with a base or alkali. Sodium and potassium soaps are soluble and useful, but can be converted to insoluble calcium and magnesium soaps (curd) by the presence of these hardness ions in water.

SODA ASH
The common name for sodium carbonate, a chemical compound used as an alkaline builder in come soap and detergent formulations; to neutralize acid water,; and in the lime-soda ash water treatment process.

SODIUM
An ion found in natural water supplies, and introduced to water in the ion exchange water softening process. Sodium compounds are highly soluble, and do not react with soaps or detergents. The effects of Sodium are not clearly understood. A high sodium intake can effect your blood pressure and cause stress. The EPA has set a maximum contaminant level of 20 ppm for people who have a sodium restricted diet.

SODIUM CHLORIDE
The chemical name for common salt, widely used in the regeneration of ion exchange water softeners.

SOFT WATER
Any water which contains less than 1.0 fpf (17/1 mg/1) of hardness minerals, expressed as calcium carbonate.

SOFTENED WATER
Any water that is treated to reduce hardness minerals to 1.0 gpg (17/1 mg/1) or less, expressed as calcium carbonate.

soil erosion
the processes by which soil is removed from one place by forces such as wind, water, waves, glaciers, and construction activity and eventually deposited at some new place.

SOLUTE
The substance which is dissolved in a solvent. Dissolved solids, such as the minerals found in water, are solutes.

SOLVENT
The liquid, such as water, in which other materials (solutes ) are dissolved.

specific conductance
a measure of the ability of a water to conduct an electrical current. Specific conductance is related to the type and concentration of ions in solution and can be used for approximating the dissolved solids concentration in water. In general, for the San Antonio River basin, conductivity * .6 approximates TDS. People monitoring water quality can measure electrical conductivity quickly in the field and estimate TDS without doing any lab tests at all. See TDS.

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.

specific heat
the amount of heat required to raise the temperature of a kilogram of a substance (water) by 1 degree Celsius.

spillway
the channel or passageway around or over a dam through which excess water is diverted.

spray irrigation
application of finely divided water droplets to crops using artificial means.

spring
an issue of water from the earth; a natural fountain; a source of a body or reservoir of water.

standard solution
any solution in which the concentration is known.

stormwater discharge
precipitation that does not infiltrate into the ground or evaporate due to impervious land surfaces but instead flows onto adjacent land or water areas and is routed into drain/sewer systems.

stream
a general term for a body of flowing water.

stream segment
refers to the surface waters of an approved planning area exhibiting common biological, chemical, hydrological, natural, and physical characteristics and processes. Segments will normally exhibit common reactions to external stress such as discharge or pollutants.

streamflow
the discharge that occurs in a natural channel.

sublimation
the transition of water directly from the solid state to the gaseous state, without passing through the liquid state; or vice versa. Compare condensation, evaporation.

subsidence
sinking down of part of the earth's crust due to underground excavation, such as removal groundwater.

SULFATE
Sulfate is a natural forming mineral found in water. Sulfate effects the taste of water, and when combined with bacteria or heated (water heater) may effect the odor. High levels of Sulfate may impact the digestion system causing a laxative effect. The EPA maximum contaminant level for sulfate in water is 250 ppm.

SULFATE-REDUCING BACTERIA
A group of bacteria which are capable of reducing sulfates in water to hydrogen sulfide gas, thus producing obnoxious tastes and odors. These bacteria have no sanitary significance, and are classed as nuisance organisms.

SULFUR
A yellowish solid element. The term is also used as a slang expression to refer to water containing hydrogen sulfide gas.

supply
a schedule that shows the various quantities of things offered for sale at various prices at a point in time. Compare demand.

surface impoundment
an indented area in the land's surface, such a pit, pond, or lagoon.

surface irrigation
application of water by means other than spraying such that contact between the edible portion of any food crop and the irrigation water is prevented.

surface water
water that flows in streams and rivers and in natural lakes, in wetlands, and in reservoirs constructed by humans.

sustainable management
method of exploiting a resource that can be carried on indefinitely. Removal of water from an aquifer in excess of recharge is, in the long term, not a sustainable management method.

sustained overdraft
long term withdrawal from the aquifer of more water than is being recharged.

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TANNIN
Tannin is a common natural occurrence in well water. Tannin is produced by decaying vegetation in the well system. It causes the water to have a yellow of light brown color and can provide a bitter taste. There is currently no EPA regulatory level for tannin in water.

TDS
The abbreviation for total dissolved solids. Please see TOTAL DISSOLVED SOLIDS.

Technology-based treatment requirements
NPDES permit requirements based on the application of pollution treatment or control technologies including BTP (best practicable technology), BCT (best conventional technology), BAT (best available technology economically achievable), and NSPS (new source performance standards).

Tertiary treatment
removal from wastewater of traces or organic chemicals and dissolved solids that remain after primary treatment and secondary treatment.

thalweg
the line of maximum depth in a stream. The thalweg is the part that has the maximum velocity and causes cutbanks and channel migration.

thermal gradient
temperature difference between two areas.

thermal pollution
an increase in air or water temperature that disturbs the climate or ecology of an area.

thermocline
fairly thin zone in a lake that separates an upper warmer zone (epilimnion) from a lower colder zone (hypolimnion).

THRESHOLD
A very low concentration of a substance in water. The term is sometimes used to indicate the concentration which can just be detected.

threshold pollutant
substance that is harmful to a particular organism only above a certain concentration, or threshold level.

TITRATION
An analytical process in which a standard solution in a calibrated vessel is added to a measured volume of sample until an endpoint, such as a color change, is reached. From the volume of the sample and the volume of standard solution used, the concentration of a specific material may be calculated.

TOTAL ACIDITY
The total of all forms of acidity, including mineral acidity, carbon dioxide, and acid salts. Total acidity is usually determined by titration with a standard base solution to the phenolphthalein endpoint (pH 8.3).

TOTAL ALKALINITY
The alkalinity of a water as determined by titration with standard acid solution to the methyl orange endpoint (pH approximately 4.5); sometimes abbreviated as "M alkalinity." Total alkalinity includes many alkalinity components, such as hydroxides, carbonates, and bicarbonates.

TOTAL DISSOLVED SOLIDS (TDS)
The weight of solids per unit volume of water which are in true solution; usually determined by the evaporation of a measured volume of filtered water and determination of the residue weight. Total Dissolved Solids is a measurement of any minerals or salts in the water. Bicarbonate, Chloride, Sulfate, Calcium, Magnesium, Sodium are the major components of dissolved solids in water. High amounts of these salts provide the major cause of water taste problems. High TDS can cause the water to appear inappropriate to drink, and spotting of glassware, fixtures, or painted surfaces such as automobiles. Also high dissolved solids can diminish the life of home appliances. The EPA has set a maximum contaminant level of 500 ppm.

TOTAL HARDNESS
The sum of all hardness constituents in a water, expressed as the equivalent concentration of calcium carbonate. Primarily due to calcium and magnesium in solution, but may include small amounts of metals such as iron which can act like calcium and magnesium in certain reactions.

TOTAL SOLIDS
The weight of all solids ( dissolved and suspended, organic and inorganic) per unit volume of water; usually determined by the evaporation of a measured volume of water at 105 C in a pre-weighed dish.

Toxicity Reduction Evaluation (TRE)
a study conducted to determine the source(s) of toxicity in a discharge effluent so that these sources can be controlled sufficiently to allow a discharger to comply with their permit limits.

toxicity test
the means to determine the toxicity of a chemical or an effluent using living organisms. A toxicity test measures the degree of response of an exposed test organism to a specified chemical or effluent.

Tragedy of the Commons
the idea that no one takes responsibility for things that everybody owns.

transmissivity
refers to the rate at which limestone allows the transmission of water. Limestone can be highly porous, but not very transmissive if the pores are not connected to each other. Technically speaking, it is the rate at which water is transmitted through a unit width of aquifer under unit hydraulic gradient. Transmissivity is directly proportional to aquifer thickness, thus it is high where the Edwards is thick and low where it is thin, given the same hydraulic conductivity.

transpiration
direct transfer of water from the leaves of living plants to the atmosphere. Distinguish evapotranspiration.

tributary
a stream that contributes its water to another stream or body of water.

turbid
thick or opaque with matter in suspension. Rivers and lakes may become turbid after a rainfall.

TURBIDITY
A measure of the amount of finely divided suspended matter in water, which causes the scattering and adsorption of light rays.

troposphere
the layer of atmosphere closest to the Earth, extending seven to ten miles above the surface, containing most of the clouds and moisture.

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USGS
United States Geological Survey

unclassified waters
those waters for which no classification has been assigned and which have not been identified in Appendix A of 31 Texas Administrative Code, Chapter 307.10 of Title 31 (relating to definitions).

unconsolidated formations
naturally occurring earth formations that have not been lithified. Alluvium, soil, gravel, clay, and overburden are some of the terms used to describe this type of formation.

undercurrent
a current below the upper currents or surface of a fluid body.

underdrain
a concealed drain with openings through which the water enters when the water table reaches the level of the drain.

underflow
movement of water through subsurface material.

undertow
the current beneath the surface that sets seaward or along the beach when waves are breaking on the shore.

underwater
under the surface of the water; lying, growing, performed, worn, or operating below the surface of the water, as underwater caverns, underwater operation of a submarine.

upflow
an upward flow.

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vested water right
the right granted by a state water agency to use either surface or ground water.

virgin flow
the streamflow which exists orwould exist if man had not modified the conditions on or along the stream or in the drainage basin.

void
the pore space or other openings in rock. The openings can be very small to cave size and are filled with water below the water table.

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wastewater
water containing waste including greywater, blackwater or water contaminated by waste contact, including process-generated and contaminated rainfall runoff.

water
the liquid that descends from the clouds as rain; forms streams, lakes, and seas, and is a major constituent of all living matter. It is an odorless, tasteless, colorless, very slightly compressible liquid.

water cycle
natural pathway water follows as it changes between liquid, solid, and gaseous states; biogeochemical cycle that moves and recycles water in various forms through the ecosphere. Also called the hydrologic cycle.

water pollution
degradation of a body of water by a substance or condition to such a degree that the water fails to meet specified standards or cannot be used for a specific purpose.

water quality-based toxics control
an integrated strategy used in NPDES permitting to assess and control the discharge of toxic pollutants to surface waters. There are two approaches: the whole-effluent approach involves the use of toxicity tests to measure discharge toxicity; the chemical specific approach involves the use of water quality criteria or State standards to limit specific toxic pollutants directly.

water quality criteria
scientifically derived ambient limits developed and updated by EPA, under section 304(a)(1) of the Clean Water Act, for specific pollutants of concern. Criteria are recommended concentrations, levels, or narrative statements that should not be exceeded in a waterbody in order to protect aquatic life or human health.

water quality standards
laws or regulations, promulgated under Section 303 of the Clean Water Act, that consist of the designated use or uses of a waterbody or a segment of a waterbody and the water quality criteria that are necessary to protect the use or uses of that particular waterbody. Water quality standards also contain an antidegradation statement. Every State is required to develop water quality criteria standards applicable to the various waterbodies within the State and revise them every 3 years.

water table
level below the earth's surface at which the ground becomes saturated with water. The surface of an unconfined aquifer which fluctuates due to seasonal precipitation.

water table aquifer
an aquifer confined only by atmospheric pressure (water levels will not rise in the well above the confining bed).

water well
any artificial excavation constructed for the purpose of exploring for or producing ground water.

water year
the 12-month period, usually October 1 through September 30. The water year is designated by the calendar year in which it ends and which includes 9 of the 12 months. Thus, the year ending September 30, 1998 is called the1998 Water Year.

waterfall
a sudden, nearly vertical drop in a stream, as it flows over rock.

waterlogging
saturation of soil with irrigation water so the water table rises close to the surface.

watermaster
An employee of a water department who distributes available water supply at the request of water right holders and collects hydrographic data.

watershed
land area from which water drains toward a common watercourse in a natural basin.

weather
day to day variation in atmospheric conditions. Compare climate.

wetland
area that is regularly wet or flooded and has a water table that stands at or above the land surface for at least part of the year, such as a bog, pond, fen, estuary, or marsh.

whole-effluent toxicity
the aggregate toxic effect of an effluent measured directly by a toxicity test.

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Xeriscape
creative landscaping for water and energy efficiency and lower maintenance. The seven xeriscape principles are: good planning and design; practical lawn areas; efficient irrigation; soil improvement; use of mulches; low water demand plants; good maintenance.

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Yield
the quantity of water expressed either as a continuous rate of flow (cubic feet per second, etc.) or as a volume per unit of time. It can be collected for a given use, or uses, from surface or groundwater sources on a watershed.

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Zero discharge water
The principle of “zero discharge” is recycling of all industrial wastewater. This means that wastewater will be treated and used again in the process. Because of the water reuse wastewater will not be released on the sewer system or surface water.

Zeta potential
An electrokinetic measurement which can be used for the control of coagulation processes.

ZINC
Zinc is a product of a corrosive or aggressive water that is in contact with a galvanized plumbing system. Zinc can effect the taste and color of the water. The EPA maximum contaminant level for zinc is 5.0 ppm.

Zone of aeration
a region in the Earth above the water table. Water in the zone of aeration is under atmospheric pressure and will not flow into a well.

Z one of saturation
the space below the water table in which all the interstices (pore spaces) are filled with water. Water in the zone of saturation is called groundwater.

Zooplankton
Tiny aquatic animals eaten by fish.

Zwitter ions
Act as cations or as anions according to the environment in which they find themselves. In water technology they are usually organic macromolecules.

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