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Drinking Water Glossary O thru Z - Chehalis River Council

Office Of Water

Drinking Water Glossary

A Dictionary of Technical and Legal Terms Related to Drinking Water

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0

Occupational Safety and Health Act of 1970. See OSHA.
odor threshold. The minimum odor of a water sample that can just be detected after successive dilutions with odorless water. Also called THRESHOLD ODOR.
offstream uses. Water withdrawn from surface or ground water sources for use at another place.
offset (or DROOP). The difference between the actual value and the desired value (or set point); characteristic of proportional controllers that do not incorporate reset action.
OHM The unit of electrical resistance. The resistance of a conductor in which one volt produces a current of one ampere.
olfactory fatigue (oh-FAK-tore-ee). A condition in which a person's nose, after exposure to certain odors, is no longer able to detect the odor.
oligotrophic (AH-lig-o-TRO-flck). Reservoirs and lakes which are nutrient poor and contain little aquatic plant or animal life.
oncology. Study of cancer.
one-hit model Mathematical model based on the biological theory that a single "hit" of some minimum critical amount of a carcinogen at a cellular target- namely, DNA-can initiate an irreversible series of events, eventually leading to a tumor.
optimal corrosion control treatment The corrosion control treatment that minimizes the lead and copper concentrations at users' taps while insuring that the treatment does not cause the water system to violate any national primary drinking water regulations.
operation and maintenance costs. The ongoing, repetitive costs of operating a water system; for example, employee wages and costs for treatment chemicals and periodic equipment repairs.
oral. Of the mouth; through or by the mouth.
organic. Substances that come from animal or plant sources. Organic substances always contain carbon. (Inorganic materials are chemical substances of mineral origin.) Also see inorganic
organics. 1) A term used to refer to chemical compounds made from carbon molecules. These compounds may be natural materials (such as animal or plant sources) or manmade materials (such as synthetic organics). Also see organic. 2) Any form of animal or plant life. Also see bacteria.
organism. Any form of animal or plant life. Also see bacteria..
orifice (OR-uh-fiss). An opening (hole) in a plate, wall or partition An orifice flange or plate placed in a pipe consists of a slot or a calibrated circular hole smaller than the pipe diameter. The difference in pressure in the pipe above and at the orifice may be used to determine the flow in the pipe.
ORP.
Oxidation-Reduction Potential. The electrical potential required to transfer electrons from one compound or element (the oxidant) to another compound or element (the reductant); used as a qualitative measure of the state of oxidation in water treatment systems.
orthotolidine (or-tho-TOL-uh-dine). Orthotolidine is a calorimetric indicator of chlorine residual. If chlorine is present, a yellow-colored compound is produced. This reagent is no longer approved for chemical analysis.
OSHA (0-shuh). The Williams-Steiger Occupational Safety and Health Act of 1970 (OSHA) is a law designed to protect the health and safety of industrial workers and also the operators of water supply systems and treatment plants. OSHA also refers to the federal and state agencies which administrator the OSHA regulations.
osmosis (oz-MOE-sis). The passage of a liquid from a weak solution to a more concentrated solution across a semipermeable membrane. The membrane allows the passage of the solvent (water) but not the dissolved solids (solutes). This process tends to equalize the conditions on either side of the membrane.
overall efficiency pump. The combined efficiency of a pump and motor together. Also called the WIRE-TO-WATER EFFICIENCY.
overdraft The pumping of water from a groundwater basin or aquifer in excess of the supply flowing into the basin. This pumping results in a depletion or "mining" of the groundwater in the basin.
overflow rate. One of the guidelines for the design of settling tanks and clarifiers in treatment plants. Used by operators to determine if tanks and clarifiers are hydraulically (flow) over- or underloaded. Also called SURFACE LOADING. Overflow Rate (GDP/sq ft) = Flow (GPD)/Surface Area (sq ft)
overturn. The almost spontaneous mixing of all layers of water in a reservoir or lake when the water temperature becomes similar from top to bottom. This may occur in the fall/winter when the surface waters cool to the same temperature as the bottom waters and also in the spring when the surface waters warms after the ice melts.
oxidation (ox-uh-DAY-shun). Oxidation is the addition of oxygen, removal of hydrogen, or the removal of electrons from an element or compound. In the environment, organic matter is oxidized to more stable substances. The opposite of reduction
oxidation-reduction potential. The electrical potential required to transfer electrons from one compound or element (the oxidant) to another compound or element (the reductant); used as a qualitative measure of the state of oxidation in water treatment systems.
oxidizing agent Any substance, such as oxygen (O2) or chlorine (Cl2), that will readily add (take on) electrons. The opposite is a reducing agent.
ozonation (O-zoe-NAY-shun). The application of ozone to water for disinfection or for taste and odor control.

p

packed tower aeration. A method of treating water to remove volatile organic chemical (VOCs) contaminants. As water is mixed with air, VOCs move from water to air which then passes through carbon filters to trap the contaminants.
palatable (PAL-a-ta-ble). Water at a desirable temperature that is free from objectionable tastes, odors, colors, and turbidity. Pleasing to the senses.
parshall flume. A device used to measure the flow in an open channel. The flume narrows to a throat of fixed dimensions and then expands again. The rate of flow can be calculated by measuring the difference in head (pressure) before and at the throat of the flume.
particle count. The results of a microscopic examination of treated water with a special "particle counter" which classifies suspended particles by number and size.
particulate (par-TICK-you-let). A very small solid suspended in water which can vary widely in size, shape, density, and electrical charge. Colloidal and dispersed particulates are artificially gathered together by the processes of coagulation and flocculation.
partition coefficient. A measure of the extent to which a pesticide is divided between the soil and ater phases.
parts per million (PPM). Parts per million parts, a measurement of concentration on a weight or volume basis. This term is equivalent to milligrams per liter (mg/L) which is the preferred term.
Pascal. The pressure or stress of one newton per square meter. (Abbreviated Pa) 1 psi = 6895 Pa = 6.895 kN/sq m = 0.0703 kg/sq cm
pathogenic organisms (path-o-JEN-ick). Organisms, including bacteria, viruses or cysts, capable of causing diseases (typhoid, cholera, dysentery) in a host (such as a person). There are many types of organisms which do NOT cause disease. These organisms are called non-pathogenic.
pathogens. Microorganisms that can cause disease in other organisms or in humans, animals and plants. They may be bacteria, viruses, or parasites and are found in sewage in runoff from animal farms or rural areas populated with domestic and/or wild animals, and in water used for swimming. Fish and shellfish contaminated by pathogens, or the contaminated water itself, can cause serious illnesses.
pathology. The study of disease.
percent saturation. The amount of a substance that is dissolved in a solution compared with the amount that could be dissolved in the solution, expressed as a percent. Amount of substance that is dissolved x 100% Amount that could be dissolved in solution
percolating water (PURR-co-LAY-ting). Water that passes through soil or rocks under the force of gravity.
percolation (PURR-ko-LAY-shun). 1) The slow seepage of water into and through the ground. 2) The slow passage of water through a filter medium.
performance evaluation sample. A reference sample provided to a laboratory for the purpose of demonstrating that the laboratory can successfully analyze the sample within limits of performance specified by the Agency. The true value of the concentration of the reference material is unknown to the laboratory at the time of the analysis.
periphyton (puh-RIF-uh-tawn). Microscopic plants and animals that are firmly attached to solid surfaces under water such as rocks, logs, pilings and other structures.
permeability. Generally used to refer to the ability of rock or soil to transmit water.
permeate (PURR-me-ate). To penetrate and pass through, as water penetrates and passes through soil and other porous materials.
permissible dose. The dose of a chemical that may be received by an individual without the expectation of a significantly harmful result.
persistence. The resistance to degradation as measured by the period of time required for complete decomposition of a material.
person. An individual, corporation, company, association, partnership; municipality; or State, Federal, or tribal agency.
pesticide. Any substance or chemical designed or formulated to kill or control weeds or animal pests. Also see algicide, herbicide, insecticide and rodenticide.
petroleum derivatives. Chemicals formed when gasoline breaks down in contact with ground water.
pH (pronounce as separate letters). pH is an expression of the intensity of the basic or acid condition of a liquid. Mathematically, pH is the logarithm (base 10) of the reciprocal of the hydrogen ion concentration, [H+]. pH= Log (I/[H+]) The pH may range from 0 to 14, where 0 is most acid, 14 most basic, and 7 neutral. Natural waters usually have a pH between 6.5 and 8.5.
pharmacokinetics. The dynamic behavior of chemicals inside biological systems; it includes the processes of uptake, distribution, metabolism, and excretion.
phenolic compounds (
FEE-noll-LICK). Organic compounds that are derivatives of benzene.
phenolphthalein alkalinity (FEE-nol-THAY-leen). The alkalinity in a water sample measured by the amount of standard acid required to lower the pH to a level of 8.3, as indicated by the change in color of phenolphthalein from pink to clear. Phenolphthalein alkalinity is expressed as milligrams per liter equivalent calcium carbonate.
photosynthesis (foe-tow-SIN-thus-sis). A process in which organisms, with the aid of chlorophyll (green plant enzyme), convert carbon dioxide and inorganic substances into oxygen and additional plant material, using sunlight for energy. All green plants grow by this process.
phytoplankton (Flo-tow-PANK-ton). Small, usually microscopic plants (such as algae), found in lakes, reservoirs, and other bodies of water.
pico. A prefix used in the metric system and other scientific systems of measurement which means 10-12 or 0.000000000001
picocurie (pCi). A measure of radioactivity. One picocurie of radioactivity is equivalent to 0.037 nuclear disintegrations per second.
plan view. A diagram or photo showing a facility as it would appear when looking down on top of it.
plankton. 1) Small, usually microscopic, plants (phytoplankton) and animals (zooplankton) in aquatic systems. 2) All of the smaller floating, suspended or self-propelled organisms in a body of water.
plug flow. A type of flow that occurs in tanks, basins or reactors when a slug of water moves through a tank without ever dispersing or mixing with the rest of the water flowing through the tank.
plumes. The way polluted water extends downstream from the pollution source (analogous to smoke from a smokestack as it drifts downwind in the atmosphere).
point of disinfectant application. The point where disinfectant is applied and water downstream of that point is not subject to recontamination by surface water runoff.
point-of-entry treatment device. A treatment device applied to the drinking water entering a house or building for the purpose of reducing contaminants in the drinking water distributed throughout the house or building .
point-of-use treatment device. A treatment device applied to a single tap used for the purpose of reducing contaminants in drinking water at that one tap.
point source. A stationery location or fixed facility from which pollutants are discharged or emitted. Also, any single identifiable source of pollution, e.g., a pipe, ditch, ship, ore pit, factory smokestack.
pole shader. A copper bar circling the laminated iron core inside the coil of a magnetic starter.
pollutant. Generally, any substance introduced into the environment that adversely affects the usefulness of a resource.
pollution. Generally, the presence of matter or energy whose nature, location or quantity produces undesired environmental effects. Under the Clean Water Act, for example, the term is defined as the man-made or man-induced alteration of the physical, biological, and radiological integrity of water.
polyelectrolyte (POLLY-ee-LECK-tro-lite). A high- molecular-weight (relatively heavy) substance having points of positive or negative electrical charges that is formed by either natural or man-made processes. Natural polyelectrolytes may be of biological origin or derived from starch products and cellulose derivatives. Man-made polyelectrolytes consist of simple substances that have been made into complex substances of high molecular weight. Used with other chemical coagulants to aid in binding small suspended particles to larger chemical flocs for their removal from water. Often called a polymer.
polymer. A chemical formed by the union of many monomers (a molecule of low molecular weight). Polymers are used with other chemical coagulants to aid in binding small suspended particles to larger chemical flocs for their removal from water. All polyelectrolytes are polymers, but not all polymers are polyelectrolytes.
population at risk. A population subgroup that is more likely to be exposed to a chemical, or is more sensitive to a chemical, than is the general population.
pore. A very small open space in a rock or granular material. Also see interstice
porosity. the capacity of soil of rock to hold water.
positive displacement pump. A type of piston, diaphragm, gear or screw pump that delivers a constant volume with each stroke. Positive displacement pumps are used as chemical solution feeders.
postchlorination. The addition of chlorine to the plant effluent, FOLLOWING plant treatment, for disinfection purposes.
potency. Amount of material necessary to produce a given level of a deleterious effect.
potentiation. The effect of one chemical to increase the effect of another chemical.
potentiometric surface. The level to which water will rise in cased wells or other cased excavations into aquifers, measured as feet above mean sea level.
potable water. Water that is safe and satisfactory for drinking and cooking.
power factor. The ratio of the true power passing through an electric circuit to the product of the voltage and amperage in the circuit. This is a measure of the lag or load of the current with respect to the voltage.
ppb. Parts per billion. Also pg/L or micrograms per liter.
ppm. Parts per million. Also mg/L or milligrams per liter.
prechlorination. The addition of chlorine at the headworks of the plant PRIOR TO other treatment processes mainly for disinfection and control of tastes, odors and aquatic growths. Also applied to aid in coagulation and settling.
precipitate (pre-SIP-uh-TATE). 1) An insoluble, finely divided substance which is a product of a chemical reaction within a liquid. 2) The separation from solution of an insoluble substance.
precipitation (pre-SIP-uh-TAY-shun). 1) The process by which atmospheric moisture falls onto a land or water surface as rain, snow, hail, or other forms of moisture. 2) The chemical transformation of a substance in solution into an insoluble form (precipitate).
Precision. The ability of an instrument to measure a process variable and to repeatedly obtain the same result. The ability of an instrument to reproduce the same results.
precursor, THM (pre-CURSE-or). Natural organic compounds found in all surface and groundwaters. These compounds MAY react with halogens (such as chlorine) to form trihalomethanes (try-HAL-o-METH-hanes) (THMs); they MUST be present in order for THMs to form.
prescriptive (
pre-SKRIP-tive). Water rights which are acquired by diverting water and putting it to use in accordance with specified procedures. These procedures include filing a request to use unused water in a strewn, River or lake with a state agency.
pressure control. A switch which operates on changes in pressure. Usually this is a diaphragm pressing against a spring. When the force on the diaphragm overcomes the spring pressure, the switch is actuated (activated).
pressure head. The vertical distance (in feet) equal to the pressure (in psi) at a specific point. The pressure head is equal to the pressure in psi times 2.31 ft/psi.
prevalence study. An epidemiological study which examines the relationships between diseases and exposures as they exist in a defined population at a particular point in time.
primacy. The responsibility for ensuring that a law is implemented, and the authority to enforce a law and related regulations. A primacy agency has the primary responsibility for administrating and enforcing regulations.
primary element. An instrument which measures (senses) a physical condition or variable of interest. Floats and thermocouples are examples of primary elements. Also called a sensor.
prime. The action of filling a pump casing with water to remove the air. Most pumps must be primed before startup or they will not pump any water.
prior appropriation. A doctrine of water law that allocates the right to use water on a first-come first-serve basis.
process variable. A physical or chemical quantity which is usually measured and controlled in the operation of a water treatment plant or an industrial plant.
product water. Water that has passed through a water treatment plant. All the treatment processes are completed or finished. This water is the product from the water treatment plant and is ready to be delivered to the consumers. Also called finished water.
profile. A drawing showing elevation plotted against distance, such as the vertical section or side view of a pipeline.
prospective study. An epidemiological study which examines the development of disease in a group of persons determined to be presently free of the disease.
prussian blue. A blue paste or liquid (often on a paper like carbon paper) used to show a contact area. Used to determine if gate valve seats fit properly.
PSIG. Pounds per Square Inch Gage pressure. The pressure within a closed container or pipe measured with a gage in pounds per square inch. See gage pressure.
public water system. A system for the provision to the public of piped water for human consumption, If such system has at least fifteen service connections or regularly least 60 days out of the year. Such term includes: 1) any collection, treatment, storage, and distribution facilities under control of the operator of such system and used primarily in connection with such system, and 2) any collection or pretreatment storage facilities not under such control which are used primarily in connection with such system. A public water system is either a "community water system" or a "non-community water system.'
pumping station. Mechanical devices installed in sewer or water systems or other liquid-carrying pipelines that move the liquids to a higher level.
pumping water level. The vertical distance in feet from the centerline of the pump discharge to the level of the free pool while water is being drawn from the pool.
purveyor, water (purr-VAY-or). An agency or person that supplies water (usually potable water).
putrefaction (PEW-truh-FACK-shun). Biological decomposition of organic matter, with the production of illsmelling and tasting products, associated with anaerobic (no oxygen present) conditions.

Q

qualitative. Descriptive of kind, type or direction, as opposed to size, magnitude or degree.
quantitative. Descriptive of size, magnitude or degree.
quicklime. A material that is mostly calcium oxide (CaO) or calcium oxide in natural association with a lesser amount of magnesium oxide. Quicklime is capable of combining with water to form hydrated lime. Also see hydrated lime.

R

radial to impeller. Perpendicular to the impeller shaft. Material being pumped flows at a right angle to the impeller.
radical. A group of atoms that is capable of remaining unchanged during a series of chemical reactions. Such combinations (radicals) exist in the molecules of many organic compounds; sulfate (SO42-) is an inorganic radical.
radionuclide. Any man-made or natural element which emits radiation in the form of alpha or beta particles, or as gamma rays.
range. The spread from minimum to maximum values that an instrument is designed to measure. Also see span and effective range.
ranney collector. This water collector is constructed as a dug well from 12 to 16 feet (3.5 to 5 m) in diameter that has been sunk as a caisson near the bank of a River or lake. Screens are driven radially and approximately horizontally from this well into the sand and the gravel deposits underlying the river.
raw water. 1) Water in its natural state, prior to any treatment. 2) Usually the water entering the first treatment process of a water treatment plant.
reaeration (RE-air-A-shun). The introduction of air through forced air diffusers into the lower layers of the reservoir. As the air bubbles form and rise through the water, oxygen from the air dissolves into the water and replenishes the dissolved oxygen. The rising bubbles also cause the lower waters to rise to the surface where oxygen from the atmosphere is transferred to the water. This is sometimes called surface reaeration.
reagent (re-A-gent). A pure chemical substance that is used to make new products or is used in chemical tests to measure, detect, or examine other substances.
recarbonation (re-CAR-bun-NAY-shun). A process in which carbon dioxide is bubbled into the water being treated to lower the pH. The pH may also be lowered by the addition of acid. Recarbonation is the final stage in the lime-soda ash softening process. This process converts carbonate ions to bicarbonate ions and stabilizes the solution against the precipitation of carbonate compounds.
receiver. A device which indicates the result of a measurement. Most receivers in the water utility field use either a fixed scale and movable indicator (pointer) such as pressure gage or a movable scale and movable indicator like those used on a circular-flow recording chart. Also called an indicator.
receiving waters. All distinct bodies of water that receive runoff or wastewater discharges, such as streams, rivers, ponds, lakes, and estuaries.
receptor. 1) In biochemistry: a specialized molecule in a cell that binds a specific chemical with high specificity and high affinity. 2) In exposure assessment: an organism that receives, may receive, or has received environmental exposure to a chemical.
recharge. Process by which rain water (precipitation) seeps into the ground-water system.
recharge area. Generally, an area that is connected with the underground aquifer(s) by a highly porous soil or rock layer. Water entering a recharge area may travel for miles underground.
recharge rate. The quantity of water per unit time that replenishes or refills an aquifer.
recorder. A device that creates a permanent record, on a paper chart or magnetic tape, of the changes of some measured variable.
reducing agent. Any substance, such as base metal (iron) or the sulfide ion (S2-), that will readily donate (give up) electrons. The opposite is an oxidizing agent.
reduction (re-DUCK-shun). Reduction is the addition of hydrogen, removal of oxygen, or the addition of electrons to an element or compound. Under anaerobic conditions (no dissolved oxygen present), sulfur compounds are reduced to odor-producing hydrogen sulfide (H2S and other compounds. The opposite of oxidation.
reference. A physical or chemical quantity whose value is known exactly, and thus is used to calibrate or standardize instruments.
reliquifaction (re-LICK-we-FACK-shun).
rem. The unit of dose equivalent from ionizing radiation to the total body or any internal organ or organ system. A millirem (mrem)" is 1/1000 of a rem.
renal Pertaining to the kidney.
repeat compliance period. Any subsequent compliance period after the initial compliance period.
representative sample. A portion of material or water that is as nearly identical in content and consistency as possible to that in the larger body of material or water being sampled.
reservoir. Any natural or artificial holding area used to store; regulate, or control water.
residual chlorine. The amount of free and/or available chlorine remaining after a given contact time under specified conditions.
residual disinfectant concentration ("C" in CT calculations). The concentration of disinfectant measured in mg/L in a representative sample of water.
residue. The dry solids remaining after the evaporation of a sample of water or sludge. Also see total dissolved solids
respiration. The process in which an organism uses oxygen for its life processes and gives off carbon dioxide.
retrospective study. An epidemiological study which compares diseased persons with non-diseased persons and works back in time to determine exposures.
reverse osmosis (oz-MOE-sis). The application of pressure to a concentrated solution which causes the passage of a liquid from the concentrated solution to a weaker solution across a semipermeable membrane. The membrane allows the passage of the solvent (water) but not the dissolved solids (solutes). The liquid produced is a demineralized water. Also see osmosis.
reversible effect. An effect which is not permanent, especially adverse effects which diminish when exposure to a toxic chemical is ceased.
RfD (Reference dose). The daily exposure level which, during an entire lifetime of a human, appears to be without appreciable risk on the basis of all facts known at the time. Same as ADI.
rill. A small channel eroded into the soil surface by runoff, rills easily can be smoothed out (obliterated) by normal tillage.
riparian rights. A doctrine of state water law under which a land owner is entitled to use the water on or bordering his property, including the right to prevent diversion or misuse of upstream waters. Riparian land is land that borders on surface water.
risk. The potential for realization of unwanted adverse consequences or events.
risk assessment. A qualitative or quantitative evaluation of the environmental and/or health risk resulting from exposure to a chemical or physical agent (pollutant); combines exposure assessment results with toxicity assessment results to estimate risk.
risk characterization. Final component of risk assessment that involves integration of the data and analysis involved in hazard evaluation, dose-response evaluation, and human exposure evaluation to determine the likelihood that humans will experience any of the various forms of toxicity associated with a substance.
risk estimate. A description of the probability that organisms exposed to a specified dose of chemical will develop an adverse response (e.g., cancer).
risk factor. Characteristic (e.g., race, sex, age, obesity) or variable (e.g., smoking, occupational exposure level) associated with increased probability of a toxic effect.
risk management. Decisions about whether an assessed risk is sufficiently high to present a public health concern and about the appropriate means for control of a risk judged to be significant.
risk specific dose. The dose associated with a specified risk level.
rodenticide (row-DENT-uh-SIDE). Any substance or chemical used to kill or control rodents.
rotameter (RODE-uh-ME-ter). A device used to measure the flow rate of gases and liquids. The gas or liquid being measured flows vertically up a tapered, calibrated tube. Inside the tube is a small ball or bullet-shaped float (it may rotate) that rises or falls depending on the flow rate. The flow rate may be read on a scale behind or on the tube by looking at the middle of the ball or at the widest part or top of the float.
rotor. The rotating part of a machine. The rotor is surrounded by the stationary (non-moving) parts (stator) of the machine.
route of exposure. The avenue by which a chemical comes into contact with an organism (e.g., inhalation, ingestion, dermal contact, injection).
run-off. That part of precipitation, snow melt, or irrigation water that runs off the land into streams or other surface water. It can carry pollutants from the air and land into the receiving waters. saturation. The condition of a liquid (water) when it has

S

sacrificial anode. An easily corroded material deliberately installed in a pipe or tank. The intent of such an installation is to give up (sacrifice) this anode to corrosion while the water supply facilities remain relatively corrosion free.
safe. Condition of exposure under which there is a "practical certainty" that no harm will result in exposed individuals.
Safe Drinking Water Act (SDWA). Commonly referred to as SDWA. An Act passed by the U.S. Congress in 1974. The Act establishes a cooperative program among local, state and federal agencies to insure safe drinking water for consumers.
safe water. Water that does not contain harmful bacteria, or toxic materials or chemicals. Water may have taste and odor problems, color and certain mineral problems and still be considered safe for drinking.
safe yield . The annual quantity of water that can be taken from a source of supply over a period of years without depleting the source beyond its ability to be replenished naturally in "wet years".
salinity. 1)The relative concentration of dissolved salts, usually sodium chloride, in a given water.. 2) A measure of the concentration of dissolved mineral substances in water.
sand. Soil particles between 0.05 and 2 .0 mm in diameter.
sand filters. Devices that remove some suspended solids from sewage. Air and bacteria decompose additional wastes filtering through the sand so that cleaner water drains from the bed.
sanitary sewer. A sewer that transports only wastewaters (from domestic residences and/or industries) to a wastewater treatment plant.
sanitary survey. An on-site review of the water source, facilities, equipment, operation, and maintenance of a public water system for the purpose of evaluating the adequacy of the facilities for producing and distributing safe drinking water.
saprophytes (SAP-row-FIGHTS). Organisms living on dead or decaying organic matter. They help natural decomposition of organic matter in water.
saturated zone. The area below the water table where all open spaces are filled with water.
saturator (SAT-you-RAY-tore). A device which produces a fluoride solution for the fluoridation process. The device is usually a cylindrical container with granular sodium fluoride on the bottom. Water flows either upward or downward through the sodium fluoride to produce the fluoride solution.
schedule, pipe. A sizing system of arbitrary numbers that specifies the I.D. (inside diameter) and O.D. (outside diameter) for each diameter pipe. This term is used for steel, wrought iron, and some types of plastic pipe. Also used to describe the strength of some types of plastic pipe.
SCD (SWCD). Soil Conservation District (also called Soil and Water Conservation District in some areas); a local government entity with in a defined water or soil protection area tat provides assistance to farmers and other local residents in conserving natural resources, especially soil and water.
SCFM. Cubic Feet of air per Minute at Standard conditions of temperature, pressure and humidity (O degrees C /14.7 psia /50% relative humidity).
SCS. Soil Conservation Service. An agency of the United States Department of Agriculture that provides technical assistance for resource conservation to farmers, other Federal, state and local agencies, and to local soil conservation districts.
SDWA. See Safe Drinking Water Act.
secchi disc (SECK-key). A flat, white disc lowered into the water by a rope until it is just barely visible. At this point, the depth of the disc from the water surface is the recorded Secchi disc transparency.
seepage. The percolation of water through the soil from unlined channels, ditches, watercourses and water storage facilities.
sedimentation. A water treatment process in which solid particles settle out of the water being treated in a large clarifier or sedimentation basin .
sediment yield. The quantity of sediment arriving at a specific location.
seize up. Seize up occurs when an engine overheats and a part expands to the point where the engine will not run. Also called "freezing".
semi-confined aquifer. An aquifer that is partially confined by a soil layer (or layers) of low permeability through which recharge and discharge can occur.
sensor. An instrument that measure (senses) a physical condition or variable of interest. Floats and thermocouples are examples of sensors. Also called a primary element
septage. The liquid and semisolid contents removed by pumping from a septic tank.
septic (SEP-tick). A condition produced by bacteria when all oxygen supplies are depleted. If severe, bottom deposits and water turn black, give off foul odors, and the water has a greatly increased chlorine demand.
septic system. An onsite system designed to treat and dispose of domestic sewage; a typical septic system consists of a tank that receives wastes from a residence or business And a system of tile lines or a pit for disposal of the liquid effluent that remains after decomposition of the solids by bacteria in the tank.
sequestration (SEE-kwes-TRAY-shun). A chemical completing (forming or joining together) of metallic cations (such as iron) with certain inorganic compounds, such as phosphate. Sequestration prevents the precipitation of the metals (iron). Also see chelation.
service line sample. A one-liter sample of water collected 'm accordance with CFR Section 141.86(b)(6)of the code of Federal Regulations, that has been standing for a least 6 hours in a service line.
service pipe. The pipeline extending from the water main to the building served or to the consumers system.
set point. The position at which the control or controller is set. This is the same as the desired value of the process variable.
sewage. The used water and solids that flow from homes through sewers to a wastewater treatment plant. The preferred term is WASTEWATER.
sewage. Liquid and solid wastes carried in sewers.
sewer. An underground system of conduits (pipes and/or tunnels) that collect and transport wastewaters and/or runoff; gravity sewers carry free-flowing water and wastes; pressurized sewers carry pumped wastewaters under pressure.
sewerage system. The network of sewers that carries sewage from point of origin to point of treatment.
shock load. The arrival at a water treatment plant of raw water containing unusual amounts of algae, colloidal matter, color, suspended solids, turbidity, or other pollutants.
short-circuiting. A condition that occurs in tanks or basins when some of the water travels faster than the rest of the flowing water. This is usually undesirable since it may result in shorter contact, reaction, or settling times in comparison with the theoretical (calculated) or presumed detention times.
silt. Soil particles between 0.05 and 0.002 millimeter in approximate diameter.
simulate. To reproduce the action of some process, usually on a smaller scale.
single family structure. A building constructed as a singlefamily residence that is currently used as either a residence or a place of business.
single-stage pump. A pump that has only one impeller. A multi-stage pump has more than one impeller.
sink. A place in the environment where a compound or material collects. See reservoir.
slake. To mix with water with a true chemical combination (hydrolysis) taking place, such as in the slaking of lime.
slope. The slope or inclination of a trench bottom or a trench side wall is the ratio of the vertical distance to the horizontal distance or "rise over run." Also see grade (2).
slow sand filtration. A process involving passage of raw water through a bed of sand at low velocity (generally less than 0.4 m/h) resulting in substantial particulate removal by physical and biological mechanisms.
sludge (sluj). The settleable solids separated from water during processing.
slurry (SLUR-e). A watery mixture or suspension of insoluble (not dissolved) matter; a thin watery mud or any substance resembling it (such as a grit slurry or a lime slurry).
SMCLs. Secondary Maximum Contaminant Levels. Secondary MCLs for various water quality indicators are established to protect public welfare.
SNARL Suggested No Adverse Response Level. The concentration of a chemical in water that is expected not to cause an adverse health effect.
soft water. Water having a low concentration of calcium and magnesium ions. According to U.S. Geological Survey guidelines, soft water is water having a hardness of 60 milligrams per liter or less.
software programs. Computer programs; the list of instructions that tell a computer how to perform a given task or tasks.
soil erodibility. A measure of the soil's susceptibility to raindrop impact, runoff and other erosional processes.
soil profile. A vertical section of the earth's highly weathered upper surface often showing several distinct layers, or horizons.
soil structure. The arrangement of soil particles into aggregates.
soil texture. The proportions of soil particles (sand, silt, and clay) in a soil profile.
solder. A metallic compound used to seal the joints between pipes. Until recently, most solder contained 50 percent lead. The use of lead solder containing more than 0.2% lead is now prohibited for pipes carrying potable water.
sole source aquifer. An aquifer that supplies 50 percent or more of the drinking water of an area.
solenoid (SO-luh-noid). A magnetically (electrical coil) operated mechanical device. Solenoids can operate a small valve or a switch.
solution. A liquid mixture of dissolved substances. In a solution it is impossible to see all the separate parts.
sorption. A surface phenomenon which may be either absorption or adsorption, or a combination of the two; often used when the specific mechanism is not known.
span. The scale or range of values an instrument is designed to measure. Also see range.
specific conductance. A rapid method of estimating the dissolved-solids content of a water supply. The measurement indicates the capacity of a sample of water to carry an electrical current, which is related to the concentration of ionized substances in the water. Also called conductance.
specific gravity. Weight of a particle, substance, or chemical solution in relation to the weight of water. Water has a specific gravity of 1.000 at 4 degrees C (39 degrees F). Particulates in raw water may have a specific gravity of 1.005 to 2.5.
specific yield. The quantity of water that a unit volume of saturated permeable rock or soil will yield when drained by gravity. Specific yield may be expressed as a ratio or as a percentage by volume.
spoil Excavated material such as soil from the trench of a water main.
spore. The reproductive body of an organism which is capable of giving rise to a new organism either directly or indirectly. A viable (able to live and grow) body regarded as the resting stage of an organism. A spore is usually more resistant to disinfectants and heat than most organisms.
spring. Ground water seeping out of the earth where the water table intersects the ground surface.
spring line. Theoretical center of a pipeline. Also, the guideline for laying a course of bricks.
standard. A physical or chemical quantity whose value is known exactly, and is used to calibrate or standardize instruments. Also see reference.
Standard Method See Standard Methods for the Examination of Water and Wastewater.
Standard Methods for the Examination of Water and Wastewater. A joint publication of the American Public Health Association, American Water Works Association, and the Water Pollution Control Federation which outlines the procedures used to analyze the impurities in water and wastewater.
standard sample. The aliquot of finished drinking water that is examined for the presence of coliform bacteria.
standard solution. A solution in which the exact concentration of a chemical or compound is known.
standardize. To compare with a standard. 1) In wet chemistry, to find out the exact strength of a solution by comparing it with a standard of known strength. 2) To set up an instrument or device to read a standard. This allows you to adjust the instrument so that it reads accurately, or enables you to apply a correction factor to the readings.
starters. Devices used to start up large motors gradually to avoid severe mechanical shock to a driven machine and to prevent disturbance to the electrical lines (causing dimming and flickering of lights).
State. The agency of the State or Tribal government which has jurisdiction over public water systems. During any period when a State or Tribal government does not have primary enforcement responsibility pursuant to Section 1413 of the Safe Drinking Water Act, the term "State" means the Regional Administrator, U.S. Environmental Protection Agency.
static head. When water is not moving, the vertical distance (in feet) from a specific point to the water surface is the static head. (The static pressure in psi is the static head in feet times 0.433 psi/ft.) Also see dynamic pressure and static pressure
static pressure. When water is not moving, the vertical distance (in feet) from a specific point to the water surface is the static head. The static pressure in psi is the static head in feet times 0.433 psi/ft. Also see dynamic pressure and static head
static water depth. The vertical distance in feet from the centerline of the pump discharge down to the surface level of the free pool while no water is being drawn from the pool or water table.
static water level. 1) The elevation or level of the water table in a well when the pump is not operating. 2) The level or elevation to which water would rise in a tube connected to an artesian aquifer, or basin, or conduit under pressure.
stator. That portion of a machine which contains the stationary (non-moving) parts that surround the moving parts (rotor).
sterilization (STARE-uh-luh-ZAY-shun). The removal or destruction of all microorganisms, including pathogenic and other bacteria, vegetative forms and spores. Compare with disinfection.
stethoscope. An instrument used to magnify sounds and convey them to the ear.
strip cropping. A crop production system that involves planting alternating strips of row crops and close-growing forage crops; the forage strips intercept and slow runoff from the less protected row crop strips.
stochastic. Based on the assumption that the actions of a chemical substance results from probabilistic events.
storm sewer. A sewer that collects and transports surface runoff to a discharge point (infiltration basin, receiving stream, treatment plant).
stratification. The formation of separate layers (of temperature, plant, or animal life) in a lake or reservoir. Each layer has similar characteristics such as all water in the layer has the same temperature. Also see thermal stratification.
subchronic. Of intermediate duration, usually used to describe studies or levels of exposure between 5 and 90 days.
submergence. The distance between the water surface and the media surface in a filter.
submerged aquatic vegetation (SAV). Aquatic vegetation, such as sea grasses, that cannot withstand excessive drying and therefore live with their leaves at or below the water surface. SAVs provide an important habitat for young fish and other aquatic organisms.
suction lift The NEGATIVE pressure [in feet (meters) of water or inches (centimeters) of mercury vacuum] on the suction side of the pump. The pressure can be measured from the centerline of the pump DOWN TO (lift) the elevation of the hydraulic grade line on the suction side of the pump.
superchlorination (SUE-per-KLOR-uh-NAY-shun). Chlorination with doses that are deliberately selected to produce free or combined residuals so large as to require dechlorination .
Superfund. Federal law which authorizes EPA to manage the clean-up of abandoned or uncontrolled hazardous waste sites.
supernatant
(sue-per-NAY-tent). Liquid removed from settled sludge. Supernatant commonly refers to the liquid between the sludge on the bottom and the water surface of a basin or container.
supersaturated. An unstable condition of a solution (water) in which the solution contains a substance at a concentration greater than the saturation concentration for the substance.
supplier of water. Any person who owns or operates a public water system.
surface loading. One of the guidelines for the design of settling tanks and clarifiers in treatment plants. Used by operators to determine if tanks and clarifiers are hydraulically (flow) overor underloaded. Also called overflow rate.
surface pump. A mechanism for removing water or wastewater from a sump or wet well.
surface runoff. Precipitation, snow melt, or irrigation in excess of what can infiltrate the soil surface and be stored in small surface depressions; runoff is a major transporter of non-point source pollutants.
surface water. All water naturally open to the atmosphere (rivers, lakes. reservoirs, streams, impoundments, seas, estuaries, etc.) and all springs. wells, or other collectors which are directly influenced by surface water.
surfactant (
sir-FAC-tent). Abbreviation for surface-active agent. The active agent in detergents that possesses a high cleaning ability.
surge chamber. A chamber or tank connected to a pipe and located at or near a valve that may quickly open or close or a pump that may suddenly start or stop. When the flow of water in a pipe starts or stops quickly, the surge chamber allows water to flow into or out of the pipe and minimize any sudden positive or negative pressure waves or surges in the pipe.
suspended solids. I)Solids that either float on the surface or are suspended in water or other liquids, and which are largely removable by laboratory filtering. 2) The quantity of material removed from water in a laboratory test, as prescribed in STANDARD METHODS FOR THE EXAMINATION OF WATER AND WASTEWATER.
synergism. An interaction of two or more chemicals which results in an effect that is greater than the sum of their effects taken independently.
system with a single service connection. A system which supplies drinking water to consumers via a single service line.
systemic. Relating to whole body, rather than its individual parts.
systemic effects. Effects observed at sites distant from the entry point of a chemical due to its absorption and distribution into the body.
sounding tube. A pipe or tube used for measuring the depths of water.

T

TCE. See trichloroethane
TDS. See total dissolved solids. telemetry (tel-LEM-uh-tree). The electrical link between the transmitter and the receiver. Telephone lines are commonly used to serve as the electrical line.
temperature sensor. A device that opens and closes a switch in response to changes in the temperature. This device might be a metal contact, or a thermocouple that generates minute electrical current proportional to the difference in heat, or a variable resistor whose value changes in response to changes in temperature. Also called a heat sensor
teratogenesis. The induction of nonhereditary congenital malformations (birth defects) in a developing fetus by exogenous factors acting in the womb; interference with normal embryonic development.
teratogenicity. The capacity of a physical or chemical agent to cause teratogenesis in offspring.
terrace. A broad channel, bench, or embankment constructed across the slope to intercept runoff and detain or channel it to protected outlets, thereby reducing erosion from agricultural areas.
therapeutic index. The ratio of the dose required to produce toxic or lethal effect to dose required to produce nonadverse or therapeutic response.
thermal stratification (STRAT-uh-fuh-KAY-shun). The formation of layers of different temperatures in a lake or reservoir. Also see stratification
thermocline (THUR-moe-KLINE). The middle layer in a thermally stratified lake or reservoir. In this layer there is a rapid decrease in temperature with depth. Also called the METALIMNION.
thermocouple. A heat-sensing device made of two conductors of different metals joined at their ends. An electric current is produced when there is a difference in temperature between the ends.
THM See trihalomethanes
THM precursor. See precursor, THM.
threshold. The lowest dose of a chemical at which a specified measurable effect is observed and below which it is not observed.
threshold odor. The minimum odor of a water sample that can just be detected after successive dilutions with odorless water. Also called odor threshold
threshold odor number. The greatest dilution of a sample with odor-free water that still yields a just-detectable odor.
thrust block. A mass of concrete or similar material appropriately placed around a pipe to prevent movement when the pipe is carrying water. Usually placed at bends and valve structures.
tillage. Plowing, seedbed preparation, and cultivation practices.
time lag. The time required for processes and control systems to respond to a signal or to reach a desired level.
timer. A device for automatically starting or stopping a machine or other device at a given time.
time-weighted average. The average value of a parameter (e.g., concentration of a chemical in air) that varies over time.
tissue. A group of similar cells.
titrate (TIE-trate). To TITRATE a sample, a chemical solution of known strength is added on a drop-by-drop basis until a certain color change, precipitate, or pH change in the sample is observed (end point). Titration is the process of adding the chemical reagent in increments until completion of the reaction, as signaled by the end point.
TNCWS. See transient non-community water system.
too numerous to count. The total number of bacterial colonies exceeds 200 on a 47-nun diameter membrane filter used for coliform detection.
topography. The arrangement of hills and valleys in a geographic area.
total dissolved phosphorus. Total phosphorus content of material that will pass through a filter of a specific size.
total dissolved solids (TDS). All of the dissolved solids in a water. TDS is measured on a sample of water that has passed through a very fine mesh filter to remove suspended solids. The water passing through the filter is evaporated and the residue represents the dissolved solids. Also see specific conductance
total dynamic head (TDH). When a pump is lifting or pumping water, the vertical distance (in feet) from the elevation of the energy grade line on the suction side of the pump to the elevation of the energy grade line on the discharge side of the pump.
total nitrogen. The sum of all nitrogen forms.
total particulate phosphorus. Total phosphorus content of material retained on a filter of a specific size.
total phosphorus. The sum of all phosphorus forms.
total residual chlorine. The amount of available chlorine remaining after a given contact time. The sum of the combined available residual chlorine and the free available residual chlorine. Also see residual chlorine
total trihalomethanes (THMs). The sum of the concentration, in milligrams per liter, of the several trihalomethane compounds, rounded to two significant figures.
total trihalomethanes (TTHM). The sum of the concentration in milligrams per liter of the trihalomethane compounds (trichloromethane [chloroform], dibromochloromethane, bromodichloromethane and tribromomethane [bromoform]), rounded to two significant figures.
totalizer. A device or meter that continuously measures and calculates (adds) total flows in gallons, million gallons, cubic feet, or some other unit of volume measurement. Also called an integrator.
toxaphene (
TOX-uh-FEEN). A chemical that causes adverse health effects in domestic water supplies and also is toxic to freshwater and marine aquatic life.
toxic (TOX-ick). A substance which is poisonous to an organism.
toxic pollutants. Materials contaminating the environment that cause death, disease. birth defects in organisms that ingest or absorb them. The quantities and length of exposure necessary to cause these effects can vary widely.
toxic substance. A chemical or mixture that may represent an unreasonable risk of injury to health or the environment.
toxicant A harmful substance or agent that may injure an exposed organism.
toxicity. The quality or degree of being poisonous or harmful to plant, animal or human life.
toxicity assessment Characterization of the toxicological properties and effects of a chemical, including all aspects of its absorption, metabolism, excretion and mechanism of action, with special emphasis on establishment of doseresponse characteristics.
toxicology. The science and study of poisons control.
transducer (trans-DUE-sir). A device which senses some varying condition and converts it to an electrical signal for transmission to some other device (a receiver) for processing or decision making.
transformation. Acquisition by a cell of the property of uncontrolled growth.
TWS. See transient water system.
transient water system. A non-community water system that does not serve 25 of the same nonresident persons per day for more than six months per year. Also called a transient non-community water system (TNCWS).
transmission lines. Pipelines that transport raw water from its source to a water treatment plant. After treatment, water is usually pumped into pipelines (transmission lines) that are connected to a distribution grid system.
transmissivity. The ability of an aquifer to transmit water.
transpiration (TRAN-spur-RAY-shun).The process by which water vapor is released to the atmosphere by living plants.
treated wastewater. Wastewater that has been subjected to one or more physical, chemical, and biological processes to reduce its pollution of health hazard.
tremie (TREH-me). A device used to place concrete or grout under water.
trichloroethane (TCE) (try-KLOR-o-ETH-hane). An organic chemical used as a cleaning solvent that causes adverse health effects in domestic water supplies.
trihalomethane . One of a family of organic compounds named as derivatives of methane. THMs are generally the by-product from chlorination of drinking water that contains organic material. The resulting compounds (THMs) are suspected of causing cancer.
tube settler. A device that uses bundles of small bore (2 to 3 inches or 50 to 75 mm) tubes installed on an incline as an aid to sedimentation. The tubes may come in a variety of shapes including circular and rectangular. As water rises within the tubes, settling solids fall to the tube surface. As the sludge (from the settled solids) in the tube gains weight, it moves down the tubes and settles to the bottom of the basin for removal by conventional sludge collection means. Tube settlers are sometimes installed in sedimentation basins and clarifiers to improve particle removal.
tubercle (
TOO-burr-cull). A protective crust of corrosion products (rust) which builds up over a pit caused by the loss of metal due to corrosion.
tuberculation (too-BURR-que-LAY-shun). The development or formation of small mounds of corrosion products (rust) on the inside of iron pipe. These mounds (tubercules) increase the roughness of the inside of the pipe thus increasing resistance to water flow.
turbid. Having a cloudy or muddy appearance.
turbidimeter. A device that measures the amount of suspended solids in a liquid.
turbidity (ter-BID-it-tee). The cloudy appearance of water caused by the presence of suspended and colloidal matter. In the waterworks field, a turbidity measurement is used to indicate the clarity of water. Technically, turbidity is an optical property of the water based on the amount of light reflected by suspended particles. Turbidity cannot be directly equated to suspended solids because white particles reflect more light than dark-colored particles and many small particles will reflect more light than an equivalent large particle.

U

uncertainty factor. A number (equal to or greater than one) used to divide NOAEL or LOAEL values derived from measurements in animals or small groups of humans, in order to estimate a NOAEL value for the whole human population.
unconfined aquifer. An aquifer containing water that is not under pressure; the water level in a well is the same as the water table outside the well.
unit cancer risk. Estimate of the lifetime risk caused by each unit of exposure in the low exposure region.
unit hydrograph. The hydrograph of one inch of storm runoff generated by a rainstorm of fairly uniform intensity within a specific period of time.
unsaturated zone. The area between the land surface and water table in which the pore spaces are only partially filled with water. Also called "zone of aeration".
upper-bound estimate. Estimate not likely to be lower than the true risk.
urban runoff. Stormwater from city streets and adjacent domestic or commercial properties that may carry pollutants of various kinds into the sewer systems and/or receiving waters.
user fee. A fee which is collected only from those persons who use a particular service, as opposed to one collected from the public in general. User fees generally vary in proportion to the degree of use of the service.
UST'S. Underground storage tanks.

V

variable costs. Input costs that change as the nature of the production activity of its circumstances change; for example, as production levels vary.
variance. A State with primacy may relieve a public water system from a requirement respecting an MCL by granting a variance if certain conditions exist. These are: 1) the system cannot meet the MCL in spite of the application of best available treatment technology, treatment techniques or other means (taking costs into consideration), due to the characteristics of the raw water sources which are reasonably available to the system, and 2) the variance will not result in an unreasonable public health risk. A system may also be granted a variance from a specified treatment technique if it can show that, due to the nature of the system's raw water source, such treatment is not necessary to public health. Also see exemption.
vegetative controls. Non-point source pollution control practices that involve plants (vegetative cover) to reduce erosion and minimize the loss of pollutants.
virus. The smallest form of microorganisms capable of causing disease. Especially, a virus of fecal origin that is infectious to humans by waterborne transmission.
volatile. Readily vaporizable at a relatively low temperature.
volatile acids. Acids produced during digestion. Fatty acids which are soluble in water and can be steam-distilled at atmospheric pressure. Also called "organic acids." Volatile acids are commonly reported as equivalent to acetic acid.
volatile liquids. Liquids which easily vaporize or evaporate at room temperatures.
volatile solids. Those solids in water or other liquids that are lost on ignition of the dry solids at 550 degrees C.
volatilization. Loss of a substance through evaporation.
voltage. The electrical pressure available to cause a flow of current (amperage) when an electrical circuit is closed. See electromotive force (E.M.F.).
volumetric. A measurement based on the volume of some factor. Volumetric titration is a means of measuring unknown concentrations of water quality indicators in a sample by determining the volume of titrant or liquid reagent needed to complete particular reactions.
vortex. A revolving mass of water which forms a whirlpool. This whirlpool is caused by water flowing out of a small opening in the bottom of a basin or reservoir. A funnelshaped opening is created downward from the water surface.

W

wastewater. The used water and solids from a community (including used water from industrial processes) that flow to a treatment plant. Storm water, surface water, and groundwater infiltration also may be included in the wastewater that enters a wastewater treatment plant. The term -sewage usually refers to household wastes, but this word is being replaced by the term -wastewater.
wastewater treatment plant. A facility that receives wastewaters ( and sometimes runoff) from domestic and/or industrial sources, and by a combination of physical, chemical, and biological processes reduces (treats) the wastewaters to less harmful byproducts; known by the acronyms , STP (sewage treatment plant), and POTW (publicly owned treatment works).
waterborne disease outbreak. The significant occurrence of acute infectious illness, epidemiologically associated with the ingestion of water from a public water system that is deficient in treatment, as determined by the appropriate local or state agency
water budget. A summation of inputs, outputs, and net changes to a particular water resource system over a fixed period. (Also, water balance model).
water hammer. The sound like someone hammering on a pipe that occurs when a valve is opened or closed very rapidly. When a valve position is changed quickly, the water pressure in a pipe will increase and decrease back and forth very quickly. This rise and fall in pressures can do serious damage to the system.
water purveyor (purr-VAY-or). An agency or person that supplies water (usually potable water).
water solubility. The maximum concentration of a chemical compound which can result when it is dissolved in water. If a substance is water soluble, it can very readily disperse through the environment.
water storage pond. An impound for liquid wastes, so designated as to accomplish some degree of biochemical treatment of the wastes.
water supplier. A person who owns or operates a public water system.
water supply system. The collection, treatment, storage, and. distribution of potable water from source to consumer.
water table. The level of ground water. The upper surface of the zone of saturation of groundwater above an impermeable layer of soil or rock (through which water cannot move) as in an unconfined aquifer. This level can be very near the surface of the ground or far below it.
water treatment lagoon. An impound for liquid wastes, so designed as to accomplish some degree of biochemical treatment of the wastes.
water well. An excavation where the intended use is for the location, acquisition, development, or artificial recharge of groundwater (excluding Sandpoint wells).
watershed. The land area that drains into a stream. An area of land that contributes runoff to one specific delivery point; large watersheds may be composed of several smaller "subsheds", each of which contributes runoff to different locations that ultimately combine at a common delivery point.
watt A unit of power equal to one joule per second. The power of a current of one ampere flowing across a potential difference of one volt.
weir (weer). 1) A wall or plate placed in an open channel and used to measure the flow of water. The depth of the flow over the weir can be used to calculate the flow rate, or a chart or conversion table may be used. 2) A wall or obstruction used to control flow (from settling tanks and clarifiers) to assure uniform flow rate and avoid short-circuiting.
weir diameter (weer). Many circular clarifiers have a circular weir within the outside edge of the clarifier. All the water leaving the clarifier flows over this weir. The diameter of the weir is the length of a line from one edge of a weir to the opposite edge and passing through the center of the circle formed by the weir
weir loading. A guideline used to determine the length of weir needed on settling tanks and clarifiers in treatment plants. Used by operators to determine if weirs are hydraulically (flow) overloaded. Weir Loading (GPM/ft) = Flow (GPM)/ Length of Weir (ft)
well. A bored, drilled, or driven shaft, or a dug hole, whose depth is greater than the largest surface dimension and whose purpose is to reach underground water supplies or oil, or to store or bury fluids below ground.
well field. Area containing one or more wells that produces usable amount of water.
well monitoring. The measurement, by on-site instruments or laboratory methods, of the quality of water in a well.
well plug. A watertight and gastight seal installed in a bore hole or well to prevent movement of fluids.
wet chemistry. Laboratory procedures used to analyze a sample of water using liquid chemical solutions (wet) instead of, or in addition to, laboratory instruments.
wetlands. Any number of tidal and nontidal areas characterized by saturated or nearly saturated soils most of the year that form an interface between terrestrial (land-based) and aquatic environments; include freshwater marshes around ponds and channels (rivers and streams), brackish and salt marshes; other common names include swamps and bogs.
wire-to-water efficiency. The efficiency of a pump and motor together. Also called the overall efficiency.
withdrawal The process of taking water from a source and conveying it to a place for a particular type of use.

Y

yield. The quantity of water (expressed as a rate of flowGPM, GPH, GPD, or total quantity per year) that can be collected for a given use from surface or groundwater sources. The yield may vary with the use proposed, with the plan of development, and also with economic considerations. Also see safe yield.

Z

zeta potential. In coagulation and flocculation procedures, the difference in the electrical charge between the dense layer of ions surrounding the particle and the charge of the bulk of the suspended fluid surrounding this particle. The zeta potential is usually measured in millivolts.
zone of aeration. The comparatively dry soil or rock located between the ground surface and the top of the water table.
zone of saturation. The soil or rock located below the top of the groundwater table. By definition, the zone of saturation is saturated with water. Also see water table.
zooplankton (ZOE-PLANK-ton). Small, usually microscopic animals(such as protozoans), found in lakes and reservoirs.

References

Water Treatment Plant Operation. California State University, Sacramento, School of Engineering, Applied Research and Design Center. 1988. Surface Water Treatment: The New Rules. Harry von Huben. American Water Works Association. 1991. Safe Drinking Water Act Amendments, Regulations and Standards. Calabrese, EJ; Gilbert, CE and Pastides, H. Eds. Lewis Publishers. Chelsea Michigan. 1988. Water Resources Planning. Dzurik, AA. Rowman & Littlefield, Savage, MD. 1990. Code of Federal Regulations, Title 40, Chapter I, Section 141.2.July 1, 1991 Federal Register 56 FR 26547, June 7, 1991 (Lead and Copper) 56 FR 3578, January 30, 1991 (Phase 11)

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