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Water Quality

Glossary of Water Quality Terms



M

Mainstem
      The main course of a river or stream where most of the water flows most of the time.

Marine
      Refers to the ocean or to a sea, saltwater.

Marsh
      A wetland that is usually submerged in shallow water and whose vegetation is dominated by

      herbs.

Maximum contaminant level, MCL
      The greatest amount of a contaminant that can be present in water without causing a risk to its       intended use, the maximum level of a contaminant allowed in water to maintain aquatic life, to       minimize pollution, to permit recreation or allow the water to be used as a drinking water       source, (see contact recreation, non-contact recreation).

MCL, Maximum contaminant level
      The greatest amount of a contaminant that can be present in water without causing a risk to its       intended use, the maximum level of a contaminant allowed in water to maintain aquatic life, to       minimize pollution, to permit recreation or allow the water to be used as a drinking water       source, (see contact recreation, non-contact recreation).

Meiosis
      The process of cell division which separates the pair of complementary chromosomes to
      produce eggs and sperm with only one set of chromosomes each.

Metalloid
      Resembling a metal, or having chemical properties similar to metals.

Methylation
      The process whereby a compound is modified chemically, often through bacterial action, by the       replacement of a hydrogen atom by a methyl group, -CH3.

Mg/L, Milligrams per litre
      A concentration unit of chemical constituents in solution, the weight of solute per unit volume
      of solvent, usually water, this measure is equivalent to parts per million or ppm.

Micrograms per litre, µ/L
      A  concentration unit of chemical constituents in solution; the weight of solute per unit volume       of solvent, usually water, one thousand micrograms per liter is equivalent to 1 milligram per       litre, this measure is equivalent to parts per billion or ppb.

Micron, µ
      A quantitative measure of thickness equal to one millionth of a meter, one thousandth of a       millimeter, one ppm.

Milligrams per litre, Mg/L
      A concentration unit of chemical constituents in solution, the weight of solute per unit volume
      of solvent, usually water, this measure is equivalent to parts per million or ppm.

Mitochondria
      
The organelles in eukaryotic cells that carry out terminal respiration, specialized structures       that carry out respiration and store energy.

Mollusca
      An organism in the invertebrate Phylum Mollusca, a major group of marine, aquatic and
      terrestrial animals which are soft bodied and usually have a hard shell, examples are clams,
      mussels, snails, octopus and squid.

Monitoring
     To check, measure or examine water quality over a period of time to note any changes which
      may occur.

Most Probable Number, MPN
      The statistically determined number that represents the number of individual bacteria most likely       to have been present in a given sample, measurement of fecal coliform indicator bacteria       based on gas production in tubes, alternative to the standard fecal coliform test involving       filtration and culture on disk media.

MPN, Most Probable Number
      The statistically determined number that represents the number of individual bacteria most likely       to have been present in a given sample, measurement of fecal coliform indicator bacteria             based on gas production in tubes, alternative to the standard fecal coliform test involving       filtration and culture on disk media.

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

Muscle
      Tissue consisting of cells which are highly contractile, most of the edible portions of animal flesh
      is muscle.

Muskeg
      A wetland or peatland such as a fen or bog that accumulates peat and whose vegetation is
      dominated by sphagnum moss and small shrubs or herbs.


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N

Nekton
      Aquatic animals in the water column with sufficient powers of locomotion to overcome currents       and go where they want under their own power as opposed to the plankton which, although       some are motile, are at the mercy of water currents, fish are examples of the nekton.

Nephelometric turbidity unit, NTU
      The unit of measure for the turbidity of water, a measure of the cloudiness of water as measured       by a nephelometer, based on the amount of light that is reflected off particles in the water.

Non-consumptive use
      Using water in a way that does not reduce the immediate supply such as hunting, fishing,       boating, water-skiing, swimming and some power production, (see consumptive use).

Non-contact 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,       (see contact recreation).

Non-filterable residue
      Solids that are not in true solution and that can be removed by filtration they usually contribute       directly to turbidity, small particles of solid pollutants that resist separation by conventional       methods; operationally greater than 0.45 microns in size; also known as suspended solids,       suspended matter or suspended sediment.

Non-point Source Pollution, NPS
      Constituents in water, including pollutants, originating from diffuse, land-based sources and       generally transported in runoff from precipitation, pollution discharged over a wide land area,       not from one specific location, diffuse pollution caused by sediment, nutrients, organic and       toxic substances originating from land-use activities, which are carried to lakes and streams by       surface runoff, contamination that occurs when rainwater, snowmelt or irrigation washes off       plowed fields, city streets or suburban backyards. As this runoff moves across the land surface,       it picks up soil particles and pollutants, such as nutrients and pesticides, 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, (see point source pollution).

Non-porous
      A material which does not allow water to pass through it, (see porous).

Non-potable
      Not suitable for drinking due to toxins, pathogens or aesthetics, (see potable).

NTU, Nephelometric turbidity unit
      The unit of measure for the turbidity of water, a measure of the cloudiness of water as measured       by a nephelometer, based on the amount of light that is reflected off particles in the water.

Nutrient
      A substance, element or compound, necessary for the growth, development and reproduction of       plants and animals, as a pollutant any element or compound, such as phosphorous or nitrogen       that encourages abnormally high organic growth in ecosystems, (see eutrophic).

Nutrient cycle
      Chemical transformations of nitrogen, phosphorus, silica and other essential elements in       continuous cycles between organic and living systems and inorganic and non-living phases in       an ecosystem as organisms grow and die.


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O

Ocean
      The large, permanent body of saline water surrounding the continents and covering most of  the
      surface of the earth.

Oligochaetes
      Primarily fresh water or terrestrial hermaphroditic annelid worms that lack a distinctive head       segment, (see worms, polychaetes).

Oligotrophic
      Having a low supply of nutrients and thus a low productivity or biomass, (see eutrophic).

Organelles
      The structures in eukaryotic cells, notably chloroplasts and mitochondria, specialized       structures that carry out respiration, photosynthesis and other functions in the cell.

Organic chemicals or compounds
      Usually chemicals or compounds which contain carbon atoms; usually chains of carbon atoms       connected directly to each other, chemicals containing carbon, organic matter, plant and animal       residues, or substances made by living organisms.

Organic contaminants
      Organic chemicals which are toxic to organisms; they may be persistent and mobile in the
      environment.

Osmosis
      The movement of water molecules through a thin membrane while leaving the dissolved salts       behind, the process occurs in our bodies and is also a technical and commercial method of       removing salts from saline water.

Outfall
      The end of the pipe leading from a sewage treatment plant which delivers the wastewater to the       environment, often via a diffuser, the discharge point for a wastewater flow, for example from       a sewage treatment plant or refinery, the place where a wastewater treatment plant       discharges treated water into the environment, the place where a sewer, drain, or stream       discharges, the outlet or structure through which reclaimed water or treated effluent is finally       discharged to a receiving water body.

Oviparous
      Fish and other organisms that produce eggs which hatch externally, fertilization may be
      internal or external, the fertilized eggs are self-contained and receive no nutrients from the
      mother.

Ovoviviparous
      Fish and other organisms that produce eggs which hatch internally, fertilization is internal, the
      fertilized eggs are self-contained and receive no further nutrients from the mother.

Oxidation
      Literally — combining with oxygen, chemically — transfer of electrons in a chemical reaction.

Oxygen demand
      The need for molecular oxygen to meet the needs of biological and chemical processes in water,       even though very little oxygen will dissolve in water, it is extremely important in biological and       chemical processes, (see BOD, biochemical oxygen demand).


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P

PAHs, Polycyclic aromatic hydrocarbons
      A family of organic compounds with several linked aromatic rings in their structure which are       derived from the combustion of fossil fuels, the higher molecular weight PAHs are an       environmental concern due to their bioaccumulation in organisms and their toxic and       carcinogenic activity.

Palustrine
      Relating to a freshwater environment, such as a marsh, fen, lake, pond, river, bog or       swamp.

Parasite, parasitic
      Organisms that are pathogens and are obliged to live on or in other organisms, often causing
      disease or death.

Particulate
      Consisting of many small individual particles, not dissolved.

Pathogen
      An organism, generally a microorganism, causing, or capable of causing, disease or death, a       disease-producing agent, usually applied to a living organism, any worms, protozoans, viruses,       bacteria or fungi that cause disease.

Pathogenic
      Causing, or capable of causing, disease or death, generally applied to microorganisms.

PCBs, Polychlorinated biphenyls
      Man-made liquid chemicals that are stable, non-corroding, fire resistant, toxic and relatively
      non-biodegradable, once used in electrical transformers because of these properties and in paint,       composed of two joined phenol molecules that have chlorine atoms replacing many of the       hydrogen atoms, frequently found in industrial wastes, and subsequently in surface water and       ground waters, accumulate in the environment, particularly in the sediment where they can       remain indefinitely, virtually banned in 1979 but continuing to appear in the flesh of fish and other       animals.

Peak flow
      The maximum instantaneous discharge of a stream or river at a given location, usually occurs
      at or near the time of maximum height.

Peatland
      A wetland such as a fen or bog that accumulates peat and whose vegetation is dominated by
      sphagnum moss and small herbs.

Pelecypoda
      Bivalves, class of aquatic molluscs with two shells.

Percolation
      The movement of water through the subsurface soil layers, usually continuing downward to the
      ground water or water table, the oozing or soaking of water through the soil, the movement of       water through the openings in rock or soil, the entrance of a portion of the streamflow into the       channel materials to contribute to ground water replenishment.

Periphyton
      Organisms attached to and growing on structures, sediments or organisms submerged in water.

Permeability
      The ability of a water bearing material to transmit water, measured by the quantity of water       passing through a unit cross section, in a unit time, the ability of a material to allow the passage       of a liquid, such as water through rocks, materials, such as gravel and sand, allow water to move       quickly through them, whereas impermeable materials, such as clay, do not allow water to       flow freely.

pH
     The numeric value which is the negative reciprocal of the logarithm, in base 10, of the hydrogen       ion concentration in moles per litre, a quantitative expression for the amount of acidity or       alkalinity of a solution, the scale ranges from 0 to 14, where pH 7 is neutral, less than 7 is       acid, more than 7 is alkaline or basic, numeric value that describes the intensity of the acid or       basic, alkaline, conditions of a solution.

Phenol
      A benzene ring with one of the hydrogens replaced by a hydroxyl or -OH group.

Photic zone
      The upper portion of the water column which admits sufficient light for photosynthesis, the       photic zone is reduced with increased turbidity.

Photosynthesis
     The process by which the chlorophyll-bearing cells of green plants, in the presence of light,       convert carbon dioxide and water into sugar, an organic compound, with the evolution of       oxygen, incorporation of solar energy into carbon compounds by green plants, ultimately       providing energy and oxygen for the vast majority of life on earth.

Phytoplankton
      The photosynthetic portion, primarily algae, of the free-floating community of small, mostly       microscopic, organisms in water, collectively called plankton.

Plankton
      The total free-floating community of small, mostly microscopic, organisms in water, some are
      motile but all are at the mercy of water currents, (see nekton).

Planktonic
      Drifting unattached in water, the plankton include both plants and animals ranging from
      microscopic to macroscopic.

Plume
      A portion of a water body which is distinguishable from the remainder because it is not       completely mixed and its characteristics are measurably different, generally downstream from       the junction of another stream of water from a tributary or waste discharge, the area taken up       by contaminants in an aquifer.

Poikilothermic
      Animals which do not automatically control their own body temperature at some fixed value,
      cold-blooded animals, their body temperature is controlled by ambient conditions or by       behaviour, (see homeothermic).

Point source pollution
      Source of pollution that involves discharge of wastes from an identifiable point, such as a       smokestack or sewage treatment plant, water pollution coming from a single point, such as a       sewage outflow pipe, (see non-point source pollution).

Pollutant
      Waste material which causes harm to organisms directly or to their environment.

Pollution
      Causing the release of a pollutant into the environment, harmful or undesirable changes in the       physical, chemical, or biological characteristics of the air, water or land that may affect the       health, survival or activities of human or other living organisms, degradation of the environment by       a substance or condition to such a degree that the environment fails to meet specified standards       or cannot be used for a specific purpose.

Polychaetes
      Primarily marine annelid worms with paired segmental appendages, separate sexes and       free-swimming trochophore larvae, worms of the Class Polychaeta of the invertebrate       worm order Annelida, dominant in marine benthos, highly diversified, ranging from detritivores       to predators, some species serving as good indicators of environmental stress, (see       oligochaetes).

Polychlorinated biphenyls, PCBs
      Man-made liquid chemicals that are stable, non-corroding, fire resistant, toxic and relatively
      non-biodegradable, once used in electrical transformers because of these properties and in paint,       composed of two joined phenol molecules that have chlorine atoms replacing many of the       hydrogen atoms, frequently found in industrial wastes, and subsequently in surface water and       ground waters, accumulate in the environment, particularly in the sediment where they can       remain indefinitely, virtually banned in 1979 but continuing to appear in the flesh of fish and other       animals.

Polycyclic aromatic hydrocarbons, PAHs
      A family of organic compounds with several linked aromatic rings in their structure which are       derived from the combustion of fossil fuels, the higher molecular weight PAHs are an       environmental concern due to their bioaccumulation in organisms and their toxic and       carcinogenic activity.

Pond
      A relatively small, sometimes ephemeral or seasonal, inland body of fresh water occupying a
      basin or hollow in the earth's surface.

Pore water
      The water found in the interstices of submerged sediments, the basis of some types of toxicity
      testing, since it is pore water to which benthic organisms are exposed.

Porosity
      A measure of the water-bearing capacity of subsurface rock, with respect to water movement, it       is not just the total magnitude of porosity that is important, but the size of the voids and the       extent to which they are interconnected, as the pores in a formation may be open and       interconnected, or closed and isolated, clay may have a very high porosity with respect to       potential water content, but it constitutes a poor flow medium as an aquifer because the pores       are usually so small.

Porous
      A material which allows water to pass through it, (see nonporous).

Potable
      Water that is toxicologically and pathologically safe and aesthetically fit to drink, (see
      non-potable).

ppb
      A concentration unit of chemical constituents in solution; the weight of solute per unit volume       of solvent, usually water, one thousand micrograms per liter is equivalent to 1 milligram per       litre, this measure is equivalent to parts per billion.

ppm
      A concentration unit of chemical constituents in solution; the weight of solute per unit volume       of solvent, usually water, one thousand milligrams per liter is equivalent to 1 gram per       litre, this measure is equivalent to parts per million.

ppt
      A concentration unit of chemical constituents in solution; the weight of solute per unit volume       of solvent, usually applied to marine, brackish or saline water, this measure is equivalent to       parts per thousand.

Precipitate
      A solid or particles which have come out of an aqueous, or other fluid, solution.

Precipitation
      Water, normally in the form or rain, snow and hail, which falls from the atmosphere to the earth       as part of the water cycle, the process whereby solids or particle come out of solution.

Precision
      This is an indicator of how close a series of measured values come to each other, how tight is       the cluster of values, regardless of whether or not the values are accurate or reflect the actual or       true value, (see accuracy).

Primary sewage treatment
      The first stage of the wastewater treatment process consisting of mechanical removal of large       settleable solids through filtering, screening and/or settling, primary sewage treatment is a       mechanical treatment in which relatively large solids are removed from the sewage by settling       out as sludge, mechanical methods, such as filters and scrapers, are used to remove       pollutants, solid material in sewage also settles out in this process, (see secondary sewage       treatment, tertiary sewage treatment).

Primary wastewater treatment
      The first stage of the wastewater treatment process consisting of mechanical removal of large       settleable solids through filtering, screening and/or settling, primary wastewater treatment       is a mechanical treatment in which relatively large solids are removed from the sewage by       settling out as sludge, mechanical methods, such as filters and scrapers, are used to remove       pollutants, solid material in sewage also settles out in this process, (see secondary sewage       treatment, tertiary sewage treatment).

Pristine
      Describes a natural system, water for example, that has not been affected by anthropogenic
      pollution
.

Productivity
      The total amount of biological material produced over a defined time period, (see biomass,
      standing crop).

Profundal zone
      The deep-water region of a lake that is not penetrated by sunlight.

Prokaryotic
      Unicellular organisms with a bacteria-like cell structure, lacking a nucleus and some other       eukaryotic organelles, they may have photosynthetic pigments but lack chloroplasts, the       specialized photosynthetic organelles in higher plants, and mitochondria, (see eukaryotic).

Protozoan
      Single-celled, nucleated, eukaryotic organisms, lacking cell walls, generally microscopic, some
      are photosynthetic.


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Q

Qualitative
      Refers to what, which chemical or compound or identity regardless of how much, (see
      quantitative).

Quantitative
      Refers to a measured value as how much, how fast, how deep, how many or what
      concentration
, (see qualitative).


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R

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

Recharge
      Water entering an underground aquifer through faults, fractures or direct absorption,
      replenishing an aquifer.

Reclaimed wastewater
      Treated wastewater that can be used for beneficial purposes, such as irrigating certain plants,
      domestic wastewater which has been treated to a quality suitable for a beneficial use.

Recycled
      Using water or other materials more than once before returning it to the natural environment,
      wastes that are used for a beneficial purpose or made into new product rather than being
      landfilled or burned.

Recycled water
      Water that is used more than once before it returns to the natural hydrologic system.

Red tide
      Algal bloom involving dinoflagellate phytoplankton species, such as Gonyaulax monilata and       Ptychodiscus brevis, which naturally manufacture biotoxins, can cause fish kills and several       types of shellfish poisoning in people.

Reservoir
      A natural or artificial basin for collecting and holding a supply of water, tanks, dammed areas,
      lakes or underground aquifers, where water is collected and used for water storage, regulation
      and control, large bodies of ground water are called ground water reservoirs, water behind a
      dam is called a surface reservoir.

Residence time
      The period of time water is retained in a reservoir, bay or other system, based upon flow rates
      into and out of the system, (see flushing).

Residual chlorine
      The unreacted chlorine which remains in solution after the reactions with all the organic
      compounds present have occurred.

Return flow
      That part of a diverted flow that is not consumptively used and is returned to its original source       or to another body of water, drainage water from irrigated farmlands that re-enters the water       system to be used further downstream, irrigation water that is applied to an area and which is       not consumed in evaporation or transpiration and returns to a surface stream or aquifer.

Reverse osmosis, RO
      A water treatment method whereby water is forced through a semi-permeable membrane       which filters out impurities, similar in function to a kidney dialysis machine and used in most       space programs and navy vessels to turn waste water into potable water, removing salts from       water using a membrane, the product water passes through a fine membrane that the salts are       unable to pass through, while the salt waste, brine is removed, method of water or wastewater       treatment that relies on a semi-permeable membrane to separate waters from pollutants, an       external force is used to reverse the normal osmotic process resulting in the solvent moving from       a solution of higher concentration to one of lower concentration.

Riparian zone
      A stream and all the vegetation on its banks out to the high water mark, associated with the
      bank of a watercourse, the woodlands bordering a river.

River
      A relatively large and usually permanent flowing body of fresh water, in a defined channel.

Runoff
      Surface flows of water entering rivers, lakes, the ocean or reservoirs, surface water entering       rivers, fresh water lakes, or reservoirs, the portion of precipitation that is not absorbed into       the soil, but flows into surface streams, that part of the precipitation or irrigation water that       appears in uncontrolled surface streams, rivers, drains or sewers, direct runoff or base runoff,       storm interflow or ground water runoff, total discharge during a specified period of time, the       depth to which a drainage area would be covered if all of the runoff for a given period of time       were uniformly distributed over it.


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S

Saline
      Waters having solute concentrations approaching or exceeding that of seawater, slightly       saline water — from 1,000 ppm to 3,000 ppm, moderately saline water — from 3,000 ppm to       10,000 ppm, highly saline water — from 10,000 ppm to 35,000 ppm, water containing more       than 1,000 parts per million of dissolved solids of any type, water that contains significant       amounts of dissolved solids, water containing dissolved salts, such as the ocean, (see brine,       fresh water).

Salinity
      A quantitative measure of the solute concentration dissolved in water, usually measured as       parts per thousand or ppt, amount of dissolved salts in a given volume of water, salt       concentration in marine waters, ranging from zero to about 33 parts per thousand, ppt, in       estuaries, does not have a precise chemical definition, since the proportions of various ions vary       in the different waters of the world.

Salmonid
      Fish of the family Salmonidae which includes trout, salmon and char.

Salt
      The product formed when an acid and a base react.

Saltwater
      The water in the ocean or a sea which has high salinity.

Sample
      A small portion of water or other substance taken at a given place and time for analysis; it is       assumed to be representative of the whole body of water or the rest of the substance within       specified statistical limits (see grab sample, composite sample).

Sanitary sewer
      A system of pipes, conduits and pumps used to convey sewage from its source generally to a       treatment plant but also to a ground disposal site, the ocean, irrigation site, holding lagoon or       a stream, conveys domestic and institutional sewage and blackwater and industrial       wastewater, as opposed to stormwater.

Saprophyte, saprophytic
      Organisms that do not manufacture their own food and use the organic matter of dead, decaying
      or decayed other organisms as a source of nutrients for growth.

Saturation
      A measure of the proportion of the maximum amount of a gas, or solid, that can be dissolved in
      a liquid, usually water, at the specified temperature and pressure, alternatively a measure of the
      maximum amount of water, or other liquid, that can be absorbed or held in a porous medium,
      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.

Screening
      Passing sewage or wastewater through a coarse mesh to remove the larger particles, (see
      filtration).

Sea
      The large, permanent body of salt water surrounding the continents and covering most of the
      surface of the earth or one of the smaller landlocked or nearly isolated bodies of salt water.

Secchi disc
      An opaque, black and white disk lowered into water until the demarcation between the black and
      white portions is no longer visible, this secchi depth is a practical, traditional measurement of
      water clarity, and is correlated with turbidity and the depth of the biological photic zone.

Secondary sewage treatment
      Includes primary sewage treatment and provides in addition conditions conducive to the       biological oxidation of the remaining organic wastes, the 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, involving the biological process of reducing suspended, colloidal and       dissolved organic matter in effluent from primary sewage treatment systems and generally       removing 80 to 95 percent of the Biochemical oxygen demand, BOD, and suspended       matter, accomplished by biological or chemical-physical methods, removes floating and       settleable solids and about 90 percent of the suspended solids, disinfection is the final stage       of secondary treatment, (see primary sewage treatment, tertiary sewage treatment).

Secondary wastewater treatment
      Includes primary sewage treatment and provides in addition conditions conducive to the       biological oxidation of the remaining organic wastes, the 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, involving the biological process of reducing suspended, colloidal and       dissolved organic matter in effluent from primary sewage treatment systems and generally       removing 80 to 95 percent of the Biochemical oxygen demand, BOD, and suspended       matter, accomplished by biological or chemical-physical methods, removes floating and       settleable solids and about 90 percent of the suspended solids, disinfection is the final stage       of secondary treatment, (see tertiary sewage treatment).

Sediment
      Undissolved soil particles, sand and minerals washed from the land into aquatic systems as a
      result of natural and human activities, usually applied to material in suspension in water or
      recently deposited from suspension, all kinds of deposits from the waters of streams, lakes or
      seas.

Sedimentation
      A large scale water treatment  process where heavy solids settle to the bottom of the
      treatment tank by gravity after flocculation, the process by which solids suspended in water
      are allowed to settle to the bottom of a basin or container.

Sedimentation tanks
      Wastewater tanks in which floating wastes are skimmed off and settled solids are removed for
      disposal.

Seepage
      The slow movement of water through small cracks, pores and interstices of a material, into or       out of a body of surface or subsurface water, the loss of water by infiltration into the soil from a       canal, ditch, lateral, watercourse, reservoir, storage facility or other body of water, or from a       field.

Separate sewer
      A sewer system that carries only sanitary sewage or stormwater runoff, when sewers are       constructed this way, wastewater sewage treatment plants do not have to be sized to handle       stormwater flows avoiding overflows of untreated sewage, (see combined sewer).

Settleable solids
      Suspended solids that will settle when the sewage, wastewater or any other water containing
      suspended material, is held static for a period of time, usually about two hours for sewage
      treatment.

Settling
      Allowing sewage or wastewater to sit in a holding basin for a period of time while the larger and       heavier particles settle to the bottom before the liquid with its solutes and some smaller       particulates is sent for further treatment or directly to the environment.

Sewage
      Primarily feces, kitchen waste and wash water but usually with other organic and inorganic
      materials present.

Sewage treatment
      The complete sewage treatment process typically involves a three-phase process, in the       primary sewage treatment process, which incorporates physical aspects, untreated water is       passed through a series of screens to remove solid wastes, in the secondary sewage       treatment process, typically involving biological and chemical processes, screened sewage is       then passed a series of holding and aeration tanks and ponds, the tertiary sewage treatment       process consists of flocculation basins, clarifiers, filters and chlorine basins or ozone or       ultraviolet radiation processes.

Sewage treatment plant
      A facility designed to receive the wastewater from domestic sources and to remove materials       that damage water quality and threaten public health and safety when discharged into receiving       streams or bodies of water, removes greases and fats, solids from human waste and other       sources, dissolved pollutants from human waste and decomposition products, and dangerous       microorganisms, facilities employ a combination of mechanical removal steps and bacterial       decomposition to achieve these results, chlorine is often added to discharge from the plants to       reduce the danger of spreading disease by the release of pathogenic bacteria.

Sewer
      A system of pipes, conduits and pumps used to convey sewage from its source generally to a
      treatment plant but also to a ground disposal site, the ocean, irrigation site, holding lagoon or
      a stream.

Side channel
      A slow moving body of water usually with two ends open to the main water body.

Site specific
      Limited to the particular site or location under discussion.

Siltation
      The accumulation of sediments transported by water, the deposition of finely divided soil and
      rock particles on the bottom of stream and river beds and lakes and reservoirs.

Slough
      A slow moving body of water usually with one end open to the main water body.

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.

Solute
      Any solid material that is dissolved in a liquid which is the solvent.

Solution
     The mixture of dissolved material, the solute and the liquid solvent.

Solvent
      The liquid, usually water, in which solutes are dissolved, a substance that dissolves other
      substances, thus forming a solution.

Sorbed
      A general term for the results of the process of absorption and adsorption, often used to       denote that either or both have occurred.

Sorption
      A general term for the process of absorption and adsorption, often used to denote the
      occurrence of both.

Spatial
      Of or relating to space.

Spawning
      Term used to denote the process where fish, and other water dwelling organisms, deposit and
      fertilize eggs during reproduction.

Specific conductance
      A quantitative measure of the ability of a water to conduct an electrical current, related to the       type and concentration of ions in solution and can be used for approximating the total       dissolved solids concentration in water, one can monitor electrical conductivity quickly in the       field and estimate total dissolved solids or TDS without doing any lab tests at all using       hand-held testers, expressed in units of electrical conductance, Siemens per centimeter at 25       degrees Celsius, used in ground water monitoring as an indicator of the presence of ions of       chemical substances that may have been released by a leaking landfill or other waste storage or       disposal facility.

Specific gravity
     The density of a material related to that of water whose specific gravity is defined as one.

Sperm
      A small motile gamete produced by the male organism which contains one haploid set of
      chromosomes and swims to the egg to bring about fertilization.

Standing crop
      The total amount of biological material present at any given time, (see productivity, biomass).

Stomata
      The small pores in the epidermis of plants, usually in the leaves, through which atmospheric gas
      and water exchange takes place and is controlled.

Storm drain
      A drainage system designed for stormwater which is surface runoff from streets and other       impervious surfaces associated with urbanization or other anthropogenic activities and distinct       from the sewage system, a sewer that carries only surface runoff, street wash and snow melt       from the land, storm drains are completely separate from those that carry domestic and       commercial wastewater, (see sanitary sewers).

Storm sewer
      A drainage system designed for stormwater which is surface runoff from streets and other      impervious surfaces associated with urbanization or other anthropogenic activities and distinct       from the sewage system, a sewer that carries only surface runoff, street wash and snow melt       from the land, storm sewers are completely separate from those that carry domestic and       commercial wastewater, (see sanitary sewers).

Stormwater
      Water which is primarily surface runoff from streets and other impervious surfaces associated
      with urbanization or other anthropogenic activities.

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

Stratification
      Vertical separation of water masses into layers with different characteristics, dense salt water       intruding under fresh water in a navigation channel can establish salinity stratification,       temperature differences in fresh water can form distinct water layers separated by density, (see       epilimnion, thermocline, hypolimniuon, specific gravity).

Stream
      A relatively small and sometime ephemeral or seasonal flowing body of fresh water, in a
      defined channel.

Stream improvement
      One or more works, situated in or near a stream, relating to diversion, storing, measuring,
      conserving, conveying, retarding, confining or using water from the stream.

Sublethal
      Involves an effect that does not cause death of the organism.

Sublimation
      The change of state from a solid directly to a gas, (see evaporation, condensation,
      vapourization, transpiration).

Supersaturation
      A concentration of a gas in water above the equilibrium concentration, this occurs when the
      gas enters solution more quickly than it can be released from the liquid to gas phase as in
      extremely high rates of plankton photosynthesis or in the tail races of dams and under
      waterfalls where air is entrained.

Surface microlayer
      The immediate surface of the water only microns thick, important as the interface for
      atmosphere and water equilibrium processes, the location of highest concentration of
      hydrophobic pollutants like oil, and the location of floating marine eggs and other biological
      larval forms.

Surface water
      Water that flows in streams and rivers and in natural lake and ponds, in wetlands and in       reservoirs constructed by humans but on the surface of the land and not underground, water on       the surface on the earth, as distinguished from ground water.

Survey
      A general overview study of a problem or area, not too specific or localized.

Suspended matter
      Solids that are not in true solution and that can be removed by filtration they usually contribute       directly to turbidity, small particles of solid pollutants that resist separation by conventional       methods; operationally greater than 0.45 microns in size; also known as non-filterable residue,       suspended solids or suspended sediment.

Suspended metals or substances
      Metals or substances attached to suspended solids.

Suspended sediment
      Very fine soil particles that remain in suspension in water for a considerable period of time due       to the upward components of turbulence and currents, can be removed by filtration and       contribute to turbidity.

Suspended solids
      Solids that are not in true solution and that can be removed by filtration they usually contribute       directly to turbidity, small particles of solid pollutants that resist separation by conventional       methods; operationally greater than 0.45 microns in size; also known as non-filterable residue,       suspended matter or suspended sediment.

Suspension
      Large particles are kept from settling out of a liquid by gravity due to motion or agitation of the
      liquid, (see solute, particulate).

Swamp
      A wetland that is permanently or seasonally submerged in shallow water and whose vegetation
      is dominated by shrubs and trees.

Synergism
      Combined activity such that the effect is either the additive of separate effects or greater than the
      sum of the separate effects.


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T

TDS, total dissolved solids
      A quantitative measure of the total dissolved organic and inorganic solids concentration in       water, an indicator test used for water analysis and also a measure of the mineral content       of bottled water and ground water, one can monitor electrical conductivity quickly in the field       and estimate total dissolved solids or TDS without doing any lab tests at all using hand-held       testers since there is a relationship between TDS and conductivity, sum of all dissolved       materials such as salts, which are non-filterable and remain following evaporation of the water,       (see specific conductance).

Temporal
      Of, or relating to, time.

Tertiary sewage treatment
      A third step in sewage treatment usually directed towards greatly increasing the removal       efficiency of nutrients, removal from wastewater of traces of organic chemicals and dissolved       solids that remain after primary sewage treatment and secondary sewage treatment,       selected biological, physical, and chemical separation processes to remove organic and       inorganic substances that resist conventional treatment practices, consists of flocculation       basins, clarifiers, filters and chlorine basins or ozone and ultraviolet radiation processes, the       additional treatment of effluent beyond that of primary and secondary sewage treatment       methods to obtain a very high quality of effluent.

Tertiary wastewater treatment
      A third step in sewage treatment usually directed towards greatly increasing the removal       efficiency of nutrients, removal from wastewater of traces of organic chemicals and dissolved       solids that remain after primary sewage treatment and secondary sewage treatment,       selected biological, physical, and chemical separation processes to remove organic and       inorganic substances that resist conventional treatment practices, consists of flocculation       basins, clarifiers, filters and chlorine basins or ozone and ultraviolet radiation processes, the       additional treatment of effluent beyond that of primary and secondary sewage treatment       methods to obtain a very high quality of effluent.

Thermal pollution
      An increase in air or water temperature that harms the climate or ecology of an area, a reduction       in water quality caused by increasing its temperature, often due to disposal of waste heat from       industrial or power generation processes.

Thermocline
      The fairly thin zone in a lake that separates the upper warmer zone, epilimnion, from the lower
      colder zone, hypolimnion.

Tissue
      A group of cells of similar structure and function which perform a specific task in an organism.

TOC, Total organic carbon
      Sum of all organic carbon compounds in water.

Total dissolved solids, TDS
      A quantitative measure of the total dissolved organic and inorganic solids concentration in       water, an indicator test used for water analysis and also a measure of the mineral content
      of bottled water and ground water, one can monitor electrical conductivity quickly in the field        and estimate total dissolved solids or TDS without doing any lab tests at all using hand-held        testers since there is a relationship between TDS and conductivity, sum of all dissolved       materials such as salts, which are non-filterable and remain following evaporation of the water,       (see  specific conductance).

Total metals or substances
      A quantitative measure of the metals or substances both in the dissolved state and those
      sorbed to particulate matter in suspension.

Total organic carbon, TOC
      Sum of all organic carbon compounds in water.

Total suspended solids, TSS
      The total suspended solids in water removable with a 0.45 micrometer mesh filter.

Toxic
      Poisonous or harmful.

Toxicant
      An element or compound with a harmful or lethal effect on the physiology, behaviour,
      reproduction or survival of an organism.

Toxicity
      A measure of how poisonous a toxin is to an organism.

Toxicity test
      A bioassay 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       concentration of chemical or effluent sample, living organisms are subjected to varying       dilutions of polluted water or water containing known amounts of presumed or known toxins or       contaminated sediment, mortality, declines in reproductive rates or behavioral changes       indicate a toxic response.

Toxin
      A compound or element which is toxic or poisonous in common usage. More strictly a toxin is
      a natural toxicant made by an organism as opposed to poisons manufactured by man.

Transpiration
      The loss of water into the atmosphere from living plants, direct transfer of water from the leaves
      of living plants to the atmosphere, the passage of water vapour from a living body through
      membranes or pores, process by which water that is absorbed by plants, usually through the       roots, is evaporated into the atmosphere from the plant surface, such as leaf pores or stomata,       (see evapotranspiration, vapourization, evaporation.)

Tributary
      A smaller stream which joins a larger stream, usually, a number of smaller tributaries merge to
      form a river.

Trihalomethanes
      Chlorinated organic chemicals which are formed when water containing organic materials is
      disinfected with chlorine, these compounds are toxic.

Trochophore
      Free-swimming ciliate larvae of marine polychaete worms and other invertebrates.

Trophic
      Related to nutrition, referring to one of the hierarchial levels in the food web or food chain
      between the many producers at the bottom and the few predators at the top.

TSS, Total suspended solids
      The total suspended solids in water removable with a 0.45 micrometer mesh filter.

Turbid
      Coloured or opaque due to matter in suspension, rivers and lakes may become turbid after a
      rainfall due to erosion and surface runoff containing particulate matter, there is sufficient
      material in suspension that visibility is decreased.

Turbidity
      The relative lack of clarity or cloudiness, of water, caused by suspended material, sediments,       colored materials in solution and plankton, correlates, inversely, with available light for       photosynthesis, the quantity of solid particles that are suspended in water and that cause light       rays passing through the water to scatter, turbidity makes the water opaque in extreme cases,       measured in nephelometric turbidity units, NTU.


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U

µ/L, Micrograms per litre
      A concentration unit of chemical constituents in solution; the weight of solute per unit volume
      of solvent, usually water, one thousand micrograms per litre is equivalent to 1 milligram per
      litre, this measure is equivalent to parts per billion or ppb.

Unsaturated zone
      The zone immediately below the land surface where the soil pores contain both water and air,
      the soil is not totally saturated with water, (see aquifer where the pores are saturated with
      water).


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V

Vapourization
      The change of state from a liquid to a gas, the change by which any substance is converted from       a liquid state and carried off as a vapor, the process of liquid water becoming water vapor from       water surfaces, land surfaces and snow fields, (see condensation, sublimation, evaporation,       transpiration, evapotranspiration).

Virus
      Small non-cellular parasitic organisms consisting of little more than DNA, or RNA in a protein
      coat, often crystalline, dependent completely on the cellular machinery of their hosts to complete
      their life cycle and reproduce.

Volatilization
      The change of state from a liquid to a gas, the change by which any substance is converted from       a liquid state and carried off as a vapor, the process of liquid water becoming water vapor from       water surfaces, land surfaces and snow fields, volatilization, (see condensation, sublimation,       vapourization, transpiration, evapotranspiration, evaporation).


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W

Waste
      Refuse or other unwanted material.

Waste discharge
      A pipe or ditch containing wastewater which empties into a water course.

Wastewater
      Water with waste materials or pollutants dissolved in it, containing waste including       greywater, blackwater or water contaminated by contact with waste, including
      process-generated and contaminated rainfall runoff, water that has been used in homes,       industries and businesses that is not suitable for reuse unless it is treated.

Wastewater treatment
      The complete wastewater treatment process typically involves a three-phase process, in the       primary wastewater treatment process, which incorporates physical aspects, untreated water       is passed through a series of screens to remove solid wastes, in the secondary wastewater       treatment process, typically involving biological and chemical processes, screened       wastewater is then passed a series of holding and aeration tanks and ponds, the tertiary       wastewater treatment process consists of flocculation basins, clarifiers, filters and chlorine       basins or ozone and ultraviolet radiation processes.

Water column
      The portion of an aquatic or marine environment extending from the water surface to the bottom
      or the surface of the sediment.

Water cycle
      The 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, the       circuit of water movement from the oceans to the atmosphere and to the Earth and back to the       atmosphere through various stages or processes such as precipitation, interception, runoff,       infiltration, percolation, storage, evaporation and transportation, (see 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
      A term used to describe the chemical, physical and biological characteristics of water, usually
      in respect to its suitability for a particular purpose.

Water quality criteria
      Scientifically derived ambient numerical values for physical, chemical or biological       characteristics of water, biota or sediment which must not be exceeded to prevent specified       detrimental effects from occurring to water uses, recommended concentrations, levels or       narrative statements that should not be exceeded in order to protect the life or health of             organisms.

Water quality guideline
      Numerical concentration or narrative statement recommended to support and maintain a
      designated water use.

Water quality objective
      A water quality criterion or water quality guideline adapted to protect the most sensitive
      designated water use at a specific location with an adequate degree of safety, taking local
      circumstances into account.

Water quality standard
      Law or regulation that consists 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 table
      The level below the surface of the earth at which the ground becomes saturated with water, the
      surface of an unconfined aquifer which fluctuates due to seasonal precipitation, the top of the
      water surface in the saturated part of an aquifer.

Water treatment
      A method of cleaning water for a specific purpose, such as drinking water, irrigation water or
      discharge to a stream.

Water use
      Water that is used for a specific purpose, such as for domestic use, irrigation, or industrial       processing, associated with human influence on the hydrologic cycle, includes water       withdrawal from surface water and ground water sources, water delivery to homes and       businesses, consumptive use of water, water released from wastewater treatment plants,       water returned to the environment and in-stream uses, such as using water to produce       hydroelectric power or for navigation.

Watershed
      The land area where precipitation runs off into streams, rivers, lakes and reservoirs, a land       feature that can be identified by tracing a line along the highest elevations between two areas on       a map, often a ridge, large drainage basins contain many smaller drainage sub-basins, land       area drained by a river or stream, the natural hydrologic unit associated with numerous       ecological and physical processes involving water, the most appropriate geographic unit for       management of water quality, (see drainage basin).

Well
      An artificial excavation, by any method, for the purposes of withdrawing water from the       underground aquifer, 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.

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, an area where saturation with water is the dominant       influence on soil parameters and on composition of the plant community, a bog, pond, fen,       estuary, swamp, peatland or marsh.

Whole-effluent toxicity
      The aggregate toxic effect of an effluent measured directly by a toxicity test.

Withdrawal
      Water removed from a ground water or surface water source for anthropogenic use.

Worm
      Multicellular invertebrate organisms in several different Phyla which are soft-bodied, elongate and
      often parasitic or pathogenic.


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X

Xerophytic
      Refers to plants, generally, that are able to grow under very arid conditions where water is
      scarce, physiological and morphological adaptations to allow growth under arid conditions.

Xeroscaping
      Planting vegetation that requires very little water.


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Y

Yield
      A quantitative measure of how much water can be pumped from a well, for example, either in       absolute units or as a percentage of what is actually present in the aquifer, expressed as an       amount per unit of time or as an instantaneous, continuous withdrawal rate, the various values       will differ depending upon the recharge rate of the aquifer, the increase in biomass or       productivity over a season which is not necessarily reflected in the instantaneous standing       crop.


Z

Zooplankton
      Primarily microscopic animals which swim freely in the water column or are carried about by
      water currents, many feed on phytoplankton and are in turn a staple diet of small fish.

Zygote
      The diploid union of haploid sperm and haploid egg, the start of the next generation.



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This page was last updated August 1, 2001


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