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Absorption, Acclimatization, Acid, Acid Deposition/Acid Rain, Activated Carbon, Adhesion, Adsorbent, Adsorption, Advanced Waste Water Treatment, Aeration Tank, Aeration, Agglomeration, Algae, Alkalinity, Anaerobic, Anion, Anion Exchange, Attrition.

Backwash, Bacteria, Baghouse Filter, Bar Screen, Base, Bed, Bed Depth, Biochemical Oxygen Demand, Biodegradable, Biological Control, Brackish Water, Brine.

Cadmium, Calcium, Capacity, Carbon Adsorber, Carbon Dioxide, Carbon Monoxide, Carcinogen, Carcinogenic, Cation, Cation Exchange, Caustic, Caustic Soda, Cesium, Chelate, Chemical Oxygen Demand, Chemical Treatment, Chlorination, Chlorinator, Chlorine, Chlorine-Contact Chamber, Chlorofluorocarbons, Clarification, Clarifier, Coagulation, Coliform Organism, Conductance, Conductivity, Coolant, Cooling Tower.

D.I. or DI, Dechlorination, Deionization, Demineralization, Denitrification, Desalinization, Digester, Digestion, Disinfectant, Disinfection, Dispersant, Disposal, Dissolved Oxygen, Dissolved Solids, Distillation.

Ecology, Effluent, Electrodialysis, Electrostatic Precipitator, Equivalent Per Million, Erosion, Evaporation Ponds, Exhaustion.

Filter, Filtration, Floc, Flocculation, Fresh Water, Fungi.

Germicide, GPG, Grain, Grain per Gallon, Gram, Granular Activated Carbon Treatment, Gray Water, Greenhouse Effect, Greensand.

Flow Control, Flow Rate, Flowmeter, Fluoridation, Fluorides, Fluorocarbon, Fluorosis, Formaldehyde, Fouling, Freeboard.

Hard Water, Hardness, Heavy Metals, Hydrologic Cycle.

Infiltration, Inflow, Influent, Insecticide, Ion Exchange, Ion Exchange Treatment, Ion Exchanger, Ion, Ionization, Ion, Ionization, Ion, Ionization, Iron, Iron Bacteria.

Lagoon, Langelier’s Index, Leachate Collection System, Leachate, Lime.

Magnesium, Manganese, Manganese Greensand, Mechanical Aeration, Mechanical Turbulence, Mercury, Methane, Micron, Mineral.

Negative Charge, Nitrate, Noncarbonate Hardness, Nutrient.

Operation And Maintenance, Operation Pressure, Organic Chemicals/Compounds, Organic Matter, Organism, Organophosphates, Osmosis, Overturn, Oxidant, Oxidation, Oxidation Pond, Oxidation, Ozonator, Ozone, Ozone Depletion.

Packed Tower, Parts Per Million, Pathogens, Percolation, Permeability, PH, Plankton, Pollution, Polyelectrolytes, Polymer, Polyvinyl Chloride, Potable Water, PPM, PPM/PPB, Precipitate, Precipitate, Precipitation, Precipitators, Pretreatment, Primary Waste Treatment.

Raw Water, Receiving Waters, Recharge Area, Recharge, Regenerant, Regeneration, Resin, Resistance, Reverse Osmosis.

Saline Water, Salinity salt, Salt Water Intrusion, sand Filters, Secondary Treatment, Sediments, Sequester, Sequestering Agent, Silt, Slow Sand Filtration, Sludge, Soda Ash, Sodium, Sodium Chloride, Soft Detergents, Soft Water, Soot, Sorption, Specific Gravity, Sterilization, Sulfate-Reducing Bacteria, Sulfur, Sulfur Dioxide, Surfactant, Suspended Solids.

TDS, Tertiary Treatment, Total Acidity, Total Alkalinity, Total Dissolved Solids, Total Hardness, Total Solids, Total Suspended Solids, Trickling Filte, Turbidity.

Ultrafiltration, Ultrapure Water, Ultraviolet, Ultraviolet Absorber, Ultraviolet Chamber, Ultraviolet Demand, Ultraviolet Dosage, Ultraviolet Rays, Uniformity Coefficient, Univalent, Upflow, Upflow Softening, Uranium.

Vacuum Breaker, Validation, Virus, Viscosity, Vocs, Void Volume, Volatile, Volatile Organic Chemicals, Volatile Organic Compound.

Waste Treatment plant, Waste Treatment Stream, Waste Water, Water, Water Retention, Water Softener, Water Softener, Water Softener, Water Softener salt, Water Softening, Water Treatment Device, WBA, Weak Acid Cation Exchangers, Weak Base Anion Exchangers, Weir, WFI, WHO.


Zeolite Softening,Zeolites, Zero Discharge Water, Zero Soft Wate, Zone Of Aeration, Zone Of Saturation, Zooplankton, Zooplankton.

Absorption :
The passage of one substance into or through another; e.g., an operation in which one or more soluble components of a gas mixture are dissolved in a liquid.

Acclimatization :
The physiological and behavioral adjustments of an organism to changes in its environment.

A substance which releases hydrogen ions when dissolved in water. Most acids will dissolve the common metals, and will react with a base to form a neutral salt and water.

Acid Deposition/Acid Rain :
A complex chemical and atmospheric phenomenon that occurs when emissions of sulfur and nitrogen compounds and other substances are transformed by chemical processes in the atmosphere, often far from the original sources, and then deposited on earth in either a wet or dry form. The wet forms, popularly called “acid rain,” can fall as rain, snow, or fog. The dry forms are acidic gases or particulates.

A granular material usually produced by the roasting of cellulose base substances, such as wood or coconut shells, in the absence of air. It has a very porous structure and is used in water conditioning as an adsorbent for organic matter and certain dissolved gases. Sometimes called “activated charcoal”.

Adhesion :
Molecular attraction which holds the surfaces of two substances in contact.

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

Adsorption :
1. Adhesion of molecules of gas, liquid, or dissolved solids to a surface.
2. An advanced method of treating wastes in which activated carbon removes organic matter from wastewater.

Advanced Waste Water Treatment :
Any treatment of sewage that goes beyond the secondary or biological water treatment stage and includes the removal of nutrients such as phosphorus and nitrogen and a high percentage of suspended solids. (See primary, secondary treatment.)

Aeration Tank :
A chamber used to inject air into water.

Aeration :
A process which promotes biological degradation of organic water. The process may be passive (as when waste is exposed to air), or active (as when a mixing or bubbling device introduces the air).

Agglomeration :
The process by which precipitation particles grow larger by collision or contact with cloud particles or other precipitation particles.

Algae :
Simple rootless plants that grow in sunlit waters in relative proportion to the amounts of nutrients available. They can affect water quality adversely by lowering the dissolved oxygen in the water. They are food for fish and small aquatic animals.

The quantitative capacity of a water or water solution to neutralize an acid. It is usually measured by titration with a standard acid solution of sulfuric acid, and expressed in terms of its calcium carbonate equivalent.

Anaerobic :
A life or process that occurs in, or is not destroyed by, the absence of oxygen.

A negatively charged ion in solution, such as bicarbonate, chloride or sulfate.

An ion exchange process in which anions in solution are exchanged for other anions from an ion exchanger. In demineralization, for example, bicarbonate, chloride and sulfate anions are removed from solution in exchange for a chemically equivalent number of hydroxide anions from the anion exchange resin.

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

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

Bacteria :
(Singular: bacterium) Microscopic living organisms which can aid in pollution control by consuming or breaking down organic matter in sewage. or by similarly acting on oil spills or other water pollutants. Bacteria in soil, water or air can also cause human, animal and plant health problems.

Baghouse Filter :
Large fabric bag, usually made of glass fibers, used to eliminate intermediate and large (greater than 20 microns in diameter) particles. This device operates in a way similar to the bag of an electric vacuum cleaner, passing the air and smaller particulate matter, while entrapping the larger particulates.

Bar Screen :
In wastewater treatment, a device used to remove large solids.

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

The exchange or filter media in a column or other tank or operational vessel.

The height of the ion exchange or filter media in the vessel after preparation for service.

Biochemical Oxygen Demand (BOD) :
A measure of the amount of oxygen consumed in the biological processes that break down organic matter in water. The greater the BOD, the greater the degree of pollution.

Biodegradable :
The ability to break down or decompose rapidly under natural conditions and processes.

Biological Control :
In pest control, the use of animals and organisms that eat or otherwise kill or out-compete pests.

Brackish Water :
A mixture of fresh and salt water.

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

Cadmium (CD) :
A heavy metal element that accumulates in the environment

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

An expression of the quantity of an undesirable material which can be removed by a water conditioner between cleaning regeneration or replacement, as determined under standard test conditions. For ion exchange water softeners, the capacity is expressed in grains of hardness removal between successive regenerations and is related to the pound of salt used in regeneration. For filters, the capacity may be expressed in the length of time or total gallons delivered between servicing.

Carbon Adsorber :
An add-on control device which uses activated carbon to absorb volatile organic compounds from a gas stream. The VOCs are later recovered from the carbon.

A gas present in the atmosphere and formed by the decay of organic matter; the gas in carbonated beverages; in water it forms carbonic acid.

Carbon Monoxide (C0) :
A colorless, odorless, poisonous gas produced by incomplete fossil fuel combustion.

Carcinogen :
Any substance that can cause or contribute to the production of cancer.

Carcinogenic :

Cathodic Protection :
A technique to prevent corrosion of a metal surface by making that surface the cathode of an electrochemical cell.

An ion with a positive electrical charge, such as calcium, magnesium and sodium.

Ion exchange process in which cations in solution are exchanged for other cations form and ion exchanger.

Any substance capable of burning or destroying animal flesh or tissue.

Caustic Soda :
Sodium hydroxide, a strong alkaline substance used as the cleaning agent in some detergents.

Cesium (Cs) :
A silver-white, soft ductile element of the alkali metal group that is the most electropositive element known. Used especially in photoelectric cells.

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

Chemical Oxygen Demand (COD) :
A measure of the oxygen required to oxidize all compounds in water, both organic and inorganic.

Chemical Treatment :
Any one of a variety of technologies that use chemicals or a variety of chemical processes to treat waste.

Chlorination :
The application of chlorine to drinking water, sewage, or industrial waste to disinfect or to oxidize undesirable compounds.

Chlorinator :
A device that adds chlorine, in gas or liquid form, to water or sewage to kill infectious bacteria.

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

Chlorine-Contact Chamber :
That part of a water treatment plant where effluent is disinfected by chlorine.

Chlorofluorocarbons (CFCs) :
A family of inert, nontoxic, and easily liquified chemicals used in refrigeration, air conditioning, packaging, insulation, or as solvents and aerosol propellants. Because CFCs are not destroyed in the lower atmosphere they drift into the upper atmosphere where their chlorine components destroy ozone.

Clarification :
Clearing action that occurs during wastewater treatment when solids settle out. This is often aided by centrifugal action and chemically induced coagulation in wastewater.

Clarifier :
A tank in which solids are settled to the bottom and are subsequently removed as sludge.

A material, such as alum, which will form a gelatinous precipitate in water, and cause the agglomeration of finely divided particles into larger particles which can then be removed by settling and / or filtration.

Coagulation :
A clumping of particles in wastewater to settle out impurities. It is often induced by chemicals, such as lime, alum, and iron salts.

Coliform Index :
A rating of the purity of water based on a count of fecal bacteria.

Coliform Organism :
Microorganisms found in the intestinal tract of humans and animals. Their presence in water indicates fecal pollution and potentially dangerous bacterial contamination by disease-causing microorganisms.

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

The quality or power to carry electrical current; in water, the conductivity is related to the concentration of ions capable of carrying electrical current.

Coolant :
A liquid or gas used to reduce the heat generated by power production in nuclear reactors, electric generators, various industrial and mechanical processes, and automobile engines.

Cooling Tower :
A structure that helps remove heat from water used as a coolant; e.g., in electric power generating plants.

Corrosion :
The dissolving and wearing away of metal caused by a chemical reaction such as between water and the pipes that the water contacts, chemicals touching a metal surface, or contact between two metals.

Cubic Feet Per Minute (CFM) :
A measure of the volume of a substance flowing through air within a fixed period of time. With regard to indoor air, refers to the amount of air, in cubic feet, that is exchanged with indoor air in a minute’s time, or an air exchange rate.

A series of events or steps which ultimately lead back to the starting point, such as the exhaustion- regeneration cycle of an ion exchange system; sometimes incorrectly used in reference to a single step of a complete cycle.

D.I. or DI :
Abbreviation for “deionization”.

Dechlorination :
Removal of chlorine from a substance by chemically replacing it with hydrogen or hydroxide ions in order to detoxify the substances involved.

The removal of all ionized minerals and salts (both cationic and anionic) from a solution by a two-phase ion exchange procedure. First, positively charged for a chemically equivalent amount of hydrogen ions. Second, negatively charged ions are removed by an anion exchange resin for a chemically equivalent amount of hydroxide ions. The hydrogen and hydroxide ions introduced in this process unite to form water molecules. The term is often used interchangeably with demineralization.

The removal of ionized inorganic minerals and salts (not organic materials) from a solution by a two-phase ion exchange procedure; similar to deionization, and the two terms are often used interchangeably.

Denitrification :
The anaerobic biological reduction of nitrate nitrogen to nitrogen gas.

Desalinization :
Removing salt from ocean or brackish water.

Digester :
In wastewater treatment, a closed tank; in solid waste conversion, a unit in which bacterial action is induced and accelerated in order to break down organic matter and establish the proper carbon to nitrogen ratio.

Digestion :
The biochemical decomposition of organic matter, resulting in partial gasification, liquefaction, and mineralization of pollutants.

Disinfectant :
A chemical or physical process that kills pathogenic organisms in water. Chlorine is often used to disinfect sewage treatment effluent, water supplies, wells, and swimming pools.

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

Dispersant :
A chemical agent used to break up concentrations of organic material such as spilled oil.

Disposal :
Final placement or destruction of toxic, radioactive, or other wastes; surplus or banned pesticides or other chemicals; polluted soils; and drums containing hazardous materials from removal actions or accidental releases. Disposal may be accomplished through use of approved secure landfills, surface impoundments, land farming, deep well injection, ocean dumping, or incineration.

Dissolved Oxygen (DO) :
The oxygen freely available in water. Dissolved oxygen is vital to fish and other aquatic life and for the prevention of odors. Traditionally, the level of dissolved oxygen has been accepted as the single most important indicator of a water body’s ability to support desirable aquatic life. Secondary and advanced waste treatment are generally designed to protect DO in waste-receiving waters.

The weight of matter in true solution in a stated volume of water; includes both inorganic and organic matter; usually determined by weighing the residue after evaporation of the water at 105 or 180 Degrees Celcius.

The process in which a liquid, such as water, is converted into its vapor state by heating, and the vapor cooled and condensed to the liquid state and collected; used to remove solids and other impurities from water, multiple distillations are required for extreme purity.

Ecology :
The relationship of living things to one another and their environment, or the study of such relationships.

Effluent :
Wastewater—treated or untreated—that flows out of a treatment plant, sewer, or industrial outfall. Generally refers to wastes discharged into surface waters.

Electrodialysis :
A process that uses electrical current applied to permeable membranes to remove minerals from water. Often used to desalinize salty or brackish water

Electrostatic Precipitator (ESP) :
An air pollution control device that removes particles from a gas stream (smoke) after combustion occurs. The ESP imparts an electrical charge to the particles, causing them to adhere to metal plates inside the precipitator. Rapping on the plates causes the particles to fall into a hopper for disposal.

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

Erosion :
The wearing away of land surface by wind or water. Erosion occurs naturally from weather or runoff but can be intensified by land-clearing practices related to farming, residential or industrial development, road building, or timber-cutting.

Evaporation Ponds :
Areas where sewage sludge is dumped and allowed to dry out.

The state of an ion exchange material in which it is no longer capable of effective function due to the depletion of the initial supply of exchangeable ions; the exhaustion point may be defined in terms of a limiting concentration of matter in the effluent, or in the case of demineralization, in terms of electrical conductivity.

Specifically, a device or system for the removal of solid particles (suspended solids); in general, includes mechanical, adsorptive, oxidizing and neutralizing filters.

Filtration :
A treatment process, under the control of qualified operators, for removing solid (particulate) matter from water by passing the water through porous media such as sand or a man-made filter. The process is often used to remove particles that contain pathogenic organisms.

Floc :
A clump of solids formed in sewage by biological or chemical action.

The agglomeration of finely divided suspended solids into larger, usually gelatinous, particles; the development of a “floc” after treatment with a coagulant by gentle stirring or mixing.

A device designed to limit the flow of water or regenerant to a predetermined value over a broad range of inlet water pressures.

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

Flowmeter :
A gauge that shows the speed of wastewater moving through a treatment plant. Also used to measure the speed of liquids moving through various industrial processes.

The addition of a fluoride compound to a water supply to produce the concentration desired for the reduction in incidence of dental caries.

Fluorides :
Gaseous, solid, or dissolved compounds containing fluorine that result from industrial processes. Excessive amounts in food can lead to fluor.

Fluorocarbon (FCs) :
Any of a number of organic compounds analogous to hydrocarbons in which one or more hydrogen atoms are replaced by fluorine. Once used in the United States as a propellant in aerosols. they are now primarily used in coolants and some industrial processes. FCs containing chlorine are called chlorofluorocarbons (CFCs). They are believed to be modifying the ozone layer in the stratosphere, thereby allowing more harmful solar radiation to reach the Earth’s surface.

Fluorosis :
An abnormal condition caused by excessive intake of fluorine, characterized chiefly by mottling of the teeth.

Formaldehyde :
A colorless, pungent, irritating gas, CH20, used chiefly as a disinfectant and preservative and in synthesizing other compounds and resins.

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

The vertical distance between a bed of filter media or ion exchange material and the over flow or collector for backwash water; the height above the bed of granular media available for bed expansion during backwashing; may be expressed either as a linear distance or a percentage of bed depth.

Fresh Water :
Water that generally contains less than 1,000 milligrams-per-liter of dissolved solids.

Fungi :
(Singular, Fungus) Molds, mildews, yeasts, mushrooms, and puff-balls, a group organisms that lack chlorophyll (i.e., are not photosynthetic) and which are usually non-mobile, filamentous, and multicellular. Some grow in the ground, others attach themselves to decaying trees and other plants, getting their nutrition from decomposing organic matter. Some cause disease, others stabilize sewage and break down solid wastes in composting.Fungicide: Pesticides which are used to control, prevent, or destroy fungi.

Germicide :
compound that kills disease-causing microorganisms.
Abbreviation for “grain per gallon”.

(gr.) A unit of weight equal to 1/7000th of a pound, or 0.0648 gram.

(gpg) A common basis for reporting water analyses in the United States and Canada; one grain per U.S. gallon equals 17.12 milligrams per liter (mg/1) or parts per million (ppm).

(g) The basic unit of weight (mass) of the metric system, originally intended to be the weight of 1 cubic centimeter of water a 4 DegC.

Granular Activated Carbon Treatment :
A filtering system often used in small water systems and individual homes to remove organics. GAC can be highly effective in removing elevated levels of radon from water.

Gray Water :
The term given to domestic wastewater composed of washwater from sinks, kitchen sinks, bathroom sinks and tubs, and laundry tubs.

Greenhouse Effect :
The warming of the Earth’s atmosphere caused by a build-up of carbon dioxide or other trace gases; it is believed by many scientists that this build-up allows light from the sun’s rays to heat the Earth but prevents a counterbalancing loss of heat.

A natural mineral, primarily composed of complex silicates, which possess ion exchange properties.

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

A characteristic of natural water due to the presence of dissolved calcium and magnesium; water hardness is responsible for most scale formation in pipes and water heaters, and forms insoluble “curd” when it reacts with soaps. Hardness is usually expressed in grains per gallon, parts per million, or milligrams per liter, all as calcium carbonate equivalent.

Heavy Metals :
Metallic elements with high atomic weights, e.g.. mercury, chromium, cadmium, arsenic, and lead. They can damage living things at low concentrations and tend to accumulate in the food chain.

The water cycle, including precipitation of water from the atmosphere as rain or snow, flow of water over or through the earth, and evaporation or transpiration to water vapor in the atmosphere. (See Transpiration)

Infiltration :
1. The penetration of water through the ground surface into sub-surface soil or the penetration of water from the soil into sewer or other pipes through defective joints, connections, or manhole walls.
2. A land application technique where large volumes of waste water are applied to land, allowed to penetrate the surface and percolate through the underlying soil. (See: percolation)

Inflow :
Entry of extraneous rain water into a sewer system from sources other than infiltration, such as basement drains, manholes, storm drains, and street washing.

Influent :
Water, wastewater, or other liquid flowing into a reservoir, basin, or treatment plant.

Insecticide :
A pesticide compound specifically used to kill or control the growth of insects.

A reversible process in which ions are released from an insoluble permanent material in exchange for other ions in a surrounding solution; the direction of the exchange depends upon the affinities of the ion exchanger for the ions present, and the concentrations of the ions in the solution.

Ion Exchange Treatment :
A common water softening method often found on a large scale at water purification plants that remove some organics and radium by adding calcium oxide or calcium hydroxide to increase the ph to a level where the metals will precipitate out.

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

Ion :
An electrically charged atom or group of atoms which can be drawn from waste water during the electrodialysis process.

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

An element often found dissolved in ground water (in the form of ferrous iron) in concentrations usually ranging from zero to 10 ppm (mg/1). It is objectionable in water supplies because of the staining caused after oxidation and precipitation (as ferric hydroxide), because of tastes, and because of unsightly colors produced when iron reacts with tannins in beverages such as coffee and tea.

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

Lagoon :
(1) A shallow pond where sunlight, bacterial action, and oxygen work to purify wastewater; also used to storage of wastewaters or spent nuclear fuel rods.
(2) Shallow body of water, often separated from the sea by coral reefs or sandbars.

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

Leachate Collection System :
A system that gathers leachate and pumps it to the surface for treatment.

Leachate :
A liquid that results from water collecting contaminants as it trickles through wastes, agricultural pesticides or fertilizers. Leaching may occur in fanning areas, feedlots, and landfills, and may result in hazardous substances entering surface water, ground water, or soil.

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

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

An element sometimes found dissolved in ground water, usually with dissolved iron but in lower concentrations; causes black stains, and other problems similar to iron.

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

Mechanical Aeration :
Use of mechanical energy to inject air into water to cause a waste stream to absorb oxygen.

Mechanical Turbulence :
Random irregularities of fluid motion in air caused by buildings or mechanical, non-thermal, processes.

Mercury :
A heavy metal that can accumulate in the environment and is highly toxic if breathed or swallowed. (See: heavy metals.)

Methane :
A colorless, nonpoisonous, flammable gas created by anaerobic decomposition of organic compounds.

A linear measure equal to one millionth of a meter.

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

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

Nitrate :
A compound containing nitrogen which can exist in the atmosphere or as a dissolved gas in water and which can have harmful effects on humans and animals. Nitrates in water can cause severe illness in infants and cows.

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

Nutrient :
Any substance assimilated by living things that promotes growth. The term is generally applied to nitrogen and phosphorus in wastewater, but is also applied to other essential and trace elements.

Operation And Maintenance :
1. Activities conducted at a site after a Super-fund site action is completed to ensure that the action is effective and operating properly.
2. Actions taken after construction to assure that facilities constructed to treat waste water will be properly operated, maintained, and managed to achieve efficiency levels and prescribed effluent limitations in an optimum manner.

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

Organic Chemicals/Compounds :
Animal or plant-produced substances containing mainly carbon, hydrogen, and oxygen.

Organic Matter :
Carbonaceous waste contained in plant or animal matter and originating from domestic or industrial sources.

Organic :
1. Referring to or derived from living organisms. 2. In chemistry any compound containing carbon.

Organism :
Any living thing.

Organophosphates :
Pesticide chemicals that contain phosphorus; used to control insects. They are short-lived, but some can be toxic when first applied.

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

Overturn :
The period of mixing (turnover), by top to bottom circulation, of previously stratified water masses. This phenomenon may occur in spring and/or fall, or after storms. It results in a uniformity of chemical and physical properties of the water at all depths.

Oxidant :
A substance containing oxygen that reacts chemically in air to produce a new substance. The primary ingredient of photochemical smog.

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

Oxidation Pond :
A man-made lake or body of water in which waste is consumed by bacteria. It is used most frequently with other waste-treatment processes. An oxidation pond is basically the same as a sewage lagoon.

Oxidation :
1. The addition of oxygen which breaks down organic waste or chemicals such as cyanides, phenols, and organic sulfur compounds in sewage by bacterial and chemical means.
2. Oxygen combining with other elements.
3. The process in chemistry whereby electrons are removed from a molecule.

Ozonator :
A device that adds ozone to water.

Ozone (03) :
Found in two layers of the atmosphere, the stratosphere and the troposphere. In the stratosphere (the atmospheric layer beginning 7 to 10 miles above the earth’s surface) ozone is a form of oxygen found naturally which provides a protective layer shielding the earth from ultraviolet radiation’s harmful health effects on humans and the environment. In the troposphere (the layer extending up 7 to 10 miles from the earth’s surface), ozone is a chemical oxidant and major component of photochemical smog. Ozone can seriously affect the human respiratory system and is one of the most prevalent and widespread of all the criteria pollutants for which the Clean Air Act required EPA to set standards. Ozone in the troposphere is produced through complex chemical reactions of nitrogen oxides, which are among the primary pollutants emitted by combustion sources; hydrocarbons, released into the atmosphere through the combustion, handling and processing of petroleum products; and sunlight.

Ozone Depletion :
Destruction of the stratospheric ozone layer which shields the earth from ultraviolet radiation harmful to biological life. This destruction of ozone is caused by the breakdown of certain chlorine and/or-bromine containing compounds (chlorofluorocarbons or halons) which break down when they reach the stratosphere and catalytically destroy ozone molecules.

Packed Tower :
A pollution control device that forces dirty air through a tower packed with crushed rock or wood chips while liquid is sprayed over the packing material. The pollutants in the air stream either dissolve or chemically react with the liquid.

A common basis for reporting the results of water and wastewater analysis, indicating the number of parts by weight of a dissolved or suspended constituent, per million parts by weight of water or other solvent, In dilute water solutions, one part per million is practically equal to one milligram per liter, which is the preferred unit.

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.

Percolation :
The movement of water downward and radially through the sub-surface soil layers, usually continuing downward to the ground water.

Permeability :
The rate at which liquids pass through soil or other materials in a specified direction.

pH :
stands for “potenz hydrogen”., German for “potential of hydrogen”. In water chemistry, pH is expressed as the concentraton of hydrogen ions to hydroxl ions. The pH scale is a logrithmic scale from 1 to 14, with 7 being neutral; above 7, more alkaline; and below 7 more acidic.

Plankton :
Tiny plants and animals that live in water.

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.

Polyelectrolytes :
Synthetic chemicals that help solids to clump during sewage treatment.

Polymer :
Basic molecular ingredients in plastic.

Polyvinyl Chloride (PVC) :
A tough, environmentally indestructible plastic that releases hydrochloric acid when burned.

Potable Water :
Water that is safe for drinking and cooking.

The abbreviation for “part per million”.

Parts per million/ parts per billion, a way of expressing tiny concentrations of pollutants in air, water, soil, human tissue, food, or other products.

To cause a dissolved substance to form a solid particle which can be removed by settling or filtering, such as in the removal of dissolved iron by oxidation, precipitation, and filtration. The term is also used to refer to the solid formed, and to the condensation of water in the atmosphere to form rain or snow.

Precipitate :
A solid that separates from a solution because of some chemical or physical change.

Precipitation :
Removal of solids from liquid waste so that the hazardous solid portion can be disposed of safely; removal of particles from airborne emissions.

Precipitators :
Air pollution control devices that collect particles from an emissions.

Pretreatment :
Processes used to reduce, eliminate, or alter the nature of wastewater pollutants from non-domestic sources before they are discharged into publicly owned treatment works.

Primary Waste Treatment :
First steps in wastewater treatment; screens and sedimentation tanks are used to remove most materials that floats or will settle. Primary treatment results in the removal of about 30 percent of carbonaceous biochemical oxygen demand from domestic sewage.

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

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

Recharge Area :
A land area in which water reaches to the zone of saturation from surface infiltration, e.g., an area where rainwater soaks through the earth to reach an aquifer.

Recharge :
The process by which water is added to a zone of saturation, usually by percolation from the soil surface, e.g., the recharge of an aquifer.

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

Regeneration :
Manipulation of individual cells or masses of cells to cause them to develop into whole plants.

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

Resistance :
For plants and animals, the ability to withstand poor environmental conditions and/or attacks by chemicals or disease. The ability may be inborn or developed.

Reverse Osmosis :
A water treatment process used in small water systems by adding pressure to force water through a semi-permeable membrane. Reverse osmosis removes most drinking water contaminants. Also used in wastewater treatment. Large-scale reverse osmosis plants are now being developed.

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

Salinity :
The degree of salt in water.

The common name for the specific chemical compound sodium chloride used in the regeneration of ion exchange water softeners. In chemistry, the term is applied to a class of chemical compounds which can be formed by the neutralization of an acid with a base.

Salt Water Intrusion :
The invasion of fresh surface or ground water by salt water. If the salt water comes from the ocean it may be called sea water intrusion.

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.

Secondary Treatment :
The second step in most publicly owned waste treatment systems in which bacteria consume the organic parts of the waste. It is accomplished by bringing together waste, bacteria, and oxygen in trickling filters or in the activated sludge process. This treatment removes floating and settleable solids and about 90 percent of the oxygen-demanding substances and suspended solids. Disinfection is the final stage of secondary treatment. (See: primary, tertiary treatment.)

Sediments :
Soil, sand, and minerals washed from land into water usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals, and clouding the water so that needed sunlight might not reach aquatic plants. Careless farming, mining, and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

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

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

Silt :
Fine particles of sand or rock that can be picked up by the air or water and deposited as sediment.

Slow Sand Filtration :
Treatment process involving passage of raw water through a bed of sand at low velocity which results in the substantial removal of chemical and biological contaminants,

Sludge :
A semi-solid residue from any of a number of air or water treatment processes. Sludge can be a hazardous waste.

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

An ion found in natural water supplies, and introduced to water in the ion exchange water softening process. Sodium compounds are highly soluble, and do not react with soaps or detergents.

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

Soft Detergents :
Cleaning agents that break down in nature.

Soft Water :
Any water that is not “hard,” i.e.. does not contain a significant amount of dissolved minerals such as salts containing calcium or magnesium.

Soot :
Carbon dust formed by incomplete combustion.

Sorption :
The action of soaking up or attracting substances. A process used in many pollution control systems.

The ratio of the weight of a specific volume of a substance compared to the weight of the same volume of pure water at 40C.

Sterilization :
1. In pest control, the use of radiation and chemicals to damage body cells needed for reproduction.
2. The destruction of all living organisms in water or on the surface of various materials. In contrast, disinfection is the destruction of most living organisms in water or on surfaces.

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

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

Sulfur Dioxide (502) :
A heavy, pungent, colorless, gaseous air pollutant formed primarily by the combustion of fossil plants.

Surfactant :
A surface-active agent used in detergents to cause lathering.

Suspended Solids :
Small particles of solid pollutants that float on the surface of, or are suspended in sewage or other liquids. They resist removal by conventional means. (See: Total Suspended Solids.)

The abbreviation for “total dissolved solids”.

Tertiary Treatment :
Advanced cleaning of wastewater that goes beyond the secondary or biological stage. It removes nutrients such as phosphorus and nitrogen and most BOD and suspended solids.
The federal regulation that guides determination of the sites to be corrected under the Superfund program and the program to prevent or control spills into surface waters or other portions of the environment.

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

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

The weight of solids per unit volume of water which are in true solution, usually determined by the evaporation of a measured volume of filtered water, and determination of the residue weight.

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

The weight of all solids, dissolved and suspended organic and inorganic. per unit volume of water, usually determined by the evaporation of a measured volume of water at 105 DegC. in a pre weighed dish.

Total Suspended Solids (TSS) :
A measure of the suspended solids in wastewater, effluent, or water bodies, determined by using tests for “total suspended non-filterable solids.” (See: suspended solids.)

Trickling Filte :
A coarse, biological treatment system in which wastewater is trickled over a bed of stones or other material covered with bacterial growth. The bacteria break down the

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

A method of crossflow filtration (similar to reverse osmosis but using lower pressures) which uses a membrane to separate small colloids and large molecules from water and other liquids. The ultrafiltration process falls between reverse osmosis and microfiltration in terms of the size of particles removed, with ultrafiltration removing particles in the 0.002 to 0.1 micron range, and typically rejecting organics over 1,000 molecular weight while passing ions and smaller organics.

Highly-treated water that is deionized and mineral-free with high resistivity and no organics; it is usually used in the semiconductor and pharmaceutical industries. Ultrapure water is NOT considered biologically pure (potable) or sterile. There is no set numerical standard to determine exactly what “ultrapure” water is or should be.

Pertaining to ultraviolet light.

Radiation (light) having a wavelength shorter than 3900 angstroms the wavelengths of visible light, and longer than 100 angstroms, the wavelengths of x-ray’s. This wavelength puts ultraviolet light at the invisible violet end of the light spectrum. Ultraviolet light is used as a disinfectant.

Substances which absorb ultraviolet radiation (light). ultraviolet absorbers are added to plastic (such as used in plastic tanks and fittings) and rubber products to make them less likely to decay as the result of absorbing ultraviolet rays.

The area where the water is irradiated with ultraviolet rays.

The amount of ultraviolet rays required to inactivate certain microorganisms.

The amount of disinfectant ultraviolet rays delivered to the organisms in the water being disinfected. Dosage is a combination of UV intensity times the contact time and is measured in watt-seconds per square centimeter.

Ultraviolet Rays :
Radiation from the sun that can be useful or potentially harmful. UV rays from one part of the spectrum enhance plant life and are useful in some medical and dental procedures; UV rays from other parts of the spectrum to which humans are exposed (e.g., while getting a sun tan) can cause skin cancer or other tissue damage. The ozone layer in the atmosphere provides a protective shield that limits the amount of ultraviolet rays that reach the Earth’s surface.

The measure of the variation in particle sizes of filter and ion exchange media. The uniformity coefficient is defined as the ratio of the sieve size that will permit passage of 60 percent of the media material by weight to the sieve size that will permit passage of 10 percent of the media material by weight. A uniformity coefficient of 1.00 denotes a material having particle grains all the same size; numbers increasingly greater than one denote increasingly less uniformity.

Having a valence of one. Also called monovalent.

– A pattern of water flow in which a solution (water or regenerant usually) enters at the bottom of the vessel or column and flows out at the top of the vessel or column during any phase of the treatment unit’s operating cycle. The term is used to describe ion exchange system flow patterns or water flow through filter media. A system can have upflow during the treatment cycle and downflow during regeneration. Upflow is also called countercurrent flow. Countercurrent flow means regeneration flows and service flows are in the opposite directions.

A pattern of water flow used in softeners in which the service water flows upward through the ion exchange bed; the media is restricted in movement, usually because of a packed bed. The regeneration brine usually flows downward in such systems. Upflow softening is normally used to achieve higher operating efficiency.

The piping arrangement inside and at the top of softeners and filters to more uniformly distribute the incoming water over the resin or filter media bed. In small domestic units, this distributor also distributes the brine for regeneration.

A radioactive metallic element found naturally only in combination with other substances. Uranium 238 (U-238) is the most common form, but about 0.7 percent of natural uranium is present as U-235, which is the important fissionable component in work with atomic enemy. Uranium in natural water exists as anionic complexes UO2(CO3)22- and UO2(CO3)34-.

– A mechanical device which automatically vents a water line to the atmosphere when subject to a partial vacuum, thus preventing back siphonage.

1. (water treatment industry) Determination upon testing that a representative sample of a water treatment equipment model has met the requirements of a specified standard.
2. (pharmaceutical industry) The requirement of certain quality control testing and record keeping procedures to ensure compliance not only with a specific quality but also with a specific means to achieve and encore that quality.

A parasitic infectious microbe, composed almost entirely of protein and nucleic acids, which can cause disease(s) in humans. Viruses can reproduce only within living cells. They are 0.004 to 0.1 microns in size, and about 100 times smaller than bacteria.

The tendency of a fluid to resist flowing due to internal forces such as the attraction of the molecules for each other (cohesion) or the friction of the molecules during flow. Viscosity varies with water temperature.

VOCs :
volatile organic chemicals.

The volume occupied by the interstitial spaces between the particles of ion exchangers, filter media, or other granular materials in a bed or column. Often expressed as percent of the total volume occupied by the medium bed.

Capable of becoming vapor at relatively low temperatures.

Organic chemicals that turn into vapor at relatively low temperatures.

Volatile Organic Compound (VOC) :
Any organic compound which participates in atmospheric photochemical reactions except for those designated by the EPA Administrator as having negligible photochemical reactivity.

Waste Treatment Plant :
A facility containing a series of tanks, screens, filters and other processes by which pollutants are removed from water.

Waste Treatment Stream :
The continuous movement of waste from generator to treater and disposer.

Water that has been used. 1. (RO, ultrafiltration, electrodialysis) The stream of water (not product water) created as the result of processing water-the reject water or concentrate. 2. (ion exchange and filtration) The spent water used in the total backwash and/or regeneration cycle. 3. The used water and solids from a residence or a community (including used water from industrial processes) that flow to a septic system or a treatment plant. Storm water, surface water, and groundwater infiltration also may be included in the waste water that enters a waste water treatment plant. The term sewage usually refers to household wastes, but this word is being replaced by the term waste water.

An odorless, colorless, tasteless liquid which exists as ice in solid form (phase) and steam in vapor form (phase). It freezes at 32°F (0°C) and boils at 212°F (100°C). Water is a polar squid with high dielectric constant which accounts for its solvent power, it is called the universal solvent. It is a weak electrolyte; in pure water, only about two molecules in every 1,100,000,000 separate into H3O+ and OH- ions. Water is only slightly compressible. It is the liquid that descends from the clouds as rain and forms lakes, streams, and seas (oceans). Water is a major constituent of all living matter. Also referred to as H2O (dihydrogen oxide) and HOH (hydrogen hydroxide).

The amount of water, expressed as a percent of the wet weight of an ion exchanger, retained within the resin bead and on the surface of fully swollen and drained ion exchange media. Also called water regain.

A compound which, when introduced into water used for cleaning or washing, will counteract the effects of the hard water minerals (calcium and magnesium) and produce the effect of softened water. For example, detergent additives and polyphosphates.

A pressurized water treatment device in which hard water is passed through a bed of cation exchange media (either inorganic or synthetic organic) for the purpose of exchanging calcium and magnesium ions for sodium or potassium ions, thus producing a softened water which is more desirable for laundering, bathing, and dishwashing. This cation exchange process was originally called zeolite water softening or the Permutit Process. Most modern water softeners use a sulfonated bead form of styrene/divinylbenzene (DVB) cation resin.

Salt suitable for regenerating residential and commercial cation exchange water softeners. Most commonly used for this purpose is sodium chloride (NaCl) in crystal or pelletized form. Rock grade salt should be 96-99 percent NaCl; evaporated salt should be 99+ percent NaCl. Potassium chloride (KCl) may also be used for the regeneration cycle in the cation exchange process, thus minimizing the amount of sodium added to both the softened water and the spent regenerant water going to the drain.

The reduction/removal of calcium and magnesium ions, which are the principal cause of hardness In water. The cation exchange resin method is most commonly used for residential and commercial water treatment. In municipal and industrial water treatment, the process can be lime softening or lime-soda softening.

Any point-of-use or point-of-entry instrument or contrivance sold or offered for rental or lease for residential use, and designed to be added to the plumbing system, or used without being connected to the plumbing of a water supply intended for human consumption in order to improve the water supply by any means, including, but not limited to, filtration, distillation, adsorption, ion exchange, reverse osmosis, or other treatment.

Weak base anion exchanger.

Those cation exchange products with functional groups which, in the hydrogen form, are not capable of splitting neutral salts to form their corresponding free acids. Weak acid cation exchange resins have a much higher (three to four times higher) regeneration efficiency than their strong acid counterparts, but in the hydrogen form can only exchange cations that are associated with alkalinity. The cations associated with sulfates, chlorides, and nitrates, for example, cannot be removed with weak acid cation exchanger in the hydrogen form. Hydrogen form weak acid cation exchangers that have been neutralized with sodium hydroxide to the sodium form, however, can effectively remove both carbonate and noncarbonate water hardness cations; thus weak acid cation resins can be used to soften wafers that, because of high total dissolved solids, are not possible or practical to treat with strong acid cation resins.

Those anion exchange products with functional groups which are not capable of splitting neutral salts to form corresponding free bases, Weak base anion exchange resins have a much higher (three to four times higher) regeneration efficiency than their strong base counterparts, but can only exchange mineral acid anions such as sulfate, chloride, and nitrate. The anions associated with weak acids, such as carbonates, bicarbonates, silicates, and organic acids, for example, cannot be removed with weak base anion exchange. SEE ALSO free base form.

1. A dam-like 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.

Water for Injection.

World Health Organization.

l. The amount of product water produced by a water treatment process.
2. The quantity of water (expressed as a rate of flow-GPM, 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.

A term formerly used for the removal of calcium and magnesium hardness from water by base exchange using natural or synthetic zeolites. Since the introduction of synthetic organic cation exchange resins, the more correct term is cation exchange softening. Zeolite softening was also called base exchange.

Hydrated sodium alumina silicates, either naturally-occurring mined products or synthetic products, with ion exchange properties. Zeolites were formerly used extensively for residential and commercial water softening but have been largely replaced by synthetic organic cation resin ion exchangers of polystyrene divinylbenzene substrate. Modified zeolites such as manganese greensand and synthetic manganese zeolites are still used as catalyst/oxidizing filters for the removal of iron, hydrogen sulfide, and manganese.

A discharge limit applied to manufacturing and commercial establishments in which only normal human sanitary waste waters may be discharged to the municipal sewerage system. All other types of waste water, such as that water used in manufacturing processes, are not included in zero discharge water; but they must be recycled, and the resulting waste product from such water must be taken to an alternate and approved disposal facility.

water produced by the cation exchange process and measuring less than 1.0 grain per U.S. gallon (17. 1 ppm or 17. 1 mg/L) as calcium carbonate. zeta potential-The electrical potential which exists across the interface of all solids and liquids. The potential represents the difference in voltage between the surface of the diffuse layer surrounding a colloidal particle and the bulk liquid beyond. Also known as electrokinetic potential.

The comparatively dry soil or rock located between the ground surface and the top of the water table.

The layer in the ground in which all available interstitial voids (cracks, crevices, holes) are filled with water. The level of the top of this zone is the water table. SEE ALSO water table.

Small, usually microscopic animals (such as protozoans), found in lakes and reservoirs.

Zooplankton :
Tiny aquatic animals eaten by fish.

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