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Absorption
To take up a substance into the physical structure of a liquid or solid (absorbent) by physical or chemical action, but without chemical reaction.
Acid rain
Rainfall above the natural pH range, caused by contact with atmospheric pollutants such as nitric and sulfuric oxides and carbon monoxide.
Acidity
Contents of hydrogen ions in water. High acidity causes corrosion and sour water taste.
Activated carbon
A porous material with large internal surface that absorbs different chemical compounds. Made of carbon that has been activated, it has high sorption qualities and is used to remove tastes, odor, chlorine, chloramines, and some organics from water.
Activation
The process by which carbon-containing materials undergo superheated steam-gas or chemical treatment to obtain adsorption qualities.
Adsorption
The process by which molecules, colloids, or particles adhere to the surfaces (of adsorbent) by physical action but without chemical reaction.
Alkalinity
Capacity for neutralizing acid, usually due to presence of bicarbonate or carbonate ions. Hydroxide, borate, silicate, or phosphate ions may contribute to alkalinity in treated waters.
Anion
See ion.
Asbestos
A fibrous silicate material, chiefly calcium magnesium silicate; a non-combastible, non-conducting, and chemical-resistant material. A known lung carcinogen.
Backwash
To reverse a solution's flow through a filtration system. Often used as a cleansing mechanism in sand and dual-media filters.
Bacteria
Any of a class of microscopic single-celled organisms, often aggregated into colonies or mobile by means of flagella. Widely dispersed in soil, water, organic matter, and the bodies of plants and animals. Either autotrophic (self-sustaining, self-generative), saprophytic (derives nutrition from non-living organic material already present in the environment), or parasitic (deriving nutrition from another living organism). Often symbiotic in man, but sometimes pathogenic.
Bactericide
Agent capable of destroying bacteria.
Bacteriostat
Substance that inhibits bacterial growth and metabolism.
Bicarbonates
See carbonates.
Binders
In reference to cartridge filters, chemicals used to hold, or "bind", short fibers together in a filter.
Carbonate hardness
The hardness in a water caused by carbonates and bicarbonates of calcium and magnesium. The amount of hardness equivalent to alkalinity formed and deposited when water is boiled.
Carbonates
Carbonic acid salts (chalk is calcium carbonate).
Bicarbonates
Carbonic acid salts, but not fully substituted.
Carbonic acid
Formed by interaction of carbon dioxide and water. Unstable and disintegrates easily. Carbonic acid salts are stable (ex. soda is sodium bicarbonate).
Carcinogen
A substance or agent producing or inciting cancer.
Cartridge
A filter device, usually disposable, filtering in the range of 0.1 micron to 100 microns, and usually 2 inches to 4 inches (51 to 102 mm) in diameter and 6 inches to 60 inches (152 to 1524 mm) in length.
Caustic soda
Sodium hydroxide (NaOH), commonly known as lye. A commonly used chemical in water treatment.
Cation
See ion.
Chelate complex
A type of complex compounds of metals with specific organic compounds (chelatable ligands) that is characterized by a very high strength.
Chelating agents
A molecule, usually organic, which is soluble in water and undergoes reaction with metal ions to hold them in solution. A number of naturally-occurring organic materials in water have chelating ability, such as humic acid and lignin. Due to their chelating abilities, some organic materials interfere with water softening processes.
Chloramine
A combination of free chlorine and ammonia gas (or other nitrogen compounds) which retains its bactericidal qualities for a longer time than does free chlorine.
Chlorination
A method of water disinfection by feeding of small amounts of free chlorine, usually 0.2 to 2.0 ppm, to kill bacteria in a water supply.
Chlorine
Chemical used for its qualities as a bleaching or oxidizing agent and disinfectant in water purification. It is a heavy greenish-yellow gas with sharp odor. Dissolved in water it forms active (or free) chlorine that is highly chemically active. Anion of chlorine (fixed chlorine) is not harmful.
Chloroform
See THM.
Chlororganic compounds
Chlorine-containing derivatives of hydrocarbon (saturated, unsaturated, alicyclic, aromatic) and various classes of organic compounds. Some of the chlororganic compounds are: trichloromethane (chloroform), dichlorethane, hexaclorane, chlorobenzene, chlorophenol.
Chlororganic matter
Organic substances containing atoms of chlorine. Dangerous for humans; can accumulate in a human body.
Coagulant
Chemical added in water and wastewater applications to cause the formation of flocks that absorb, entrap, or otherwise bring together suspended matter that is so fine, it is defined as colloidal. Compounds of iron and aluminum are generally used to form flocks to allow removal of turbidity, bacteria, color, and other finely divided matter from water and waste water.
Colloid
A substance of very fine particle size, typically between 0.1 and 0.001 microns in diameter suspended in liquid or dispersed in gas. Has a very extended surface. Typically removable only by reverse osmosis, distillation, or ultrafiltration.
Colloidal iron
Iron compounds (hydroxide, oxyhydroxide, and others) in a colloidal state.
Compound
Composed of the union of separate elements, ingredients, or parts.
Concentration
The amount of material contained in a unit volume of fluid; the process of increasing the dissolved material per unit volume.
Contaminant
A source of contamination, an impurity. Any substance in water which is not H2O.
Deionization (DI)
Specially manufactured ion exchange resins which remove ionized salts from water. Can theoretically remove 100% of salts. Deionization typically does not remove organics, virus or bacteria, except through specially made strong base anion resins which will remove gram negative bacteria.
Demineralization
The process of removing minerals from water, usually through deionization, reverse osmosis, or distillation.
Desorption
The process opposite to sorption.
Developed surface
Surface of a solid characterized by the extended surface area (about 1-1500 square meters per gram). Powders with small linear size, such as particles or porous solid substances (activated carbons, activated carbon fibers) have especially developed surface area. Effectiveness of an adsorbent is defined mainly by how developed its surface is.
Disinfection
To kill pathogenic organisms in a water supply or distribution system by means of heat, chemicals, or UV light.
Dissolved solids
The residual material remaining after filtering the suspended material from water and evaporating the solution to a dry state.
Distillate
The product water from distillation formed by condensing vapors.
Distillation
The process of condensing steam from boiling water on a cool surface. Most contaminants do not vaporize and therefore do not pass to the distillate. Removes nearly 100% of all impurities, but the process is expensive. Distillation can be used to separate liquid from dissolved hard materials as well as from another liquid that has different boiling point.
Endotoxin
A heat-resistant pyrogen, specifically a lipopolysacharide found in the cell walls of viable and non-viable bacteria.
EPA
Environmental Protection Agency (USA) - an organization that has set the potable water standards.
Evaporation
Process where water passes from a liquid to a vapor state.
Exhaustion
In water softening or ion exchange, the point where the resin can no longer exchange for additional ions.
FDA
Food and Drug Administration (USA).
Feed
The input solution to a treatment/purification system, including the raw water supply prior to any treatment.
Filter cake
The accumulated particles on a filter surface, usually from a slurry mixture.
Filtrate
The portion of the feed stream which has passed through a filter.
Floc
Coagulated groupings of formerly suspended particles which then settle by gravity.
Flocculant
Chemical(s) which, when added to water, cause suspended particles to coagulate into larger groupings (flocs) which then settle by gravity.
Flocculation
The process of agglomerating particles into larger groupings called flocks, which then settle by gravity.
Freezing
Water filtration by way of partial freezing. Based on the difference in freezing point of pure water and "brine" that contains contaminants.
Glassing
A form for silica scaling at high temperatures, usually in high-pressure boilers or stills.
Gpd
Gallons per day.
Grains per gallon (gpg)
A unit of concentration equal to 17.1 milligrams per liter.
GRAS
Material "generally regarded as safe", as listed by the FDA.
Hardness (hard water)
The concentration of calcium and magnesium salts in water. Hardness varies not only in different natural sources of water, but even in the same source of water but at different times of year. Water hardness less than 4 mmole per liter is called soft, from 4 to 8 mmole per liter is average, from 8 to 12 mmole per liter is hard, and over 12 mmoles per liter is very hard. When heated, hard water forms precipitation of calcium carbonate that has negative effect on heating appliances, kitchen and plumbing equipment. Hard water doesn't readily form foam and irritates skin.
Heavy metals
Metals having a high density or specific gravity of approximately 5.0 or higher. A generic term used to describe contaminants such as cadmium, copper, lead, arsenic, chromium, mercury, selenium and zinc. Most are toxic to humans in low concentration. These metals can be present in water as cations of soluble salts and their presence is usually due to industrial pollution.
Herbicides
Organic compounds used in agriculture to control weeds. They can leach into drinking water supply.
Heterogeneous system
A system that contains several phases (solid - liquid, liquid - gas).
Humic acid
A water-soluble organic compound composed of decayed vegetable matter (such as peat, brown coal, bituminous coal) which is leached into a water source by runoff. Present in most surface waters. Higher concentrations cause a brownish tint and odor, speed up corrosion of metals, negatively affect development of water microorganisms, reduce oxygen content, and affect ion and phase equilibrium. Difficult to remove except by ultrafiltration or reverse osmosis.
Hydrocarbon
An organic compound containing only carbon and hydrogen and often occurring in petroleum, natural gas, coal, and bitumens. Most successfully removed from water by coalescing (large volumes) or activated carbon (small volumes).
Hydrogen sulfide
A toxic gas (H2S) that is detectable by a strong "rotten egg" odor. A common by-product of anaerobic bacteria.
Hydroxide
A product of interaction between metal and water.
Ion
An atom or molecule which has lost or gained one or more electrons, thereby acquiring a net electronic charge.
Cation
Positively chargeed ion in an aqueous solution.
Anion
Negatively charged ion in an aqueous solution.
Ion exchange
A specific case of sorption of charged elements (ions) in which ions are preferentially adsorbed from a solution for equivalently charged ions attached to small solid structures (resin).
Ion exchange membrane
Highly engineered polymer film containing controlled distribution of pores capable of passing ions of a certain type. Used as a separation mechanism in reverse osmosis.
mg/L
Milligrams of an element per liter of water.
Microelements
Small quantities of compounds in water that can be useful as well as harmful. Measured in micrograms (1 microgram = 0.001 milligram).
Microfiltration (MF)
Filtration designed to remove particles and bacteria in the range of 0.1 to 2 or 3 microns in diameter.
Micron
A metric unit of measurement equivalent to 10-6 meters, 10-4 centimeters, 0.001 millimeters. Symbol is µ.
Microorganisms
Smallest organisms that can be seen only under a microscope. Mostly single-celled organisms of great veriety. Play important role in the lifecycle of matter in nature. Used in industry and agriculture. Some are pathogens.
Module
A membrane element combined with the membrane element housing.
Mole
Quantity of a substance expressed in grams that numerically coincide with molecular weight of the substance expressed in atomic units. Mmole = 0.001 mole.
Molecular weight (MW)
The sum of atomic weights of the constituents which make up a molecule. Often used to indicate size when referring to ultrafiltration of saccharide compounds.
Molecule
The smallest physical unit of a substance, composed of one or more atoms, that retains the properties of the substance.
Nitrates
Nitric acid salts that are traditionally used as a nitrogen fertilizer. Their water content is usually less than 10 mg/L. Agricultural runoffs may cause increase in concentration of nitrates in water. At 50 mg/L nitrates can be dangerous for human health, especially for small children.
Nitrites
Nitric acid salts. Poisonous.
Nominal
With regard to the micron rating of cartridge filters, refers to an approximate size particle, the vast majority of which will not pass through the filter. A small amount of particles this size or larger may pass through the filter.
Non-carbonate hardness
Hardness caused by chlorides, sulfates, and nitrates of calcium and magnesium. Evaporation of waters containing these ions makes the water highly corrosive.
Osmosis
The spontaneous flow of water from a less concentrated solution to a more concentrated solution through a semipermeable membrane until energy equilibrium is achieved.
Oxidize
To increase a molecule or ion in positive valence, losing electrons to an oxidizing agent.
Oxidizing filters
Filters that use a catalytic media such as manganous oxides to oxidize iron and mnganese and then filters the impurities from the water after they have been oxidized.
Ozonator
A device which generates ozone by passing a high-voltage current through a chamber containing air or oxygen. Used as a disinfection system.
Ozone (O3)
An unstable, highly reactive form of the oxygen formed by natural lightning or by passing a high-voltage electric charge through air. An excellent oxidizing agent and bactericide.
Particle filtration (PF)
Filtration rated in the range of 5 to 75 microns. Typically handled by cartridge filters.
Particulate
Minute, separate pieces of matter.
Pathogen
A bacterium or virus that causes an infectious disease.
Permeable
Allowing some material to pass through.
Pesticides
Chemical substances (organic compounds) used in agriculture as control agents against undesired microorganisms, animals and plants that are considered detrimental from a financial or health protection points of view (bactericides, insecticides, defoliants). These compounds can leach into water sources. Many are suspected carcinogens.
Petroleum products
Products of oil refinement, organic substances such as gasoline and fuel oil. Considerably decrease water quality (taste and smell), even in small quantities.
pH
An expression of hydrogen ion concentration; specifically, the negative logarithm of the hydrogen ion concentration. The range is from 0 to 14, with 7 as neutral, 0 to 7 as acid and 7 to 14 as alkaline (base).
Phase
A state of matter, either solid, gaseous, or liquid.
Phosphates
inorganic salts of orthophosphoric acid. Used in agriculture as phosphate fertilizers.
Polymers
A chemical compound with many repeating structural units produced by uniting many primary units, called monomers.
Pore
An opening in a membrane or filter matrix.
Porous
The ability of certain substances to pass fluids due to an open physical structure.
ppb
Parts per billion, commonly considered equivalent to micrograms per liter (µg/L).
ppm
Parts per million, commonly considered equivalent to milligrams per liter (mg/L).
ppt
Parts per trillion, commonly considered equivalent to nanograms per liter (ng/L).
Precipitate
An insoluble product of a chemical reaction of soluble compounds in water.
Precipitation
The process of producing an insoluble reaction product from an aqueous chemical reaction, usually a crystalline compound that grows in size to be settleable.
Precursors
Compounds such as humic acid which may lead to the creation of other compounds, such as THM.
psi
Pounds per square inch (pressure).
Pyrogen
Any substance capable of producing a fever in mammals. Often an organic substance shed by bacteria during cell growth. Chemically and physically stable, they are not necessarily destroyed by conditions that kill bacteria.
Pyrolysis
The process of high-temperature decomposition (usually in inert atmosphere) of organic polymers in order to obtain carbon materials that are then activated.
Reagent
Source material that participates in a chemical reaction.
Regeneration
In ion exchange systems, the process of using either an acid alkali, or salt solution to remove the accumulated cations or ions. The cation exchange resins take on hydrogen ions and the anion exchange resins take on hydroxide ions to restore themselves to the original hydrogen or hydroxide form when using strong acid and strong alkali solutions for the process.
Residual chlorine
Excess chlorine added to the water after it has been through the filtration works to maintain the bacteria "kill potential".
Resin
Specially manufactured polymer beads used in the ion exchange process to remove dissolved salts from water.
Reverse osmosis (RO)
The separation of one component of a solution from another component by slowly flowing the feed stream under pressure across a semipermiable membrane. RO removes ionized salts, colloids, and organics down to 150 molecular weight. May also be called hyperfiltration.
Rust
Household name for a mixture of compounds that consist of oxides and hydroxides of iron.
Saturation
The point at which a solution contains enough of a dissolved solid, liquid, or gas so that no more will dissolve into the solution at a given temperature and pressure.
Scaling
The build-up of precipitated salts on a surface, such as pipes, tanks, or boiler condensate tubes.
Selectivity
Quality of a sorbent to discriminate between molecules and retain some substances while allowing others to pass through.
Semipermeable membrane
A membrane which allows a solvent such as water to pass through, while rejecting certain dissolved or colloidal substances.
Solutes
Matter dissolved in a solvent.
Sorption
Absorption of gases, vapors, and dissolved substances by a solid material or a liquid. Sorbent is the substance that sorbs.
Sorption capacity
Quantity of a substance that can be absorbed by the mass unit of a sorbent.
Sterilization
Processing under high temperature in order to kill bacteria, viruses, parasites, and other living microorganisms.
Suspended solids (SS)
Solid organic and inorganic particles in a solution that are held in suspension.
Suspension
A solid dispersed in a liquid usually in particles of larger than colloidal size.
THM (e.g. Chloroform)
Trihalogenated Methane Compounds - Formed by contact between free chlorine and certain organics to form materials similar to certain organic solvents. Always present in chlorinated water. Considered a carcinogen.
TOC
Total Organic Carbon - The amount of carbon bound in organic compounds in a water sample as determined by a standard laboratory test.
TDS
Total Dissolved Solids - The sum of total dissolved solids and total suspended solids.
TSS
Total Suspended Solids - The residual matter which can be removed from a solution by filtration.
Turbidity
A suspension of fine particles (mineral and organic) in water that cause cloudiness and will not readily settle due to small particle size.
Vaporize
To convert a liquid into a vapor.
Virus
Any of a large group of submicroscopic infective agents capable of growth and multiplication only in living cells of a host. Viruses use biosynthesis and power mechanisms of the cells of a host and therefore virus is a parasite on the genetic level. There are about 500 viruses that inhabit warm-blooded vertebrates.
VOC
Volatile organic compound - synthetic organic compounds which easily volatize. Usually, industrial solvents. Many are suspected carcinogens.
Volatile
Readily passing off by evaporation.
WHO
World Health Organization - (part of the United Nations) which has set the standards for potable water.
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