Water Filtration Glossary

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Absorption: The process of one substance actually penetrating into the structure of another substance. This is different from adsorption in which one substance adheres to the surface of another.

Activated alumina: A medium made by treating aluminum ore so that it becomes porous and highly adsorptive. Activated alumina will remove several contaminants including fluoride, arsenic and selenium. This medium requires periodic cleaning and appropriate reagent such as alum, acid and or/caustic.

Activated carbon: A water treatment medium, found in block, granulated, or powder form, which is produced by heating carbonaceous substances (bituminous coal or cellulose-based substance such as wood or coconut shell) in the absence of air, creating a highly porous adsorbent material.

Adsorption: The physical process occurring when liquids, gases or suspended matter adhere to the surface of, or in the pores of, an adsorbent medium. Adsorption is a physical process which occurs without chemical reaction.

Aeration: The process whereby water is brought into intimate contact with air by spraying or cascading, or air is brought into intimate contact with water by an air aspirator or by bubbling compressed air through the body of water. Both pressure (closed) aerators and open (gravity) aerators are used. Closed aeration is used chiefly for oxidation; open aeration for degassing.

Aesthetic contaminants: Characteristics of water which affects its taste, odor, color and appearance (and may affect the objects touched by the water) but which do not in themselves have any adverse health effects in otherwise potable water.

Alkali: A substance which creates a bitter taste and a slippery feel when dissolved in water and will turn litmus paper blue. An alkali has a pH greater than 7.0 and is the opposite of an acid. Highly alkaline waters tend to cause drying of the skin.



Back pressure: Pressure which creates resistance against a flow of water.

Backflow: The flow of water in a pipe or line in a direction opposite to the normal flow.

Bacteria: Single-celled organisms (single form = bacterium) which lack well-defined nuclear membranes and other specialized functional cell parts and reproduce by cell division or spores. Bacteria may be free-living organisms or parasites. Bacteria (along with fungi) are decomposers that break down the wastes and bodies of dead organisms making their components available for reuse. Bacteria cells range from about 1 - 10 micron in length and from .2 - 1.0 micron in width. They exist almost everywhere on earth. Despite their small size, the total weight of all bacteria in the world likely exceeds that of all other organisms combined. Some bacteria are helpful others are harmful.

Bacteriostatic: Having the ability to inhibit the growth of bacteria without destroying the bacteria. For example: silver-impregnated activated carbon will reduce bacterial colonization but not eliminate it.

Ballast: The power supply to activate and regulate voltage in an ultraviolet (UV) lamp.

Beaver fever: See Giardia lamblia.

Bleach: A strong oxidizing agent and disinfectant formulated to break down organic matter and destroy biological organisms.

Brine: A strong solution of salt(s) with total dissolved solid s concentrations. The waste solution in both automatic water softeners and reverse osmosis systems.



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

Carcinogens: A substance that can cause cancer.

Cartridge: Any removable pre-formed or pre-packaged component containing a filtering medium, ion exchanger, membrane or other treatment material which fits inside a housing to make up a cartridge filter.

Cartridge filter: A device often used for single faucet water treatment, made up of a housing and a removable cartridge (element). In residential filtering systems, disposable elements are used.

Channeling: The flow of water through a limited number of passages in a filter.

Charcoal: An adsorbent carbon product which has about one-third the surface area of activated carbon.

Check valve: A valve which will allow water to pass in one direction but will close and prevent flow (backflow) in the opposite direction.

Chloramines: Chemical complexes formed from the reaction between ammonia and chlorine being used to disinfect many municipal water supplies. Unlike chlorine, chloramines do not combine with organics in the water to form potentially dangerous trihalomethanes (THMs). Water containing chloramines may not be used for fish or for kidney dialysis applications.

Chlorine (Cl2): A gas widely used in the disinfection of water and as an oxidizing agent for organic matter. Chlorine is known to react with organic matter in the water to form trihalomethanes (THMs), a suspected carcinogen.

Clear water iron: See ferrous iron.

Coliform Bacteria: A particular group of bacteria primarily found in human and animal intestines and wastes. These bacteria are widely used as indicators organisms to show the presence of such wastes in water and the possible presence of pathogenic (disease producing) bacteria. Escherichia coli (E. coli) is one of the fecal coliform bacteria widely used for this purpose.

Color: A shade or tint which is imparted to water by substances which are in true solution and thus cannot be removed by mechanical filtration. Color is most commonly caused by dissolved organic matter, but it may be produced by dissolved mineral matter.

Contact time: The time the water is allowed to contain the disinfectant to assure potability. Contact time may also be called retention time.

Contaminant: Any undesirable physical, chemical or microbiological substance or matter in a given water source or supply. Anything in water which is not H2O may be considered a contaminant.

Cryptosporidium: A waterborne protozoan that forms cysts and causes acute gastrointestinal illness in humans, Cryptosporidium is commonly found in unfiltered surface water and is resistant to disinfectants such as chlorine and ultraviolet light, but it can be removed by filters that capture all particles of one micron and greater in size.

Cyst: A capsule or protective sac produced about themselves by many protozoans (as well as some bacteria and algae) as preparation for entering a resting or a specialized reproductive stage. Similar to spores, cysts tend to be more resistant to destruction by disinfectant. Fortunately, protozoan cysts are typically 2-50 microns in diameter and can be removed from water by fine filtration.



Desalination: The removal of dissolved inorganic solids (salts) from solution such as water to produce a liquid which is free of dissolved salts. Desalination is typically accomplished by distillation, reverse osmosis or electrodialysis.

Disinfection: The treatment of water to inactivate, destroy and /or remove pathogenic (disease producing) bacteria, viruses, cysts, and other microorganisms for the purpose of making the water microbiologically safe for human consumption. Disinfection may involve the use of disinfecting chemicals such as chlorine, iodine, ozone or peroxide; or it may involve physical processes such as distillation, microfiltration, ultrafiltration, boiling or ultraviolet radiation. Disinfection may also be called sterilization.

Dissolved solids also known as total dissolved solids: The weight of matter, including both organic and inorganic matter, in true solution in a stated volume of water. The amount of dissolved solids is usually determined by filtering water through a 0.45 pore-diameter micron filter and weighing the filtration residue left after the evaporation of the water at 180 degree C.

Distillation: The process of separating the water from the organic and inorganic contaminants through a combination of evaporation (or vaporization), cooling and condensation.

Distilled water: Water which has been cleansed by passing through one or more evaporation-condensation cycles until it contains a very low amount of dissolved solids (usually less than 5.0 ppm TDS).

Drain: A pipe or conduit which carries liquids by gravity to waste.

Drain line: A pipe line which is used to carry water from the water treatment system to a waste system.

Drinking water: A water treated or untreated which is intended for human use and consumption and considered to be free of harmful chemicals and disease-causing bacteria, cysts, viruses or other microorganisms.



Escherichia coli (E coli): One of the members of the coliform bacteria group normally found in human and animal intestines and indicative of fecal contamination when found in water. Determination of whether E. coli is present is often used to measure the microbiological safety of drinking water supplies.



Fecal matter: Matter (feces) containing or derived from animal or human bodily wastes that are discharged through the anus.

Fecal coliform: Coliform bacteria found in fecal matter.

Feed pressure: The pressure at which water is supplied to a water treatment device.

Feedwater: The water to be treated that is fed into a given water treatment system.

Ferric iron: Small solid iron particles containing trivalent iron, which are suspended in water and visible as "rusty water". Ferric iron can normally be removed by filtration. Also known as precipitated iron.

Ferrous iron: A divalent iron ion, usually as ferrous bicarbonate which when dissolved in water produces a clear solution. It is usually removed by cation exchange water softening. Also called clear water iron.

Filter: A device installed as part of the water system through which water flows for the purpose of removing turbidity, taste, color, iron or odor.

Filter media: The selected materials in a filter that form the barrier to the passage of filterable suspended solids or dissolved molecules. Filter media are used to remove undesirable materials, tastes and odors from a water supply.

Filtration: The process of separating solids from a liquid by means of a porous substance such as permeable fabric or membrane or layers of inert media.

Fines: Extremely small particles which are smaller than the specified size (in millimeters) for the medium.

Flow controller: An in-line device or orfice fitting which regulate and control flow of water.

Flow rate: The quantity of water which=h passes a given point in a specified unit of time, offen expressed in U.S. gpm (or L/min).

Fluoridation: The addition of fluoride compound to a potable water supply to produce the concentration desired (about one PPM) for the purpose of the reduction of dental caries (tooth decay).

Fluoride: A natural occurring constituent of some water supplies, an excess of which (over 2.0ppm) can cause discolored teeth.

Fouling (filtration): The accumulation of undesirable foreign matter in a filter causing clogging of pours coating of surfaces and inhibiting or limiting the proper operation of the treatment system.



Giardia: A common waterborne protozoan that forms cysts and is resistant to disinfectants such as chlorine and ultraviolet light. Giardia can be removed by filters that all particles of four microns and greater in size.

Giardia lamblia: A type of cyst found in the intestines of mammals and in water contaminated by mammal droppings. The giardia lamblia cyst, which is common and is frequently carried by water, is capable of causing a contagious waterborne disease characterized by acute diarrhea. This disease is referred to as beaver fever, because beaver droppings can contain giardia lamblia.

Groundwater: Water found beneath the surface of the ground. Ground water is primarily water which has seeped down from the surface by migrating through the interstitial spaces in soils and geologic formations.



Hardness: A common quality of water which contains dissolved compounds of calcium and magnesium and sometimes other divalent and trivalent metallic elements.

Health contaminant: Any substance or condition that may have any adverse effect on human health.



Installation: The connecting or setting up and start up operation of any water treatment system.

Ion exchange: A reversible chemical process in which ions from an insoluble permanent solid medium (the "ion exchanger" usually resin) are exchanged for ions in a solution or fluid mixture surrounding the insoluble medium.

Iron (Fe): A very common element often present in groundwater in amounts ranging from 0.01 to 10.0 ppm (mg/L) Iron can be found in three forms:

1. Soluble form as in ferrous bicarbonate.

2. Bound with a soluble organic compound

3. As suspended ferric iron particles

Iron bacteria: Bacteria which thrives on iron and are able to actually use ferrous iron (as found in water or steel pipes) in their metabolic processes, to incorporate ferric iron in their cell structure, and to deposit gelatinous ferric hydroxide iron compounds in their life processes.

Iron fouling: The accumulation of iron on or within an ion exchange resin bed or filter medium in such amounts that the capacity of the medium is reduced.







Lime (CaO): A calcined chemical material, calcium oxide.

Lime scale: Hard water scale formed in pipes and vessels (generally more severe on the hot water side) containing a high percentage of calcium carbonate (CaCO3) or magnesium carbonate MgCO3).

Loop: A plumbing connection used to bypass water around a location designed for installation of a water treatment system or used when the treatment system is out of service for any reason.



Magnesium (Mg): one of the elements that make up the earth's crust as part of many rock-forming minerals such as dolomite. Magnesium and calcium dissolved in water constitutes hardness. The presence of magnesium in water contributes to the formation of scale and insoluble soap which identify hard water.

Manganese (Mn): An element sometimes found dissolved in groundwater usually in combination with - but in lower concentrations than iron. Manganese is noticeable because in concentrations above 0.05mg/L it causes black staining of laundry and plumbing fixtures.

Mechanical filter: A pressure or gravity filter designed to physically separate and remove suspended solids from a liquid by mechanical (physical) means rather than by chemical means.

Media: A selected group of material used in filters and filter devices to form barriers to the passage of certain solids or molecules which are suspended or dissolved in water.

Membrane: A thin sheet or surface film, either natural or man-made of microporous structure that performs as an effluent filter of particles down to the size range of chemical molecules and ions. Such membranes are termed "semipermeable" because some substances will pass through but others will not.

Methane: A colorless, odorless, flammable gas consisting of the hydrocarbons (CH4) and resulting from the decay of vegetable matter or manure due to the action of anaerobic bacteria in swampy land, closed landfills or sewage disposal plants.

Micrograms per liter: Considered as equal to parts per billion (ppb). The common symbol for micrograms per liter is ug/L.

Micron: A metric unit of length equal to one millionth of a meter or one thousandth of a millimeter or about 0.00003937 inches. The symbol for micron is the Greek letter μ.

Micron rating: A measurement applied to filters or filter media to indicate the particle size at which suspended solids above that size will be removed. As used in the water treatment industry standards, this may be an absolute rating or a nominal rating.

Microorganism: A living organism invisible or barely visible to the naked eye and generally observed only through a microscope. Also called a microbe. Microorganisms are generally considered to include algae, bacteria, fungi, protozoa and viruses.

Mineral: An inorganic (non-living) substance which occurs naturally in the earth and has a composition that can be expressed as a chemical formula and a set of characteristics (crystalline structure, hardness etc.) common to all minerals. Examples of minerals are sulfur, salt and stone.

Mixed bed: The intermix of two or more filter exchange products in the same vessel during a service run.

Mixed media: The use of two or more media products in a single filtration loose media bed where the products are intermixed - rather than in stratisfied layers. For example the intermix use of calcite and magnesia in pH modification.

Municipal water: Water that has been processed at a central plant to make it potable or "safe to drink" and which is then distributed to homes and businesses via water mains. The term is a general one used to refer to the common source of water in most urban and suburban areas - as opposed to water obtained from separate proprietary sources such as private wells.



Nanofiltration: A membrane treatment process which falls between reverse osmosis and ultra filtration on the filtration/separation spectrum.

Naturally soft water: Ground surface, or rain water sufficiently free of calcium and magnesium salts so that no curd will form when soap is used and no calcium or magnesium based scale will form when the water is heated.

Neutral: (water chemistry) The midpoint (neutral) reading of 7.0 on the pH scale, indicating that the solution (water) producing the neutral reading will produce neither an acid nor alkaline reaction. A 7.0 reading on the pH scale means that there are an equal number of free hydrogen (acidic) ions and hydroxide (basic) ions.

Nitrate: A natural nitrogen compound sometimes found in well or surface waters. In high concentrations, nitrates can be harmful to young infants.

Nonpathogenic: Not disease producing.

Not detectable: A term used in reporting test results to mean that the substance being tested cannot be detected by the equipment or method being used for this particular test. This term implies that it is possible that trace amounts may be present in quantities to small to be detected by the test equipment or method.

NTU: nephelometric turbidity unit.



Operating pressure: The manufacture's specific range of pressure expressed in pounds per square inch (psi) within which a water processing device or water system is designed to function. A range of 30 to 100 psi is often indicated. Also called working pressure.

Operating temperature: The manufacturer's recommended feed water or inlet water temperature for a water treatment system.

Organic: Having the characteristics of or being derived from a living organism, plant and animal. Containing carbon (although a few very simple carbon compounds such as carbon oxides, the carbides, carbon disulfides and metallic carbonyls and carbonates are considered inorganic).

Organic matter: Substances consisting of or derived from plant or animal matter, as opposed to inorganic matter which is derived from rocks, ore and minerals. Organic matter is characterized by its carbon hydrogen structure.

Orfice: An opening, such as a hole or vent in something.

Oxidizing agent: A chemical substance that gains electron (is reduced) and brings about the oxidation of other substances in chemical oxidation and reduction (redox) reactions.

Ozonation: The process of feeding ozone into a water supply for the purpose of decolorization, deodorization, disinfectant or oxidation.

Ozone (03): A very strong oxidizing agent which is unstable and must be generated on site. Ozone is a highly reactive form of oxygen and can be produced by sending a high voltage electrical discharge through air or oxygen (such as occurs in a lightening storm). Ozone can also be produced by some types of ultra violet lamps. Ozone is an excellent oxidizing agent and bactericide.



Particle: A very tiny, separate subdivision matter.

Particle filtration: Filtration of particles in the size range of 2 microns or larger in diameter. Particle filtration is typically handled by cartridge filters and media filters.

Particle size: As used in water industry standards, this term refers to the size expressed in microns, of a particle suspended in water as determined by the smallest dimension.

Parts per billion (ppb): A measure proportion by weight which is equivalent to one unit weight of solute (dissolved substance) per billion unit weights of the solution.

Parts per million (ppm): A measure of proportion by weight which is equivalent to one unit of weight of solute (dissolved substance) per million weights of solution. Since one liter of water weighs one million milligrams, one ppm is equal to one milligram per liter (mg/L). PPM is the preferred unit of measure in water or wastewater analysis.

Pathogens: Any disease producing organism.

Pathogenic: Capable of causing disease.

pH (potential of hydrogen): A measure of the degree of the acidity or the alkalinity of a solution as measured on a scale ("pH scale") of 0 to 14. The midpoint of 7.0 on pH scale represents neutrality, that is, a neutral solution is neither acid nor alkaline. Numbers below 7.0 indicate acidity; numbers above 7.0 indicate alkalinity. It is important to understand that pH is a measure of intensity, not capacity. That is, pH indicates the intensity of alkalinity in the same way temperature tells how hot something is but not how much heat the substance carries.

Phosphate: A salt of phosphoric acid. In the water treatment industry, poly phosphates are used a sequestering agents to control iron and hardness, and as a coating agent to control corrosion by formation of a thin passivating film on metal surfaces.

POE: Point of entry.

Point of entry (POE) treatment: Full service water treatment at the inlet to an entire building or facility (outside faucets may be excepted from treatment).

Point of use (POU) treatment: Water treatment at a single outlet or limited number of water outlets in a building, but for less than the whole building or facility. POU treatment is often used to treat water for drinking and cooking only.

Polishing filter: A filter installed for use after the primary water treatment stage to remove any trace of undesirable matter or to polish the water.

Pollutant: A contaminant existing at a concentration high enough to endangered the environment or the public health or to be otherwise objectionable.

Potable (drinking) water: A water supply which meets U.S. EPA and/or state water quality standards and is considered safe and fit for human consumption.

POU: Point of use.

Pounds per square inch (psi): unit of measure for expressing pressure.

ppb: Parts per billion.

ppm: Parts per million.

Pretreatment: Any water treatment step performed prior to the primary treatment process, such as filtration prior to deionization.

Pressure drop: A decrease in the water pressure (in psi) which occurs as the water flows. The difference between the inlet and outlet water pressure during water flow through a water treatment device.

Process water: Water used in a manufacturing or treatment process or in the actual product manufacture.

Production rate: The amount (gallons or liters) of product water the system produces per minute or (especially for reverse osmosis) per 24 hour period.

Protozoa: Microscopic, usually single celled microorganisms which live in water and are relatively larger in comparison to other microbes. Protozoa are higher on the food chain than the bacteria that they eat. Many protozoa are parasitic.

psi: Pounds per square inch.

Pure water: This term has no real meaning unless the word "pure" is defined by some standard such as pharmaceutical grade water.

Purified water: A USP grade water produced from water meeting U.S. EPA standards for potable drinking water which has microbiological content under control and is free from foreign substances.



Quartz sleeve or quartz jacket: A clear, pure fused quartz tube used to protect the high intensity ultraviolet lamps in ultraviolet systems. It usually retards less than 10% of the ultraviolet radiation dose.



Radon (Rn): A colorless, odorless, short lived radioactive gas which is produced by decay of the uranium/radium series and is soluble in water. Radon is considered carcinogenic when inhaled by humans. Radon can be removed from water by aeration or activated carbon.

Raw water: Water, usually from wells or a surface source, which has had no previous treatment and is entering the water processing system or device. The water at the inlet side of any water treatment device.

Regeneration (ion exchange, softening): The use of a chemical solution (regenerant) to displace the contaminant ions deposited on the ion exchange resin during the service run and replace them with the kind of ions necessary to restore the capacity of the exchange medium for reuse.

Reject water: A term used in distillation, reverse osmosis and ultra filtration to describe that portion of the incoming feed water that has passed across the membrane but has not been converted to product water and is being sent to drain.

Rejection rate: In a reverse osmosis or ultra filtration system, rejection rate is the quantity of feed water that does not pass through the membrane expressed as a percent of the total quantity of incoming fed water.

Residual: The amount of a specific material which remains in the water after the water has been through water treatment step.

Resin: As used in the water processing industry, this term refers to ion exchange resin products which are usually specifically-manufactured organic polymer beads used in softening and other ion exchange processes to remove dissolved salts from water.

Retention: Contact time.

Reverse osmosis (RO): A water treatment process that removes undesirable materials from water by using pressure to force the water molecules through a semipermeable membrane. This process is called "reverse" osmosis because the pressure forces the water to flow in the reverse direction (from the concentrated solution to the dilute solution) to the flow direction (from the dilute to the concentrated) in the process of natural osmosis. RO removes ionized salts, colloids and organic molecules down to a molecular weight of 100.

Rust (ferric oxide): A reddish corrosion product occasionally found in water. Rust is formed as a result of electrochemical interaction between iron and atmospheric oxygen in the presence of moisture.



Safe water: see potable water..

Saline: Consisting of, or containing salt.

Salt water: The general term for all water over 1,000 ppm (mg/L) total dissolved solids.

Sand filter: The oldest and most basic filtration process, which generally uses two grades of sand (coarse and fine) for turbidity removal or as a first stage roughing filter or pre-filter in more complex processing systems.

Scale: A coating or precipitate deposited on surfaces such as kettles, water pipes or steam boilers that are in contact with hard water. Waters that contain carbonates or bicarbonates of calcium or magnesium are especially likely to cause scale when heated.

Septic: Producing or characterized by bacterial decomposition.

Service flow: The rate in U.S. gallons per minute (gpm) or liters per minute (L/min) at which a given water processing system can deliver product water. The rating may be intermittent peak flow or constant flow.

Shallow well: A well sunk in easily penetrated ground to a point which is below the water table but usually less than about 30 feet in depth.

Sodium: (Na+): A metallic element found abundantly in compounds in nature, but never existing alone.

Sodium chloride (NaCl): The chemical name for common table salt.

Soft water: Any water which normally contains less than 1.0 grain per gallon (17.1 mg/L or ppm) of total hardness expressed as calcium carbonate equivalent.

Softened water: Any water which has been processed in some manner to reduce the total hardness to 17.1 mg/L or ppm (1.0 grain per gallon) or less expressed as calcium carbonate equivalent.

Solids: The matter dissolved or suspended in water or wastewater.

Submicron filter: A cartridge type membrane filter used in fine particle separation applications to remove particles of less than one micron in size.

Sulfur (S): A yellowish solid chemical element. "Sulfur" is also often used to refer to sulfur water.

Sulfur bacteria: Thio-Bacillus.

Sulfur water: water containing objectionable amounts of hydrogen sulfide gas which causes an offensive "rotten egg" odor.

Surface water: All of the water (fresh and salt) on the surface of the earth including streams, lakes oceans, rivers, glaciers and some shallow wells that can be fed by surface runoff water.



Teflon: The trade name of a high temperature industrial plastic material used in cooking, finishes, bearings, lubricating, plumbing sealants, and a practically inert coating on metal and glass surfaces.

Total dissolved solids (TDS): The total weight of the solids that are dissolved in the water, given in ppm per unit volume of water. TDS is determined by filtering a given volume of water (usually through a 0.45 micron filter), evaporating it at a defined temperature (usually 103 - 105 degrees Celsius) and then weighing the residue.

Total hardness (TH): The total of the amounts of divalent metallic cations, principally calcium hardness and magnesium hardness, expressed in terms of calcium carbonate equivalent.

Toxic: Poisonous (to human beings); capable of producing disease or otherwise harmful to human health when taken into the body.

Trace element: An element essential to plant and/or animal nutrition in trace concentration of 1% of less.

Trihalomethanes (THMs): A group of organic chemicals, suspected of being carcinogenic, which are formed in water when chlorine being used as a disinfectant reacts with natural organic matter such as humic acids from decayed vegetation.

Turbidity: The amount of small particles of solid matter suspended in water as measured by the amount of scattering and absorption of light rays caused by the particles. Turbidity is measured in nephelometric turbidity units (NTU). Potable water should not exceed 0.5 NTU.



Ultrafiltration: A method of cross-flow filtration (similar to reverse osmosis but using lower pressure) which uses a membrane to separate small colloids and large molecules from water and other liquids.

Ultraviolet (UV): Pertaining to ultraviolet light.

Ultraviolet chamber: The area where the water is irradiated with ultraviolet rays.

Ultraviolet (UV) light: Radiation (light) having a wavelength shorter than 3900 angstroms, the wavelengths of visible light, and longer than 100 angstroms, the wavelength of x-rays.

Up flow: 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.



Virus: 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 micron in size, about 100 times smaller than bacteria.

VOCs: Volatile organic chemicals.

Volatile organic chemicals (VOCs): Synthetic organic chemicals that turn into vapor at relatively low temperatures.



Wastewater: Water that has been used. RO, ultrafiltration, and electrodialysis the stream of water (not product water) created as a result of processing water -the reject water or condensate.

Water (H2O): The liquid that descends from the clouds as rain and forms lakes, streams and seas (ocean). Water is a major constituent of all living matter. An odorless, colorless, tasteless liquid which exists as ice in solid form (phase) and steam in vapor form (phase). It freezes at 32 degrees F/0 degrees C and boils at 212 degrees F/100 degrees C.

Waterborne disease: A disease, caused by bacterium or organism able to live in water, which can be transmitted by water.

Water conditioning: The treatment or processing of water, by any means, to modify enhance or improve its quality to meet a specific water quality need desire or set of standards. Also called water treatment.

Water softening: The reduction /removal of calcium and magnesium ions, which are the principal cause of hardness in water.

Water source: The basic origin of a water, either a surface source (such as lake, river or reservoir) or a subsurface source (such as well). After treatment and pumping via pipelines, the treated and pumped water becomes a water supply.

Water table: The level of the top of the zone of groundwater saturation.









  • 1 US grain per gallon = 17.1 ppm
  • 1 milligrams per liter (mg/L) = 1.0ppm
  • 1 part per billion = 1 ug/l
  • 1 US gallon of water = 3.785 liters
  • 1 US gallon of water = 8.34 pounds (lb)
  • 1 cu. Ft. of water = 7.48 US gallons