Glossary

Absolute Filter Rating

Filter rating meaning that 99.9 percent (or essentially all) of the particles larger than a specified micron rating will be trapped on or within the filter. >>

Activated Carbon     

A water treatment medium made in block, granular or powder form.  It is commonly used for the removal of chlorine and other organic chemicals from water.  Activated carbon block filters have greater absorbtion capacities than granular or powdered carbon.

 

Algae

Single-celled or simple multicelled organisms, commonly found in surface water, which produce their own food through photosynthesis.  Excessive algae growth may cause the water to have undesirable odors or tastes, and decay of algae can deplete the oxygen in the water. >>

Ambient temperature

Temperature of the surrounding air (or other medium).>>

 

Bacteria

Ballast

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

Black Water

Bore Water

Water accumulated in aquifers below the earth's surface but available for farm use by sinking a bore pipe into the aquifer.  May discharge to the surface (artesian bore) or need to be pumped to the surface (subartesian bore).

 

Bottled Water Plant

Any place or establishment in which bottled water is prepared for sale.>> 

Breakthrough     

Term associated with the expiration of activated carbon media where the absorption capacity of the carbon has expired and the contaminants may bleed back into the water supply. Similarly associated with sediment filters where the water pressure may either bend or flex a heavily laden filter cartridge or the filter media may be breached releasing the suspended contaminants into the water supply.

Bridging

Bridging occurs in water softening when salt sticks together to form one large solid mass of pellets, or by the salt caking in a dry-salt brine tank which causes failure of the liquid or brine beneath the dry salt to become saturated. The result of bridging is insufficient salt in the regenerant solution to properly regenerate the cation resin.>>

Brine

A strong solution of salt(s), usually sodium chloride and other salts too, with total dissolved solids conentrations in the range of 40,000 to 300,000 or more milligrams per litre.>>

 

Calcium   

Calcium, the most abundant mineral in the human body, has several important functions. More than 99% of total body calcium is stored in the bones and teeth where it functions to support their structure. The remaining 1% is found throughout the body in blood, muscle, and the fluid between cells. Calcium is needed for muscle contraction, blood vessel contraction and expansion, the secretion of hormones and enzymes, and sending messages through the nervous system. A constant level of calcium is maintained in body fluid and tissues so that these vital body processes function efficiently.

Carcinogen

Any substance which tends to produce cancer in an organism.>>

Cartridge

Any removable preformed or prepackaged component containing a filtering medium, ion exchanger, membrane, or other treatment material which fits inside a housing to make up a cartridge filter.>>

Chlorination   

The treatment process in which chlorine gas or a chlorine solution is added to water for disinfection and control of microorganisms. Chlorination is also used in the oxidation of dissolved iron, manganese, and hydrogen sufide impurities.>>

 

Chlorine

Chlorine /klor-een/ n. a poisonous green gaseous chemical element. Chlorine is added to water for disinfection and control of bacteria.

Concentrate recycle (reverse osmosis and electrodialysis)

A technique for increasing the amount of product water by recycling a fraction of the concentrate stream back through the membrane or membrane stack.>>

 

Contaminant

Any undesirable physical, chemical, or microbiological substance or matter in a given water source or supply.  Anything in water which is not H ₂ O may be considered a contaminant.>>

 

Cryptosporidium    

Crytosporidium is a protozoan that can cause gastro-intestinal illness with diarrhea in humans.

 

Cyst

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

DI - Deionised Resin filtration   

Deionised resin consisting of cation and anion resin beads for the removal of ionised minerals and salts from water.

Deionization

The removal of all ionized minerals and salts (both organic and inorganic) from a solution by a two-phase ion exchange procedure.>>

Desalination

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

E. coli

Escherichia coli or E. coli is found in the intestines of animals, and does not originate from environmental sources.  For this reason, E. coli is a highly specific indicator of faecal contamination in drinking water.

Effluent

The outflow from any water processing system or device. Sometimes used to mean the product water or treated water emerging from a given device or system.>>

e-Waste

Electronic waste - such as power control boards (PCB's) all electronic components of appliances.  e-Waste in landfill leaches cadmium, lead and polyvinyl chlorides into soil and water.

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.>>

Filter

A device installed as part of the water system through which water flows for the purpose of removing turbidity, taste, colour, iron, or odour. Filters can loose media beds in tanks or cartridge-type devices (either packed-medium cartridges or membrane cartridges) and filter media may be used for mechanical, adsorptive, neutralizing, or catalyst/oxidation filtration processes.>>

Filtration

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

Flagellates

Microorganisms that move by the action of tail-like projections.>>

Floc (water treatment)

A very fine, fluffy-type mass formed by the coming together of a number of fine suspensed particles. A floc can occur naturally, but most frequently it is induced by the addition of a coagulant/flocculent to raw water which contains undesirable tubidity or colour.>>

Floc (waste water treatment)

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

Flocculation

The process of brining together destabilized or coagulated particules to form larges masses or flocs which can be settled and/or filtered out of the water being treated.>>

Flocculents

Materials which, when added to water, cause suspended particles to coagulate into larger groupings and form gelatinous clouds of precipitate which enclose additional fine particles of suspended dirt.  The precipitate and the dirt can then be settled or filtered out of the water being treated.>>

Flow rate

The quantity of water or regenerant which passes a given point in a specified unit of time, often expressed in U.S. gpm (or L/min). In filters, flow rate is usually measured in gmp/sq.ft. of bed area. In ion exchangers, it is expressed in gpm/cu.ft. of resin. Flow rate is a critical design parameter by which the effectiveness of the water treatment unit is measured.>>

Fluoridation

The addition of a chemical to increase the concentration of fluoride ions in drinking water to a predetermined optimum limit to reduce the incidence (number) of dental caries (tooth decay) in children.  Defluoridation is the removal of excess fluoride in drinking water to prevent the mottling (brown stains) of teeth.>>

 

Fluoride     

Fluoride - A naturally occuring or introduced substance in water supplies for the development of children's teeth and the reduction of cavities. May cause discoloured teeth and skeletal fluorosis bone disease if ingested above certain amounts.

   

Giardia  

Giardia lamblia (synonymous with Lamblia intestinalis and Guardia duodenalis) is a flagellated protozoan parasite that colonises and reproduces in the small intentine, causing giardiasis.

Grey Water

Greywater, also known as sullage, is non-industrial wastewater generated from domestic processes such as dish washing, laundry and bathing. Greywater comprises 50-80% of residential wastewater. Greywater is distinct from blackwater in the amount and composition  of its chemical and biological contaminants (from faeces or toxic chemicals). Greywater gets its name from its cloudy appearance and from its status as being neither fresh (white water from groundwater or potable water), not heavily polluted (blackwater).

Grey Water Treatment System

A system that collects, treats and disinfects greywater generated from a household. These systems usually include primary treatment in the form of a grease trap and coarse filter and a secondary aerobic treatment and disinfection.  The input to the system needs to be permanently connected to the dwelling and the output needs to be plumbed back in to the house and/or to a sub-surface irrigation system.

H₂O

The chemical formula for water (dihydrogen oxide).>>

Halogens

A family group of elements, including bromine, chlorine, fluorine, astatine and iodine, which are extremely active chemically. These elements exist in the free state normally as diatomic molecules, but more commonly are found as the ionic component in compounds with various other elements.>>

 

Hardness

A common quality of water which contains dissolved compounds of calcium and magnesium and, sometimes, other divalent and trivalent metallic elements. The term hardness was originally applied to waters that were hard to wash in, referring to the soap wasting properties of hard water. Hardness prevents soap from lathering by causing the development of an insoluble curdy precipitate in the water; hardness typically causes the buildup of hardness scale (such as seen in cooking pans or kettles).  Dissolved calcium and magnesium salts are primarily responsible for most scaling in pipes and water heaters and cause numerous problems in laundry, kitchen, and bath. Hardness is usually expressed in grains per gallon (or ppm) as calcium carbonate equivalent.>>

Water is generally regarded as being hard when the total hardness is more than 86 parts per million.

Helminths

Other causes of waterborne disease in humans include helminths. These worms or worm-like parasites infect the intestine and include roundworms, tapeworms and flatworms. The worms in humans that origionate from helminth eggs are relatively easy to cure and present a problem only in developing countries where malnutrition is a problem.

Hydration

The chemical combination of water into another substance.>>

Hydraulic

Referring to water or other fluids in motion.>>

In-Line Filtration

The addition of chemical coagulants directly to the filter inlet pipe. The chemicals are mixed by the flowing water.  Flocculation and sedimentation facilities are eliminated. This pretreatment method is commonly used in pressure filter installation.>>  In-line filtration is used on appliances such as fridges and coffee machines.

Installation

The connecting or setting up and startup operations of any water treatment system.  The term also refers to complete assembly of piping, valves, drain line, pumps, meters, and controls by which the equipment is connected into the water supply system.>>

 

Iron

A very common element often present in groundwater in amounts ranging from 0.01 to 10.0 ppm (mg/L). Iron may be found in three forms: 1) in soluble form such as in ferrous bicarbonate; 2) bound with a soluble organic compound; 3) as suspended ferric iron particles.  Iron above 0.3 mg/L is objectionable in water because of staining of laundry and plumbing fixtures caused by the oxidation and precipitation of ferric hydroxide and/or ferric oxide (ferric iron) into small solid iron particles.  Iron can also give a metallic or distorted flavor to beverages. Iron also occurs in water as ferric iron.>>

Iron Bacteria

Bacteria which thrive on iron and are able to actually use ferrous iron (as found in water or steel pipes) in the metabolic processes, to incorporate ferric iron in their cell structure, and to deposit gelatinous ferric hydroxide iron compounds in their life processes. Iron bacteria are found in several varieties including Crenothrix, Lepothrix, and Gallionella.  Iron bacteria can cause staining, plugging, and taste and odour problems in a water system.

 

Lead

Lead poisoning is a medical condition caused by increased levels of the metal lead in the blood.  Lead may cause irreversible neurological damage as well as renal disease, cardiovascular effects, and reproductive toxity.

Legionella

Over 26 species of bacteria, such as Legionella pneumohila, which can cause the pneumonia-like illness called "Legionnaires' Disease" (after the American Legion convention at which the disease first drew attention). These bacteria are known to thrive at about 100 ^o F and are believed to live in infected humidifiers, cooling tower water, and shower rooms.  Infection is by inhalation.>>

Lime (CaO)

A calcined chemical material, calcium oxide. Lime is used in lime and soda ash water treatment, but must first be slaked to calcium hydroxide. [Ca(OH) ₂ ].>>

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 (CaCO ₃ ) or magnesium carbonate (MgCO ₃ ).>>

 

Magnesium   

Magnesium is one of the most important minerals in the body. It is vital for over 300 enzyme systems in the body - more than Iron and Zinc combined.

Manganese (Mn)

An element found dissolved in groundwater, usually in combination with - but in lower concentrations than - iron.  Manganese is noticeable cause in concentrations above 0.05 mg/L it causes black staining of laundry and plumbing fixtures. Important ores of manganese are pyrolusite, manganite, psilomelane, and rhodochrosite.>>

Media

A selected group of materials used in filters and filter devices to form barriers to the passage of certain solids or molecules which are suspended or dissolved in water. It is also common to use the term media to refer to ion exchange resin products. Media is the plural form of medium and refers to more than one type of barrier material.>>

Membrane Filtration

A laboratory analytical technique for the quantitative and qualitative analysis of bacterial or particulate matter in a water sample. Upon filtering through a membrane of specified pore size (e.g. 0.45 micron), bacteria and particles of larger size are separated from the water sample and are retained on the filter. Then by incubation with a suitable nutrient and temperature, the captured bacteria will grow to visible colonies than an be counted;  or by careful weighing, the amount of suspended particulate solids can be determined in the water sample.>>

mg/L

Milligrams per litre.

Microfiltration

The separation or removal from a liquid of particulates and microorganisms in the size range of 0.1 to 2 microns in diameter.>>

 

Micron

A metric unit of length equal to one millionith of a meter or one thousandth of a millimeter or about 0.00003937 inches.>>

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 observable only through a microscope.  Also called a microbe. Microorganisms are generally considered to include algae, bacteria, fungi, protozoa, and viruses.>>

Neutralizer

An alkaline substance such as calcium carbonate (calcite) or magnesium oxide (magnesia) used to neutralize acidic waters or an acidic substance such as acetic acid or dilute hydrochloric acid used to neutralize alkaline waters. The term "neutralizer" is commonly used to refer to calcite or magnesia acid-neutralizing filters used to neutralize acidity and/or reduce free carbon dioxide in water and thereby raise the H of acidic water.>>

Nitrate

A natural compound (NO _3^- ) sometimes found in well or surface waters. In high concentrations, nitrates can be harmful to young infants or young livestock.>>

Nominal filter rating

Filter rating indicating the approximate size particle, the majority of which will not pass through the filter. It is generally interpreted as meaning that 85 percent of the particles of the size equal to the nominal filter rating will be retained by the filter. Standard test procedures, such as those listed in the ANSI/NSF standards for particulate and cysts reduction by drinking water treatment units, should be used to determine and substantiate nominal filter ratings.>>

Nutrient

Any substance that is assimilated (taken in) on organisms and promotes growth. For example, carbon dioxide, nitrogen, phosphorous, potassium, and numerous mineral elements are essential nutrients which promote the growth of plants. Water and oxygen are also included in this definition.>>

Operating cycle (filtration)

The complete filtration process consisting of filter service, backwash and rinse, and return to service.>>

Operating cycle (ion exchange)

The cycle of service run, backwash and regeneration, slow rinse, fast rinse, and return to service.>>

Osmosis

The natural tendency for water to spontaneously pass through a semipermeable membrane separating two solutions of different concentrations (strengths). The water will naturally pass from the weaker (less concentrated) solution containing fewer particles of dissolved substance to the stronger (more concentrated) solution containing more particles of a dissolved substance.  Thus, natural osmosis causes the stronger solution to become more diluted and tends to equalize the strength of the solutions on both sides of the membrane.  See also osmotic pressure;  reverse osmosis.>>

Osmotic Pressure

The pressure and potential energy difference which exists between two solutions on either side of a semipermeable membrane because of the tendency of water to flow in osmosis.  Every 100 ppm (mg/L) of TDS generates about one pound per square inch of osmotic pressure.  This osmotic pressure must first be overcome by water pressure for a reverse osmosis membrane to become effective.>>

Ozone (O₃)

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 lightning storm). Some degree of ozone can also be produced by certain types of ultra-violet lamps.  Ozone is an excellent oxidizing agent and bactericide.>>

Particle Count

The results of a microscopic examination of treated water with a special "particle counter" which classifies suspended particles by number and size.>>

Particle Filtration

Filtration of particles in the size range of two 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.>>

Particulate

A very small solid suspended in water which can vary widely in size, shape, density, and electrical charge.  Colloidal and dispersed particulates are artificially gathered together by the processes of coagulation and flocculation.>>

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 litre of water weights one million milligrams, one ppm is equal to one milligram per litre (mg/L). Milligram per litre is the preferred unit of measure in water or waste water analysis.>>

Pathogenic

Capable of causing disease.>>

Pathogens

Waterborne diseases - Microorganisms that are capable of causing disease are called pathogens. The pathogens of concern in water supplies are mainly those that are found in the excrement (faeces) of humans or animals. If these microorganisms are present in water, and are not removed by water treatment or disinfection, then consumers may suffer infections.

Percent Recovery

The percentage of the feedwater which becomes product water.  Determined by the number of gallons (or litres) of product water divided by the total gallons (or litres) of feedwater and multiplied by 100.  The percent recovery is called recovery rate in reverse osmosis and ultrafiltration.>>

Percent Rejection (reverse osmosis/ultrafiltration)

The percentage of TDS in the feedwater that is prevented from passing the membrane with the permeate. The formula used is:  the difference obtained fromthe TDS in feedwater minus TDS in permeate divided by TDS in feedwater;  then multilply the answer obtained by 100 to obtain a percent.>>

Permeability

The ability of a body, such as a reverse osmosis or ultrafiltration membrane, to pass a liquid under pressure or to pass ions under the influence of an electric current as an ion exchange membrane in elcetrodialysis.>>

Permeate

1. To penetrate and pass through, as water penetrates and passes through soil and other porous materials.  2. That portion of the feedwater which passes through a membrane to become product water.>>

 

pH     

A measure of the degree of acidity and alkalinity in water from 0 to 14. Numbers below 7 indicate acidity whereas numbers above 7 indicate alkalinity. 7 is neutral.

Point-of-entry (POE) treatment  

Full service water treatment appied to the water entering a house or building for the purpose of reducing contaminants in the water distributed throughout the house or building (outside faucets may be excepted from treatment).>>

Point-of-use (POU) treatment   

Water treatment applied to a single tap used for the purpose of reducing contaminants in water at that one outlet. POU treatment is often used to treat water for dinking and cooking only.>>

 

Pollutant

A contaminant existing at a concentration high enough to endanger the environment or the public health or to be otherwise objectionable.>>

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.>>

Porous

Full of pores through which water, light, etc. may pass.>>

Potable Water

Water of sufficient quality to serve as drinking water is termed potable water, whether it is used for drinking or not.  Although many sources of water are utilised by humans, some contain disease vectors or pathogens and cause long-term health problems if they do not meet certain water quality standards.

 

Potassium    

Potassium is a mineral that helps the kidneys function normally. It also plays a key role in cardiac, skeletal, and smooth muscle contraction, making it an important nutrient for normal heart, digestive, and muscular function.

Pressure Differential

The difference in the pressure between two points in a water system. The difference may be due to the difference in elevation and/or to pressure drop resulting from water flow.>>

Pressure Drop

1. A decrease in the water pressure (in psi) which occurs as the water flows. Pressure drop may occur for several reasons:  internal friction between the molecules of water, external friction between the water and the walls of the piping system, or rough areas in the channel through which the water flows.    2. The difference between the inlet and outlet water pressure during water flow through a water treatment device such as a water conditioner.>>

Product Water

Water that has been through the total treatment process and meets the quality standards required for the use to which the water will be put. Product water is called by different names, depending upon which treatment process it has gone through:

"Centrate" from a centrifuge

"Distillate" from a distiller

"Filtrate" from a filter unit

"Finished" from a municipal treatment plant

"Deionized" from an cation and anion exchange system

"Softened" from a softener unit

"Permeate" from a reverse osmosis or ultrafiltration unit.>>

 

Protozoa

The term protozoa refers to a collection of generally colourless, single-celled organisms with a well-defined nucleus.  They are much bigger than bacteria, ranging in length from 5 to 100 microns.

Protozoa are among the simplest of all living organisms. As a group, protozoa are extremely diverse.  Pathogenic protozoa found in water supplies include Cryptosporidium, Giardia, Cyclospora, Naegleria, Acanthamoeba and Entamoeba.

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.>>

 

RO - Reverse Osmosis     

Osmosis occurs in nature where plants take water from a dilute solution to a concentrated solution. Reverse Osmosis (RO) reverses this process where pressure is applied to water molecules from a concentrated solution (water with dissolved contaminants) and some water (depending upon the design of the filter) passes through a semi-permeable membrane. The rest of the water is emitted from the filter as rinse water together with the contaminants.

Safe Water

Water that does not contain harmful bacteria, or toxic materials or chemicals. Water may have taste and odour problems, colour and certain mineral problems and still be considered safe for drinking.>>

Salinity

1. The relative concentration of dissolved salts, usually sodium chloride, in a given wwater.  2. A measure of the concentration of dissolved mineral substances in water.>>

Sanitize

To reduce the number of bacterial contaminants to safe levels as judged by public health requirements. To make clean and free of inactivation of dirt, filth, and conditions injurious to health.  Generally considered to reduce germ could by 50 to 99.9 percent.>>

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.>>

 

Sediments or suspended particles     

Contaminants such as dirt and rust that float in water.  Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water.

Sewage

The combination of liquids or water carrying wastes from homes, businesses, institutions, and industries. In some cases, storm water, groundwater, and surface water may be included in the sewage flow.  In the larger sense, sewage is the water supply of a community after the water supply has been used.>>

Softened Water

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

Spring Water

Water obtained from an underground formation from which water flows naturally to the surface, or would flow naturally to the surface if it were not collected underground.>>

Submicron Filter

A cartridge-type membrane filter used in fine particle separatin applications to remove particulates of less than one micron in size.>>

Surface Water

All water naturally open to the atmosphere (rivers, lakes, reservoirs, streams, impoudments, seas, estauries, etc) and all springs, wells, or other collectors which are directly influenced by surface water.>>

Suspended Solids

Solids that either float on the surface or are suspended in water or other liquids, and which are largely removable by laboratory filtering.>>

Tannin

Any of a group of water soluble, natural organis phenolic compounds that are produced by metabolism in trees and plants, and are part of the degredation-resistant fulvic acid materials formed during the decompositon of vegetation. Tannins occur in water almost any location where large quantities of vegetation have decayed. Tannins can impart a faintly yellowish to brown colour to water. Tannin molecules tend to form anions in water above pH 6 and can then be treated with anion exchange resins. Below pH 5, tannins are better treated with activated carbon.>>

TDS - Total Dissolved Solids

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 ^o -105 ^o C), and then weighing the residue. Note: A test measuring the electrical conductivity of the water provides only an estimate of the TDS present, as conductivity is not precisely proportional to the weight of an ion and non-conductive substances cannot be measured by electrical tests.>>

Total coliforms

This is a larger group of bacteria which includes E.coli and faecal coliforms. It also includes many non-faecal organisms that can grow in the environment. Total coliforms occur in much greater numbers in water sources than faecal coliforms or E. coli, and for this reason changes in their numbers (reduction by disinfection) are easier to detect.

Total coliforms are not good indicators of faecal contamination, because they may originate from many sources other than faeces.  Increases in their numbers in water distribution systems may be due to regrowth or external contamination.

 

Transmission of ultraviolet

The percentage of light wave length at 2537 angstrom units transmitted through water.>>

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. Humic acids are present in all natural water used as sources of drinking water supplies. Chloroform is one of the most common THMs formed in this type of reaction.>>

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 blocks light rays and makes the water opaque. Turbidity is lmeasured in nephelometric turbidity units (NTU). Potable water should not exceed 0.5 NTU. Turbidity cannot be directly equated to suspended solids because white particles reflect more light than dark-coloured particles and many small particles will reflect more light than an equivalent large particle.>>

Ultrafiltration

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.>>

Ultrapure Water

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.>>

Ultraviolet (UV) light

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

Velocity

(General water treatment) - The time measurement of linear motion (flow) in a given direction. For example, water flowing 60 feet in a conduit each minute has a velocity of 60 feet per minute (fpm) or one foot per second (1 fps).>>

Viruses

Viruses are a large group of infectious agents, much smaller than bacteria, and are able to be viewed only through an electron microscope.  They are not cells but biologically active particles that vary in size from 0.01 to 0.1 microns.

Viruses may survive in the environment for some time in soil or water, but they cannot multiply unless they infect a suitable host. The viruses that are of conern for water supplies can only infect humans, therefore they can arise only from human waste.  Viruses cannot be simply cultured in the laboratory in the way bacteria are identified, and for this reason it is difficult to detect viruses.

Problem viruses identified in the Australian Drinking Water Guidelines include adenovirus, enterovirus, hepatitis viruses, norwalk viruses and rotaviruses.

 

Water  

(H₂O) - A colourless transparent liquid, devoid of taste and smell and completely neutral in its reaction.

Water filter maintenance     

Regular program of replacing the water filter media/cartridges to ensure that breakthrough does not occur.

Water softener     

The removal of calcium and magnesium ions which cause hardness in water and precipitate as scale in kettles, shower heads, water pipes and heaters.

World Health Organisation

A part of the United Nations. The WHO, which is headquartered in Geneva, Switzerland, has compiled recommended standards for drinking water.>>

>> = q.v. Joseph F.Harrison, P.E., CWS-VI Wes McGowan Editor Peggy Blazek "WQA Glossary of Terms" Fourth Edition Prepared and distributed by the Water Quality Association, A not-for-profit organisation. 2000.