Glossary


Aerosol

A suspension in a gaseous medium of solid particles, liquid particles or solid and liquid particles having negligible falling velocity.


AFLP - Amplified Fragment Length Polymorphisms

A highly sensitive method for detecting polymorphisms in DNA.

Following restriction enzyme digestion of DNA, a subset of DNA fragments is selected for PCR amplification and visualisation.


Air-Conditioning

A form of air treatment whereby temperature, humidity and air cleanliness are all controlled within limits determined by the requirements of the air-conditioned enclosure.


Algae

A small, usually aquatic, plant which requires light to grow, often found on exposed areas of cooling towers.


Amoebae

Protozoa able to alter shape as a result of movements of cell processes.

Protozoa generally live in fresh water, soil or as parasites in humans and animals.

Some amoebae can ingest Legionella allowing them to replicate in a protected environment.


Antibodies

Substances in the blood which destroy or neutralise various toxins or components of bacteria known generally as antigens.

The antibodies are formed as a result of the introduction into the body of the antigen to which they are antagonistic as in all infectious diseases.


Anti-Corrosive Chemicals

Anti-corrosive chemicals are also known as corrosion inhibitors. Chemicals which protect metals by:

(a) passivating the metal by the promotion of a thin metal oxide film (anodic inhibitors); or

(b) physically forming a thin barrier film by controlled deposition (cathodic inhibitors).


Artificial Water Systems

Any water system that has been constructed and does not occur naturally such as a hot water system.


Audits

See also legionella audits.

The inspection and verification of an existing legionella risk management system.

This would normally involve the review of existing legionella risk assessment reports and other documentation to ensure all critical risks are addressed and action plans are operational.


Bacteria

The singular of bacterium, a microscopic, unicellular (or more rarely multicellular) organism.


Biocides

A chemical substance which kills micro-organisms.

There are two types, oxidizing and non-oxidizing biocides.


Biodispersants

A chemical product that can be added to recirculating water within a cooling system to penetrate and break down biofilms.


Biofilm

A community of bacteria and other micro-organisms, embedded in a protective layer with entrained debris, attached to a surface.


Blow-Down / Bleed-Off

Water discharged from the system to control the concentration of salts or other impurities in the circulating water; usually expressed as a percentage of recirculating water flow.


Calorifier

A calorifier, also more commonly referred to as a water heater is an item of equipment used for the transfer of heat to water in a vessel, the source of heat being contained in a pipe or coil immersed in the water. Also see water heater.

How to check calorifier flow and return hot water temperatures... calorifier video


CFU - Colony Forming Units

A unit of measurement used in microbiology that indicates the number of microorganisms present in a water sample.

It is normally measured by the number of colony forming units (CFU) present in one millilitre of water.


Chlorine

A chemical element commonly used for disinfection purposes.

An oxidising biocide.


Cold Water Services (CWS)

Installation of plant, pipes and fittings in which cold water is stored, distributed and subsequently discharged.


Concentration Factor

The concentration factor (CF) compares the level of dissolved solids in the cooling water with that dissolved in the make-up water (also known as cycle of concentration).

Usually determined by comparison of either the chloride or magnesium hardness concentration.


Cooling Tower

A cooling tower is an apparatus through which warm water is discharged against an air stream; in doing so part of the water is evaporated to saturate the air and this cools the water.

The cooler water is usually pumped to a heat exchanger to be reheated and recycled through the tower.


Corrosion Inhibitors

Corrosion inhibitors are speciality chemicals which protect metals by:

(a) passivating the metal by the promotion of a thin metal oxide film (anodic inhibitors); or

(b) physically forming a thin barrier film by controlled deposition (cathodic inhibitors).


Dead End / Blind End

A dead end or blind end describes a length of pipe closed at one end through which no water passes.


Deadlegs

A deadleg describes a pipe leading to a fitting through which water only passes when there is draw-off from the fitting.


Decontamination

The process of removing or neutralising pathogenic bacteria in a water or other system.


Dip slides

A dip slide is a means of testing the microbial content of liquids.

It consists of a plastic carrier bearing a sterile culture medium which can be dipped in the liquid to be sampled.

It is then incubated to allow microbial growth.

The resulting microbial colonies are estimated by reference to a chart.

More on dip slides...


Disinfection

A process which destroys or irreversibly inactivates micro-organisms and reduces their number to a non-hazardous level.


Distribution Circuit

Pipework which distributes water from hot or cold water plant to one or more fittings/appliances.


Domestic Water Services

Hot and cold water intended for personal hygiene, culinary, drinking water or other domestic purposes.


Drift

Circulating water lost from the tower as liquid droplets entrained in the exhaust air stream; usually expressed as a percentage of circulating water flow but for more precise work it is parts of water per million by weight of air for a given liquid to gas ratio.


Drift Eliminator

More correctly referred to as drift reducers or minimisers – equipment containing a complex system of baffles designed to remove water droplets from cooling tower air passing through it.


Evaporative Condenser

A heat exchanger in which refrigerant is condensed by a combination of air movement and water sprays over its surface.


Evaporative Cooling

A process by which a small portion of a circulating body of water is caused to evaporate thereby taking the required latent heat of vaporisation from the remainder of the water and cooling it.


Fill / Packing

That portion of a cooling tower which constitutes its primary heat transfer surface; sometimes called tower ‘packing’ or ‘pack’.


Flushing

The process of draining and cleaning a cooling system, including all associated pipework.


Fouling

Organic growth or other deposits on heat transfer surfaces causing loss in efficiency.


Half-Life

The ratio of system volume to purge rate.


Hot Water Services (HWS)

Installation of plant, pipes and fittings in which water is heated, distributed and subsequently discharged (not including cold water feed tank or cistern).


Langelier Saturation Index (LSI)

The Langelier Saturation Index (LSI) helps to determine the scaling potential of water and is based on the study of the carbonate equilibrium in water.


Legionaires’ Disease

A misspelling, more correctly spelt Legionnaires' disease which is a severe form of pneumonia caused by Legionella bacteria.


Legionella

Type of aerobic bacterium which is found predominantly in warm water environments.

Singular of legionellae.


Legionella Audits

The inspection and verification of an existing legionella risk management system.

This would normally involve the review of existing legionella risk assessment reports and other documentation to ensure all critical risks are addressed and action plans are operational.


Legionella Bacteria

Legionella bacteria, singular bacterium, a microscopic, unicellular (or more rarely multicellular) organism.

The germ which causes Legionnaires' disease is a bacterium called Legionella pneumophila.


Legionella Bacterium

Legionella bacterium, plural bacteria, a microscopic, unicellular (or more rarely multicellular) organism.

The germ which causes Legionnaires' disease is a bacterium called Legionella pneumophila.


Legionella Disease

A name sometimes used to describe Legionnaires' disease.

Legionnaires' disease is a form of pneumonia caused by legionella bacteria.

Legionella is a type of aerobic bacterium which is found predominantly in warm water environments (singular of legionellae).


Legionellae

The genus legionella belongs to the family legionellaceae which has over 40 species.

These are ubiquitous in the environment and found in a wide spectrum of natural and artificial collections of water.


Legionella Longbeachae

One of the causative organisms of Legionnaires’ disease.

Has also been associated with soil, potting compost, mulches, compost heaps and composted animal manures.

Particularly common in Australia although cases have been reported in other countries including the USA, Japan and the United Kingdom.


Legionella Pneumonia

Legionnaires' disease is a type of pneumonia.

It was named after an outbreak of severe pneumonia which affected a meeting of the American Legion in 1976.

The germ which causes Legionnaires' disease is a bacterium called Legionella pneumophila.


Legionella Pneumophila

One of the causative organisms of Legionnaires’ disease.


Legionella Pneumophilia

A misspelling, more correctly spelt Legionella pneumophila which is one of the causative organisms of Legionnaires’ disease.


Legionella Micdadei

The second most commonly isolated member of the Legionella family.

The bacterium can cause flu like symptoms and pneumonia, including Pittsburgh pneumonia.


Legionella Sampling

Any monitoring programme should include routine sampling and testing for the presence of bacteria, both general (aerobic) bacterial species and legionella bacteria.

Detection of Legionella bacteria requires specialist laboratory techniques, although routine monitoring for aerobic bacteria can be used as an indication of whether microbiological control is being achieved.

More on legionella testing...


Legionella Species

Currently there are over 40 species and even more serogroups of legionella including:

  • Legionella adelaidensis
  • Legionella anisa
  • Legionella beliardensis
  • Legionella birminghamensis
  • Legionella brunensis
  • Legionella busanensis
  • Legionella cherrii
  • Legionella cincinnatiensis
  • Legionella donaldsonii
  • Legionella drancourtii
  • Legionella drozanskii
  • Legionella erythra
  • Legionella fairfieldensis
  • Legionella fallonii
  • Legionella feeleii
  • Legionella geestiana
  • Legionella gratiana
  • Legionella gresilensis
  • Legionella hackeliae
  • Legionella israelensis
  • Legionella jamestowniensis
  • Legionella jordanis
  • Legionella lansingensis
  • Legionella londiniensis
  • Legionella longbeachae
  • Legionella lytica
  • Legionella monrovica
  • Legionella moravica
  • Legionella nautarum
  • Legionella oakridgensis
  • Legionella parisiensis
  • Legionella pneumophila
  • Legionella quateirensis
  • Legionella quinlivanii
  • Legionella rowbothamii
  • Legionella rubrilucens
  • Legionella sainthelensi
  • Legionella santicrucis
  • Legionella shakespearei
  • Legionella spiritensis
  • Legionella steigerwaltii
  • Legionella taurinensis
  • Legionella tucsonensis
  • Legionella wadsworthii
  • Legionella waltersii
  • Legionella worsleiensis

Legionellosis

Any illness caused by exposure to legionella.


Legionnaires’ Disease

Legionnaires’ disease is a severe form of pneumonia caused by legionella bacteria.


Make-Up Water

Water which is added to a cooling water system to compensate for wastage (e.g. via system leaks), evaporative loss and bleed.


Micro-Organism

An organism of microscopic size including bacteria, fungi and viruses.


Multi-Locus Sequence Typing

A method of molecular typing, relying on DNA sequence analysis of nucleotide polymorphisms in several genes.

This technique has shown a high degree of intra-species discriminatory power for bacterial and fungal pathogens.


Non-Oxidising Biocide

A non-oxidising biocide is one that functions by mechanisms other than oxidation, including interference with cell metabolism and structure.


Nutrients

A food source for micro-organisms.


Oxidizing Biocides

Agents capable of oxidizing organic matter, e.g. cell material, enzymes or proteins which are associated with microbiological populations resulting in death of the micro-organisms.

The most commonly used oxidizing biocides are based on chlorine or bromine (halogens) which liberate hypochlorous or hypobromous acids on hydrolysis in water.

The exception is chlorine dioxide, a gas which does not hydrolyse but which functions in the same way.


Parts Per Million (ppm)

Parts per million is a measure of dissolved substances given as the number of parts there are in a million parts of solvent.

It is numerically equivalent to milligrams per litre mg/l with respect to water.


Pasteurisation

Heat treatment to destroy micro-organism usually at high temperature.


PCR

PCR, polymerase chain reaction.


Phenotypic Variations

Differences in the expression of genes as determined by observable characteristics such as the presence or absence of a particular cell component.


Planktonic

Free floating micro-organisms in an aquatic system.


Plume

The visible discharge of air and moisture from a cooling tower or other scooling system.

This can include condensation and aerosols and as such represents a potential legionella risk.


Pond / Sump

Collection of cooling water at the base of a cooling tower.


Pontiac Fever

Pontiac fever is a disease caused by species of legionella, an upper respiratory illness less severe than Legionnaires’ disease.


Puckorius Scaling Index (PSI)

The Puckorius Scaling Index (PSI) helps to determine the scaling potential of water.

The PSI method attempts to quantify the relationship between the saturation state of the water and the amount of scale deposited.


PPE - Personal Protective Equipment

Personal protective equipment is used to protect personnel during hazardous operations.


Retention Time

Describes the time a chemical is retained in the system.


Risk Assessment

Identifying and assessing the risk from legionellosis from work activities and water sources on premises and determining any necessary precautionary measures.


Ryznar Stability Index (RSI)

The Ryznar Stability Index (RSI) helps to determine the scaling potential of water.

RSI is based on the concept of saturation level and attempts to to quantify the relationship between calcium carbonate saturation and scale formation.


Scale

Crystalline deposits that form on system surfaces or pipework.

Scale normally results from a build up of unwanted minerals, usually calcium carbonate.

See also scale inhibitors.


Scale Inhibitors

Chemicals used to control scale.

They function by holding up the precipitation process and/or distorting the crystal shape, thus preventing the build-up of a hard adherent scale.


Sentinel Taps

For hot water services installations, sentinel taps describe the first and last taps on a recirculating system.

For cold water systems (or non-recirculating hot water systems), the nearest and furthest taps from the storage tank.

The choice of sentinel taps may also include other taps which are considered to represent a particular risk.

How to check hot water temperatures at sentinel outlets... sentinel outlet video


Sero-Group

A sub-group of the main species.


Sessile

Aquatic micro-organisms adhering to a surface normally as part of a biofilm.


Shunt Pump

A circulation pump fitted to hot water service/plant to overcome the temperature stratification of the stored water.


Slime

A mucus-like exudate which covers a surface produced by some micro-organisms.


Sludge

A general term for soft mud-like deposits found on heat transfer surfaces or other important sections of a cooling system.

Also found at the base of calorifiers and cold water storage tanks.


Spa Pools

A spa pool is a self-contained body of warm water designed for sitting in (not whole body immersion).

It is intended for a small number of people to use at one time.

The water is re-circulated and kept between 30 - 40oC and is usually not drained between use and is continually filtered and cleaned.

A hydro-jet circulation, with or without an air induction bubble system, is also used to agitate the water.

Spa pools are known under a range of names including spa bath, hot spa, hot tub, portable spa, whirlpool spa, swim spa and often Jacuzzi.

All systems usually work in the same way.


Spray Drift

Aerosol emissions from cooling towers due to fan forced or extracted air exiting the cooling system or tower.

This can include condensation and aerosols and as such represents a potential legionella risk.


Stagnation

The condition where water ceases to flow and is therefore liable to microbiological growth.


Strainers

A coarse filter usually positioned upstream of a sensitive component such as a pump control valve or heat exchanger to protect it from debris.


Surfactants

Soluble surface acting additives that help to reduce the surface tension between water and particulate matter.


Thermal Disinfection

Heat treatment (elevated temperatures) used to disinfect a system.


Thermostatic Mixing Valves (TMV's)

Mixing valve in which the temperature at the outlet valve is pre-selected and controlled automatically by the valve.

How to check the hot water temperature at a TMV... TMV video


Total Viable Counts (TVC)

The total number of culturable bacteria (per volume or area) in a given sample (does not include legionella).


Water Heater

A water heater, also referred to as a calorifier is an item of equipment used for the transfer of heat to water in a vessel, the source of heat being contained in a pipe or coil immersed in the water. Also see calorifier

How to check water heater flow and return hot water temperatures... water heater video


Windage

Physical loss of water from a cooling tower caused by draught of air or wind – water is lost around the base of the cooling tower as a result of cross winds as opposed to drift.

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Email: info@legionellacontrol.com

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