Legionella & Water Management Glossary


Aerosol

An aerosol is 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

AFLP stands for Amplified Fragment Length Polymorphisms. It is 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

Air conditioning often abbreviated to “Air Con” is 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

Algae are small, usually aquatic, plants which require light to grow, often found on exposed areas of cooling towers. There presence on cooling towers and their surroundings can sometimes be a sign that the tower is defective or poorly maintained and should prompt further investigation.


Amoebae

Amoebae are 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

Antibodies are 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. They are speciality water treatment 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

Artificial water systems are any water system that has been constructed (man-made) and does not occur naturally such as a hot water system.


Audits

See also legionella audits.

An audit in a legionella or water management context describes 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

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


Biocides

Biocides are a chemical substance which kill micro-organisms.

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


Biodispersants

Biodispersants are chemical products that can be added to re-circulating water within a cooling tower or cooling system that are designed to penetrate and break down biofilms.


Biofilm

A biofilm is a community of bacteria and other micro-organisms, embedded in a protective layer with entrained debris, attached to a surface. They can colonise water systems, can cause contamination and are often difficult to remove.


Blow-Down / Bleed-Off

Blow-down or bleed-off describes the water discharged from a 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 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… how to check calorifier water temperatures


CFU – Colony Forming Units

A colony forming unit or CFU is 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

Chlorine is a chemical element commonly used for water disinfection purposes. It is widely used for the treatment of water because of its good disinfecting properties and its cost effectiveness.

Chlorine is an oxidising biocide.


Cold Water Services (CWS)

Cold water services is a wide-ranging term that describes plant installations, 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).

Concentration factor is 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.

Wet cooling towers are considered high risk are are subject to strict legionella controls.


Corrosion Inhibitors

Corrosion inhibitors (see also anti-corrosive chemicals) are speciality water treatment 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. They can result in the local stagnation of water and are considered high risk. They should be removed where possible.


Deadlegs

A deadleg describes a pipe leading to a fitting through which water only passes when there is draw-off from the fitting. They can result in the local stagnation of water and are considered high risk. They should be removed where possible.


Decontamination

Decontamination describes 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.

A dip slide 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.


Disinfection

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


Distribution Circuit

A distribution circuit describes pipework which distributes water from hot or cold water plant to one or more fittings/appliances.


Domestic Water Services

Domestic water services describes hot and cold water systems that are intended for personal hygiene, culinary, drinking water or other domestic purposes.


Drift

Drift describes the circulating water that is lost from a cooling 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

Drift eliminators are also 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

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


Evaporative Cooling

Evaporative cooling describes 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. The process is used in wet cooling towers.


Fill / Packing

Fill or packing describes that portion of a cooling tower which constitutes its primary heat transfer surface; sometimes called tower ‘packing’ or ‘pack’. Cooling tower pack requires regular maintenance as part of a legionella control programme.


Flushing

Flushing describes the process of draining and cleaning a cooling system, including all associated pipework. It is also used to describe the process of regular flushing little used outlets in hot and cold water systems.


Fouling

Fouling describes the organic growth or other deposits found on heat transfer surfaces causing loss in efficiency. Fouling or biofouling also occurs in water systems where there is a build up of bacteria and biofilm.


Half-Life

Half-life describes the ratio of water system volume to purge rate.


Hot Water Services (HWS)

Hot water services or HWS describe plant installations, pipes and fittings in which water is heated, distributed and subsequently discharged (not including cold water feed tank or cistern).


Incubators – Dip Slide Incubators

Incubators or dip slide incubators are electrical components used to incubate dip slides and other microbiological tests at controlled temperatures.


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. Monitoring the LSI aids in the control of scale which is essential in the maintenance of heat transfer surfaces, operational components and the control of Legionnaires’ disease.


Legionaires’ Disease

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


Legionella

Legionella is a type of aerobic bacterium which is found predominantly in warm water environments. It can inhabit lakes, ponds and other natural water courses but becomes problematic in man-made water systems with the potential to cause Legionnaires’ disease under certain conditions.

Singular of legionellae.


Legionella Audits

A legionella audit describes 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

Legionella longbeachae is 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

Legionella pneumophila is 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

Legionella micdedei is ohe second most commonly isolated member of the legionella family.

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


Legionella Sampling

Legionella sampling forms part of a monitoring programme. The legionella control 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.


Legionella Species

There are many different legionella species and even more serogroups of legionella including:

  • L. adelaidensis
  • L. anisa
  • L. beliardensis
  • L. birminghamensis
  • L. bozemanii
  • L. bozemanii
  • L. brunensis
  • L. busanensis
  • L. cardiaca
  • L. cherrii
  • L. cincinnatiensis
  • L. clemsonensis
  • L. donaldsonii
  • L. drancourtii
  • L. dresdenensis
  • L. drozanskii
  • L. dumoffii
  • L. erythra
  • L. fairfieldensis
  • L. fallonii
  • L. feeleii
  • L. feeleii
  • L. geestiana
  • L. genomospecies 1
  • L. gormanii
  • L. gratiana
  • L. gresilensis
  • L. hackeliae
  • L. hackeliae
  • L. impletisoli
  • L. israelensis
  • L. jamestowniensis
  • Candidatus L. jeonii
  • L. jordanis
  • L. lansingensis
  • L. londiniensis
  • L. longbeachae
  • L. longbeachae
  • L. lytica
  • L. maceachernii
  • L. massiliensis
  • L. micdadei
  • L. moravica
  • L. nagasakii/nagasakiensis
  • L. nautarum
  • L. norrlandica
  • L. oakridgensis
  • L. parisiensis
  • L. pneumophila (Philadelphia 1)
  • L. pneumophila (Knoxville 1)
  • L. pneumophila (Benidorm 030 E)
  • L. pneumophila (France 5811)
  • L. pneumophila (Allentown 1)
  • L. pneumophila (OLDA)
  • Legionella pneumophila (Oxford 4032 E)
  • Legionella pneumophila (Bellingham)
  • Legionella pneumophila (Heysham 1)
  • Legionella pneumophila (Camperdown 1)
  • Legionella pneumophila (Togus 1)
  • Legionella pneumophila (Bloomington 2)
  • Legionella pneumophila (Los Angeles)
  • L. pneumophila (Portland1)
  • L. pneumophila (Dallas 1E)
  • L. pneumophila (Cambridge 1)
  • L. pneumophila (Chicago 1)
  • L. pneumophila (Chicago 8)
  • L. pneumophila (Concord 3)
  • Legionella pneumophila (IN-23-G1-C2)
  • Legionella pneumophila (Leiden 1)
  • L. pneumophila (797-PA-H)
  • Legionella pneumophila (570-CO-H)
  • Legionella pneumophila (82A3105)
  • Legionella pneumophila (1169-MN-H)
  • Legionella pneumophila (Lansing 3)
  • L. quateirensis
  • L. quinlivanii
  • L. quinlivanii
  • L. rowbothamii
  • L. rubrilucens
  • L. sainthelensi
  • L. sainthelensi
  • L. santicrucis
  • L. saoudiensis
  • L. shakespearei
  • L. spiritensis
  • L. steelei
  • L. steigerwaltii
  • L. taurinenesis
  • L. tucsonensis
  • L. tunisiensis
  • L. wadsworthii
  • L. waltersii
  • L. worsleiensis
  • L. yabuuchiae

Legionellosis

Legionellosis describes any illness caused by exposure to legionella bacteria.


Legionnaires’ Disease

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


Make-Up Water

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


Micro-Organism

A micro-organism is an organism of microscopic size including bacteria, fungi and viruses.


Multi-Locus Sequence Typing

Multi-locus sequence typing describes 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

Nutrients are a food source for micro-organisms.


Oxidising Biocides

Oxidising biocides are chemical 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 oxidising 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

Pasteurisation describes a heat treatment process to destroy micro-organism usually at high temperature.


PCR

PCR, polymerase chain reaction.


Phenotypic Variations

Phenotypic variations describes the differences in the expression of genes as determined by observable characteristics such as the presence or absence of a particular cell component.


Planktonic

Planktonic is the term used to describe free floating micro-organisms in an aquatic system.


Plume

Plume describes the visible discharge of air and moisture from a cooling tower or other cooling system.

This can include condensation and aerosols (airborne water droplets) and as such represents a potential legionella risk.


Pond / Sump

A pond or sump is a 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. See also Langelier Saturation Index.


PPE – Personal Protective Equipment

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


Retention Time

Retention time describes the time a chemical is retained in the system.


Risk Assessment or Legionella Risk Assessment

A risk assessment or legionella risk assessment describes the process of dentifying 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

Scale comprises crystalline deposits that form on system surfaces or pipework.

Scale normally results from a build up of unwanted minerals, usually calcium carbonate. Scaling should be controlled as it can lead to heat transfer inefficiencies, reduce the life of plant and equipment and encourage bacteria.

See also scale inhibitors.


Scale Inhibitors

Scale inhibitors are speciality water treatment chemicals used to control the build up of scale in water.

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),sentinel outlets are 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:


Sero-Group

Asero-group is a sub-group of the main species.


Sessile

Sessile describes aquatic micro-organisms adhering to a surface normally as part of a biofilm.


Shunt Pump

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


Slime

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


Sludge

Sludge is a general term used 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 (also called a hot tub, spa bath or Jacuzzi) 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.

Spa pools represent a legionella risk and require expert management.


Spray Drift

Spray drift describes an aerosol emission from a cooling tower due to fan forced or extracted air exiting the cooling system or cooling tower.

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


Stagnation

Stagnation describes the condition where water ceases to flow and is therefore liable to microbiological growth. Stagnation of water should be avoided as it increases the potential for bacteria proliferation.


Strainers

Strainers is the term used to describe the coarse filter usually positioned upstream of a sensitive component such as a pump control valve or heat exchanger to protect it from debris.


Surfactants

Surfactants describe soluble surface acting chemical additives that help to reduce the surface tension between water and particulate matter.


Thermal Disinfection

Thermal disinfection is a common heat treatment (elevated temperatures) used to disinfect a system. It is a commonly used technique to control legionella bacteria in water systems.


Thermostatic Mixing Valves (TMV’s)

Thermostatic mixing valves or TMVs are special valves that automatically control water temperatures at taps/showers/outlets to a pre-selected setting to prevent scalding from hot water. There are two main types of TMV, TMV2 and TMV3. TMV3 valves are used in hospitals and healthcare settings.

Learn how to check the hot water temperatures at a TMV:


Total Viable Counts (TVC)

Total Viable Counts or TVC describe the total number of culturable bacteria (per volume or area) in a given sample (this 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

Learn how to check water heater flow and return hot water temperatures:


Windage

Windage describes the 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.