Legionella Management – Principles and Practice
History
The organism was first identified in 1976 during an outbreak at an American Legion Convention in Philadelphia. 34 attendees died because of contracting the bacterium. The name has stuck since.
Requirements for Growth
- Optimum temperature range of 20 – 45 ⁰C
- Food source (other bacteria, C/N/P & sediments)
- Facultative (“breathes” with or without O2)
- Requires Cysteine and Iron
- Prefers stagnant conditions (forms Biofilm)
- Needs Water
- pH 5-8.5
About the Disease
Potentially fatal form of pneumonia –
- 5-30% fatality rate
- 200-300 cases of infection in England & Wales annually
- Incubation period 2-10 days – typical 3-6 days
- Legionella pneumophila – 23 sub types
- Long term effects (confusion, memory loss, fatigue)
Symptoms
Flu-like symptoms like fever, chills, and muscle aches.
As the infection progresses, more specific symptoms appear, including :
a cough,
shortness of breath, and
chest pain or discomfort.
Gastrointestinal issues like nausea, vomiting, and diarrhea can also occur.
Some individuals may experience confusion or changes in mental state.
Routes of Infection
Primarily through inhalation of aerosols, fine droplets & mists
Can be contracted by choking on contaminated water
Inhalation or ingestion of potting soil
Statistically most susceptible: 50 to 70 year olds/Males/ Smokers/Immuno-suppressed
Legal Duty of Care
- “ Employers have a legal duty of care to ensure the safety of all their employees.”
- HSE view Legionnaire’s Disease as “preventable” assuming management failure
Legislation
The Health and Safety at Work Act 1974
Management of Health & Safety at Work Regulations 1999
COSHH 2002
HSE L8 ACOP
L8 ACOP
Requires:
- Management regime in place
- Risk Assessments
- Control/operation regime
- Maintenance and upgrade
- Review
- Response Plan
Risk Assessment
- Identify & quantify relevant wet systems plus equipment holding /circulating water/air
- Assess potential for Legionella growth
- Identify who is at risk
- Assess the potential for bacterial transfer
- Quantify and prioritise the risks
- Determine suitable means of control/prevention/response
Responsibility
Appointed Responsible Person for day to day management
Deputy Responsible Person to cover holidays and illness
Responsibility cannot be delegated
Policy for the Control of Legionella bacteria
Management structure in place with contractor charged with carrying out:
- Legionella Risk assessments of all buildings
- Treatment of water assets where required
- Sampling and analysis of water systems
- Remedial works incl. removing “dead-legs”
Typical Systems/Equipment At Risk
Cooling Towers (for example Max Th = 57 and Tc = 37)
Condenser (cooling water side)
FF System
Domestic hot & cold water systems
Equipment producing aerosols, mists or droplets from stored water sources including showers & humidifiers
HVAC
Potable water system/Emergency Showers
Equipment holding / circulating water at 20 – 45⁰ C for example aquariums
Water tanks & baths
Spray taps
Water recirculation systems for cooling
Rarely used taps & showers (even at home)
Misting equipment
Oil / water emulsions for lubricating lathes
Mobile AC equipment with water
Metalworking Systems
How To Control Legionella
Temperature monitoring
Control release of water spray
Avoid temp. conditions 20 – 45⁰ C
Avoid water stagnation – drain & clean/disinfect regularly
Avoid materials which harbour bacteria (ex. Rubber gaskets)
Maintain cleanliness of spray outlets/shower heads
Water treatment program (disinfection, scale and corrosion control)
Point of use (POU) Membrane filter (0.2 µm)
Ensure correct & safe operation of system
Flushing regime for rarely-used outlets
Maintain low levels of bacterial counts in the MCW, FF network and showers
Maintain good water chemistry to eliminate scale formation/fouling/corrosion
Scheduled maintenance of the cooling tower Fill especially in case of fouling/biofouling
Scheduled inspection of Drift eliminators to prevent mist
PPE (FFP3 breathing mask)
Monitoring/Treatment/Remedial Options
- Monitor temperatures; 20-45⁰C = risk range
- Every 2 weeks – heat water to 60⁰C for 5 mins in showers
- Add disinfectants / NaOCl/dispersant as advised
- Clean & disinfect shower spray heads every month
- Flush rarely-used outlets weekl
- Arrange with Engineering for removal of “dead-legs” and rubber gaskets in MCW system
- Arrange with Specialist for samples to be taken if risk exists (sampling is NOT a control measure)
– it takes 10 days for results to be sent through
– it monitors whether your controls work)
Drinking Water Coolers?
2 types generally available:
Using large bottles of mineral water
Plumbed-in units
Legionella is not reported to be a problem with water bottle coolers, usually work outside “critical temperature range”,
1 reported instance of Legionella bacteria being isolated from Activated Carbon filters in a plumbed-in unit in New Zealand – replace as recommended by manufacturer.
In Conclusion
The Legionella File needs to be managed by an expert. There are legal requirements and responsibilities.
About The Author
Rami Elias Kremesti is Legionella certified with IOSH and has managed the file before in Carrington Power Station. There are a lot of so called “Hygiene” experts in the UK but they don’t understand water treatment. Proper Water treatment is at the heart of good Legionella Management.
Rami Elias Kremesti Portrait