Prevention and control of Legionella Bacteria in Water Systems

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Prevention and Control of Legionella Bacteria in Water Systems
(HSE approved code of practice and guidance. L8)

Legionnaires disease, background.

Legionella was first recognised in water systems in 1976, when a group of American Legion ex-servicemen were stricken with a pneumonia type infection while attending a conference in the Bellevue Stratford Hotel Philadelphia, resulting in the deaths of 29 of the 182 delegates and the coining of the phrase 'Legionnaires Disease' to describe the affliction. Since then over 50 other species of legionella have been discovered of which at least 20 have been associated with disease in humans.

Reports of Legionnaires’ disease continues to rise. Premises storing water are at risk from Legionella a life-threatening bacteria which is now known to be commonly present in water systems and which proliferates in certain aquatic conditions. Following this incident it was discovered that the bacteria is normally contracted by inhaling either tiny droplets of water (aerosols) or in droplet nuclei (the particles left after the water has evaporated). With regular inspection of premises water systems, the risk of exposure can be minimised or eliminated.

Conditions favourable to multiplication.

Legionella bacteria are common and can be found in water sources such as lakes, rivers and reservoirs however they are normally low in number. The optimum temperature for multiplication is at around 37 °C. At higher temperatures, the rate of multiplication decreases, and at 46 °C ceases. The bacteria can survive at higher temperatures but at 70 °C the organism is killed. Below 37 °C the multiplication rate decreases and it can be considered to be insignificant below 20 °C. Legionella bacteria also require a supply of nutrients to multiply. Sources can include algae, amoebae and other bacteria. The presence of sludge, scale and sediment are also thought to play a part in harbouring and providing favourable conditions for growth.

Legal duty of employers and managers.

Employers and managers of premises have a legal duty to ensure they have measures in place to prevent and control Legionella in their water systems. The disease is not known to be transmissible via person-to-person contact and the way to prevent or control outbreaks of Legionnaires’ disease is to inhibit or limit the growth of these organisms in water.

Our recommendations for minimising the risk of exposure to Legionella

To ensure compliance and avoid prosecution in the event of an outbreak, you must identify the risks from Legionella that may affect staff or the public through a comprehensive risk assessment of your water systems. With the findings from a risk assessment, a programme of control measures can be implemented in accordance with the code of practice. Following our surveyor visit, we will be able to determine if further action is required to your current risk assessment, control measures and record keeping. Based upon his initial assessment and your requirements we will supply you with a written quotation setting out our recommendations.

Our engineers are trained to a standard which ensures risk assessments are carried out in a technically competent manner and are set up to be reviewed every two years. We have been devising and managing control programs over many years for a variety of clients. Our proven on-line document management system "Log-Book Portal" certified by LRQA to BS EN 9001:2000 will assist in the implementation of the control program and management of records keeping to demonstrate compliance.

To arrange a free, no-obligation quotation, contact us.

Relevant publications and standards
BS7592: 2008 Sampling for Legionella bacteria in water systems, code of practice.
HSE: The Control of Legionella Bacteria in Water Systems (L8).
CIBSE: Minimising the risk of Legionnaires disease TM13.