Microbiological testing can determine the subtype of Legionella from infected people, and this information is used to aid identification of the specific source of the outbreak. Due to the evaporative processes within a cooling tower, and combined with particulate matter in the outdoor air, a substantial amount of solids can accumulate in a cooling tower. Water temperatures and that viability of Legionella Source: Legionella is not transmitted from person to person, but is acquired by the inhalation of the bacteria, typically in a contaminated aerosol. These guidance documents have included:. The bacteria may come from one of any number of reservoirs of water, including evaporative cooling towers, pipework and water storage tanks, but the bacteria will also be naturally present in the atmosphere, including in soil, groundwater, seawater and even water on plants.
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Since it is the inhalation of the bacteria within water aerosols that carries the principal risk, that risk can be reduced by not cibss creating aerosols, and by allowing drain down of components when not in use to remove the opportunity for water dead legs. Monitoring — This includes setting up and monitoring control regimes to maintain appropriately safe conditions; and.
Microbiological testing can determine the subtype of Legionella from infected people, and this information is used to aid identification of the specific source of the outbreak. These are used in the data in Figure 2 to show the rising number of reported outbreaks in Europe. System assessment — This includes undertaking and recording system survey to determine such things as whether Legionella bacteria is likely to be present, level of risk, whether conditions prevail to promote growth, and so on.
However, this is not a case where more is better, but one where it is important to use appropriate biocides in a planned fashion, based on the monitored conditions of the cooling water.
Guidance, including the current revisions to ASHRAE Standard P focus strongly on the need to establish a robust management and control system.
The generally cibde incubation period is two to 10 days, although studies have observed periods of up to 19 days. Pragmatically, although the potential growth of Legionella can be minimized in cooling towers with good design, operation and cleaning procedures, it is unrealistic to expect that Legionella can be eliminated from the environment, and so must be controlled with appropriate procedures and water treatment.
Water temperatures cibss that viability of Legionella Source: However, there are conditions that will determine whether Legionella has the opportunity to thrive and increase the risk of infection. Small particle sizes penetrate deep into the lungs, carrying the legionella that cause infection. Due to the evaporative processes within a cooling tower, and combined with particulate matter in the outdoor air, ym13 substantial amount of solids can accumulate in a cooling tower.
Some of the rise may be attributed to more formalised reporting methods. Legionella requires nutrients to grow, and these are normally already available in mains supplied water. However, UV and pasteurisation provide localized treatment that will not affect downstream biofilms and, if not continuously applied throughout the system, allow the regrowth of Legionella.
Paul was an active member of HSE’s Legionella Committee and its Legionella Technical Working Group and has facilitated the development and delivery of past and current HSE intervention strategies for the control of Legionella risks in workplaces. Prevention is typically achieved by engineers with normal, good working practices. Since setting up his own biorisk consultancy in JulyPaul has undertaken a variety of work including the role of Water Safety Authorising Engineer at one NHS Trust and is currently providing advice and training services at a number of others, as well supporting water risk management arrangements in a number of large academic institutions.
Figure 5 relates the range of temperatures to typical applications in building services. The high incidence of individual cases in coincides with particularly high summer temperatures. Dr Paul McDermott Paul has an Honours degree and PhD in microbiology and spent the first 11 years of his career in microbiology research and as a university lecturer. Legionella is not transmitted from person to person, but is acquired by the inhalation of the bacteria, typically in a contaminated aerosol.
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Such appropriate conditions are frequently established in stagnant water. Management and communication — This includes defining responsibility; documenting system assessment and monitoring; ensuring appropriately trained people; developing action plans; and planning communication requirements, both internally and to external bodies.
Drift eliminators are essential to reduce the amount of makeup water carried into the atmosphere; however, some will still tm1.
Particular care must be taken immediately following periods of shutdown — maybe after lack of use in winter and spring — where poorly treated systems ym13 accumulate significant Legionella concentrations.
Paul has acted as expert witness in a number of Legionella enforcement cases and has contributed to the production of numerous Legionella-related guidance documents. Sinceit has been a notifiable disease in the UK.
The successful control of Legionella is as much about management as it is technical detail. There are several documents and websites most freely available that provide guidance on the management processes and technical solutions:. Recent research A in test cooling towers has shown that some non-chemical devices — including magnetic, pulsed electric field, electrostatic, ultrasonic, and hydrodynamic cavitation — that are marketed for treating biological growth, are ineffectual.
There are a number of antibiotic treatments for different strains of infection from the various species of Legionellawith good recovery rates if the infection is identified early enough. The trend probably results from a combination of increased external temperatures and greater use of aerosolgenerating devices, such as cooling towers and water sprays, both within and outside the built environment — for example, a recent report in the UK has highlighted vehicle windscreen washers as being potential sources of Legionella infections.