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Wastewater Linked to High Risk of Legionnaires’ Disease

by | Sep 9, 2019 | Industry | 0 comments


Studies found that aerosols contaminated with legionella can spread as far as 8 miles away from wastewater sources[1]! As a result, Legionnaires’ disease associated with sewage do not only affect plant employees but has also a large-scale impact on neighbouring communities.

The increasing use of reclaimed wastewater by various industries coupled to ideal proliferation conditions suggest elevated risk factors, which have been confirmed by a number of studies showing exceptionally high concentrations in these facilities.

As Legionnaires’ disease is on the rise, so is the proportion of non-serogroup 1 outbreaks[2]. This clearly demonstrates the inefficiency of traditional detection methods and highlights the need for adequate monitoring using rapid, on-site testing solutions.


Wastewater facilities’ employees and neighbouring residents are subject to high risk of legionellosis

Evidence suggest a blatant lack of monitoring and widespread legionella contamination in water networks, leading to high exposure for employees. A study[4] conducted in Spain found that 9 out of 12 samples from a wastewater treatment plant were heavily contaminated with legionella. In another instance in 2005, a Norwegian wood-based chemical industry was incriminated following an outbreak of 56 cases, including 10 deaths. This specific case highlighted the dissemination potential of air scrubbers, within a radius of more than 6 miles.[5]


Duty holder is liable if human contamination occurs

To this day, non-potable water systems have been widely neglected in legionella monitoring guidelines. Although most of legionella-specific regulations only address the risk in hot water systems of public buildings as well as in cooling towers, the duty holder is responsible for employees’ health and safety and must also ensure their undertaking do not affect people living in the perimeter.[6] Depending on the severity and conditions of the outbreak, employers and facility operators may be sued for negligence or manslaughter. Industrial firms using reclaimed water are regularly featured in the press and ordered to pay millions of pounds as penalties and compensation to the victims.

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Why is it important to monitor legionella in water systems?

Legionella is a waterborne pathogen thriving between 25-45°C. When inhaled by humans via aerosolization, it can cause Legionnaires’ disease (legionellosis), a fatal form of pneumonia. One species, L. pneumophila is responsible for an estimated 90% of legionellosis cases in the world and consists of 16 serogroups.

The European Centre for Disease Prevention reports more than 11,343 cases of Legionnaires’ disease in the European Union in 2018, which is a 50% increase over a 10-year period.[3]

Furthermore, assuming the underestimation factor of eight to ten-fold suggested by the National Academies of Sciences in the United States can apply to Europe, this would bring this number to 90,744 to 113,430 cases!


Risk is not limited to a single serogroup

wastewaterThe Dutch National Institute for Public Health points out that the proportion of Legionnaires’ Disease cases associated to non-serogroup 1 legionella is increasing [7]. This data is confirmed by various studies [8]: for example, two cases of Legionnaires’ disease in Finland in 2006[9] prompted investigations on wastewater systems, where strains of serogroups 1, 2, 3, 5, 13 were found. One of the worker’s antibody response and urinary antigen assays showed that serogroup 2 was involved in the infection.


Keep legionella at bay by implementing a suitable prevention program

The only way to avoid human contamination, costly treatments, penalties, reputation damage and service interruption is to implement a tailored prevention program.

Key elements of an effective legionella monitoring plan must include:

  1. Risk assessment and mapping of high-risk points
  2. Regular self-testing
  3. In case of contamination: appropriate and timely actions which may include water system upgrades (removal of dead arms or decay, replacement of failing parts…), thermal shocks and chlorine-based treatments
  4. Retesting to confirm efficiency of corrective measures

How to make the right choice when selecting a testing method?

Many testing solutions are available on the market and although they all claim to be efficient, criteria that must be taken into consideration when buying a testing solution include:

  • Speed of results:

Laboratory analysis has failed over the years to provide results in a timely manner, with an average delay of 10 days. While you are waiting for the diagnosis, legionella has enough time to proliferate from an acceptable threshold until exceeding the alarming rate of 100 000 CFU/L. Testing kits delivering much faster results are now available for sale.

  • Reliability:

Culture method is recognized as the most reliable as it is based on the same technique as ISO 11731:2017 standard. In the United Kingdom, most laboratories accredited by the UKAS use the culture method for legionella detection.

  • Serogroup inclusivity:

As shown above non-serogroup 1 strains of L. pneumophila can also cause deadly infections. Few testing kits on the market are able to identify all serogroups of L. pneumophila, which is a major shortcoming in most mainstream legionella detection kits.



[1] https://www.ecdc.europa.eu/en/legionnaires-disease/surveillance/atlas

[2] https://hal.univ-lorraine.fr/hal-01739129/document

[3] [6] https://www.rivm.nl/en/legionnaires-disease-legionellosis

[4] https://www.sciencedirect.com/science/article/pii/S092325089781902X

[5] https://academic.oup.com/cid/article/46/1/61/338589

[7] http://www.hse.gov.uk/pubns/priced/hsg274part1.pdf

[8] https://www.researchgate.net/publication/228521953_Legionella_pneumophila_serogroup_3_prevalence_in_drinking_water_survey_in_Israel_2003-2007

[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3014939/ 


Visit our stand at Contamination Expo in Birmingham (NEC) on September  11-12, 2019

Meet us on stand G87 to find out about our cutting-edge solutions  to detect legionella in water systems in 48 hours!

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Obtain a free expert consultation on legionella risk management based on your premises.

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