I imagine you probably know all there is to know about Legionella. The facts are well established, after all. You probably know that it can damage tape drives used to store data in IT systems for instance. You surely know that you can catch it from your car windscreen wiper reservoir. Without question, you are fully conversant with best practice for legionella control in your building. Just in case you can’t respond to any of these statements in the affirmative, Brian Booth, VP of NCH Europe’s Water Treatment Innovation Platform, distills the myth from the truth.
After scientists established, in 1976, that the bacterium that causes Legionnaires disease is present in most standing water, the scientific community developed bactericides to treat the problem.
However, in the early nineteen eighties there was a mysterious mass failure of tape drives manufactured by IBM, which created problems across the United States. At first, the company could find no fault with the drives, so they commisioned a team of their best people to investigate.
What they found surprised all of them. Each of the failed drives was located close to a ventilation duct. The biocide used to solve the problem of legionella was formulated with minute traces of tin, which was in turn collecting on the tape heads and causing them to crash.
So, in a sense, legionella was the first human disease to affect machines as well as people!
However, the effect legionella has on its human victims has the most significant impact. It creates pneumonia-like symptoms and has the potential to be fatal, particularly if there are underlying conditions also affecting the patient.
Surprisingly, given how easy it is to prevent, Legionnaires disease is believed to be growing increasingly common in the UK and across the globe. Unfortunately, it is hard to measure this precisely, as many cases are inaccurately recorded as pneumonia or simply not reported.
Causes of Legionnaire’s
Legionnaire’s Disease is caused by a widespread bacterium called Legionella, which is found in ponds, rivers and lakes. However, purpose-built water systems present the biggest danger to people. And yes, according to a report in the 2010 European Journal of Epidemiology, that includes the reservoir of your vehicle’s windscreen wipers. Naturally, this made the news but it isn’t the real issue because legionella creates a far larger risk more regularly in bigger systems.
Problems arise when still water sits at temperatures of 20-45 degrees centigrade (68-113 degrees Fahrenheit), allowing the bacteria to grow and develop. If the fluid is then converted into an aerosol or spray, it can become dangerous.
Humans contract Legionnaire’s Disease by breathing in the tiny droplets of contaminated water suspended in the air when the aerosol is created. Even in non-fatal cases, the symptoms can be very unpleasant and include temperatures of up to 38 degrees centigrade (100.4 degrees Fahrenheit) or higher, muscle pains, confusion, tiredness, chills and regular headaches.
However, due to the UK’s strict legislation and high levels of awareness of Legionnaires disease, particularly in comparison to the rest of Europe where there is a far more relaxed approach, the island nation can claim a death rate of only 10%.
Between 2011 and 2013, there were 84 deaths from Legionnaires disease in the UK. Of these, 33% encountered the bacteria while travelling outside the country.
Prevention of Legionnaire’s disease
The systems that pose the greatest risks are systems that include large tanks containing relatively stagnant or still water, including hot and cold water systems, humidifiers, evaporative cooling systems and, in particular, cooling towers, spas and hot tubs.
As well as these systems, companies with emergency showers, ornamental fountains, humidifiers, hybrid coolers, pasteurisers or air washers should also put Legionella control in place.
In order to minimise the risk of Legionnaires disease, it is essential that all water systems are regularly checked and maintained, abiding by the relevant country’s health and safety regulations. However, at NCH Europe, we recommend adhering to a code of best practice based on the UK’s approach to minimise risk.
To ensure water vessels don’t encourage the growth of bacteria, the building or facility owner should keep them at temperatures either below 20 degrees centigrade, where the bacteria will remain dormant, or above 60 degrees centigrade, where the bacteria will not be able to survive.
Similarly, facilities and plant managers or maintenance teams should keep the water clear of impurities, including organic matter, sludge, scale and biofilms.
Regular and controlled checks should be made as part of a clear predictive maintenance plan to ensure water is not contaminated and remains at the appropriate temperature.
You should also address the Management of Health and Safety Work Regulations (MHSWR), which provides a framework for preventing health and safety issues at the workplace. Similarly, the Control of Substances Hazardous to Health Regulations 2002 (COSHH) also offers a structure specifically for the prevention of Legionella bacteria, whilst suggesting what actions to take if your water system becomes infected.
The UK’s Notification of Cooling Towers and Evaporative Condensers Regulations 1992 should also be addressed, as should the Control of Legionella Bacteria in water systems: Approved Code of Practice and Guidance L8, 4th edition.
Best practice would be to contact an expert and have them undertake a Legionella risk assessment and recommend a programme of chemical and service based treatments, including monitoring and control as well as regular analysis.
You should bear in mind that the changes to the Control of Legionella Bacteria in water systems, made in the fourth edition were quite significant. As a building owner you are now required to continually update your risk assessment and include a schematic diagram in the case of both domestic systems and cooling towers.
For cooling towers, new chemical parameters need to be measured on a regular basis and taken into account in order to calculate fouling, scaling and corrosion potential.
In the case of evaporative cooling systems, the measured parameters, in conjunction with regular inspections, should be used to assess the cleanliness of the tower and system as a whole will determine the requirements and the frequency for cleaning and disinfecting the system as a whole. This is very distinct from the previous regulations, like the third edition, which suggested cleaning every six months.
IBM’s failed storage tapes are a great example of how adherence to best practice in the form of directives and legislation can help minimise the problems across a system. As a result, NCH Europe would recommend that you treat the harshest regulatory requirements, which in this case happen to be the UK’s, as best practice and adhere to them as closely as possible. If you do, you will find that eventually you will know all there is to know about Legionella, or at least everything you need to know to run a safe and well managed facility.
