Strike back at bacteria

There is a potential conflict between demands from clients to make hvac systems more energy-efficient and the need to control dangerous bacteria such as legionella pneumophila, which causes legionnaires’ disease. For example, reducing hot water temperatures saves energy, but also increases the risk of legionella infection because the bacterium thrives in water between 20 and 45 deg C. For some, the rise of renewable technologies has also had a significant negative effect on legionella risk.

Consultant clinical scientist with the Health Protection Agency and the Water and Environmental Microbiology Reference Unit Dr John Lee says: “In the
current context with lots of new technologies being introduced to try and make ourselves greener, we may run the risk of creating the conditions for legionella or
other organisms.”

Healthy Buildings International managing director Dave Handley adds: “Quite a lot of [renewable solutions such as solar water heating systems] that I have seen
have been installed in such a way that I regard them as a very high legionella risk. Often, the person who has had them installed has had no option - they have had to put them in to get planning permission for the development.”

HM specialist inspector for the Biological Agents Unit of the Health and Safety Executive Dr Paul McDermott agrees that new hvac technology can change the legionella risk profile. However, he warns: “It can’t be energy savings at the cost of health and safety.”

He believes we need to be cleverer about how we control legionella and that may involve using alternative methods. “Traditional techniques involve keeping hot water hot and cold water cold. That means our risk assessments have to be absolutely spot on; we might have to think a little bit more carefully about how we control risk, rather than slavishly following the guidance when that’s all it is,” he says, adding that this might, for example, mean using chemical rather than temperature
control. But can either prevent legionella?

Mission impossible?
Member of the Management Committee of the Legionella Control Association John Sweet doesn’t believe it is possible to stop legionella. “It is a naturally
occurring group of bacteria present in natural water systems, and can also be present in mains supply (drinking water) in low numbers,” he says. “Preventing its entry into other types of engineered water systems is not practical.” This, he believes, makes preventing legionnaires’ disease the objective and that this can be achieved by:

• Controlling the amplification/multiplication of the number of bacteria present;
• Minimising aerosol production/dissemination;
• Minimising contaminated aerosol inhalation;
• Applying increased control measures if a susceptible population could be exposed to aerosols.

This, explains Mr Sweet, relies on designing, installing, risk assessing and managing water systems effectively. Dr Lee agrees: “Legionella is a good example of how, in modifying our environment to suit ourselves, we have actually created an unanticipated risk. But it can be controlled by appropriate design and management.”

Improved standards
Appropriate design and management starts with effective risk assessment. A new British Standard - BS8580 Risk Assessment for the Control of Legionella in Water
Systems - should help.

The standard, which has been out for consultation and is expected to be published in the autumn, is a code of practice and guide for independent risk assessors,
regulators, facility managers and other duty holders. It describes the processes required to produce a legionella risk assessment for artificial water systems.

Dr Lee says: “Hopefully, [BS8580] will set a standard to which [contractors] can be accredited, so it should create an even playing field and improve the standard of
risk assessment.”

Healthy Buildings International’s Mr Handley represents CIBSE on the drafting committee for BS8580. He warns: “A legionella risk assessment does not necessarily advocate how you control risk; it is there to assess risk and its current control. The vast majority of water systems we are dealing with are maintained by temperature and that was one of our key focuses [when drafting BS8580].

“We are trying to bring clarity to the legionella risk assessment marketplace, because there are varying standards in the industry and varying standards and expectations elsewhere too. So there is no one place where a client could go and say: ‘When I get a legionella risk assessment, this is what I could reasonably expect’.”

He says hvac contractors rely on an effective risk assessor because risk assessment is key to legionella control. “Hopefully the presence of a good document such as BS8580 in the market will give contractors ideas of what they need to look for in their suppliers.”

For Mr Sweet, there are challenges in terms of design that he says “could be largely overcome by carrying out a preliminary risk assessment on the design of proposed new and/or refurbished installations of water systems.”

This would also help address the general ignorance in the industry. Director at the London laboratory of the Food, Water and Environmental Microbiology Network
Dr Susanne Surman-Lee says: “Poor design is an exacerbating feature in lots of buildings when legionella isn’t taken into account at the design stage. There are lots
of architects who still aren’t aware of the problem.”

Solar concern
Design is a particularly critical issue in solar thermal water heating systems, according to managing director of Solar Twin Barry Johnston. He says: “There are
potentially three ways you can plumb in a solar heating installation. There is a super safe one - thermal stores - there’s a fairly safe one - ‘heat-to-the-base system’ - and there is one that doesn’t comply with the HSE guidance - ‘don’t-heat-to-the-base system’.”

Approved Code of Practice L8 offers practical advice on how to comply with UK health and safety law relating to the control of legionella bacteria. It recommends “The water temperature at the base of the calorifier (ie under the heating coil) will usually be much cooler than the water temperature at the top. Arrangements should
therefore be made to heat the whole water content of the calorifier, including that at the base, to a temperature of 60 deg C for one hour each day.”

But Mr Johnston says: “Eighty per cent of people will not heat their solar heating systems to the base, which is the area we think is maybe of concern.” David Matthews of the Solar Trade Association disagrees: “There are no known cases in Europe of anybody linking, for example, legionella and solar. There are cases where people have died from legionnaires’ disease allied to hot water systems. They have no links that we know of to solar.”

Nonetheless, the Solar Trade Association (along with other organisations involved in hot water production) has put together a paper - Risk Assessment and Control
Measures for Household Hot Water Systems.

This is said to concentrate on “a common sense approach for the normal domestic household and is aimed at providing practical advice and knowledge to heating engineers and other interested parties”.

Mr Matthews says: “The reason we have put the risk assessment paper together is to encourage people to design and implement their systems in a manner that
avoids legionella.”

Avoiding legionella is just as important in the refurbishment of water systems as in new-build projects, says Mr Sweet: “I recently attended a building which had undergone some major refurb on the hot and cold water systems. The installer had clearly removed some outlets and installed other new ones together with replacing
storage cisterns and calorifiers.

“The site had regular micro-monitoring carried out and noticed an increase in bacteria levels following refurbishment. On inspection behind panels and in plant
ooms, it became evident that they had not considered removal of redundant pipework. Consequently, dead legs and blind ends exited throughout the system. This
highlights the requirement to carry out a pre-install assessment of proposed modifications and to carry out a complete risk assessment following system modification.”

Beyond the rules
However, Dr Surman-Lee believes legionella management is more than a simple matter of risk assessment and following the recommended guidance - principally approved code of practice (ACOP) L8.

She says: “For example, there is an increased risk in hospitals because the population is more susceptible, so any control measures put in place may need to be over and above the minimum requirement in the ACOP.

“People seem to be of the opinion that all they have to do is to comply with the ACOP and guidance, but in some cases they need to go that one step further. It has to be done on a risk assessment basis as the guidance implies. I’m not criticising the guidance, but I believe people think that is it and they don’t need to do anything else.”

L8 remains a useful guide to good practice. But it has been around for a decade, so isn’t it time it was updated?

Dr McDermott thinks not: “Some of the guidance in L8 certainly does need beefing up, which is one reason we are producing new guidance [such as that for cooling
tower cleaning]. This is designed to supplement the guidance that is already in L8, but also to keep pace with technical developments and changes in approach.

“L8 will be reviewed, but we have no concrete plans to do so. The ACOP principles are simple and sensible and my view is that they won’t change. What might
change is the guidance that supports the ACOP.”

He claims the HSE is developing a good working relationship with its industry partners and this involves a new way of working. “We will be looking to develop guidance documents with people like the Legionella Control Association, Water Management Society and British Association for Chemical Specialities,” he says.

“It is a slightly different approach - rather than the HSE putting together the guidance and then sending it out for consultation, I think it probably makes more sense to
give the job of writing the guidance to the industry and then have the HSE take a look at it. The HSE can then consult on that guidance to see how it fits with legal
obligations and the expectations of the regulator.”

The seventh Combating Legionella conference will take place on 14-15 September in London. Organised in association with H&V News, this annual event will provide the latest updates on legionella control, prevention and treatment and explain the legal requirements set out in the BS8580 Guide to Risk Assessment. The key speakers are: former director at the Health Protection Agency Dr Susanne Surman-Lee; HM specialist inspector at Health and Safety Executive Dr Paul McDermott; chairman of WMS John Lindeman; partner at Devonshires Mark London; global technical director of hygiene at NALCO Howard Barnes; and directorate manager for medical microbiology at the Royal Liverpool and Broadgreen University Hospitals Dr Tom Makin. Book your place now at www.combatinglegionella.co.uk, or call for details on 0845 056 8069.