Prevention is better than cure
Water quality management plans are essential for cooling towers, along with effective regular monitoring of hot water systems to avoid a legionella outbreak, as PAUL ANGUS reports.
According to Health Department data, in May 2017, 47 cases of Legionnaires’ disease were reported across Australia, which is a significant increase on the 28 cases reported for the same period a year earlier.
There are countless research papers, experts available, design standards around the world and equipment on the market to minimise and prevent Legionnaires’. The question therefore must be asked – why does it keep happening and how can we ensure another fatality can be prevented?
Do we need an improvement in legislation and Australian Standards to incorporate additional design, operation and maintenance techniques? You may have missed the amendment to the Public Health Regulation 2012, which was published on 1 December last year, with the new requirements that came into effect on 1 January this year.
The main update involves the occupier of premises that contain a water-cooling system. The occupier must ensure that:
- all water-cooling systems undergo monthly testing for legionella count and heterotrophic colony count, and
- reportable test results of legionella count >1000 cfu/mL (colony-forming unit per millilitre) and heterotrophiccolony count >5,000,000 cfu/mL are notified to the local government authority for that area.
DUTY OF CARE – YES, THAT MEANS YOU
Regular maintenance and testing of plumbing and mechanical plant within your facility plays an important part to prevent fatalities. But who is accountable when an outbreak occurs? Is it the facilities maintenance staff, the client, the main contractor? Or does the blame trickle down to the hydraulic contractor or the hydraulic consultant?
One thing’s for sure, we all have a duty of care and should ensure no stone is left unturned, and quite rightly so, especially as prevention is better than cure.
As the facility manager, you are responsibletoprovideadutyofcare,as defined in the Public Health Act 2010 – being a responsible person who may reasonably be expected to be competent to install, operate or maintain a water-cooling system. Relying on external companies to take this risk from you simply won’t cut it.
Monthly testing of water-cooling systems for legionella and total bacteria is an important way to prevent outbreaks of Legionnaires’ disease. The Australian Standard 3666 ‘Air-handling and water systems of buildings – microbial control’ describes good practice in the management of water cooling systems, including monthly testing and reporting.
RECIPE FOR DISASTER
Legionella is most commonly found in water services pipework, evaporative condensers, cooling towers and water fountains. As soon as these systems fail to be correctly maintained, the bacteria can grow to significant proportions.
It’s really quite a simple recipe that can occur in any facility, by becoming lax on risk assessment measures:
- add a sprinkle of slack water treatment in for good measure, don’t forget the stagnant water!
- place the hot water system somewhere warm and temperate – just wait a short while to see the fantastic results that have allowed the legionella bacteria to ‘prove’
- use the water in an aerosol (shower) or for misting purpose (cooling tower), then
- add people to your facility.
Et voilà! Legionnaires’ biofilms will grow and multiply in force in a blink of the eye. Legionella is not a fussy tenant. It doesn’t care what size the building is or how many people are there. It’s just waiting for these correct conditions to occur and to become airborne. Just follow the recipe above and you will eventually have a ‘deadly’ success.
Preventing legionella should focus on engineering solutions such as design and installation, plus the selection, location and maintenance regime of plumbing and mechanical plant. And, as with any great engineering design, how a system is operated and maintained is paramount to its ongoing success. Whatever the approach, it must be integrated with modern technology, such as being connected to a building management system (BMS) to provide real-time monitoring and avoid human error.
The time of year is also critical; for example, in the peak summer months when air-conditioning is in use, the cooling towers can be subjected to heat from the sun and temperatures can easily rise to the required temperatures for legionella to form. Similarly, facilities that have been inactive during holiday periods or levels of buildings used infrequently will contain stagnant water and require a water management plan to flush or pasteurise the system.
HITTING THE HOT SPOT!
Consideration at the design stage on a hot water circuit may often be disregarded by a hydraulic contractor to save time or money. It is therefore imperative that the consultant overseeing the installation ensures the installation is correct. The design, including the pipework route and diameter of the hot water distribution system, is particularly important for the hot water return circuit, ensuring the hot water system is working to its full capability.
A full appraisal should be undertaken to consider the usage of supplementary treatments, although these can come at a cost. Do the contractor, hydraulic engineer and building services consultant fully understand that a simple cost saving in the short-term could ultimately be costing another person’s life in the long-term?
The hot water plant also requires careful selection and location, taking into account peak periods and frequency of use. These heaters should be capable of ensuring a temperature rise that can provide a pasteurisation cycle to disinfect the system and eliminate biofilm forming and building up within the internal surfaces of pipework.
Similarly, how much thought goes into locating and installing thermostatic mixing valves (TMVs)? These mixed hot water temperature ‘dead legs’ can be overlooked at either design or installation stage and unintentionally become a breeding ground. Introduce a shower outlet, which is used intermittently, and the water becomes stagnant, and it will impact the mixed hot water temperature to become a breeding ground for Legionnaires’ biofilm.
Flushing and treating the pipework at installation stage helps to prevent legionella from forming; however, it doesn’t stop there. As buildings are refurbished, capped pipework should be taken back to the final branch to avoid stagnant pockets of water occurring and becoming a further breeding ground for biofilm.
A risk assessment and identification process should be carried out on the water services system. This will help to spotlight any conditions that could encourage bacteria to multiply. For example, if the water temperature happens to be between 20 and 45 degrees Celsius, there is a means of creating and disseminating breathable droplets (e.g. the aerosol created by a shower or cooling tower).
All you need is a few susceptible people to be exposed to the contaminated aerosols and you have an outbreak on your hands.
Temperature is important, particularly in business today with such a high focus on energy efficiency and escalating energy costs. Good practice in the energy world is to reduce temperatures to save energy and money; however, making an unguided decision to reduce the hot water temperature from 60 to 50 degrees Celsius dramatically increases the risk of legionella throughout the hot water system.
RISK MANAGEMENT PLAN
Managing the risk is of vital importance. A risk management plan or water quality management plan must be prepared for preventing or controlling the risk. In order for control measures and guidelines to remain effective, regular monitoring of the systems and the control measures is essential. Monitoring of general bacterial numbers can indicate whether microbiological control is being achieved. Sampling for legionella is another means of checking that a system is under control.
The plan is a living document that should be reviewed and updated regularly. This is the only way to ensure the tenants’ safety within the facility you operate. By achieving the right engineering design elements, operating and maintaining systems correctly, keeping records of the steps and precautions in place and, importantly, appointing a person to be managerially responsible, these precautions can prevent a deadly outbreak.
Paul Angus is an associate director – Hydraulic Services at AECOM, based in Sydney. Paul has strong commercial and technical capability in developing and delivering hydraulic design strategies and solutions. He specialises in providing a sustainable approach to system design, including water conservation, recycling and generating innovative engineering solutions. He has extensive experience in the hydraulic design, pre-acquisition and condition surveys, including all forms of specialist client advisory work.
This article also appears in the June/July issue of Facility Management magazine.
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