Frequent outbreaks

The last New South Wales summer was long and hot, and this meant air conditioning systems battled away at a higher load for longer periods than they normally would. Legionella outbreaks were more frequent, particularly in the city of Sydney.

HydroChem’s CEO, Nick Duncan, has well over a decade of experience advising the harbour city’s commercial building sector.

“The temperature drop this winter seemed quite sudden,” says Duncan.”When this happens we see a significant reduction in the levels of bacterial detections (including Legionella) in the cooling towers that we maintain.This year was no different.”

“This pattern is quite common and can be attributed to the change in climactic conditions,” continues Duncan. “Outside temperatures drop resulting in a diminished demand for cooling and the knock-on effect is cooler water temperatures within systems. “

Cooler water reduces the rate of microbial multiplication.Lower fan use means that there are fewer nutrients drawn into the system to promote the growth of bacteria, including Legionella. Many systems will not operate at all in the winter months.

Outside temperatures are particularly changeable in Australia as spring approaches and hot spells are not uncommon. This sudden demand for cooling from dormant systems can result in an increased risk for the proliferation of Legionella bacteria.

“Increased water temperatures and the resultant nutrition for microbial growth are just a part of it,” says HydroChem’s CEO. “The stop start approach of the Australian summer often leads to intermittent demand as we alternately experience warmer then cooler days. Spring can be a dangerous time with the risk of Legionella even higher in some systems than we see during summer when cooling towers are operational and running on a full load.”

Managing Legionella

These factors are manageable with good risk mitigation strategies in place. A simple tick-the-box compliance approach is dangerous and will not necessarily provide the finesse required to adequately control the Legionella risk. System stagnancy is a tough challenge and one that cannot be safely combated with water treatment alone.

“Building owners and facility managers need to work proactively with their mechanical contractors to coordinate circulation programs,” continues Duncan. “An upgrade to smart water treatment technology can also help to effectively manage the vagaries in water conditions.”

“HydroChem strongly supports a structured risk management approach to the control of Legionella,” says Duncan proudly. “Our company has developed a range of resources including an online risk rating tool that analyses data collected from cooling tower systems and rates their performance. The resources assist not only our clients, but also the wider building sector.”

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