Industry is currently consulting with the NSW Government on the introduction of new cooling tower regulations which aim to reduce future outbreaks of Legionnaires' Disease. Aqua Technical Services president, Frank Rosa, believes new laws may not be the best solution.
Everyone wants to introduce measures to prevent Legionellosis but the problem here is that it diverts attention away from the real problem – water supply.
This is not to say the water is at fault, only that legionella are aquatic organisms, they do not spring up spontaneously. Yes, if a disseminator gets overloaded with the bacteria the air-borne droplets will carry to great distances to inoculate other locations, causing illness or death to an untold number of victims.
The City of Sydney has 1,200 registered cooling towers in the CBD, but the number of systems regulated under the Public Health Act, including potable hot water systems, humidifying systems, warm water systems and water cooling systems, remain unknown but these are all known sources of legionella amplification and dissemination.
It would be a safe wager to say the unknown sources far outnumber the known sources, so the focus (illness prevention) is obscured and the public vulnerable.
The truth is that risk management plans, chemicals and magic gadgets focused on cooling towers, are a fruitless endeavour. We are so focused on that fish that we are neglecting the approaching great white below, to our dismay.
We need to address the inoculator, the city mains, with proper filtration as it enters the facility. The water supplier cannot do it. The complexity of the mains makes it near impossible, even if the mains are pigged.
We must also be cognizant of issues that adversely affect decisions; a primary one is the Laminar Flow of water. One cannot address biofilm within piping easily because ature will not allow it. To attempt it will increase operating costs without a significant improvement in performance.
One must remove the moving “cats and dogs” – addressing viable legionella with chlorine at 0.5 ppm, within the building supply with lower filtration if needed, depending on end use. The make-up water to open condenser water systems need additional filtration, as do condenser sumps.
Sumps can be filtered using sand, as long as we remember to properly “fluff” the sand weekly. Remember, sand is a perfect media for bacterial amplification as anyone with a swimming pool can attest. Once biofilm takes hold, to remove it takes more effort than removing fleas and ticks from wild lions.
Air-screens, for open condenser systems, have proven valuable in helping to maintain the internal environment of open condenser loops free of debris. Chemical use, to minimise potential for illness, is the last barrier.
As for potable H/W loops (110F/43C), we are faced with a triple “whammy”. Heat destroys effective oxidisers (halogens and Ozone) rapidly, makes for easy bacterial amplification and turning a non-pathogen into a killer. UV can be used, as long as one understands its limitations – it does not sterilise. As for Copper/Silver systems, they cannot be defended in a court of law and magnets, electro-transmorgrifiers and such won’t even be mentioned.
What will it take to get on the ball and address the issue? We need to take preventative measures and take the proactive steps outlined on the June 2016 issue of CCN (page 17).
We must take the torch and run with it. Remember, we all use the same water. ?
About the Author
Frank Rosa is the president of Aqua Technical Services and is an internationally renowed chemist and biologist with extensive experience in the water treatment of potable and HVAC systems. Rosa is also an ASHRAE Life Member and former chapter president.