Legionella and Cooling Towers

With sadness we’ve been reading about the ever-growing number of people in the Bronx that have been infected with and died from Legionnaires‘ disease. Our hearts sincerely go out to those that have lost friends and family.

Cooling towers act as the radiator for large air conditioning systems. There has been little technological improvement over many decades in the industry and almost all manufacturers have built near identical designs. Traditional cooling tower designs do require considerable maintenance and can become environmentally unfriendly. This is because the water in the basin at the bottom is often exposed to sunlight that allows for the growth of algae, the primary food source for biological growth such as Legionella. This is compounded by stagnant areas in the basin where biological growth can multiply. The top-mounted fans cause drift emissions or mist to exit the tower at a rate where it commonly feels like it’s sprinkling outside when walking by the cooling tower. When people with lowered immune systems breathe in drift emissions that come from a cooling tower with high Legionella growth, outbreaks such as what we’re seeing now can occur. We published a white paper about this several years ago: http://www.towertechinc.com/documents/Legionella_Control_White_Paper_05072004.pdf

New York City is now faced with putting appropriate legislation in place to greatly reduce the potential for such an outbreak to happen again. The UK and Australia were among the first to put legislation in place relative to Legionella control with cooling towers several years ago. Their focus was on requiring owners to thoroughly clean their cooling towers every month or quarter, and that the government would oversee and enforce. Although every cooling tower owner needs to provide water treatment and routine maintenance as outlined in the manufacturer’s O&M manual, here’s the problem with that approach to solving the problem:

• It’s unrealistic to shut down the air conditioning system during summer months for cleaning without spending a lot more capital dollars for a redundant unit
• Maintenance departments are under staffed, and because it’s one of the hardest jobs and in a confined space, new legislation will require a lot of teeth to actually be enforceable
• It increases the burden to the local tax payers since now oversight is required to ensure the cleaning is consistently taking place per legislation
• It encourages the use of air cooled systems instead of water cooled, which often use nearly twice as much energy and can double the building’s cooling system carbon footprint

An Ounce of Prevention is Worth a Pound of Cure
There are two (2) key things that have to happen in a cooling tower before someone can become infected from the cooling tower:

1) Legionella has to grow inside the tower, and
2) the mist or drift from the water in the tower has to be transported to the person

If you eliminate either of those items, it’s near impossible for a person to get infected by Legionella from a cooling tower. Technology commonly exists today that can automatically greatly reduce and/or nearly eliminate both items above. As a more simple, manageable, and surer solution, perhaps legislation can focus on the following two (2) requirements instead:

• Must install a basin sweeper system (already offered by major manufacturers and after market providers) if the basin does not keep the water moving at least 3’ per second
o This turbulence makes it very difficult for Legionella to grow, and the cost is much less and more realistic than monthly to quarterly government mandated cleaning
• Mist/drift eliminators must be designed not to exceed 0.001% drift emissions per CTI standards
o This will reduce the amount of mist that can travel from the cooling tower by 50-80%, depending on what’s currently installed

If you’re reading this post, you probably already know that the Tower Tech modular cooling tower eliminates 100% of sunlight contact with the water so algae, the primary food source for biological growth like Legionella, doesn’t form. You already know the Tower Tech basin keeps the water moving at 5’ per second, without the need for a basin sweeper system, so Legionella has no hiding place. You already know Tower Tech towers have a drift emissions rate of 0.0004% per CTI standards so 82-90% of the drift or mist, as compared to conventional designs with top-mounted fans, is eliminated. That’s why a Tower Tech cooling tower is the surest way to eliminate the potential for Legionella. Additionally, readily available and cost effective technology exists that can easily be retrofitted into traditional designs (as described above) which can dramatically reduce the potential for Legionella without putting undue burden on local businesses and local government.

Cooling Tower Helps Eliminate Legionella

Cooling Tower Helps Eliminate Legionella

To see a specific example of how simply eliminating algae and keeping the water moving can reduce biological growth such as Legionella, see the last page of this case study:
http://www.towertechinc.com/documents/Buffalo_Case_Study.pdf

Legionella growth in under-maintained cooling tower designs that utilize open basins with stagnant zones and high rates of drift emissions can be a matter of life or death. Technology that can easily replace or be retrofitted into these designs is readily available and can save lives. Use the right technology and let’s all breathe easier.

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