Do you think that your cooling tower is dirty? If you have biofilm in your cooling tower, bad things are already happening. For certain, your HVAC system is losing efficiency and you are losing money; but it is possible that there are bigger issues lurking just beneath that slime.
What is Biofilm?
Sometimes also referred to as "bioslime," biofilm is actually a matrix of polysaccharides and proteins that is secreted by microorganisms that allows them to adhere to a surface and protect themselves from elements that may harm them. Scientists call this matrix "Extracellular Polymeric Substances" or EPS, but if you've ever felt it, you might just call it "slime."
Many biofilms have some interesting properties that make them something that you should be concerned about, especially in a cooling tower. Here is a short list:
1. Biofilm has incredible insulating properties, meaning that it greatly impedes heat transfer. In fact, in the case of a cooling tower, biofilm impedes heat transfer even more than scale deposition does!
2. Biofilm is produced by microorganisms. They produce the biofilm so that they thrive within or underneath it, and some of these microorganisms can be quite nasty. Some sulfite reducing bacteria can cause significant corrosion in your HVAC system. Legionella in a cooling tower produces a biofilm to protect itself; and legionella is the bacterium that is responsible for Legionnaires’ disease, a nefarious and potentially deadly form of pneumonia.
3. Due to their physiochemical properties, biofilms are extremely resistant to biocides. This means that simply increasing the amount of biocide in your water treatment is usually not enough to disinfect your cooling tower.
Want to learn more? Check out this awesome biofilm explainer video:
The Cost of Biofilm in Your Cooling Tower
While every situation and cooling tower system is different, we can make some approximations as to what not getting rid of the biofilm in your tower system will cost you.
1. Loss of efficiency - As I mentioned earlier, biofilm is an amazing insulator. If biofilm takes hold in your chiller tubes you will lose efficiency. A biofilm layer that is less than one fifth of one millimeter thick can reduce efficiency by more than 10%! In a 1000 ton chiller system that could mean the loss of tens of thousands of dollars in wasted energy.
2. Potential serious damage - Some biofilms are caused by sulfite-reducing or iron-depositing bacteria. These types of bacteria can destroy steel. We have seen severe cases where sulfite-reducing bacteria have destroyed 1 inch thick steel tube plates of chillers that were in service for less than 18 months. The cost to the facility was a complete re-tubing of two chillers. The facility was not prepared for this extreme maintenance cost or consequent down time.
3. Unnecessary and profound liability - Biofilms in your tower could indicate that you have a far more ominous issue like a water-borne pathogen. Legionella is one of the most ominous in this category. Legionella bacteria are responsible for causing Legionnaires' Disease, a potentially deadly form of pneumonia. If you tower is located in an area that is close enough to send mist into a populated area, you have a potentially huge liability on your hands. Anyone that is immunocompromised is at a much greater risk of developing Legionnaires' Disease from an infected cooling tower. These include the very old, the very young or someone who is already fighting an infection. Facility operators that take care of cooling towers at senior living centers or hospitals should be on constant alert for Legionella in their systems.
How to Remove Biofilm from Your Cooling Tower
There are many options to consider when fighting biofilm in your cooling tower system. Usually it is not enough to merely increase your biocides; and in some cases, that could actually cause more harm than good. While preventing biofilm from forming in the first place is always preferable, there are a few steps that you take if you feel that you have a problem.
1. First, determine if there might be a problem. Just because you cannot see a biofilm, does not mean that it doesn't exist. Even if your cooling tower water is completely clear, you could still have an issue. You can try putting on a rubber glove and running your hand just under the water line in your cooling tower's basin. If it feels slick or slimy, you have probably have a biofilm problem.
2. Let your water treatment service provider know that there is potential issue. Many times they can adjust the water treatment program to avoid further problems. They may also be able to perform a full system disinfection for you.
3. Many times biofim needs to be physically disturbed, or broken up, to be effectively destroyed. That means a physical cleaning could be in order. Contact a reputable HVAC Cleaning Company in your area to evaluate your specific situation. Make sure they follow all safety protocols. Not sure if you have the best HVAC Cleaning Company for the job? Check out our free eBook: Top Five Tips for Choosing the Best HVAC Cleaning Company
4. There are advanced methods now available to make the disinfection process closer to 100% effective. Some top HVAC Cleaning Companies and some innovative Water Treatment Service Companies have these tools at their disposal. One such method is the use of chlorine dioxide, which has proven to be one of the best and least destructive methods of advanced disinfection available; but make sure you educate yourself on what type of chlorine dioxide disinfections are available. Some methods of chlorine dioxide disinfection work much better than others, some methods are better and safer than others; and generally speaking, the best way to administer chlorine dioxide into your system is to have your vendor generate it on-site at your facility.
As with all things having to do with advanced water treatment or HVAC cleaning services, if you have any questions or would like assistance at your facility, please do not hesitate to call us.
Next Step: We are conducting free on-site surveys throughout the Northeast! This type of in-depth system review could help save you thousands of dollars in operating costs. If you would like to learn how you can receive a free comprehensive HVAC System Survey and Analysis of your facility's HVAC System, please use the link below.
Thanks for reading!
Greg Frazier is an expert in Industrial Water Treatment and is currently the Managing Partner of Clarity Water Technologies, a top Water Treatment and HVAC Cleaning Company in New York. He has over 18 years of Industrial Water Treatment experience and holds a degree in Chemical Engineering from the University of Tennessee.