Water Treatment Company Wisdom: Bioslime in a Cooling Tower is Bad

Posted by Greg Frazier on Fri, Jul 24, 2015 @ 05:56 PM

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Cooling towers are notorious for growing things; especially microscopic things… They are warm and moist. They have areas that get a lot of sunlight and other areas that kept fairly dark. Whether it's algae or bacteria, it's no wonder that cooling towers provide the perfect environment for all kinds of little organisms to proliferate. In fact, an improperly treated cooling tower can act like a giant Petri dish.

So what's a couple hundred million microscope critters living in your tower mean anyway?  It's not such a big deal, right? A little bleach will keep them at bay, right?


The truth is that those little organisms can be much more of a liability than you think. Most facility operation managers are well versed in or have at least heard of the dangers of waterborne pathogens, like legionella, emanating from their cooling towers; it is why most facility managers find water treatment companies that provide water treatment services for their main water systems. While legionella presents a worst case scenario, it is not the only bug that can cause major operational issues in a cooling tower, and is why proper tower water treatment is so important to the overall operational health of a cooling tower system.

IMPORTANT NOTE: If you haven’t heard yet, ANSI/ASHRAE Standard 188-2015, Legionellosis: Risk Management for Building Water Systems was recently released and it has major potential impacts on how building owners need to think about legionella in their water systems. Click this link if you would like read our previous post about Legionella and ASHRAE Standard 188.

Almost all bacteria have one thing in common... they really, really, really want to live!  And they will do whatever they can to protect themselves.  One of the clever things they do, especially in water, is to band together and produce a slimy matrix that covers them while they breed and grow. This material is actually quite resistant to most biocides. It is technically called biofilm, but many people also refer to it as bioslime (because hey, it’s slimey!) and if you have it in your tower, you probably have other issues.

One thing about bioslime that many people do not realize is that it acts as an incredibly good insulator. When you get bioslime on an active heat transfer surface, like on inside surfaces of the tubes of a chiller, it becomes harder and harder to produce chilling.  In fact, a bioslime layer that is less than one fifth of one millimeter thick can impede heat transfer by more than 10%! That means that you will have to use more energy to produce the proper levels of cooling. In a larger chiller system that could mean tens of thousands of dollars in wasted energy... all because of a little slime in the towers.

Water Treatment Fun Fact: There are no issues with bioslime in boiler water treatment. The heat inside a boiler is typically way too hot to allow biological growth.  The kind of issues that plague boilers are usually scale and/or corrosion related.

Check out this short video to see what bioslime is all about:

So what should I do about bioslime in my cooling tower?

The most important thing you can do is keep your cooling tower clean and make sure that your water treatment professional is aware of any issues that you see. Sometime it might not seem like you have a problem, but the best way to tell in not with your eyes. Even if the water looks completely clear, put on a rubber glove and run your hand over part of the cooling tower basin. If the basin feels "slick" or "slimy" you almost certainly have bioslime in your tower.

Options for removing bioslime vary from system to system, but it is almost always a good idea to get your water treatment professional involved and possible even employ the help of a reputable HVAC Cleaning company. Ongoing proper water treatment is the only way to prevent bioslime from ever forming. Your water treatment service provider should be able to describe their methods for keeping biological growth under control in your cooling tower.

Current industry standards dictate the use of a three chemistry system for cooling towers:

  1. An oxidizing biocide – kills microorganisms by destroying their cell walls and oxidizing protein within the organism. Chlorine is an example of an oxidizing biocide.
  2. A non-oxidizing biocide – kills by ways other than oxidation, including interference with cell metabolism and structure; more like a poison. DBNPA and isothiazoline are non-oxidizing biocides.
  3. A corrosion inhibitor – provides protection to the metal surfaces against corrosion. Especially helps counteract the corrosive properties of the oxidizing biocide.

This standard water treatment protocol for cooling towers is often referred to as a “dual biocide program” because to the two biocides used, and it is still considered the best defense against microbiological growth in a cooling tower.

EcoSafe powered by Smart ReleaseThe latest advancements that have been made in the standard dual alternating biocide program doesn’t actually change the chemistry much at all, but instead changes the way in which those chemicals are fed into the cooling tower system. Most water treatment companies rely on liquid chemicals which are pumped into the open condenser system via chemical metering pumps.  Up until now, the benefit to this type of system was precise control over the dosage rates of each chemical via highly calibrated, electronic metered pumps.

Today, there are highly improved solid feed delivery systems that use dry chemistry to achieve the same level of control without the headaches and safety issues of liquid chemistry. These newer types of solid feed systems, like EcoSafe Solid Feed System powered by Smart Release, have all but completely revolutionized the way that we treat cooling towers today.

If you would like more information about what to do if you have bioslime in your cooling tower, please do not hesitate to call us! If you would like to learn more about how to navigate the new ANSI/ASHRAE Standard 188 and implement its core philosophies throughout your facilities, please follow the link below to our brief questionnaire.

Thanks for reading!

Learn More about our ASHRAE Standard 188 Legionella Consulting Services


Water Treatment Company CTClarity Water Technologies is known throughout the east coast as an innovative industrial/commercial water treatment company. To put it simply: We make commercial HVAC and industrial process machinery last longer and run more efficiently, with less fuel and less downtime, by chemically treating the water that runs through it. Typical systems that we treat include steam boilers, chillers and cooling towers; however, we also offer advanced wastewater, glycol services, odor control and fuel treatment services. We are one of Northeast’s most trusted Legionella remediation companies and are widely accepted as one of the best consulting firms to establish best practices for the implementation of ASHRAE Standard 188 - Legionellosis: Risk Management for Building Water Systems.

As water treatment experts, we know that chemical treatment is only part of what makes a mechanical system operate at peak performance. The other part of the equation is proper physical cleaning and maintenance.  Today, Clarity offers one of the most reliable and effective HVAC cleaning services available throughout NY, NJ, CT, DE and PA. Clarity is a NADCA Certified HVAC Cleaning Service Company. Over and above physical equipment cleaning services, our team also offers iron removal, on-line cleanings, chlorine dioxide disinfection, Legionella remediation and the installation of the EcoSAFE Solid Feed System—one of the most advanced water treatment systems for Cooling Towers in the world! Call us today for a free estimate on your next project or click the link above for more information.

Greg Frazier water treatment expert in NYCNew York City Water Treatment Consultant, Greg Frazier is an expert in Industrial Water Treatment and is currently the Managing Partner of Clarity Water Technologies, one of the best Water Treatment and HVAC Cleaning Companies in the North Atlantic Region of United States. Mr. Frazier has over 19 years of Industrial Water Treatment experience and holds a degree in Chemical Engineering from the University of Tennessee. Clarity Water Technologies specializes in comprehensive water treatment services. Clarity's service goes far beyond administering Cooling Tower Water Treatment chemicals - it also includes Cooling Tower Maintenance and HVAC Cleaning Services.

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