Cooling towers continuously scrub bacteria, dust, pollen, insects, and other debris from the air during routine operation. Without good maintenance, including regular cleaning and disinfection, these contaminants can cause serious problems that reduce the life, efficiency, reliability, and safety of building HVAC systems.
Dirty cooling towers with fouled fill, plugged spray nozzles, or deposits blocking air flow do not cool as efficiently as clean ones, forcing fans and pumps to operate longer to maintain designated water temperatures. If the cooling tower is unable to sustain the optimal condenser water supply temperature, chiller efficiency will also be reduced.
Dirty, crusty cooling towers also present an ideal environment for biofilms, another term for slime, to form, and gain a toe-hold to infest the entire HVAC system. Biofilms are communities of surface attached microorganisms held together by a slimy microbial secretion. A wide range of problem causing microorganisms, including the Legionella bacteria that causes Legionnaires’ disease, can grow to high levels protected from biocide additions inside biofilms.
Biofilms are the root cause of serious problems in cooling tower systems including clogged piping, reduced heat transfer efficiency, microbial corrosion, and Legionella transmission. The buildup of debris and stagnant conditions in equalization lines, drains, side stream filters, and off-line equipment make these locations particularly favorable to biofilms and Legionella growth. Once established, biofilms are tenacious and difficult to remove completely, even when subjected to high levels of chlorine or other disinfectants.
OSHA recommends that cooling towers be cleaned and disinfected at least twice a year. More frequent cleaning and disinfection may be required if inspections show visible microbiological growth or an excessive buildup of debris, or as a remedial measure in response to positive Legionella or bacteria test results. New cooling tower systems or systems that have been out of service for an extended period (generally defined as > 5 days), should be cleaned and disinfected before startup to reduce Legionella risks.
Although the payback is significant, effective cooling tower cleaning and disinfection is a labor-intensive process that requires specialized processes, equipment, and expertise. The mechanical cleaning and disinfection procedures must be employed correctly to address problem areas and prevent damage. Aggressive cleaning and disinfection procedures using specialized cleaners are necessary to remove fill deposits and biofilms. And specific protocols may be necessary to accommodate systems that cannot be shut down for cleaning, or require Legionella remediation.
In addition, all work must be performed safely. Workers must wear the proper personal protective equipment (PPE) to avoid chemical and microbiological hazards. And specialized equipment may be required to safely access spray nozzles, air inlet louvers, and fill.
While often overlooked or performed incorrectly, routine cooling tower cleaning and disinfection is essential preventative maintenance to avoid problems in building HVAC systems and reduce Legionella risks. Using the services of a qualified company helps ensure this work is performed safely, following industry recognized procedures with supporting documentation. For more information, click here today!
Written by: Tom Worley