In this fourth and final installment of our series on In August 2025, Essential Water Quality Management to Safeguard Health and Infrastructure, we will explore key strategies for cooling tower treatment to protect your investment. Central Harlem faced a serious public health crisis when an outbreak of Legionnaires’ disease sickened over 100 individuals and claimed seven lives. Investigations ultimately traced the outbreak to a hospital and molecular analysis confirmed a genetic match between the patient samples and strains found in two contaminated cooling towers.
This incident underscores the critical importance of effective cooling tower water treatment and monitoring strategies to prevent microbial proliferation and safeguard public health.
5 Key Strategies for Cooling Tower Water Treatment
Effective cooling tower water treatment combines physical water treatment methods with continuously monitored chemical treatment to protect assets and to prevent contamination.
1. Side-Stream Filtration
Side-stream filtration removes suspended solids by filtering a portion of the recirculating water – typically 3-10%. Removing suspended solids results in better heat transfer, reduced maintenance, and improved chemical efficiency. With fewer solids in the system, chemical treatment will perform better, reducing the need for high dosages. Filtration should be employed for systems with high turbidity or if biological control is not achieved.
2. Makeup Water Softening
Makeup water may need to be softened to prevent scale formation in the cooling tower system. Scale acts like insulation, reducing heat transfer efficiency and increasing energy costs. Ion-exchange softeners replace the scale-forming calcium and magnesium ions with sodium. With fewer hardness ions, less scale inhibitors and acids are needed to control pH and prevent deposits. Soft water also allows the cooling tower to operate at higher cycles of concentration, resulting in less frequent blowdown. Soft water can be more corrosive if not properly managed which is why partial softening or blending methods are employed.
3. UV Disinfection
UV disinfection may also be employed to further mitigate Legionella risk. This chemical-free method of disinfection disrupts DNA replication, preventing pathogens from multiplying. Unlike biocides, UV does not introduce chemicals or form disinfection byproducts. While UV provides continuous disinfection, it does not leave a residual which is why chemical treatment is often necessary.
4. Chemical Treatment
Chemical treatment must be precisely managed to avoid equipment damage and ensure safety. Chlorine and bromine are common oxidizing biocides used to kill bacteria. However, chemical dosing must be properly controlled to prevent corrosion. Automated dosing systems maintain chemical levels and reduce human error.
5. Monitoring and Compliance
According to ASHRAE Standard 188, facilities must maintain a Water Management Program that includes monitoring and validation strategies for building water systems.
Routine monitoring should include:
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Makeup Water: Total Hardness, Alkalinity, Conductivity/TDS, and pH
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Basin Water: Temperature, pH, Conductivity, and ORP
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Weekly: Dipslide Testing for Total Bacteria
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Quarterly (Minimum): Legionella Sampling, with More Frequent Testing During Warmer Months
Why It Matters
Outbreaks of Legionnaires’ disease serve as a reminder that proper maintenance of building water systems is essential. By integrating physical water treatment with tightly controlled chemical treatment, facility managers can prevent microbial growth while protecting plumbing and HVAC assets.
Consistent monitoring and adherence to industry standards not only protects infrastructure but also prevents waterborne illnesses.
Previous Articles in This Series:
- Essential Water Quality Management to Safeguard Health and Infrastructure
- Unintended Consequences of Chemical Disinfection – Health Effects
- Protecting Your HVAC Operating Equipment Assets Requires Proper Water Quality Management
This series is written in partnership with the Water Solutions Group (WSG). WSG offers innovative water quality solutions. Contact the team for a site assessment or view our extensive line card to learn more.
Water Solutions Group is a separate division of the R.L. Deppmann Company created to provide end users and engineers with a valuable resource in efforts to improve water quality. Proper water quality management protects the equipment, operations, occupants, and environment. Water quality should be considered at the time of design to ensure safe and efficient operating systems. Our intimate knowledge of water systems positions Water Solutions Group to be the ideal partner when evaluating operational issues that may arise because of poor water quality.