Cooling Tower Water Treatment FAQs
What is the purpose of a cooling tower system?
Cooling towers are designed to reject heat from open recirculating water systems by utilizing evaporative cooling. They help reduce water usage by recycling water and are the most efficient method for heat rejection in industrial and HVAC applications.
How does evaporative cooling work in a cooling tower?
Heat is picked up from the facility via cooling coils and transferred to a chiller. The heat then moves into a recirculating water loop, which flows to the cooling tower. There, water is sprayed and cooled by air, rejecting heat into the atmosphere. The cooled water is then recirculated.
What types of cooling towers are common?
- Natural Draft Towers: Large, chimney-like structures typically found at power plants.
- Forced Draft Towers: Smaller units using fans to move air, commonly used in commercial and industrial settings.
What is the typical water usage breakdown in a facility with cooling towers?
Approximately 70% of the total plant water usage goes to cooling towers, 20% to process use, and 10% to potable and other uses.
What are common applications for cooling towers?
- HVAC systems (e.g., in commercial buildings)
- Industrial process cooling
Why is filtration important in cooling towers?
Filtration removes particulates that could otherwise cause scale, corrosion, and fouling. Though not mandated, filtration is highly recommended to protect pumps, valves, and other system components.
What are the main treatment goals for cooling towers?
- Prevent scale and corrosion
- Control microbial growth (including Legionella)
- Optimize water use through cycles of concentration
What is “cycle of concentration” in cooling towers?
It refers to the number of times dissolved solids in the water are concentrated due to evaporation. Typical systems aim for 3–5 cycles. Higher cycles reduce water usage but risk scale or corrosion if not properly managed.
How is conductivity used to control cycles of concentration?
Conductivity probes monitor dissolved solids. When levels get too high, the system bleeds off water and replaces it with fresh water. This maintains the desired concentration range.
What equipment helps automate water treatment in cooling towers?
- Walchem Controllers
- Bleed Valves
- WTLink Modems
How can facilities increase cycles of concentration safely?
- Use automation for chemical feed and blowdown
- Soften makeup water
- Control alkalinity with acid feed
- Improve filtration
- Select better-quality makeup water (if possible)
What are common sources of scaling, corrosion, and fouling?
- Scaling: Calcium, magnesium, silica, and iron from hard water
- Corrosion: Especially in soft water systems or neglected areas like sumps
- Fouling: Dust, dirt, pollen, and organic material sucked in by the cooling tower
What is the recommended cleaning schedule for cooling towers?
At least once per year. More frequent cleanings may be required depending on environmental exposure and fouling potential.
What chemicals are used in cooling tower water treatment?
- Scale and Corrosion Inhibitor
- Oxidizing Biocide
- Non-oxidizing Biocide
What is microbiologically induced corrosion (MIC)?
A type of corrosion that occurs beneath bacterial biofilms. Bacteria excrete acidic byproducts that corrode metal surfaces beneath the biofilm.
Why are two types of biocide used?
Using both an oxidizing and non-oxidizing biocide helps prevent bacteria from developing resistance and ensures more thorough microbial control.
How is biocide feed optimized for effectiveness?
- Proper dosage based on system volume
- Attention to pH compatibility
- Sufficient contact time
- Automated controllers to manage dose and flow timing
What role do sensors and probes play in cooling tower treatment?
- Conductivity: controls cycles
- ORP: verifies oxidizing biocide levels
- PTSA: tracks chemical feed using fluorescent tracers
What are best practices for optimizing a cooling tower system?
- Know your water source
- Use automation for monitoring and alerts
- Install makeup and bleed meters
- Maintain pre-treatment equipment
- Conduct regular inspections and cleanings
- Collaborate with a water treatment provider