Now Available: On-Demand Webinar–Alternative Water Treatments for Cooling Towers

On Demand Webinar and Slides


Alternative Water Treatments
for Cooling Towers 

If you missed our last webinar, "Alternative Water Treatments for Cooling Towers," and would like to watch a recording of it or share it with colleagues, you can access it in the Emerging Building Technologies YouTube Channel. You can also view the presentation slides.

Thanks to presenters and participants for their thoughtful questions, some of which are answered below.



Q: Do these systems control for Legionella?
A: Yes. As part of regular maintenance, all systems were tested for Legionella pneumophila and found to be clear. The AWT systems all control for bacterial growth, including Legionella, E. coli and other pathogens. At the conclusion of the assessments in Denver, NREL conducted follow-up water quality testing in 16 cooling towers and found no Legionella bacteria.

Q: The average GSA water rate of $16.76 seems high. Does this include sewer charges?
A: Yes, payback calculations that demonstrated payback under 3 years for all four AWT systems assumed a combined water/sewer rate of $16.76/kgal, GSA’s average. GSA has combined water and sewer rates that are as high as $29/kgal.

Q: Is internet connectivity required for any of these systems?
A: All of the systems run effectively without internet connectivity, though facility teams noted that for some of the technologies, connectivity could improve performance by allowing for remote monitoring and control by the technology’s vendor or a licensed distributor.

Q: How hard was the water at the testbeds?
A: Both testbeds typically have moderately hard water (90 to 110 ppm), though the Denver Federal Center has recently seen levels as high as 200 ppm. These AWT systems are designed to work with a range of water hardness.

Q: When do you need to consider a side-stream filtration system?
A: They are particularly helpful for open cooling towers, which are prone to collect dirt and debris. When installing a new cooling tower or doing a major renovation, also consider adding a tower sweeper to deal with sediment that collects at the bottom of the basin. In Region 8, side-stream filtration is now standard operating procedure.

Q: Are all four systems recommended?
A: Yes. Prioritize cooling towers with higher run times and electricity rates. Performance at the test beds was comparable in terms of water savings, water quality, cooling-tower cleanliness, and payback. Note that AWT systems rely on proprietary technology that is offered by a single vendor. In selecting an AWT technology, get estimates and choose the most cost-effective system for your location. Consider ongoing maintenance requirements and costs in your selection.