Challenge
A global hyperscale data centre customer was looking to operate their cooling water system without continuous chemical dosing.
Solution
Evoqua worked closely with the customer’s engineering team to find the solution that would best fit their needs. Ultimately, a combination of media filtration and ultraviolet (UV) was selected and installed.
Evoqua‘s Vortisand microsand media filter technology was chosen for the cooling tower‘s side stream filtration, 5% of total flow. Its unique ability to generate cross-flow patterns across the surface of the media allows for higher filtration rates while preventing fouling and channelling. The backwash cycle requires 40% less water for cleaning compared to other media filters. Fourteen Vortisand VC-50 models, each filtering 50gpm of water, treat multiple data centres at one facility.
According to ASHRAE Standard 550-98, 0.001in of fouling in cooling towers equals 10% increase in energy consumption. Due to the Vortisand‘s superior performance for submicron filtration, total suspended solids (TSS) of the cooling water has been reduced to 1mg/L. Less build-up of small particles under 5 micron in size on heat exchanger equipment allows for increased energy efficiency and less maintenance overall. Habitat/food source for Legionella and other harmful bacteria is also significantly reduced.
Finer filtration also enables UV disinfection to do its job more effectively. Particles are not accumulating and blocking the UV from penetrating the microbes.
Evoqua‘s ETS-UV disinfection system technology was installed to treat the cooling tower‘s full stream to reduce microbial growth. Less biocide/chemical treatment is necessary as a result. Unlike chemical disinfection systems, organisms do not demonstrate a tolerance or resistance to UV light. Additionally, the water cannot be overdosed.
Indeed, the ETS-UV disinfection system has been so successful that this customer has over 80 UV systems installed at over 30 different data centre locations throughout the USA.
Results
The customer has seen dramatic results by combining Vortisand microsand filtration and ETS-UV disinfection including:
- Payback in 13-16 months
- 10-17% reduction in energy usage
- Switch to intermittent biocide (every 13 weeks is typical) and continuous UV disinfection will use 75% less biocide
- 40% reduction* in water consumption from efficient backwash (*compared to traditional sand filtration)
- 50% reduction in cooling tower maintenance
