In a recent interview with WaterWorld, Carollo’s National PFAS Lead, Rosa Yu, and Highlands Ranch Water’s Director of Operations, Peter Bong, discussed findings from a pilot-scale study on PFAS treatment. The conversation, recorded at this year’s AWWA ACE conference, explored how the Colorado utility is evaluating treatment strategies that balance technical performance with cost-effectiveness.
Testing GAC-Capped Filters for PFAS Removal
Highlands Ranch Water serves about 105,000 residents in the southwest Denver metro area, with water demands that range from 8 mgd in winter to 40 mgd in summer. While PFAS levels in their system are relatively low (between 4 and 8 nanograms per liter), pending regulations make treatment essential.
The pilot tested whether existing particle filters could be modified with granular activated carbon (GAC) to also remove PFAS, reducing the need for a costly new adsorber facility. “The plan was to meet filtration needs while gaining PFAS removal capacity in the same unit,” Rosa explained. Peter added, “If we could modify our existing filters to do both… that’d be great! Less grey infrastructure to build, less money to spend.”
PFAS Removal: Results and the Path Forward
The results showed that while GAC-capped filters do remove PFAS, their effectiveness is short-lived, requiring media replacement every six months, which is too frequent to be cost-effective. “The GAC filter does provide some PFAS adsorption capacity, but not for long durations of time like we’d expect for adsorbers,” Rosa said.
With that in mind, the utility is now exploring alternative approaches, including traditional adsorbers, blending water sources to dilute PFAS, and adding powdered activated carbon (PAC). Carollo is conducting an alternatives analysis to help determine the most practical and resilient path forward. “Our approach is not relying on one single process, but instead taking a multi-barrier approach,” Rosa emphasized.
PFAS Control Options: Lessons for Other Utilities
While PFAS levels and water quality conditions vary from system to system, Peter believes this process can be a model for others. “These are the options—what’s more likely to work, what’s less likely to work, what’s more costly, what’s less costly,” he said. “We can’t have a bad day at the treatment plant… we want those two steps to ensure compliance every day, 24/7, 365.”
Watch the full WaterWorld interview with Rosa and Peter below to hear more about the pilot and its implications for PFAS treatment in surface water systems:
