OCWD Completes Phase I of a PFAS Pilot-Scale Treatment Study

  • by Orange County Water District
  • Jun 23, 2021

The Orange County Water District (OCWD) completed Phase I of a PFAS Pilot-Scale Treatment Study of water filtration adsorbents to remove per- and polyfluoroalkyl substances (PFAS) detected in local groundwater supplies. The final comprehensive report is available on OCWD’s website.

The nation’s largest PFAS adsorptive media pilot test, the project evaluated 14 treatment media to identify the best and most cost-effective treatment technologies to restore local groundwater quality and meet drinking water regulatory requirements.

The PFAS pilot project was initiated due to the critical need to restore the local drinking water supply, after dozens of local drinking water wells were taken out of service following the lowering of California’s drinking water Response Level (RL) advisories for two legacy PFAS chemicals found in water supplies in many parts of California and the nation. The occurrence of these chemicals has impacted 11 local water agencies in Orange County who have removed selected wells from service that provide water for up to 800,000 individuals annually.

Beyond the immediate engineering scope, key research components of the OCWD PFAS Treatment Study addressed knowledge gaps for treatment of PFAS in water supplies and identified novel adsorbents as having great promise for PFAS treatment. To the project team’s knowledge, the pilot is the nation’s largest PFAS adsorptive media pilot test with respect to the number of treatment media that were evaluated to remove PFAS: 14 media including granular activated carbon (GAC), ion exchange (IX), and alternative (novel) adsorbents (which are not classified as GAC or IX and only recently commercially available). Other project components included laboratory-scale testing of GAC and alternative adsorbents for a range of groundwaters, nanofiltration laboratory-scale testing, lead-lag system modeling to project full-scale treatment system performance, and cost estimating. The purpose was to identify cost effective treatment technologies to restore local groundwater quality and meet drinking water regulatory requirements.

The pilot testing, completed in February 2021, demonstrated that all adsorbents evaluated can successfully remove PFAS to meet California drinking water advisories. Based on these results, OCWD is initiating a Phase II PFAS Pilot-Scale Treatment Study to continue identifying promising adsorbents for wellhead treatment systems, and to serve as an ongoing research program that supports the water industry more broadly.

The effort to address PFAS in the OCWD service area is highly time sensitive as the actions by Orange County water agencies to take dozens of drinking water wells out of service temporarily resulted in increased reliance on costlier treated surface water supplies imported from Northern California and the Colorado River. The cost of purchasing imported water may place a burden on ratepayers of up to $20 per month and additional wells are likely to be taken offline as testing is expanded.

Local water suppliers can rely on increased imported supplies in the near-term, but OCWD and its water retailer partners are working quickly to implement new PFAS treatment systems, planned to come online in one to two years, using information from the described study and research. Effective PFAS treatment will allow the local groundwater to once again be used as the most cost-effective, reliable source of drinking water to the residents and businesses in north and central Orange County.