Formatted Title
Prediction of Ion Exchange System Treatment of Per- and Polyfluoroalkyl Substances Using Rapid Small-Scale Column Testing
Background/Objectives
Background/Objectives. In March of 2023, the Environmental Protection Agency announced the proposed National Primary Drinking Water Regulation of six PFAS compounds. The leading treatment technologies for the removal of PFAS are granular activated carbon (GAC) and ion exchange (IX) resin. Facilities required to install PFAS treatment systems need to quickly evaluate treatment technologies to meet the changing regulatory landscape. The rapid small-scale column test (RSSCT) can be used to compare media quickly under dynamic loading conditions and with less water than traditional bench-scale or pilot column testing. This test method was first developed to assess GAC treatment of VOC compounds. A set of RSSCT design equations are used to determine the ratio of small to large-column empty bed contact time and media particle size. The RSSCT has been applied to PFAS treatment by GAC but there is limited research on IX resin scale-up. This study bridges this gap in current research and demonstrates successful IX media performance using the RSSCT for the treatment of PFAS from a drinking water utility. The objectives of this study were to determine if the RSSCT method could be successfully applied to IX treatment of PFAS and if a correction factor is needed for accurate full-scale prediction.
Approach/Activities
Approach/Activities. ECT2 installed a drinking water treatment system in 2020 to treat PFAS-impacted groundwater with gelular polystyrene-based strong base IX resin. Data have been collected over the two-and-a-half-year operation of the system to monitor PFAS breakthrough from the IX contactors. Five PFAS compounds have been detected in the groundwater and compounds range in concentration from 1.0 to 150 ng/L. An RSSCT was conducted at ECT2’s R&D facility in North Carolina using 15 gallons of test water collected from the utility and 0.25 mL of IX resin. A sample of resin was collected from the same batch as was used at the site, mechanically ground, and wet sieved to a uniform size fraction for the RSSCT. The bench test took 10 days to simulate over three years of full-scale PFAS treatment.
Results/Lessons Learned
Results/Lessons Learned.
- The RSSCT was able to successfully predict breakthrough of all five PFAS compounds detected in the source water.
- A correction factor was not needed for any of the PFAS compounds when plotted on a percent breakthrough basis.
- These findings provide a basis for further RSSCT studies that include IX treatment of PFAS.
- Based on these findings, this is a promising test method that can be used to predict bed life of IX and drive system design decision making on the basis of cost, footprint, and changeout frequency.
- Additional testing with various source waters would provide greater confidence in full-scale system performance.