Water quality impacts on sorbent efficacy for per- and polyfluoroalkyl substances treatment of groundwater |
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| Authors: | Nicholas T Hayman Jessica E Carilli Yina Liu Michael R Shields Lewis Hsu Robert George |
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| Institution: | 1. Naval Information Warfare Center Pacific, San Diego, California, USA;2. Department of Oceanography, Texas A&M University, College Station, Texas, USA
Geochemical and Environmental Research Group, Texas A&M University, College Station, Texas, USA;3. Geochemical and Environmental Research Group, Texas A&M University, College Station, Texas, USA |
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| Abstract: | Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic compounds that have emerged as chemicals of concern in drinking water and groundwater. Typically, such waters are treated to remove PFAS by passing the water through a bed of sorbent material (e.g., activated carbon and anion exchange resins AIX]). However, the efficacy of these sorbents varies depending on the types and concentrations of PFAS, in addition to water quality conditions such as organic matter content and conductivity (ionic strength). The choice of sorbent material to effectively treat PFAS in complex natural waters will, therefore, depend upon site water quality and PFAS conditions. To help inform these decisions, a series of evaluations using a rapid small-scale column test approach was conducted with two sorbent materials (a granulated activated carbon GAC] and an AIX), individually and combined, under conditions where conductivity, pH, and organic carbon concentrations were varied in a semifactorial approach. Artificial groundwater batches were prepared to meet these test conditions and spiked with six PFAS compounds (perfluorobutane sulfonic acid PFBS], perfluorobutanoic acid PFBA], perfluorohexane sulfonic acid PFHxS], perfluorohexanoic acid PFHxA], perfluorooctane sulfonic acid PFOS], and perfluorooctanoic acid PFOA]), passed through small columns packed with ground sorbent material for ～30,000 bed volumes of water for single sorbent treatments and ～20,000 bed volumes for combined sorbent treatments, during which samples of effluent were captured and analyzed to quantify breakthrough of PFAS from the sorbent materials over time. AIX was found to be more effective than GAC at removing the tested perfluoroalkyl sulfonic acids (PFBS, PFHxS, and PFOS), but GAC was similarly or more effective than AIX at removing perfluorocarboxylic acids (PFBA, PFHxA, and PFOA) under high conductivity conditions. Overall, the efficacy of AIX at removing PFAS was more strongly impacted by organic carbon and conductivity than GAC, while pH had less of an effect on either sorbent's efficacy compared to the other test conditions. |
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