Perfluoroalkyl substances (PFASs) such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are a group of contaminants of great concern. EPA has set a lifetime drinking water health advisory limit of 0.07 µg/L for [PFOA] + [PFOS]. In addition some PFASs other than PFOA and PFOS have shown higher toxicity in aquatic organisms. Among the treatment processes, adsorption by activated carbon (AC) and ion exchange (IX) resin has proven to be promising. Although adequate data have been reported for the adsorption of PFOA and PFOS, much less information is available for other PFASs. Also, PFASs concentrations used in studies were often much higher than their levels in the environment. Therefore, further studies are needed to investigate the application of adsorption in treating different PFASs under environmentally relevant conditions.  In our study, the efficacy of AC and IX resin in treating PFAS impacted groundwater is investigated. Three groundwater samples with different PFASs levels were used. Rapid small-scale column tests (RSSCT) are designed to simulate the performance of 1 MGD pilot scale treatment system. The treatment performance of five types of ACs and two IX resins is compared by plotting breakthrough curves. Surface properties of ACs on PFASs adsorption were studied by analyzing surface area, pore size distribution, oxygen content, and surface charge.  PFASs including perfluorobutanesulfonic acid (PFBS), perfluorohexanoic acid (PFHxA), perfluorohexanesulfonic acid (PFHxS), perfluoroheptanoic acid (PFHpA), PFOS and PFOA were found in the groundwater samples with combined PFOA and PFOS concentration of ~40, 100 and 3000 µg/L, respectively. In the experiments, bituminous coal based ACs show higher capacity than coconut shell based AC, which is likely due the elevated surface area and mesopore/macropore volume. In addition, selective adsorption of PFASs is observed: breakthrough of short chain PFBS and PFHxA is observed earlier than PFASs with longer chain; perfluorosulfonic acids are more susceptible to AC adsorption than perfluorocarboxylic acid with the same chain length (e.g. PFOS and PFOA). IX resins generally show better performance in removing PFASs than all the tested ACs. However, they have low affinity in treating PFHxA.  <br/>To obtain reliable design specifics, RSSCTs designed using constant diffusivity and proportional diffusivity will be compared with each other. We expect to get the results in the coming month.

Removal of perfluoroalkyl substances (PFASs) in groundwater using activated carbon and ion exchange resin: Column test

2019 Fall National Meeting

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