Colorado School of Mines
Raised in rural North Carolina, Conner received his undergraduate degree in Environmental Engineering from North Carolina State University in Raleigh, North Carolina. After an REU at Colorado School of Mines with Dr. Chris Bellona, he moved west joining the Bellona lab in the summer of 2017 to begin his PhD. His research is focused on the removal of PFAS using activated carbon technologies at contaminated sites in Colorado. Other research interests include membrane technologies and potable reuse. Outside of research Conner enjoys spending time in the beautiful outdoors that Colorado offers."
Removal of Per- and Polyfluoroalkyl Substances using Super-Fine Powdered Activated Carbon and Ceramic Filtration Compared with Granular Activated Carbon
Per- and polyfluoroalkyl substances (PFASs) are emerging contaminants found in numerous aquatic systems across the United States and other countries. Numerous PFASs have been quantified in municipal drinking water supplies serving as an exposure route for city residents. Of the hundreds of PFASs that are currently known and studied, perflurorooctane sulfonate (PFOS) and perflurorooctanoic acid (PFOA) have received the most attention due to their relatively common occurrence in the environment, recalcitrance in treatment and associated human health concerns. The USEPA recently developed a health advisory limit of 70 ng/L for PFOS and PFOA combined or separate in 2016. Perfluoroalkyl acids (PFAAs) such as PFOA, PFOS are noted for being poorly removed by conventional drinking water treatment processes.
Adsorption onto activated carbon has become the most commonly applied approach for the removal of PFAAs as well as other PFASs. Past research has demonstrated that while granular activated carbon (GAC) is effective for removing long-chained PFAAs, the removal of shorter-chained PFAAs and PFASs is more challenging. Super-fine powder activated carbon (SPAC) may offer advantages over GAC due to a smaller particle size and increased quantity of larger pores that are more conducive to PFAS adsorption.
The purpose of this study was to perform a side-by-side comparison of GAC and SPAC coupled with microfiltration for PFAS removal from contaminated water using continuous flow systems.
The effectiveness of GAC and SPAC in removing PFASs was first evaluated by performing experiments with contaminated groundwater. SPAC adsorption experiments were conducted for 72 hours alongside a long term GAC pilot study to evaluate PFAS breakthrough. Further experiments were subsequently conducted to determine breakthrough mass loading for multiple PFAAs and SPAC. To do this, the mass of PFAS delivered to the SPAC was increased by using water collected from a fire fighting training area that had orders of magnitude higher PFAAs (and other PFAS) levels than the contaminated groundwater. Comparison of GAC and SPAC adsorption capacities indicate that SPAC could be more than 400 times more effective for the removal of PFAAs although additional work is required to evaluate individual treatment technology costs. The adsorption performance of GAC and SPAC in relation to PFASs was found to be a function of adsorbent size, pore content and PFAS chain length.
Experiments run using SPAC and contaminated water from the fire-fighting area were run using a ceramic membrane system that filtered out the adsorbent SPAC and returned to the adsorption tank. Results demonstrated that the performance of the SPAC when operated under constant flux conditions exhibited minimal fouling despite a large volume of contaminated water being treated.
The removal of PFASs by water utilities using activated carbon technologies will have increasing importance in the future if more stringent regulatory levels are introduced. Continued efforts in lowering treatment costs while increasing short chained and intermediate PFAS removal performance will be critical steps in future studies.