Emerging Contaminants Summit

Spring 2020

StudentCompetitionliuCharlie Liu
PhD Student
Colorado School of Mines

Charlie is passionate about making positive impacts through community work and meaningful research as a PhD student in Environmental Engineering at the Colorado School of Mines co-advised by Dr. Christopher Bellona and Dr. Timothy Strathmann. He currently works extensively with various remediation methods for per and polyfluoroalkyl substances (PFAS) including GAC and membranes in pilot scale studies. These studies involve GAC remediation in a locally impacted city in Colorado as well as PFAS rejection with nanofiltration membranes for a DoD site. He also investigates factors influencing membrane performance under various conditions. Aside from his research Charlie is also heavily involved in leadership positions within professional organizations such as American Water Works Association (AWWA), Water Environment Federation (WEF), and the Society of Asian Scientists and Engineers (SASE). 



PFAS Remediation: A 7 Month Field GAC Rapid Column Test Combined with Carbon Characterization

Per- and polyfluoroalkyl substances (PFASs) have recently received considerable attention due to their ubiquitous presence, recalcitrance in the environment, and toxic properties. Using water quality data compiled by the USEPA, the New York Times recently reported that approximately 5.2 million Americans have drinking water sources contaminated with various PFASs. Due to this finding and a review of toxicological data, the USEPA issued a human health advisory in May 2016 for two perfluoroalkyl acids (PFAAs) including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at 70 ng/L for individual or combined concentrations. The effective removal of PFASs from contaminated water is extremely challenging. One of the most commonly used and accessible treatment technologies is granular activated carbon (GAC). Herein, we discuss PFAS remediation with GAC in a rare evaluation of GAC treatment with a real groundwater matrix performed at a locally impacted community.

In the field tests, we compared between various forms of commercially available activated carbons including 3 bituminous coal and 1 coconut based carbons for 6 months. Following data processing, we looked further into why each carbon performed the way it did through various non-standard carbon characterization tests including Brunauer-Emmett-Teller (BET) surface area analysis and Barrett-Joyner-Halenda (BJH) pore size and volume analysis.

Based on side by side manufacturer data on each carbon, we initially hypothesized that coconut based carbons would significantly outperform bituminous based carbons. However, our field results showed the opposite. After performing nonstandard analysis including BET and BJH we determined effective PFAS removal was most likely a function of pore characteristics. Although coconut based carbons measure higher surface areas, they are however typically more microporous. On the other hand, bituminous based carbons measure lower surface areas with less micropores but with more meso and macropores. As a result, we theorize that the presence of meso and macropores significantly facilitates PFAS adsorption onto carbon justifying the bituminous coal based carbon outperforming the coconut based carbons. In general, when choosing the best performing carbons, industry tends to choose carbons with higher surface areas; indeed, this study may prove otherwise.


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