Granular Activated Carbon for PFAS Removal in Municipal Wastewater: A Rapid Small-Scale Column Test Study.

work summary

 

This study mainly assesses the effectiveness of granular activated carbon (GAC) in municipal wastewater treatment, especially in the removal of perfluorinated and polyfluoroalkyl substances (PFAS). The study employed rapid small-scale column tests (RSSCTs) to simulate the performance of GAC in municipal wastewater treatment facilities, and tested the ability of two types of commercial granular activated carbon and one type of commercial biochar to remove four types of PFAS, namely PFOA, PFOS, PFHxA and PFHxS, from secondary treated municipal wastewater. The research results show that biochar is not effective in removing PFAS, while granular activated carbon has a better removal effect on PFOA and PFOS, but is not effective enough for short-chain PFAS (such as PFHxA). Further cost analysis indicates that the economic feasibility of applying the GAC system to remove PFAS in municipal wastewater treatment facilities is poor, especially when dealing with high-concentration PFAS, where the operation and maintenance costs are relatively high. The study also points out that the control of PFAS may need to focus on upstream discharge control within wastewater treatment plants or the removal of high-concentration wastewater streams, rather than relying solely on end-of-pipe treatment technologies.

graphical abstract

 

Quick Overview of Pictures and Text

Figure 1. (a) The RSSCT Settings used in this project. (B) Schematic diagram of RSSCT setup.

Figure 2. Removal of PFOA, PFOS, PFHxA and PFHxS from the effluent of WRRF #1 using (a) GAC #1, (B) GAC #2 and (c) biochar. The initial concentration of a single PFAS compound was 200 ng/L, simulated EBCT was 10 min, approach velocity was 6 m/h, and DOC was 5.9 mg/L

Figure 3. Removal of PFOA, PFOS, PFHxA and PFHxS from the effluent of WRRF #2 using (a) GAC #1, (B) GAC #2 and (c) biochar. The initial concentration of a single PFAS compound was 200 ng/L, simulated EBCT was 10 min, approach velocity was 6 m/h, and DOC was 5.6 mg/L.

 

Main Findings

The innovation points and main findings of this work include: Firstly, the author experimentally verified the removal effect of granular activated carbon on PFAS in municipal wastewater and compared it with other possible adsorption materials (such as biochar). It was found that biochar had a poorer removal effect on PFAS, indicating that it may not be applicable in the treatment process. Secondly, although granular activated carbon can effectively remove some long-chain PFAS (such as PFOS and PFOA), it performs poorly on short-chain PFAS (such as PFHxA), revealing the influence of different PFAS molecular structures on adsorption efficiency. In addition, the literature also conducted a cost analysis. The results indicated that the economic viability of applying GAC technology was poor, especially in the case of high concentrations of PFAS, which might lead to a significant increase in the operating costs of municipal wastewater treatment facilities. Finally, the research suggests that controlling the side flow within wastewater treatment plants (such as sludge dewatering flow) or implementing source control might be more feasible strategies for PFAS removal.