Impact of effluent organic matter on perfluoroalkyl acid removal from wastewater effluent by granular activated carbon and alternative adsorbents

Occurrence of perfluoroalkyl acids (PFAAs) in wastewater effluent coupled with increasingly stringent regula-tions has increased the need for more effective sorption-based PFAA treatment approaches. This study investi-gated the impact of ozone (O3)-biologically active filtration (BAF) as integral components of non-reverse osmosis (RO)-based potable reuse treatment trains and as a potential pretreatment option to improve adsorptive PFAA removal from wastewater effluent by nonselective (e.g., granular activated carbon (GAC) and selective (e.g., anionic exchange resins (AER) and surface-modified clay (SMC)) adsorbents. For nonselective GAC, O3 and BAF resulted in similar PFAA removal improvements, while BAF alone performed better than O3 for AER and SMC. O3-BAF in tandem resulted in the highest PFAA removal performance improvement among pretreatments investigated for selective and nonselective adsorbents. Side by side evaluation of the dissolved organic carbon (DOC) breakthrough curves and size exclusion chromatography (SEC) for each pretreatment scenario suggested that despite the higher affinity of selective adsorbents towards PFAAs, the competition between PFAA and effluent organic matter (EfOM) (molecular weights (MWs): 100-1000 Da) negatively impacts the performance of these adsorbents. The SEC results also demonstrated that transformation of hydrophobic EfOM to more hydro-philic molecules during O3 and biotransformation of EfOM during BAF were the dominant mechanisms responsible for alleviating the competition between PFAA and EfOM, resulting in PFAA removal improvement.

Automated summary

The occurrence of perfluoroalkyl acids (PFAAs) in wastewater effluent has led to a greater need for effective sorption-based PFAA treatment methods. This study investigated the impact of ozone (O3)-biologically active filtration (BAF) as pretreatment options for nonselective and selective adsorbents. The results showed that O3-BAF in tandem achieved the highest PFAA removal performance improvement. Additionally, the transformation of hydrophobic effluent organic matter (EfOM) to hydrophilic molecules during O3 and biotransformation of EfOM during BAF were the main mechanisms responsible for improving PFAA removal.