Boosting the Removal Rate of PFAS by Algae Through Coagulant-Assisted Algae-Bubble Matrix

Inspired by foam fractionation (FF) and coagulation for per- and polyfluoroalkyl substances (PFAS) removal, we explored using photosynthesized O 2 bubbles from microalgae cells to extract PFAS from water. Each cell serves as a microscale site for O 2 bubble generation. The system was introduced as coagulant-assisted algae-bubble matrix (CAABM). In the system, two types of green algae ( Chlorella sp. and Ankistrodesmus falcatus ) and supporting media (glass wool, cotton balls) with different surface charges, and three coagulants (FeCl 3 , alum, and poly (diallyldimethylammonium chloride) were investigated. Results showed that 12.7–13.9% of perfluorooctanoic acid (PFOA) and 7.5–10.3% of the perfluorobutanoic acid (PFBA) could be removed within 97 min. The coagulants are necessary as they can neutralize the negative charge of algae cells to enhance PFAS removal via cell adsorption and bubble extraction. It should be noted that, unlike conventional FF, the foams or accumulated oxygen bubbles in the CAABM are not separated but remain in the column due to the slow bubble generation via photosynthesis and strong bubble attachment to cells. An advantage of this system is the faster removal of PFAS when compared to reported cases using algae alone. Specifically, the PFAS removal rate was enhanced by 21.3 and 428.3 times for PFOA and PFBA, respectively (it is an overall comparison based on a single column test without considering other factors such as biomass loading density, O 2 generation rate). In particular, the CAABM helps promote short-chain PFBA removal as compared to reported algal or coagulation systems. Plus, the PFAS-laden biomass, enriched with lipids, is likely to reduce fuel cost in the incineration treatment. More work will be conducted later to clarify it.