Foam fractionator as a tool to remove dissolved organic matter and improve the flocculation of the marine microalga Nannochloropsis oceanica

Hydrothermal Alkaline Treatment (HALT) of Foam Fractionation Concentrate Derived from PFAS-Contaminated Groundwater

“…Similarly, fluoride concentrations measured during treatment of 1-to-2 diluted FC2 reached 1050 (±50) mg/L (Figure 1d), 108% of the TOF concentration estimated from LC-QToF-MS analysis (970 ± 100 mg/L). Furthermore, 19 F-NMR spectra of FC2 collected before and after treatment (Figure S3) indicate near complete conversion of fluoro-organic structures in the foam concentrate to inorganic fluoride. The spectrum collected following treatment showed a single sharp peak matching the sodium fluoride standard.…”

“…18 Accumulation of DOM in the foam concentrates is consistent with the documented application of FF processes for such purposes in the aquaculture industry. 19 FC2 also has much higher chloride (754 mg/L) but otherwise has similar levels of inorganic anions as FC1. The diluted AFFF had much lower inorganic anions (individual <1 mg/L) due to the fact that it was not derived from groundwater.…”

“…42,43 Total organic fluorine (TOF) concentrations in FC1 and FC2 estimated from target and semiquantitative PFAS analyses are 16.8 ± 0.2 and 1,940 ± 200 mg/L, respectively. Analysis of FC2 with 19 F-NMR (Figure S3a) (measurable due to the higher fluorine concentration) showed a total fluorine concentration of 1,510 ± 100 mg/L. The ∼20% higher TOF value estimated by LC-QToF-MS analyses can be attributed, in part, to high uncertainties associated with semiquantitative estimates for the concentration of suspect PFASs (>30%).…”

“…23 19 F-NMR spectra were collected on a JEOL ECA-500 spectrometer (500 MHz) to estimate the total fluorine content of foam concentrates and to verify the conversion of organic fluorine to inorganic fluoride ion during hydrothermal reactions. Additional details of the methods used to measure 19 F-NMR spectra are provided elsewhere. 23 Characterization of Dissolved Organic Matter (DOM).…”

“…While several treatment technologies have been developed to remove PFASs from contaminated water, − foam fractionation (FF) technology has emerged as a viable strategy for remediation. − FF applies fine gas bubbles to remove molecules with surfactant properties that accumulate at gas–liquid interfaces . FF, also called protein skimming, has been increasingly employed in recirculating aquaculture systems and other water treatment processes to remove particles, colloids, and dissolved substances. ,− Foaming with air or nitrogen produces microbubbles (ca. 0.5–0.8 mm in diameter) that serve as surfaces to adsorb dissolved organic matter (DOM) and transfer it to the water surface where it can be physically separated to improve water quality .…”