The concept of incorporating foam fractionation in aerated bioreactors at wastewater treatment plants (WWTPs) for the removal of per- and polyfluoroalkyl substances (PFAS) has recently been proposed. The extent of PFAS enrichment in aerated bioreactors’ foams, as indicated by enrichment factors (EFs), has been observed to vary widely. Laboratory evidence has shown that factors affecting PFAS enrichment in foams include conductivity, surfactant concentrations and initial PFAS concentrations. However, real wastewaters are complex heterogenous matrices with physical, chemical and biological characteristics potentially contributing to the phenomenon of PFAS partitioning into foams. In this study, we characterised mixed liquor suspensions, including conductivity, filament content, aqueous PFAS concentrations, surface tension and total suspended solids concentrations (TSS) as well as foams, including bubble size and half-life. We used statistical tools – linear mixed-effects model – to establish relationships between PFAS enrichment in aerated bioreactor foams and the examined characteristics. We found that some of the examined characteristics, specifically filament content, surface tension and TSS concentrations measured in mixed liquor suspension and foam half-life, are negatively and significantly associated with the enrichment of longer chain PFAS (with perfluorinated carbon number ≥ 6). Of these, filament content is the important determinant of PFAS enrichment, potentially leading to an increase in, for example, perfluorooctanoic acid (PFOA) EF from 3 to 100 between typical filamentous and non-filamentous suspended biomass. However, enrichment of shorter chain PFAS (with perfluorinated carbon number ≤ 5) is negligible and is not affected by the characteristics that were measured. The findings of our study may serve as valuable information for the implementation of foam fractionation at WWTPs by elucidating the drivers that contribute to the enrichment of longer chain PFAS, under conditions typically found at WWTPs.

中文翻译：

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废水处理厂数据分析确定了泡沫中 PFAS 富集的驱动因素


最近提出了在废水处理厂 （WWTP） 的曝气生物反应器中加入泡沫分馏以去除全氟烷基和多氟烷基物质 （PFAS） 的概念。据观察，曝气生物反应器泡沫中 PFAS 的富集程度（如富集因子 （EF） 所示）差异很大。实验室证据表明，影响泡沫中 PFAS 富集的因素包括电导率、表面活性剂浓度和初始 PFAS 浓度。然而，真正的废水是复杂的异质基质，具有物理、化学和生物特性，可能导致 PFAS 分解成泡沫的现象。在这项研究中，我们表征了混合液体悬浮液，包括电导率、细丝含量、水性 PFAS 浓度、表面张力和总悬浮固体浓度 （TSS） 以及泡沫，包括气泡大小和半衰期。我们使用统计工具（线性混合效应模型）来确定曝气生物反应器泡沫中 PFAS 富集与检查特性之间的关系。我们发现，一些检查的特性，特别是在混合液悬浮液和泡沫半衰期中测量的细丝含量、表面张力和 TSS 浓度，与长链 PFAS（全氟碳数≥ 6）的富集呈负相关且显著相关。其中，细丝含量是 PFAS 富集的重要决定因素，可能导致典型丝状和非丝状悬浮生物质之间的全氟辛酸 （PFOA） EF 从 3 增加到 100。 然而，短链 PFAS（全氟碳数≤ 5）的富集可以忽略不计，并且不受所测特性的影响。我们的研究结果可能为在 WWTP 中常见的条件下，通过阐明导致长链 PFAS 富集的驱动因素，为 WWTP 实施泡沫分馏提供有价值的信息。