Evaluation of Per- and Polyfluoroalkyl Substances Leaching from Biosolids and Mitigation Potential of Biochar through Undisturbed Soil Columns

• Published in: ACS ES&T water 2024-02, Vol.4 (2), p.413-426
• Main Authors: Holly, Michael A., Gunn, Kpoti M., Keymer, Daniel, Sanford, Joseph R.
• Format: Article
• Language: English
• ISSN: 2690-0637; 2690-0637
• DOI: 10.1021/acsestwater.3c00414

Land application of biosolids recycles nutrients and reduces the need for commercial fertilizers. However, per- and polyfluoroalkyl substances (PFAS) may leach from biosolids, resulting in groundwater contamination. We measured PFAS leaching from land-applied biosolids through undisturbed soil column trials and evaluated the treatment potential of amending biosolids with biochar. Synthetic rainfall was applied weekly to undisturbed soil columns from four regions in Wisconsin, including two fields with a history of biosolid application, simulating annual precipitation. The treatments consisted of a control (soil only), soil amended with biosolids, and soil receiving a mixture of biosolids and biochar. Concentrations of total PFAS in leachate were significantly affected by soil location and site history One-time application of biosolids may result in groundwater contamination, as PFAS concentrations in leachate exceeded the local groundwater standard (a combined perfluorooctanoic acid and perfluorooctanesulfonic acid groundwater concentration of 20 ng L–1) at three locations. Legacy PFAS may pose a risk to human health years after biosolid application, as a control column from a site with an intensive history of biosolid application exceeded PFAS groundwater standards. Incorporation of biochar with biosolids during application mitigated PFAS (specifically from soils with elevated leaching potential) through significant reductions of C7–C10 perfluoroalkyl carboxylic acids and C4 and C6–C8 perfluorosulfonic acids (40% to 64% reduction in measured Σ28 PFAS). Biochar may facilitate sustainable use of biosolids through mitigation of long-chain PFAS leaching, pending a long-term field evaluation.