Abstract

This study investigated the potential of biochar filters as a replacement for, or complement to, sand filters for removal of per- and polyfluoroalkyl substances (PFASs) from wastewater in on-site wastewater treatment systems (OWTSs). Concentrations and removal of nine perfluoroalkyl carboxylates (PFCAs; C3-11) and three perfluoroalkane sulfonates (PFSAs; C-4,C- 6,C- 8) and one perfluorooctanesulfonamide (FOSA; C-8) were investigated over 22 weeks in four treatments with column filters: biochar (BC) without biofilm (BC-no-biofilm), biochar with active biofilm (BC-active-biofilm), biochar with inactive biofilm (BC-inactive-biofilm) and sand with active biofilm (Sand-active-biofilm). The filters were operated under hydraulic loading (50 L m(-2) day(-1)) to mimic the loading rate in on-site filtration beds. The initial concentrations of the Sigma PFASs in the influent were in the range of 1500-4900 ng L-1. In BC-no-biofilm, the removal efficiency (20-60%) and adsorption capacity (0-88 ng EPFASs g(-1) BC) of short-chain PFCAs (C3-6) and PFSA (C-4) was low, whereas the removal efficiency (90-99%) and the adsorption capacity (73-168 ng g(-1)) was high for C-7-C-11 PFCAs, C-6, C-8 PFSAs and FOSA. The relative removal was generally lower for C3-9 PFCAs and C-4, C-6, C-8 PFSAs using BC-active-biofilm and BC-inactive-biofilm compared with BC-no-biofilm. This can be explained by the presence of biofilm and solids in BC-active-biofilm and the presence of wastewater solids in BC-inactive-biofilm, which decreased the availability and number of adsorption sites for PFASs compared with BC-no-biofilm. On the other hand, inactivation of the biofilm resulted in lower removal efficiencies for C5-11 PFCAs, C-4, (C)6, C-8 PFSAs and FOSA, probably because the biofilm degraded organic matter and thus increased the availability and number of adsorption sites compared with BC-inactive-biofilm. Sand-active-biofilm showed poor removal (0-70%) for all PFASs except FOSA (90%) and its adsorption capacity was low (0.0-7.5 ng g(-1)). In general, for all biochar treatments, shorter-chain PFASs were more resistant to removal than longer-chain PFASs. In addition, C-4, C-6 and C-8 PFSAs showed 10-30%, 10-50% and 20-30% higher average removal efficiency, respectively, than PFCAs with corresponding perfiuoroalkyl chain length. In conclusion, biochar is a promising filter medium for removal of PFASs in OWTSs, especially for PFASs with a perfluorocarbon chain longer than C-6. 2019 Elsevier Ltd. All rights reserved.

Keywords

Active biofilm; Adsorption; Biochar filters; Biodegradation; Inactive biofilm; PFASs; On-site wastewater treatment

Published in

Environmental Pollution
2019, Volume: 247, pages: 155-164
Publisher: ELSEVIER SCI LTD

SLU Authors

• Dalahmeh, Sahar

  • Department of Energy and Technology, Swedish University of Agricultural Sciences
    

• Ahrens, Lutz

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

SDG6 Ensure availability and sustainable management of water and sanitation for all
SDG3 Ensure healthy lives and promote well-being for all at all ages


UKÄ Subject classification

Water Treatment


Publication identifier

DOI: https://doi.org/10.1016/j.envpol.2019.01.032

Permanent link to this page (URI)

https://res.slu.se/id/publ/99232