Removal efficiency and microbial community shifts in full-scale versus laboratory-scale bank filtration systems using horizontal collector wells.

Climate-induced changes in dissolved organic matter (DOM) and trace organic contaminants (TrOCs) present growing challenges for drinking water treatment, particularly in surface water-dependent regions. Bank filtration (BF), a natural subsurface treatment process, offers a sustainable solution, but its performance and scalability require further validation. This study simultaneously assesses the performance of laboratory-scale and full-scale BF systems using a horizontal collector well (HCW), both receiving the same source water and aquifer materials, to remove DOM and TrOCs, and to investigate changes in microbial communities under equivalent residence times (20 days). The full-scale HCW system achieved a 63.0 % DOM removal rate compared to 37.0 % in laboratory-scale columns, effectively reducing biopolymers and humic substances through soil passage. Microbial analysis revealed distinct shifts, with Proteobacteria comprising 80.1 % of the full-scale filtrate compared to 59.1 % in the laboratory-scale. Total cell counts and microbial activity decreased by 85.0 % and 90.4 % in the full-scale system, respectively. The removal efficiency for 60 selected TrOCs varied by their properties: hydrophobic ionic compounds achieved high removal (91.2 %), while hydrophilic and neutral compounds, including perfluoroalkyl substances (PFAS), showed lower removal rates (37.3 % and 24.5 %, respectively). Pharmaceuticals, steroid hormones, and pesticides were effectively removed, with some exceeding 99.9 %. This study is the first to directly compare full-scale HCW and laboratory-scale BF systems under controlled conditions. These findings highlight BF's effectiveness and the need for integrating complementary technologies to improve water quality and sustainability.