Hybrid Slow Sand Filtration for Emerging Applications in Water Treatment.

The current review summarizes recent advances in slow sand filtration (SSF) for water treatment, with a focus on addressing key gaps identified in recent studies. SSF has progressed beyond traditional biophysical processes through the integration of hybrid systems and advanced materials. The addition of zerovalent iron, graphene oxide, activated carbon, and biocomposites has improved the removal of turbidity, pathogens, heavy metals, pesticides, pharmaceuticals, and emerging contaminants, including antibiotic resistance genes. Advancements in molecular biology tools, flux modeling, and system analysis have enhanced understanding of the mechanisms underlying SSF performance. Implementation across rural, urban, and industrial contexts demonstrates SSF's versatility, though operational challenges persist. However, significant knowledge gaps remain, particularly regarding nutrient removal efficiency, long-term performance, scalability, and the absence of standardized operational protocols. In any case, SSF is emerging as a flexible and multifunctional water treatment platform. Future research should prioritize long-term field validation, economic assessment, and process optimization to enable sustainable large-scale implementation.