Technical and ecological evaluation of a diatomite-based filter strip for cleaning polluted runoff from a railway embankment

This study presents a technical and ecological evaluation of a diatomite-based filter strip designed to purify polluted surface runoff from a railway embankment. A pilot-scale three-layer structure (1.0 m width, 0.70 m height, slope 1:1.5) was constructed parallel to the embankment. The upper gravel layer dissipates flow and retains coarse solids, the diatomite layer (0.8-2.0 mm) serves as the main sorption–filtration medium for petroleum hydrocarbons (PHCs) and fine suspended solids, and the bottom drainage layer provides filtrate collection and sampling. Field observations during rainfall and snowmelt events showed removal efficiencies of 97.5 % for petroleum hydrocarbons and 96.7 % for suspended solids, ensuring compliance with regulatory limits for fishery water bodies. The system operates passively, without external energy, and maintains stable filtration parameters. The results confirm the engineering feasibility and ecological efficiency of diatomite-based filter strips for mitigating hydrocarbon pollution in railway drainage systems.