Modeling volumetric clarifying filtration of particulate matter for transient rainfall-runoff loadings

摘要

Volumetric clarification incorporating filtration with engineered granular media is increasingly used as a viable combined unit operation for separation of rainfall-runoff particulate matter (PM). Such combined unit operations are typically operated at the catchment-level for rainfall-runoff clarification of transient loadings, in contrast to centralized watershed or sewershed regional treatment. Using computational fluid dynamics (CFD), this study models the PM separation by a volumetric clarifying filter (VCF) subject to unsteady event-based hydrologic, hydraulic, mass, and particle size distribution (PSD) loadings. Modeled and measured physical model results indicate that the VCF is capable of PM load reductions and effluent concentrations at or below 30 mg/L. These results, with PM measured as suspended sediment concentration (SSC) represent reductions ranging from 83 to 97% on an event basis. CFD model results predict effluent PM mass loads. Modeled effluent median particle diameter (d50_m), as an index for the filtered effluent PSD, reproduces the d50 m from the VCF physical model on an event basis. Filter head loss is examined as a function of flow rate. Despite geometric asymmetry of the multiple radial cartridge configuration tested, hydraulic loading for each individual cartridge is relatively uniform.