Collector efficiency for hydrosol deep-bed filtration of non-Brownian particles at low and finite Reynolds numbers
Haochen Li*, John Sansalone
Aqueous filtration systems with granular media are increasingly implemented as a unit operation for the treatment of urban waters. Many of these aqueous filtration systems are designed with coarse granular media and are therefore subject to finite granular Reynolds numbers (Reg). In contrast to the Reg conditions generated by such designs, current hydrosol filtration models, such as the Yao and RT models, rely on a flow solution that is derived within the Stokes limit at low Reg. In systems that are subject to these finite and higher Reg regimes, the collector efficiency has not been examined. Therefore, in this study, we develop a 3D periodic porosity-compensated face-centered cubic sphere (PCFCC) computational fluid dynamics (CFD) model, with the surface interactions incorporated, to investigate the collector efficiency for Reg ranging from 0.01 to 20. Particle filtration induced by interception and sedimentation is examined for non-Brownian particles ranging from 1 to 100 μm under favorable surface interactions for particle adhesion. The results from the CFD-based PCFCC model agreed well with those of the classical RT and Yao models for Reg < 1. Based on 3150 simulations from the PCFCC model, we developed a new correlation for vertical aqueous filtration based on a modified gravitation number, NG*, for the initial deep-bed filtration efficiency at lower yet finite (0.01 to 20) Reg. The proposed PCFCC model has low computational cost and is extensibile from vertical to horizontal filtration at low and finite Reg.
Deep-bed filtration; Granular filtration; Unit operations; Stormwater; Urban water; Urban drainage