Physical Experiment and Modeling of the Transport and Deposition of Polydisperse Particles in Stormwater: Effects of a Depth-Dependent Initial Filter Coefficient

Abstract

The artificial recharge of stormwater is an effective approach for replenishing aquifer and reduce urban waterlogging, but prone to clogging by suspended particles (SP) that are highly heterogeneously sized. In this paper, the transport and deposition of SP in a sand column were investigated under a constant flow condition, for five stormwater concentrations. A depth-dependent initial filter coefficient is incorporated into the conventional filtration model. This modified model considers the heterogeneity of the particle population by lumping the capture of heterogeneous SP into a capture probability. The good agreement between the results of the modified model and the experimental results of measured outlet concentration and average specific deposit validated the modified model. The experiment data and the simulation results both indicate that the highly hyper-exponential retention profiles are caused by non-uniform deposition of heterogeneous SP; and, the conventional model was found to homogenize the spatial distribution of SP retention and overestimate retention of the porous medium. Local and overall permeability reductions were assessed by an empirical relationship and the Kozeny-Carman model, respectively. It is shown that consideration of polydisperse suspended particles is of primary importance. This study highlights the effects of polydisperse particles on SP deposition in a saturated porous medium.

The Comparison of Seven Models to Simulate the Transport and Deposition of Polydisperse Particles under Favorable Conditions in a Saturated Medium

“…At the end of the experiment, the mixed deposition and sandy material packed in the column was carefully excavated and cut into sections to obtain the final deposition profile of the retained particles along the column length according to the procedure described in [32]. PSD analyses were conducted for the retained particles.…”

“…) is the solid phase concentration of retained particles, u (L•T −1 ) is the Darcy velocity, t (T) is the time coordinate, ε is the porosity of the sand porous medium, and ρ p (M•L −3 ) is the bulk density of the particles. The kinetic equation of the polydisperse particles is given as follows [32]:…”

“…where S m is the maximal retention (S m ≤ ε), and measured to be 0.265 according to the methods described in [32].…”