Abstract: The blockage caused by polydisperse particles in the process of stormwater recharge is in essence the transport and deposition of particles in porous media. To find deposition feature of polydisperse particles, a one-dimensional sand column test for artificial recharge is carried out to observe the outflow and inflow concentration of polydisperse particles ranging from 0.375 to 55.82 μm at five injection concentrations. A modified model in consideration of the particle polydispersity is theoretically derived based on the colloid filtration theory (CFT). Both the experimental and simulation results show the retention profiles of five concentrations compile with the hyper-exponential law, rather than the exponential retention predicted by the conventional model. The highly hyper-exponential retention profiles are caused by non-uniform deposition of polydisperse particles; and, the conventional model is found to homogenize the spatial distribution of retention of polydisperse particles. Local and overall permeability reductions are assessed by the Kozeny-Carman model. The blockage degree of media is directly relevant to particle size. The permeability of the medium is reduced to 52%, and the deposition of particles larger than 2.26 μm in the stormwater is the main cause of blockage.

Key words: stormwater recharge, polydisperse particles, filter coefficient, hyper-exponential retention, Kozeny-Carman model