Modeling of retention and re-entrainment of mono- and poly-disperse particles: Effects of hydrodynamics, particle size and interplay of different-sized particles retention Enze Ma, Tariq Ouahbi ⁎, Huaqing Wang, Nasre-Dine Ahfir, Abdellah Alem, Ahmed Hammadi Normandie UNIV, UNIHAVRE, UMR 6294, CNRS, LOMC, 76600 Le Havre, France HIGHLIGHTS • Numerical model of transport, retention and re-entrainment in porous media • Particle retention and re-entrainment dynamics under different hydrodynam- ic conditions • Wedged particles drastically restrain the re-entrainment of the smallest. • Strained and wedged larger particles supply excess retention sites for the smallest. GRAPHICAL ABSTRACT abstract article info Article history: Received 16 December 2016 Received in revised form 27 March 2017 Accepted 28 March 2017 Available online xxxx Editor: Kevin V. Thomas In this paper, numerical simulations of experimental data were performed with kinetic rate coefficients to char- acterize the retention and re-entrainment dynamics under different hydrodynamic conditions for monodisperse and polydisperse latex particles (3, 10, 16 μm and the mixture). The results show that drastic increase in fluid ve- locity provokes hardly any remarkable decrease in retention in the presence of large energy barriers (N 2000 kT). Systematical increases in deposition and re-entrainment dynamic rates were observed with fluid velocity and/or particle size. Increased irreversible deposition rate indicates straining and wedging dominate deposition in this study. Excess retention of 3 μm particle in the polydisperse particle suspension was observed. The origins are reckoned that deposited larger particles may hinder the re-entrainment of smaller particles near the grain-to- grain contact and can provide additional sites of attachment. © 2017 Elsevier B.V. All rights reserved. Keywords: Transport Deposition Numerical modeling Straining and wedging BTC 1. Introduction For more than recent four decades, the colloid filtration theory (CFT) stemming from Yao et al. (1971) has been supplying the basis for a func- tioning theory to predict particle transport and removal in homoge- neous porous media without particle-grain repulsion. However in aquifers, both particles and porous medium grain typically are found to be negatively charged and the subsurface water generally has a low ionic strength and neutral pH (Bradford et al., 2006a). Under these con- ditions, the electrical double layer interaction is repulsive, yielding an energy barrier for attachment (so-called unfavorable conditions). Near- ly no particle deposition is predicted by existing models derived from CFT in the presence of energy barriers (see Fig. 1) because these models are constructed on the basis of the hypothesis of totally equivalent sur- face characteristics (e.g. zeta potentials and surface topography) across the whole surfaces. However significant deviations were often found between the predictions with mean-filed approaches and experimental Science of the Total Environment 596–597 (2017) 222–229 ⁎ Corresponding author. E-mail address: tariq.ouahbi@univ-lehavre.fr (T. Ouahbi). http://dx.doi.org/10.1016/j.scitotenv.2017.03.254 0048-9697/© 2017 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv