Combined Settlement and Clogging in Drainage Sand Layer for Suspended Solids, Colloids and Inorganic Salts

Abstract

A combined sedimentation test of suspended solids, colloids, and inorganic salts and a sand column blocking test were conducted, and mineral composition and grain characteristics of sediments were determined. Adsorption and flocculation reactions occurred in colloids (silver iodide) and inorganic salts (calcium chloride or aluminum sulfate), and final products were flocculation or flocculent network polymers. This increased the sedimentation rate of suspended matter by 8–18 times. Combined migration of suspended solids, colloids (silver iodide), and inorganic salts (calcium chloride or aluminum sulfate) significantly exacerbated silting of sand columns. Compared with sand column silting caused by pure SS, this combined migration more than halved sand column silting time and reduced hydraulic conductivity by nearly one order of magnitude.