Determination of the Efficiencies of Clay and PFCL or PACL with Na2CO3 Flocculent in the Removal of TSS from the AMD

Abstract

The experiment was conducted on the acid mine drainage (AMD) that was sampled from the Krugersdorp decant in South Africa. Five 500 ml glass beakers were filled with 200 ml of AMD sample and dosed with synthetic flocculent of FeCl3 and Na2CO3 (PFCl) and treated in jar test (exp. A). pH, conductivity, total suspended solids (TSS), dissolved oxygen (DO) and oxidation reduction potential (ORP) were measured after treatment and an hour settling. Another identical set of experiments was carried out with a combination of clay and PFCl dosage (exp. B). A third similar set of experiments was conducted with dosages of a combination of clay with PFCl or clay with AlCl3 and Na2CO3 (PACl) including another set of experiments using five 500 ml Erlenmeyer flasks in a shaker (exp. C). The pH results of the samples dosed with PFCl are relatively lower than that of the samples with a combination of clay and PACl dosage. The pH changing pattern with PFCl exhibited an increasing rate with increasing dosage whereas the pH of the sample dosed with a combination of clay and PFCl decreases with increasing dosage. The results show that bentonite clay does not have significant impact on pH of the samples. The ORP in treated AMD samples of experiments A and B is lower than in raw AMD sample. Residual TSS of the AMD samples which were treated with mixing are similarly identical to those of the samples treated on a shaker. TSS removal of the AMD samples with clay and PFCl is better than that with FeCl or PACl only.