Soil Washing and Bioremediation of Tailing Dam Wastes

The paper presents that soil washing and bioremediation technologies were employed to treat the contaminated soil. Various works were conduced in parallel with each other and th results of the laboratouy studies were used to determine critical parameters. Four lixiviants, i.e. sulphuric acid, acetic acid, oxalic acid and ethylene diamine acetic acid were tests at three concentration levels respectively. The tests showed that the leaching of the heavy metals increases as the soil porosity increases. Silica sand was added to increase porosity of the contaminated soil. Hightest Mn removal was achieved mainly by sulphuric and oxalic acid at 0.001M at all soil samples. EDTA was significantly efficient in the removal of Ni and Zn. The recovery of heavy metals, particalarly Mn, decreased as the depth of samping increased. Heterogeneous bacteria and filamentous organism plate counts were conduced to evaluate the growth of the bacteria and filamentous organisms in the soil. The results from this study suggest that the leaching of heavy metals from the contaminated soil is to a large extent dependant on the pH of the leaching solution. By increasing the soil’s porosity and bioremediating the soil, higher extractions of metals were achieved.