In-suit Remediation Of Heavy Metal Pollution Of Lead-zinc Tailings By Microorganism

Large amount of tailings in the tailings storage contain a certain amount of heavy metal ions, which will dissolve into water with the leaching of rain water, mineral water, etc.Waste water with large amount of heavy metal ions spread with the surface runoff and under ground permeating making surrounding environment polluted. In-situ remediation with low cost, good effect, easy operation, no secondary pollution etc attracts wide attention.This paper studied the suitable coditions for growth and reproduction of sulphate reducing bacteria and iron reducing bacteria, and the treatment effect for heavy metal pollution of lead-zinc tailin gs.Research on yeast extract, tryptone, glucose, sodium lactate served as nutrient substance indicated that 1.2 g/L of yeast extract could provide the nutrient the reducing bacteria need to grow and keep the advantage in 40 days. 1.8 g/L of sodium lactate could inhabit the growth of autotrophic bacteria.1.2 g/L of yeast extract and 1.8 g/L of sodium lactate were selected to provide the nutrient and reducing bacteria multiplied.Research on the effect of ammonium sulfate to the bacteria indicated that autotrophic bacteria could use ammonium sulfate effectively, while the reducing bacteria had weak selectivity from organic or inorganic nitrogen nutrient. Therefor, in the solution contained yeast extract and sodium lactate without ammonium sulfate, the reducing bacteria growed well with high pH, low Eh, and low heavy metal ions.Research on the effect of different environmental parameters to the removal of heavy metal ions indicated that sulphate reducing bacteria and iron reducing bacteria could remove heavy metal ions in the solution with pH above 5.0. In oxygen and non-oxygen condition, the reducing bacteria could precipitate the ion of zinc and stibium, which lied in the reducing atmosphere.Research on the variation of characteristic of the solution and lead-zinc tailings with the simulative acid rain eluviation in 7 weeks. With the growth and metabolism of the reducing bacteria, SO42- would be reduced into S2-, Fe(OH)3 would be reduced into Fe2+, while OH- and HCO3- would be produced and combined with H+, which elevated pH value, reduced Eh value. Meanwhile, S2- would combine with heavy metal ions into precipitate.Since the comparison of solubility product constant is: Sb2S3<CuS<PbS<ZnS<FeS, the element iron and arsenic will deposited after stibium and zinc. After 7 weeks’ remediation, the removal rate of As, Fe, Pb, Sb, Zn were above 99% in the solution of sulphate reducing bacteria. In the solution of sulphate reducing bacteria and iron reducing bacteria, a certain amount of Fe2+ was existed in the solution, which could maintain low level of Eh value, suitable for the reducing bacteria to grow and work. Concentration of heavy metal ions in the solution had reduced to a low level, thus, bioremediation had good effect.