Flocculation-bio-treatment of heavy metals-vacuum preloading of the river sediments

Heavy metals pollution in river sediments is irreversible, and it is not easy to be found to be concealed. The pollution of heavy metals for river sediments is currently a serious environmental problem. In the paper, the Bacillus subtilis was selected to remove heavy metals by bio-mineralization method in river sediments. Optimal content of Bacillus subtilis powder and organophosphate monoester was 20 g and 0.2 mol in 1 L of bacterial solution, respectively. The optimum reaction time and temperature were 36 h and 30 °C, respectively. The optimal reaction conditions were applied to zinc ions in river sediments. After heavy metals treatment, there was little effect on the water content before and after flocculation and vacuum preloading. Treatment of heavy metals had no effect on the cross-plate shear strength of river sediments after vacuum preloading. After treatment of heavy metals, the effect of purifying water quality was the group B(Polyacrylamide + Polysilicate aluminium ferric) bigger than the group A (Polyacrylamide). The removal efficiency of zinc ions (Zn²⁺) in the group B was 89.59% and 74.99% before and after the vacuum preloading, respectively, which was better than that in the group A.