The silica sand samples were sieved, washed, air-dried, and sterilized before the experiments. The pH of the sand suspended in distilled water was 8.5. The heavy metal bioremediation studies were performed in 50 mm diameter and 500 mm length columns (OMG Chemical Co., Korea), containing 1.0 kg silica sand supplemented with 2 mM mixture of heavy metals. The heavy metals were thoroughly mixed into the sand while in solution form. The bacterial mixtures culture (A3, equivalent to 108 CFU/mL) was grown overnight in YA broth. The control treatment consisted of the same set-up as the experimental treatment but without the addition of bacterial cells. Bioremediation was determined by measuring the time required for 100 mL of 5 mM urea and 25 mM calcium chloride to pass through the column. The experiment was performed at room temperature (25 ◦C) and run for 3 d.