Fig. 3. Results of column experiments on Cd transport with Bacillus subtilis spore input concentrations of (a) 9 x 10⁴ colony-forming units (cfu)/mL, pH = 7.0; (b) 7 x 10⁵ cfu/mL, pH = 7.7; and (c) 5.6 x 10⁷ cfu/mL, pH = 7.0. The spores were introduced after about 5 pore volumes injection of Cd and Br.