Fig. 4. Results of column experiments on Cd transport with Escherichia coli input concentrations of (a) 5 x 10³ colony-forming units (cfu)/mL, pH = 7.5; (b) 1.6 x 10⁵ cfu/mL, pH = 7.0; and (c) 3.7 x 10⁷ cfu/mL, pH = 7.0. Escherichia coli were introduced after about 5 pore volumes injection of Cd and Br.