On the other hand, as expected, the BTEX degradation rates increased as the initial cell concentration increased (Fig. 4b). The BTEX degradation rates increased significantly when the cell mass increased from 1.0 107 cells/L to 2.0 107 cells/L, but the degradation rates were relatively similar between 2.0 107 and 4.0 107 cells/L. Therefore, 360 mg/L of BTEX and 2.0 107 cells/L were used as the constant conditions for the next single factor experiments of NH4Cl and NaH2PO4