However, as seen in Fig. 4a, the amount of degraded BTEX (degradation efficiency) was highest at
360 mg/L although the degradation percentage was lower at 360 mg/L than at 120 and 240 mg/L. Also, BTEX degradation efficiency decreased significantly at 480 mg/L of BTEX. These results might be due to the combined effects of the higher availability of BTEX compounds at 360 mg/L than at 120 and 240 mg/L and the higher toxicity at 480 mg/L than at 360 mg/L (Steliga et al., 2012).