Tables 2a–c and 3a–c shows the ANOVA results for RE and EC of benzene and toluene, respectively, under the conditions tested in this 17 alpha-propionate study. The main effects were significant for all the RE and EC profiles of benzene and toluene as observed from the very high F and low P values (<0.05). Among the main effects on toluene EC, toluene concentration (T = 37.34, P = 0.017) appears to play a major role than benzene concentration (T = −9.91, P = 0.064) and flow rate (T = 19.23, P = 0.033). In the case of benzene EC, the concentration of toluene (T = −12.19, P = 0.052) affected the EC values more severely than benzene itself (T = 2.23, P = 0.031) The total maximum EC observed in this study was 91.2 g/m3 h at a total ILR of 150.2 g/m3 h. This EC value is nearly 25% higher than the EC values observed in the same biofilter when benzene was treated individually. It should be noticed that at this ILR, nearly 94% of the elimination was contributed due to toluene degradation at higher loading rates. Therefore, phosphorylation is quite apparent that the presence of toluene inhibits the degradation of benzene strongly at higher loading rates, while the presence of benzene has little effect on toluene degradation.