The effect of the thickness of water film on BTF performance was investigated by where they compared the PC with continuous nutrient trickling at a flux of 1.36 m 3 /m 2 h and no trickling. They reported a 20% increase in PC without trickling as compared to the trickling. This improvement effect was attributed to direct gas to biofilm contact where the mass transfer resistance due to water film is not present. The results of this study also show the same effect where PC decrease with increasing the trickling rate. It was also shown in this study that the case of no trickling is not sustainable for long period. However, intermittent supply of the nutrient can be adopted, where the reactor is either flushed or flooded at controlled intervals.