A novel trickling Ðbrous-bed bioreactor was developed for bioÐltration to remove pollutants present in contaminated air. Air containing benzene as the sole carbon source was e †ectively treated with a coculture of Pseudomonas putida and Pseudomonas Ñuorescens immobilized in the trickling bioÐlter, which was wetted with a liquid medium containing only inorganic mineral salts. When the inlet benzene concentration was 0É37 g m~3, the benzene removal efficiency (C gi ) in the bioÐlter was greater than 90% at an empty bed retention time (EBRT) of 8 min or a superÐcial air Ñow rate of 1É8 m3 m~2 h~1. In general, the removal efficiency decreased but the elimination capacity of the bioÐlter increased with increasing the inlet benzene concentration and the air (feed) Ñow rate. It was also found that the removal efficiency decreased but the elimination capacity increased with an increase in the loading capacity, which is equal to the inlet concentration divided by EBRT. The maximum elimination capacity achieved in this study was D11É5 g m~3 h~1 when the inlet benzene concentration was 1É7 g m~3 and the superÐcial air Ñow rate was 3É62 m3 m~2 h~1. A simple mathematical model based on the Ðrst-order reaction kinetics was developed to simulate the bioÐltration performance. The apparent Ðrst order parameter in K l this model was found to be linearly related to the inlet benzene concentration
The model can be used to predict the benzene removal (K l \ 4É64 [ 1É38 C gi ). efficiency and elimination capacity of the bioÐlter for benzene loading capacity up to D30 g m~3 h~1. Using this model, the maximum elimination capacity for the bioÐlter was estimated to be 12É3 g m~3 h~1, and the critical loading capacity was found to be 14 g m~3 h~1. The bioÐlter had a fast response to process condition changes and was stable for long-term operation ; no degeneration or clogging of the bioÐlter was encountered during the 3-month period studied. The bioÐlter also had a relatively low pressure drop of 750 Pa m~1 at a high super-Ðcial air Ñow rate of 7É21 m3 m~2 h~1, indicating a good potential for further scale up for industrial applications.