CHARACTERISTICS OF SIMULTANEOUS UTILIZATION OF OXYGEN AND SUBSTRATE IN A 3-PHASE FLUIDIZED-BED BIOREACTOR

A three-phase fluidized bed bioreactor was employed for a biological treatment process of phenolic wastewater. The characteristics of simultaneous utilization of oxygen and substrate (phenol) in the bioreactor were evaluated. In the experiments, activated carbon BAC and CB ball were utilized as media. Air was used for aeration. The model discussed in this paper includes the following steps: (1) Gas-liquid mass transfer of oxygen (2) Liquid-biofilm interfacial mass transfer of oxygen and substrate (3) Intrabiofilm mass transfer and simultaneous biological reaction of oxygen and substrate Two cases, biological substrate removal as rate-determining step and oxygen absorption as rate-defermining step, were evaluated. Within the range of experimental conditions studied, biooxidation of phenol was simply evaluated by treating substrate utilization as zero-order reaction. The experimental results of phenol removal were well explained by an equation based on the assumption of oxygen absorption as the rate-determining step. It was found that biological reaction did not act as the rate-determining step in the case of superficial air velocity up to 1.0 cm/s. The volumetric phenol removal rate becomes more than 8 kg-phenol/(m3-bed. d) by increase of oxygen supply in the three-phase fluidized bed bioreactor. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.