Kinetics of reactive azo-dye decolorization by Pseudomonas luteola in a biological activated carbon process

A laboratory-scale biological activated carbon (BAC) process was conducted to treat a reactive azo-dye (reactive red 22) by Pseudomonas luteola and the kinetics of azo-dye decolorization was investigated. The BAC-reactor removed 89% of reactive red 22 while P. luteola biofilm and suspended P. luteola reached a maximum growth rate at a steady-state condition. The azo-dye effluent from BAC-reactor met a discharge standard required by Taiwan government. The kinetic BAC-model, based on fundamental mechanisms, including surface diffusion, liquid-film mass transfer, Monod kinetics, growth of biofilm and suspended cells as well as shear loss of biofilm, was developed to describe the performance of biofilm attached on activated carbon in the azo-dye treatment process. The kinetic BAC-model predictions and experimental results for simultaneous adsorption and biodegradation of azo-dye contaminants were compared. It is shown that the fundamental mechanisms of BAC-process for azo-dye decolorization are not the simple addition but the synergetic combination of carbon adsorption and biodegradation of P. luteola strain. The major aspects of such synergism are the bioregeneration of the adsorbent and the reduction of the toxic effect of azo-dye contaminants in textile wastewater on P. luteola strain. The kinetic BAC-model not only provides insights into underlying mechanisms of adsorption and biodegradation but also can be used as a powerful tool to assist the design of a pilot-scale or full-scale BAC-process to treat azo-dye contaminants by P. luteola cells in textile wastewater.