Biodegradation of inhibitory aromatic solvents in a novel bioreactor

Abstract

A novel bioreactor system for the microbial degradation of inhibitory aromatic solvents such as benzene, toluene, and xylenes was developed. Silicon tube was immersed in the reactors and liquid solvent was circulated within the tubing from a solvent reservoir. Transfer rate of the solvent through a silicon tubing was significantly affected by impeller speed, whereas other operating parameter such as circulation rate of liquid solvent within the tubing showed a negligible effect. In this study, the biodegradation of toluene was efficiently carried out using Pseudomonas putida in the bioreactor developed. Toluene was transferred at high rate into the culture broth through a silicon tube immersed in bioreactor. In continuous operation, the degradation rate of toluene in the bioreactor was found to be considerably high when compared to those in conventional methods. Mathematical model established well described the biodegradation of toluene in the bioreactor developed, and simulation results showed a good agreement with those obtained experimentally. Maximum removal efficiency of toluene was obtained at the condition under which the growth of microorganism was limited simultaneously by toluene and oxygen. It was proposed that the operational parameters of the biodegradation processes such as toluene transfer rate and dilution rate should be optimized by taking into consideration the removal efficiency and the level of toluene in the discharge stream. Simultaneous biodegradation of toluene and p-xylene was performed in a bioreactor. Bath, sequencing batch, and continuous mode of operation werecarried out in the bioreactor to compare the performance of the biodegradation of solvent mixture. Sequencing batch operation worked well, but several operational difficulties were found. Continuous operation was shown to present higher biodegradation rate and operational stability at lower dilution rate. Continuous biodegradation process was mathematically simulated, and opera...