| Summary: | A draft-tube spouted bed bioreactor with different types of aeration was developed to study the aerobic microbial degradation of aqueous phenol using a cyclodextrin-based support material. Since oxygen is a key in aerobic bioprocesses, the influence of different types of aeration on the volumetric mass transfer coefficient, kLa, was investigated. The values of kLa increased with gas spatial velocity, and decreased with increasing solid load, air flow distribution (spout to total flow ratio) and medium viscosity (carboxymethylcellulose solutions). The proposed correlations for kLa predicted the experimental data satisfactorily. Bacteria from activated sludge were acclimated to phenol in a continuous stirred tank bioreactor, and then immobilized onto the hydrogel particles within the spouted bed bioreactor. Microorganisms from cultures obtained in both bioreactors were isolated and characterized. Microbial population distribution in bioreactors was not only affected by phenol concentration, but also by oxygen and nitrogen availability, the system configuration and the presence of intermediates formed during phenol metabolization. A maximum elimination capacity of 6.63 kg-phenol/m3d was achieved in the spouted bed bioreactor, with Burkholderia cepacia being the dominant strain during high degradation periods. Batch experiments were carried out to evaluate the biodegradation of phenol by isolated dominant strains. Higher phenol concentrations inhibited the biomass and reduced the biodegradation rate. The modeling of batch phenol biodegradation indicated that the Haldane inhibitory model provided a good fit to the experimental data. Results showed that Acinetobacter baumannii and Burkholderia cepacia yielded the maximum specific growth rates.
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