A simplified dynamic model for the removal of toxic organics in a two-phase partitioning bioreactor

A two-phase partitioning bioreactor (TPPB) equipped with an agitator was used to remove phenol from an organic phase that was dispersed in an aqueous mineral salt medium containing Pseudomonas putida BCRC 14365. Kerosene was selected as the organic solvent. The initial cell concentration in aqueous cell medium was fixed at 25 g/m ³. The effect of initial phenol level in the organic phase (300-2500 g/m ³) on phenol degradation and cell growth was experimentally studied at 30°C. Under the ranges studied, phenol could be completely removed from the organic phase and biodegraded in the cell medium within 78 h even though the initial phenol level was high up to 1800 g/m ³. A simplified model that combines steady-state mass-transfer equations and dynamic growth kinetics of suspended cells was proposed to describe the whole process, in which all parameters involved were determined by separate experiments or existing correlations. It was shown that the proposed model acceptably described the whole process as long as phenol level in the cell medium did not exceed the toxicity limit of suspended P. putida under specified conditions. This model allowed selecting the qualified organic phases that had suitable partition coefficients for toxic organics with respect to the aqueous phases.