Dynamic simulation of benzene vapor treatment by a two-phase partitioning bioscrubber: Part II: Model calibration, validation, and predictions

The two-phase partitioning bioscrubber (TPPB) model presented in Part I has been validated using experimental data under constant and transient operating conditions for the treatment of benzene waste gases by Achromobacter xylosoxidans Y234 with n-hexadecane as an immiscible, organic phase. Model calibration was performed to account for observed enhancements of benzene biodegradation rates in biphasic media, postulating that direct benzene uptake from dispersed organic droplets increased substrate bioavailability. This led to the use of an ‘effective dissolved substrate concentration’ to model cell specific growth rates. Model predictions were greatly improved using this empirical modification. The characteristics of the organic phase, both in terms of the volume fraction selected and its high equilibrium solubility, are found to be of critical importance for minimizing effluent gas VOC concentrations and stabilizing performance during transient operation. The biokinetic parameters μmax and KS are also particularly important, greatly influencing the response of the TPPB both during and while recovering from transient periods. KS was found to be important for influencing steady-state benzene removal efficiencies under even invariant operation, leading to the conclusion that microorganisms which can maintain high rates of biological activity under very dilute substrate concentrations will make ideal biocatalysts in the TPPB.