Xenobiotic removal from wastewater in a two-phase partitioning bioreactor. Process modelling and identification of operational strategies

This paper proposes a dynamic model simulating the performance of a fed batch system operated as solid–liquid two-phase partitioning bioreactor, with polymer beads as the sequestering phase, applied to the removal of xenobiotic compounds from concentrated aqueous streams, in which substrate inhibition is significant. The model takes into account substrate mass transfer into, and within, the solid particles. Outputs of the models are xenobiotic concentrations in the liquid and solid phases and the concentration profile within the solid polymer beads. Sensitivity analyses have been performed on the influent concentration and on the main operating parameters, which can be modified to control the process performance (i.e. polymer/feed ratio, reaction and loading times). With an inhibitory substrate, the selected duration of the reaction period exhibits a critical value which determines the transition from high to low efficiency of the bioreactor. Application examples are provided for a target compound, 4-nitrophenol, previously investigated in TPPBs with an immiscible organic solvent, while Hytrel 8206 has been considered as the polymer partitioning phase. The proposed model has been shown to be a powerful tool to predict suitable operating conditions for TPPB systems treating inhibitory substrates.