Factors affecting continuous 2,4-DNT degradation by an immobilized mixed microbial culture were investigated including the cell adaptation to this toxic substrate, 4-NT co-degradation, packing material porosity and substrate mass loading. Experiments were carried out in two packed bed reactors, with poraver (porous glass) and expanded slate as packing materials, using a concurrent water-air flow with ample oxygen. Running the system as a batch reactor with re-circulated medium showed that the immobilized cells adapted to higher 2,4-DNT concentrations yielding higher substrate biodegradation rates. The 2,4-DNT removal rate further increased, up to 180-265 mg L(-1)d(-1), when the immobilized biomass cultivation was switched to a continuous mode. The type of the packing material influenced the 2,4-DNT removal rate, apparently due to the difference in biofilm development. Significant changes in the biofilm composition were observed compared to the original inoculum despite poor biofilm growth.

Institute of Chemical Technology Department of Fermentation Chemistry and Bioengineering Prague Czech Republic

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