Reactor models for horseradish peroxidase-catalyzed aromatic removal

Horseradish peroxidase catalyzes the oxidation of aqueous aromatic compounds by hydrogen peroxide, resulting in the formation of polymers, which spontaneously precipitate from solution. This process is being investigated as a means of removing toxic phenols and aromatic amines from industrial wastewaters. Models of plug-flow reactors and continuous-flow stirred tank reactors (CFSTR) were developed for the horseradish peroxidase-peroxide-aromatic substrate system as an aid for reactor design and process optimization. The models were verified for phenol removal at pH 7 and 25 degrees C, both in the presence and absence of high molecular weight polyethylene glycol, a protective additive. Modeling suggests that the rate of enzyme inactivation is lower in a CFSTR than in a plug-flow reactor. Nevertheless, no single optimal reactor configuration can be identified, because the best configuration depends on the initial phenol concentration, the desired effluent quality, and the selected retention time. The CFSTR performance could be improved further by engineering a system that returns effluent active enzyme to the treatment process.