The accelerated biodegradation and mineralization of acetaminophen in the H₂O₂-stimulated upflow fixed-bed bioreactor (UFBR)

The biodegradation and mineralization of acetaminophen (ACT) was evaluated in the upflow fixed-bed bioreactor (UFBR) inoculated with a biomass containing mixture of Pseudomonas spp. and Bacillus spp. as the dominant bacteria under H₂O₂ stimulation. The effect of various main operational variables was evaluated on the performance of the UFBR for ACT removal. The maximum ACT removal was obtained at the H₂O₂:ACT molar ratio of 14. H₂O₂ induced the bacteria in biofilm for the in-situ generation of peroxidase resulted in the acceleration of ACT decomposition into more biodegradable intermediates. Over 99% of ACT and 72% of its TOC at initial ACT concentrations up to 300 mg/L could be eliminated under optimum H₂O₂:ACT molar ratio in the batch UFBR within 12 h recirculation time. The specific biodegradation rate of ACT increased from 1.0 to 4.1 mg ACT/g_biomass.h when the inlet loading rate was increased from 8.3 to 41.7 g ACT/m³.h. In addition, the complete biodegradation and TOC removal of ACT was observed in the continuous UFBR at the hydraulic retention time of 6 h and the presence of 1-20 g/L salinity without inhibition. The presence of H₂O₂ could efficiently stimulate the production of bacterial peroxidase, which in turn resulted in the acceleration of ACT biodegradation and mineralization. Therefore, the H₂O₂-stimulated UFBR is an efficient and viable technique for in-situ production of peroxidase used for acceleration of ACT biodegradation.