Enhanced Biofilm Attachment onto Polyurethane Foam, Packed-bed Biotrickling Filters for the Treatment of Odors

The selection of an adequate support medium where the biofilm is immobilized in a biotrickling filter is critical for the optimization of the pollutant removal capacity of the unit. Recent efforts have focused in the development of synthetic media possessing properties such as high interfacial contact area, low density, high rigidity, high void fraction or porosity, sufficient water retention capacity, chemical resistance to severe acidity working conditions, and appropriate adhesion of the microflora to the medium surface. Polyurethane Foams (PUF) have been regarded as the media that best combines the aforesaid properties, yielding high removal efficiencies in the treatment of Volatile Organic Compounds (VOC) and Sulfur Reduced Compounds (SRC) while exhibiting low clogging and pressure drop. In this study, PUF will be coated with different positively charged polymeric solutions aiming at increasing the attachment capacity of the foam surface to bacteria degrading Hydrogen Sulfide (H2S) as substrate in a biotrickling filter. By means of this approach, typical negatively charged bacteria responsible for the oxidation of SRC will settle onto the foam media faster and more homogeneously, increasing the removal capacity of the unit during the start-up period and acclimatization stage compared to uncoated PUF. Aqueous solutions of polyethyleneimine, poly-d-lysine and animal collagen at different concentrations will be used as coating in SRC oxidizing cells growth on PUF during batch experiments. The solution providing the highest solid retention and cell growth will be used to coat PUF cubes filling a biotrickling filter as in a packed bed, treating H2S at high concentrations up to 100 ppmv and Empty Bed Residence Times (EBRT) as low as 5 seconds. Experimental results will be fitted to a unique theoretical model that predicts the performance of a non-adsorbing, macroporous media packed-bed biotrickling filter, and accounts for the axial distribution of the biofilm and water layer thicknesses.