Influence of synthetic packing materials on the gas dispersion and biodegradation kinetics in fungal air biofilters |
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Authors: | Francesc X Prenafeta-Boldú Josep Illa Johan W van Groenestijn Xavier Flotats |
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Institution: | (1) GIRO Technological Centre, Pompeu Fabra 1, 08100 Mollet del Vallès, Barcelona, Spain;(2) IRTA, Passeig de Gràcia, 44, 3a pl., 08007 Barcelona, Spain;(3) University of Lleida, Avda Rovira Roure, 191, 25198 Lleida, Spain;(4) Department of Microbiology, TNO, P.O. Box 360, 3700 AJ Zeist, The Netherlands |
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Abstract: | The biodegradation of toluene was studied in two lab-scale air biofilters operated in parallel, packed respectively with perlite
granules (PEG) and polyurethane foam cubes (PUC) and inoculated with the same toluene-degrading fungus. Differences on the
material pore size, from micrometres in PEG to millimetres in PUC, were responsible for distinct biomass growth patterns.
A compact biofilm was formed around PEG, being the interstitial spaces progressively filled with biomass. Microbial growth
concentrated at the core of PUC and the excess of biomass was washed-off, remaining the gas pressure drop comparatively low.
Air dispersion in the bed was characterised by tracer studies and modelled as a series of completely stirred tanks (CSTR).
The obtained number of CSTR (n) in the PEG packing increased from 33 to 86 along with the applied gas flow (equivalent to empty bed retention times from
48 to 12 s) and with operation time (up to 6 months). In the PUC bed, n varied between 9 and 13, indicating that a stronger and steadier gas dispersion was achieved. Michaelis–Menten half saturation
constant (k
m) estimates ranged 71–113 mg m−3, depending on the experimental conditions, but such differences were not significant at a 95% confidence interval. The maximum
volumetric elimination rate (r
m) varied from 23 to 50 g m−3 h−1. Comparison between volumetric and biomass specific biodegradation activities indicated that toluene mass transfer was slower
with PEG than with PUC as a consequence of a smaller biofilm surface and to the presence of larger zones of stagnant air. |
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Keywords: | Air biofiltration Packing materials Biodegradation kinetics Dispersion dynamics Fungi Toluene abatement |
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