Biofiltration has been established as a promising alternative to conventional air pollution control technologies. However, gas biofilters modeling has been less developed than experimental research due to the complexity of describing the fundamental processes and the lack of globally accepted\ud physical, chemical and biological parameters. In addition, biofiltration modeling based on degradation activity of fungi has been rarely considered.\ud For this reason, in thiswork, a dynamic model describing toluene abatement by a bacterial and fungal biofilter is developed, calibrated and validated.\ud The mathematical model is based on detailed mass balances which include the main processes involved in the system: convection, absorption, diffusion and biodegradation. The model was calibrated and validated using experimental data obtained from two equal lab-scale biofilters packed\ud with coconut fiber and pine leaves, respectively. Both reactors were operated under similar conditions during 100 days at an empty bed residence time of 60 s and an average inlet load of 77 g toluenem−3 h−1. Biofilters were initially inoculated with a bacterial consortium, even though reactors\ud were mostly colonized by fungi after 60 days of operation according to microscopic observation and reactors pH. Removal efficiency increased notably from 20% for the bacterial period to 80% for the fully developed fungal biofilters. Since kinetic parameters are strongly dependent on the\ud biological population, semi-saturation constants for toluene and maximum growth rates were determined for bacterial and fungal operation periods.\ud Kinetic parameters were fitted by means of an optimization routine using either outlet concentrations or removal efficiency data from the coconut fiber biofilter. A novel procedure in gas biofilters modeling was considered for checking the model calibration, by the assessment of the parameters confidence interval based on the Fisher Information Matrix (FIM). Kinetic parameters estimated in the coconut fiber reactor were validated in the pine leaves biofilter for bacterial and fungal operation. Adequate model fitting to the experimental outlet gas concentration for both bacterial and fungal operation periods was verified by using a standard statistical test.Peer ReviewedPostprint (published version

An industrial-scale biotrickling filter for the removal of high concentrations of H 2 S is described in this work. The system has been operating at H 2 S inlet concentrations between 1000 and 3000 ppm v at acidic conditions. A decrease of pH from 2.6 to 1.8 did not affect the biological activity inside the biofilter while reducing the water make-up consumption up to 75%. The current oxygen supply system, based on direct injection of air to the liquid phase, has demonstrated to be inefficient for a long term operation leading to elemental sulfur accumulation in the packing material (i.e. promoting clogging episodes). The present study demonstrates it is possible to partially remove (40.3%) the deposited elemental sulfur by bio-oxidation when biogas is not fed. In normal operation conditions, the implementation of an aeration system based on jet

In the present work, 10 packing materials commonly used as support media in biofiltration are analyzed and compared to evaluate their suitability according to physical characteristics. The nature of the packing material in biofilters is an important factor for the success in their construction and operation. Different packing materials have been used in biofiltration without a global agreement about which ones are the most adequate for biofiltration success. The materials studied were chosen according to previous works in the field of biofiltration including both organic and inorganic (or synthetic) materials. A set of nine different parameters were selected to cope with well-established factors such as material specific surface area, pressure drop, nutrients supply, water retentivity, sorption capacity and purchase cost. One ranking of packing materials was established per each parameter studied to define a relative suitability degree. Since biofiltration success generally depends on a combination of the ranked parameters, a procedure was defined to compare packing materials suitability under common situations in biofiltration. Selected scenarios such as biofiltration of intermittent loads of pollutant and biofiltration of waste gases with low relative humidity were investigated. The results indicate that, out of the packing materials studied, activated carbons were ranked on top of several parameter rankings and showed as a significantly better packing material when parameters were combined to assess such selected scenarios. Keywords: packing materials; biofiltration; Physical properties; Economical assessment IntroductionBiological treatments have become an effective and economical alternative to traditional gas treatment systems.The correct selection of the packing material employed in a biofilter or a biotrickling filter is an important decision to achieve high removal efficiencies and to maintain an optimal performance in the long-term run [1]. Despite the widely recognized importance of the support media role, several packing materials have been used in biofiltration under a wide range of operating conditions without a global agreement about which one is the most adequate.Previous works studying packing materials are mostly based on a sole packing material case study [2][3][4] or on the comparison of the removal efficiency achieved by different packed biofilters under the same operating conditions [5,6]. In general, these studies concluded that high removal efficiencies in biofilters are strongly related to packing material properties although physical and chemical properties of the materials were not evaluated thoroughly. The nature of the carrier material, which may be organic, natural inorganic or entirely synthetic, is a crucial factor for the successful application of biofilters and biotrickling filters because it affects the frequency at which the medium is replaced and other key factors such as bacterial activity and pressure drop across the bioreactor [7,8].Among the natural carriers reported, com...

Overall mass transfer coefficients (K G a and K L a) were determined experimentally for four different-nature packing materials used in gas-phase biotrickling filters. A simple methodology based on overall mass balances and following a standard procedure allowed to calculate the mass transfer coefficients under different operating conditions corresponding to usual biotrickling filtration situations. Results showed an increase of mass transfer resistance when increasing the empty bed residence time (EBRT) of the reactor for all packing materials. Experimental results were fitted to existing and well-accepted correlations used in conventional biofilter or biotrickling filter modeling. The comparison of experimental and theoretical data showed huge discrepancies. Simple correlations for the experimental data obtained in this study were also suggested.

Biomass accumulation was studied in a biofilter packed with an organic/inorganic, hybrid packing material made of clay pellets plus clay pellets covered by a thin layer of compost and inoculated with activated sludge from a municipal WWTP. Operating conditions under high loads of toluene were selected to force plant failure by clogging. The biofilter achieved a remarkably maximum elimination capacity of 595 g toluene •m-3 •h-1 (1280 g toluene•m-3 •h-1 based on the first 25 cm of the biofilter). The evolution of biofilter performance and biomass growth over the packing material were studied until the reactor collapsed. Several variables related to biomass growth such as reactor weight, oxygen consumption, CO 2 production, substrate removal and pressure drop were monitored. Alternated periods of substrate supply and starvation were tested to assess biomass growth and detachment. Moreover, pH and biomass content were periodically measured in the leachate to determine the washing efficiency of intermittent watering. Pressure drop measurements demonstrated that watering was an effective technique to wash the excess of biomass accumulated. Experimental data also permitted to determine important parameters for biofilter modeling as the biomass growth yield and the stoichometric coefficients of toluene biological oxidation. Variables monitored are sensitive to biomass accumulation