| Biofiltration is a gas treatment technique that can potentially be used to remove methane, a greenhouse gas, from various methane emission sources. Problems associated with methane biofilters include methane's hydrophobic nature, as well as supplying nitrogen.; The objectives of this work were to test the effects of different nitrogen supplies on methane biofiltration, to determine factors controlling the removal rate, and to illustrate the fundamental mechanisms that underlie hydrophobic compound biofiltration. The methane concentrations tested ranged from 190 to 500 ppm in air.; Three forms of nitrogen supply, ammonia, nitrate and organic nitrogen (peptone), were used. Gaseous ammonia in the inlet gas was observed to be inhibitory to methane biodegradation in biofilters. This inhibitory effect, however, was less severe when NH3 was restrained within a small portion of the reactor bed. Nitrate supported methane biofiltration, with maximum removal efficiencies reaching ∼80% at 2 min empty bed residence time. An elevated pH, however, was observed as a result of NO3 --N assimilation. Biofilter performance decline caused by nitrogen deficit was also observed in methane biofilters using NO3 --N. Organic nitrogen as peptone did not demonstrate harmful effects on the methane biofilter operations.; A steady-state model of methane biofiltration was developed using conventional biofiltration mechanisms. The methane removal efficiency predicted by the model was close to the experimental results, indicating the validity of conventional mechanisms in hydrophobic compound biofiltration. Biofilm specific surface area (AS) used in the model was estimated utilizing an X-ray microtomography (XMT) technique and fractal image analysis methods.; A dynamic model describing hydrophobic compound biofiltration processes also was developed. Nitrogen limitation was incorporated in the model. Both explicit and implicit approaches were utilized and compared in model programming using the MATLAB language. Excellent agreement was found between results of the model simulation and the experimental results. Sensitivity of other model parameters was also tested.; Simultaneous biofilter removal of methane (hydrophobic) and ethanol (hydrophilic) was investigated. Experimental results showed no substantial methane removal in the simultaneous treatment despite the greater biofilm formation, probably because the rapid ethanol degrader growth excluded methane removal from the active region through resource competition. |
