Effects of gas flow rate and inlet concentration on xylene vapors biofiltration performance

According to previous literature works on biofiltration of mixtures of arom atic compounds vapors, xylene is the most resistant to biodegradation in bi ofilters. However, only limited information is available about the applicat ion of biofiltration to the removal of xylene vapors as the sole contaminan t in the air stream. In the present work biofiltration of xylene vapors has been investigated on a laboratory scale biofilter packed with a new filter material composed essentially of peat mixed with structuring and condition ing agents and initially inoculated with a microbial consortium. Three vari ous gas flow rates, i.e. 0.4, 0.7 and 1 m(3) h(-1), were tested for xylene inlet concentration ranging from 0.2 to 4 g m(-3). The biofilter proved to be highly efficient in the removal of xylene at a gas flow rate of 0.4 m3 h (-1) corresponding to a gas residence time of 157 s. For all the tested inl et concentrations, both the removal efficiency and the elimination capacity decreased for high gas flow rates. For all the tested gas flow rates, a de crease in the elimination capacity was noticed for high xylene inlet concen tration. The follow-up of carbon dioxide concentration profile through the biofilter revealed that the mass ratio of carbon dioxide produced to the xy lene removed was approximately 2.5/1, which confirms complete degradation o f xylene if one considers the fraction of the consumed organic carbon used for the microbial growth. (C) 2000 Elsevier Science S.A. All rights reserve d.