Dynamic volume-averaged model of heat and mass transport within a compost biofilter: I. Modal development

Successful, long-term operation of a biofilter system depends on maintainin g a suitable biofilm environment within a porous medium reactor. In this ar ticle a mathematical study was conducted of the spatial and temporal change s of biofilter performance due to interphase heat and mass transport. The m ethod of volume averaging was used to spatially smooth the three-phase (sol id, liquid, and gas) conservation equations over the biofilter domain. The packing medium was assumed to be inert, removing the solid phase mass conti nuity equation from the system. The finite element method was used to integ rate the resulting nonlinear-coupled partial differential equations, tracki ng eight state variables: temperature, water vapor, dry air, liquid water, biofilm, gas and liquid phase organic pollutant, and nutrient densities, th rough time and space. A multiphase, gas and liquid flow model was adapted t o the biofilter model from previous studies of unsaturated groundwater flow . Newton's method accelerated by an LU direct solver was used to iterate th e model for solutions. Effects of packing media on performance were investi gated to illustrate the utility of the model. The moisture dynamics and nut rient cycling are presented in Part II of this article. (C) 2001 John Wiley & Sons, Inc.