A numerical transport model for oxygen‐ and nitrate‐based respiration linked to substrate and nutrient availability in porous media

Abstract

A model to simulate organic carbon biodegradation by facultative bacteria in saturated porous media using oxygen‐ and/or nitrate‐based respiration is developed. Basic assumptions incorporated into the model concept include a simulated particle‐bound microbial population comprised of heterotrophic, facultative bacteria in which metabolism is controlled by lack of either an organic carbon‐electron donor source (substrate), electron acceptor (O 2 and/or NO 3 − ), or mineral nutrient (NH 4 + ), or all three simultaneously. A system of nine coupled nonlinear equations is developed that describe the processes of transport, degradation, and microbial growth and decay. The solution technique is highly resistant to numerical dispersion and oscillation when applied to the advection‐dispersion equation, even for large Peclet numbers (100). Microbial utilization of materials is assumed to occur by intrapore scale diffusion of materials across a diffusion boundary layer separating the particle‐bound microcolonies of bacteria from the pore fluid. Denitrifying enzyme inhibition is modeled as a function of the oxygen concentration associated with the biomass. Simulations of oxygen‐based, nitrate‐based, and multiple‐electron acceptor respiration are presented for a hypothetical experiment using kinetic parameter value estimates available from the literature.