A model for simulating microbial growth‐degradation processes in porous media is developed. It is assumed that the bulk of microorganisms in an aquifer grow in microcolonies attached to matrix surfaces. As developed, the model applies to the growth and decay of aerobic, heterotrophic microorganisms whose growth is limited by lack of a carbon and energy source (substrate), an oxygen source or both simultaneously as described by modified Monod kinetics. Transport of substrate and oxygen in the porous medium is assumed to be governed by advection‐dispersion equations with surface adsorption. A total of five coupled equations result describing substrate and oxygen concentrations in the pore fluid, substrate and oxygen concentrations in the microcolonies and colony density, which is assumed sufficiently small so that aquifer hydraulic conductivity is not diminished. An iterative process involving an Eulerian‐Lagrangian numerical procedure that is highly resistant to numerical dispersion in the presence of small dispersivities is used to solve the overall model, with parameter values selected from the literature or estimated. Results indicate that biodgradation would be expected to have a major effect on contaminant transport when proper conditions for growth exist. For one‐dimensional transport in a column, the most rapid microbial growth always occurred at the influent boundary where oxygen and substrate concentrations were held constant independent of colony density. Anaerobic conditions develop rapidly and aerobic biodegradation ceases if large amounts of substrate are added to the system.

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 (O2 and/or NO3−), or mineral nutrient (NH4+), 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.

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This paper summarizes one institution's efforts to develop an ongoing strategy for gathering and analyzing data from constituents for use in appraisal and improvement efforts in its instructional programs. Although a large number of different constituents were identified, for logistical reasons it was decided to focus on five groups: undergraduate students, graduate students, faculty, alumni and industry. The primary emphasis of this paper is on the results from the alumni and industry surveys. Demographics of these two groups are given and the influence of these characteristics on responses to survey questions is noted. Comparisons drawn among the two groups show that alumni and industry responses are virtually identical on the importance of specific attributes associated with newly graduated engineers. A short discussion is also given which compares the responses of all five constituent groups on certain instructional program attributes.