The influence of physical heterogeneity on microbial degradation and distribution in porous media

摘要: Intermediate-scale experiments (meter-long, two-dimensional flow cell) were performed with aerobic biodegradation of benzoate substrate in physically heterogeneous (bimodal inclusive) media. Clastic heterogeneities represented a quasi-two-dimensional field, low-conductivity inclusions embedded high-conductivity sandy matrix. The two media had similar pore-scale dispersivities but the conductivity ratio (∼1∶50) incurred macrodispersive spreading longitudinal direction. sand was uniformly inoculated Pseudomonas cepacia sp., and pulse input chloride ion tracer evaluated. Degradation growth oxygen-limited under nonlinear dual-Monod kinetics controlled by spatial temporal variations nutrient flux. created regions slow transport that prolonged dual availability both oxygen substrate, which turn enhanced microbial these regions. Bacterial detachment significant, fivefold increase biomass due to entirely accounted for aqueous effluent displayed complicated breakthrough curve. High-resolution deterministic modeling applied simulate intermediate-scale experiment, parameters relevant constitutive relations calibrated independently through batch small-scale column experiments. Parameter fitting match cell data avoided. This approach taken order test predictive capability as it would necessarily be used field application avoid priori assumption all processes adequately respective theories. Analyses fit between model then isolate further experimental study. iterative experimental/modeling identified contributed (surprisingly) yet are not currently incorporated most mathematical models: (1) buoyancy effects associated very small solution density variations, amplified media, (2) dynamic biological growth, namely, endogenous respiration, division partitioning phase, active adhesion/detachment strongly coupled dissolved nutrients or microorganisms.