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Interpreting deposition patterns of microbial particles in laboratory-scale column experiments.
Nathalie Tufenkji1, Jeremy A Redman, Menachem Elimelech
1Department of Chemical Engineering, Environmental Engineering Program, P.O. Box 208286, Yale University, New Haven, Connecticut 06520-8286, USA.
Environmental Science & Technology
|March 13, 2003
Summary
Microbial particle transport in subsurface environments deviates from traditional filtration models. Nonexponential decay in microbial retention profiles suggests variable deposition rates, crucial for understanding subsurface microbial fate and transport.
Area of Science:
- Environmental science
- Geology
- Microbiology
Background:
- Subsurface microbial transport is governed by natural filtration (capture) by sediment grains.
- Classical filtration models predict exponential microbial concentration decrease with distance.
- Laboratory experiments reveal nonexponential microbial retention profiles, challenging existing models.
Purpose of the Study:
- To investigate the causes of nonexponential microbial deposition patterns in porous media.
- To incorporate particle variability into colloid filtration theory.
- To identify key indicators for microbial deposition and transport mechanisms.
Main Methods:
- Developed a filtration model incorporating a distribution of deposition rate coefficients.
- Tested log-normal, bimodal, and power-law distributions for the deposition rate coefficient.
- Compared model predictions with experimental data from bacteria and virus transport studies.
Main Results:
- Power-law distribution of deposition rates explains nonexponential microbial deposition.
- Particle release and blocking effects also contribute to deviations from classical theory.
- Microbial retention profile shape is a critical indicator of deposition and transport mechanisms.
Conclusions:
- Heterogeneity in microbial particle deposition rates, particularly a power-law distribution, explains nonexponential retention.
- Classical filtration theory requires modification to account for particle variability.
- Analyzing retention profile shape is essential for accurate subsurface microbial transport characterization, beyond just monitoring fluid-phase concentration.