Collision efficiency distribution of a bacterial suspension flowing through porous media and implications for...

The collision efficiency (alpha) distribution of a bacterial population was determined using multiple packed-bed columns of varying lengths and analyzing the bacteria clean-bed breakthrough concentrations using a distributed colloid filtration theory. This technique allows the alpha distribution to be determined independently from other effects that can cause non-exponential deposition, including detachment and blocking. It was found that multiple probability density functions (PDF's) could accurately replicate the experimental data. Regardless of which PDF was used, a distributed alpha resulted in significantly greater predicted field-scale transport than when using a single alpha. However, there were wide variations in the predicted field-scale transport between the different distributions, suggesting that lab-scale experiments may not be readily utilized to determine the specific PDF that best represents alpha at the field scale. Finally, blocking was observed in the column effluent curves, underscoring the fact that if non-clean-bed processes occur then an approach such as that utilized in the current study may be used to separate the non-clean-bed and clean-bed processes when determining the collision efficiency distribution.