The use of bacteria for the in situ remediation of contaminants is becoming a common practice. To effectively apply such bioremediation techniques we must have a better understanding of how bacteria, present mostly as biofilms, move through a porous medium. No experimental or field data presented to date provide information on the spatial distribution of the biofilm as growth and fluid convection occurs.

A sorted relaxation-resolved NMRI technique is introduced for the non-destructive, quantitative spatial resolution of biofilm in an idealized porous medium. T1 and T2 relaxation NMR imaging data were used to resolve spatial maps of biofilm. Experiments with a transparent, open-flow and glass bead-packed parallel-plate bioreactor, yielded NMR biofilm images comparable to photographs of the bioreactor. Sorting of the relaxation data improves NMRI by using a threshold biofilm relaxation time value from relaxation time histograms. Ranges of relaxation times for biofilm were determined to be between 0.3 and 2.2 seconds for T1, and 0.07 and 0.11 seconds for T2. Our results clearly point to the feasibility of using NMR methods for the in-situ monitoring of bacterial populations in porous media. We also show that T1 and T2 resolved methods will work best for this application.

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