Selective imaging of biofilms in porous media by NMR relaxation

Nuclear magnetic resonance imaging (NMRI) techniques were employed to ident ify and selectively image biological films (biofilm) growing in aqueous sys tems. Biofilms are shown to affect both the longitudinal (T-1) and transver se (T-2) NMR relaxation time values of proximal water hydrogens. Results ar e shown for biofilm growth experiments performed in a transparent parallel- plate reactor. A comparison of biofilm distributions by both NMR and optica l imaging yielded general agreement for both an open-flow system and an ide alized porous system (the reactor without and with packed glass beads, resp ectively). The selective imaging of biofilm by relaxation NMRI is dependent upon the resolution of relaxation times for the fluid phases, dynamic rang e, and signal-to-noise ratio, For open-flow systems, the use of a rapid and quantitative T-2-sorted NMRI technique was preferred. For porous systems w here T-2 values are generally more similar, a T-1-weighted technique was pr eferred. (C) 1999 Academic Press.