Hydrodynamic properties of the five columns were assessed
on days 5 and 212 using a pulse input of biological grade
tritiated water (3H2O, American Radiolabeled Chemicals, Inc.,
St. Louis, MO) as a conservative tracer. Injections of 10 mL of
128 mCi/mL 3H2O were made directly into the feed flow, for
a total applied radioactivity of 1.28 mCi per column. Over 24 h,
1 mL effluent samples were combined with 9 mL of liquid
scintillation cocktail and counted as described in Section 2.3.
Results from the generated 3H2O breakthrough curves were
modeled with the convection dispersion equation using
CXTFIT software (Toride et al., 1995).