ISSN:
1745-6584
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Energy, Environment Protection, Nuclear Power Engineering
,
Geosciences
Notes:
Experiments were conducted to investigate the role of sorption during the transport of the bacterium Klebsiella oxytoca through saturated silica sand. The sorption process was visualized at the pore scale in a minicell (3 mm deep × 6.0 mm wide × 7.0 cm long) using scanning confocal laser microscopy. The sorption process was also studied by conducting column experiments at three scales (3.8, 10, and 40 cm long). Results of image analyses of the sorbed and unattached cells in pore throats and the bacterial breakthrough data from the column experiments exhibited similar trends. Breakthrough peaks were attenuated with respect to the input concentrations and well-defined tailing was observed. Visualization suggested that the sorption process was dominated by reversible and irreversible sorption (kirr). In the case of reversible sorption, the rate of forward sorption (kf) was different from the rate for reversible sorption (kr). Visualization also showed that the bacterial coverage on the sand grains, although extensive, covered 〈 0.5% of the available surface area. A 1D solution for advective-dispersive transport was used to estimate kirr, kf, and kr with appropriate values for the coefficient of hydrodynamic dispersion and average linear pore-water velocity (determined from CI data). Simulated best fits to the bacterial peaks were good for the 3.8 cm columns but underestimated peak heights in the 10 and 40 cm columns by one order of magnitude. Best-fit kirr values decreased with increasing scale (0.6,0.13, and 0.062 hr-1 for the 3.8,10, and 40 cm columns, respectively) and showed that a kirr value determined at one scale cannot be used to determine concentrations of K. oxytoca with time at another scale. These results suggested that kirr was a function of to (length of column over velocity). The equivalent irreversible sorption parameter (A, where A = to· kirr) was a constant (mean value of 3.36) for the three scales investigated. This observation suggested that the use of the value A, determined at one scale of investigation, may prove effective in approximating the value of kirr predicting bacterial transport at other scales. Best-fit determinations yielded the same kf and kr values at all three scales (0.1 and 0.02 hr-1). This suggested that reversible sorption may be independent of column length. This study emphasized the need for more comprehensive investigations of the role of sorption in the transport of microorganisms in the subsurface.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1745-6584.1997.tb00122.x
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