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efficiencies compared with measured values of sticking efficiencies over the total transport
distances and at column segments make the minimum sticking efficiency a valuable tool in
delineating well-head protection areas in real-world scenarios.
5.6 Conclusions
The transport of two
Escherichia coli
strains was studied over 25 m using helical columns.
Column segment sticking efficiency and sticking efficiency over total transport distances were
determined. Fractions of total bacteria mass flowing into the column that were retained in
column segments as a function of their corresponding segment sticking efficiency revealed
power-law distributions in cell affinity for quartz grains. Also, a substantial sub-population of
total input mass exited the column. The results in this study indicated that:
Low values of sticking efficiencies in the order 10
-3
to 10
-6
are measurable in the
laboratory, and the results demonstrate the importance of the use of long columns.
•
•
Power-law distributions in sticking efficiencies commonly observed for limited intra-
column distances (< 2 m) are applicable for the description of distributions at large
segments (> 6 m) of columns packed with quartz grains.
•
The power-law distribution in segment sticking efficiencies can provide useful
information about transport of bacteria in the environment. In addition, it may provide a
useful framework within which the transport and attachment of bacteria may be
evaluated.
•
Substantial numbers of bacteria cells may possess the minimum sticking efficiency
indicating the possibility of being transported over distances much longer than may be
predicted using measured sticking efficiencies from experiments with both short and long
columns.
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