Biology Reference
In-Depth Information
2.2.4 Computation of the sticking efficiency
Bacteria attachment to the sand was quantified by computing the sticking efficiency ( Α
L
) (-) at
the various sampling ports as (Kretzschmar et al., 1997, Abudalo et al., 2005)
M
2
d
eff
Α
= −
c
ln
(2.2)
(
)
L
3 1
−
Θ
L
Η
M
0
inf
where
d
is the median of the grain size weight distribution (m),
Η
is the single collector contact
efficiency (-) ,Θ is the total porosity of the sand (-),
L
is the travel distance (m),
is the total
M
inf
number of cells in the influent and
M
is the total number of cells in the effluent (-) obtained as
eff
(Kretzschzmar et al., 1997)
t
( )
=
∫
(2.3)
M
q
C t dt
eff
0
where
q
is the volumetric flow rate (mL/min),
C
is the cell suspension ( # cells/mL) and
t
is
time (min). The TE correlation equation (Tufenkji and Elimelech, 2004a) was used to compute
Η
. For this, we assumed that the bacteria density was 1055 kg/m
3
, and the Hamaker constant
was estimated to 6.5×10
-21
J (Walker et al., 2004).
To assist in analyzing relationships between cell properties and sticking efficiency, we employed
the strain averaged sticking efficiency (
) defined as:
Α
strain
7
∑
Α
strain,L
Α
=
i
=
1
(2.4)
strain
7
whereby subscript
strain
indicates the strain used and 7 refers to the number of sampling ports
used.
2.2.5 Statistical analyses
The degree of association between cell properties and
strai
Α
for all strains and between cell
properties and
Α
for all traveled distances were determined with the parametric Pearson's
correlation test. Correlations, determined with Pearson's correlation coefficient (
r
), were
considered to be statistically significant, when
p
≤
0 05
.
. All statistical analyses were conducted
using SPSS 14 (SPSS Inc., 2005).
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