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Convection-dispersion equations coupled with deposition kinetics. deposition rate coefficient (kd)
Vegetative Filter Strip (VFS)
advance current understanding of fundamental processes govern colloid fate and transport in overland flow in surface vegetation systems.
inform guidelines for the design, establishment, and maintenance of VFS for colloidal contaminants, such as pathogens (Fig.9).
Transport of colloidal particles (Fig.1) in water flow is an important contamination process. carry a variety of contaminants enhance their mobility in aquatic systems affect primary productivity, nutrient cycling, and species composition
Very limited research on fate and transport of colloidal particles in surface flow, particularly with respect to colloid transport through vegetation in overland flow (Fig.2). Plant filtration has a significant effect on
colloidal particles transport Knowledge gap regarding the mechanisms that
govern colloid transport through vegetation Systemic theoretical and experimental investigations
needed
The contact efficiency of a single-collector (η0)
η0 =
Classic filtration theory (Fig.3)o Sedimentationo Interceptiono Diffusion
Mathematical models (Fig.4)
Experimental single-collector contact efficiency (η0)
Experimental apparatus (Fig.5) and scenarios (Table.1)
Effects of flow velocity and colloid and collector Sizes Increases in flow velocity (u) reduced η0 (Fig.6) η0 varied with colloid diameters (dp), suggesting
that a minimum value of η0 might exist at a critical colloid size (Fig.7)
Smaller collector had a larger η0
Comparison of experimental data and theoretical predictions The theoretical predictions underestimated the
experimental data (Fig.8).
A regression equation A best-fit (R2 > 0.98, Fig.9) correlation equation:
To determine how perturbations in flow velocity, colloid size, and collector size affect the single-collector efficiency of colloid capture by a cylindrical collector in laminar overland flow
To test whether existing single-collector efficiency models can be used to predict colloid capture by a cylinder in laminar overland flow
To develop a correlation equation to describe the single-collector efficiency of colloid transport through emergent vegetation in laminar overland flow
Experimental Analysis of Colloid Capture by a Cylindrical Collector in Laminar Overland FlowLei Wu, Bin Gao, and Rafael Muñoz-Carpena
Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL 32611
1.Yao, et al., Environ. Sci. Technol. 1971, 5, 11052. Rajagopalan, R.; Tien, C. Aiche J. 1976, 22, 5233. Tufenkji, et al., Environ. Sci. Technol. 2004, 38, 5294. Palmer, et al., Limnol. Oceanogr. 2004, 49, 76
Introduction Theory and Methods Results and Discussion Implications
Objectives
0 I D
cdN
rdt
00
c
c c
rN u d l
Fig.3
Fig.5
0.00 0.05 0.10 0.15 0.20 0.25
1E-4
1E-3
0.01
Sin
gle
colle
ctor
effi
cien
cy (η 0e
xp)
Flow velocity (cm/s)
N0= 8.6E+06 no./mL
dp = 1.05 um
dc = 2 cm
T = 298 Kt =120 mins
0.01 0.1 1 10 1001E-4
1E-3
0.01
u=0.02cm/sT=298Kt =120mins
Sin
gle
colle
ctor
effi
cien
cy (η 0e
xp)
Colloid size (um)
dc=1cm dc=2cm
0.0000 0.0005 0.0010 0.0015
0.0000
0.0005
0.0010
0.0015
0.0000 0.0005 0.0010 0.0015
0.0000
0.0005
0.0010
0.0015
0.0000 0.0005 0.0010 0.0015
0.0000
0.0005
0.0010
0.0015
0.0000 0.0005 0.0010 0.0015
0.0000
0.0005
0.0010
0.0015
T=298K
t=120mins
0TE
0RT
0Yao
0exp
(b)
(c)
T=298K
t=120mins
0exp
(d)
T=298K
t=120mins
0exp
(a)
T=298K
t=120mins
0equations 1-3
0exp
Fig.6 Fig.7
Fig.8
0.94 0.030 0.0044Rec peN
Fig.9
0
4(1 )d
c
f uk
d f
References
Fig.1
This research was partially supported by the NSF grant CBET-1054405
Acknowledgements
0.000 0.002 0.004 0.006 0.0080.000
0.002
0.004
0.006
0.008
η 0exp
η0Eqn.regression
Fig.2
Fig.9Table 1: Experimental scenarios
Wu, L. , B. Gao, and R. Muñoz-Carpena, 2011. Experimental Analysis of Colloid Capture by a Cylindrical Collector in Laminar Overland Flow. Environmental Science & Technology, doi: 10.1021/es201578nEmail: [email protected], [email protected] and [email protected]
Rate at which particles strike the collector
Rate at which particles approach the collector
Fig.4
5 7(Re 0.42 42, 4.5 10 9.7 10 )c peN
f : spacing densityα : attachment efficiency
& N0: NO. of colloids in the suspensionu: flow velocitydc: diameter of collectorlc: height of coated area of collector
Effect of flow velocity
Effect of colloid size and collector size
Coated area
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