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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: wulei424@ufl.edu, bg55@ufl.edu and carpena@ufl.edu

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