1
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Transport of Colloids in Saturated and Unsaturated
Porous Media: Pore-scale Observation of Processes
Arturo A. Keller, Sanya Sirivithayapakorn,& Maria Auset
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Size Range of Various ParticlesSize Range of Various Particles
0.00001
0.0001
0.0010.01
0.1 1 10 1001000
Size Range (µm)
Colloids
Molecules
Macromolecules
Viruses
Bacteria
Protozoa
Gravel
Sand
Silt
Clay
Effective Pore Diameter
Contaminants
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Courtesy of Bruce Robinson, LANL
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Saturated Saturated ZoneZone
Vadose Vadose ZoneZone
Leaking Sewer lineLeaking Sewer lineOr Septic tankOr Septic tank
Contaminated Water Supply ?
Contaminants Contaminants --VirusesViruses-- BacteriaBacteria
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Colloids in Groundwater
Photo credit: A. F.P. Williams, U.S. EPA, http://www.epa.gov/nerlcwww/index.htmlB. Nannobacteria Research, http://www.msstate.edu/dept/geosciences/4site/nannobacteria.htmC. H.D.A Lindquist, U.S. EPA, http://www.epa.gov/nerlcwww/index.html
50 nm
A B C
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Viruses: bioViruses: bio--nanonano--colloidscolloids
Two general shapes:icosahedral (twenty-sided)helical
(a) (b)
2
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Virus morphologyVirus morphology
Composition
Genome, either DNA or
RNA
Capsid protein: protect viral genome
attach to specific
receptor on host cell
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Waterborne Human VirusesWaterborne Human Viruses
Family Genera Note Picornaviridae Enterovirus Represent the largest fraction
of viruses detected in waterCause Hepatitis A, digestive
problems, juvenile diabetes, and poliomyelitis
Reoviridae Reovirus Cause serious inflammation of Rotavirus mucous membrane of stomach
and intestines in childrenCoronaviridae Coronavirus Cause serious bleeding
in the intestines in children Caliciviridae Calcivirus Cause some intestinal problem
Astrovirus in children Adenoviridae Mastadenovirus Cause diarrhea, respiratory&eye infection
hepatitis non-A, non-B
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Virus Contaminated SewageVirus Contaminated SewageRaw sewage
Primary
Secondary
Tertiary
WA
STE
W
ATE
R
SLU
DG
E
Ozone at0.3 ppmfor 2 min
Hypochlorousacid at 1 ppm
for 30 min
Incineration
Pasteurization at70oC in alkalinecondition, 60 min
Air-dryingweeks-months
Anaerobicdigestion50oC, 4 weeks
Composting well aerated
< 1%viruses
< 1%viruses
< 1%viruses
Nil virus
Nil virus
1%viruses
1%viruses
10%viruses
0-25%viruses
90%viruses
99%viruses
75-100%viruses
1%viruses
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Viruses in the EnvironmentViruses in the Environment
In rivers and oceanviruses can stay viable up to weeksrenewal rate is very high.
In sludge prior to land applicationviable up to 4 months
After application of sludge to soilviable up to 2-5 weeks
Viruses migrated from land application of sludge viable in groundwater up to 2 monthsviable in groundwater for at least 6 months at 10oC
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Colloid TransportColloid Transport
Environmental factors that affect colloid
transport
groundwater velocity
quantity, type and size of colloid
geometry of aquifer pores
media surface
ionic strength
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Fate and Transport of Viruses
SolidSolid
WaterWater
SuspendedSuspended
Attached Attached
Inactivated Inactivated
Inactivated Inactivated
SuspendedSuspendedV
3
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Early Breakthrough in Saturated Porous Media
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.70 0.80 0.90 1.00 1.10 1.20 1.30 1.40
Pore Volume
C/C
0
KClMS2
Commonly observed in column and field scale experiments
Hypotheses from field and core scale:
Hydrodynamic Chromatography (HDC)Size exclusion
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Hydrodynamic Chromatography
rr
r
Small, H., J. Colloid Interface Sci.48:1, 147 (1974)
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Experimental Setup
Inlet
Pressurizedreservoir
Microscope
Inlet valveto micromodel
Micromodel
VideoCamera
Video image
VCR/monitor
PC with videocapture boardOutlet
PEG*Pump
*Polyethylene Glycol Solution
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
100 µm 100 µm 100 µm 100 µm 100 µm
11
2
13
10
14
12
16
15
9
4
5
7
3
6
8
1
1 2
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
97%
3%
97%3%
7%93%
1) 14%
6) 58%
7) 28%
3) 36%
2) 22%
4) 14%
5) 14%
3 µm colloids 2 µm colloids
1 µm colloids 0.05 µm colloids
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.70 0.80 0.90 1.00 1.10 1.20 1.30
C/C0
KClModel fir for KCl0.05umModel fit for 0.05um
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.70 0.80 0.90 1.00 1.10 1.20 1.30
C/C0
KClModel fit for KCl3umModel fit for 3um
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.70 0.80 0.90 1.00 1.10 1.20 1.30
C/C0
KClMOdel fit for KClMS2Model fit for MS2
Pore Volume
Breakthrough curves for average water velocity = 1.4 m/d
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Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Connection to the larger scaleExplains findings at larger scale:
Earlier breakthrough for larger colloids
Early breakthrough increases with fluid velocity
Less dispersion of
Colloids relative to conservative tracer
Larger colloids relative to smaller colloids
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Fate and Transport of Colloids
SolidSolid
WaterWater
SuspendedSuspended
AirAir
Attached Attached
Attached Attached Inactivated Inactivated
Inactivated Inactivated
Inactivated Inactivated
SuspendedSuspended
Attached Attached
V
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 41%Direction of flow
Air
Water
Solid
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
First Flush 12 sec after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 76%26 sec after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 78%38 sec after flush
5
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content:78%51 sec after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 79%1 min 04 sec after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 80%1min 12 sec after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 82%1min 28 sec after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 83%1min 39 sec after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 83%1min 55 sec after flush
6
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 84%10 min 09 sec after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 68%2 h 59 min after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 58%3 h 49 min after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 55%4 h 08 min after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 47%4 h 51 min after flush
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Water Content: 43%5 h 04 min after flush
7
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Effect of clusters
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Key Findings at Pore ScaleSorption onto AWI is “irreversible”
Colloids sorbed onto AWI can form clusters
Colloids sorbed onto AWI can be transported Along with the moving air bubble
As colloidal clusters
As water is remobilized
Colloids may also be at SWA interfacePromotes attachment to SWI
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Unsaturated ColumnSetup
Sample Collection
Conductivity Sensor
Pressure Transducers PumpFlow Meter
Injection Port
DI Water
Data AcquisitionSystem
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.0 0.5 1.0 1.5 2.0 2.5
C/Co
, KCl
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
C/Co
, Col
loid
s
KCl MS20.05 um 3 um
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.0 0.5 1.0 1.5 2.0 2.5
C/Co
, KCl
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
C/Co
, Col
loid
s
KCl MS20.05 um 3 um
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.0 0.5 1.0 1.5 2.0 2.5Pore volume
C/C
o, K
Cl
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
C/C
o, C
ollo
ids
KCl MS20.05 um 3 um
Breakthrough curves
forsteady water
contents
Sw = 44%
Sw = 37%
Sw = 27%
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Connection to larger scale
Under unsaturated conditions, steady-state water content, slow flow
Colloid breakthrough is low due to sorption at AWI
Sorption to solid interface can be significant due to low flowrates
Colloids trapped in immobile water
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
8
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Key Findings
Microbial retention rate is high: 99.972 % Retention is due sorption onto Air-Water Interface and irreversible attachment onto Soil-Water Interface.
Bren School of Environmental Science & ManagementUniversity of California, Santa Barbara
Conclusions
Significant storage of colloids under saturated and unsaturated conditionsModelling of colloid transport is important to understand the risk of mobilizationUnderstanding pore-scale mechanisms can
help guide larger-scale experimentsproduce better models