S. Majid Hassanizadeh Faculty of Geosciences Utrecht

12/9/2012 1

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VIRUS TRANSPORT IN SOIL AND GROUNDWATER

Field and Laboratory Experiments and Modelling

S. Majid Hassanizadeh Faculty of Geosciences; Utrecht University

Soil and Groundwater Systems, Deltares

in collaboration with:Jack Schijven (National Institute of Public Health and the Environment)Reza Sadeghi (Utrecht University); Experiments on IS, pH, CaZhang Qiulan (Utrecht University); Visualization of colloids movementNikos Karadimitriou (Utrecht University); Visualization of colloidsS. Torkzaban (CSIRO, Adelaide); Unsaturated experiments

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MOTIVATIONDune infiltration of pretreated surface water14 % (=181×106 m3/year) of drinking water production

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Aerial View of Castricum Dune Infiltration Area

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Schematics of Castricum Infiltration Canals

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MOTIVATION

Concentrations of enteroviruses in surface water: 20 to104 viruses/m3

Maximum allowable drinking water concentration is 2× 10-4 viruses/m3 (based on a allowable risk of infection of 10-4 per person per year).

A removal of about 8 log10 by dune passage is required.

Dune infiltration of pretreated surface water

Removal of 1 - 2 log10 achieved by pretreatment.

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Deep well injection of surface water

River bank filtration and water production

Use of (domestic) wastewater in agriculture or for aquifer recharge

Disposal of septic tank effluents in soil

Disposal of domestic wastewater in shallow wells

MOTIVATION

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PROCESSES INVOLVED

AdvectionDispersionAttachment/DetachmentInactivationGrowth?Relevant to other reactive transport problems and colloid transport

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Main Question

How far do viruses travel once they enter soil and groundwater?

Reported distances are anywhere between a few meters to a few kilometers!

Large number of factors can influence the process. Major factors are different under different additions.

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Research Questions

What are the roles of equilibrium and kinetic adsorption?In the case of kinetic, is a first-order one-site model sufficient (should we consider blocking)?What is the influence of geochemical and environmental conditions (pH, lS, Ca, P, OC, T)?What is the influence of soil moisture?What is the influence of transient conditions?

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OUTLINE OF PRESENTATIONIntroduction

Influence of pH, IS, and Ca2+

Influence of moisture content

Influence of transient conditions

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For laboratory and field experiments we use MODEL VIRUSES

Why are they needed?

To do a field study, we need very large concentrations (order of 108 viruses per liter).

It would be hard to get permission to introduce even a small amount of pathogenic micro-organisms into groundwater.

So, we use model viruses as surrogates for pathogenic micro-organisms in field studies.

Using pathogenic viruses in the lab requires special facilities and imposes major operational restrictions.

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Model virusesBacteriophages as model for enterovirusesThey are harmless to human beingTheir host is not present in nature;They have properties similar to pathogenic virusesMS2– 26 nm– Isoelectric point at pH 3.9– Partly hydrophobic

PRD1– 62 nm– Isoelectric point at pH 3.4– Partly hydrophobicφX174– 25 nm– Isoelectric point at pH 6.6– Hydrophilic

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Castricum field study on dune recharge

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Castricum Field Study: Short DescriptionAn area of 6x12 m in an infiltration canal was sheet walled.

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Castricum Field Study

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Castricum Field Study Breakthrough Curves of Salt, MS2, and Model results

PCO2 (2.4 m)

1.E-02

1.E+00

1.E+02

1.E+04

1.E+06

0 25 50 75 100 125

C (p

fp/l)

100

1000

10000

EC (μ

S/cm)

ObservationModelBelow detection limitEC

PCO3 (3.8 m)

1.E-02

1.E+00

1.E+02

1.E+04

1.E+06

0 25 50 75 100 125

C (p

fp/l)

100

1000

10000

EC (μ

S/cm

)

PCO4 (6.4 m)

1.E-02

1.E+00

1.E+02

1.E+04

1.E+06

0 25 50 75 100 125

C (p

fp/l)

100

1000

10000

EC (μ

S/cm)

PCO5 (10 m)

1.E-02

1.E+00

1.E+02

1.E+04

1.E+06

0 25 50 75 100 125Day

C (p

fp/l)

100

1000

10000

EC (μ

S/cm)

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Modeling breakthrough of MS2 (Castricum data)One-site kinetic adsorption model

1.E+02

1.E+04

1.E+06

0 25

C (N/l)

100

1000

10000

EC(μS/cm)

ObservationModel simulationEC

MS2; L=2.4 m

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Modeling breakthrough of MS2 (Column I);one-site and two-site kinetic models

0.000001

0.0001

0.01

1

0 24 48 72 96 120 144 168 192

Time [hours]

b

c

a

C/C0

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Modeling breakthrough of MS2 (Column I);one-site and two-site kinetic models

Rate coeff’s (day-1)

Curve a one site

Curve b one site

Curve ctwo site

katt1 4.8 2.6 2.0 kdet1 6.7 0.065 0.065 katt2 3.36 kdet2 13.7 μs1=μs2 5.8 0.43 0.43 Goodness of fit

98% 92% 98%

0.000001

0.0001

0.01

1

0 24 48 72 96 120 144 168 192

Time [hours]

C/C0b

c

a

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Conclusions from field and Laboratory experiments about adsorption models

Site 1: katt1 >> kdet1 (strong adsorption)

Site 2: katt2 < kdet2 (weak adsorption)

Site 2: Improves model fit to data

Site 1: Contributes MOST to virus removal

Site 2: Contributes LITTLE to virus removal

A one-site kinetic model is sufficient for all practical purposes.

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Virus transport under various geochemical conditions (pH, IS, Ca2+,T)

G. Sadeghi (UU)J. F. Schijven (RIVM)S. M. Hassanizadeh (UU)T. Behrends (UU)

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Batch experiments

Inactivation experiments

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Column set-up

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Column experimentsSaturated clean quartz sand in 50-cm columnsWater composition, pH, IS, and temperature were carefully regulated and kept constantAverage pore velocity of 8.3 cm/hPulse of PRD1 with a duration ≈1 PVExperiments were performed at various combinations of constant pH, IS, and Ca2+

Experimental with transient Ca2+ concentration were performed too.

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Breakthrough Curves of PRD1 at different pH values; IS 1

IS 1pH 8pH 7pH 6pH 5

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

0 2 4 6 8 10PV

C/C0

26


0.000001

0.00001

0.0001

0.001

0.01

0.1

1

0 2 4 6 8 10PV

C/C0


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0.000001

0.00001

0.0001

0.001

0.01

0.1

1

0 2 4 6 8 10PV

C/C0

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Modelling Breakthrough curvesExperiments at different pH and IS

Fitting with Hydrus-1D: katt and kdet values

IS 1 mMkatt increases a little if pH decreases

IS 10 mMkatt increases strongly for pH 5

IS 20 mMkatt increases strongly for pH 5 and 6

Effect on kdet unclear


0.000001

0.00001

0.0001

0.001

0.01

0.1

1

0 2 4 6 8 10PV

C/C0


0.000001

0.00001

0.0001

0.001

0.01

0.1

1

0 2 4 6 8 10PV

C/C0


0.000001

0.00001

0.0001

0.001

0.01

0.1

1

0 2 4 6 8 10PV

C/C0

IS pH 8 pH 7 pH 6 pH 51mM 0.0045 0.041 0.070 0.1110mM 0.038 0.040 0.14 0.8020mM 0.11 0.21 0.55 2.0

katt h-1

IS=1

IS=10

IS=20

katt (h-1)

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Empirical formula for sticking efficiency αas a function of pH and IS

katt values =>sticking efficiency α(Colloid Filtration Theory)

3(1 )2att

c

k vdφα η

⎡ ⎤−= ⎢ ⎥

⎣ ⎦

0.50 0.13IS pHeα − + −=

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Comparison with values from the literatureTrend given by empirical formula is consistent with literature values for sticking efficiencies above 10-4

-4

-3

-2

-1

0

1

-4 -3 -2 -1 0 1

log α model

log α

mea

sure

d

MS2-Columnλ-columnPRD1-field

Log α given by formula

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Column Experiments at different Ca2+ concentrations

0.0000010.00001

0.00010.001

0.010.1

1

0 5 10 15 20 25 30 35 40PV

C/C

0 Ca 0

0.0000010.00001

0.00010.001

0.010.1

1

0 5 10 15 20 25 30 35 40PV

C/C

0

Ca 20

Ca 60

Ca 120

[Ca2+] =0

[Ca2+] =20 mg/l[Ca2+] =60 mg/l

[Ca2+] =120 mg/l

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katt (h-1)

Ca2+ (mg/l)

katt (h-1)=0.011[Ca2+](mg/l); R=1

Attachment Coefficient as a function of Ca2+

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Sticking efficiency as a function of Ca2+

α=0.00056[Ca2+](mg/l); R=1

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0.000001

0.00001

0.0001

0.001

0.01

0.1

1

0 10 20 30 40 50 60 70

C/C

0

PV

Column experiments with transient Ca2+

concentrations

120 mg/l

Switching to Ca2+-free soln.

60 mg/l

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Effect of soil moisture on virus removal

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Why study unsaturated conditions?It is the first line of defense against groundwater pollution

Leakage from sewers

Use of (domestic) wastewater in agriculture

Disposal of septic tanks effluents in soil

Disposal of domestic wastewater in shallow wells

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Saturated/Unsaturated Processes on MicroscaleAttachment to Solid-Water Interface (SWI), Air-Water Interface (AWI) and Air-Water-Solid (AWS) Contact line Inactivation occurs in water, at SWI and AWI, and AWS

Solid grainSolid grain

Solid grain

Solid grainSolid grain

Solid grain

Air

Air

UnsaturatedSaturated38

In general, more colloids are retained in unsaturated media compared to saturated media

(Wan et al., 1994)(Wan et al., 1994)

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Role of AWIUsing glass micromodel and fluorescent microscopy, Wan et al., (1994) found that “colloids are preferentiallyattached to AWI”

This concept dominated the thinking for ~10 years

solid

water air

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Why is there enhanced removal under unsaturated conditions?

Inconsistent reports in literature:Attachment to the AWI (Wan and Wilson, 1994a,b; Schafer et al., 1998a; Cherrey et al., 2003; Torkzaban et al., 2006b)Increased attachment to the SWI (Chu et al., 2001; Lance and Gerba, 1984; Torkzaban et al., 2006a)Contact line (or the AWS triple phase line) is the primary retention site for colloids (not AWI!) (Wan and Wilson, 1994a,b; Crist et al., 2004; Schafer et al., 1998a; Cherry et al., 2003; Torkzaban et al., 2006b)Enhanced sorption/inactivation at AWS (Thompson et al., 2004)Film straining in water films enveloping the solid phase (Wan and Tokunaga, 1997; Saiers and Lenhart, 2003)

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Experiments conducted in saturated and unsaturated (21% sat.) sand columns

Virus removal increased under unsaturated flow conditions – attachment to air‐water interface (AWI)

Increased removal of φX174 due to reversible sorption

Increased removal of MS2 due to inactivation

φX174

MS-2

Examples of virus transport in unsaturated media

(Jin et al., JCH, 2000)

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(Chu et al., JEQ, 2003)

Experiments conducted in five soils

Virus removal under unsaturated conditions increased in some soils but not in others

Water content effect on virus removal strongly affected by the properties of the solid phase

MS-2

0.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10 12Pore Volume

C/C

o

Sat.Unsat.

0.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10 12Pore Volum e

C/C

o

Sat.Unsat.

CA soil

DE soil


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Experiments using water‐washed and oxide‐removed sands

Virus removal increased with decreasing water content in both sands

Water content effect less significant in the ‘inert’ sand – AWI did not play a dominant role


1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 2 4 6 8 10

Pore Volume

C/C

0

100% of saturation71% of saturation21% of saturation

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 2 4 6 8 10 12

Pore Volume

C/C

0

100% of saturation61% of saturation26% of saturation

Water‐washed sand

Oxide‐removed sand

(Chu et al., WRR, 2001)

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Description of column experimentsAll experiments conducted under steady state and uniform

water content. These two conditions are very important.Water pressure and water content were measured.Virus concentration measured at the outlet.

TensiometerTDR

Hangingtube

(Torkzaban et al., VZJ, 2006 and WRR, 2006)45

Stock suspension

PumpShaker

Data Logger

Porous plate

Fraction collector

Tensiometers

P.C.

TDR

Adjustable tube

soil

Schematic of experimental set-up

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Experiments with sand

Virus removal increased with decreasing water content

Water content effect less significant at high pH and low ionic strength (not shown)

Increased retention due to increased attachment to solid‐water interface (SWI)?


(Torkzaban et al., VZJ, 2006)

At pH 7 and ionic strength 19 mM

Sw= 100%

Sw= 66%

Sw= 52%

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Overview of experimental conditionsExperiment pH Ionic

strength (mM)

Saturation(%)

Pore velocity

(cm/min)

HpLi100 9 0.6 100 0.68

HpLi65 9 0.6 65 0.56

LpHi100 7 19 100 0.68

LpHi66 7 19 66 0.7

LpHi52 7 19 52 0.45

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Virus adsorption in unsaturated zone

Equations solved numerically using HYDRUS

( ) ( )ww w w w s a

C C C C r rt

θ θ μ θ∂= ∇• •∇ −∇• − − −

∂D q

Adsorption to the AWI:

a aaa a a att w det a a a

aC r aC k C k aC aCt

μ θ μ∂= − = − −

∂

Adsorption to the SWI:s sb s

s s b s att w det b s s b sC r C k C k C Ct

ρ μ ρ θ ρ μ ρ∂= − = − −

∂

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0.0001

0.001

0.01

0.1

1

10

0 5 10 15 20 25 30 35Time (P.V)

C/C0

MS2FiX174

Breakthrough curves for LpHi65 experiments65% saturation; two-site kinetic model

C/C0

Time (P.V.)50

Estimation of adsorption coefficients

detsk a

attkadetk

sattk ×103 min-1 ×103 min-1 ×103 min-1 ×103 min-1 R2 (%)

φX174

LpHi100 8.2± 1.7 1.4 ± 0.2 88

LpHi66 13 ± 1.4 1.5 ± 0.3 90

LpHi52 15 ± 1.1 1.7 ± 0.14 94

MS2

LpHi100 3.7±1.1 0.030±0.010 98

LpHi66 5.1±1.2 0.010±0.006 0.50±0.05 22±2.3 97

LpHi52 6.4±1.5 0.010±0.009 0.80±0.02 25±2.5 94

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Estimation of adsorption coefficients

Experiment φX174 MS2

HpLi100 0.02 0.002

HpLi65 0.1 0.004

LpHi100 5.8 123 0.005

LpHi66 8.6 510 0.02

LpHi52 8.8 640 0.03

sDK

aDKs

DK

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Proposed removal mechanisms in unsaturated media

(Bradford and Torkzaban, VZJ, 2008)

Attachment to solid‐water interface (SWI, 1)Attachment to air‐water interface(AWI, 2)Film straining (5) in water films enveloping the solid phaseRetention at the solid–air–water triple point or the contact line (6)Straining, wedging, or bridging (3,4, 7)

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Colloids/Virus Transport under Transient Hydraulic Conditions

BTC, Modeling, Visualization Experiments

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天津

Why should we be interested in transient flow conditions?

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Colloid and virus remobilization in unsaturatedporous media has been found during both drainageand imbibition columns.Transient flow caused by rainfall, irrigation,evaporation, snowmelt and water level fluctuationsmainly present in unsaturated zone.Mobilized colloids can serve as carriers andfacilitate contaminant transport in both vadosezone and groundwater.Mobilized viruses may cause unexpected pollution.

56Cheng and Saiers, Water Resour Res, 2009

Transient Column Experimentsmulti-pulse drainage /imbibition events.

Time57

det det1 ( )s ii

att i s i ib C

S k C k S S k t St N

θ μρ

∂= − − −

∂　　　　

Detachment coefficient as a function of saturation changes.

Remobilization occurs in pores that are being drained or imbibed. Larger pores are drained first and smaller pores are imbibed first. So, based on pore size distribution, pore space is subdivided into a number of compartments (Cheng and Saiers, WRR, 2009).

Then, adsorption to SWI can be written as:

1( )

Ncs s ibatt det b s b det i

i

S k C k S S k St

ρ θ ρ μ ρ=

∂= − − −

∂ ∑

Modeling virus transport under transient flow conditions

det 0isik for h h= > det

id sik N for h htθ∂

= ≤∂

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(Torkzaban, Hassanizadeh, Schijven; Vadose Zone Journal, 2006)

Drainage from initial saturation 65%

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At the end of a steady-state experiment (saturation 50%), the column was resaturated with clean water to almost full saturation, and after that, it was drained.

Imbibition-drainage Experiment

0.0001

0.001

0.01

0.1

1

0 20000 40000 60000 80000 100000 120000

time(s)

Concentration C/C0

simulation

observation

Initial saturation 50%

(Torkzaban, Hassanizadeh, Schijven, Water Resour. Res, 2006)60

A B

C

A: Remobilization breakthrough during drainage started from fully saturated column.

B:Remobilization breakthrough during drainage from saturation 65%.

C: Remobilization during imbibition-drainage condition.

Modeling remobilization part by Cheng and Saiers Model

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A B

C

A: Remobilization breakthrough during drainage started from fully saturated column.

B:Remobilization breakthrough during drainage from saturation 65%.

C: Remobilization during imbibition-drainage condition.

Modeling remobilization part by Cheng and Saiers Model Extended to include adsorption to and remobilization from air-water interfaces

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(Zhang et al.,1996)

Role of air-water interfaces

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Pore-scale Visualization Experiments

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outlet reservoir

flow network

inlet path

inlet reservoir

flow channel

Detailed structure of the micro-model

Three inlet reservoirs and paths are for fluorinert, colloid-water suspension, pure water respectively. 65

Experimental Set-up

66

The whole set-up

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Colloid attachment at AWI

water

fluorinert

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Colloid attachment at AWS contact line

Colloids accumulation at the triple point where fluorinert, water, and PDMS solid surface meet was clearly observed under confocal microscope.

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1) Colloid remobilization under transient water flow conditions is highly dependent on the changes in water content;

2) Breakthrough curves represent an aggregated response of different mechanisms of colloids transport and mobilization;

3) In steady-state unsaturated PDMS micro-model, retention of colloids at SWI, AWI, and AWS contact line was observed.

4) Currently visualization experiments of colloids transport under transient hydraulic conditions (drainage/imbibition) are underway to quantify colloid retention, mobilization with the moving AWIs and AWS contact lines.

Conclusion and Discussion

Documents

S. Majid Hassanizadeh Faculty of Geosciences Utrecht