11. Antony RealTimeMonitoringVirus

8/10/2019 11. Antony RealTimeMonitoringVirus

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New technique for validation of UF

membrane processes

Alice Antony and Greg Leslie


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Overview

Background

Project outline Results

Nanoparticles development

UF challenge tests

Conclusions & Future Work


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Membrane validation

What is membrane validation?

Process of demonstrating that the system can produce water of the requiredmicrobial quality under defined operating conditions and the system can be

monitored in real time assure the water quality objectivesare continuouslymet.

How is this performed?

Through challenge test and operational integrity monitoring tests.What guidance do we have?

1. Membrane filtration guidance manual (MFGM)1

2. Guidelines for validating treatment processes for pathogen reduction Supporting Class A recycled water schemes in Victoria2

1MFGM, USEPA, 2005 2Department of Health, Victorian Government, February 2013


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New techniques for real time monitoring of membrane

integrity for virus removal -Project outline

Phase 1 - Review of literature, identification of

knowledge gaps and recommendation of novelintegrity tests (completed in 2009)Critical Reviews in Environmental Science and Technology 42(9), 2012, 891-933.

Phase 2 Development and testing of novelintegrity test (Completed in 2013)Journal of Membrane Science 454, 2014, 193-199


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Phase 1 outcomes

o Challenge test using MS2 bacteriophage, by plaque forming unitenumeration, PFU is presently considered the best process indicator forvirus removal. However, the MS2 bacteriophage challenge test is difficult inon a full scale plant on a regular basis1 (for revalidation)

Developing a non-microbial indicator for challenge testing and challengetesting on ultrafiltration membranes

o Existing integrity test methods are for breaches 1 m; Identifying direct orindirect integrity testing for detecting breaches less than virus-sizedparticles (0.01 0.04 m)is a necessary

Testing size exclusion chromatography and fluorescent spectroscopy fortheir sensitivity to detect membrane breaches in UF and RO membranes

1Water Research, 2002, 36(17): 4227-4234

/ Phase 2 Objectives


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MS2 challenge testing

Rota

virus

Norwalk

HepA

PoliovirusTesting with native Viruses (NV) Low conc. in real scenario

Assay of NV is complex, time consuming, definite analysismethodology is not available in some cases

Issue of possible contamination

MS2 as a surrogate1,2,3Why and Why not?

Ablity to cultivate in high concentration

sensitivity as high as 6LRV

Impractical in full scale high cost and effort

Long turnover time, 24 h

Physicochemical retention vs. inadvertent biological inactivationParticle aggregation may enhance the filtration capacity

PFU does not provide tools to control denaturation and aggregation

1Journal of Applied Microbiology , 2007, 103(5): 1632-1638, 2Journal of Membrane Science, 2009, 326(1): 111-1163Critical Reviews in Environmental Science and Technology, 2012, 42,891-933.


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Non-microbial alternative

MS2 Phage

Diameter 24 nm

Icosahedral

Isoelectricpoint (pI) - 3.5-3.9, netnegative change above pH 3.9

Non-microbial substitute

Citrate stabilizedsilver (zerovalent)

nanoparticle

Virus sizedSpherically shaped

Negatively charged at pH 7Stable during filtration


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Synthesis of nanoparticles

Centrifuge, redisperse in water

1% sodiumcitrate solution

Boil

Silver nitrate solution

Constant stirring for 1 hr)

spherical or roughlyspherical silvernanoparticles1,2

1The Journal of Physical Chemistry B, 107 (2003) 6269-6275.2The Journal of Chemical Physics, 116 (2002) 6755-6759.

423 nm


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Characterisation of Nanoparticles

concentration, size, charge & stabilityConcentration of the finishednanoparticles Inductivelycoupled plasma Optical

emission spectroscopySize - as averagehydrodynamic size & charge bya dynamic light scattering,

Brookhaven 90 Plus particlesizer

Eff. diameter (hydrated) : 50 nm Charge: -25 mV (negatively charged)

Particle properties stable over 3 days


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Near spherical shape, size ranging from 20 50 nm

Crystal lattice pattern, d-spacing of 0.24 nm, characteristic of zerovalentsilver

Characterisation of Nanoparticles

Transmission electron microscopy


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Challenge testing

Membrane - PVDF, UF membranes, average pore size - 0.04 m

Effective membrane area - 0.025 m2

Flux - 30 or 50 L m-2 h-1

Feed solution Clean water with 5, 10 & 20 mg L-1 of silver

nanoparticles

Parameters measured and/or compared Clean water flux, TMP

Change in TMP as a function of time, due t fouling of nanoparticles


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Challenging compromised membranes with nanoparticles

Physical compromise through punctures and cuts

Chemical damage

o Exposure to hypochlorite solutions (Ct) of 2,500, 5,000, 10,000,15,000 and 20,000 mg L-1.h

o Equivalent to a total exposure of 3.5, 6.9, 13.9, 20.8 and 27.8months at 1mg/L concentration over multiple uses

SEM imagesof the

puncturesmade with a100 mdiameterneedle


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Challenge testing contd.,

LRV and TMP change during the testing of intact UF membrane

Flux,(L m

2h

-1)

Nanoparticleconcentration,

(mg L-1

of Ag)

LRV

30 5 2.340.09

30 10 2.610.10

30 20 2.940.09 50 5 2.310.10

50 10 2.610.10

50 20 2.830.10

LRV ranging from 2.3 to 2.9 was demonstrated without any impact on theoperating flux

Slightly high LRV could be established with high nanoparticle concentration


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One puncture,compromise ratio was0.00003% and the LRV

decreased from 2.8 to 1.5

Four successive holes, theLRVs reduced to 1.1, 0.6,0.5 and 0.3, respectively

After three cuts, rejectionwas 7.1 % and LRV


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Realistic representation of theimpairment taking place in an

operational plant with routineuse of chemicals

At 2500 and 5000 mg L-1.h, themembrane resistance (Rm)

decreased to 19 and 38%, butthe rejection capacity wasalmost unaffected

Exposure to high concentrations

seem to affect both theresistance and rejection


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Summary MS2 vssilver nanoparticles

Criterion Microbial indicators, bacteriophagesCitrate stabilised silver

nanoparticles

Analysis, leadtime

Long, 24 h to measure the integritybreach

Small, using onsite measurementtechniques

Generation labour intensive, needs PC2 Relatively low labour requirements

PlantPreparation

High levels of disinfection of samplepoints and preventative measures to

avoid contamination

Non-microbial, very little risk ofcontamination by outside sources

Safety/hazards Host bacteria require microbial safetyprocedures

Minimal PPE

Backgroundinterference

Potential chances of interference frombackground virus and bacteria

Low Ag conc. In background

Measurement

limitations

PFU method may suffer from limitations

due to viral aggregationNo known limitations

Indicatorrigidity

Potential to deform under high pressureand pass through the membrane

Unlikely to deform under highpressure


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4 Key Conclusions

Demonstrated the suitability of newcitrate stabilised silver nanoparticles asvirus surrogates in terms of shape, size,

rigidity, charge and ease of detection Demonstrated close to 3 LRV of virus

removal for intact UF membranes

Demonstrated the sensitivity of the

system to differentiate intact membranefibres from those with a low number ofphysical breaches or chemicaldegradation

Demonstrated the potential for thevalidation of UF membranes in recycledwater applications


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Project is complete..however..

Would like to work

with a water utility to use these particles in

the field on the recovery of silver nanoparticles


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Acknowledgements

11. Antony RealTimeMonitoringVirus

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