New technique for validation of UF membrane processes Alice Antony and Greg Leslie

19 Pages·2014·2.37 MB·English

New technique for validation of UF
membrane processes
Alice Antony and Greg Leslie
Overview
• Background
• Project outline
• Results
• Nanoparticles development
• UF challenge tests
• Conclusions & Future Work
Membrane validation
What is membrane validation?
Process of demonstrating that the system can produce water of the required
microbial quality under defined operating conditions and the system can be
monitored in real time assure the water quality objectives are continuously
met.
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
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 novel
integrity tests (completed in 2009)
Critical Reviews in Environmental Science and Technology 42(9), 2012, 891-933.
Phase 2 – Development and testing of novel
integrity test (Completed in 2013)
Journal of Membrane Science 454, 2014, 193-199
Phase – 1 outcomes / Phase – 2 Objectives
o
Challenge test using MS2 bacteriophage, by plaque forming unit
enumeration, PFU is presently considered the best process indicator for
virus removal. However, the MS2 bacteriophage challenge test is difficult in
on a full scale plant on a regular basis1 (for revalidation)
• Developing a non-microbial indicator for challenge testing and challenge
testing on ultrafiltration membranes
o ≤
Existing integrity test methods are for breaches 1 µm; Identifying direct or
indirect integrity testing for detecting breaches less than virus-sized
particles (0.01 – 0.04 µm)is a necessary
• Testing size exclusion chromatography and fluorescent spectroscopy for
their sensitivity to detect membrane breaches in UF and RO membranes
1Water Research, 2002, 36(17): 4227-4234
MS2 challenge testing
Testing with native Viruses (NV)

s
• Low conc. in real scenario u
r
i
v
• Assay of NV is complex, time consuming, definite analysis o
i
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o
P
methodology is not available in some cases

• Issue of possible contamination

A
p
MS2 as a surrogate1,2,3 – Why and Why not? e
H

• Ablity to cultivate in high concentration

• sensitivity as high as 6LRV

k
l
a
w
r
o
• Impractical in full scale – high cost and effort N

• Long turnover time, 24 h

s
• Physicochemical retention vs. inadvertent biological inactivation u
r
i
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Particle aggregation may enhance the filtration capacity a
t
o
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• 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): 111-116
3Critical Reviews in Environmental Science and Technology, 2012, 42,891-933.
Non-microbial alternative
Non-microbial substitute
MS2 Phage
Citrate stabilized
silver (zerovalent)
nanoparticle
Diameter – 24 nm Virus sized
Spherically shaped
Icosahedral
Negatively charged at pH 7
Isoelectricpoint (pI) - 3.5-3.9, net
Stable during filtration
negative change above pH 3.9
Synthesis of nanoparticles
Silver nitrate solution
Boil
1% sodium
citrate solution
423 nm
Constant stirring for 1 hr)
spherical or roughly
spherical silver
nanoparticles1,2
Centrifuge, redisperse in water
1The Journal of Physical Chemistry B, 107 (2003) 6269-6275.
2The Journal of Chemical Physics, 116 (2002) 6755-6759.
Characterisation of Nanoparticles
concentration, size, charge & stability
Concentration of the finished
nanoparticles – Inductively
coupled plasma – Optical
emission spectroscopy
Size - as average
hydrodynamic size & charge by
a dynamic light scattering,
Brookhaven 90 Plus particle
sizer
Eff. diameter (hydrated) : 50 nm Charge: -25 mV (negatively charged)
Particle properties stable over 3 days
Characterisation of Nanoparticles
Transmission electron microscopy
• Near spherical shape, size ranging from 20 – 50 nm
• Crystal lattice pattern, d-spacing of 0.24 nm, characteristic of zerovalent
silver