New technique for validation of UF membrane processes Alice Antony and Greg Leslie PDF
Preview New technique for validation of UF membrane processes Alice Antony and Greg Leslie
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 l 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 v Particle aggregation may enhance the filtration capacity a t o R • 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
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