New Techniques for Real-Time Monitoring of Membrane Integrity for Virus Removal: Pulsed-Marker Membrane Integrity Monitoring System
Project: 09-06 (Phase B)
Year Released: 2014
Type: Scientific Investigation
Funding Partners: Bureau of Reclamation
Total Investment: $251,333 (Cash: $145,748, In-Kind: $105,585)
Principal Investigators: Val S. Frenkel, Ph.D., P.E., D.WRE., EKI – Erler & Kalinowski, Inc. and Yoram Cohen, Ph.D., University of California Los Angeles
The use of high pressure membrane processes, particularly reverse osmosis (RO), has grown significantly over the past few decades in water treatment and reuse applications to safeguard water supplies against harmful pathogens and impurities. In principle, RO membranes should provide a complete physical barrier to the passage of nanosize pathogens (e.g., enteric viruses). However, in the presence of imperfections and/or membrane damage, membrane breaches as small as 20 to 30 nm in diameter can allow enteric viruses to pass through the membrane and contaminate the product water stream, thereby posing a potential health hazard that is of particular concern for potable water production.
Goals and Objectives
This project was designed to develop a system and approach for real-time integrity monitoring of high pressure reverse osmosis/nanofiltration (RO/NF) membrane systems by using pulsed dosing and online detection of fluorescent molecular markers (i.e., tracers), referred to herein as pulsed-marker membrane integrity monitoring (PM-MIMo). The primary goal of the PM-MIMo system and approach was to reliably monitor virus removal capability of RO/NF membranes for regulatory compliance purposes.
Findings and Conclusions
- A molecular marker approach using uranine (commercially available fluorescent marker) was evaluated for monitoring of RO membrane integrity.
- The current approach is suitable for marker LRV quantification up to 4 or higher.
- The PM-MIMo approach for detecting membrane breaches was established in a series of experiments using a diagnostic PFRO system with intact and damaged (mechanically and via exposure to chlorine) flat-sheet membrane coupons.
- A membrane integrity breach increases the degree of convective passage through the membrane, as indicated by a decrease in the marker reflection coefficient.
- The fraction of total marker passage for a given monitoring period can be correlated with membrane breach size and location.
- The molecular marker approach can be adapted for real-time RO membrane integrity detection and characterization as a method that is in compliance with regulatory requirements
- The feasibility of the PM-MIMo approach for monitoring the integrity of spiral-wound RO elements was tested by using a bench-scale SPRO pilot plant with intact and damaged (mechanically and via exposure to chlorine) membrane elements.