New techniques for real-time monitoring of reverse osmosis membrane integrity for virus removal

Abstract

This paper presents methodology, concept and results of the WateReuse Foundation project WFR – 09 – 06b when developing a high pressure membrane, reverse osmosis (RO) and nanofiltration (NF) online membrane integrity testing (MIT) technique. The use of pressure-driven membrane processes, particularly 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 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. This project was focused on evaluating a pulsed-marker membrane integrity monitoring (PM-MIMo) approach for RO processes on the basis of the use of a fluorescent marker. The monitoring approach employs pulsed dosing (via a precision metering pump) of a marker into the RO feed stream coupled with online marker concentration monitoring in the RO permeate by an inline spectrofluorometer. Membrane integrity is then inferred on the basis of real-time analysis of the marker permeate time − profile concentration in response. The basic concept of the PM-MIMo approach for detecting membrane breaches was successfully demonstrated, by comparing intact and damaged membranes, in a series of experiments using a diagnostic plate-and-frame RO system and spiral-wound RO pilot system. Results of the developed technique are presented in the project report to allow the industry to consider adopting this technique for RO/NF online integrity monitoring.

A critical review on the existing wastewater treatment methods in the COVID-19 era: What is the potential of advanced oxidation processes in combatting viral especially SARS-CoV-2?

“…In laboratory systems, RO membranes have shown to achieve higher than 5-log removal values (LRV) of viruses [68] , [69] . Also, this kind of research has been performed in pilot-scale systems [70] , [71] . LRV measures the efficiency with which a target, such as a particle, organism, or surrogate, is eliminated or inactivated.…”

Membrane integrity monitoring on laboratory scale: Impact of test cell-induced damage on membrane selectivity

“…Non-biological surrogates consisted of two fluorescent markers, pyranine (MW: 524.40 g/mol; λex/em = 370/513 nm) and R-WT 20% w/w solution (MW: 567 g/mol; λex/em = 550/580 nm) (Sigma-Aldrich, Germany), which were quantified by fluorescence spectroscopy, and sodium chloride salt (NaCl), quantified by electrical conductivity. The markers are commonly available and non-toxic [23] [24] [25]. Feed marker concentrations were adjusted, such that a minimum LRV of 4 could be measured considering the detection limit (pyranine at 0.1 mM and R-WT at 2.6 uM).…”

The role of wastewater treatment plants as tools for SARS-CoV-2 early detection and removal

“…Frenkel and Cohen [ 175 ] proposed new techniques for real-time monitoring of reverse osmosis membrane integrity for virus removal. They proposed a pulsed marker membrane integrity monitoring system.…”