Integrity monitoring of reverse osmosis membranes: Potential for naturally present viruses to verify virus removal comparing to MS2 bacteriophages

Reverse osmosis membrane filtration is becoming an interesting solution since it is in principle an effective barrier against pathogenic microorganisms in water. Although having the ability to treat many water sources and provide safe drinking water, viruses are the smallest pathogenic microorganisms and therefore the most challenging to verify their removal in membrane filtration. For a reverse osmosis filtration system to be secure to public health, a trustful membrane integrity monitoring method is crucial to detect damages. The use of MS2 phages is currently the most used challenge test to validate virus removal in RO membranes. Although it has numerous advantages such as their similarity in size and morphology to enteric human viruses, it still has the drawbacks of being spiked in the feed water and not being feasible in full-scale plants. This dissertation focused on assessing the potential of a new challenge test that uses naturally occurring viruses in surface water to validate virus removal in RO membranes. This is a promising method since it discards the need of introducing components into the feed water thus being applicable to drinking water plants. Using a reverse osmosis pilot scale, experiments were performed using intact and damaged spiral wound membranes to assess the potential of using natural present viruses in surface water for validating virus removal in comparison with the performance of the already known good method – MS2 bacteriophages. The findings in this research demonstrate that both MS2 and naturally present viruses challenge tests achieved above 7 log removal values in the presence of intact membranes. Compromised membranes with induced pinholes achieved different log removal values according to the severity of the inflicted damages indicating sensitivity to detect impairments by both challenge tests. Greater loss of membrane integrity was observed when four pinholes with 1-mm diameter were inflicted on the membrane, followed by one 4- and one 1-mm diameter. Based on the consistency of the achieved log removal values between the two challenge tests, these results therefore demonstrate the potential of using natural present viruses to verify virus removal, particularly the suitability of the natural virus used in this research to be an adequate virus removal indicator