Efficiency of MS2 phage and Qβ phage removal by membrane filtration in water treatment: Applicability of real-time RT-PCR method

MS2 phage is currently used as a surrogate to evaluate pathogenic virus removal efficiency by filtration membrane during water treatment. Phage removal is commonly defined upon comparing number of infectious units in permeate with that in feed solution by PFU method. This method may lead to overestimation of the virus removal because of possible occurrence of viruses aggregation. In this study, we report the removal efficiencies of various conventional membranes used in water treatment technology, with respect to suspensions of MS2 and Qβ bacteriophages. These phages – known to exhibit distinct interfacial characteristics in terms of electrostatic charge and degree of hydrophobicity – were used in conditions where viral particle aggregation is negligible. Under such conditions, the feasibility of fast, easy to handle, molecular biology method, i.e. real-time RT-PCR, for measuring virus removal rates is clearly addressed. Comparison of the results provided by this method with those obtained via more traditional procedure is given. On the basis of the filtration results, it is shown that Qβ phages are eliminated to a lower extent than MS2 phages, this being the case for all membranes considered here. Accordingly, the analysis questions the choice of MS2 phage as the best surrogate classically used for characterizing membrane virus removal propensity in worst possible conditions.