An evaluation of virus removal mechanisms by ultrafiltration membranes using MS2 and φX174 bacteriophage

• MS2 and φX174 bacteriophage removal by ultrafiltration membranes was evaluated.
• Size exclusion was predicted by modeling, and found to be the main removal mechanism for both viruses.
• MS2 removal at pH 7.6 was higher than φX174 either at pH 6.5 and 9.4.
• The role of electrostatic repulsion and adsorption in removal was different for MS2 and φX174.

Low pressure membranes are a widely used drinking water treatment technology to reject particles and microbiological contaminants. A commercial UF membrane was used to investigate the removal of two virus surrogates (MS2 and φX174 bacteriophage) of similar size but with different surface characteristics. MS2 was better removed than φX174 regardless of its smaller size. φX174 removal was found to decrease significantly as the feed solution pH increased from 6.5 to 9.4. Using mathematical modeling, size exclusion was confirmed to be the main removal mechanism for both bacteriophage. These values were then compared with experimental results and virus characteristics to evaluate the contribution of other removal mechanisms. The additional removal for MS2 above baseline size exclusion was likely a result of electrostatic repulsion. For φX174, adsorption was shown to increase rejection at pH 6.5, but at pH 9.4 removal was due solely to size exclusion. The higher isolectric point of φX174, along with its complex capsid structure, are believed to be responsible for the different removal patterns between the two phage types.