Challenge tests with virus surrogates: an accurate membrane integrity evaluation system?

Abstract

The use of membrane filtration in drinking water treatment has significantly increased in the last decades due to its advantages, including its capacity to produce water of high quality with a high level of pathogens rejection. However, if membrane integrity is compromised, this feature cannot be guaranteed, increasing the associated microbial risk of the treated water. This study has focused on the development and application of a protocol based on virus surrogates challenge tests applicable to the three existing ultrafiltration (UF) configurations. The operational conditions have been defined, and the tests have been conducted successfully. The selected micro-organisms, PDR-1, MS-2, GA and Bacillus spores, present different characteristics providing complementary information of membrane integrity and its status. In particular, PDR-1 and Bacillus spores, due to their larger size, are mainly removed by size exclusion and low removal rates may indicate membrane impairment. MS-2 and GA, 25 nm in size approximately, may not be rejected by size exclusion but by adsorption and electrostatic interactions, so that their removal values may not necessarily be indicative of membrane integrity failures. Since they may be influenced by further factors, such as membrane characteristics, feed water quality, non-chemically removable fouling, etc., the results obtained can be used to better understand membranes performance.

Keywords:

• Membrane integrity
• Viruses surrogates
• Bacteriophages
• Bacillus spores
• Cryptosporidium
• Ultrafiltration
• Pressure decay test

Acknowledgements

This work has been conducted under the financial support of the LIFE+ Programme of the European Commission within the framework of the UFTEC Project (LIFE09 ENV/ES/000467 UFTEC). The authors gratefully acknowledge Xavier Serrallach (CETaqua), Verónica García-Molina (Dow Chemical Ibérica) and BastiaanBlankert (Pentair X-Flow) for their technical contributions in this work.

Notes

Presented at the Conference on Membranes in Drinking and Industrial Water Production. Leeuwarden, The Netherlands, 10–12 September 2012. Organized by the European Desalination Society and Wetsus Centre for Sustainable Water Technology