Online Flow Cytometry in Drinking Water Production

Assessment of the efficiency of filtration and disinfection – the example of Lausanne, Switzerland

An article by Alexandra Hauret; Christophe Mechouk; Fereidoun Khajehnouri; Archjana Chandramohan, Service de l’Eau – Ville de Lausanne

Jérémy Senouillet; Simon Künzi; Luigino Grasso, bNovate Technologies SA

Published in AQUA & GAS No. 7/8, 2021


The water supplier Service de l'eau of the city of Lausanne, Switzerland, carried out flow cytometry measurements to assess the reduction of microorganisms in the various water treatment processes used at production sites.

The results obtained with an online flow cytometer were compared with those measured in the laboratory after sampling and showed the following results:


Sand filtration does not lead to any significant sterilisation. Only the final chlorination of the water, before it is released into the supply network, significantly reduces the bacterial count. This disinfection step ensures a reduction in the number of intact cells by a factor of 100.


The measurements also showed that ultrafiltration is effective as a means of disinfection. This filtration technique holds back the bacteria like a physical barrier. Reduction factors of 1000 to 10,000 are achieved in the total number of intact cells.


The comparative tests showed that the values measured with the BactoSense automatic online flow cytometers were the same as those determined in the laboratory after taking a random sample.



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