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A new method using flow cytometry
for water testing

Bacteria naturally populate most aquatic ecosystems including drinking water. Sysmex Partec realises the number of bacteria present in drinking water is an important consideration in the production process. Our analytical instruments use a new method to determine bacterial counts in drinking water ensuring early preventative action can be taken. Rapid and reliable, the method is recommended by the Swiss Federal Office of Public Health.

Using this new method, it is now possible to determine the microbiological status of drinking water rapidly. The procedure can be carried out at water companies, in distribution networks and by end consumers and mobile testing is also possible. The technique relies on the determination of total cell count (TCC) and the quantitative relationship between cells with low and high nucleic acid content in fresh water by means of flow cytometry. It is quick, reliable and cost-effective, enabling bacterial contamination in drinking water to be characterized in less than 15 minutes.

Heterotrophic plate count

Robert Koch founded modern bacterial drinking water quality control in 1883, with his description of a method for determining the cell count of microorganisms in soil, air and water. Ever since, bacterial count has served as a parameter for monitoring water quality and as a measure for checking the efficacy of drinking water purification. Alongside more recent, more specific methods, the heterotrophic plate count (HPC) is still determined today in almost exactly the same way and, in accordance with the established standard, is limited to 300 colonies per millilitre.

It is now known however, that the actual bacteriological status of drinking water is not really comparable with bacterial growth on an artificial culture medium. The total number of bacteria present, as determined using flow cytometry, is typically up to 10,000 times higher than the figure determined using aerobic colony counts. This is due to the fact that only a fraction (typically less than 1%) of the microorganisms in drinking water can be detected by HPC. The Flow Cytometry Total Cell Count (FMC-TCC) has gained interest because this method is an easy, rapid, quantitive and accurate method to detect both cultivable and non-cultivable microorganisms.

New Total Cell Count Technique

The technique involves marking individual bacterial cells with a fluorescent marker and using fluorescent detection to count and characterize them in a laser beam. A particular feature of the technique is its ability to count large numbers of bacteria in just a few seconds, and dispenses entirely with the need for time-consuming bacterial cultivation on ager in petri dishes. Using the ultra-compact, portable and highly cost-efficient CyFlow® Cube 6 flow cytometer from Sysmex Partec, it is possible to process more than 50 separate water samples per hour.

Based on "True Volumetric Absolute Counting" (TVAC) technology, the CyFlow® Cube 6 delivers bacterial total cell counts and cell counts of living, damaged and dead cells as recommended by the Swiss Institute of Aquatic Science and Technology (Eawag, Switzerland). TVAC delivers results by determining the analysed sample volume and a direct calculation of cell concentration. Such analysis is highly valuable for the surveillance of the water purification process in drinking water production plants as well as within the distribution network. A good example is the monitoring of a disinfection step (e.g. chlorine treatment). Here a problem would be immediately detected when there is an increase in the cell count of viable microorganisms.


  • Detection of Bacterial cells
  • Absolute counting of bacterial cells
  • Monitoring the viability of bacterial cells

Organisations that benefit from using Sysmex Partec Products

  • Water companies
  • Water treatment plants
  • Water and sewerage companies
  • Bottled water companies


"Der mikroskopische Fingerabdruck des Wassers" - Interview mit dem Amt für  Verbraucherschutz und Veterinärwesen in St.Gallen

Analysis of microorganisms

Find out more about how flow cytometry is used for the analysis of microorganism

Download White Paper

EAWAG - Featured Research

Flow cytometry: the new analytical method for the quantification of microbial cells in water.

Read Here

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