What happens during the “microbial bus journey”?

Imagine that the water drop is like a bus and the bacteria are its passengers. In our project The microbial bus journey we have investigated whether or not the same groups of bacteria remain in the bus from the water treatment plant to the last stop on the journey.

Using flow cymetry water samples are analyzed and dot plot diagrams are created. A dot in the diagram corresponds to a particle, and particles are assessed as bacteria when they land on a specific surface. With the method, we can detect culturable and non-culturable microorganisms. The diagram shows the number of intact (live) bacterial cells in a section of the bus journey during 2020-2021.

The bus runs from Ringsjöverket to Flyinge and passes large parts of Lund municipality and various types of facilities. During the journey, the water changes and is exposed to new environments and conditions, such as varying pressure, flow rate, pipe dimensions and of course the water also passes reservoirs and water towers.

What happens in the drop of water at these different “stops” and how does the bacterial flora in the water change during the journey, from when it is produced until it reaches our customers?

This project has been a cooperation between Sydvatten and VA SYD.

We challenged the way you usually design a sampling program. Instead of taking samples from all points at one and the same time, we followed one single “water package” all the way, using hydraulic modelling. In this way, we were able to track which changes actually occur during a specific section of the pipeline network and see how “water packages” change on their way to the customer, says Lena Meyer Lind at VA SYD, who run the project together with Sandy Chan from Sydvatten.

The project was carried out as one of three subprojects funded by Svenskt Vatten Utveckling: Rational microbiological analysis for distribution of stable drinking water quality.

The results are presented in a report that will be release in February 2023.

Belongs to project

The microbial bus journey