Roadmap for Next-Generation Sequencing (NGS) to monitor microbial drinking water quality

Changes in water quality during drinking water production or distribution can lead to the growth of undesirable micro-organisms in the drinking water system. Mixing drinking water produced at different production locations or the distribution of drinking water from another production location can adversely affect microbiological water quality.

At present, the growth of undesirable micro-organisms in the distribution system is mainly determined on the basis of the colony count at 22°C (KG22) and the colony count for Aeromonas with culture methods on selective agar plates as required by the Dutch Drinking Water Decree. However, it is reasonable to assume that the composition of the total microbiota in the drinking water system will also change as water quality changes.

NGS methods for complete microbiota

Over the past decade, NGS methods to characterise microbiota have enjoyed increasing interest. Methods of this kind can be used to investigate microbiological drinking water quality in a much broader way than is possible with selective culture media.

In this project, we are evaluating the added value of microbiota monitoring and the opportunities and impossibilities relating to application in the drinking water sector. We are investigating the reproducibility, repeatability and detection limits of two different NGS methods that are available at KWR (Illumina and Nanopore). KWR is also comparing the two methods in order to establish a picture of the differences and similarities in the results. Where possible, drinking water laboratories are being asked to contribute to the study with their own methods so that these results can also be included in the study.

In collaboration with the drinking water laboratories, we are also looking at how the methods can be harmonised as much as possible. In this way, we will ensure that current developments do not get in the way of routine application over time, for example because NGS analyses that are being set up and conducted now by laboratories differ from each other unnecessarily.

Interviews are also taking place with the drinking water utilities and their laboratories to jointly assess how NGS methods can be used in research projects and which considerations are important in that respect. There are also discussions about which routine applications may be promising.

Roadmap for the application of NGS to monitor drinking water quality

The results of the study will be worked up into a roadmap for the application of NGS methods to monitor drinking water quality. This anticipates the application of NGS methods for routine monitoring over time and the use of NGS methods for research. It also identifies the considerations involved in applying the methods for both purposes. The roadmap focuses on the steps that have to be taken to allow NGS methods to be used more routinely in practice and further standardised. Promising applications for the uniform NGS method are being investigated. They include the biological stability of drinking water, the effect of mixing different sources and/or alternating sources on biological stability, biofilm build-up in different piping materials and/or the emergence of anomalies/calamities. A concluding workshop will be organised to present the project results and to jointly engage in dialogue about the opportunities and impossibilities relating to the routine application of NGS to monitor microbial drinking water quality.