Microbiology laboratory

Analytical methods for microbial water quality

The Laboratory for Microbiology at KWR (NEN-EN-ISO/IEC 17025 and NEN-EN-ISO/IEC 17043 accredited, registration numbers L479 and R005, respectively) conducts research on the biological water quality of surface water, drinking water and wastewater streams. Besides the legally required microbial analyses of (drinking) water, we carry out a wide range of supplementary (specialty) analyses from source to tap-point. We also investigate the materials that come into contact with the water.

The Laboratory for Microbiology has the following core activities:

  • Specialty analyses – including rapid molecular detection methods, cell culture methods and analyses in the area of biological stability and safety
  • R&D – development of new, innovative testing methods
  • Emergencies – urgent analyses of water quality and biological safety
  • Proficiency testing – an important tool for the standardisation and quality assurance of analytical methods

Specialty analyses

The experts in the microbiological laboratory work closely with the researchers and have considerable experience in assessing biological water quality. We determine whether our (drinking) water complies with the microbial safety requirements. The biological stability of the (drinking) water is another of our core activities.

Microbial contamination can cause health hazards, water-quality deterioration and technical problems. We determine the causes of contamination and strive for a biologically stable drinking water system. In this effort, we work continually on the improvement of existing methods.

Biofilm formation plays an important role in microbial regrowth in the drinking water distribution network. We have considerable experience in determining biofilm formation potential, speed and stability. Biofilms can also be implicated in the spread of pathogens or in clogging caused by biofouling. With regard to the spread of pathogens, we have worked on mapping the presence of water lice (Asellus) and Aeromonas. A key role is also played by the Continuous Biofilm Monitor (CBM) in the early detection of potential problems, including those associated with clogging.

Thanks to the KWR-validated and -standardised biomass production potential (BPP) test, the growth potential of our drinking water can be determined more precisely than with the traditional assimilable organic carbon (AOC) method. The test allows us, for instance, to examine biofilm formation on newly employed materials such as polyethylene (PE) connecting pipes.

In addition, we also investigate the parasitological water quality, focusing on the presence of Giardia and Cryptosporidium.

Besides analysing water quality, we also carry out effect-based water-quality measurements using bioassays to determine chemical water quality. We examine whether there are any substances present in the water that could have an impact on health. In this effort, we work closely with KWR’s Laboratory of Materials Research and Chemical Analysis.

We also have validated detection methods for specific questions, for example concerning the presence of opportunistic pathogens like Legionella pneumophila, Pseudomonas aeruginosa and Aspergillus fumigatus. We dispose of techniques, such as the Hemoflow method, that allow us to concentrate large volumes of water for detection purposes.

New challenges are moreover arising as a result of urbanisation, climate change and the energy transition, which must make the Netherlands climate-neutral by 2050. The installation of heating networks presents extra challenges in keeping the drinking water temperature under the legal limit of 25°C. This has direct implications for microbial safety, which we also identify.


Clients can also come to us with questions about non-standard analyses. Apart from our specialty analyses, we also develop new (molecular) analytical methods. One example is the RT-PCR method, with which the presence of E. coli, a key species in faecal contamination, can be determined within a few hours with great sensitivity and specificity. This technique is currently being validated for clean water.

When the composition of the microbial population is unknown, we apply modern, next-generation sequencing (NGS) techniques to elucidate them. This enables us to identify the key species, including species that are not identified by culture methods. Besides their use for drinking water, these DNA fingerprinting techniques can also clarify questions concerning the quality of surface water and the functioning of wastewater treatment plants (WWTPs).

Examples of recent research

Test laboratory for the World Health Organization (WHO)

Not all countries have centralised treatment and distribution of safe drinking water. As a WHO Collaborating Centre, we function as a test laboratory for Household Water Treatment Systems. The knowledge produced can be used to advise governments in countries where drinking water is of lesser quality, about which products are suitable for local water treatment and water quality improvement.

Proficiency testing

The microbiological laboratory has for 30 years organised proficiency testing for the coordination of measurement methods among different laboratories. We can also organise specific proficiency tests, upon request. Moreover, we carry out the data processing and reporting, both nationally and internationally.

Action during crises

Work activities on the network and emergencies can have an impact on (drinking) water quality.

Whenever the drinking water is exposed to possible danger as a result of an emergency, our experts are immediately ready to respond and the microbiological laboratory can conduct rapid analyses. The laboratory is part of the national crisis organisation, which includes the Crisis Expert Team Environment and Drinking Water (CET-md). In these networks we contribute our knowledge about water quality, water technology and health hazards. We manage analytical methods for chemical and microbial contamination, and ensure rapid data processing.

The lab brochure

An overview of the background, conduct and performance characteristics of the different analyses can be found in the Laboratory Analyses of the Microbiology Laboratory Brochure.