Joint Research Programme/WiCE and STOWA study use of viruses against Legionella in wastewater streams

Within the Joint Research Programme-WiCE (Water in the Circular Economy) programme, KWR and STOWA are studying the extent to which bacteriophages that are capable of infecting the Legionella pneumophila bacterium offer a therapy to control L. pneumophila in warm side streams in wastewater treatment processes. The researchers are at the same time examining the use of this ‘phage therapy’ against Campylobacter in wastewater, because more is known about the bacteriophages that infect Campylobacter.

In an Exploratory Research project of the Joint Research Programme-WiCE programme, KWR and STOWA are researching the extent to which bacteriophages that infect L.  pneumophila can be used as phage therapy to control this bacterium in warm side streams. To begin with, the researchers aim to isolate the bacteriophages capable of infecting the bacterium. Subsequently, under laboratory conditions, they will study whether the isolated bacteriophages are capable of killing L. pneumophila in pure cultures and in wastewater. Since the Legionella bacteriophages are barely described in the scientific literature, the researchers are simultaneously taking the same approach to examine whether phage therapy can be used to control Campylobacter in wastewater. Bacteriophages that infect Campylobacter are particularly well described in the literature, and are in fact already being successfully applied as phage therapy in other ecosystems.


At a time when the SARS-CoV-2 virus has the world in its grip, one might almost forget that there are also viruses that are welcome; viruses that do not infect humans, animals or plants, but actually attack pathogenic bacteria. These viruses are called bacteriophages, and the bacterial cells that they infect die. This could offer a possible alternative to antibiotics. In the past, particularly in the former Soviet Union, research was carried out into phage therapy: the use of bacteriophages to kill pathogenic bacteria. Interest in phage therapy has recently revived because infections caused by antibiotic resistant bacteria cannot always be effectively treated with antibiotics, but they might be susceptible to specific bacteriophages. But phage therapy could possibly also be used to control undesirable bacteria in aquatic environments.

Legionella outbreaks in wastewater treatment

In recent years there have been a few small outbreaks of L. pneumophila caused by warm side streams in wastewater treatment processes.  Surveys also show that this bacterium can be present in relatively high numbers in such wastewater treatment processes. Given that many of the common control measures kill all bacteria, they cannot be used, since it is the other bacteria present in wastewater streams that actually treat the wastewater. Currently, the response frequently involves covering up the treatment tanks in which large numbers of L. pneumophila have been detected, thus preventing any aerosols from getting into the air and potentially spreading the bacterium. This measure is however very costly.

Participants for supervisory group

The phage therapy research was recently launched and will run through to the end of 2021. At the moment, STOWA’s Legionella Community of Practice forms the project supervisory group, but interested persons from the drinking water utilities would also be welcome. You can contact the researcher if you would like to participate in this project.