Survival and growth of water lice in (2018-2020 follow-up)

This research investigated whether water lice can survive and grow on biofilms. This information makes it possible to establish preventive measures to control the spread of water lice. It could also allow for the possible reduction in the numbers of Aeromonas in the water distribution network.

Water lice and Aeromonas in drinking water

Previous research showed that water lice play an important role in the increase of Aeromonas in drinking water. A problem arises when the standard of 1000 colony-forming units (CFUs, a measure of the number of microorganisms capable of multiplying) is exceeded. This was the reason for the launch of two research projects within the Joint Research Programme of KWR and the water utilities in 2018 and 2019. The projects collected results of survival experiments with water lice on drinking water sediment and on water concentrates with high-molecular organic carbon.

In combination with the results of the previous research, the present project identified the most important food sources of water lice in drinking water networks. This provides the basis for possible preventive measures to limit the spread of water lice and therefore also of Aeromonas.

Survival of water lice

This research investigated the survival of water lice on polyethylene (PE material) and on other relevant materials within the drinking water distribution network. The first experiment involved a shortened materials test to determine the amount of biofilm formation. An ATP test was used to establish the amount of actively growing microorganisms. During a biofilm culture, we allowed biofilms to grow in a controlled manner on a large number of PE fragments. The chemical composition of the biofilms was then determined. In the growth and survival experiment with water lice, the study focused on the degree to which this species can survive on biofilms formed from two types of drinking water.

Preventive measures

This research provides a clearer picture of the most important food sources for water lice in the distribution network. This knowledge contributes to the development of preventive measures aimed at controlling the numbers of water lice. It is expected that the measures will also limit the spread of Aeromonas and that the incidence of standard exceedances will decrease.

Water lice (Asellus) on a maple leaf.