Sub-project 2: Effects of cleaning and disinfection procedures on the survival of pathogens in biofilms and their discharge into drinking water under close-to-practice conditions


Research partners:Biofilm Centre, Universität Duisburg-Essen (Koordination)
Institut für Hygiene und Öffentliche Gesundheit der Universität Bonn
IWW Zentrum Wasser, Mülheim/Ruhr
Fachgebiet Umweltmikrobiologie, TU Berlin

Funding:BMBF, DVGW und 15 Industriepartner
Duration:01.09.2010 - 28.02.2014

Project management / project work:

Dr. Bernd Bendinger / Dipl.-Biol. Thomas Meier


Pseudomonas aeruginosa (P. a.) and Legionella pneumophila (L. p.) are able to contaminate and persist in drinking water biofilms. It has been observed that after incorporation into biofilms P. a. can switch into a viable but nonculturable (VBNC) state i.e. it is no longer detectable with cultivation methods. In this state individual cells can possibly survive a disinfection with chlorine dioxide and can afterwards switch back into a culturable state. It is to clarify under which operating conditions and with which disinfectants this phenomenon occurs and hopefully also which measures can prevent this. Unlike P. a., L. p. remains in biofilms predominantly in a culturable state for a long time but single cells are also able to survive a disinfection and multiply again.


Long term experiments are performed in two close-to-practice test rigs simulating a household drinking water installation under varying operational conditions (temperature, pipe materials, DOC, nutrient supply). After autochthonous drinking water biofilms have been contaminated with P. a. and L. p. a cleaning procedure and prevalent disinfection procedures are performed. Biofilm and drinking water samples will be analyzed with standard and molecular methods (FISH, qPCR) after contamination and disinfection, in order to quantify the bacteria in their culturable and/or their nonculturable VBNC state. The goal is to define cleaning and disinfection measures for drinking water installations that can ensure an enduring hygienic safety because the cells in the VBNC state will also be inactivated. Thereby the unrecognized distribution of pathogens inside drinking water installations can be prevented and the risk of infection for the consumer can be minimized.


see project homepage

Executive Summary