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Development of a pilot‐scale 1 for Legionella elimination in biofilm in hot water network: heat shock treatment evaluation
Author(s) -
Farhat M.,
Trouilhé M.C.,
Briand E.,
MolettaDenat M.,
Robine E.,
Frère J.
Publication year - 2010
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/j.1365-2672.2009.04541.x
Subject(s) - legionella , biofilm , tap water , microbiology and biotechnology , legionella pneumophila , contamination , water treatment , pulp and paper industry , shock (circulatory) , environmental science , biology , environmental engineering , chemistry , bacteria , ecology , medicine , genetics , engineering
Aims: (i) To develop an analytical tool in order to evaluate the effectiveness of anti‐ Legionella treatment in biofilm and (ii) study the fate of Legionella populations in water and biofilm after applying a heat shock treatment. Methods and Results: A pilot‐scale unit simulating a hot water system was built and designed by the Scientific and Technical Building Centre (CSTB, France). At the end of the contamination period, a stable cultivable Legionella spp. concentration of 5 × 10 5 CFU l −1 was obtained. Two heat shock treatments (70°C for 30 min) were applied. The results showed that the first treatment had a transitional effect on the abatement of Legionella concentrations, while the second treatment had no detectable effect on Legionella populations in water and biofilm. The DAPI (4′,6′‐diamidino‐2‐phenylindole), Legionella PCR and GVPC (glycocolle vancomycin pyrophosphate cycloheximide) counts measured in the dead leg water of the Test Loop were 1, 2 and 2 log units higher than results found in the Test Loop water. Moreover, Legionella spp. count in tap water was about 10 4 GU l −1 . These analyses revealed that they are responsible for the rapid recolonization as well as the uncomplete destroyed biofilm. In addition, a resistance test was conducted and showed that Legionella in the second heat shock treatment was not thermo‐resistant but thermo‐acclimated. Conclusion: Thermal disinfection does not seem to be efficient enough to eliminate Legionella when it is used as a curative treatment. Significance and Impact of the Study: This work could help water managers for a better management of water network and for a better control of Legionella .