Efficiency of various treatments of disinfection against Legionella were tested on a Hot Water
Distribution System (HWDS) pilot unit. The results demonstrated clearly that a large majority
of Legionella in the networks were fixed in the biofilm at the surface of the pipe (more than
98% for each loop). Chemical treatments (continuous chlorination, hyperchlorination,
hydrogen peroxide and peracetic acid mixing) commonly used for the eradication of
Legionella in hot water distribution networks, appeared to be inadequate for eradicating the
bacteria in the biofilm. Unfortunately, the biofilm contained a large majority of the pathogens
in an HWDS whereas legislation is only restricted to the Legionella concentration in the water
phase. Thermal treatment appeared to be efficient to disinfect the majority of the biofilm but
seemed to promote the biofilm re-growth as well. It was then concluded that the best solution
to prevent Legionella contamination in a hot water distribution system would be to have
perfect control of the temperature in the networks (temperature > 55C at all points).
Nevertheless, in many cases it is difficult to have such control, so during the time necessary
to do the network modifications, the best solution to control the Legionella proliferation
appeared to be applying a treatment shock (thermal or chlorination in function of pipe
characteristics). These treatments must be followed by a continuous chlorination totally
controlled and equipped with alarm systems. This study demonstrated that biofilm sampling
devices must be installed in hot water distribution systems to anticipate Legionella
contamination and correctly determine the efficiency of the treatments. Includes 21 references, table, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 600 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 14 |
| Published : | 11/02/2003 |
