AWWA WQTC58911

Efficiency of various treatments of disinfection against Legionella were tested on a Hot WaterDistribution System (HWDS) pilot unit. The results demonstrated clearly that a large majorityof Legionella in the networks were fixed in the biofilm at the surface of the pipe (more than98% for each loop). Chemical treatments (continuous chlorination, hyperchlorination,hydrogen peroxide and peracetic acid mixing) commonly used for the eradication ofLegionella in hot water distribution networks, appeared to be inadequate for eradicating thebacteria in the biofilm. Unfortunately, the biofilm contained a large majority of the pathogensin an HWDS whereas legislation is only restricted to the Legionella concentration in the waterphase. Thermal treatment appeared to be efficient to disinfect the majority of the biofilm butseemed to promote the biofilm re-growth as well. It was then concluded that the best solutionto 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 necessaryto do the network modifications, the best solution to control the Legionella proliferationappeared to be applying a treatment shock (thermal or chlorination in function of pipecharacteristics). These treatments must be followed by a continuous chlorination totallycontrolled and equipped with alarm systems. This study demonstrated that biofilm samplingdevices must be installed in hot water distribution systems to anticipate Legionellacontamination and correctly determine the efficiency of the treatments. Includes 21 references, table, figures.

Product Details

Edition:

Vol. - No.

Published:

11/02/2003

Number of Pages:

14

File Size:

1 file , 600 KB