Peer-Reviewed Research Study

Control of Legionella Contamination and Risk of Corrosion in Hospital Water Networks Following Various Disinfection Procedures

Isabella Marchesi, Greta Ferranti, Antonella Mansi, Anna M. Marcelloni, Anna R. Proietto, Navneet Saini, Paola Borella, Annalisa Bargellini
American Society for Microbiology, Applied and Environmental Biology,  May 2016

This study evaluated four disinfection methods for their efficacy in controlling Legionella and their corrosive effects on water pipes. The four disinfection methods included:

  • Heat
  • Chlorine dioxide
  • Monochloramine
  • Hydrogen peroxide

Legionella control
Of the four disinfection methods analyzed, monochloramine had the lowest Legionella positivity rate (percentage of test sites positive for Legionella), followed by chlorine dioxide, hydrogen peroxide, and heat. None of the methods eliminated Legionella.

The results from the lowest Legionella positivity rate (most effective) to the highest (least effective):

  1. Monochloramine: 9.5%
  2. Chlorine dioxide: 29.8%
  3. Hydrogen peroxide: 38.5%
  4. Heat: 54.5%

Hydrogen peroxide and chlorine dioxide caused pitting on the pipe’s interior surface. Pitting is a type of corrosion that can lead to holes.

Monochloramine and heat appeared to be less aggressive, with monochloramine exhibiting uniform corrosion with the rare formation of pitting. Heat showed corrosion similar to that observed on the untreated samples.

Continuous chemical disinfection is effective to an extent and is significantly more effective than using only heat, and each modality displayed different morphologies of corrosion.  

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Highlighted author

Dr. Isabella Marchesi

Dr. Isabella Marchesi is a professor at the Department of Public Health Sciences at the University of Modena and Reggio Emilia, Modena, Italy. In the field of Legionella, her interest is focused on the prevention and control of environmental contamination. Her current research focuses on developing and implementing water safety plans in healthcare facilities and evaluating innovative disinfection methods for effectiveness against Legionella contamination, formation of toxic by-products, and corrosive action in the water networks. She is the author and co-author of 42 original papers and 81 abstracts presented at national and international conferences and manages the Italian website entirely devoted to Legionella.

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