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
Introduction
This study evaluated four disinfection methods for their efficacy in controlling Legionella and their corrosive effects on water pipes. The four methods included:
- Heat
- Chlorine dioxide
- Monochloramine
- Hydrogen peroxide
Results
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):
- Monochloramine: 9.5%
- Chlorine dioxide: 29.8%
- Hydrogen peroxide: 38.5%
- Heat: 54.5%
Corrosion
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.
Conclusion
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.
