Safety and Effectiveness of Monochloramine Treatment for Disinfecting Hospital Water Networks

• Main Authors: Isabella Marchesi, Stefania Paduano, Giuseppina Frezza, Luca Sircana, Elena Vecchi, Pietro Zuccarello, Gea Oliveri Conti, Margherita Ferrante, Paola Borella, Annalisa Bargellini
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: International Journal of Environmental Research and Public Health
• Subjects: monochloramine; disinfection by-products; N-nitrosamines; hospital setting; water networks; <i>Legionella</i>
• Online Access: https://www.mdpi.com/1660-4601/17/17/6116

The formation of potentially carcinogenic N-nitrosamines, associated with monochloramine, requires further research due to the growing interest in using this biocide for the secondary disinfection of water in public and private buildings. The aim of our study was to evaluate the possible formation of N-nitrosamines and other toxic disinfection by-products (DBPs) in hospital hot water networks treated with monochloramine. The effectiveness of this biocide in controlling <i>Legionella</i> spp. contamination was also verified. For this purpose, four different monochloramine-treated networks, in terms of the duration of treatment and method of biocide injection, were investigated. Untreated hot water, municipal cold water and, limited to N-nitrosamines analysis, hot water treated with chlorine dioxide were analyzed for comparison. <i>Legionella</i> spp. contamination was successfully controlled without any formation of N-nitrosamines. No nitrification or formation of the regulated DBPs, such as chlorites and trihalomethanes, occurred in monochloramine-treated water networks. However, a stable formulation of hypochlorite, its frequent replacement with a fresh product, and the routine monitoring of free ammonia are recommended to ensure a proper disinfection. Our study confirms that monochloramine may be proposed as an effective and safe strategy for the continuous disinfection of building plumbing systems, preventing vulnerable individuals from being exposed to legionellae and dangerous DBPs.