Safety and Effectiveness of Monochloramine Treatment for Disinfecting Hospital Water Networks

Abstract

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 Legionella 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. Legionella 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.

Environmental Management of Legionella in Domestic Water Systems: Consolidated and Innovative Approaches for Disinfection Methods and Risk Assessment

“…However, monochloramine has shown to be more effective on copper biofilms while free chlorine is more effective on polyvinyl chloride drinking water biofilms [ 64 ]. Finally, the lower reactivity of monochloramine can also be an advantage, as it is less likely to react with natural organic matter in the water, forming fewer DBPs, and leading to fewer undesirable tastes and odors than chlorine or chlorine dioxide [ 65 ].…”

Legionella and Biofilms—Integrated Surveillance to Bridge Science and Real-Field Demands

“…These are all critical aspects related to Legionella persistence in man-made systems that contribute to a higher or lower legionellosis risk. The studies considered in Table 1 cover different water settings, including cooling towers [55][56][57], premise plumbing from hospitals [51,52,54,[58][59][60][61][62][63][64] and hotels [45,48,[64][65][66][67][68][69], residential potable water systems [46,70,71], and other facilities [72][73][74][75][76][77][78].…”

“…Chemical Disinfection Programs shape bacterial communities and reduce Legionella positivities (chlorination, chloramine, chlorine dioxide, copper-silver ionization, hydrogen peroxide and silver salts, NEOW) [51,52,54,56,61,62,66,72,73,[79][80][81] Effective temperature control reduces Legionella incidence [60,70,82] Water stagnation vs. water flushing [48,59,65,71,78,83]…”

Disinfection of Wastewater by UV-Based Treatment for Reuse in a Circular Economy Perspective. Where Are We at?

“…Amid the several classes of DBPs reported in the literature, trihalomethanes (THM) and haloacetic acids, are among the most studied ones [ 25 , 26 ]. The DBPs generated following the use of some chemical oxidants can also be more toxic and dangerous than the starting disinfectant compounds [ 24 , 27 ] having a potential carcinogenicity and other adverse effects on human and animal health also at low concentration [ 28 , 29 ]. For instance, haloacetic acids are considered cytotoxic and genotoxic [ 30 ].…”

“…As regards ozone, among the main disadvantages are the high costs, including energy costs and the operative and management difficulties related to its instability [ 33 ]. Ozonation also leads to the formation of bromate as DBP in waters containing the bromide ion (Br − ) [ 29 , 34 ]. Bromate appears to be a possible human carcinogen and is not biodegradable [ 35 ].…”