Monochloramine: The Solution for Water Disinfection
Monochloramine: what it is
Monochloramine (NH2Cl) is a disinfectant obtained from the reaction between a chlorine source and an ammonia source, and it has been used for the treatment of drinking water since the early 20th century.
Today, monochloramine is used not only for secondary disinfection in water utility applications but also as a solution for treating cold and hot sanitary water in large buildings and infrastructures such as hospitals and other healthcare facilities, hotels, industrial plants, and cooling systems (evaporative towers). This is done to ensure adequate control of the risk of proliferation of undesirable microorganisms, some of which, like Legionella and Pseudomonas, are potentially hazardous to health.
Monochloramine: what it is
Monochloramine (NH2Cl) is a disinfectant obtained from the reaction between a chlorine source and an ammonia source, and it has been used for the treatment of drinking water since the early 20th century.
Today, monochloramine is used not only for secondary disinfection in water utility applications but also as a solution for treating cold and hot sanitary water in large buildings and infrastructures such as hospitals and other healthcare facilities, hotels, industrial plants, and cooling systems (evaporative towers). This is done to ensure adequate control of the risk of proliferation of undesirable microorganisms, some of which, like Legionella and Pseudomonas, are potentially hazardous to health.
Is monochloramine effective against Legionella?
Yes, and its efficacy is well documented, not only through hundreds of practical applications but also by numerous studies published in scientific journals.
The San Francisco water utility was the first to highlight the significant reduction in Legionella colonisation in building networks following the switch from chlorine to monochloramine for secondary disinfection in 2005.
Based on this observation, Sanipur developed SANIKILL, initially designed as a technology dedicated to the elimination of Legionella.
To date, dozens of publications report the satisfactory results obtained with the use of monochloramine: starting from 2011, several national and international groups have documented real-world applications, highlighting the efficacy and safety of this disinfection system, even in the long term. Here are some examples:
- Water Safety Plan, Monochloramine Disinfection and Extensive Environmental Sampling Effectively Control Legionella and Other Waterborne Pathogens in Nosocomial Settings: The Ten-Year Experience of an Italian Hospital. Microorganisms (2023):1794.
- Can Monochloramine Offer a Long-Term Solution for Controlling Legionella and Waterborne Pathogens in a Healthcare Facility? The Analyst (2023) 30, 56-62.
- A comprehensive evaluation of monochloramine disinfection on water quality, Legionella and other important microorganisms in a hospital. Water Res. (2021) 189:116656.
- Safety and Effectiveness of Monochloramine Treatment for Disinfecting Hospital Water Networks. Int. J. Environ. Res. Public Health (2020) 17, 6116.
- Preventing Healthcare-Associated Legionellosis: Results after 3 Years of Continuous Disinfection of Hot Water with Monochloramine and an Effective Water Safety Plan. Int. J. Environ. Res. Public Health (2018) 15, 1594-1605.
- Continuous disinfection by monochloramine on domestic hot water system of healthcare facilities for the control of Legionella contamination. A seven months experience from Italy. J. Health Science, 2015, 3, 11-17
- Evaluation of a New Monochloramine Generation System for Controlling Legionella in Building Hot Water Systems S. Infect. Contr. Hosp. Epidemiol. 35 (2014) 1356.
- Control of Legionella Contamination with Monochloramine Disinfection in a Large Urban Hospital Hot Water System. Am. J. Inf. Cont., 40 (2012) e84
- Control of Legionella contamination in a hospital water distribution system by monochloramine. Am. J. Inf. Cont., 40/3 (2012) 279-281
Is monochloramine officially recognised as a solution for the elimination of Legionella?
Yes, monochloramine is mentioned in national guidelines (Guidelines for the Prevention and Control of Legionellosis, ISS), European guidelines (European Technical Guidelines for the Prevention, Control and Investigation of Infections Caused by Legionella Species; ESGLI), and international guidelines (Legionella and the Prevention of Legionellosis, WHO) as an effective solution for the eradication of Legionella and the prevention of its proliferation. To ensure adequate disinfection coverage, all guidelines agree on recommending the use of monochloramine concentrations between 2 and 3 ppm.
What are the benefits of monochloramine compared to other disinfectants?
Monochloramine is effective against Legionella and other potentially harmful microorganisms present in water. It exerts its disinfectant action not only on free-floating bacteria in the water but also on those present in biofilm, through which it can effectively penetrate. Its action is also independent of pH.
At usage concentrations, monochloramine is a very stable molecule, allowing it to provide optimal residual disinfection even in the case of long and complex distribution networks, low water consumption, and high temperatures, such as those typical of hot sanitary water. Being a mild oxidant, it does not cause damage or corrosion to the materials of the system in which it is dosed.
When produced correctly, it does not generate disinfection by-products, thereby minimising the chemical risk associated with disinfection.
The production method is undoubtedly an essential aspect to fully benefit from all the potential advantages of monochloramine: for this reason, SANIKILL ensures the production of monochloramine in-line, directly in the water to be treated without the accumulation of unstable concentrated solutions, and with optimal yield, so as not to leave uncombined reagents and not to form undesirable by-products.
Is monochloramine a biocide?
Is monochloramine effective in the presence of biofilm?
Yes, monochloramine acts on both free-floating bacteria in the water and those that inhabit the biofilm.
Unlike sodium hypochlorite and chlorine dioxide, which, being strongly oxidising, react immediately with the organic matter of the outermost layers and reach the deeper layers at ineffective residual concentrations, monochloramine has selective reactivity. This allows it to diffuse into the biofilm, penetrating it without being consumed. In this way, it can reach the deepest part, where it exerts its biocidal action.
This was recently confirmed by an in vitro study conducted by the University of Catania, which demonstrated the efficacy against Pseudomonas biofilm of monochloramine produced according to the SANIKILL protocol.
Is it possible to purchase monochloramine-based products?
No, monochloramine cannot be marketed as a ready-to-use product because, while it is stable at low concentrations, such as those used in practice, it is unstable at high concentrations.
The use of monochloramine therefore necessarily requires the use of suitable precursors and an appropriate system capable of generating and dosing it in situ, that is, directly at the place where it is used. SANIKILL is the patented technology developed by Sanipur for the optimal production and dosing of monochloramine, produced from its precursors ENOXIN and ZEBION.
Does the method by which monochloramine is produced affect its characteristics? Which of Sanipur's products utilise monochloramine?
Yes, the method by which monochloramine is produced can significantly affect its purity and stability. For example, an uncontrolled and uncoordinated dosing of the two reagents used to produce it (commonly, a solution based on sodium hypochlorite and one containing ammonia) can lead to an imbalance in proportions, resulting in the generation of by-products (e.g., dichloramine) and the presence of uncombined ammonia, which contributes to the onset of nitrification phenomena.
Production using systems that involve the storage of monochloramine at high concentrations is also not optimal: at high concentrations (>100 ppm), monochloramine is highly unstable and undergoes autodecomposition, with a loss of active substance and the release of ammonia and other undesirable by-products.
Conversely, SANIKILL’s patented technology allows for the precise control of the combination of the two reagents, optimising reaction conditions to produce pure monochloramine. It generates monochloramine directly in the water flow to be treated, avoiding accumulation at high concentrations.
Can monochloramine damage or corrode materials, harming the pipes of the systems in which it is dosed?
No, if produced correctly and generated in pure form, monochloramine is a “steel fist in a velvet glove”: while being an effective disinfectant, it is a very mild oxidant and thus is completely compatible with all metallic (stainless steel, carbon steel) and plastic (PPr, PE, multilayer) materials typically found in water systems.
Regarding SANIKILL, practical applications and scientific studies demonstrate the absence of any undesirable effects on piping, even with prolonged use (over 10 years).
Does the use of monochloramine necessarily cause the occurrence of nitrification phenomena?
No, the use of monochloramine does not necessarily imply the occurrence of nitrification phenomena. These can occur in the presence of uncombined ammonia and, simultaneously, insufficient disinfection.
Nitrification is a process that involves the conversion of ammonia into nitrites and then into nitrates by specific bacteria.
Using a system like SANIKILL, which can produce monochloramine without leaving free ammonia and ensuring an adequate residual of monochloramine in the network, prevents nitrification phenomena from occurring. Numerous studies and practical applications demonstrate that the use of SANIKILL does not lead to any nitrification phenomena.
Can monochloramine impart unusual or unpleasant tastes and odours to the water?
No, monochloramine itself is among the chlorine-based disinfectants with the least impact on the organoleptic qualities of water, so much so that some water utilities prefer it for this reason. At the concentrations used in drinking water (never exceeding 3 ppm, as stipulated by WHO), its presence is not clearly perceptible to most people, although individual sensitivity may vary.
It is also worth noting that, especially at the beginning of the treatment of networks previously lacking adequate disinfection, temporary alterations in the taste and smell of the water may occur, attributable to the action of monochloramine on the biofilm present in the pipes.
