WATER SYSTEM HYGIENE AND SAFETY
Cold water supply
NH2 Cl generator ≈150-200 gpm of water to treat Hot water return from the building
Cold water supply
Hot water return from the building
Main hot water to the building
NH2
Fig 3. Cold (left) and hot (right) water system installations.
Cl generator ≈15-20 gpm of water to treat
Hot water heater
Conclusions Legionella bacteria, which can cause pneumonic and non-pneumonic respiratory illnesses, can be eliminated by monochloramine at concentrations of 2 mg/l - 3 mg/l within a few weeks of continuous application. Monochloramine is a stable and mild oxidant, and offers the best compatibility with the materials typically used in water distribution systems, making it less corrosive to pipework systems and their components, unlike other chlorine-based disinfectants. The chemical structure of monochloramine is the key to its stability and material compatibility. Compared with other common disinfectants, it is a weaker oxidiser due to the nitrogen atom
Authors
Marchesi I et al. AJIC 2012
Kandiah S et al. AJIC 2012
Marchesi I et al.
J. Wat. Health 2013 Kandiah S et al.
Infectious disorders, 2013
Marchesi I et al. J. Wat. Health 2013
Casini B et al. ICHE 2014
Duda S et al. ICHE 2014
Coniglio MA et al. J. Health. Sci 2015
Monochloramine Monochloramine Monochloramine 2 mg/l 1-4 mg/l 2-3 mg/l Monochloramine 2-3 mg/l
Disinfection Methods
Monochloramine Monochloramine Monochloramine Monochloramine
being bound to a chlorine atom, rather than the oxygen atom, and it exhibits high penetration through biofilms. Biofilms can act as a protective barrier against disinfectant residuals, creating a challenge for traditional disinfectants. Many studies and trials have been undertaken on the use of monochloramine following a four-step validation process: 1. Verification of effectiveness using laboratory studies;
2. Anecdotal field reports of its effectiveness from individual institutions;
3. Controlled field trials in individual institutions;
4. Successful applications in multiple Concentration Result 2-3 mg/l 2-3 mg/l 2-3 mg/l 2-4 mg/l From 60% to 8%
positive sites in 1 month From 33% to 0%
positive sites in 3 weeks From 100% to 9.5%
positive in 1 month From 53% to 0.35%
in 1 year
From 100% to 9.5% in 36 months
Chlorine Dioxide 0.5-0.7 mg/l From 96% to 46% in 36 months
From 100% to 0%
positive within 1 month From 53% to an average
of 9% in 30 months (sensor faucets risk evaluated)
From 100% to 0% positive within 1 month Table 1: Literature survey on the efficacy of monochloramine for Legionella remediation. 66 Health Estate Journal June 2023
Frank Butterworth
Frank Butterworth, Technical director at Goodwater, has over 30 years’ experience in water treatment, water hygiene, water treatment plant design, project management, and compliance, across the industry. He has worked extensively both in the UK and overseas, gaining a wealth of experience as a multidisciplined chemist engineer.
Hot water heater
institutions over a prolonged period. The results of such studies indicate that monochloramine is an ideal disinfectant for use in healthcare facilities, where the safety of patients and staff is of upmost importance. Table 1 shows that positive Legionella
remediation results have been obtained via the application of monochloramine. Only recently has monochloramine been well understood and used more widely across the globe. This could explain why it took some time for monochloramine to affirm itself as a superior biocide for secondary disinfection of buildings’ water systems.
Main hot water to the building
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