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Comparison Table

We have compiled a table outlining the characteristics of the main water disinfectants and their respective evaluations.

By clicking on “References,” you can view the bibliographic information.

StabilityEffectivenessBiofilm PenetrationpH InfluenceBy-productsMaterial Compatibility
MonochloramineEXCELLENT
References		EXCELLENT
References		EXCELLENT
References		GOOD
References		EXCELLENT
References		EXCELLENT
References
Chlorine dioxideWORST
References		GOOD
References		POOR
References		EXCELLENT
References		POOR
References		WORST
References
Cu / AgGOOD
References		POOR/GOOD
References		GOOD
References		GOOD
References		NO DATAWORST
References
Hydrogen PeroxideNO DATAPOOR/GOOD
References		POOR
References		GOOD
References		NO DATAPOOR
References
Hypochlorite and Formulations / Electrolytic ChlorineWORST
References		POOR
References		WORST
References		WORST
References		WORST
References		WORST
References

Stability:

WORST

Al-Jasser (2007). Chlorine decay in drinking-water transmission and distribution systems: Pipe service age effect. Water Res. 41, 387-396
“While flowing through pipes, the chlorine concentration decreases for different reasons. Reaction with the pipe material itself and the reaction with both the biofilm and tubercles formed on the pipe wall are known as pipe wall demand, which may vary with pipe parameters.”

Effectiveness:

POOR

Lin et al. (2011). Controlling Legionella in Hospital Drinking Water: An Evidence-Based Review of Disinfection Methods. Infect Control Hosp Epidemiol. 32, 166-173
“Hyperchlorination was found to be the most unreliable and also the most expensive disinfection modality.”

Bonetta et al. (2018). Effectiveness of a neutral electrolysed oxidising water (NEOW) device in reducing Legionella pneumophila in a water distribution system: A comparison between culture, qPCR and PMA-qPCR detection methods. Chemosphere. 210, 550-556.
“The NEOW treatment resulted in a reduction of the amount of L. pneumophila positive samples (-32%)”

Biofilm Penetration:

WORST

De Beer, D., Srinivasan, R. and Stewart, P., (1994), Direct measurement of chlorine penetration into biofilms during disinfection, Applied and Environmental Microbiology, Vol. 60 No.12, p.4339- 4344
“Comparison of the cross sections and chlorine microprofiles leads to the conclusion that decreased action of chlorine against biofilms is due to limited penetration stemming from a reaction-diffusion interaction. The microprofiles show that, after exposure to 2.5 ppm of chlorine for 1 h, only the upper 100 μm of the cell clusters is penetrated by chlorine.”

Lin, Y.E, Vidic, R.D., Stout, J.E. and Yu, V.L., 1998, Legionella in water distribution systems., JAWWA, 90, 112-121.
“Because chlorine has a limited ability to penetrate biofilms, it is less effective against biofilm-associated microorganisms such as Legionella.”

pH Influence:

WORST

European Technical Guidelines for the Prevention, Control and investigation of infections caused by Legionella species (2017)
The bactericidal action of the hypocholorite is pH-sensitive and decreased rapidly at values above pH 7.

By-products:

WORST

Orsi, G. et al, (2014) Legionella control in the water system of antiquated hospital buildings by shock and continuous hyperchlorination: 5 years experience, BMC Infectious Diseases, 14, 394
“In our experience, continuous free chlorine levels between 0.5 and 1.0 mg/L (Figure 3) were effective in reducing significantly Legionella presence in the old hospital water system. Unfortunately the continuous hyperchlorination at >0.5 < 1.0 mg/L determined the non-potability of drinking water [16], and the production of disinfectant by-products such as trihalomethanes increased.”

Material Compatibility:

WORST

Lin, Y.E., Stout, J.E., & Yu, V.L., (2011)Controlling Legionella in Hospital Drinking Water: An Evidence-Based Review of Disinfection Methods, Infect Control Hosp Epidemiol 32(2):166-173
“Hyperchlorination was found to be the most unreliable and also the most expensive disinfection modality. It has met with increasing disfavor because of inadequate penetration of the agent into biofilms in piping, persistence of Legionella organisms in hyperchlorinated systems, corrosion of the water distribution system leading to pinhole leaks over time, and the introduction of carcinogens into the drinking water.”

Lin, Y.E, Vidic, R.D., Stout, J.E. and Yu, V.L., 1998, Legionella in water distribution systems., JAWWA, 90, 112-121.
“Chlorine is highly corrosive and damages pipes. Three years after chlorination at the University of Iowa hospital, the incidence of pipe leaks was 30 times the rate before chlorination.”

Colin et al. (2011) “Degradation of polyethylene pipes by water disinfectants”.Water Disinfection, Nova Science Publishers, pp.109-142
“Disinfectants such as chlorine, bleach or chlorine dioxide can induce polymer degradation through oxidative processes, and reduce lifetime at eventually unacceptable values”

Stability:

NO DATA

Effectiveness:

POOR/GOOD

Casini et al. (2017) Application of Hydrogen Peroxide as an Innovative Method of Treatment for Legionella Control in a Hospital Water Network. Pathogens. Apr 17;6(2):15
“Overall, our data suggest that the effectiveness of HP is evident in the long-term. In the early stages of treatment, some Legionella species other than L. pneumophila appear to resist treatment by disinfectant and subsequently replace L. pneumophila”

Marchesi et al. 2016 “Control of Legionella Contamination and Risk of Corrosion in Hospital Water Networks following Various Disinfection Procedures” Appl Environ Microbiol. 2016 May 2;82(10):2959-2965.
“Different selections of Legionella spp. were observed… hydrogen peroxide treatment was associated mainly with non-pneumophila species”
See table n. 2

Biofilm Penetration:

POOR

Armon, R. et al, (2000), Controlling biofilm formation by hydrogen peroxide and silver combined disinfectant, Water Science and Technology, Vol. 42 No. 1-2, p.187-192
“Biofilm prevention effectivity of chlorine (approximately 1 ppm) was considerably higher than that of the combined disinfectant.”

pH Influence:

GOOD

Environmental Protection Agency, (2001), Final Report: Evaluation of the Efficacy of a New Secondary Disinfectant Formulation Using Hydrogen Peroxide and Silver and the Formulation of Disinfection By-Products Resulting From Interactions with Conventional Disinfectants
“Inactivation performance of the combined disinfectant increased at basic pH (e.g., log activation increased by two-fold by increasing the pH from 6 to 9 using the optimized formulation).”

By-products:

NO DATA

Unable to find any information on this subject from independent sources, i.e. scientific literatur

Material Compatibility:

POOR

Marchesi et al. 2016 “Control of Legionella Contamination and Risk of Corrosion in Hospital Water Networks following Various Disinfection Procedures” Appl Environ Microbiol. 2016 May 2;82(10):2959-2965.
“The mean corrosion rate was 0.17 0.03 mm/year for the coupons exposed to hydrogen peroxide”
“The coupons exposed… to hydrogen peroxide were characterized by pitting, with pit sizes ranging from a few micrometers to several millimeters”

Stability:

GOOD

Baron et al. 2020. Control of Legionella in hospital potable water systems. Decontamination in Hospitals and Healthcare (Second Edition). Pages 71-100
“Monitoring ion concentrations and maintenance of equipment to reduce scale formation on the electrodes is necessary”
“Elevated water pH and low ion concentrations may compromise the efficacy of ionization and so these have to be addressed at the time of installation and monitored”

Effectiveness:

POOR/GOOD

June et al. 2018. Copper and Silver Biocidal Mechanisms, Resistance Strategies, and Efficacy for Legionella Control. JOURNAL AWWA. DECEMBER 2018, 110:112
“The use of copper and silver ions to control Legionella in potable water systems is a widespread practice. The scientific literature, taken as a whole, shows varied results.”
“When properly applied and maintained, onsite water treatment offers options for pathogen inactivation and health protection”
“However, recent events have raised questions about the method’s reliability, and the conditions that may account for variable efficacy are not well understood”.

Biofilm Penetration:

GOOD

Lin, Y.S., Stout, J.E., and Yu, V.L., (2002), Negative effect of high pH on biocidal efficacy of copper and silver ions in controlling Legionella pneumophila. Appl Environ Microbiol 68:2711– 2715.
“When the pH was elevated to 9 in these experiments, copper ions achieved only a 10-fold reduction in the number of Legionella organisms in 24 h, compared to a millionfold decrease at pH 7.0.”

pH Influence:

GOOD

Lin, Y.S., Stout, J.E., and Yu, V.L., (2002), Negative effect of high pH on biocidal efficacy of copper and silver ions in controlling Legionella pneumophila. Appl Environ Microbiol 68:2711– 2715.
“When the pH was elevated to 9 in these experiments, copper ions achieved only a 10-fold reduction in the number of Legionella organisms in 24 h, compared to a millionfold decrease at pH 7.0.”

By-products:

NO DATA

Material Compatibility:

WORST

Triantafyllidou et al. (2016) Copper-silver ionization at a US hospital: Interaction of treated drinking water with plumbing materials, aesthetics and other considerations. Water Res. 2016 Oct 1; 102: 1–10
“When soluble ions from a more noble metal (such as silver) are present in the drinking water flowing through a copper pipe, they can be directly deposited and plated onto the copper surface, potentially corroding the underlying copper metal due to deposition corrosion. Metallic deposition has previously been observed between common plumbing materials like copper-galvanized steel and copper-lead, and the same electrochemical theory would apply to copper-silver in potable water plumbing.”
“Visually displeasing purple/grey staining in bathroom porcelain after CSI activation was attributed to AgCl(s).”

Stability:

WORST

Department of Health, 2016, Health Technical Memorandum 04-01: Safe water in healthcare premises, Para. 15.34, page 69.
“In the case of hot water distribution systems with calorifiers/water heaters operating conventionally (that is, at 60°C), there will be a tendency for chlorine dioxide to be lost by gassing off, especially if the retention time in a vented calorifier/water heater is long.”

Zhang Z, McCann C, Stout JE, Piesczynski S, Hawks R, Vidic R, Yu VL., (2007), Safety and efficacy of chlorine dioxide for Legionella control in a hospital water system. Infect Control Hosp Epidemiol. Aug;28(8):1009-12.
“It is clear that maintaining a sufficient residual level of chlorine dioxide in the hot water system is challenging. An elevated water temperature hastens the conversion of chlorine dioxide to chlorite by the reactions with organic compounds in the water distribution system. This finding is consistent with our observation that the mean chlorite concentration in hot water was higher than that in cold water.”

Ammar et al. (2014). Chlorine dioxide bulk decay prediction in desalinated drinking water. Desalination Volume 352, Pages 45-51
Fig. 10

Effectiveness:

GOOD

Baron et al. 2020. Control of Legionella in hospital potable water systems. Decontamination in Hospitals and Healthcare (Second Edition). Pages 71-100
“Although chlorine dioxide has been shown to control Legionella, more time may be needed for efficacy in hot water. This is due to the breakdown of chlorine dioxide into its by-products, chlorite and chlorate.”

Nella stessa reference, volendo, presenti altre considerazioni sull’efficacia limitata.

Biofilm Penetration:

POOR

Jang, A., et al, (2006), Measurement of chlorine dioxide penetration in dairy process pipe biofilms during disinfection, Appl Microbiol Biotechnol. Sep;72(2):368-76.
“Chlorine dioxide may not reach bacteria deep in a biofilm as a result of multiple resistance factors, such as molecular diffusion limitations, biofilm density, reactive depletion of ClO2.”

pH Influence:

EXCELLENT

LeChevallier, M.W. and Au, K-K, (2004), Water Treatment and Pathogen Control, WHO, p.52
“Chlorine dioxide is highly soluble in water (particularly at low temperatures), and is effective over a range of pH values (pH 5–10).”

By-products:

POOR

Baron et al. 2020. Control of Legionella in hospital potable water systems. Decontamination in Hospitals and Healthcare (Second Edition). Pages 71-100
“Reactions with organic material and corrosion scale in piping causes rapid conversion of chlorine dioxide to chlorite and chlorate, these by-products may pose health risks”

Material Compatibility:

WORST

Department of Health, 2016, Health Technical Memorandum 04-01: Safe water in healthcare premises, Para. 15.35, Note 2, page 69.
“Excessive values of chlorine dioxide should be avoided subsequently since it can corrode copper and steel pipework and can also damage non-metallic pipework and component parts, particularly at higher temperatures.”

Vertova et el. (2019). Chlorine Dioxide Degradation Issues on Metal and Plastic Water Pipes Tested in Parallel in a Semi-Closed System. Int. J. Environ. Res. Public Health 2019, 16, 4582-4598
“Results show that ClO2 has a deep effect on all the materials tested (plastics and metals) and that severe damage occurs due to its strong oxidizing power in terms of surface chemical modification of metals and progressive cracking of plastics. These phenomena could in turn become an issue for the health and safety of drinking water due to progressive leakage of degraded products in the water.”

Material Compatibility:

EXCELLENT

Lytle et al. (2021) “A comprehensive evaluation of monochloramine disinfection on water quality, Legionella and other important microorganisms in a hospital”. Water Res. 2021 February 01; 189
“The addition of monochloramine had no obvious impact on metals (lead, copper and iron)”

McNeill et al. (2001). IRON PIPE corrosion IN DISTRIBUTION SYSTEMS. Journal AWWA. July, 88-100.
“Monochloramine was found to be less aggressive than free chlorine.”

By-products:

EXCELLENT

Marchesi et al. (2020). Safety and Effectiveness of Monochloramine Treatment for Disinfecting Hospital Water Networks. Int J Environ Res Public Health. 2020 Aug 22;17(17):6116
“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”

pH Influence:

GOOD

Baron et al. 2020. Control of Legionella in hospital potable water systems. Decontamination in Hospitals and Healthcare (Second Edition). Pages 71-100
“Monochloramine…has a wider pH working range than copper-silver ionization and chlorine”

Biofilm Penetration:

EXCELLENT

Lee et al. (2011). Free chlorine and monochloramine application to nitrifying biofilm: comparison of biofilm penetration, activity, and viability. Environ Sci Technol. 2011 Feb 15;45(4):1412-9
“For equivalent chlorine concentrations, monochloramine initially penetrated biofilm 170 times faster than free chlorine”
“It appears that monochloramine’s diffusion rate was higher than its reaction rate, resulting in continued penetration with time. For approximately the same equivalent chlorine concentration, monochloramine (Figure 3b) showed increased biofilm penetration compared to free chlorine (Figure 1b), supporting by direct measurement the hypothesis that monochloramine penetrates biofilm better (i.e., quicker and further) than free chlorine.”

Effectiveness:

EXCELLENT

Lytle et al. (2021) “A comprehensive evaluation of monochloramine disinfection on water quality, Legionella and other important microorganisms in a hospital”. Water Res. 2021 February 01; 189
“Legionella culture assays decreased from 68% of all sites being positive prior to monochloramine addition to 6% positive after monochloramine addition, and these trends were parallel to qPCR results. Considering all samples, NTMs by culture were significantly reduced from 61% to 14% positivity (p<0.001) after monochloramine treatment.”
“A significant decrease in HPCs was observed after monochloramine addition. Lastly, Pseudomonas aeruginosa and Vermamoeba vermiformis demonstrated large and significant decrease of qPCR signals post-chloramination”

Stability:

EXCELLENT

Monochloramine Vikesland et al. “Monochloramine decay in model and distribution system waters”. Wat. Res. Vol. 35, No. 7, pp. 1766–1776, 2001
“The half life of monochloramine at pH 7.5 is about 75 h at 35°C but exceeds 300 h at 48°C”