FAQ - Frequently Asked Questions about Monochloramine

The primary difference between hypochlorite and monochloramine lies in their chemical structure and the resulting differences in their disinfectant properties.

Sodium hypochlorite is commonly known as the active component in bleach. Its active form, which provides disinfectant properties, is hypochlorous acid, and its effectiveness is highly influenced by pH, decreasing drastically at pH levels above 7. Being a strong oxidant due to the instability of the Cl-O bond, it is a powerful disinfectant used for a wide range of purposes, including water disinfection (even for drinking water) and surface hygiene. However, its high reactivity can cause it to interact with substances in the water, forming unwanted and harmful by-products, such as trihalomethanes. It can also attack the materials in water and plumbing systems, leading to corrosive effects.

Monochloramine, on the other hand, is a disinfectant characterised by reduced reactivity, thanks to the stabilising effect of the Cl-N bond. It is commonly used for the disinfection of drinking and industrial water. Due to its chemical properties, monochloramine is more persistent than hypochlorite, ensuring longer disinfectant coverage, greater compatibility with water system materials, and reduced formation of unwanted by-products.

The choice between hypochlorite and monochloramine depends on the specific circumstances and disinfection needs. While both are effective disinfectants, monochloramine is preferred in certain contexts, such as secondary disinfection of drinking water, due to its greater stability and lower production of harmful by-products, or for treating “dirty” process waters rich in oxidisable material.

Yes, water treated with monochloramine is safe when used in accordance with current guidelines and regulations for drinking water. Monochloramine is an effective disinfectant used to make water safe for human consumption.

When water is treated with monochloramine, the substance reacts with microorganisms in the water, such as bacteria, viruses, and parasites, eliminating them and effectively removing the risks they pose to human health. Compared to other common disinfectants, such as sodium hypochlorite and chlorine dioxide, monochloramine minimises the formation of disinfection by-products, which are often potentially harmful to health.

International authorities have established strict guidelines to ensure that monochloramine levels in water are safe for human consumption. In particular, the World Health Organization has set a maximum concentration of 3 mg/l for monochloramine in drinking water, a level at which no adverse health effects are observed.

Using water treated with monochloramine in an aquarium requires specific pretreatment precautions, which are necessary whenever water contains chlorine-based disinfectants. While these compounds are safe for humans, they can be harmful to delicate aquatic species. Water that is safe for humans is not necessarily suitable for aquarium life, and compounds like monochloramine, sodium hypochlorite, and chlorine dioxide can be dangerous to the organisms living in the aquarium.

Before adding water treated with monochloramine to the aquarium, you should either:

• Filter the water through a dechlorination filter (typically a carbon filter) to remove the residual disinfectant. Most aquariums are equipped with these systems, but it is always recommended to check for their presence and proper operation according to the technical specifications.
• Precondition the water by adding specific neutralising agents, available at specialised stores, and follow the detailed usage instructions provided.

Only after adequately pretreating the water (and optionally verifying the pretreatment’s effectiveness with analytical tests) should the water be used in the aquarium without risking harm to its organisms.

Drinking water treated with monochloramine does not pose a risk to anyone’s health, including individuals undergoing dialysis.

However, when it comes to water used for dialysis treatment, it must be free of any disinfectant residues, including monochloramine. For this reason, dialysis systems are legally required to be equipped with water pretreatment systems to remove disinfectants, typically through appropriately sized activated carbon filtration systems that ensure complete removal of all residues.

For patients undergoing dialysis at home, it is particularly important to verify the presence and functionality of these systems. Given monochloramine’s persistence and stability, if the water utility employs it for secondary disinfection, the residual concentration in tap water may be higher than that of sodium hypochlorite or chlorine dioxide.

In general, due to the critical role water plays in the dialysis process, it is always essential to carefully follow the instructions of technical and healthcare experts to ensure that the water used during dialysis is adequately treated and safe for the patient.

Monochloramine is documented as having the least impact on the organoleptic qualities of water among chlorine-based disinfectants. Although it is not completely neutral, it is usually faint or undetectable at the concentrations used for drinking water treatment. However, odour and taste perception can be subjective and may vary from person to person.

In some cases, when starting a monochloramine disinfection process, there may be a temporary and slight change in the water’s odour and taste. This is not due to the disinfectant itself but to its effect on the biofilm in the water system. Nevertheless, this effect is entirely temporary and quickly subsides.

Monochloramine is a colourless compound, so it does not impart any colour or specific appearance to the water. The water remains perfectly clear and colourless. Its presence in water cannot be detected visually but can be confirmed using appropriate analytical methods.

Disinfecting drinking water is an essential process to protect human health from potential microbiological risks that water may carry. Water disinfection is crucial in preventing the spread of diseases caused by bacteria, viruses, and other microorganisms present in the water.

Water can become contaminated from natural or anthropogenic sources, and microbial contamination may either be present at the source or occur along the distribution network.

For this reason, two types of disinfection processes are distinguished: primary disinfection, which takes place at the drinking water treatment plant and eliminates any contamination at the water’s point of capture, and secondary disinfection, conducted immediately before the water is introduced into the distribution network to ensure protection against any contamination or bacterial growth that may occur within the pipes. Monochloramine is particularly suitable for this application due to its stability and persistence.

Yes, monochloramine is a chemical compound commonly used to disinfect drinking water, and its concentration is regulated by specific standards. Compliance with these standards ensures that water treated with monochloramine is absolutely safe for human consumption. Water utilities use monochloramine dosing to protect consumer health, as the water may contain microorganisms that are dangerous to human health. The purpose of adding a disinfectant like monochloramine is to eliminate these microorganisms and control any recontamination throughout the distribution network, up to the end users.

As with any disinfectant dosing, utilities that use monochloramine also conduct chemical and microbiological monitoring of the water to ensure all relevant parameters are within safe limits, fully protecting consumer health.