Drinking water odor and flavor have improved
by the application of chloramines from the beginning of the twenty-first century.
Eventually chloramines were also used for disinfection.
What are the properties of chloramines?
Chloramines are formed
during a reaction between chlorine (Cl2) and ammonia (NH3).
Chloramines are amines which contain at least one chlorine atom, which is
directly bond to nitrogen atoms (N).
Inorganic chloramines are formed when dissolved chlorine and ammonia react.
During this reaction three different inorganic chloramines are formed;
monochloramine (NH2Cl), dichloramine (NHCl2) en
free chlorine and organic chloramines are chemically related and can change
into one another easily. These compounds cannot be found in isolated form.
Inorganic chloramines are not persistent; however, these compounds are more
persistent than freely available chlorine compounds. Research has shown that
the half-lives of inorganic chloramines can vary from one minute to 23 days,
depending on the circumstances.
How are chloramines produced?
frequently produced by adding ammonia to water containing free chlorine (HOCl
or OCl, depending on the pH). The ideal pH value for this reaction is 8.4. This
means the water is slightly alkaline.
NH3 (aq) + HOCI NH2Cl + H2O
When the reaction
takes place three kinds of inorganic chloramines can be formed. The pH value
determines which kind of chloramines is formed. Trichloramines mainly form
when the pH value is 3 or below. When the pH value is 7 or above,
dichloramine concentrations are highest.
The amounts of chlorine and ammonia in the water also influence the
origination of chloramines. The chlorine/ ammonia rate is ideally 6:1. During
chloramine production the rate is usually 3-5:1. When ammonia concentrations
are higher, more di- and trichloramines are formed.
Organic chloramines can also be formed during these reactions. Organic
chloramines cannot be distinguished from other chloramines, using standard
chloramine analysis methods.
Figure 1: pH values determine which kind of chloramine is formed
1: various types of chloramines and their properties
4 - 7
1 - 3
What are the applications of chloramines?
Chloramines can be
used as bleach, disinfectants and oxidators. Organic disinfectants slowly
give off chlorine, causing a slower and less aggressive disinfection than
with hypochlorite (OCl-). Chloramines can be used to improve odor
and flavor of the water when chlorine is used as a disinfectant. Chloramines
are also used for the disinfection of drinking water and wastewater and to resist biofouling in cooling water systems.
Water disinfection with chloramines
When chloramines are
used as a disinfectant, ammonia is added to chlorine treated water. Ammonia is
added after chlorine, because this causes CT values to be lower than when
ammonia is added primarily.
Chloramines are as
effective as chlorine for the deactivation of bacteria and other
microorganisms, however the reaction mechanism is slower. Chloramines, like
chlorine, are oxidators. Chloramines can kill bacteria by penetration of the
cell wall and blockage of the metabolism. Monochloramine is the most effective disinfectant. It
reacts directly with amino acids in the bacterial DNA. During deactivation of
microorganisms chloramines destroy the shell which protects a virus. When the
pH value is 7 or higher, monochloramine is the most abundant chloramine. The
pH value does not interfere with the effectiveness of chloramines.
Is drinking water disinfected using
applied more and more often in the United States as an alternative for
chlorine during secondary disinfection of drinking water. In the year 2002,
20% of the US drinking water production companies used chloramines. The main
reason for the transfer from chlorine to chloramines is that chloramines
react with organic matter less often than chlorine. Little to no trihalomethanes (THM) and
other disinfection byproducts are formed during chlormaine disinfection.
Chloramines will remain actively within the
plumbing much longer. This is because it takes long for chloramines to be
broken down. Chloramines do not give
off any taste or smell and are relatively safe.
Can chloramines be removed from water?
active in the water system for a considerably long period of time. Like other
molecules, chloramines contribute to the total amount of dissolved solids in
the water. Like chlorine, chloramines are selectively reactive and may have
damaging affects when they remain in the water for too long.
When chloramines are
present, there are usually trace amounts of ammonia and hypochlorite in the
water as well. Chloramines are hardly ionic. As a result and because of the
low molecular weight, chloramines, mainly monochloramine, are difficult to
remove from water by reverse
osmosis (RO) or water softening. Boiling and distillation cannot
be used either. Substances for chlorine removal cannot be used for the removal of chloramines. Sunlight and
aeration may aid chloramine removal.
Chloramines can be removed by
means of a granular active carbon filter. This filter brings down chloramine
concentrations from 1-2 ppm to less than 0,1 ppm. One must make sure that the
active carbon comes in contact with chloramines for a significant amount of
time. An active carbon filter is a selective, which means it also removes
other compounds, such as chlorine (reduction to chloride), hydrogen sulphide,
organic compounds, THM, pesticides and radon. When these compounds are
present in water, this will influence the capacity of the filter.
The amount of
chloramines in the water can be determined by measuring the 'total chlorine'
residu. This means measuring the 'total amount of chlorine' or the 'amount of
What benefits and drawbacks are there to using
What are the benefits?
Few disinfection byproducts
Using chloramines benefits over using chlorine, because few organic compounds
(trihalomethanes; THM) and other possibly carcinogenic byproducts (halogenic
acetic acid; HAA) are formed.
active for a long time
Chloramines remain in the water longer than chlorine. Monochloramines are
most effective when the pH value is 7 or higher. When the pH value exceeds 7
the water is alkaline. The benefit of alkaline water is that it is less
corrosive than acid water. When the pH value is high chlorine can be found in
the water as hypochlorite ions (OCl-). These ions have a higher
oxidation potential than underchloric acid. However, as a disinfectant it is
a hundred times less effective than underchloric acid. When pH values are too
high, its affectivity will diminish.
taste and smell of the water
Chloramines do not alter the pH of the water. Chloramines provide a better
taste and smell than chlorine. Chloramines are often applied to prevent a
chlorine taste or smell.
Chloramine disinfection can be improved by
What are the
When large amounts of organic matter are present in the water, organic nitrogen causes the
formation of organic chloramines. These do not possess the same disinfection
properties as inorganic chloramines. This situation occurs when organic
matter contents exceed the 3 ppm boundary.
What is the reaction rate of chloramines?
The drawback of chloramines is that they are less reactive than chlorine.
Part of the disinfectant remains in the water, where it will be consumed by
bacteria or broken down. This process can take weeks. Contrary to chlorine,
chloramines do not perish when the water lies still for a few days. As a result
chloramines need to be removed from water. Chloramines can be removed by
using granular active carbon or acetic acid.
What is the effectivity of chloramines?
In Massachusetts, research has been carried out to bring to light the death
causes of people that used water disinfected by chlorine or chloramines. The
results show that the number of people dying from bladder cancer was higher
when the water was chlorinated. When water was disinfected by chloramines,
people were more likely to die from pneumonia or flues. This may show that
chloramines are less effective than chlorine for the elimination of
Do chloramines form nitrates?
High amounts of ammonia serve as nutrients for nitrifying bacteria in the
water, which can cause nitrate levels in the water to rise. Nitrate is
converted to nitrite in the stomach. Nitrites can react to N-nitrosamines
with proteins in fish. These compounds may be carcinogenic. Young children
are more susceptive to nitrites. When children are below 0,5 years old they
cannot drink nitrate-rich water, because nitrites cause the oxygen level in
the blood to fall (Blue Baby Syndrome). It is advised to feed baby’s with
water that has a nitrate content of below 25 μg/L.
Can ammonia cause
When chloramines are chemically removed, ammonia may be released. The toxic
effect that ammonia has on fish can be prevented by the application of
biological filters, natural zeolites and pH-control.
Ammonia causes corrosion of lead
and copper. Nowadays most waterworks are made of lead or copper. In
Washington DC (US), increased lead concentrations in
drinking water caused by chloramine disinfection caused a fuss in 2003.
However, drinking water companies do not plan to switch back to using
chlorine, because this can no longer comply with the standard for
disinfection byproducts, which was lowered to 80 μg/L by the EPA.
Chloramines are used because of a lower concentration of disinfection byproducts.
To prevent corrosion, orthophosphates are added.
What are the health effects of chloramines?
Water that is
disinfected by chloramines does not cause a health threat. It can be used for
drinking, bathing and washing and is suitable for several daily domestic
What are the dangers to kidney dialysis patients, fishes and amphibians?
Drinking chloramine-containing water or using it for boiling and bathing is
safe, because of a neutralization of chloramines in the metabolism. However,
people with weakened immune systems, such as young children, elderly people,
people with HIV and people that undergo chemo therapy, should also be
cautious when it comes to the use of chloramine disinfected water.
Kidney dialysis patients and people that own fish, reptiles or amphibians
should be careful. With kidney dialysis patients the blood comes in contact
with water in a semi permeable membrane. This can cause chloramines to
directly enter the blood vessels. Chloramines are toxic to the blood.
Fishes can directly take up chloramines in the blood through their gills.
Chloramines are toxic to fishes, too. Water that is used in aquaria should be
free from chloramines.
What is the legislation for chloramine
According to American
guidelines by EPA, drinking water that is treated with chloramines can
contain a maximum amount of 4 mg/L Cl2. (National Primary
Drinking Water Regulations EPA, 2002)