Chloramines – derivatives of ammonia by the substitution of one, two or three hydrogen atoms with chlorine atoms – are fast becoming a standard means of removing bacteria from water supplies. It is estimated that around 25% of US water treatment plants use chloramines as a water-cleaning agent, and its use is growing in the UK. Chloramine actually exists in three different forms, being monochloramine, dichloramine, and trichloramine, depending upon atomic arrangement. They are chemically related and are easily converted into each other, depending upon local conditions. Medically, chloramines have been linked to respiratory problems, and may be a factor in cancer formation.
With its potential health implications, the removal of chloramines from general water supplies is a high priority in many instances. In addition, chloramines should always be removed from water for dialysis, aquariums, hydroponic applications, and homebrewing beer. Chloramines can interfere with kidney dialysis systems, can be detrimental to aquatic animals, and can give home-brewed beer a nasty taste by forming chlorophenols. In hydroponic applications, the compound has also been shown to stunt the growth of plants. Luckily, both dichloramine and trichloramine are fairly volatile and naturally escape from water quite quickly, and the remaining monochloramines can be removed by couple of means.
Chloramine water filters are carbon based devices, however standard granular activated carbon (GAC) is fairly ineffective as a chloramine filter since its reduction rate is quite slow so throughput needs to be significantly reduced. That’s not a good situation for a heavy water user and other means are needed to ensure efficient removal. The most effective way of addressing chloramine reduction is to use catalytic carbon systems to help break down the chloramine.
Generally, the catalytic properties of carbon are measured by the rate at which carbon decomposes a common material – hydrogen peroxide. The resulting “peroxide number” which is measured in terms of minutes, estimates the carbon’s utility in any other catalytic application, and in this case, its chloramine reduction characteristics. Therefore, based on the comparative results obtained for a variety of carbon mesh sizes for commercial carbons, the efficiency of chloramine reduction is discussed in the terms of peroxide decomposition capacity and further extended to the total life (I.E. the total volume) claims for corresponding GAC cartridge and carbon block systems.
Catalytic carbon cartridges are one of the major methods of removing chloramines on an industrial scale. Supplied as replaceable units, catalytic carbon is usually such a matrix of carbon spheres which have been structurally modified to change the chloramine into nitrogen and ammonia gases – which are then harmlessly bled off – with the chlorine remaining in the water. The subsequent chlorine reduction can be carried using simple activated carbon or even a UV light source.
In terms of throughput, chloramine filtration can be carried out rapidly, with some industrial systems able to handle as much as 250 gallons per minute. This makes them suitable for heavy water users such as hospitals, schools and other educational establishments, food preparation systems and industrial processes that require copious amounts of clean water.
Chloramine is dissolved in water to ensure that it remains antibacterial in nature while travelling through the water system, however, increasing concern about noxious materials such as chlorine and ammonia placed in our water have led to an increasing interest in removing them at point of use. Using combinations of catalytic and activated carbon filters, it is becoming easier to ensure both chloramine and chlorine removal on either a commercial or domestic basis.
