Catalytic Carbon for Chloramine Removal
Many water utilities across Australia are transitioning or have, to chloramine for disinfection as an alternative to chlorine. This change is in response to stricter regulations on disinfection byproducts (DBPs), which are created when chlorine reacts with organics in water. Chloramine, a combination of chlorine and ammonia, is more stable and does not create DPBs.
Removing chloramine at the point of use, however, is more difficult than removing chlorine. Standard granular activated carbon (GAC) and carbon block products have limited capacity for chloramine reduction. Products known as catalytic carbon or “surface-modified” activated carbon can provide a solution.
Catalytic carbon removes chlorine and other chemicals the same as regular carbon. You don’t need an additional filter for chlorine.
The chloramine reduction process is a catalytic operation that breaks the bond between chlorine and ammonia and converts the chlorine to harmless chloride. What happens to the ammonia is a much more complicated issue; the removal of ammonia traces can be accomplished separately with a water softener, but special conditions apply. By definition, chloramine removal means getting rid of chloramine and does not take by products like ammonia into consideration.
There are many sound reasons why for some cities it is a better disinfectant than chlorine. However, for those who have allergic reactions to it, it can be a real menace. It is also a big problem for aquarium owners. Removing chloramine is more a challenge than removing chlorine, but it can be done and life will definitely go on.
Removing chloramine from drinking water is much easier than removing it from all the water entering the home. The best plan is a filtering device with lots of carbon–the more the better. Chloramine specific cartridges are available in drinking water sizes, though standard carbon is usually very effective when it gets the water at drinking water speed of a half gallon a minute or so. Most reverse osmosis units remove chloramine easily, however the chlorine will cause damage to the RO membrane.
The challenge of chloramine and other difficult contaminants has led to the production of a modified carbon called catalytic carbon. Catalytic carbon is a specially processed filter medium designed to greatly enhance carbon’s natural ability to promote chemical changes in contaminants. Standard filter carbon reduces contaminants in two ways. It “adsorbs” chemicals by trapping and holding them, and to a smaller degree, it “chemisorbs” contaminants by changing them to something harmless. Chlorine, for example, can be “catalyzed” to harmless chloride.
Catalytic carbon retains conventional carbon’s ability to adsorb contaminants but it also possesses greatly enhanced capacity to catalyse, to promote beneficial chemical reactions. It is by catalytic action that chloramine is reduced.
In general, basic activated carbon itself has some catalytic activity due to the presence of a small number of chemical functionalities present on the corners of its graphitic basal plane. To enhance the catalytic activity of carbon, the surface is modified by a chemical process in which the electronic structure of the carbon is altered in such a manner that the resulting carbon offers enhanced catalytic capability.
As a result, the catalytic carbon produced by this method is not only rich in chemisorbtion, but also physisorbtion capacity.
Applications for Catalytic Carbon:
- Potable water – removal of chloramine prior to RO filters
- Whole House Filtration: Removal of chloramine , organics , Hydrogen Sulphide from water supplies
- Waste water treatment
- Aquariums – removal of chloramines which is lethal to fish and invertebrates.
How Catalytic Carbon works to remove Chloramines:
Chloramine removal turned out to be a much difficult than chlorine. In fact most standard activated carbon filters don’t do the job, simply because there is not enough contact time. Most drinking water is at pH 7 or above. At pH 7 chloramine forms into a monochloramine. Monochloramines are highly stable by nature making them very difficult to remove with traditional activated carbons. It was soon discovered, if you manufacture carbon with catalytic functionality, it will remove the chloramine. Here’s how: traditional carbon would do an excellent job of removing the chlorine portion, but leave a significant amount of ammonia. Catalytic enhancements to traditional carbon allowed the carbon to retain more oxygen. The oxygen acted as the needed catalyst to breakdown the ammonia.