Chloramines in Drinking Water
The EPA's webpage on chloramines begins with this paragraph:
Chloramines are disinfectants used to treat drinking water. Chloramines are most commonly formed when ammonia is added to chlorine to treat drinking water. The typical purpose of chloramines is to provide longer-lasting water treatment as the water moves through pipes to consumers. This type of disinfection is known as secondary disinfection. Chloramines have been used by water utilities for almost 90 years, and their use is closely regulated. More than one in five Americans uses drinking water treated with chloramines. Water that contains chloramines and meets EPA regulatory standards is safe to use for drinking, cooking, bathing and other household uses.
In spite of the EPA's assurances of safety, the use of chloramine in city water supplies has provoked continual controversy. And for many reasons, including simple aesthetic preference, a very high percentage of city water users want chloramines removed from the water they drink and bathe in.
Treatment for Chloramines: How to Remove Chloramines from Water
Reduction of chloramines from city water is a commonly misunderstood issue. For those unfamiliar with the details of water treatment, there is often an expectation that there is a "filter" for every contaminant that specifically identifies that contaminant and, as if by magic, "takes it out." A frequent question is "How much does your filter take out?" It isn't quite as simple as that, especially with "problem contaminants" like chloramines.
Here is an excerpt from technical writer David Bauman. This is from a Water Technology article on chloramines. By way of explanation, the "catalytic carbon" Mr. Bauman refers to is commonly known by its most popular brand name, Centaur carbon.
Removal possibilities Chloramines should not be confused with chlorine. Chloramines cannot be removed by passing water through the same activated carbon filters used for chlorine removal because these filters are too small at their designed flow rates.
Everything attributed to catalytic carbon applies to standard carbon, although to a lesser degree. All activated carbon has some catalytic capability, but standard carbons of all common basic materials have a relatively low activity for chloramine removal. For thorough removal, up to four times the contact time of catalytic carbon may be required. Substantial increases in percent removal and length of run before chloramine breakthrough can be achieved with smaller mesh carbon. Some systems have been designed that precondition the carbon by exposure to general use or to chlorine.
The practical realities one is left with from Mr. Bauman's excellent summation of removal strategies are that
1. Except in a controlled industrial setting, it is next to impossible to predict the lifespan or the exact reduction percentage of a water filter used for chloramines.
2. Such variables as water temperature, flow rate, mesh size of the medium (in the case of carbon), and other contaminants in the water greatly affect the effectiveness and the longevity of the filter.
3. The often-used blanket statement that "reverse osmosis does not remove chloramines" is technically true but realistically false. While the reverse osmosis membrane itself does not remove chloramines, every respectable RO unit is equipped with two or more high quality carbon filters. Pre-filters, the filters that process the water before the membrane, receive water at a very slow rate of flow and therefore work under excellent conditions for chloramine reduction. The use of the high quality cartridges described by Mr. Bauman actually should provide superb chloramine reduction in an undersink RO unit, yet the "reverse osmosis does not remove chloramines" myth continues to be promoted by sellers of non-RO products.
4. If you are thinking of purchasing a "whole house" chloramine filter, your choice in sizing should be made considering the life expextancy of the carbon. Mr. Bauman's figures show that the carbon's lifespan could be reduced to as little as 1/8 by undersizing.
Catalytic Carbon and Chloramine
Filter carbon is often classified according to a system of rating scales that describe its properties. One of these scales is called the "Peroxide Number," which is used to measure carbon's ability to promote catalytic reactions. The peroxide number is actually a time measurement in minutes of the time that is required by a carbon to decompose hydrogen peroxide. The lower the peroxide number, the greater the carbon's ability to decompose hydrogen peroxide and consequently to perform catalytic activities. The lower the peroxide number, the higher the catalytic activity, and, therefore, the greater the carbon's chloramine reduction effectivenss.
Here are typical peroxide numbers for various carbons:
Catalytic Bituminous Coal-Based – 10
Conventional Bituminous Coal-Based – 40
Subbituminous Coal-Based – 40
Lignite Coal-Based – 60
Wood-Based - >120
Coconut-Based - >120
Figures are from Hayden and Spotts, "Fundamentals of Catalytic Activated Carbons,"Water Technology Magazine.
References from other websites:
A look at a top notch catalytic carbon filter.
Removing ammonia from aquarium water (with a technique that can be applied to undersink reverse osmosis for drinking water as well).