Chloramine is a common disinfectant used by many municipalities to treat tap water, ensuring its safety for consumption by eliminating harmful bacteria and viruses. This chemical compound is formed when ammonia is added to chlorine during the water treatment process. While widely used for its effectiveness, there is often confusion regarding how chloramine behaves in water, particularly concerning its evaporation. This article aims to clarify the distinct properties of chloramine in tap water and provide practical information on effective methods for its removal.
Chloramine Versus Chlorine
The widespread misunderstanding about chloramine’s evaporation stems from its chemical distinction from chlorine. Chlorine (Cl2) is a highly volatile gas that readily off-gasses from water when exposed to air, which is why leaving tap water out can reduce its chlorine content. In contrast, chloramine, typically monochloramine (NH2Cl), is a more stable compound created by bonding chlorine with ammonia. This chemical bond makes chloramine significantly less volatile than free chlorine.
Water utilities often choose chloramine because its stability allows it to provide longer-lasting disinfection as water travels through extensive pipe networks to consumers’ homes. While chlorine dissipates quickly, especially when exposed to sunlight or organic matter, chloramine maintains its disinfectant properties for a prolonged period. This difference in chemical structure and stability is the fundamental reason why chloramine does not behave like chlorine when it comes to evaporation.
The Reality of Chloramine Evaporation
Contrary to common belief, chloramine does not significantly evaporate from tap water over short or even extended periods, unlike chlorine. The chemical bond between chlorine and ammonia in chloramine is stable, meaning it does not readily break down and off-gas into the air. A minimal amount might degrade over days or weeks due to UV light or oxygenation, but this is not a practical removal method.
Boiling water, for instance, is effective at removing chlorine, but it is largely ineffective for chloramine. Even after extended boiling, only about half of the chloramine might be removed, compared to rapid removal for chlorine. Therefore, simply letting tap water sit out or boiling it will not substantially reduce chloramine levels for most applications.
Why Removing Chloramine Matters
Despite being safe for drinking water at regulated levels, the persistence of chloramine in tap water necessitates its removal for specific uses. For instance, in aquariums, chloramine is toxic to fish and other aquatic life because they absorb it directly into their bloodstream through their gills. It can damage gills, cause respiratory problems, and even lead to death, while also killing beneficial nitrifying bacteria essential for a healthy aquarium environment.
In hydroponics and gardening, chloramine can be detrimental to sensitive plants and the beneficial microbes in the soil or growing medium. Even low concentrations can cause root browning and inhibit plant growth. The chemical can also interact negatively with nutrients, making them less available to plants.
Homebrewing is another area where chloramine removal is important, as it can react with organic compounds in the brewing process to produce undesirable off-flavors, often described as medicinal or plastic-like. Furthermore, while generally safe for human consumption, some individuals find that chloramine imparts a distinct chemical or “pool-like” taste and odor to drinking water, making it less palatable.
Effective Methods for Chloramine Removal
Since evaporation is not a practical solution, several effective methods exist for removing chloramine from tap water. Activated carbon filters are widely used, as they can remove chloramine through a process called catalytic reduction, where the carbon surface chemically breaks down the chloramine molecule. For effective removal, it is often recommended to use catalytic carbon, which has enhanced properties to facilitate this breakdown, rather than standard activated carbon alone, which requires longer contact times.
Chemical dechlorinators offer another immediate solution, particularly useful for smaller volumes of water like those for aquariums. Compounds such as sodium thiosulfate react with the chlorine portion of chloramine, neutralizing it. However, some simple dechlorinators may leave behind ammonia, which can still be toxic to aquatic life, so products designed to also address ammonia are often preferred. Ascorbic acid (Vitamin C) is also effective, chemically reducing chloramine into harmless compounds.
Reverse osmosis (RO) systems can also reduce chloramine levels, although the primary removal typically occurs through activated carbon pre-filters within the RO unit. While RO membranes can filter out many impurities, chloramine molecules are small enough to pass through some membranes, making the carbon pre-filtration a crucial component for chloramine removal in these systems.