Chloramine is a common disinfectant used in public water systems to ensure water safety. Unlike free chlorine, chloramine does not quickly dissipate from water. This article explains why and outlines effective removal methods.
Understanding Chloramine in Water
Chloramine is a stable chemical compound formed when chlorine is combined with ammonia during water treatment. This combination forms monochloramine, the most prevalent type used in municipal water supplies, though dichloramine and trichloramine can also exist. Water utilities favor chloramine due to its persistent disinfectant residual. Its chemical structure provides greater stability than free chlorine, allowing it to remain effective over longer distances and durations in plumbing systems.
Evaporation’s Role in Chloramine Removal
Unlike free chlorine, which readily evaporates, chloramine exhibits high chemical stability. The strong bond between chlorine and ammonia prevents it from easily volatilizing. Therefore, letting water sit out, even for extended periods, will not significantly reduce chloramine levels. This stability is why traditional aeration methods, effective for chlorine removal, are ineffective for chloramine.
Practical Methods for Removing Chloramine
Since evaporation is not an effective removal method, specific techniques are necessary to eliminate chloramine from water. Chemical neutralization is one approach, often involving reducing agents like ascorbic acid (Vitamin C) or sodium thiosulfate. Ascorbic acid, for instance, breaks down chloramine into harmless compounds such as inorganic chloride and dehydroascorbic acid. Approximately 2.5 parts of ascorbic acid are needed to neutralize 1 part of chloramine.
Activated carbon filtration is another method for chloramine removal. Granular activated carbon (GAC) and carbon block filters work through both adsorption and catalytic reduction. In catalytic reduction, the carbon surface acts as a reducing agent, facilitating a chemical reaction that breaks down the chloramine molecule. While standard activated carbon can remove some chloramine, catalytic carbon is specifically engineered for enhanced efficiency, requiring less contact time for effective removal.
Reverse osmosis (RO) systems also contribute to chloramine reduction, though the RO membrane itself does not directly remove it. These systems incorporate carbon pre-filters that effectively eliminate chloramine. The slow flow rate inherent in the reverse osmosis process allows for extended contact time between the water and the carbon filters, optimizing chloramine removal before the water reaches the RO membrane.
Why Chloramine Removal Matters
Removing chloramine from water is important for several applications. For aquatic environments, chloramine is highly toxic to fish and other aquatic invertebrates. It can damage their gills and red blood cells, hindering oxygen absorption. Even very low concentrations, such as 0.002 to 0.005 parts per million, can be detrimental to aquatic life.
In gardening and hydroponics, chloramine can negatively impact sensitive plants and beneficial soil microbes. It may cause root browning in hydroponically grown lettuce plants. It also affects microbial communities in soil, which are important for plant nutrient uptake.
Chloramine can impart a chemical taste or odor to drinking water. Beyond aesthetics, it reacts with organic matter to form disinfection byproducts (DBPs), such as N-nitrosodimethylamine (NDMA). While chloramine produces fewer DBPs than chlorine, effective filtration helps reduce exposure.