Distilled water is dechlorinated. Distillation is a purification method where water is boiled into steam and then condensed back into a liquid state, mimicking the earth’s natural hydrologic cycle. This process consistently removes nearly all impurities, including the chlorine compounds added to municipal supplies. The resulting product is essentially pure water, free from chemical additives and contaminants found in regular tap water.
Why Chlorine Exists in Water Supplies
Municipal water systems rely on chlorination to ensure the water delivered to homes is safe for consumption. Chlorine is an efficient disinfectant added to public water to kill or inactivate disease-causing pathogens, such as bacteria, viruses, and protozoans. The introduction of this chemical has historically been one of the most significant public health advances, drastically reducing the spread of waterborne diseases.
A residual amount of chlorine is intentionally left in the water after initial treatment, known as secondary disinfection. This residual protection is necessary to maintain the water’s safety as it travels through the vast network of pipes, guarding against potential recontamination. Facilities may also use chlorine for controlling taste and odor or preventing the growth of nuisance organisms within the distribution system.
The Distillation Process and Dechlorination
The fundamental principle allowing distillation to remove chlorine is the significant difference in boiling points between water and chlorine compounds. Water boils at \(100^{\circ}\text{C}\) (\(212^{\circ}\text{F}\)), but free chlorine is a volatile gas that vaporizes at a much lower temperature. As the source water is heated, the chlorine readily converts to a gas and separates from the liquid water before the water turns to steam.
Many modern distillation units use vents or a specialized process to ensure these gaseous contaminants are safely expelled and do not recombine with the purified water. Chloramines, compounds of chlorine and ammonia used by some municipalities for a more stable disinfection residual, are also removed through this process. Although chloramines are less volatile than free chlorine, continuous boiling and vaporization ensure separation from the pure water vapor.
Many high-quality distillers include a final stage where condensed water passes through an activated carbon post-filter. This step adsorbs any trace amounts of volatile organic compounds (VOCs) or residual chlorine compounds that may have traveled with the steam. The combination of thermal separation and carbon filtration provides nearly complete removal of all volatile chemical disinfectants.
Purity Beyond Chlorine: What Else Is Removed
Distillation’s effectiveness extends beyond the removal of chlorine to encompass a wide spectrum of non-volatile contaminants. The process is efficient at separating non-volatile inorganic compounds, which have extremely high boiling points and cannot turn into steam. These substances are left behind in the boiling chamber as a concentrated residue.
A primary group of removed contaminants includes dissolved solids and minerals, such as calcium, magnesium, and sodium, which cause water hardness. Distillation also eradicates heavy metals like lead, arsenic, mercury, and barium, which pose serious health risks. Inorganic chemicals, including nitrates and fluoride, are separated by this method.
The intense heat of the boiling process provides an excellent safeguard against biological contaminants. The water is maintained at \(100^{\circ}\text{C}\) for a sustained period, sufficient to inactivate or kill all microorganisms. This includes bacteria, viruses, and protozoan cysts like Giardia and Cryptosporidium, ensuring the final product is microbiologically pure. Distillation removes approximately 99.9% of total dissolved solids, resulting in exceptionally high water quality.