Chlorine is a disinfectant, most commonly used to kill microbes in the water supply. If excessive amounts are used or high concentrations reside in pipes and plumbing, chlorine can impart an undesirable taste and odor in your drinking water and other beverages. It can also contribute to foodservice equipment problems such as pitting and corrosion.
Chlorine is a very common, naturally occurring chemical element manufactured from sodium chloride. It is widely used for everything from creating household bleach to manufacturing computer chips to disinfection of swimming pools. Most water utility companies add chlorine gas to raw water to kill bacteria and other harmful microorganisms to prevent waterborne diseases. While necessary for safe water, chlorine creates many problems for foodservice operations:
- Chlorine gas has a very strong, pungent smell and an unpleasant taste. It is detectable in concentrations of as low as 1 part per million (ppm).
- Chlorine is an oxidizing agent, and is corrosive on metals in plumbing and foodservice equipment.
- Chlorine can cause damage to gaskets in equipment, making them brittle.
- Chlorine reacts with natural organic compounds in the water to form potentially harmful chemical by-products such as trihalomethanes (THMs).
- Chlorine is not very effective at killing cysts, which are living organisms that can cause illness. Examples of cysts include Giardia and Cryptosporidium.
Fortunately, chlorine is not difficult to remove from water. Carbon, found in many water filters, has remarkable capacity for neutralizing chlorine. Activated carbon is a mild reducing agent and chlorine is a strong oxidizing agent, so after chlorine becomes adsorbed, it then actually reacts with the carbon. The chlorine is reduced to chloride ion (as in table salt and sea water), one atom of carbon is oxidized to carbon dioxide, and both are released to the solution (desorbed). Meanwhile, most of the spots on the activated carbon, where all this took place, become “auto-regenerated” back to their original, like new condition, ready to adsorb again. For free available chlorine (FAC), this takes only about fifteen minutes, which means that a small amount of carbon can achieve an acceptable steady-state condition if the flow rate is slow or intermittent. For “combined chlorine” (chloramines), the reaction is much slower, and more carbon or more contact time is needed to achieve equivalent reductions.