How Does Chlorine Work as a Disinfectant?
- Chlorine disinfects through a process known as disassociation. Once water is combined with chlorine a reaction occurs that creates two acids. Hypochlorous acid and hydrochlorous acid appear when chlorine is added to water. And it's hypochlorous acid that becomes the chlorine that's active in water treated with chlorine. This active chlorine kills microorganisms by destroying their cell walls, rendering their inner enzymes useless. Microorganism death quickly ensues.
- Once the active form of chlorine in water, hypochlorous acid, kills off microorganisms, it eventually becomes deactivated, or oxidized, itself. Deactivation itself occurs only after hypochlorous acid has bound with certain nitrogen or ammonia compounds. These compounds are produced when active chlorine successfully kills off microorganisms. The product left over after all the active chlorine is used up are known as chloramines. Once chloramines are present, pool chlorine levels will be greatly dissipated or even disappear.
- To be effective as a water disinfectant, a certain level of chlorine needs to be present. In swimming pools, the recommended level of free available chlorine is 2 parts per million (ppm). The recommended chlorine level range should be from 1 ppm to 3 ppm to provide a safety buffer. Free available chlorine is the actual unused chlorine ready to attack microorganisms that end up in a swimming pool's water.
- Chlorine is classified as a hazardous material and it's an extremely strong disinfectant. Chlorine's strength is also why only very small amounts of it are needed in water. For example, in drinking water it's only necessary to have 0.2 ppm of free available chlorine present. In swimming pools, a 2 ppm chlorine level is obtained by dosing a 30,000 gallon pool with about 1 pound of standard pool chlorine.
- There are three forms of chlorine; gas, liquids and solids. Gas is the least-used form of chlorine in home pools. Two other forms of chlorine, liquids and solids, are more common. The most common type of chlorine used in home pools is a solid known as calcium hypochlorite. Available in powder, tablets and sticks, calcium hypochlorite is about 65 percent chlorine. For liquid chlorine (sodium hypochlorite), strength ranges from 11 to 14 percent. In bleach, chlorine strength is about 5.25 percent.