Chlorine water treatment is a method for eliminating infectious organisms from water by introducing chlorine to render them inert. The idea of chlorinating, as it is known, was introduced in the 19th century by physician John Snow when he attacked an infamous cholera outbreak that centered around a community pump in London. By removing the handle of the Broad Street Pump, preventing people from accessing the contaminated water, he halted the outbreak and was able to show that the disease spread by water. Snow experimented with adding chlorine to a water source to decontaminate it, ushering in a major breakthrough in public health.
In chlorine water treatment, there are two different approaches. Shock chlorination is used when a water source has a high number of bacteria due to a contamination incident like a release of raw sewage. The water is treated with high concentration of chlorine to stop the spread of the bacteria and make the water safe to drink. Continuous chlorination involves passing chlorine through a water source at low levels, as it moves through a water supply system to keep it clean.
While chlorine can be hazardous, it dissipates from the water, allowing people and animals to drink it safely. It can cause a distinctive odor and color that some people do not like, although water filters are available for consumers who want to filter out some of the unpleasant taste to make their water more enjoyable to drink. Handling of chlorine for water treatment requires some care, as it is possible for workers to be injured.
Chlorinated water sources are believed to be, overall, much safer than sources not treated with chlorine, and it is the water treatment method of choice worldwide. Water is also regularly tested to make sure the chlorine is working. Levels of bacteria are determined by analyzing water samples to see if the water purification is sufficient or if there is a problem. Checks also reveal whether problems with the system are allowing for the introduction of hazardous organisms after the water passes through purification filters and the chlorine water treatment.
Municipal water supplies are often put through chlorine water treatment. Individual homes using wells and other water sources like springs can also treat their water with chlorine, using a pump to pass chlorine through their water as it is used. The necessity of chlorine water treatment for homes using their own wells and other sources is determined by testing the water for signs of contamination; in a closed system where water is drawn from a deep well, it may not be needed.