Why chlorine is added to water?
Water comes from a variety of sources, such as lakes and wells, which can be contaminated with germs that may make people sick. Germs can also contaminate water as it travels through miles of piping to get to a community. To prevent contamination with germs, water companies add a disinfectant usually either chlorine or chloramine that kills disease-causing germs such as Salmonella, Campylobacter, and norovirus. Chlorine and chloramine are the major disinfectants used in public water systems.
Is chlorinated water toxic?
Even though chlorine is used to treat water and make it safe to drink, it’s important to understand that chlorine is still a chemical and can lead to some long-term health effects if you regularly drink water that contains too much chlorine. Since there is hardly any chlorine in drinking water, it’s not toxic to drink water that contains chlorine. The majority of municipalities choose to add chlorine to water because of how effective it is at killing bacteria and viruses. Swimming pool facilities commonly choose to add chlorine to their water for the same reason.
While there are other methods of disinfection, chlorine can disinfect water by breaking down the chemical bonds of the molecules that exist within viruses and bacteria. In the 1800’s, water went largely untreated until it was discovered that chlorine could be used as a disinfectant. Before this occurred, waterborne diseases like dysentery, cholera, and typhoid were common. Even though ultraviolet light is a great way to disinfect water without using chemicals, chlorine is still considered to be the most inexpensive option when used for large-scale treatment.
Despite its heavy use, chlorine doesn’t cause much harm to the environment. Chlorine can react with other types of chemicals once it has entered the water or air. When combined with inorganic materials in the water, chloride salts can be formed. When chlorine combines with organic materials, chlorinated organic chemicals will form. If animals have extended exposure to chlorine in the air, their respiratory systems, immune systems, and heart health may be adversely affected. Despite these issues, the harm caused to the environment by chlorine is low compared to other water contaminants.
Does chlorinated water cause corrosion?
Yes, it will, depending on its concentration. It will corrode steel and stainless steel due to chemical reactions between chlorine and water. Oxidation will occur and cause pipes to decay and over time will fail. Dilution with more water can assist in preventing this but it will still affect the metal in pipe to be corroded. Plastic types of pipe like PVC or CPVC will not be affected by the oxidation reaction of chlorine as is used in these applications instead of carbon and chromium-based metals.
Chlorine is strong oxidizing agent and it’s more corrosive than HCl. For example in reaction with iron metal:
2HCl + Fe → FeCl2 + H2
3Cl2 + 2Fe → 2FeCl3
chlorine oxidises iron directly to 3+ ion while HCl only to 2+ ion because hydronium ion is a weaker oxidising agent than chlorine.