- Calcium hypochlorite, with the chemical formula Ca(ClO)₂, is a white or grayish-white granular solid or tablet that is widely used as a disinfecting and bleaching agent.
- It has a strong chlorine-like odor due to its release of active chlorine when dissolved in water. As a powerful oxidizing agent, calcium hypochlorite is primarily used for water treatment, particularly in the disinfection of drinking water and swimming pools, where it helps eliminate bacteria, viruses, algae, and other pathogens.
- Commercially available calcium hypochlorite typically contains around 65–70% available chlorine, making it one of the most potent solid sources of chlorine used in sanitation. It is often referred to as “chlorinated lime” or “bleaching powder,” though it should not be confused with older bleaching compounds that contained calcium chloride and lime with lower available chlorine content. When dissolved in water, calcium hypochlorite forms hypochlorous acid (HOCl), the active disinfectant species that rapidly destroys microbial cells by disrupting proteins and DNA.
- One of its major applications is in municipal and rural water treatment, where it provides a convenient and stable form of chlorine for disinfection, especially in areas lacking infrastructure for gas chlorination systems. It is also used in emergency sanitation scenarios, such as natural disasters or refugee camps, to ensure access to safe drinking water.
- In swimming pool maintenance, calcium hypochlorite is a popular choice for routine chlorination due to its high efficacy, long shelf life, and ease of use. It is commonly available in tablet, granular, or powder form and is used to maintain appropriate chlorine levels that help prevent waterborne illnesses and control algae growth.
- Outside of water treatment, calcium hypochlorite is used in agriculture, food sanitation, and industrial hygiene. It is employed to disinfect equipment, wash fruits and vegetables, sanitize dairy and food-processing facilities, and purify wastewater. Additionally, it is used as a bleaching agent in the textile and paper industries and as an oxidizer in certain chemical manufacturing processes.
- Despite its many benefits, calcium hypochlorite must be handled with caution due to its reactive and corrosive nature. It is incompatible with organic materials, acids, ammonia, and flammable substances, and can cause fires or explosions if improperly stored. It should be kept in cool, dry, well-ventilated areas, away from heat sources and moisture. Protective equipment is recommended during handling to prevent skin, eye, and respiratory irritation.
- In health and environmental contexts, calcium hypochlorite is effective in reducing microbial contamination but can produce disinfection byproducts (DBPs) such as trihalomethanes (THMs) when it reacts with natural organic matter in water. These byproducts are regulated due to potential long-term health effects, and their formation is typically managed through controlled dosing and filtration.
