What type of chemical is primarily used for disinfection in water treatment?

Chlorine is primarily used for disinfection in water treatment due to its effectiveness in killing bacteria, viruses, and other pathogens present in water. It is a powerful oxidizing agent and has a long-lasting residual effect, which means it continues to disinfect even after initial treatment. This residual effect is crucial for maintaining water quality as it helps prevent the regrowth of harmful microorganisms as the water travels through the distribution system.

Chlorine is preferred because it can be easily dosed into water supplies and is relatively inexpensive compared to other disinfectants. Additionally, the overall process of chlorination forms various disinfection by-products, which are monitored to ensure they remain within safety standards. This robust capability aligns with regulatory requirements for potable water treatment.

In contrast, fluoride is primarily used for dental health and not for disinfection, sodium carbonate is typically used for pH adjustment, and alum serves as a coagulant to help in the removal of suspended solids and turbidity. These alternatives do not serve the primary role of pathogen inactivation that chlorine provides, highlighting the specific function and importance of chlorine in water treatment processes.