What is the primary source of chlorine in water treatment facilities?

The primary source of chlorine in water treatment facilities includes several different forms, making "All of the above" the correct answer. Chlorine gas, sodium hypochlorite, and calcium hypochlorite are all widely used for disinfection in various water treatment processes.

Chlorine gas is a traditional method for disinfecting water due to its effectiveness and relatively low cost. It is often preferred in larger treatment plants because it can be more efficient for treating large volumes of water.

Sodium hypochlorite, which is commonly found in household bleach, is another important source of chlorine in water treatment. It is often used in plants due to its ease of handling and storage, particularly in smaller or decentralized systems.

Calcium hypochlorite is also utilized because it is stable and can be stored safely for longer periods. It effectively releases chlorine when dissolved in water, making it another viable option for disinfection.

By including all three sources, the answer reflects the comprehensive and versatile approaches that facilities can employ to ensure effective disinfection in water treatment.