When applying supplemental disinfection, which method is least likely to produce disinfection byproducts?

Using ultraviolet light as a method of supplemental disinfection is least likely to produce disinfection byproducts. This is primarily because ultraviolet light treatment works by inactivating microorganisms through the direct action of light, without introducing any chemicals into the water. As a result, there are no chemical reactions that could lead to the formation of byproducts, which can often occur with other disinfection methods that utilize chemical agents.

In contrast, chlorination introduces chlorine into the water, which can react with organic and inorganic materials to form various disinfection byproducts, such as trihalomethanes and haloacetic acids. Similarly, chloramination, which uses both chlorine and ammonia, can also lead to the formation of byproducts, albeit typically at lower levels than chlorination. Ozonation, though highly effective at disinfection, can create ozone byproducts when reacting with certain substances in the water.

Focusing on how UV light functions highlights its effectiveness in disinfection while minimizing the risk of harmful byproducts, making it a preferred option in situations where maintaining water quality and safety is a priority.