ADEQ Water Treatment Grade 4 Practice Test

Disinfection in drinking water treatment is about inactivating pathogens so water is safe to drink. The most common disinfectants used in treatment plants are chlorine-based compounds, chloramines, ozone, and UV light. Chlorine-based compounds provide quick disinfection and leave a protective residual in the distribution system. Chloramines are formed when ammonia is added with chlorine, giving a longer-lasting residual but somewhat slower disinfection. Ozone is a powerful oxidant that disinfects rapidly and can improve taste and odor, though it doesn’t leave a lasting residual in the pipes. UV disinfection uses light to inactivate microorganisms as water passes through a UV chamber, but it does not provide any residual disinfectant after treatment. Boiling water is a household precaution, not a routine plant disinfection method, and hydrogen peroxide alone is not a standard primary disinfectant for drinking water treatment. That combination—chlorine-based compounds, chloramines, ozone, and UV—reflects the typical approaches used in treating drinking water.