Water Treatment · Treatment Steps
What Is a Disinfectant Residual?
Disinfection controls microorganisms that may remain after other treatment steps.
Plants may use chlorine, chloramine, ultraviolet light, ozone, or another approved method. Each works differently. Chlorine and chloramine leave a residual you can test in the pipes. UV and ozone leave none, so plants that use them often add chlorine or chloramine for the distribution system. For a chlorine system, the operator needs to understand chemical dose, the amount used by the water, the contact time before the water leaves, and the residual that remains. A residual is the measured disinfectant left after some has reacted. It shows the process is working and protects water farther out in the pipes. The correct values depend on the water, plant design, and rules. Clear-looking water may still need disinfection.
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Introduction to Water Treatment Operations
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