After which treatment step should the fluoride injection point be located?

• A. Before aeration
• B. Before filtration
• C. After the water has received complete treatment
• D. After sedimentation

Answer: (C)

The fluoride injection point should be located after the water has received complete treatment to ensure its effectiveness and safety. By administering fluoride at this stage, the treatment process maximizes the stability and homogeneity of the fluoride in the water. If fluoride were added too early in the treatment process, such as before filtration or sedimentation, it could be removed or altered by the subsequent treatment steps, thereby diminishing its intended benefits.

Injecting fluoride after complete treatment ensures that it can be effectively distributed throughout the water supply without being lost to filtration or sedimentation processes, thus achieving its public health goal of preventing dental caries in the population served by the water system. Additionally, this timing takes into account that other treatment processes, such as disinfection, should have been completed to avoid any potential interactions between fluoride and disinfectants that might compromise either component's efficacy or safety.