Superchlorination is typically used when ______ are excessive

• A. Heterotrophic plate counts
• B. Quercitannic acids
• C. Ammonia concentrations
• D. Fulvic acids and humic acids

Answer: (C)

Superchlorination is used to overcome chlorine demand created by ammonia and to ensure an effective free chlorine residual. When chlorine meets water containing ammonia, it first forms chloramines, which consume free chlorine and are weaker disinfectants. To restore strong disinfection, you add enough chlorine to push past the breakpoint, oxidizing the ammonia and breaking down chloramines so free chlorine remains. This is why the approach is typically applied when ammonia concentrations are high. Heterotrophic plate counts reflect microbial presence, and natural organic acids contribute to chlorine demand too, but the need to achieve a free-chlorine residual after ammonia oxidation is the situation that drives superchlorination.