Lime softening effect on disinfection

Lime softening effect on disinfection

• A. Decreases disinfection due to chlorine consumption
• B. Increases disinfection due to higher pH
• C. No effect on disinfection
• D. Lowers pH

Answer: (B)

Lime softening raises the water’s pH and alkalinity by adding calcium hydroxide. That higher pH environment helps disinfection in practice because it reduces the amount of substances in the water that would otherwise consume disinfectant. By removing or precipitating certain dissolved organic matter, iron, and manganese during the lime-softening process, the chlorine (or other disinfectant) used later faces less demand, leaving more disinfectant available to inactivate pathogens. In this way, the overall disinfection effect improves when lime softening increases the pH.

Lime softening raises the water’s pH and alkalinity by adding calcium hydroxide. That higher pH environment helps disinfection in practice because it reduces the amount of substances in the water that would otherwise consume disinfectant. By removing or precipitating certain dissolved organic matter, iron, and manganese during the lime-softening process, the chlorine (or other disinfectant) used later faces less demand, leaving more disinfectant available to inactivate pathogens. In this way, the overall disinfection effect improves when lime softening increases the pH.