Which parameter is commonly used as a water quality indicator to evaluate coagulant dosage?

Which parameter is commonly used as a water quality indicator to evaluate coagulant dosage?

• A. Turbidity
• B. Temperature
• C. pH
• D. Chlorine demand

Answer: (D)

Evaluating coagulant dosage hinges on turbidity after coagulation and clarification because turbidity directly shows how many suspended particles remain. When you adjust the dose, you look for the lowest turbidity achievable without wasting chemical, meaning the coagulant is effectively destabilizing and removing particles. Temperature and pH influence the process, but they don’t by themselves indicate the right dose. Chlorine demand measures what’s needed to disinfect the water, which depends on organics and other compounds, not on how well coagulation removed particles. So turbidity is the best indicator for setting coagulant dosage.

Evaluating coagulant dosage hinges on turbidity after coagulation and clarification because turbidity directly shows how many suspended particles remain. When you adjust the dose, you look for the lowest turbidity achievable without wasting chemical, meaning the coagulant is effectively destabilizing and removing particles. Temperature and pH influence the process, but they don’t by themselves indicate the right dose. Chlorine demand measures what’s needed to disinfect the water, which depends on organics and other compounds, not on how well coagulation removed particles. So turbidity is the best indicator for setting coagulant dosage.