Excess pink water can result from an overdose of which substance?

The correct answer is potassium permanganate. Excessive amounts of potassium permanganate in water treatment processes can lead to the formation of a pink discoloration in the water. This is a direct result of the compound’s strong coloration properties; even at low concentrations, it can impart a noticeable pink hue. When dosage levels exceed the necessary amounts for oxidation or disinfection, the residual potassium permanganate remains in the water, causing the visual effect known as "pink water."

This understanding is particularly important in managing a water treatment facility because maintaining proper chemical dosing is crucial not only for the effectiveness of treatment processes but also for ensuring the aesthetic quality of the water supplied to consumers. By controlling the amount of potassium permanganate added, operators can prevent excess discoloration and maintain water clarity.