Florida Wastewater Practice Test

In wastewater treatment, what is the purpose of using an indicator like phenolphthalein?

1. To increase reaction speed

2. To indicate endpoint of titration

3. To stabilize pH

4. To precipitate solids

The correct answer is: To indicate endpoint of titration

Phenolphthalein is commonly used in titration processes to signal the endpoint of a chemical reaction. When used in wastewater treatment, it changes color depending on the pH level of the solution, typically transitioning from colorless in acidic conditions to pink in basic conditions. This visual change allows operators to easily determine when the desired level of acidity or alkalinity has been reached during analyses involving acid-base reactions. Identifying the endpoint of titration is crucial in various testing protocols in wastewater treatment, such as measuring alkalinity, which influences the treatment process and the efficiency of waste stabilization. This capability allows for precise adjustments to treatment chemicals, thereby ensuring optimal performance and compliance with environmental regulations. Other options do not encapsulate the primary function of phenolphthalein in wastewater treatment effectively, as it is not designed to stabilize pH or precipitate solids, nor does it inherently increase reaction speed.