What is the purpose of ORP measurements in wastewater treatment?

• A. To measure pH
• B. To measure dissolved oxygen
• C. To measure oxidation-reduction potential
• D. To measure turbidity

Answer: (C)

Oxidation-reduction potential (ORP) measures the tendency of the water to gain or lose electrons, i.e., its redox state. In wastewater treatment, knowing the redox state is crucial because many treatment steps depend on whether conditions are oxidizing or reducing. ORP provides a single signal that reflects the combined effect of oxidants and reductants present, helping operators judge and control processes such as aerobic digestion (oxidizing conditions) and denitrification (reducing conditions), and to assess disinfection effectiveness (where a higher oxidizing condition is typically desired). It is not a direct measure of pH, dissolved oxygen, or turbidity, which are different parameters with their own sensors. So, the purpose of ORP measurements is to monitor the redox state of the wastewater and use that information to optimize treatment steps.