What does Chemical Oxygen Demand (COD) measure?

Chemical Oxygen Demand (COD) is a critical parameter used to assess the amount of organic compounds in a sample of water or wastewater. It indicates how much oxygen is required to chemically oxidize the organic matter present in the water, providing a measure of the level of pollution. A higher COD value suggests a higher concentration of organic substances, which can be detrimental to water quality and can affect aquatic life if not properly treated.

While it's true that COD reflects the presence of organic materials, it's distinct from measuring just the linear amounts of specific compounds or directly indicating the biological activity within the sample (as expressed in metrics like Biochemical Oxygen Demand, BOD). Thus, the option that states COD measures all organic compounds in a sample directly aligns with its definition and application in wastewater treatment and environmental monitoring.

This understanding is crucial because it informs the treatment process and regulatory compliance associated with wastewater discharge and environmental protection.