Which of the following is true about COD and BOD?

COD, or Chemical Oxygen Demand, and BOD, or Biochemical Oxygen Demand, are both important parameters used to evaluate the organic content in wastewater, but they measure different aspects and provide different insights into water quality.

When stating that they are indirect measurements of the organic content in influent, it is crucial to understand that neither COD nor BOD directly quantifies specific organic compounds. Instead, these measurements estimate the amount of oxygen required to degrade organic matter. COD measures the total oxygen demand from both biodegradable and non-biodegradable compounds through a chemical process, while BOD specifically assesses the oxygen required by microorganisms to biologically decompose the organic material over a specified time frame. Therefore, while they correlate to some extent, they do not correspond in terms of what they specifically measure or the nature of the organic material involved.

This characterization helps clarify why other options do not hold. For instance, they are not direct measurements of organic content, as both require certain assumptions and approximations in their methodologies. Additionally, they do not provide the same measurements; each represents different fractions of organic material. Lastly, while COD can include measurements of toxic substances, BOD does not primarily focus on this aspect; thus, saying only COD measures toxic substances oversimplifies the