What does biochemical oxygen demand (BOD) indicate about water quality?

Biochemical oxygen demand (BOD) is a critical metric used to assess the organic pollution levels in water. It quantifies the amount of oxygen that microorganisms will consume while decomposing organic matter in a sample of water over a specific period, typically five days at a controlled temperature. A higher BOD value suggests a greater presence of organic matter, which can lead to oxygen depletion in aquatic environments, negatively affecting fish and other aquatic life that rely on dissolved oxygen.

In the context of evaluating water quality, understanding BOD is essential because it provides insights into the degree of organic pollution. This can be essential for determining the effectiveness of wastewater treatment processes and assessing the health and sustainability of aquatic ecosystems. Other options, such as measuring the presence of heavy metals, assessing temperature fluctuations, or determining color and turbidity, do not relate to the inherent purpose of BOD, which is exclusively focused on the biological demand for oxygen due to organic pollutants.