What does chemical oxygen demand (COD) testing measure?

Chemical oxygen demand (COD) testing measures the amount of oxygen required to oxidize organic and inorganic substances present in water. This test is an important indicator of water pollution, as it assesses the level of contaminants that can consume oxygen during decomposition. The COD value reflects the loading on a body of water, giving insights into how much oxygen will be needed to break down the pollutants. A higher COD indicates a greater amount of oxidizable material, which can lead to a depletion of dissolved oxygen in the water, affecting aquatic life.

The other options do not accurately describe what COD measures. The total oxygen available in the water pertains more to dissolved oxygen levels rather than the oxygen demand for oxidation. Levels of dissolved solids refer to the concentration of all dissolved materials in water, which is unrelated to the oxidation process assessed by COD. Lastly, the concentration of metals in the water is specific to metal pollutants rather than the biological and chemical oxygen consumption reflected in COD results.