chemical oxygen demand (COD)

Definition

Standard method for indirect measurement of the amount of pollution (that cannot be oxidized biologically) in a sample of water. COD test procedure is based on the chemical-decomposition of organic and inorganic contaminants, dissolved or suspended in water. The result of a COD test indicates the amount of water dissolved oxygen (expressed as parts per million or milligrams per liter of water) consumed by the contaminants, during two hours of decomposition from a solution of boiling potassium dichromate. Higher the COD, higher the amount of pollution in the test sample. For the contaminants that can be oxidized biologically, biological oxygen demand (BOD) method is used.