COD (Chemical Oxygen Demand)

Chemical oxygen demand is a measure of the total quantity of oxygen required to oxidize all organic material (biologically available, inert organic matter) into carbon dioxide and water, and oxidisable inorganic matter.

Oxidation is performed using chemical oxidants (potassium dichromate, potassium permanganate). The consumption of chemicals gives an indirect indication of the content of organic matter and the corresponding quantity of oxygen required.

COD values are always greater than BOD values as this test oxidises inert organic matter as well as biologically available organic matter.