Chemical Oxygen Demand (COD)

The organic matter is susceptible to oxidation by strong chemical oxidant. COD is used as a measure of the oxygen equivalent of the organic matter content of the sample. COD is typically used when there are industrial wastewater sources, as compare biological to chemical oxidation in the selection of treatment process and performances.

COD might be defined as the milligrams of oxygen need to chemically oxidize, by using chromic acid, the organic contaminants in 1 litre of wastewater. COD is other means of measuring the pollutional strength of a wastewater. By using this technique, most oxidizable organic compounds present in the wastewater sample are measured rather than only the more simply oxidizable ones measured using the BOD test. Commonly, COD values will be higher than those determined along with the BOD text. The purpose for this difference is which the BOD test measures only the quantity of organic material capable of being oxidized through microbial action, although the COD test represents a more fully oxidation. The COD test has a major advantage over the BOD analysis because of the short time required - a few hours as opposed to 5 days for the standard BOD test. This advantage allows more responsive operational control of the treatment procedures. Typical COD values for domestic wastewater range from 200 to 500 mg/l. Since the industrial content of the wastewater rises, the ratio of COD to BOD typically additionally increases