When a body of wastewater contains too much biological material, the bacteria and other microorganisms in it cannot successfully decompose all the organic matter for food, growth and energy. This breaking down of the biological material requires oxygen; therefore, by measuring the amount of oxygen that is depleted from the sample as a result of such bacterial action, the balance within the aquatic environment can be measured. Chemical Oxygen Demand (COD) is a test that adds a strong chemical oxidizing agent to the wastewater sample in order to estimate the result of bacterial action. Although it is completely artificial, it is considered to yield a result that may be used as the basis on which to calculate a reasonably accurate and reproducible estimate of the oxygen-demanding properties of a wastewater. The COD’s advantages (compared to the BOD test) are that it takes under three hours for completion and is not subject to the interference from toxic materials that can affect the results of the BOD. Both of these are standard tests for estimating the health of an aquatic environment.
Source: CT Glossary
Category: Green