Biochemical oxygen demand (BOD) and chemical oxygen demand (COD) are two important indicators used to assess the degree of water pollution, but they have some differences in measurement methods, concepts, and types of pollutants reflected.
Determination method: BOD is determined by biochemical method, which mainly reflects the amount of free oxygen consumed by the oxidative decomposition of organic matter in water by aerobic microorganisms. COD is determined by chemical methods, mainly using chemical oxidants to oxidize and decompose oxidizable substances in water, and then calculate the oxygen consumption according to the amount of residual oxidants.
Types of pollutants reflected: BOD mainly reflects the amount of organic matter in the water that can be biologically oxidized, while COD can reflect all substances with reducing properties in the water, including organic and inorganic substances, such as sulfides, ferrous ions, sodium sulfite, etc.
Measurement time and water quality conditions: The measurement time of BOD is long, usually 5 days, and it is greatly affected by water quality conditions, such as water temperature, pH value, microbial species and quantity, etc. On the other hand, COD is measured in a shorter time, usually only a few hours, and is largely unrestricted by water quality conditions.
COD tester
In the actual measurement, the appropriate index should be selected according to the specific needs and conditions. If you need to quickly understand the degree of pollution of water quality and the requirements for inorganic pollutants are not high, you can choose COD. If you need a more accurate understanding of the degree of contamination of organic matter in your water and do not require a high measurement time, you can choose BOD. At the same time, it can also be combined with the two indicators for a comprehensive analysis to have a more comprehensive understanding of the pollution status of water quality.