Wastewater treatment concept analysis: COD, BOD, ammonia nitrogen, total nitrogen

Chemical oxygen demand (COD) reflects the degree of water polluted by reducing substances, these substances including organic matter, nitrite, ferrous salt, sulphur, etc., but the general inorganic reducing substances in water and wastewater, the number of relatively modest by organic pollutants is very common, therefore, COD can be used as a comprehensive indicator of the relative contents of organic matter.

Its definition is: under aerobic conditions, the amount of free oxygen consumed by aerobic microorganisms to oxidize and decompose organic matter in unit volume of water, expressed in mg/L).

Ammonia nitrogen is a nutrient in water, which can lead to water eutrophication. It is the main oxygen consuming pollutant in water, and is toxic to fish and some aquatic organisms.