Chemical oxygen demand (COD) is a chemical method to measure the amount of reducing substances in water samples that need to be oxidized. Under certain conditions, the amount of oxidant consumed by oxidizing reducing substances in 1 liter of water sample is taken as an index, which is converted into the milligrams of oxygen needed after each liter of water sample is completely oxidized, expressed in mg/L.. It reflects the degree of pollution by reducing substances in water. This index is also used as a comprehensive index of the relative content of organic matter.
Fundamental principles
When the mixture of water sample, potassium dichromate digestion solution, silver sulfate solution (silver sulfate can effectively oxidize straight chain fatty compounds) and concentrated sulfuric acid is heated to 170 ℃, the color of organic matter in the solution will change after being oxidized by dichromate ions. The analyzer detects this color change and converts this change into COD value for output. The amount of dichromate ions consumed is equivalent to the amount of oxidizable organic matter.
Application field
On-line monitoring of industrial pollution source wastewater
On-line monitoring of industrial process water
On-line monitoring of import and export water quality of municipal sewage treatment plant
On-line monitoring of river, lake, reservoir and groundwater quality